U.S. patent application number 17/337981 was filed with the patent office on 2021-11-04 for thermal energy delivery systems and methods for heating a vertebral body.
This patent application is currently assigned to THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. The applicant listed for this patent is THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. Invention is credited to David S. Bradford, Chris J. Diederich, Jeffrey C. Lotz, Will Nau.
Application Number | 20210339054 17/337981 |
Document ID | / |
Family ID | 1000005708961 |
Filed Date | 2021-11-04 |
United States Patent
Application |
20210339054 |
Kind Code |
A1 |
Diederich; Chris J. ; et
al. |
November 4, 2021 |
THERMAL ENERGY DELIVERY SYSTEMS AND METHODS FOR HEATING A VERTEBRAL
BODY
Abstract
An ultrasound therapy system and method is provided that
provides directional, focused ultrasound to localized regions of
tissue within body joints, such as spinal joints. An ultrasound
emitter or transducer is delivered to a location within the body
associated with the joint and heats the target region of tissue
associated with the joint from the location. Such locations for
ultrasound transducer placement may include for example in or
around the intervertebral discs, or the bony structures such as
vertebral bodies or posterior vertebral elements such as facet
joints. Various modes of operation provide for selective,
controlled heating at different temperature ranges to provide
different intended results in the target tissue, which ranges are
significantly affected by pre-stressed tissues such as in-vivo
intervertebral discs. In particular, treatments above 70 degrees
C., and in particular 75 degrees C., are used for structural
remodeling, whereas lower temperatures achieve other responses
without appreciable remodeling.
Inventors: |
Diederich; Chris J.;
(Novato, CA) ; Lotz; Jeffrey C.; (San Mateo,
CA) ; Nau; Will; (San Francisco, CA) ;
Bradford; David S.; (Sausalito, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE REGENTS OF THE UNIVERSITY OF CALIFORNIA |
Oakland |
CA |
US |
|
|
Assignee: |
THE REGENTS OF THE UNIVERSITY OF
CALIFORNIA
Oakland
CA
|
Family ID: |
1000005708961 |
Appl. No.: |
17/337981 |
Filed: |
June 3, 2021 |
Related U.S. Patent Documents
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Application
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16161025 |
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11052267 |
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17337981 |
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60349207 |
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60351827 |
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60410603 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2090/374 20160201;
A61B 2017/00261 20130101; A61N 2007/0056 20130101; A61N 2007/0021
20130101; A61B 2017/00092 20130101; A61N 2007/003 20130101; A61B
2017/00101 20130101; A61B 18/04 20130101; A61N 2007/0078 20130101;
A61N 7/022 20130101; A61N 7/02 20130101 |
International
Class: |
A61N 7/02 20060101
A61N007/02 |
Claims
1. An ultrasound energy delivery system for treating a region of
tissue associated with a skeletal joint, comprising: an ultrasound
treatment assembly with an ultrasound transducer; a skeletal joint
delivery assembly that is adapted to deliver the ultrasound
treatment assembly into the body with the ultrasound transducer
positioned at a location within the body associated with the
skeletal joint; and wherein the ultrasound treatment assembly is
adapted to deliver a therapeutic level of ultrasound energy from
the location and into the region of tissue.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/161,025 filed on Oct. 15, 2018,
incorporated herein by reference in its entirety, which is a
continuation of U.S. patent application Ser. No. 14/540,017 filed
on Nov. 12, 2014, now U.S. Pat. No. 10,272,271, incorporated herein
by reference in its entirety, which is a continuation of U.S.
patent application Ser. No. 12/781,689 filed on May 17, 2010, now
U.S. Pat. No. 8,915,949, incorporated herein by reference in its
entirety, which is a continuation of U.S. patent application Ser.
No. 11/364,357 filed on Feb. 27, 2006, now abandoned, incorporated
herein by reference in its entirety, which is a division of U.S.
patent application Ser. No. 10/347,164 filed on Jan. 15, 2003, now
U.S. Pat. No. 7,211,055, incorporated herein by reference in its
entirety, which claims the benefit of U.S. provisional patent
application Ser. No. 60/349,207 filed on Jan. 15, 2002,
incorporated herein by reference in its entirety, and the benefit
of U.S. provisional patent application Ser. No. 60/351,827 filed on
Jan. 23, 2002, incorporated herein by reference in its entirety,
and the benefit of U.S. provisional patent application Ser. No.
60/410,603 filed on Sep. 12, 2002, incorporated herein by reference
in its entirety, and the benefit of U.S. provisional patent
application Ser. No. 60/411,401 filed on Sep. 16, 2002,
incorporated herein by reference in its entirety. Priority is
claimed to each of the foregoing patents and patent
applications.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0003] The present invention is a system and method for delivering
therapeutic levels of energy to tissue in a living body. More
specifically, it is a system and method for delivering therapeutic
levels of ultrasound energy invasively within the body in order to
treat disorders associated with the spine and other joints. Still
more specifically, it is a system and method for delivering
ultrasound energy to intervertebral discs in order to treat
disorders associated therewith such as chronic lower back pain.
2. Description of the Background Art
[0004] For many years, much research and commercial development has
been directed toward delivering energy to tissue in order to
achieve various desired therapeutic results. Examples of energy
modalities previously described for tissue treatment include:
electrical current (both DC and AC, e.g. radiofrequency or "RF"
current), plasma ion energy, sonic energy (in particular
ultrasound), light energy (e.g. laser, infrared or "IR", or
ultraviolet or "UV"), microwave induction, and thermal energy (e.g.
convection or conduction). Other modalities for treating tissue
include without limitation: cryotherapy (cooling tissue to desired
levels to affect structure of function), and chemical therapy
(delivering chemicals to the tissue to affect the tissue structure
of function). Each of these energy delivery and other treatment
modalities has been extensively studied and characterized as
providing unique benefits, as well as unique issues and concerns,
with respect to tissue therapy. Accordingly, many specific energy
delivery methods and systems have been disclosed to provide unique
benefits for particular intended therapeutic applications.
[0005] Various specific tissue responses to energy delivery have
also been observed and reported during the course of significant
study and characterization. In one regard, tissues or their
function may be damaged by energy delivery such as thermal therapy.
Examples of previously disclosed, differentiated effects of thermal
tissue therapy generally characterized to damage tissue include,
without limitation: ablation (which has been defined as either
molecular dissociation or by achieving cellular necrosis),
coagulation, degranulation, and desiccation. Alternatively, energy
delivery in certain particular forms has also been characterized as
promoting reproductive stimulation in certain tissues. Certain
desired results have been disclosed with respect to intending
controlled tissue damage with tissue thermal therapy; other desired
results have been disclosed with respect to promoting tissue
reproduction with tissue thermal therapy. In any event, because of
the pronounced effects observed from tissue energy delivery, it is
often desired to control and accurately select the localization of
tissue/energy interaction in order to treat only the intended
tissue, else normal surrounding tissue is effected with harmful
results.
[0006] Accordingly, the different energy delivery modalities have
been specifically characterized as providing particular benefits
and problems versus other modalities with respect to various
specific tissues and related medical conditions. Examples of
specific medical conditions and related tissue that have been
studied and characterized for tissue energy delivery include:
tumors such as cancer (e.g. liver, prostate, etc.); vascular
aneurysms, malformations, occlusions, and shunts; cardiac
arrhythmias; eye disorders; epidermal scarring; wrinkling; and
musculo-skeletal injury repair. The nature of the condition to be
treated, as well as the anatomy of the area, can have significant
impact on the desired result of energy delivery, which directly
differentiates between the appropriateness or inappropriateness of
each of the different energy delivery modalities for such
application (as well as the corresponding particular operating
parameters, systems, and methods for delivering such energy).
[0007] Depending upon the particular energy modality, various
different parameters may be altered to affect the thermal effect in
particular tissues, including which type of effect is achieved
(e.g. ablation, coagulation, desiccation, etc.), as well as depth
or degree of the effect in surrounding tissues. For the purpose of
a general understanding, however, known tissue responses to thermal
therapies, e.g. effect of changing temperatures to particular
levels, have been previously characterized for certain tissues in
prior disclosures which are summarized as follows.
[0008] As described above, temperature elevation of biological
tissues is currently used for outright tissue destruction or to
modify tissues to enhance other therapies. Low temperature
elevations (41-45.degree. C.) of relatively short duration
(<30-60 min) may damage cells but generally only to such extent
to be repairable and considered non-lethal. In this range, it is
believed that heat mediated physiological effects include heat
induced acceleration of metabolism or cellular activity, thermal
inactivation of enzymes, rupture of cell membranes, and delayed
onset of increasing blood flow and vessel permeability. For
temperature exposures in excess of 45.degree. C. and/or longer
durations, it is believed that cellular repair mechanisms no longer
function due to denaturation of key proteins or can't keep up with
the accumulating damage. Complete cell death and tissue necrosis
have been observed to be fully expressed in approximately 3-5 days.
Temperature exposures in the 42-45.degree. C. regimen are commonly
used for example as an adjuvant to radiation cancer therapy and
chemotherapy, and have been considered for enhancing gene therapy
and immunotherapy as well. Higher temperature elevations
(50+.degree. C.) have been investigated for inducing desirable
physical changes in tissue, ranging from applications such as
controlled thermal coagulation for "tightening" ligaments and joint
capsules, tissue reshaping, and selective tissue thermal
coagulation for destroying cancerous and benign tumors. High
temperature exposures (50+.degree. C.) are generally believed to
produce rather lethal and immediate irreversible denaturation and
conformational changes in cellular and tissue structural proteins,
thereby thermally coagulating the tissue.
[0009] In general, heat-induced cell damage or tissue structural
changes described above are believed to be attributed to thermal
denaturation and aggregation of key protein structures. The
accumulation of this thermal damage can be modeled using the
Arrhenius rate process equation, which establishes a relationship
between rate of thermal damage and the duration and temperature of
exposure:
1 .tau. = A e - .DELTA. .times. .times. E / RT , ( 1 )
##EQU00001##
where .DELTA.E is activation energy (J mol.sup.-1), is the
universal gas constant (8.32 J mol.sup.-1K.sup.-1), A is the rate
constant (s.sup.-1), T is temperature in Kelvin, and 1/.tau. is
rate of thermal damage (s.sup.-1). Using this expression (Eqn. 1),
a relationship can be derived to determine an exposure time
(.tau..sub.2) and/or temperature elevation (T.sub.2) required to
produce an equivalent observed biological effect associated with a
specified temperature (T.sub.1) and time exposure (.tau..sub.1).
This is the basis of the thermal iso-effect equation as shown
below, which is non-linear with respect to temperature exposure and
linear with respect to exposure time:
.tau..sub.2=.tau..sub.1e.sup.(.DELTA.E/RT.sup.1.sup.T.sup.2.sup.)(T.sup.-
1.sup.-T.sup.2.sup.)=.tau..sub.1K.sup.(T.sup.1.sup.-T.sup.2.sup.),
(2)
where the parameter K is approximated as constant for typical
therapeutic temperature elevations (10-30.degree. C.). Furthermore,
extensive in vitro and in vivo studies have demonstrated that
.DELTA.E for thermal damage is approximately constant at 140 J
mol.sup.-1 for temperatures greater than 43.degree. C. Thus, the
relationship between time and temperature for a given biological
effect depends upon activation energy only. Thus, as determined
from the hyperthermia biology literature, K.apprxeq.2 for
T.gtoreq.43.degree. C. and K.apprxeq.4-6 for T<43.degree. C. The
different values split at approximately 43.degree. C. in order to
model the biphasic behavior in the rate response, with faster
damage accumulation after a break around 43.degree. C. These values
hold for lethal cellular damage, but not coagulation of structural
proteins (collagen). Traditionally this iso-effect dose has been
used to characterize hyperthermia cancer treatments with a target
temperature elevation of 42.5-45.degree. C., and has led to
43.degree. C. becoming the historical reference dose temperature.
This forms the basis of the thermal iso-effect dose (TID) equation,
which as shown below can be used to calculate thermal dose of a
varying temperature exposure over time as an equivalent exposure
duration at 43.degree. C. (or other reference temperature).
Temperature time history is equated to a thermal dose at a known
temperature reference.
E .times. M 4 .times. 3 = .intg. 0 t f .times. K ( T - 4 .times. 3
) .times. d .times. t = t = 0 t final .times. .DELTA. .times. t
.times. K ( T - 4 .times. 3 ) , ( 3 ) ##EQU00002##
where dt is a time step (min) and EM.sub.43 is thermal dose
expressed in equivalent minutes at 43.degree. C.
[0010] Various previously published disclosures have verified the
Arrhenius model and the iso-effect relationship of different
temperature-time exposures for generating trans-epidermal thermal
necrosis in skin. Applying the TID analysis, a threshold of
approximately 320 EM.sub.43 (wherein "EM" represents "equivalent
minutes" at the given temperature shown in subscript) as found for
temperatures between 44-60.degree. C. Thermal dosages between
10-100 EM.sub.43 have been shown to correlate with improved
response to hyperthermia and radiation therapy. For a conservative
approach 250 EM.sub.43.degree. C. is a threshold dose for complete
thermal necrosis, where reported values range from 25-240
EM43.degree. C. for brain and muscle tissue, respectively.
[0011] In addition, thermal coagulation or coagulation necrosis
will occur in tissues exposed to temperatures greater than
approximately 55.degree. C. for a duration of minutes in collagen
in particular. Thermal coagulation of soft tissues requires
temperatures in excess of 50.degree. C. Numerous investigators have
validated the "TID" (or "temperature iso-dose") concept for
predicting lesions using 240-340 EM 43.degree. C. as a threshold
dose and critical temperatures of 53-54.degree. C. for coagulating
muscle.
Therapeutic Energy Delivery for Spinal Disorders
[0012] Spinal disorders have been the topic of significant study
and commercial development for therapeutic energy delivery. In
particular, various specific conditions that have been studied with
respect to particular modes of therapeutic energy delivery.
[0013] Of particular interest has been chronic lower back pain.
Chronic low back pain is a significant health and economic problem
in the United States, being the most costly form of disability in
the industrial setting. For a substantial number of these patients
the intervertebral disc is considered the principal pain generator.
Traditionally, patients who fail conservative therapy have few
treatment options beside discectomy or fusion, either of which can
result in significant morbidity and variable outcomes. Recent
efforts have been directed toward investigating thermal therapy for
providing a healing effect on collagenous tissues, and therefore
this modality has been incorporated into several minimally invasive
back pain treatments.
[0014] Early orthopedic use of high temperature heat therapy was to
manage shoulder instability. In this application, the shoulder
capsule is treated with laser or radio-frequency (RF) thermal
energy to temperatures typically in the range of 70 to 80.degree.
C. This treatment has been disclosed to stabilize the joint by
inducing tissue contraction. Such treatment also has been disclosed
to result in an acute decrease in stiffness (e.g. as much as 50%)
that may be recovered due to biologic remodeling. However, the
long-term benefits of this treatment have been questioned since the
collagenous tissue may re-lengthen over time.
[0015] The contraction associated with thermal therapy, which can
reach as high as 50% along the fiber direction in the shoulder
capsule, has been correlated with thermal denaturation. Thermal
denaturation is an endothermic process in which the collagen triple
helix unwinds after a critical activation energy is reached.
Differential scanning calorimetry (DSC) is a technique to measure
both the denaturation temperature (T.sub.m--the peak temperature
corresponding to this critical activation energy) and the total
enthalpy of denaturation (.DELTA.H--the total energy required to
fully denature the collagen). This technique can be used to
correlate thermal exposure with the resulting degree of
denaturation for a specific collagenous tissue, and thus to guide
the development of an optimal thermal dose.
[0016] Intradiscal electrothermal therapy (IDET) has been recently
introduced as a minimally invasive, non-operative therapy in which
a temperature elevation is applied in order to treat discogenic low
back pain. In this procedure, a catheter containing a 5 cm long
resistive-wire heating coil is introduced percutaneously into the
disc under fluoroscopic guidance. The internal temperature of the
device is then raised from 65.degree. C. to 90.degree. C. over a
course of 16 minutes. This procedure is thought to produce
temperatures sufficient to contract annular collagen and ablate
annular nociceptors. A controlled, 12 month trial of IDET on a
relatively small patient population (36 individuals) demonstrated
some relief of back pain in 60% of patients and total relief in
23%. A two-year follow-up study of 58 patients found clinically
significant improvement in pain, physical function, and quality of
life. While these results have been considered by some to be
promising, prospective placebo-controlled trials are lacking, and
the therapeutic mechanisms of thermal therapy are unknown. Proposed
therapeutic mechanisms of such technique have included: 1) collagen
denaturation, causing annular stiffening, and tissue remodeling; 2)
annular de-innervation; and 3) ablation of cytokine-producing
cells. Due to mechanistic uncertainty, treatment optimization and
patient selection are generally empirically based.
[0017] The effect of heat on collagen denaturation and
biomechanical properties has been investigated in various tissues:
knee and shoulder capsule, tendon, and chordae tendineae. In
general, at least one prior disclosure reports that significant
denaturation and shrinkage occurred in tissue treated at 65.degree.
C. and above for 1-5 minutes. However, given that the annular
architecture of intervertebral discs is quite different from these
other tissues it is has not been previously made clear that prior
results can be directly extrapolated to the intervertebral
disc.
[0018] Further more detailed background information related to
various aspects of thermal tissue therapy and/or chronic back pain
is variously disclosed in the following publications: Amonoo-Kuofi,
H. S., 1991, "Morphometric changes in the heights and
anteroposterior diameters of the lumbar intervertebral discs with
age." J Anat 159-68; Arnoczky, S. P. and Aksan, A., 2001, "Thermal
modification of connective tissues: basic science considerations
and clinical implications." Instr Course Lect 3-11; Chen, S. S.,
Wright, N. T. and Humphrey, J. D., 1997, "Heat-induced changes in
the mechanics of a collagenous tissue: isothermal free shrinkage."
J Biomech Eng 4, 372-8; Chen, S. S., Wright, N. T. and Humphrey, J.
D., 1998, "Heat-induced changes in the mechanics of a collagenous
tissue: isothermal, isotonic shrinkage." J Biomech Eng 3, 382-8;
Dewey, W. C., 1994, "Arrhenius relationships from the molecule and
cell to the clinic." Int J Hyperthermia 4, 457-83; Flandin, F.,
Buffevant, C. and Herbage, D., 1984, "A differential scanning
calorimetry analysis of the age-related changes in the thermal
stability of rat skin collagen." Biochim Biophys Acta 2, 205-11;
Gerber, A. and Warner, J. J., 2002, "Thermal capsulorrhaphy to
treat shoulder instability." Clin Orthop 400, 105-16; Hall, B. K.,
1986, "The role of movement and tissue interactions in the
development and growth of bone and secondary cartilage in the
clavicle of the embryonic chick." J Embryol Exp Morphol 133-52;
Hayashi, K. and Markel, M. D., 2001, "Thermal capsulorrhaphy
treatment of shoulder instability: basic science." Clin Orthop 390,
59-72; Hayashi, K., et al., 2000, "The mechanism of joint capsule
thermal modification in an in-vitro sheep model." Clin Orthop 370,
236-49; Hayashi, K., et al., 1997, "The effect of thermal heating
on the length and histologic properties of the glenohumeral joint
capsule." Am J Sports Med 1, 107-12; Heary, R. F., 2001,
"Intradiscal electrothermal annuloplasty: the IDET procedure." J
Spinal Disord 4, 353-60; Hecht, P., et al., 1999, "Monopolar
radiofrequency energy effects on joint capsular tissue: potential
treatment for joint instability. An in vivo mechanical,
morphological, and biochemical study using an ovine model." Am J
Sports Med 6, 761-71; Karasek, M. and Bogduk, N., 2000,
"Twelve-month follow-up of a controlled trial of intradiscal
thermal anuloplasty for back pain due to internal disc disruption."
Spine 20, 2601-7; Kronick, P., et al., 1988, "The locations of
collagens with different thermal stabilities in fibrils of bovine
reticular dermis." Connect Tissue Res 2, 123-34; Le Lous, M., et
al. 1982. "Influence of collagen denaturation on the
chemorheological properties of skin, assessed by differential
scanning calorimetry and hydrothermal isometric tension
measurement." Biochim Biophys Acta 2, 295-300; Lopez, M. J., et
al., 2000, "Effects of monopolar radiofrequency energy on ovine
joint capsular mechanical properties." Clin Orthop 374, 286-97;
Miles, C. A. and Ghelashvili, M. 1999, "Polymer-in-a-box mechanism
for the thermal stabilization of collagen molecules in fibers."
Biophys J 6, 3243-52; Naseef, G. S., et al., 1997, "The thermal
properties of bovine joint capsule. The basic science of laser- and
radiofrequency-induced capsular shrinkage." Am J Sports Med 5,
670-4; Nieminen, M. T., et al., 2000, "Quantitative MR microscopy
of enzymatically degraded articular cartilage." Magn Reson Med 5,
676-81; (Nrc/Im), N. R. C. A. I. O. M. (2001). "Musculoskeletal
Disorders and the workplace: low back and upper extremities."
Washington D.C., National Academy Press; Saal, J. A. and Saal, J.
S., 2002, "Intradiscal electrothermal treatment for chronic
discogenic low back pain: prospective outcome study with a minimum
2-year follow-up." Spine 9, 966-73; discussion 973-4; Saal, J. S.
and Saal, J. A., 2000, "Management of chronic discogenic low back
pain with a thermal intradiscal catheter. A preliminary report."
Spine 3, 382-8; Schachar, R. A., 1991, "Radial thermokeratoplasty.
Int Ophthalmol" Clin 1, 47-57; Schaefer, S. L., et al., 1997,
"Tissue shrinkage with the holmium:yttrium aluminum garnet laser. A
postoperative assessment of tissue length, stiffness, and
structure." Am J Sports Med 6, 841-8; Schwarzer, A. C., et al.,
1995, "The prevalence and clinical features of internal disc
disruption in patients with chronic low back pain." Spine 17,
1878-83; Urban, J. P. and Mcmullin, J. F., 1985, "Swelling pressure
of the intervertebral disc: influence of proteoglycan and collagen
contents." Biorheology 2, 145-57; Vangsness, C. T., Jr., et al.,
1997, "Collagen shortening. An experimental approach with heat."
Clin Orthop 337, 267-71; Vujaskovic, Z., et al., 1994, "Effects of
intraoperative hyperthermia on peripheral nerves: neurological and
electrophysiological studies." Int J Hyperthermia 1, 41-9; Wallace,
A. L., et al., 2000, "The scientific basis of thermal capsular
shrinkage." J Shoulder Elbow Surg 4, 354-60; and Wallace, A. L., et
al., 2002, "Creep behavior of a rabbit model of ligament laxity
after electrothermal shrinkage in vivo. Am J Sports Med 1, 98-102.
The disclosures of these references are herein incorporated in
their entirety by reference thereto.
[0019] Chronic lower back pain (e.g. discogenic lumbar pain) and
related motor nerve deficit is typically due to damaged or
herniated vertebral discs which either directly impinge on
surrounding nerves or cause irritating inflammation. Traditional
treatment options include surgery, anti-inflammatory drugs,
physical therapy, etc., with surgery typically the last option. Due
to difficulty of surgical procedure, complications and time of
recovery, alternative procedures have been investigated. Recently,
intradiscal thermal therapy has been introduced as a
minimally-invasive alternative in the treatment of various spinal
disorders such as chronic low back pain and otherwise disorders
related to intervertebral disc abnormalities.
[0020] In particular, several different systems and methods have
been disclosed for treating various abnormal conditions associated
with intervertebral discs specifically by delivering electrical
current in the RF range during invasive treatment procedures in and
around the disc within the body. Other previously disclosed
examples intended to invasively deliver therapeutic levels of
energy in order to treat various spinal disorders include delivery
of plasma ion energy (e.g. Coblation.RTM. from Arthrocare, Inc.),
laser light energy, or thermal energy from conductive heating
elements (e.g. SpineCATH IDEC procedure, commercially available
from Oratec Interventions). At least one other prior disclosure is
intended to deliver heated thermoplastic material to allow it to
flow into and then set upon cooling within the nucleus of an
intervertebral disc in order to replace the nucleus pulposus.
[0021] Further more detailed examples of energy delivery systems
and methods such as of the types just described, that are intended
to provide invasive therapy to treat various conditions associated
with intervertebral disc disorders are variously disclosed in the
following issued U.S. Pat. No. 4,959,063 to Kojima; U.S. Pat. No.
6,264,650 to Hovda et al.; U.S. Pat. No. 6,264,659 to Ross et al.
Examples are also disclosed in the following published U.S. Patent
application: US 2001/0029370 to Hodva et al. Other examples are
disclosed in the following published international patent
applications: WO 00/49978 to Guagliano et al.; WO 00/71043 to Hovda
et al.; WO 01/26570 to Alleyne et al. Additional disclosure is
provided in the following published reference: Diederich C J, Nau W
H, Kleinstueck F, Lotz J, Bradford D (2001) "IDTT Therapy in
Cadaveric Lumbar Spine: Temperature and thermal dose distributions,
Thermal Treatment of Tissue: Energy Delivery and Assessment,"
Thomas P. Ryan, Editor, Proceedings of SPIE Vol. 4247:104-108. The
disclosures of all these references provided in this paragraph are
herein incorporated in their entirety by reference thereto.
Ultrasound Energy Delivery Systems and Methods
[0022] Ultrasound energy delivery and the effects of such energy on
various different tissue structures has been the topic of
significant recent study. The particular benefits of ultrasound
delivery have been substantially well characterized, in particular
with respect to different types of tissues as well as different
ultrasound energy deposition modes. Many different medical device
systems and methods have been disclosed for delivering therapeutic
levels of ultrasound to tissues to treat wide varieties of
disorders, including for example arterial blockages, cardiac
arrhythmias, and cancerous tumors. Such disclosures generally
intend to "ablate" targeted tissues in order to achieve a desired
result associated with such particular conditions, wherein the
desired response in the particular tissues, and the ultrasound
delivery systems and methods of operation necessary for the
corresponding energy deposition modalities, may vary substantially
between specific such "ultrasound ablation" systems and
methods.
[0023] Further more detailed examples of ultrasound delivery
systems and methods such as of the type just described are
disclosed in the following issued U.S. patents which are
incorporated herein by reference: U.S. Pat. No. 5,295,484 to Marcus
et al.; U.S. Pat. No. 5,620,479 to Diederich; U.S. Pat. No.
5,630,837 to Crowley; U.S. Pat. No. 5,733,280 to Sherman et al.;
U.S. Pat. No. 6,012,457 to Lesh; U.S. Pat. No. 6,024,740 to Lesh et
al.; U.S. Pat. No. 6,117,101 to Diederich et al.; U.S. Pat. No.
6,164,283 to Lesh; U.S. Pat. No. 6,245,064 to Lesh et al.; U.S.
Pat. No. 6,254,599 to Lesh et al.; and U.S. Pat. No. 6,305,378 to
Lesh et al. Other examples are disclosed in the following published
foreign patent applications which are incorporated herein by
reference: WO 00/56237 to Maguire et al.; WO 00/67648 to Maguire et
al.; WO 00/67656 to Maguire et al.; WO 99/44519 to Langberg et
al.
[0024] In addition, ultrasound enhanced drug delivery into tissues,
e.g. to increase dispersion, permeability, or cellular uptake of
therapeutic compounds such as drugs, has been well characterized
and disclosed in many different specific forms.
[0025] Further more detailed examples of ultrasound energy delivery
systems and methods such as those just described are disclosed in
the following U.S. Patent References: U.S. Pat. No. 5,725,494 to
Brisken; U.S. Pat. No. 5,728,062 to Brisken; U.S. Pat. No.
5,735,811 to Brisken; U.S. Pat. No. 5,846,218 to Brisken et al.;
U.S. Pat. No. 5,931,805 to Brisken; U.S. Pat. No. 5,997,497 to Nita
et al.; U.S. Pat. No. 6,210,393 to Brisken; U.S. Pat. No. 6,221,038
to Brisken; U.S. Pat. No. 6,228,046 to Brisken; U.S. Pat. No.
6,287,272 to Brisken et al.; and U.S. Pat. No. 6,296,619 to Brisken
et al. The disclosures of these references are herein incorporated
in their entirety by reference thereto.
[0026] Additional previously disclosed examples for ultrasound
energy delivery systems and methods are intended to treat disorders
associated with the spine in general, and in some regards of the
intervertebral disc in particular. However, these disclosed systems
are generally adapted to treat such disorders chronically from
outside of the body, such as for example via transducers coupled to
a brace worn externally by a patient. Therefore locally densified
US energy is not achieved selectively within the tissues associated
with such disorders invasively within the body. At least one
further disclosure, however, proposes delivering focused ultrasound
energy from outside the body for the intended purpose of treating
intervertebral disc disorders, in particular with respect to
degenerating the nucleus pulposus to reduce the pressure within the
disc and thus onto the adjacent spinal cord. However, the ability
to actually achieve such targeted energy delivery at highly
localized tissue regions associated with such discs, and to
accurately control tissue temperature to achieve desired results,
without substantially affecting surrounding tissues has not been
yet confirmed or taught.
[0027] Further more detailed examples of such systems and methods
intended to treat spinal disorders with ultrasound energy from
outside of the body are variously disclosed in the following issued
U.S. Pat. No. 5,762,616 to Talish; U.S. Pat. No. 6,254,553 to
Lidgren et al. Other examples are disclosed in the following
published international patent applications: WO 97/33649 to Talish;
WO 99/19025 to Urgovich et al.; and WO 99/48621 to Cornejo et al.
The disclosures of these references are herein incorporated in
their entirety by reference thereto.
[0028] There is still a need for improved systems and methods for
locally delivering therapeutic amounts of ultrasound energy
invasively within the body in order to treat disorders associated
with the spine and other joints.
[0029] There is in particular still a need for a system and method
adapted to locally deliver ultrasound to a highly localized region
of tissue, such as only a portion of a disc.
BRIEF SUMMARY OF THE INVENTION
[0030] An object of the invention is to deliver therapeutic levels
of ultrasound energy to intervertebral discs in order to treat
disorders associated therewith.
[0031] Another object of the invention is to provide a kit of
energy delivery devices with varied shapes along the energy
delivery portion thereof in order to specifically treat different
regions of intervertebral discs having varied geometries from
within the nucleus.
[0032] Another object of the invention is to deliver therapeutic
levels of energy sufficient to cause necrosis of particular
cellular structures associated with an intervertebral disc without
substantially remodeling or affecting the structure integrity of
the annulus fibrosus of the disc.
[0033] Another object of the invention is to provide thermal
therapy to a region of tissue associated with a joint in the body
without substantially remodeling structural support tissues
associated with the joint.
[0034] Another object of the invention is to treat inflammation and
pain associated with disorders of the spine in general and
intervertebral discs in particular.
[0035] Another object of the invention is to denervate or necrose
nociceptive fibers or cells in certain regions of tissue associated
with an intervertebral disc.
[0036] Another object of the invention is to reduce inflammation
associated with damaged intervertebral discs.
[0037] Another object of the invention is to repair damaged regions
of intervertebral discs.
[0038] Another object of the invention is to achieve cellular
necrosis of certain particular tissues associated with an
intervertebral disc disorder without substantially altering the
structure of the annulus fibrosus of the respective disc.
[0039] Another object of the invention is to remodel cartilaginous
tissue associated with spinal joints, and in particular
intervertebral discs.
[0040] Another object of the invention is to provide sufficient
thermal therapy to a region of stressed tissue to cause a
remodeling of the tissue.
[0041] Another object of the invention is to provide sufficient
thermal therapy to a region of an intact mammalian intervertebral
disc to cause a remodeling of at least one support structure.
[0042] Another object of the invention is to provide a thermal
therapy device that can substantially heat deep regions of tissue
from the site of therapy, such as with respect to spinal joints at
least about 4 mm, 7 mm, or even 10 mm from the site of therapy.
[0043] Another object of the invention is to provide therapeutic
levels of thermal therapy to tissue within relatively short periods
of time.
[0044] Another object of the invention is to direct therapeutic
energy into targeted tissues from remote locations within the body,
such as in or around joints, without substantially harming closely
adjacent tissues, such as nerves, vessels, or other tissues not
intended to be treated.
[0045] Another object of the invention is to focus energy into
targeted regions of tissue within the body.
[0046] Another object of the invention is to enhance cellular
functions in certain tissue structures so as to provide a
therapeutic effect.
[0047] Another object of the invention is to enhance drug delivery
into remotely located body tissues, such as within or around joints
such as spinal joints.
[0048] Another object of the invention is to treat back pain.
[0049] Another object of the invention is to treat arthritis.
[0050] Another object of the invention is to locally enhance the
delivery, permeability, or cellular uptake related to certain
therapeutic compounds delivered within the spine and other
joints.
[0051] Accordingly, one aspect of the invention is a spinal thermal
therapy system with a spinal delivery system and a spinal thermal
therapy device. The spinal delivery system is adapted to deliver a
thermal therapy assembly of the spinal thermal therapy device to a
location within the body such that the energy may be coupled to a
region of tissue associated with a vertebral joint.
[0052] One mode of this aspect, the thermal therapy assembly is
adapted to deliver sufficient energy to the region of tissue to
heat the region to a temperature less than about 65 degrees C. and
to deliver a thermal dose of at least about 240 EM43.
[0053] According to one embodiment of this mode, the assembly is
adapted to heat the region sufficiently to form cellular necrosis,
but not to cause substantial denaturation of collagen, and in
particular with respect to regions of tissue under mechanical
stress.
[0054] Another mode of this aspect, the thermal therapy assembly is
adapted to heat the region of tissue to a temperature of greater
than about 65 degrees C.
[0055] According to one further embodiment of this mode, the
thermal therapy assembly is adapted to heat the region of tissue to
a temperature of greater than about 70 degrees C.
[0056] According to a further feature of this embodiment, the
thermal therapy assembly is adapted to heat the region of tissue to
a temperature of greater than a bout 75 degrees C.
[0057] According to another embodiment, the thermal therapy
assembly that is adapted to heat the region of tissue to a
temperature that is greater than about 65 degrees C. but is less
than about 100 degrees C.
[0058] In a further variation of this embodiment, the thermal
therapy assembly is adapted to heat the region to a temperature
between about 65 degrees C. and about 85 degrees C.
[0059] Another aspect of the invention is an ultrasound energy
delivery system for treating a region of tissue associated with a
skeletal joint, and includes an ultrasound treatment assembly with
an ultrasound transducer; and a skeletal joint delivery assembly.
The skeletal joint delivery assembly is adapted to deliver the
ultrasound treatment assembly into the body with the ultrasound
transducer positioned at a location within the body associated with
the skeletal joint. The ultrasound treatment assembly is adapted to
deliver a therapeutic level of ultrasound energy from the location
and into the region of tissue.
[0060] According to one mode of this aspect, the ultrasound
transducer is constructed to provide directional thermal therapy to
the region of tissue. According to another mode, the ultrasound
transducer is constructed to deliver a converging field of energy
to the region of tissue. In another mode, the ultrasound transducer
is constructed to deliver a diverging field of ultrasound energy to
the region of tissue. In another mode, the ultrasound transducer is
constructed to deliver a substantially collimated field of
ultrasound energy to the region of tissue. In still another mode,
the ultrasound treatment assembly comprises a coupling member
positioned so as to couple ultrasound energy from the ultrasound
transducer to the region of tissue. Further embodiments for the
coupling member it is a balloon that may be either elastomeric or
pre-formed and noncompliant.
[0061] According to further modes, a temperature control system is
provided that is adapted to control the temperature of at least one
of the ultrasound transducer or a tissue interface between a region
of tissue and the ultrasound treatment assembly during ultrasound
energy delivery to the region of tissue.
[0062] Another mode further includes an ultrasound control system
with a temperature monitoring system, a controller, and an
ultrasound drive system. The ultrasound treatment assembly is
adapted to couple to the ultrasound control system. The ultrasound
control system is adapted to control the ultrasound energy being
emitted by the ultrasound transducer as a function of at least one
parameter related to thermal therapy in the region of tissue.
[0063] In a further embodiment, the parameter comprises a parameter
related to the effects of ultrasound delivery from the ultrasound
transducer in tissue, such as thermal dose, tissue temperature,
depth of thermal penetration, or rates of change thereof. Such
parameter may be empirically based, or a value that is monitored
during ultrasound therapy, and/or calculated based upon another
measured parameter.
[0064] In other embodiment the controller is adapted to control the
operation of the ultrasound transducer such that the temperature in
at least a portion of the tissue within at least a 4 mm depth from
the ultrasound transducer is elevated to at least about 70 degrees
C. In another embodiment, the controller is adapted to control the
operation of the ultrasound transducer such that the temperature of
the tissue within the 4 mm depth is elevated to at least about 75
degrees C. In another embodiment, the controller is adapted to
control the operation of the ultrasound transducer such that the
temperature in tissue within up to at least about a 7 mm depth from
the ultrasound transducer is elevated to at least about 70 degrees
C. In still a further embodiment, the controller is adapted to
control the operation of the ultrasound transducer such that the
temperature in tissue within up to at least a 10 mm depth from the
ultrasound transducer is elevated to greater than about 45 degrees
C.
[0065] In still a further embodiment, the controller is adapted to
control the operation of the ultrasound transducer such that the
temperature within the tissue are limited to not exceed certain
values. In one such embodiment the control is set for tissue at up
to at least a 4 mm depth from the ultrasound transducer not to
exceed an elevated temperature of about 75 degrees C. or less. In
another embodiment, the controller is adapted to control the
operation of the ultrasound transducer such that the temperature of
the tissue within the 4 mm depth is elevated to an elevated
temperature of no more than about 70 degrees C. or less. In another
embodiment the controller is adapted to control the operation of
the ultrasound transducer such that the temperature in tissue
within up to at least a 7 mm depth from the ultrasound transducer
is elevated to at least 70 degrees C.
[0066] Further modes provide the treatment assembly in a manner
adapted to provide certain ideal temperature delivery objectives.
In one such mode, the device is adapted to heat tissue within up to
at least a 10 mm depth from the ultrasound transducer is elevated
to greater than 45 degrees C. In another embodiment, the ultrasound
treatment assembly is adapted to heat tissue up to a distance of at
least about 4 mm from the ultrasound transducer to a temperature of
at least about 70 degrees C.
[0067] In another embodiment, the ultrasound heating assembly is
adapted to heat the tissue within the 4 mm depth to a temperature
of at least about 75 degrees C. In still another embodiment, the
ultrasound treatment assembly is adapted to heat the tissue at
least about 4 mm away from the transducer to the temperature of at
least about 75 degrees C. in less than about 5 minutes of
ultrasound energy delivery into the tissue. In yet a further
embodiment, the ultrasound treatment assembly is adapted to heat
tissue up to a distance of at least about 7 mm from the ultrasound
transducer to a temperature of at least about 70 degrees C. In
further embodiments, the ultrasound treatment assembly is adapted
to heat tissue up to a distance of at least about 10 mm from the
ultrasound transducer to a temperature of at least about 45 degrees
C. In another embodiment, the ultrasound treatment assembly is
adapted to heat tissue up to a distance of at least 4 mm from the
ultrasound transducer to a temperature of no more than about 75
degrees C. or less.
[0068] According to another mode, the ultrasound treatment assembly
is adapted to be positioned within an intervertebral disc and to
heat at least portion of the disc.
[0069] In another mode, the ultrasound treatment assembly is
adapted to be positioned at a location adjacent to an
intervertebral disc and to provide thermal therapy to the
intervertebral disc from the location.
[0070] In another mode, the ultrasound treatment assembly is
adapted to positioned within at least a portion of a vertebral
body, or posterior vertebral element such as facet joints, and to
provide thermal therapy at least in part to such structure.
[0071] In another mode, it is adapted to be positioned adjacent to
such spinal joint bony structures and to heat at least a portion of
the vertebral body.
[0072] Another aspect of the invention is a skeletal joint thermal
therapy device with a thermal treatment assembly on the distal end
of a delivery member. The thermal treatment assembly includes an
energy emitter. The distal end portion is adapted at least in part
to deliver the thermal treatment assembly into a body of an animal
with the energy emitter positioned at a location such that the
energy emitter is adapted to deliver energy into a region of tissue
associated with a skeletal joint. The thermal treatment assembly is
adapted to heat tissue up to a distance of at least 4 mm from the
energy emitter to a temperature of at least 75 degrees C., and is
adapted to heat tissue up to a distance of at least about 7 mm from
the energy emitter to a temperature of at least about 55 degrees
C., and is adapted to heat tissue up to a distance of at least
about 10 mm from the energy emitter to a temperature of at least
about 45 degrees C.
[0073] In one further mode of this aspect, the thermal treatment
assembly is adapted to heat tissue up to a distance of at least 4
mm from the energy emitter to a temperature of at least 80 degrees
C. In another mode, the thermal treatment assembly is adapted to
heat tissue up to a distance of at least 4 mm from the energy
emitter to a temperature of at least 85 degrees C. In still another
mode, the thermal treatment assembly is adapted to heat tissue up
to a distance of at least 7 mm from the energy emitter to a
temperature of at least 60 degrees C. In yet another mode, the
thermal treatment assembly is adapted to heat tissue up to a
distance of at least 7 mm from the energy emitter to a temperature
of at least 65 degrees C. A further modes provides the thermal
treatment assembly adapted to heat tissue up to a distance of at
least 7 mm from the energy emitter to a temperature of at least 70
degrees C. Still further, the thermal treatment assembly may be
further adapted to heat tissue up to a distance of at least 10 mm
from the energy emitter to a temperature of at least 50 degrees C.
It may also be adapted to heat tissue up to a distance of at least
10 mm from the energy emitter to a temperature of at least 55
degrees C. Even still further, it may be adapted to heat tissue up
to a distance of at least 10 mm from the energy emitter to a
temperature of at least 60 degrees C.
[0074] In yet another mode, the thermal treatment assembly is
constructed to provide directional thermal therapy to the region of
tissue.
[0075] In another highly beneficial mode, the energy emitter
comprises an ultrasound transducer.
[0076] In another mode, the ultrasound treatment assembly comprises
a coupling member positioned so as to couple ultrasound energy from
the ultrasound transducer to the region of tissue.
[0077] Another aspect of the invention is an ultrasound thermal
treatment system with an ultrasound treatment assembly with an
ultrasound transducer on a distal end portion of a rigid delivery
probe. The probe's distal end portion has a proximal section with a
longitudinal axis, a distal section with a distal tip, and a bend
between the proximal and distal section. The ultrasound treatment
assembly is located along the distal section of the distal end
portion and extending at an angle from the proximal section. The
distal end portion is adapted to be delivered into the body of an
animal by manipulating the proximal end portion externally of the
body and such that the ultrasound treatment assembly is positioned
at a location associated with a region of tissue to be treated.
Moreover, the ultrasound treatment assembly is adapted to deliver a
therapeutic level of ultrasound energy into the region of tissue
from the location within the body.
[0078] In one further mode of this aspect, the proximal end portion
of the rigid delivery probe comprises a metal tube.
[0079] In another mode, the distal end portion of the rigid
delivery probe comprises a metal tube.
[0080] In another mode, the ultrasound transducer is constructed to
provide directional ultrasound delivery to the region of
tissue.
[0081] In another mode, the ultrasound transducer is constructed to
deliver a converging field of ultrasound energy to the region of
tissue.
[0082] Another aspect of the invention is an ultrasound thermal
therapy system with an ultrasound heating assembly with an
ultrasound transducer and a therapy control system coupled to the
ultrasound heating assembly. The ultrasound heating assembly is
adapted to be delivered into a body of an animal with the
ultrasound transducer positioned at a location such that the
ultrasound transducer is adapted to deliver a therapeutic amount of
ultrasound energy into a targeted region of tissue in the body from
the location. The therapy control system is adapted to control
operation of the ultrasound heating assembly such that a
substantial portion of the region of tissue being heated by the
ultrasound heating assembly does not exceed a maximum temperature
of at least about 70 degrees C.
[0083] According to one further mode of this aspect, the therapy
control system is adapted to control operation of the ultrasound
heating assembly such that a substantial portion of the region of
tissue being heated by the ultrasound heating assembly does not
exceed a maximum temperature of at least about 75 degrees C.
[0084] Another aspect of the invention is a directional ultrasound
spinal thermal therapy system with an ultrasound delivery assembly.
The ultrasound delivery assembly has a directional ultrasound
transducer that is adapted to be positioned at a location
associated with a spinal joint and to deliver a directed,
therapeutic amount of ultrasound energy from the location and to a
region of tissue associated with the spinal joint.
[0085] In one mode of this aspect, the ultrasound delivery assembly
is adapted to direct the ultrasound delivery into substantially
only a particular radial zone around the circumference of the
distal end portion of the support member.
[0086] In another mode, the ultrasound delivery assembly is
constructed to provide directional thermal therapy to the region of
tissue.
[0087] In another mode, the ultrasound delivery assembly is
constructed to deliver a converging field of energy to the region
of tissue.
[0088] In another mode, the ultrasound treatment assembly comprises
a coupling member positioned so as to couple ultrasound energy from
the ultrasound transducer to the region of tissue.
[0089] In another mode, the ultrasound delivery assembly is adapted
to be positioned at the location within at least a portion of an
intervertebral disc associated with the spinal joint and to deliver
the therapeutic ultrasound energy into the region of tissue from
that location.
[0090] In another mode, the ultrasound delivery assembly is adapted
to be positioned at the location outside of an intervertebral disc
associated with the spinal joint and to deliver the therapeutic
level of ultrasound energy into the intervertebral disc from that
location.
[0091] In another mode, the ultrasound delivery assembly is adapted
to be positioned at the location within at least a portion of a
vertebral body and/or posterior vertebral elements such as facet
joints associated with the spinal joint and to be ultrasonically
coupled with the region of tissue from that location.
[0092] In another mode, the ultrasound delivery assembly is adapted
to be positioned at the location outside of a vertebral body and/or
posterior vertebral elements such as facet joints associated with
the spinal joint and to deliver the therapeutic level of ultrasound
energy into the intervertebral disc from that location.
[0093] Another aspect of the invention is a skeletal joint
ultrasound delivery system with an ultrasound treatment assembly
with an ultrasound transducer and a coupling member. The ultrasound
delivery assembly is adapted to be delivered into a body of a
mammal with the ultrasound transducer positioned at a location
within the body associated with a skeletal joint. The ultrasound
transducer is adapted to deliver a therapeutic amount of ultrasound
energy to a region of tissue associated with the skeletal joint via
the coupling member.
[0094] In one further mode, the ultrasound delivery assembly is
constructed to provide directional ultrasound delivery to the
region of tissue.
[0095] In another further mode, the ultrasound delivery assembly is
constructed to deliver a converging field of energy to the region
of tissue.
[0096] In another mode, the ultrasound treatment assembly comprises
a coupling member positioned so as to couple ultrasound energy from
the ultrasound transducer to the region of tissue.
[0097] Another aspect of the invention is an ultrasound thermal
therapy system with an ultrasound heating assembly and a control
system. The ultrasound heating assembly is adapted to be positioned
at a location within a body of a mammal so as to deliver ultrasound
energy into a region of tissue in the body from the location. The
control system is adapted to couple to the ultrasound heating
assembly and to control operation of the ultrasound heating
assembly such that a region of tissue being heated by the
ultrasound heating assembly exceeds a temperature of at least about
70 degrees C.
[0098] Another aspect of the invention is an ultrasound thermal
therapy system with a an ultrasound heating assembly located along
the distal end portion of a delivery member. The ultrasound heating
assembly has a curvilinear ultrasound transducer having a concave
surface with a radius of curvature around a reference axis that is
transverse to the longitudinal axis of the distal end portion.
[0099] The invention according to another mode is a method for
invasively treating a medical condition associated with a skeletal
joint within a body of an animal. This method includes delivering a
therapeutic level of ultrasound energy to a region of tissue
associated with the joint from a location within the body of the
patient.
[0100] Another aspect of the invention is a method for treating a
medical condition associated with a skeletal joint within a body by
delivering sufficient energy to a region of tissue associated with
the skeletal joint that is sufficient to necrose nociceptive nerve
fibers or inflammatory cells in such tissue region without
substantially affecting collagenous structures associated with the
skeletal joint.
[0101] One mode of this aspect further includes delivering the
energy into the region of tissue while the region of tissue is
under mechanical stress; and heating the tissue to a temperature of
up to no more than 75 degrees C.
[0102] Another mode includes heating the tissue to a temperature of
up to no more than 70 degrees C.
[0103] Another aspect of the invention is a method for treating a
region of tissue associated with an intervertebral disc in a body
of an animal by delivering an ultrasound transducer to a location
within the body such that a therapeutic level of ultrasound may be
coupled from the transducer to the tissue.
[0104] One mode of this aspect includes delivering energy to a
region of tissue associated with the spine, wherein such tissue
does not experience a rise in temperature of more than about 55
degrees C.
[0105] Another aspect of the invention is a method for treating an
animal by delivering energy to a region of tissue associated with
the spine, wherein such energy delivery is between about 10 and
about 300 equivalent minutes at 43 degrees C.
[0106] Another aspect is a method for invasively treating a medical
condition associated with an intervertebral disc within a body of
animal by delivering a therapeutic level of ultrasound energy to a
region of tissue associated with an intervertebral disc from a
location within the body of the patient.
[0107] Another aspect of the invention is a method for treating
medical condition associated with a joint between two bony
structures in a body of an animal by delivering an ultrasound
transducer to a location within the patient's body associated with
the joint; and emitting ultrasound energy from the transducer at
the location so as to provide a therapeutic effect to at least a
portion of the joint.
[0108] Another aspect of the invention is a method for treating an
animal by introducing an ultrasound transducer into a body of the
animal; positioning the ultrasound transducer at a location within
the animal that is adjacent to at least one of an annulus fibrosus
of an intervertebral disc, a nucleus pulposus of the intervertebral
disc, or a vertebral body associated with a spinal joint in the
body; and emitting ultrasound energy from the ultrasound transducer
at the location.
[0109] Another aspect of the invention is a method for providing
ultrasound energy delivery within a body of an animal by
introducing an ultrasound transducer into a body of a patient;
positioning the ultrasound transducer at a location within the
patient that is within at least one of an annulus fibrosus of an
intervertebral disc, a nucleus pulposus of the intervertebral disc,
or a vertebral body associated with a spinal joint in the body; and
emitting ultrasound energy from the ultrasound transducer at the
location.
[0110] Another aspect of the invention is a method for treating a
patient by ultrasonically heating a region of tissue associated a
spinal joint to a temperature between about 45 to about 90 degrees
Fahrenheit for sufficient time to cause a therapeutic result in the
tissue.
[0111] The method according to one further mode includes providing
sufficient thermal dose so as to cause necrosis effect in
nociceptive nerve fibers or inflammatory cells in the region of
tissue.
[0112] Another mode includes providing sufficient thermal dose at
appropriate temperature so as to stimulate cellular metabolism
without substantially killing cells in the region of tissue.
[0113] Another mode includes delivering sufficient thermal dose and
temperature in the region of tissue to cause a substantially
non-necrotic cellular effect.
[0114] Another mode includes delivering sufficient thermal dosing
to the region of tissue to cause preferential regeneration.
[0115] Another mode includes delivering sufficient thermal dose to
the region of tissue to cause inhibition of inflammatory factors or
cytokines.
[0116] Another mode includes delivering sufficient thermal dose to
the region of tissue to cause modification of a healing response to
injury in the region of tissue.
[0117] Further objects and advantages of the invention will be
brought out in the following portions of the specification, wherein
the detailed description is for the purpose of fully disclosing
preferred embodiments of the invention without placing limitations
thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
[0118] The invention will be more fully understood by reference to
the following drawings which are for illustrative purposes
only:
[0119] FIG. 1A shows a side perspective view of an illustration of
a typical human spine for treatment according to the systems and
methods of the invention.
[0120] FIG. 1B shows an exploded, cross-sectioned side view of the
region depicted as 1B in FIG. 1A, and shows an intervertebral disc
between two adjacent vertebral bodies.
[0121] FIG. 2 shows an angular perspective view of a transversely
cross-sectioned intervertebral disc in relation to adjacent spinal
structures.
[0122] FIG. 3A shows an angular perspective view of an ultrasonic
intervertebral disc therapy system according to the invention, and
includes a partially segmented view of an ultrasound treatment
device, a schematic view of an ultrasound drive system, and an
angular perspective view of an introduction device, respectively,
of the system.
[0123] FIG. 3B shows a longitudinal side view taken along lines
3B-3B in
[0124] FIG. 3A.
[0125] FIG. 3C shows a transverse cross-sectioned view taken along
lines 3C-3C in FIG. 3A.
[0126] FIG. 4 shows a transverse cross-sectioned view of the distal
end portion of another ultrasound treatment device of the invention
with a different support structure under the ultrasound transducer
of the device than the support structure shown in FIG. 3C.
[0127] FIG. 5A shows a slightly angled side view of the distal end
portion of another ultrasound treatment device according to the
invention, and also shows a schematic view of a guide wire included
in the system.
[0128] FIG. 5B shows a cross-sectioned side view of the device
taken along lines 5B-5B in FIG. 5A.
[0129] FIG. 6A shows a slightly angled side view of an ultrasound
transducer component assembly for use in the distal end portion of
another ultrasound treatment device according to the invention.
[0130] FIG. 6B shows a cross-sectioned transverse view taken along
lines 6B-6B in FIG. 6A.
[0131] FIG. 6C shows a schematic cross-sectioned side view of an
alternative ultrasound transducer component assembly within an
ultrasound treatment device according to the invention versus that
shown in FIG. 6B.
[0132] FIG. 6D shows an angular perspective view of a
semi-spherical disc-shaped transducer for use according to a
further embodiment of the invention.
[0133] FIGS. 7A-F show a top perspective view of a laterally
cross-sectioned intervertebral disc during respectively sequential
modes of operating the ultrasound treatment system for
intervertebral disc therapy according to the invention.
[0134] FIGS. 8-9 show alternative modes of operating an ultrasound
treatment device according to the invention for treating different
respective regions of an annulus fibrosus of a disc from within the
nucleus and according to a posterior-lateral approach into the
disc.
[0135] FIG. 10 shows an alternative mode of operating an ultrasound
treatment device according to the invention using an anterior
approach to treat a posterior wall region of the annulus fibrosus
of a disc from within the nucleus of the disc.
[0136] FIGS. 11-13 show alternative modes of operating an
ultrasound treatment device for treating different respective
regions of an annulus fibrosus of a disc from externally of the
annulus fibrosus and without entering the nucleus, wherein FIGS. 11
and 13 show a posterior-lateral approach to right lateral and
posterior wall regions of the annulus, respectively, and FIG. 12
shows an anterior approach to a left lateral wall region of the
annulus.
[0137] FIGS. 14A-B show plan perspective views of the distal end
portion of another ultrasound treatment device of the invention
during various modes of operation, wherein FIG. 14A shows a
straight configuration for the device, and FIG. 14B shows two modes
of angular deflection for the distal end portion of the device.
[0138] FIG. 14C shows a top perspective view of another ultrasound
treatment device of the invention with a distal ultrasound
treatment section that is adapted to be rotated about a hinge point
for minimally invasive treatment of intervertebral discs and other
spine or joint disorders.
[0139] FIG. 15A shows a plan perspective view of the distal end
portion of another ultrasound treatment device of the invention
having a predetermined shape and operative region for ultrasound
delivery that corresponds to particular desired approaches and
ultrasound therapy to certain specified regions of tissue
associated with an intervertebral disc.
[0140] FIG. 15B shows a perspective view of another ultrasound
treatment device having a similar shape to that shown in FIG. 15A,
but having a different operative region for ultrasound delivery
corresponding to delivering invasive therapy to a different desired
region of a respective intervertebral disc.
[0141] FIG. 16 shows a perspective view of another ultrasound
treatment device having a different unique shape and operative
region for ultrasound delivery corresponding to delivering invasive
therapy to a different desired region of a respective
intervertebral disc.
[0142] FIG. 17A shows a top view of an ultrasound treatment device
assembly with transducers inside of an outer cooling jacket that is
interfaced with a fluid circulation pump to actively cool the
transducers.
[0143] FIG. 17B shows a top view of another partially
cross-sectioned ultrasound treatment device assembly similar to
that shown in FIG. 17A, except showing the cooling fluid to
circulate from within the ultrasound transducer device and into the
surrounding sheath.
[0144] FIG. 18A shows an x-ray picture of an explanted disc being
treated according to one aspect of the invention, and shows various
data points along temperature monitoring probes inserted along
certain desired locations for monitoring across the disc.
[0145] FIG. 18B shows a graph of temperature vs. time for an
ultrasound heating study in an explanted cadaver spine disc, and
shows curves for tissue depths of 1 mm, 4 mm, 7 mm, and 10 mm away
from the directional heating transducer.
[0146] FIG. 19 shows a typical modulus versus applied stress plot
according to a study performed in Example 2, and shows results
before (solid line) and after (dashed line) heat treatment at
85.degree. C., and indicates the following biomechanical
parameters: change in modulus at the inflection point (MI), change
in modulus at 150 kPa (M150), and change in residual stress at the
inflection point (RSI).
[0147] FIG. 20 shows a typical stress-strain plot before (solid
line) and after (dashed line) treatment at 85.degree. C., and shows
for each cycle an upper line indicating the loading phase, and a
lower curve indicating the unloading phase.
[0148] FIG. 21 shows graphs (a)-(e) that variously represent
respective changes in certain tissue parameters that were observed
after varied heat treatments.
[0149] FIG. 22 shows various light microscopy photographs of
various tissue samples, and includes bright light (left panel) and
polarized light (right panel) microscopy of specimens treated, and
shows pictures (a, b) for samples intact at 37.degree. C.; pictures
(c, d) for intact samples at 85.degree. C.; and pictures (d, e)
representing excised at 85.degree. C.
[0150] FIG. 23 shows a schematic side view of a distal end portion
of an external directional ultrasound thermal treatment
("ExDUSTT.TM.") device of the invention incorporating a
directional, focused ultrasound emitter assembly that is adapted
for external use adjacent to an intervertebral disc.
[0151] FIG. 24 shows an illustrated side view of a partially
cross-sectioned ultrasound spinal treatment assembly similar to
that shown in the ExDUSTT device shown in FIG. 23, and shows the
assembly during one mode of use in treating a region of an
intervertebral disc associated with a spinal joint.
[0152] FIG. 25 shows a plan view of a distal end portion of a
further ExDUSTT embodiment that incorporates a substantially rigid,
pre-shaped probe device platform.
[0153] FIG. 26 shows a plan view of a distal end portion of another
ExDUSTT device embodiment that incorporates a substantially
flexible, catheter device platform according to another embodiment
of the invention.
[0154] FIG. 27A shows a longitudinally cross-sectioned view of a
distal end portion of an ExDUSTT device on a rigid probe platform
similar to that shown in FIG. 25, and shows a substantially
compliant elastomeric balloon over a curvilinear ultrasound
transducer.
[0155] FIG. 27B shows a transverse cross-sectioned view through an
ultrasound transducer mounting region of the ExDUSTT device shown
in FIG. 27A.
[0156] FIG. 28A shows a longitudinally cross-sectioned view of a
distal end portion of another ExDUSTT device on a rigid probe
platform that is also similar to that shown in FIG. 25, except with
a substantially non-compliant pre-formed balloon over the
curvilinear ultrasound transducer.
[0157] FIG. 28 B shows a transverse cross-sectioned view through an
ultrasound transducer mounting region of the ExDUSTT device shown
in FIG. 28A.
[0158] FIG. 29A shows a transverse cross-sectioned view of a distal
end portion of another ExDUSTT device on a polymeric catheter
delivery chassis similar to that shown in FIG. 26, and shows a
substantially compliant elastomeric balloon over a transversely
aligned, curvilinear ultrasound transducer.
[0159] FIG. 29 B shows a transverse cross-sectioned view through an
ultrasound transducer mounting region of the ExDUSTT device shown
in FIG. 29A.
[0160] FIG. 30A shows a transverse cross-sectioned view of a distal
end portion of another ExDUSTT device on a catheter delivery
platform similar to that shown in FIG. 29A, except with an axially
aligned, curvilinear ultrasound transducer within a substantially
compliant elastomeric balloon.
[0161] FIG. 30B shows a transverse cross-sectioned view through an
ultrasound transducer mounting region of the ExDUSTT device shown
in FIG. 30A.
[0162] FIGS. 31A-B show two respective graphs for acoustic
efficiency and acoustic output power, respectively, for one
exemplary working embodiment of a rigid probe ExDUSTT device
similar to that shown in FIG. 25.
[0163] FIGS. 32A-B show two respective graphs for acoustic
efficiency and acoustic output power, respectively, for one
exemplary working embodiment of a catheter-based ExDUSTT device
similar to that shown in FIG. 26.
[0164] FIG. 33 shows a schematic drawing of an ultrasound heating
assembly portion of a catheter-based ExDUSTT device similar to that
shown in FIG. 26 superimposed over an X-ray picture of the
intervertebral disc to illustrate one experimental set-up to
evaluate the device, and also shows superimposed reference numbers
designating certain monitored temperatures at various locations
within the disc during one mode of treatment.
[0165] FIG. 34A-B show two respective graphs of temperature
monitored over time at various thermocouples locations
105(C)-109(C) during two respective in-vivo thermal therapy
treatments in an intervertebral pig disc using a catheter-based
ExDUSTT device similar to that shown in FIG. 26 and according to an
experimental set-up similar to that shown in FIG. 33.
[0166] FIG. 35 shows two, respective ExDUSTT devices of pre-shaped,
rigid probe construction similar to that shown in FIG. 25, except
the devices shown are constructed according to different size
embodiments incorporating ultrasound transducers having varied
respective widths of 2.5 mm and 3.5 mm, respectively.
[0167] FIGS. 36A-B show top and angular perspective views,
respectively, of certain power output profile across the face of
the 2.5 mm wide transducer shown in FIG. 35A.
[0168] FIGS. 37A-B show top and angular perspective views,
respectively, of certain power output profiles across the face of
the 3.5 mm wide transducer shown in FIG. 31B.
[0169] FIG. 38 shows an X-ray picture of a top view of an ex-vivo
experimental arrangement similar to that shown schematically in
FIG. 33, except showing a directional ultrasound heating assembly
of a working embodiment for a probe-based ExDUSTT device such as
shown in FIG. 25 positioned for desired heating of an
intervertebral disc according to one modes of use, and shows
various thermocouple probes within the disc to monitor experimental
temperatures.
[0170] FIG. 39 shows an exploded view of the same Ex-DUSTT
intervertebral disc treatment arrangement shown for the 3.5 mm
probe-like ExDUSTT device in FIG. 38, and shows monitored
temperature values at various respective locations along the axial
and radial temperature probes during one relatively high
temperature mode of use with active cooling at 0 degrees C.
[0171] FIG. 40 shows a graph of temperature vs. time for the
various temperature probes according to the thermal therapy
arrangement shown in FIG. 39.
[0172] FIG. 41 shows a graph of temperature monitored along the 5
mm and 10 mm deep axial temperature sensor probes and the radial
temperature sensor probes shown within the intervertebral disc and
during treatment with the probe-based ExDUSTT with the 3.5 mm wide
transducer shown in FIG. 38, and according to an ex-vivo study
performed with active transducer cooling at 0 degrees C.
[0173] FIG. 42 shows the same exploded view of the experimental
arrangement shown in FIG. 39, except shows thermocouple values
corresponding to a relatively low temperature mode of operation
with room temperature cooling.
[0174] FIG. 43 shows a similar graph of temperature vs. time as
that shown in FIG. 40, except with respect to data measured
according to the arrangement illustrated for FIG. 42.
[0175] FIG. 44 shows another graph of certain temperature vs.
transducer position results similar to the graph shown in FIG. 41,
except showing results according to the mode of operation also
variously illustrated in FIGS. 42-43.
[0176] FIG. 45 shows a similar exploded X-ray picture to that shown
in FIGS. 39 and 42, except showing thermocouple values according to
a relatively low temperature mode of operation using a 3.5 mm wide
transducer and cooling at 0 degrees C.
[0177] FIG. 46 shows another temperature vs. time graph, except
with respect to the arrangement also illustrated in FIG. 45.
[0178] FIG. 47 shows a graph of temperature vs. thermocouple
position results according to the thermal therapy arrangement
illustrated in FIGS. 45 and 46.
[0179] FIG. 48 shows another exploded X-ray picture of the same
ExDUSTT arrangement, except according to use of a 2.5 mm wide
transducer with relatively low temperature heating mode and cooling
at 0 degrees C.
[0180] FIG. 49 shows another temperature vs. time graph for the
ExDUSTT heating arrangement illustrated in FIG. 48.
[0181] FIG. 50 shows another temperature vs. thermocouple position
graph for a 2.5 mm curvilinear ExDUSTT ex-vivo disc treatment using
0 degree C. cooling and relatively low temperature mode of
operation.
[0182] FIG. 51 shows another exploded X-ray picture, except with
thermocouple values corresponding to use of a 2.5 mm transducer
ExDUSTT device at a relatively low temperature mode of use with
room temperature cooling.
[0183] FIG. 52 shows a temperature vs. time graph according to the
ExDUSTT mode of therapy also illustrated in FIG. 51.
[0184] FIG. 53 shows a temperature vs. thermocouple position graph
for the modes of ExDUSTT therapy illustrated in FIGS. 51 and
52.
[0185] FIG. 54 shows a perspective view of an internal directional
ultrasound thermal therapy system ("InDUSTT.TM.") that includes a
spinal disc delivery probe and an InDUSTT device that fits within
the spinal disc delivery probe.
[0186] FIG. 55A shows a plan view of a schematic representation of
an internal ultrasound thermal spine therapy device according to
another embodiment of the invention.
[0187] FIG. 55B shows an exploded view taken at region B shown in
FIG. 55A, and shows enhanced detail of various aspects of the
ultrasound heating assembly along the distal end portion of the
InDUSTT system according to a further feature of that
embodiment.
[0188] FIG. 55C shows a transverse cross-sectioned view taken along
line C-C in FIG. 55A.
[0189] FIGS. 56A-B show respective X-ray pictures of the distal end
portion of an InDUSTT system similar to that shown in FIGS. 54-55B
positioned within an intervertebral disc during in-vivo thermal
spinal treatments according to certain modes of the invention.
[0190] FIG. 57 shows a table providing thermal dosimetry data
collected during certain modes of in-vivo operation for various
working embodiments of an InDUSTT system similar to that shown in
FIGS. 54-55B and providing therapeutic ultrasonic heating at
various temperature modes of powered operation corresponding to
C2/3, C3/4, C4/5, and C5/6 intervertebral sheep discs,
respectively.
[0191] FIG. 58 shows various X-ray pictures of the placement of the
InDUSTT transducer within the C2/3, C3/4, C4/5, and C5/6
intervertebral discs corresponding to the results provided in the
table in FIG. 57.
[0192] FIG. 59A shows a graph of temperature vs. time during
InDUSTT heating of a C3/4 intervertebral disc according to a
relatively high temperature mode of use, and shows curves for
various respective thermocouple probe positions.
[0193] FIG. 59B shows a graph of temperature vs. time using the
same InDUSTT device as that used for creating the data shown in
FIG. 59A, except shows results according to a relatively low
temperature mode of use in a C4/5 intervertebral disc location.
[0194] FIG. 59C shows a graph of temperature monitored at various
temperature sensor positions during 10 minute InDUSTT heating, and
shows curves for results in two separate intervertebral discs each
heated with a different one of two separate InDUSTT systems of the
invention.
[0195] FIG. 60 shows another table providing thermal dosimetry data
collected during modes of in-vivo operation for various working
embodiments of a directly coupled InDUSTT system providing
therapeutic ultrasonic heating from within C2/3, C3/4, and C4/5
intervertebral discs of a sheep.
[0196] FIG. 61 shows various respective X-ray pictures of certain
transducer placements for the directly coupled InDUSTT during
in-vivo spinal disc thermal therapy at the C2/3, C3/4, and C4/5
intervertebral sheep discs corresponding to the similarly
designated rows of data illustrated in the table of FIG. 60.
[0197] FIG. 62A shows a graph of temperature vs. time corresponding
to the C2/3 disc treatment shown in FIG. 61 and according to a
relatively high temperature mode of use.
[0198] FIG. 62B shows a graph of temperature vs. time corresponding
to the C3/4 disc treatment shown in FIG. 61, and according to a
relatively low temperature mode of use.
[0199] FIG. 62C shows a graph of temperature monitored at various
temperature sensor positions during 10 minute directly coupled
InDUSTT heating, and shows curves for thermal treatment results at
both dead sectors and active sectors of the transducer in the C2/3
disc at relatively high temperature power level, and at similar
locations in the C3/4 disc at the corresponding, relatively low
temperature power level.
[0200] FIG. 62D shows a graph of accumulated thermal dose versus
temperature sensor position for the 10 minute treatments at the
C2/3 and C3/4 discs at the relatively high and low temperature
power levels, respectively.
[0201] FIG. 63 shows another table providing thermal dosimetry data
collected during modes of in-vivo operation for various working
embodiments of a catheter cooled InDUSTT system providing
ultrasonic heating from within C2-3, C3-4, C4-5, and C5-6
intervertebral discs of a sheep.
[0202] FIG. 64 shows various respective X-ray pictures of certain
transducer placements for the catheter cooled InDUSTT during
in-vivo thermal spinal disc therapy at the C2-3, C3-4, C4-5 and
C5-6 intervertebral discs corresponding to the similarly designated
rows of data illustrated in the table of FIG. 63.
[0203] FIG. 65A shows a graph of the relatively high temperature,
catheter cooled InDUSTT therapy of the C2/3 disc as monitored over
multiple temperature sensors along first and second temperature
probes positioned within the disc.
[0204] FIG. 65B shows a temperature vs. time graph of the
relatively low temperature mode of operation for the catheter
cooled InDUSTT therapy in the C3/4 disc and as monitored over
multiple temperature sensors along first and second temperature
monitoring probes positioned within the disc.
[0205] FIG. 65C shows a temperature vs. time graph of the
relatively high temperature, catheter cooled InDUSTT therapy of the
C5/6 disc as monitored over the multiple temperature sensors along
first and second temperature monitoring probes positioned within
the disc.
[0206] FIG. 65D shows a graph of temperature monitored at various
axial positions relative to the transducer during 10 minute
catheter cooled InDUSTT heating, and shows curves for thermal
treatment results at various locations in the C2/3 disc at
relatively high temperature power level, in the C3/4 disc at
relatively low temperature power level, and C5/6 disc at relatively
high temperature power levels.
DETAILED DESCRIPTION OF THE INVENTION
[0207] Referring more specifically to the drawings, for
illustrative purposes the present invention is intended to provide
thermal treatment to spinal joints, and in particular
intervertebral discs as illustrated in FIGS. 1A-2, as embodied in
the apparatus shown and characterized by way of the various modes
of operation with respect to certain intended anatomical
environments of use variously throughout FIGS. 3-65D. It will be
appreciated that the apparatus may vary as to configuration and as
to details of the parts, and that the method may vary as to the
specific steps and sequence, without departing from the basic
concepts as disclosed herein.
[0208] As an initial introduction, various respective aspects,
modes, embodiments, variations, and features of the invention are
herein shown and described, both broadly and in variously
increasing levels of detail. Each provides individual benefit,
either in its own regard, or in the ability to provide enhanced
modes of operation and therapy by way of combinations with other
aspects or features. Moreover, their various combinations, either
as specifically shown or apparent to one of ordinary skill, provide
further benefits in providing useful healthcare to patients.
[0209] In one regard, two illustrative ultrasound spinal thermal
therapy probe configurations are described for applying thermal
(heat) therapy or ultrasound (US) exposure to tissues within the
spine or other joints. Heat at high temperatures and thermal doses
can shrink tissues, change the structural matrix, generate
physiological changes and/or kill cells. Heat at relatively lower
temperatures and US exposure can generate permeability changes or
changes in the cellular transport/metabolism that increase
effectiveness or deposition of certain pharmaceutical agents. The
heat or US can be delivered with the present invention in a highly
controlled fashion to selected tissue regions in order to exploit
these physiological effects for therapeutic purposes. Ultrasound
applicators may achieve more precise targeting or heating control
not possible with current RF and Hot Source techniques. For soft
tissue or bone surfaces within the spine or other joints, the high
temperature exposure can be used to shrink tissue impinging on
nerves, re-structure and possibly strengthen mechanical properties
of the disc or joint material, destroy abnormal or undesirable
cells or tissue, destroy nerves responsible for pain, seal leaks
from the disc annulus/nucleus, joint capsules, etc. Novel
ultrasound applicators and treatment methodologies are thus herein
shown and described which allow for the interstitial insertion or
laparoscopic or arthroscopic placement of these applicators within
or upon targeted tissue to receive such treatments or
prophylaxis.
[0210] As will be further developed by reference to the Figures
below, one exemplary type of such an applicator and treatment
methodology provides a segmented array of tubular, sectored
tubular, plate, hemispherical, or portions of cylinders (e.g.
convex) with linear control of US exposure or heating via power
level adjustments and angular control of US exposure or heating via
directional characteristics of the applicators. (e.g. angularly
directive with an inactive zone). These transducers are mounted
over a guidewire lumen or tube or structure to facilitate
placement, wires, and/or cooling structures. Thermometry sensors
can be placed directly on the transducer/tissue or
applicator/tissue interface. Internal cooling via gas or liquid or
external cooling via an outer plastic sheath or catheter can be
accomplished, though may not be necessary in many instances. These
can be inserted within the disc or laparoscopically placed against
the target tissue or directed toward the target tissue. Acoustic
gain and temperature regulation of applicator surface(s) can help
control distance of heated regions and effects from the applicator
surface. Frequency and depth of focus can be selected to control
heating pattern, and time can be varied to control heating effects
and distribution. Some of the device and method embodiments
provided herein may incorporate various features similar to those
previously disclosed such as in U.S. Pat. No. 5,620,479 to
Diederich, though in many instances will be modified specifically
for heating within the special environment of use within or around
intervertebral discs or other joints.
[0211] Another illustrative type of applicator according to the
present invention incorporates a segmented array similar to that
described above, but using concave sections of cylindrical or
tubular transducers or spherical or semi-spherically focused
transducers. The outer diameter (OD) of the tubes used to form such
transducers are much larger than the applicator diameter for the
tubes--the sectors activated are a small arc of the tube they
otherwise would be a part of. Thus, a line of convergence, e.g.
focus, is produced at depth over a small arc angle, producing an
intense US exposure or heating pattern which is approximately the
same length as the tubular segment transducer emitting the US,
though very narrow (e.g. 1-5 degrees) in the angular dimension. The
length and number of segments can be varied in either applicator
type described here for introduction purposes (or elsewhere
herein), and may be a single transducer versus an array. These
applicators can also have internal cooling or external cooling as
described above and further detail with respect to the particular
embodiments below. The applicators can be inserted within the disc
or laparoscopically placed against the target tissue or directed
toward the target tissue. Acoustic gain and temperature regulation
of applicator surface can help control distance of the heated
region and effects from the applicator surface. Further applicable
features may by incorporated from other prior disclosures, such as
U.S. Pat. No. 5,391,197 to Burdette et al. disclosing prostate
therapy devices and methods, and may be modified to suit the
particular needs for the present invention. Frequency and depth of
focus can be selected to control heating pattern, and time can be
varied to control heating effects and distribution.
[0212] The various embodiments herein described have applications
in other soft and/or hard tissue sites and body parts where
ultrasound exposure, high temperature, low temperature, or
combination effects are desired.
[0213] Each type of applicator can be designed with or without
cooling balloons, distendable (e.g. compliant and/or elastomeric)
or pre-shaped (e.g. substantially non-compliant with relatively
fixed inflation size and shape), and symmetric or asymmetric shapes
are considered. The devices' respective chasses may be
substantially stiff, e.g. rigid probes, or flexible. They may
further be either implantable within the target tissue, or be used
on surface contact. They may be delivered on a guidewire rail
platform, through pre-shaped insertion or placement guides, or have
their own steerability or deflectability. For spinal treatments,
they may be placed surgically following for example a posterior
approach, or laparoscopic/arthroscopic lateral/anterior directed to
the spinal joint for treatment.
[0214] Treatment methodologies contemplated include implanting the
devices within or positioning them next to the target tissue for
heating, such as for example inserted into a disc or joint capsule,
or placed outside of the disc or joint.
[0215] Directivity and cooling aspects, when incorporated, protect
sensitive non-targeted tissue, which is highly beneficial for
example in spinal applications protecting spinal nerves.
Applicators herein described are repositionable according to
various modes to control angular thermal profile according to their
directed energy delivery. In one example for further illustration,
a specially adapted spinal disc insertion apparatus is adapted to
deflect an applicator being delivered therethrough into the spinal
disc from an angle. Other special procedures and tools are also
herein described to align the applicators with target areas of
tissue such as with respect to spinal joints and intervertebral
discs in particular.
[0216] Though many different configurations, sizes, shapes, and
dimensions are contemplated consistent with the overall intent to
meet the various objects of the invention, exemplary devices may be
provided with outer diameters between about 1.2 to about 3 mm,
though may be up to 5 mm in some instances, deliverable as desired
to spinal joint areas from 18 gauge.
[0217] Insertion techniques into tissue to be treated may progress
according to several example. In one mode, a relatively stiff (e.g.
sufficient to support the intended use), pre-shaped guidewire is
used which may be with or without memory metal alloy such as nickel
titanium for example. The guidewire is inserted under fluoroscopy
and positioned in an annulus fibrosus or posterior annulus,
avoiding the nucleus of the disc. An applicator of the relatively
more flexible variety is then inserted over the guidewire and into
position. In another regard, a relatively stiff (e.g. sufficient
support) pre-shaped insertion tool guides the applicator with a
sharp tip into the annulus from outside without requiring the
guidewire (though they may be used in conjunction). Similar
insertion techniques may be used for thermometry placement, if
desired. Such delivery tool may thus be multi-lumened to integrate
both placements (e.g. applicator and temperature probes)
simultaneously for better positioning, etc.
[0218] Contact therapy techniques of operation may also proceed
according to a variety of modes. An arthroscopic approach is
suitable for many applications, such as for example as follows.
Internal tip deflection may be used to align (e.g. steer) the
applicator with or along the outside of an annulus--e.g. similar to
certain intracardiac catheters (such as mapping or ablation
devices). Such may be integrated to a steerable catheter. The
device according to these modes may be placed lateral or posterior
behind the disc and nerves, or ventral. The device is aligned with
the disc, the region is targeted and then treated with directional
thermal therapy.
[0219] Various of the components herein described for the various
embodiments may be provided together, or may be provided
separately. For example, implements for providing streaming liquid
or balloon to protect tissue from transducer conductive heating may
be an integral part of the respective applicator, or may be
separate as an accessory.
[0220] The applicators and respective insertion and/or guidance
tools herein described may be further adapted to be compatible with
magnetic resonance imaging for real time monitoring of the
procedure. Other imaging modalities may also be used for
positioning, monitoring, thermal monitoring, lesion assessment,
real-time monitoring of coagulation, etc. This includes ultrasound
monitoring.
[0221] Further to the ultrasound aspects of the various
embodiments, use of such energy modality provides temperature
elevation as one mode of creating an intended effect, but also
provides other non-thermal effects on tissues, such as for example
drug activation, etc., such as for example to treat arthritis at
joints where the applicator is being used.
[0222] It is to be appreciated that the invention is in particular
well adapted for use in treating intervertebral disc disorders of
the spine, such as at spinal joints, and in particular at an
intervertebral disc 1 shown in various relation to surrounding
spinal structures of a spinal joint in FIGS. 1A-2. In particular,
as will be further developed below, disc disorders associated with
chronic lower lumbar back pain are to be beneficially treated
according to the invention. However, it is to be appreciated that
other disorders of the discs in particular, and of other joints
(e.g. hips, knees, shoulders, etc.) may also be treated according
to the device systems and methods herein shown and described. For
example, other regions of the vertebrae will be beneficially
treated with invasive ultrasound delivery according to the
invention in order to promote bone growth, such as for example to
assist in the healing of injuries or bone-grafts. Areas between the
vertebral bodies, or the spinal processes, for example, may be
treated with US application from the present devices and according
to the methods as herein shown and described. In particular,
regions such as graft between inner bodies through nucleus;
anterior inner body fusion; posterior lateral fusion are
contemplated. Ultrasound energy may be delivered with collagen
matrixes or autograft/allograft materials to bone.
[0223] A typical intervertebral disc 1 such as shown in FIGS. 1A-2
generally includes an annulus fibrosus 2 that surrounds a nucleus
pulposus 3 along a plane that lies between two adjacent vertebrae
8,9, respectively, that are located above and below, also
respectively, disc 1 along the spine. More specifically, disc 1
lies between two the two cartilaginous endplates 8a,9a that border
two adjacent vertebral bodies 8b,9b of vertebrae 8,9,
respectively.
[0224] As will be further developed below, an ultrasound treatment
device according to the invention may be located in various places
in and around a disc 1. A variety of such locations is shown for
the purpose of illustration at locations a-d in FIG. 1B, wherein
device 11 is shown: within the middle of the nucleus at location a;
along the border between the nucleus 3 and the annulus 2 such as
shown at proximal wall at location b; in the wall of the annulus
itself, as shown for example at location c; or outside of the disc
1 around the outer periphery of annulus 3, as shown at location d.
Moreover, the device may also be delivered into and around bony
structures associated with the spinal joint, such as for example
shown at locations e, f, g, or h in FIG. 1B. Such positioning may
be accomplished for example by drilling a bore into the vertebral
body from a posterolateral approach through an associated pedicle,
as shown in shadow at location E in FIG. 2, or via a more lateral
approach as shown directly into the body at location F in FIG. 2.
Such positioning and heating within bone structures associated with
the joint may be in particular useful in one regard for treating
bone cancer, destroying nociceptive nerves, stimulating growth or
drug uptake (e.g. low thermal dose applications). Either the
vertebral body itself may the target for heating, or the end plate,
or the disc from such location. A further particular useful
application of this is treatment of osteoporotic back pain.
[0225] As shown in particular in FIG. 2, disc 1 also has a shape
similar to a "kidney"-shape with a concave curvature along a
proximal wall 4 that borders the spinal cord (not shown), as well
as along opposite anterior wall 5. Right and left anterior walls
6,7 are generally characterized by a more acute radius of curvature
than posterior and anterior walls 4,5. As will be further developed
below, each of these uniquely located and anatomical wall regions
may be selectively treated with localized therapeutic ultrasound
energy according to the system and method of the present invention.
In general, intervertebral discs (with respect to the lumbar region
associated with lower back pain) are typically 30 mm wide (e.g.
laterally from right wall 6 to left lateral wall 7, about 20 mm
front-back, e.g. anterior wall 5 to posterior wall 4); and
approximately 10 mm tall, e.g. from end plate 8a to endplate 9a.
Accordingly, the devices herein shown and described are to be
particularly adapted to operate within this general description of
the intended environment of use within intervertebral discs.
[0226] As will be appreciated by the description below of the
various modes of operating the ultrasound treatment system of the
invention, treatment of the annulus fibrosus 2 from within the
nucleus may be achieved via various approaches. In particular,
regions A and B shown in FIG. 2 correspond to right and left
anterior approaches, whereas regions C and D correspond to right
and left posterior-lateral approaches around right and left
vertebral prostheses 8c,8d, respectively
[0227] Multiple ultrasound probe configurations are herein
described for applying thermal (heat) therapy or ultrasound (US)
exposure to tissues within the spine in particular, though other
joints such as knee, hip, etc. are contemplated. It is to be
appreciated that the two specific probe configurations shown and
described provide highly beneficial embodiments, though they are
exemplary and other configurations, improvements, or modifications
according to one of ordinary skill based upon this disclosure in
view of the known art are contemplated.
[0228] In any event, heat produced according to the present
invention at high temperatures and thermal doses can shrink
tissues, change the structural matrix, generate physiological
changes, and/or kill cells within the targeted region of tissue
associated with a disc. Heat at low temperatures and US exposure
can generate permeability changes or changes in the cellular
transport/metabolism that increase effectiveness or deposition of
certain pharmaceutical agents. The heat or US can be delivered with
this technology in a highly controlled fashion to selected tissue
regions in order to exploit these physiological effects for
therapeutic purposes.
[0229] Ultrasound applicators may achieve a degree of precise
targeting or heating control generally not possible with previously
disclosed RF, plasma ion, or heat source techniques. In addition,
ultrasound energy actually penetrates surrounding tissues, rather
than according to other modes (e.g. RF and laser) that heat the
closest tissues the hottest and allowing conduction therefrom in a
diminishing temperature profile curve with distance away. For soft
tissue or bone surfaces within the spine or other joints, high
temperature exposure by use of the invention is used to shrink
tissue impinging on nerves, re-structure and possibly strengthen
mechanical properties of the disc or joint material, destroy
abnormal or undesirable cells or tissue, destroy nerves responsible
for pain, and seal leaks from the disc annulus/nucleus, joint
capsules, etc.
[0230] In particular to disc applications, three general goals are
intended to be achieved according to use of the present invention:
(1) collagen associated with the annulus fibrosus may be
reorganized to reshape the annulus; (2) nerve ingrowth in and
around the annulus or nucleus may be killed; or (3) inflammatory
cells around areas of injury or otherwise penetrating areas in or
around a disc may be killed or ablated. In particular with respect
to causing nerve damage, this may include regions of the annulus
itself, at the endplates, usually is located posteriorly, and
rarely but at times may be within the region of the nucleus itself.
In any event, such nervous ingrowth is typically related to
structural disc damage that is identified e.g. in a discogram and
therefore predicted to be where pain/nerve treatment should be
directed.
[0231] In one particular non-limiting application, either or both
of nerve and inflammatory cells are necrosed by US delivery without
achieving sufficient heating to denature or weaken, or to denature
but not weaken, or to reshape the disc annulus. This is possible
using the devices and methods of the invention herein described at
levels of energy delivery between about 10 to about 300 EM43 deg C.
(e.g. may be from 1 to 60 min at between about 42 deg C. and about
45 deg C.). Where collagen denaturation, modification, or reshaping
is desired, energy delivery from the ultrasound devices herein
described may be from between about 55 deg C. to about 85 deg C.
for between about 10 sec to about 30 min.
[0232] The novel ultrasound applicators and treatment methodologies
herein disclosed allow for the interstitial insertion or
laparoscopic or arthroscopic placement of these applicators within
or upon targeted tissue, in particular with respect to
intervertebral discs.
[0233] One particularly beneficial embodiment of the invention is
shown at ultrasound treatment system 10 in FIGS. 3A-C. This system
10 includes an ultrasound device 11, ultrasound drive system 40,
and intervertebral disc delivery assembly 50.
[0234] Device 11 is shown to couple proximally to an a proximal end
portion (not shown) that generally includes a handle (not shown)
that is adapted to couple to ultrasound drive system 40, which
includes an ultrasound actuator 41. Drive system 40 may be operated
empirically, such that a predetermined delivery of energy is
achieved at a desired level known to produce a desired result. Or,
external therapy monitoring may be employed during treatment, e.g.
MRI, CT, fluoroscopy, X-ray, discogram, or PET in order to control
energy delivery and determine appropriate levels and time duration
for a particular case. These monitoring modalities may be effective
prior to treatment in order to identify the area of concern to be
treated, which may impact the choice of particular device to be
used as provided according to the embodiments herein. Still in a
further alternative embodiment, a treatment feedback device 42,
such as a temperature monitoring system, may be incorporated in a
feedback control system, as shown in FIG. 3A.
[0235] Device 11 is also adapted to be delivered to the desired
location for treatment through delivery assembly 50 and therefore
has a length corresponding to length L of delivery assembly 50 that
is adapted for use in standard access procedures for intervertebral
disc repair. For posterior-lateral approaches, such as for example
in order to invade the nucleus 3 through posterior-lateral sites B
or C shown in FIG. 2, delivery assembly 50 is typically a spinal
needle of about 18 Gauge having a needle bore 53 and sharp pointed
tip 51. Accordingly, the length for device 11 may be about 30 cm
long, with a corresponding outer diameter for device 11 adapted to
fit within such a needle, generally less than about 3 mm, generally
between about 1 and about 3 mm, typically between about 1.2 and 3
mm. However, other sizes may be realized for applications not
requiring delivery through size-limiting delivery assemblies such
as spinal needles, and up to or greater than 5 mm OD is realizable
(e.g. in particular for applications outside of the disc nucleus or
within the annulus). For anterior delivery such as at sites A or B
shown in FIG. 2, delivery assembly 50 may be minimally invasive
delivery device such as an arthroscope or laparoscopic
assembly.
[0236] Device 11 is of a type that contains a linear array of
segmented transducers 16 that are adapted to provide selective,
localized ultrasonic heating via radial, collimated energy delivery
in tissue adjacent to the array. The particular device 11 of the
present invention, including corresponding elements such as
transducers 16 located thereon, are generally smaller and more
flexible than elsewhere previously described for other linear array
transducer devices. In addition, fewer transducers 16 are typically
required for treating the generally smaller regions of the
intervertebral discs as contemplated herein. These substantial
modifications are believed to significantly enhance the
controllability and performance of ultrasound therapy within the
unique (and often dangerous) anatomy of an intervertebral disc.
Otherwise, the basic components for segmented, linear array
transducer device 11 may be similar to those previously described
in U.S. Pat. No. 5,620,479, which has been previously incorporated
by reference above.
[0237] Referring more specifically to FIGS. 3A through 4, an
ultrasound applicator 11 of the invention preferably includes a
cylindrical support member such as a tube, conduit or catheter 12
which may be compatible for adjunctive radiation therapy of the
spine such as according to remote afterloaders and standard
brachytherapy technology. Since catheter 12 includes a coaxial
longitudinal inner lumen 14, a source of radiation, a drug or a
coolant can be inserted therein, as well as guidewires, deflection
members, stylets, etc., according to modified embodiments elsewhere
herein described. One highly beneficial embodiment for example uses
a polyurethane or other similar polymer that is of a soft, low
modulus type according to uses as contemplated herein within the
sensitive intervertebral discs and elsewhere along the spine and
related, highly sensitive nervous tissues. Where direct access to
the desired treatment location is possible without risk of damaging
soft, sensitive tissues around the spine, a more rigid support may
be used, and may even include a thin-walled stainless steel
hypodermic tubing or stiff conduits (though shapes may be important
as further developed below).
[0238] Catheter 12 is coaxially disposed through a plurality of
tubular piezoceramic transducers 16 which are spaced apart and
electrically isolated as shown, thus forming a segmented array of
tubular ultrasound transducers which radiate acoustical energy in
the radial dimension. Transducers 16 may be formed from a variety
of materials as has been previously disclosed. Transducers 16 may
have an outer diameter between about 0.5 to about 6 mm, though with
respect to energy therapy from within the nucleus 3, is more
typically between about 0.5 mm and about 1.5 mm.
[0239] It is preferred that the wall thickness for transducers 16
be substantially uniform in order to generate uniform acoustic
patterns where such energy delivery is desired. Further to
conjunctive radiation therapy (e.g. spinal tumor therapy), the
transducer material is preferably stable when exposed to typical
radiation sources.
[0240] The frequency range of the transducers will vary between
approximately 5-12 MHz depending upon the specific clinical needs,
such as tolerable outer diameter, depth of heating, and inner
catheter outer diameter. Inter-transducer spacing is preferably
approximately 1 mm or less. Those skilled in the art will
appreciate that, while three transducers 16 are shown in FIG. 3A-B,
the number and length of transducers can be varied according to the
overall desired heating length and spatial resolution of the
applicator and depth of penetration desired. This may vary for
example for devices 11 intended to treat along the entire length of
posterior wall 4 of disc annulus 2, versus a lateral wall 6,7
thereof, versus the anterior wall 5. Even the desired length along
a given one of these regions may vary depending upon the particular
patient, or even within a given patient depending upon a particular
region of the spine being treated (e.g. lower discs along the spine
increase in size). Therefore, a kit of devices 11 having varied
lengths and sizes for the array of treatment transducers 16 is
contemplated according to such variances. Transducers 16 are also
shown to be substantially cylindrical for the purpose of
illustration, and which design may be desired where uniform heating
around the circumference of the device 11 is desired. However, as
developed below, the highly selective tissue therapy typically
desired within and around intervertebral discs may require in many
cases more radial selectivity around the device 11, as further
developed below.
[0241] Each transducer 16 is electrically connected to actuator 41
of drive assembly 40, which is typically an RF current supply. This
electrically coupling is achieved via separate pairs of signal
carrying wires 18, such as 4-8 mil silver wire or the like,
soldered directly to the edges of the transducer surface to form
connections 20a,20b. One wire in the pair is connected to the edge
of transducer 16 at its outer surface, while the other is connected
to the edge of transducer 16 at its inner surface, although other
connection points and modalities are also contemplated. Each wire
18 is routed through the center of the transducers between the
outer wall of catheter 12 and the inner wall of the transducer 16,
as can be seen in FIG. 3B, and from there to the connection point
through the spaces between the individual transducer elements.
[0242] In order to ensure that each transducer 16 in the array is
kept centered over catheter 12 while still maintaining flexibility
and not impending transducer vibration, a plurality of spacers 22
are disposed between the transducers and catheter 12. These spacers
22 may take various forms as previously described. For the
particularly smaller designs herein contemplated for spinal
applications, a "spring-ground lead" comprising 3-4 mil stainless
steel wire or the like wound to form a coaxial spring may be placed
between a transducer 16 and an electroded outer surface of inner
catheter 12 where such coil is soldered directly thereto. Such
electroded outer surface may be a common ground for all transducers
16.
[0243] As previously disclosed, transducers 16 are preferably
"air-backed" to thereby produce more energy and more even energy
distribution radially outwardly from device 11. To ensure such
air-backing and that the transducers 16 are electrically and
mechanically isolated, a conventional sealant 24 as previously
described is injected around exposed portions of catheter 12, wires
18, and spacers 22 between transducers 16. Sealant 24 serves
multiple functions in this application, as has been previously
described.
[0244] As a means for monitoring temperature of tissue surrounding
the transducers 16, and to provide for temperature control and
feedback where desired, a plurality of small (e.g. 25.4 .mu.m)
thermocouple sensors 26, such as copper-constantan or
constantan-maganin fine wire junctions, are placed along the outer
surface of each transducer at points which are approximately
one-half of the length of the transducer, and connected to
individual temperature sensing wires 28 which run along one-half of
the length of the transducer 16 and then through the annular space
36 between catheter 12 and the transducers 16. A conventional
acoustically compatible flexible epoxy 30 such as has been
described is then spread over the transducers, thereby embedding
the temperature sensors. The epoxy coated transducers are then
sealed with an ultra thin walled (e.g. about 0.5 to about 3 mil)
tubing 32 that may for example be a heat shrink tubing such as
polyester or the like. Or, the epoxy coated transducers may
otherwise covered, as is known. Heat shrink tubing 32 extends
beyond the area over transducers 16 and covers substantially the
length of device 11. To support tubing 32 in such extended area, a
filler 33 of chosen composition (preferably flexible) is placed
around catheter 12 and between it and tubing 32.
[0245] According to the present embodiments and those elsewhere
herein shown and described, a cooling system may be included, which
has been characterized to increase heating efficiency by about
20-30% versus non-cooled embodiments. In addition, as shown in FIG.
4, standoffs 34 may be used to support transducers 16, which are
preferably flexible and may be an integral part of catheter 12.
[0246] For spinal disc therapies herein contemplated, device 11 is
generally designed to be sufficiently flexible to be delivered in a
substantially straight configuration through delivery device 50,
and thereafter be adapted to assume a configuration appropriate for
delivering energy along a length corresponding to an interface
between the linear array of transducers 16 and the desired region
of tissue to treat. This flexibility may be modified according to
various different modes elsewhere herein described in order to
achieve appropriate positioning and shape conformability used in a
particular case.
[0247] In one particularly beneficial further embodiment shown
variously in FIGS. 5A-B, device 11 is modified from the previous
embodiment of FIGS. 3A-4 such that inner support catheter, similar
to catheter 12 in FIGS. 3A-4, provides a through lumen 13 that is
adapted to slideably receive a guidewire 60 therethrough. Guidewire
60 includes a stiff proximal end portion and either a shaped or
shapeable, more flexible distal end portion 62. According to this
guide wire-based embodiment for system 10, guidewire 60 is adapted
to be placed within the desired region of treatment by steering and
advancing the shaped distal end portion 62 with manipulation of
proximal end portion 61 externally of a patient's body. Device 11
along the array of treatment transducers 16 is sufficiently
flexible to track over guidewire 60 in order to be positioned for
treatment along the desired treatment region. Guidewire 60 may be
of a shape memory type, or may be designed according to many other
previous guidewire disclosures. Moreover, device 11 may be adapted
to receive and track over guidewire 60 over substantially the
length of device 11, also known as "over-the-wire", or may be of a
"rapid exchange" or "monorail"-type wherein guidewire 60 exits
proximally from device 11 at a port along device 11 that is distal
to the most proximal end of device 11.
[0248] FIG. 5A also shows the linear array of transducers 16 to be
of the segmented type, wherein each linear location for a
transducer 16 corresponds to two opposite transducer regions
16a,16b that may be independently or alternatively actuated for
energy delivery. This allows localization of US energy along only
one radial aspect surrounding device 11. Particular designs and
methods incorporating linear array of segmented or partially
activated US transducer regions is disclosed in U.S. Pat. No.
5,733,315 to Burdette et al., which has been previously
incorporated herein above. It is to be appreciated herein that each
transducer segment 16a or 16b is in effect an independently
actuatable transducer, though shown and described as sub-parts of
an overall transducer 16 for illustrative simplicity. Corresponding
transducer regions 16a may be all actuated simultaneously along the
array, without actuating the opposite regions 16b, in order to
ablate along a length only along one radial aspect of device 11
corresponding to actuated regions 16a. Or, the other regions 16b
may be actuated without regions 16a emitting US energy. The device
of FIG. 5A provides this selectivity, which may be useful for
treating different regions of a disc annulus as further discussed
below.
[0249] Various different shaft structures may be appropriate for
housing the corresponding functional components of a device 11
according to the embodiment of FIG. 5A, though one particular
cross-section is shown in FIG. 5B for illustration. Due to the
radially segmented aspect of the transducer array of this
embodiment, the number of actuatable transducer elements
corresponding to a given length of the array is doubled compared to
the earlier embodiment (e.g., each linear region is split into two
radial regions). Therefore, twice the number of electrode leads 18
and thermocouple leads 28 must be housed. The cross-sectioned,
multi-lumen tubing 12A shown in FIG. 5B therefore has a plurality
of surrounding lumens 14 surrounding a central guidewire lumen 13.
This is adapted to give an organized shaft structure for adapting a
proximal pin connector to interface with drive and control system
40, as well as uniform flexibility in multiple planes to enhance
delivery and position control in use.
[0250] Device 11 as illustrated by the FIG. 5A embodiment may
include transducers 16 having many different geometries that may be
customized for a particular energy delivery profile along the
transducer array. Examples include tubular (e.g. FIGS. 3A-4),
sectored tubular (e.g. FIG. 5A), and also as further examples
planar or plate, hemispherical, or portions of cylinders (convex),
depending upon the desired energy delivery for a particular
application. Further to the FIG. 5A embodiment, a distinct radial
region of a transducer location along the array may be rendered
completely inoperative for US delivery, such as for example in
order to protect against delivery into sensitive tissues such as
the spinal chord. In any event, according to the various
embodiments, device 11 may be adapted for linear control of US
exposure or heating via power level adjustments and angular control
of US exposure or heating via directional characteristics of
transducer emitters 16 (e.g., angularly directive with an inactive
zone).
[0251] A further embodiment shown in FIGS. 6A-C further provides
semi-hemispherically shaped transducers 16 that are essentially
flipped to have an opposite radial orientation relative to the
radius of device 11 as compared to otherwise similar transducer
sectors 16a,b in FIG. 5A. More specifically, transducer segments
16a,b each have their concave surfaces 17 facing outwardly from
device 11. This is believed to allow for a focused US signal to be
emitted therefrom to a focal point or depth in relation to device
11 that is controlled by the radius of curvature R for the
corresponding transducer. Such an arrangement may include two
radial sides of linearly spaced transducers, e.g. 16a,b as shown in
FIGS. 6A-B. Or, device 11 may be adapted to house a single such
transducer segment 16, as shown in FIG. 6C, which limits the radial
emission choices to one region around the device periphery, but
increases the design real estate and options for device 11 to house
this unique transducer configuration. In any event, the applicator
device 11 may be repositioned to control angular thermal profile.
Where angular control is of important necessity (such as treatment
immediately adjacent spinal column), device 11 may be designed to
be in particular torqueable from outside the body in order to
rotate the radially focused transmission with the shaft, such as
via use of metal reinforcements or tubular members, or in general
composite shaft designs such as wire or braid reinforcements.
[0252] As elsewhere herein shown and described, device 11 along the
US path from transducer 16 generally includes an ultrasonically
translucent medium, such as a fluid. Acoustic gain and temperature
regulation of applicator surface can help control distance of
heated region and effects from applicator surface. Frequency and
depth of focus can be selected to control heating pattern, and time
can be varied to control heating effects and distribution.
[0253] The segmented array of FIG. 6C can use many different types
of transducers 16, such as for example concave sections of
cylindrical or tubular transducers or spherical or semi-spherically
focused transducers. The outer diameter of the tubes used to form
the transducer shown in FIG. 6C is much larger than the diameter
for device 11 that supports the transducer 16. The transducer
sectors are a small arc; thus, a line focus is produced at depth
over a small arc angle, producing an intense US exposure or heating
pattern which is approximately the same length as the tubular
segment, but very narrow in the angular dimension, which can
beneficially be as narrow as from about 1 to about 10 deg.,
preferably as narrow as from about 1 deg. to about 5 deg. The
length and number of segments can be varied.
[0254] Referring to the particular embodiment shown in FIG. 6D, a
conical or semi-spherical disc-shaped transducer 16 is shown which
focuses energy not only radially along a length of the
corresponding transducer, but instead focuses along the entire
surface of the disc-shape. Therefore such shaped transducer more
precisely and densely focuses and localizes the energy being
delivered into a very small region of tissue. While an array of
such shaped disc transducers 16 is contemplated, the focused
pattern may create energy gaps between adjacent elements--therefore
this design may be more applicable to precise treatment in one area
by one transducer, which may be followed by moving the transducer,
either together with or along the supporting device 11 to another
location to be treated.
[0255] As previously mentioned above, the embodiments of FIG. 6A-D,
in addition to the other embodiments contemplated herein, can
cooled either externally or internally, an can be inserted within
the disc or laparoscopically placed against the target tissue or
directed toward the target tissue. Acoustic gain and temperature
regulation of applicator surface can help control distance of
heated region and effects from applicator surface. Frequency and
depth of focus can be selected to control heating pattern, and time
can be varied to control heating effects and distribution. Other
examples of ultrasound array techniques for adjusting the
selectivity of ultrasound transmission from a device are disclosed
in U.S. Pat. No. 5,391,197, which has been previously incorporated
by reference above; the various embodiments of that disclosure are
contemplated in combination with this disclosure with respect to
segmented array of US transducers, where appropriate and as
modified according to this disclosure according to one of ordinary
skill.
[0256] As elsewhere provided herein, the illustrative embodiments
and procedures have applications in many different soft/hard tissue
sites and body parts where ultrasound exposure, high temperature,
low temperature or combination of effects are desired. Joints in
particular are locations where the present invention is well suited
for providing therapy. However, as stated above of particular
benefit is use of the present invention for treating intervertebral
discs.
[0257] Therefore, one example of a method for treating an
intervertebral disc according to the present invention is provided
according to various sequential modes of use shown in FIGS. 7A-F.
This procedure for the purpose of illustration more specifically
shows posterior-lateral approach to treating a posterior wall of an
intervertebral disc from a location within the nucleus. However,
because selectivity in disc treatment is so very important, clearly
other procedures are contemplated as will be further developed
through other examples below.
[0258] More specifically, according to FIG. 7A a posterior wall 4
of annulus 2 is observed to require thermal treatment, either due
to physical damage to the annulus 2 structure (e.g. herniation), or
otherwise, such as for example innervation with unwanted nervous
tissue causing pain or other inflammatory cells (which may be
directly or indirectly related to disc damage such as herniation).
As shown in FIG. 7A, a sharp, pointed tip 51 of a spinal needle 50
is used in a posterior-lateral approach to puncture through the
posterior-lateral region of the wall of annulus 2. This gives
lumenal access through needle bore 53 into the nucleus 3 for
ultrasound probe delivery.
[0259] As shown in FIG. 7B, a guidewire 60 having a steerable
distal tip 62 is then advanced through needle bore 53 and into
nucleus 3. It is contemplated that guidewire 60 may be used for
many purposes within the nucleus 3, or otherwise in or around disc
1. However, one particularly beneficial use is shown, wherein
guidewire is tracked along proximal wall 4, and then further around
the more severe radius along lateral wall 7. This gives a rail
along proximal wall 4 along which a highly flexible device 11 may
track for ablation there. This is shown in FIG. 7C, wherein
ultrasound transducers 16 are of length, size, and location along
device 11 such that they are positioned over guidewire 60 to
coincide with the area along posterior wall 4 to be treated.
According to the embodiment shown in FIG. 7D, only one radial
aspect of device 11 is actuated for US emission and treatment,
which is shown to be transducer segments 16b in an array on one
radial aspect of device 11 interfaced with or facing proximal wall
4. Thus US energy is transmitted into wall 4 to treat that region
without substantial treatment elsewhere.
[0260] After treatment, other regions may be treated by further
manipulating guidewire 60 and/or device 11 within the nucleus 3 (or
outside of annulus if desired). Once treatment within the annulus
is completed, device 11 may be withdrawn. In the embodiments shown
in FIGS. 7E-F, the ultrasound transducers 16 may be used to assist
in closing the wound formed at entry site C through annulus, such
as by elevating the temperature in that area sufficient to cause
collagen shrinkage to aid in closing that aperture, as shown in
FIG. 7F for example. In this application, the entire circumference
of device 11 may be activated for US emission, or if only a radial
region is adapted for such emission, it may be rotated to heat all
aspects of the wound aperture to seal it. In addition, a sealant
may be administered through the distal end of device 11 to close
the wound, such as at introduction region C, either instead of or
in conjunction with ultrasonic emission from device 11.
[0261] Other regions of disc 1 may also require localized,
selective therapy with US, and the present invention allows for
highly specialized treatments in the various regions. FIGS. 8 and 9
for example show use of device 11 from the right posterior-lateral
approach through site C shown in FIGS. 7A-F, but for treating
anterior wall 5 and left lateral wall 7 regions, respectively. For
the embodiments shown wherein device 11 is highly flexible for
sufficient trackability over guidewire 60, the same device may be
used for treating the very different areas shown in FIGS. 7A-F,
FIG. 8 (anterior wall), and FIG. 9 (left lateral wall). However, as
shown in comparing FIGS. 7A-F, 8, and 9, different radial regions
of device 11 may be activated to treat the respective interfacing
wall (where angular specificity is provided, which may not be
required though often preferred). In particular, the guidewire
trackability of the present embodiments provides for highly
beneficial flexibility between the ability to treat these very
different segments, in particular in view of the generally more
significant curvature associated with the anatomy around the
lateral wall regions as shown at radius R for lateral wall region 7
shown in FIG. 9.
[0262] For the purpose of further illustration, FIG. 10 shows a
device 11 according to the invention used to treat a posterior wall
4 of disc 1, but according to an anterior approach through a region
of anterior wall 5 adjacent to left lateral wall 7. Again, this may
for example be a similar device as that shown and described with
respect to FIGS. 7A-9.
[0263] The devices and methods of the invention are also adapted
for use in treating spinal disorders from outside of the annulus 2,
though preferably still from an invasive location within the
patient's body in order to provide the necessary and desired
amounts of energy at only the highly localized, target locations.
For example, FIG. 11 shows a right posterior-lateral approach to
treat a region of annulus 2 from outside of disc 1. Because of
surrounding tissues, it is highly desired (though not always
required), to deliver only highly selective, directed US energy
into only the region of annulus 2 being treated. In particular,
truncal nerves often extend along such areas, as well as the spinal
cord being located not to far away from such region. Therefore, a
controllable, selective array of transducers as shown at
transducers 16a radiates only toward the disc annulus 2, whereas
the opposite side of device 11 is non-emissive. In fact, this
opposite side may be selectively cooled to prevent from thermal
heating of the area, and may include sensors to monitor such
temperature around that area opposite the active US treatment zone,
such as for example at thermocouples 27 shown in FIG. 11.
[0264] For the purpose of further illustration, FIG. 12 also shows
US treatment from outside of a disc 1 according to the invention,
but according to an anterior approach. FIG. 13 shows still another
exterior treatment modality, however this particular location along
the posterior wall 4 is particularly sensitive as the spinal cord
is located immediately adjacent device 11 opposite transducers 16a
and must not be harmed. Therefore, not only the radial emission of
energy (either US or thermal heat) from device 11 must be insulated
from that radial region corresponding to the spinal cord.
[0265] Though guidewire tracking mechanisms provide the
illustrative embodiments for positioning in FIGS. 7A-13, other
embodiments are contemplated. Moreover, positioning of a device 11
may include simultaneous or sequential positioning of thermometry
probes for monitoring of sensitive tissue areas, etc.
[0266] A pre-shaped or otherwise directional introduction/delivery
device may assist to point a device 11 to a localized area for
treatment, such as shown for example in shadow in FIG. 3A for
shaped tip 51 for delivery device 50. Such directionality from the
delivery device 50 may be provided in addition to, or in the
alternative to, providing guidewire tracking of device 11 or other
additional positioning modes herein discussed. In addition, other
positioning control mechanisms may be incorporated into device 11
itself as follows.
[0267] One particular deflectable tip design is shown for device 11
in FIG. 14A-B. According to this embodiment, the region of device
11 that includes the array of transducers 16 is deflectable to take
a variety of shapes, such as shown in right and left deflection
modes around a radius r in FIG. 14B. Such deflection may be
achieved using conventional deflection mechanisms, such as for
example using an arrangement of one or more pull-wires integrated
into the tip region so that tension causes catheter deflection. In
addition, such deflection may be achieved instead of along a length
of an arc, around a pivot point, as shown in FIG. 14C. Such may be
achieved in order to achieve different angles for surgical
approaches into the desired treatment areas, such as in or around
intervertebral discs. The transducer elements may be along a
deflectable segment that is either round, or may be more planar as
desired.
[0268] Pre-shaped distal regions for device 11 may also provide for
desired treatment of highly unique anatomies. A kit of devices,
each having a particular shape is contemplated. Such shapes may be
integrated in procedures with or without conjunctively using
guidewire tracking. For example, FIG. 15A shows a pre-shaped distal
end for device 11 having a simple distal curve around radius r. The
transducers 16 are around the outer radius of such shaped end, and
therefore this shape and orientation is suitable for example for
treating an anterior wall 5 from within a disc 1 via a
posterior-lateral approach, such as for example according to FIG.
8. A similar shaped end is shown in FIG. 15B, but the transducers
16 are instead on the inside radius r. This is more suitable for
posterior-lateral approach with posterior wall treatment, such as
for example in FIGS. 7A-F.
[0269] A further beneficial shape and orientation is shown in FIG.
16. Here, an acute bend shown around radius r2 is adapted to
correspond to the more drastically rounded lateral wall regions 6,7
of a disc annulus 2 with an energy emission region on the outside
of that bend. An additional bend region may be highly beneficial,
though not always required, shown proximally of the distal bend
around radius r2 and having a less drastic bend, in the opposite
direction of r2, shown around radius r2. This configuration is
highly beneficial for treating lateral wall regions 6,7 from a
posterior-lateral approach (e.g. FIG. 9), though may be used in the
same configuration or slightly modified for anterior approach.
[0270] Though ultrasound transducers and their many benefits for
invasive energy delivery into tissues has been extensively herein
described, various of the embodiments further contemplate use with
other energy sources or treatment modalities, either instead of or
in conjunction with ultrasound. Thus, treatment region 16 in FIG.
16 does not specifically show individual ultrasound segments as in
the other figures, for the purpose of illustrating other energy
sources or treatment modalities that my be incorporated thereon and
still gain the benefit of the unique shape provided for inner disc
ablation according to that figure. Other sources such as electrical
(e.g. RF), light (e.g. laser), microwave, or plasma ion may be
used. In addition, cryotherapy or chemical delivery may be achieved
along the regions variously designated as "transducer 16", which
may be accompanied by other modifications corresponding therewith,
without departing from the scope contemplated by the
embodiments.
[0271] According to the various deflectable or pre-shaped modes, or
modes where energy delivery is limited to only one side of the
device, the device 11 is preferably torqueable, such as by
integrating into the shaft design a composite of braided fibers or
other stiff members. This allows for more precise control of the
distal tip regions as it deflects or takes its shape along a plane
within the desired area of the body to treat.
[0272] The various embodiments for device 11 above may be adapted
to incorporate active cooling, such as circulating cooling fluids
within or around active energy emitting elements such as
transducers 16 variously shown or described. Such cooling may be
integrated into the particular device 11, or may be achieved by
interfacing the particular device 11 inside of or otherwise with
another device.
[0273] FIG. 17A shows for example device 11 within an outer jacket
15 that may or may not be distendable, as shown in shadow at 15'.
Outer jacket 15 is adapted to circulate fluids around transducers
16 and therefore is interfaced with a circulation pump 70 in an
overall system. In an alternative embodiment sharing many common
features as FIG. 17A, the device 11 shown in FIG. 17A provides for
the cooling fluid to be delivered through an interior passageway of
the interior ultrasound device, out the distal tip thereof within
the outer jacket 15, and back over the outer surface of the
interior device including the transducers 16.
[0274] In either the FIG. 17A or 17B embodiments, device 11 may be
fixed within outer jacket 15, or may be moveable relative to outer
jacket 15, or visa versa. Fluids provided in an outer jacket
surrounding transducers 16 according to the invention may also be
used beneficially for ultrasound coupling to intended tissues to be
treated. This may be in addition to or instead of being used for
cooling. In particular, such coupling fluids may be provided in a
jacket 15 that is conformable, such that irregular surfaces to be
treated receive uniform energy coupling from the assembly. Or,
pre-shaped, and symmetric or asymmetric shapes, may be provided as
appropriate to provide such coupling. Ultrasound coupling may be
further achieved by providing a non-liquid coupling member as a
stand-off over a transducer in order to couple that transducer to
the tissue--such as for example a sonolucent coupling gel pad,
etc.
[0275] In addition to the various designs for device 11 described
above for achieving positioning, e.g. guidewire tracking,
pre-shaped, or deflectable, other mechanisms may also be
incorporated for accurate positioning. For example, stiff or
flexible distendable member(s) may be incorporated on device 11,
e.g. a balloon or expandable cage, that distends to a
predetermined-shaped (or just generally distends). This may help
positioning, such as for example where the nucleus 3 is void of
pulposus in order to position the transducers 16 within a balloon
at a desired location within the annulus 2. In addition to
positioning, such a member may also be used to aid coupling, tissue
deforming, and tissue repositioning during a treatment
procedure.
[0276] As previously discussed, the intervertebral disc
applications of ultrasound herein contemplated require high
selectivity for US or otherwise thermal therapy due to the presence
of highly sensitive, non-targeted tissues in close proximity (e.g.
spinal cord and other nerves). Therefore, though heat conduction
may not be the intended mode of therapy with transducers 16, their
concomitant heating during US sonic wave delivery may cause
unwanted damage in either the targeted or non-targeted tissues.
Accordingly, cooled lumens or balloons over the transducers may be
employed to protect such tissues from such heat, or directivity of
the ultrasound per the embodiments herein described my adequately
protect sensitive non-targeted tissue. In the case of an active
cooling mechanism, it is to be appreciated that such mechanism may
be integrated directly onto device 11 that carries the transducers
16. Or, a separate co-operating device such as an outer sleeve
carrying cooling fluids may be used. Such cooling chamber may be on
the side of the transducer delivering the targeted US wave, in
which case fluid in the chamber must be substantially sonolucent
for efficient energy delivery. In the event the cooling is intended
to protect a "back side" of the device only, other fluids may be
used.
[0277] Applicators, such as the various embodiments shown for
device 11 among the FIGS., and insertion tools, e.g. delivery
device 50, may be adapted to be MR compatible for real time
monitoring of a particular procedure. Also other imaging modalities
may be used instead, or in conjunction with one another, in order
to control and optimize the US treatment procedure, including for
example for monitoring positioning, temperature, lesion assessment,
coagulation, or otherwise changes in tissue structures related to
the treatment (e.g. targeted tissue to be heated or adjacent
tissues to monitor safety, such as regions of concern to preserve
nerves associated with the spinal chord). In fact, US itself is an
energy source that has been widely used for acoustic imaging in and
around internal body structures. It is contemplated that imaging US
devices may be incorporated into a device 11 directly, or
indirectly incorporated as a separate cooperating device in system
10, and further that the US treatment transducers 16 herein shown
and described may be operated in imaging modes before, during, or
after thermal US therapy is performed with those same transducers
16.
[0278] In addition to the spine, the device systems and methods
according to the embodiments may be used in other regions of the
body, in particular other joints. Examples of such regions include
knee, ankle, hip, shoulder, elbow, wrist, knuckles, spinal
processes, etc. In such case, further modifications from the
illustrative embodiments herein provided may be made in order to
accommodate the unique anatomy and target tissue regions, without
departing from the spirit and scope of the present invention.
[0279] While the device systems and methods have been herein
described with respect to treating tissue via US exposure in order
to provide hyperthermia effects, other non-thermal results may also
be intended, either in conjunction with hyperthermia or in the
alternative to. For example, drug activation and or enhanced drug
delivery, such as for example via enhanced dispersion or cellular
permeability or uptake, may be achieved by delivering certain
specific therapeutic dosing of US energy, as has been well studied
and characterized in the art. Such methods may for example aid in
the treatment for example of arthritis in joints, etc.
[0280] The invention as described herein according to the
particular embodiments is highly beneficial for treatment of the
body, in particular joints, and in particular the spine. In
general, these devices and methods are adapted for such treatment
invasively from within the body. However, external applications are
contemplated as well. In addition, treating living bodies according
to the invention is believed to provide a highly therapeutic result
for improved living. Nevertheless, use of the devices and methods
as described herein are also contemplated for conducting scientific
studies, in particular with respect to characterizing tissues in
their relation to applied energy. Therefore, "therapeutic"
applications may include those sufficient to induce a measurable
change in tissue structure or function, whether living or
post-mortem, prophylactic or ameliorative, research or clinical
applications.
Example: External Directional Ultrasound Thermal Therapy of Cadaver
Spinal Discs
[0281] FIG. 18A shows an X-ray photograph of a cadaver
intervertebral disc during invasive ultrasound treatment with a
device and method according to the invention as follows.
Temperature monitoring measurements are shown as overlay dotted
lines and numbers over the X-ray.
[0282] An ultrasound probe was provided as follows. Two PZT
ultrasound transducers were provided on a hypotube, each being 1.5
mm OD.times.10 mm long (0.012'' wall thickness), and being spaced
by about 1 mm. The ultrasound probe was inserted within a 13-g
Brachytherapy Implant Catheter having a 2.4 mm O.D., which is
commercially available from Best Industries. Water at room
temperature was circulated through the outer catheter and over the
transducers at about 40 ml/min during ultrasound transmission. The
assembly of the outer catheter with inner transducers and probe was
inserted laterally into a cadaver disc along the border of the
nucleus pulposus and posterior wall of the annulus fibrosus. The
approximate location of the transducers is shown in two rectangles
in FIG. 18A. Thermocouple probes were inserted into the disc as
shown in the X-ray, and with measurement locations reflected by the
sample measurements in the overlay. The above test sample and
instrumentation was placed within a 37 deg C. water bath during
testing. Each transducer was run at approximately 10 W power,
wherein temperature numbers shown in FIG. 18A generally represent
temperatures at substantially steady state after actuating the
transducers. Heat generated by the ultrasound probe was sufficient
to cause therapeutic effects in surrounding tissues of the annulus
and nucleus.
[0283] Another similar study was performed using ultrasound to heat
a post-mortem intervertebral cadaver disc using a curvilinear
ultrasound applicator directly coupled to tissue at 5.4 MHz and 10
W power. A temperature vs. time graph of the results at varied
depths from the transducer surface are shown in FIG. 18B, which
shows among other information that temperatures reached 70-85
degrees within 7 mm from the disc treatment surface and within 5
minutes of treatment..
[0284] As shown in the graph of FIG. 18B, the elevated temperature
achieved at 1 mm from the ultrasound transducer reached: over 45
degrees C. within 90 seconds (11/2 minutes); over 70 degrees C.
within 120 seconds (2 minutes); over 75 degrees C. in nearly 120
seconds; over 80 degrees C. within 180 seconds (3 minutes); and
over 85 degrees C. by about 300 seconds (5 minutes).
[0285] Temperatures at 4 mm depth from the transducer reached: 45
degrees C. in less than 120 seconds (2 minutes); 55 degrees in
close to about 120 seconds; 65 degrees C. within 150 seconds (21/2
minutes); over 70 degrees C. within less than 210 seconds (31/2
minutes); and over 75 degrees C. and still rising by about 240
seconds (4 minutes).
[0286] Temperatures at 7 mm depth from the transducer reached: 45
degrees C. by about 120 seconds (2 minutes); 55 degrees C. by about
150 seconds (21/2 minutes); 60 degrees C. in nearly 180 seconds (3
minutes); 65 degrees C. within 240 seconds (4 minutes); and 70
degrees C. within 300 seconds (5 minutes).
[0287] Temperatures at 10 mm depth from the transducer reached: 45
degrees C. in less than 150 seconds (21/2 minutes); 55 degrees C.
in less than about 210 seconds (31/2 minutes); over 60 degrees C.
in less than 270 seconds (41/2 minutes); and slightly less than
about 65 degrees C. by 300 seconds (5 minutes).
[0288] In another regard, the graph in FIG. 18B also shows that
temperatures above 45 degrees C. were reached within 90 seconds at
1 mm, 120 seconds at 4 mm and 7 mm, and 150 seconds at 10 mm depths
from the transducer. Similarly, temperatures of at least 55 degrees
C. were reached within about 120 seconds at 1 mm and 4 mm, 150
seconds at 7 mm, and 210 seconds at 10 mm depths. Temperatures of
at least 65 degrees C. were reached within less than 120 seconds at
1 mm, 150 seconds at 4 mm, 240 seconds at 7 mm depths. Still
further, temperatures above 70 degrees C. were reached within 120
seconds at 1 mm, 210 seconds at 4 mm, and 300 seconds at 7 mm
depths. Even further heating to above 75 degrees C. were reached
within close to 120 seconds at 1 mm, and 240 seconds at 4 mm
depths.
[0289] Further observation of FIG. 18B in the time domain, in less
than 150 seconds temperatures at up to 7 mm depth from the
transducer reached at least 55 degrees C. Within about 210 seconds
temperatures in tissue as deep as 4 mm deep reached over 70 degrees
C., up to 7 mm deep reached at least 60 degrees C., and up to 10 mm
deep reached over 55 degrees C. Within 270 seconds, temperatures 4
mm deep reached over 75 degrees C., up to 7 mm deep reached over 65
degrees C., and up to 10 mm deep reached over 60 degrees C. In
still a further regard, by 300 seconds temperatures up to 7 mm deep
reached at least 70 degrees C., and up to 10 mm deep reached almost
65 degrees C.
[0290] Upon further comparison of temperatures vs. depth according
to the FIG. 18B graph: temperatures over 60 degrees C. (and for the
most part up to 65 degrees or more) were achievable up to 10 mm
deep; temperatures up to at least 70 degrees C. were achieved up to
7 mm deep; temperatures over 75 degrees were achieved up to at
least 4 mm deep; and at 1 mm depth temperatures of over 80 degrees
and even 85 degrees were observed.
[0291] As will be further developed below and elsewhere herein,
such elevated heating, including at tissues as deep as 4 mm, 7 mm,
and in some regards even 10 mm, is a highly beneficial aspect of
the present invention. For example, other more conventional
intervertebral disc heating devices, in particular the "IDTT"
device elsewhere herein described, have been observed to be limited
as to the extent and depth of heating possible.
[0292] For example, according to at least one study observing the
heating effects of the "IDTT" radiofrequency electrical heating
device (elsewhere herein described) also on cadaveric lumbar spine
disc samples, the following observations were made. During intended
modes of use for internal disc heating, and over treatment times of
17 minutes (1020 seconds), the IDTT devices tested were able to
heat only the closest 1-2 mm of intervertebral disc tissue to
temperatures just barely exceeding 60 degrees, with no tissue of 1
mm depth or greater exceeding 65 degrees C. despite reaching 90
degrees C. on the probe itself. Moreover, only tissues within a 7
mm radius of the heating probe exceeded 48 degrees C. during the 17
minute treatment time. Still further thermal dosing was limited
such that the maximum predicted depth for damaging nociceptive
fibers infiltrating the discs was believed to be only within a 6-7
mm radius.
[0293] Accordingly, substantial benefit is gained by using the
ultrasound treatment device of the present invention to the extent
depth of heating and heating to substantial temperatures and within
reasonable times is desired.
Example: Thermal Therapy of Pre-Stressed Spinal Joints
[0294] This Example provides an abstract summary, introduction,
methods, results, and conclusions with respect to a certain group
of studies performed to evaluate heat-induced changes observed in
intervertebral discs, related structures such as in particular
annulus fibrosus, and the related biomechanics, in particular with
respect to "intact" discs, as follows.
[0295] 1. Abstract.
[0296] The intervertebral disc is considered a principal pain
generator for a substantial number of patients with low back pain.
Thermal therapy has been disclosed to have a healing effect on
other collagenous tissues, and has been incorporated into various
minimally invasive treatments intended to treat back pain. Since
the therapeutic mechanisms of thermal therapy have generally been
previously unknown, proper dosage and patient selection has been
difficult. Thermal therapy in one regard has been disclosed to
acutely kill cells and denature and de-innervate tissue, leading to
a healing response.
[0297] The purpose of this study was to quantify the acute
biomechanical changes to the intact annulus fibrosus after
treatment at a range of thermal exposures and to correlate these
results with the denaturation of annular tissue. Intact annulus
fibrosus from porcine lumbar spines was tested ex vivo. Changes in
biomechanical properties, microstructure, denaturation temperature,
and enthalpy of denaturation before and after hydrothermal heat
treatment (at 37, 50, 60, 65, 70, 75, 80, and 85.degree. C.) were
determined. Shrinkage of excised annular tissue was also measured
after treatment at 85.degree. C. Significant biomechanical changes
in the intact annulus were observed after treatment at 70.degree.
C. and above, but the effects were much smaller in magnitude than
those observed in excised tissues. Histological and mDSC data
indicated that denaturation had occurred in intact annular tissue
treated to 85.degree. C. for 15 minutes, though such effect was
observed to be slight. It is believed based on observations made
that constraints imposed on the tissue by the joint structure
retard changes in properties. These findings have implications for
dosing regimens when thermally treating disc tissue.
[0298] 2. Introduction.
[0299] The goals of this study were to: 1) quantify acute
biomechanical changes to the intact annulus fibrosus induced by a
broad range of ex vivo thermal exposures; and 2) to correlate these
results with denaturation of annular tissue using modulated
differential scanning calorimetry (mDSC) and histological data.
[0300] 3. Methods.
[0301] a. Mechanical Testing.
[0302] Forty-one spinal motion segments (18 L.sub.12, 19 L.sub.34,
19 L.sub.56) consisting of the intervertebral disc (IVD) and each
adjacent vertebral body were cut from 22 fresh frozen porcine
lumbar spines (domestic farm pig weight range: 115-135 lbs).
Muscular and ligamentous structures, facet joints, transverse
processes, and posterior elements were dissected from the vertebral
bodies to isolate the disc. Saline-soaked gauze was wrapped around
the discs during preparation to minimize dehydration. Next, the
nucleus was depressurized by drilling holes first through the
vertebral bodies to the center of the nucleus in the
superior-inferior direction, and then from the anterior faces of
the vertebral bodies to the central hole. Plastic tubing was
inserted into the anterior openings and affixed with cyanoacrylate.
The vertebral bodies, anchored with 2.5 mm threaded rod, were
embedded into fixation cups using polymethylmethacrylate (PMMA). An
alignment bar mated with grooves in the fixation cups to ensure
that the plane of the disc remained normal to the vertical loading
axis. X-rays (Faxitron Cabinet X-Ray System, Hewlett-Packard,
McMinnville, Oreg.) were taken of the specimens in the
dorsal-ventral plane after equilibration in a 37.degree. C. saline
bath. Disc heights were determined by averaging three caliper
readings from the dorsal-ventral x-rays.
[0303] Specimens were secured in fixation cups, mounted into a
hydraulic materials testing machine (MTS Bionix 858, Eden Prairie,
Minn.), and placed into a temperature controlled 0.15M saline bath
at 37.degree. C. to equilibrate. Saline at bath temperature was
also circulated through the center of the discs via the tubing
attached to the vertebral bodies; this allowed for a more rapid and
uniform heat distribution within the annulus.
[0304] Temperatures were measured using two stainless steel
thermocouple needle probes, one placed in the bath, and one
inserted approximately halfway into the anterior annular wall.
These fine-needle temperature probes were fabricated in-house using
25 micron constantan-manganin thermocouple junctions embedded
within a 30 gauge (0.30 mm OD) needle. Superior-inferior x-rays
were used to verify proper placement of the annular temperature
probe.
[0305] The testing protocol consisted of a 20-minute thermal
equilibration at 37.degree. C., a 15-minute heat treatment, and
another 20-minute equilibration at 37.degree. C. Fast temperature
changes were facilitated by exchanging the saline in the bath with
that in a reservoir heated to the desired temperature and then
maintained with temperature-controlled circulation. The target
temperature (to within 7%) was reached within 5 minutes of
exchanging the saline. During the equilibrations, the disc stress
was maintained at 0 kPa.
[0306] Mechanical testing was performed at 37.degree. C. just prior
to heat treatment and again subsequent to heat treatment and
re-equilibration at 37.degree. C. Testing consisted of nine
preconditioning cycles in axial tension-compression (-25 to +150N
at 0.25 Hz), followed by one testing cycle to the same limits. The
applied load was measured using a precision force transducer (Load
Cell 662, MTS, Eden Prairie, Minn.), and the deformation of the
disc was assumed to be the change in distance between fixtures,
measured using the test system LVDT. Data was collected every 0.01
seconds during mechanical testing and every 15 seconds during heat
treatment and equilibration. Heat treatment was to one of the
following temperatures: 37 (Controls), 50, 60, 65, 70, 75, 80, or
85.degree. C. Five specimens were tested at each treatment
temperature except for the 60.degree. C. group that had six
specimens.
[0307] After testing, specimens were removed and the discs were cut
in the transverse plane and scanned at a resolution of 600 dpi
(CanoScan N656U, Canon, Inc., Costa Mesa, Calif.). Annulus areas
were measured using imaging software (Scion Image, v. 4.0.2B,
Frederick, Md.).
[0308] Two additional experiments were conducted to allow us to
explore the limits of annular thermal response. In the first study,
a specimen was prepared as described above and treated at
85.degree. C. until the thermal contraction stabilized (within 0.01
mm). For the second study, sections of anterolateral annulus were
excised from five lumbar discs (2 L.sub.23, 3 L.sub.45) from four
different spines and treated at 85.degree. C. using the same
heating protocol as above. X-rays were taken before and after
treatment, and changes in circumferential and radial dimensions
after heat treatment were measured using digital calipers.
[0309] b. Microstructure
[0310] Tissue samples were excised from 37.degree. C. and
85.degree. C. mechanical test specimens, and from an excised
specimen treated at 85.degree. C. Samples were embedded in
paraffin, sectioned in the circumferential plane at 6 microns, and
stained with HBQ (Hall, 1986). The sections were imaged on a Nikon
Eclipse E800 microscope (Nikon, Melville, N.Y.) under bright field
to examine tissue structure, and under polarized light to assess
collagen birefringence.
[0311] c. Modulated Differential Scanning Calorimetry
[0312] Traditional DSC measures the combined effects of reversible
and nonreversible heat flow, but the two components can be measured
separately if the modulated DSC (mDSC) technique is used. mDSC was
performed on samples of anterolateral annulus fibrosus removed from
fifteen previously treated specimens (Cambridge Polymer Group,
Somerville, Mass.). Punches (approximately 10 mg) were removed from
the control (37.degree. C.) mechanical test specimens (n=5),
mechanical test specimens treated at 85.degree. C. (n=5), and from
the excised annular specimens treated at 85.degree. C. (n=5). Each
sample was placed in 0.1% NaCl solution for 20 minutes, blotted,
weighed, and crimped into an aluminum anodized hermetic DSC pan.
Samples were placed into a Q1000 differential scanning calorimeter
(TA Instruments, New Castle, Del.), equilibrated at 55.degree. C.,
and then ramped from 55.degree. C. to 95.degree. C. at 0.5.degree.
C./min. Using an empty pan as a reference, total enthalpy of
denaturation (.DELTA.H) and the temperature corresponding to the
nonreversible endothermic peak (T.sub.m) were recorded. Following
the mDSC procedure, samples were vacuum dehydrated, and the
fractional dry mass (ratio of dry weight to wet weight) was
recorded.
[0313] 4. Data Analysis
[0314] The force and displacement data from the mechanical tests
were converted to stress and strain. The stress and strain data for
each mechanical test were then fit to a high-order polynomial, and
an equation for the specimen tangent modulus was calculated as the
derivative of this polynomial. A plot of modulus vs. applied stress
was constructed. The stress at the inflection point--the transition
between tension and compression--was the stress at which the second
derivative of the polynomial was zero. The reference configuration
was defined as the stress and strain at the pre-treatment
inflection point. Three biomechanical parameters were calculated
from the modulus vs. applied stress curves to quantify heat-induced
changes in the mechanical response (FIG. 19): the change in modulus
at the inflection point (MI), the change in modulus at 150 kPa
(M150), and the change in residual stress at inflection point
(RSI). The percent change in hysteresis (HYST %) was calculated
from the pre- and post-treatment load-displacement curves. The
change in the modulus at the inflection point is a measure of the
increase or decrease in the stability of the joint, while the
change in the modulus at 150 kPa is an indication of how well the
joint will withstand physiologic loading. The percent change in
strain at 0 stress (E0%) was used to quantify axial shrinkage of
the tissue.
[0315] Differences in each parameter with treatment temperature
were compared using a one-way analysis of variance (ANOVA).
Post-hoc multiple pairwise comparison tests (Fisher's Least
Significant Difference) were performed to determine differences
between treatment groups with a significance of p<0.05.
[0316] 5. Results.
[0317] a. Mechanical Testing
[0318] FIG. 21 includes various graphs representing observed
biomechanical parameters after varied heat treatments according to
the present study as follows: graph (a) represents change in
modulus at the inflection point (MI); graph (b) represents change
in modulus at 150 kPa (M150), graph (c) represents percent change
in strain at 0 stress (E0%), graph (d) represents change in
residual stress at the inflection point (RSI), and graph (e) shows
percent change in hysteresis (HYST %). Further to the graphs in
FIG. 21, the reference letter "X" is used to designate where data
is significantly different from 37.degree. C. group, p<0.05;
whereas the symbol "+" is used to designate where data is observed
to be significantly different from the 85.degree. C. group,
p<0.05.
[0319] Significant differences between the control group and the
heat-treated specimens were observed at temperatures of 70.degree.
C. and above (FIGS. 19, 20, 21). The variation increased with
increasing treatment temperature. No significant changes were
observed between the control group and the 50 and 60.degree. C.
groups, and the 65.degree. C. treatment group showed a change only
in the hysteresis parameter. The modulus at the inflection point
(MI) increased by 152 kPa after treatment at 70.degree. C.
(p<0.05), and continued to increase with increasing heat
treatment: the 85.degree. C. group, with an average increase of 343
kPa after treatment as shown in FIG. 19), and was significantly
different from both the control group (p<0.001) and the
70.degree. C. group (p<0.05) according to the graph in FIG. 21a.
The modulus at 150 kPa (M150) significantly decreased for groups
treated at 70.degree. C. and up, but did not continue to decrease
with increasing treatment temperature; the decrease was 17% at
70.degree. C. and 18% at 85.degree. C. as shown in the graphs of
FIGS. 19, 21b.
[0320] Relative to the control group, significant axial shrinkage
(E0%) was first observed at the 70.degree. C. treatment
temperature. There was no significant difference observed in this
particular experiment between the axial shrinkage after treatment
at 70 and 85.degree. C., although there was a trend towards
continued increase (p<0.10) according to the graphical results
in FIG. 21c. The change in the residual stress at the inflection
point (RSI) after heat treatment was significantly larger for
groups treated at temperatures of 75.degree. C. and up with a trend
towards increasing stress with increasing treatment temperature (75
vs. 85.degree. C., p=0.084), as shown in the graph of FIG. 21d. A
36% percent increase in hysteresis (HYST %) was observed for the
65.degree. C. group; this was significantly larger than that of the
control group (p<0.05) per the FIG. 21e graph.
[0321] The disc heights of the specimen exposed to long heat
treatment time at 85.degree. C. stabilized after approximately 2.5
hours. As a result of treatment, M150 decreased 47%, MI increased
625 kPa, RSI was 47.3 kPa, and hysteresis increased 98%. The
percent change in strain at 0 stress (E0%) was 22.5%.
[0322] Heat treatment of the excised annulus at 85.degree. C.
resulted in shrinkage of 45.1%.+-.5.5% in the circumferential
direction and expansion of 56.9%.+-.25.4% in the radial direction.
The shrinkage was accompanied by a color change from white to
translucent, a finding that which was not present in our whole-disc
samples.
[0323] b. Microstructure
[0324] The structure of the annular collagen, as indicated by its
birefringence under polarized light microscopy, varied with heat
treatment (FIGS. 22a-f). The structure of the excised sample
treated at 85.degree. C. changed dramatically relative to that of
the control specimen: the 37.degree. C. specimen was strongly
birefringent under polarized light as shown in FIG. 22b, while the
85.degree. C. excised specimen showed no birefringence as shown in
FIG. 22f. The 85.degree. C. mechanical test specimen appeared less
birefringent than the control, as shown in FIG. 22d. Bright light
microscopy revealed a structure consistent with that observed under
polarized light. The heated excised specimen exhibited a homogenous
morphology, as shown in FIG. 22e, with a complete loss of the
original structure relative to the control shown in FIG. 22a.
Tissue organization decreased, but was not absent, in the
85.degree. C. mechanical test specimen shown in FIG. 22c.
[0325] c. Modulated Differential Scanning calorimetry
[0326] The excised specimens did not exhibit an endothermic peak,
and thus, values for T.sub.m and .DELTA.H were not calculable. Both
intact groups exhibited a full and clear endothermic denaturation
event. There were no significant differences in T.sub.m and
.DELTA.H between the intact (37.degree. C. & 85.degree. C.)
specimens. T.sub.m for the control group and the 85.degree. C.
intact group were 65.4.+-.1.5.degree. C. and 65.3.+-.0.9.degree. C.
respectively, while .DELTA.H was 11.5.+-.2.4 W/g and 12.2.+-.4.6
W/g. The fractional dry mass of the 85.degree. C. intact group
(0.33.+-.0.03) and the 85.degree. C. excised group (0.37.+-.0.043)
were both significantly higher than the control group
(0.26.+-.0.04; p<0.05 and p<0.01, respectively).
[0327] 6. Discussion
[0328] In this study we examined the acute biomechanical effects of
thermal treatment on the annulus fibrosus. The data demonstrate
that treatment for 15 minutes at 70.degree. C. or above is required
to produce statistically significant biomechanical modification of
the intact motion segment ex vivo. Heat treatments of 70.degree. C.
and higher resulted in stiffening of the annulus at low loads (i.e.
in the `toe` region, parameter MI) and a decrease in stiffness at
higher applied loads (M150).
[0329] These results suggest that thermal therapy at temperatures
70.degree. C. and greater leads to a more stable transition from
flexion to extension. The depressurization we performed during
specimen preparation created a neutral zone at the transition
between tension and compression, within which small changes in
force resulted in relatively large changes in displacement. After
treatment at higher temperatures, this neutral zone was reduced or
eliminated, as reflected in the graph shown in FIG. 20. It is
further believed that the experimental model was illustrative of,
and that this response would similarly affect, the neutral zone of
intact discs. By contrast, our observation that heat treatment at
temperatures greater than 70.degree. C. softens the annulus at
higher forces suggests that the acutely treated intact disc may be
at increased risk of injury when brought to its range-of-motion
limits. This confirms, in the unique setting of vertebral discs,
similar behavior that has been noted in the shoulder capsule, where
heat has been observed to both acutely shrink and decrease the
linear-region stiffness of the joint. As a result of such prior
observations in that setting, clinical practitioners have
recommended joint protection for six to twelve weeks after
treatment.
[0330] While the trends in our data are comparable to those
reported for other tissues such as the shoulder capsule, the
magnitude of the annular treatment effect in intact tissue is
smaller. For instance, while shoulder capsule contraction has been
reported in at least one study to be 60% after 80.degree. C.
treatment, we observed annular contraction of only 7.8% (E0%) after
heating the intact disc to 85.degree. C. Similarly, shoulder
capsule stiffness reductions at high loads were much greater than
those observed in the intact vertebral discs: we observed stiffness
decreases of 20% (M150), while shoulder capsule stiffness decreases
were on the order of 50%. It is believed that these differences are
likely due to either the unique joint structure or the fiber
orientation of the intact annulus, or both. The shoulder data was
derived from experiments in which the capsule, a linearly oriented
collagenous tissue, was cut into strips along the collagen fiber
direction before testing. In contrast, intact annular collagen is
oriented in two directions at .+-.65.degree. to the spinal axis,
and it is highly constrained both axially, by the adjacent
vertebrae, and circumferentially, by its annular structure. When
the in situ constraints on the annulus were removed by excising the
tissue before heat treatment, we observed a 45% circumferential
shrinkage, which is similar in magnitude to that reported for
linear collagenous tissues. It is believed, therefore, based upon
our observations, that in situ tissue constraint, rather than fiber
orientation, may be the dominant mechanism responsible for the
observed differences.
[0331] Our conclusion that in situ tissue constraint reduces the
effects of thermal therapy on the annulus fibrosus, though not
previously known or confirmed prior to this study, is further
supported by results observed in several other previously reported
studies. In one previous report, for example, only 6.6% shrinkage
was observed in the patellar tendon, a linearly oriented
collagenous tissue, after in situ treatment with laser energy. This
difference was attributed to constraints imposed by the intact
joint. Similarly, a number of other studies have been reported
examining heat-induced changes in the mechanics of chordae
tendineae. Tissue stress was observed to have a retarding effect:
when tissue was stressed during heating, increases in the
temperature, the heating time, or both, were required to achieve
effects noted for unstressed tissue in these studies.
[0332] The mechanism by which tissue stress retards thermal
denaturation has a thermodynamic basis. Tensile stress straightens
tissue collagen and decreases configurational entropy, which in
turn, increases the activation energy required for thermal
denaturation. This retarding effect was clearly evident in intact
annulus, where we observed that several hours of thermal treatment
at 85.degree. C. were required to achieve maximum contraction. In
contrast, at least two groups of prior researchers examining
excised collagenous tissues achieved maximum contraction within 5
minutes. Also, while M150 for an intact specimen treated at
85.degree. C. for 15 minutes was only 18%, the decrease in
stiffness (47%) after several hours of treatment at 85.degree. C.
was comparable to that elsewhere reported for excised shoulder
capsule tissue.
[0333] Our polarized light microscopy data provides further
evidence that tissue constraint effects both the temperature and
time required to achieve a given amount of thermal damage. Collagen
birefringence disappeared completely after heat treatment for 15
minutes at 85.degree. C. in the unconstrained specimen, but it
remained in the intact treated annulus. Clearly 15 minutes of
treatment was not sufficient to fully denature the intact annular
tissue. While it was not possible to quantify the degree of
birefringence in the intact tissue after treatment at 85.degree. C.
relative to that at 37.degree. C. with only one specimen, it
appears that that the treated specimen was less birefringent than
the control. These observations are consistent with the results of
our mechanical tests.
[0334] Differences in the mechanical behavior of the intact annulus
after treatment at temperatures greater than 70.degree. C. indicate
that the tissue underwent a thermally mediated change. However the
results of the mDSC experiments indicate that tissue constraint
prevented significant collagen denaturation: the main denaturation
peak and enthalpy of denaturation of the intact annulus were
unaffected by 15 minutes of treatment at 85.degree. C. Although the
increase in hysteresis after treatment implies an energetic change,
the mechanisms by which the tissue was thermally modified are
unclear. One possible explanation is provided by studies examining
both the structure of collagenous tissue using scanning electron
microscopy (SEM), and endothermic events, using DSC. Using these
techniques, several investigators identified discrete stages of the
denaturation process. They attributed the earliest denaturation
(<56.degree. C.) to the destruction of heat-labile cross-links
(which are more pronounced in young animals), and showed that the
structure of the fibrils remain intact during this process.
[0335] A second contributing factor for the biomechanical changes
is suggested by the observed increase in fractional dry mass in
both our constrained and unconstrained treated tissue relative to
the control tissue. The increase in fractional dry mass indicates
that the tissues heated at 85.degree. C. swell less when
equilibrated in saline. Since annular tissue hydration has been
disclosed to be related to proteoglycan content, our finding
indicates that the proteoglycans of the annulus have been affected
by the heat treatment. Similar to collagen, proteoglycans are
susceptible to denaturation through destruction of heat-labile
hydrogen bonds. Alteration of annular proteoglycan can affect
tissue properties since they have been previously disclosed to play
a role in stabilizing the collagen matrix, as had been observed
according to at least one prior disclosure in articular cartilage
where the modulus decreases significantly when the proteoglycans
are removed. It is thus believed that a portion of the observed
biomechanical changes is due to changes in proteoglycan, the
thermal properties of which are not extensively understood
according to prior publications. Confirmation of such belief as to
the specific mechanism with respect to proteoglycans may be
achieved according to further study and observation by one of
ordinary skill based upon review of this disclosure.
[0336] The retarding effect of stress on annular denaturation has a
number of clinically relevant implications. First, to achieve a
significant degree of collagen denaturation in vivo, the annulus
should be heated either for long times or at high temperatures, or
both. Second, thermal treatment according to the devices and
methods of the present invention may be applied in a selective
fashion. Since unstressed annular fibers are more susceptible to
thermal treatment than stressed fibers, areas of slack tissue (e.g.
the inner annulus in degenerating discs) are preferentially heated,
while preserving structurally competent areas that are carrying
stress (e.g. the outer annulus that retains stress into later
stages of degeneration). Further, patient pre-positioning is
desired for certain circumstances, allowing the practitioner to
selectively stress particular annular regions, thereby further
controlling the zone of biomechanical alterations.
[0337] In another regard, the present invention provides a useful
tool when applied to selectively shrink proliferative
fibrocartilage responsible for annular protrusion and prolapse.
This is accomplished for example by providing the thermal therapy
to degrade proteoglycans and decrease swelling.
[0338] In still a further regard, and as further supported by the
results of this study, the present invention is used to provide
thermal therapy in a manner specifically adapted to ablate annular
nociceptors and cytokine producing cells while sparing tissue
material properties. Thermal therapy in the range of 48-60.degree.
C. is sufficiently low to avoid collagen denaturation and
biomechanical changes, yet this temperature region is desired for
modes of thermal spine treatment intended to induce nerve injury
and cellular death without significant biomechanical change from
the heating (or with biomechanical change if desired and brought
about by other means).
[0339] It is to be further appreciated that the results of this
study, as to specific ranges and/or numbers, are potentially
limited by the use of non-degenerate porcine intervertebral discs.
While porcine discs are similar to human discs in many ways, there
may be differences in denaturation temperature, which is dependent
on a number of factors such as collagen cross-link type and
density. However, the consistent tissue quality and size afforded
by the porcine model minimizes inter-specimen variability and
therefore provides a good system by which to investigate mechanisms
of thermal/biomechanical interactions. The disc height also differs
between human and porcine lumbar discs. Since the lumbar human disc
is generally taller (averaging approximately 11 mm) than the
porcine disc (averaging 3 mm in this study), it may be less
influenced by vertebral constraint and therefore more able to
thermally contract. In this regard, as with many previously
disclosed devices and treatment methods, the exact extent of effect
may vary even between species according to varied anatomy.
[0340] Notwithstanding the foregoing, future studies may be
performed on human discs according to one of ordinary skill based
upon this disclosure to confirm effects of specific treatment
regimens. Moreover, it is further believed that the relationship
between varied temperatures (and/or ranges) and predictably varied
results are well correlated across species, though specific
temperatures, temperature-time dosing, or magnitudes of observed
results may differ. Accordingly, it is believed that the studies
disclosed herein and aspects of the invention related thereto
provide beneficial treatment regimens, though such may clearly
require further tuning in order to be particularly adapted for
specified use in treating a particular patient, patient group, or
even animal type.
[0341] Further to the experimental model of the present Example,
nuclear depressurization allowed for the biomechanical response of
the intact annulus to be isolated. However, for intact discs,
nuclear pressure will increase annular stress and therefore is
believed to further retard thermal effects beyond that observed
here. Finally, the ex vivo study summarized herein does not
characterize any subsequent biologic remodeling that would occur
after heat treatment in vivo. Remodeling likely further modifies
annular tissue properties, and the magnitude and temporal sequence
of this response may be further characterized in a suitable in vivo
model. However, the acute effects provided hereunder provide
significant benefit notwithstanding such potential for
remodeling.
[0342] Despite these limitations, the foregoing observations and
related description demonstrates a number of mechanisms by which
thermal therapy influences the biomechanical response of the
annulus fibrosus. Unique features of the disc--specifically tissue
structure and stress-strain constraints due to attachment to
adjacent vertebrae--have significant impact on the thermal
treatment effect size. Future in vivo animal studies and controlled
human trials may be further performed by one of ordinary skill in
the art based at least in part on this disclosure in order to
further link biomechanical and biological consequences of tissue
heating to the various beneficial patient outcomes.
External Directional Ultrasound Thermal Treatment ("ExDUSTT")
System and Method
[0343] The following description relates generally to FIGS. 23-53
and provide further illustrative embodiments of the invention
according to modes previously described above for providing an
external directional ultrasound thermal treatment (or "ExDUSTT")
device, and method for treating spinal disorders therewith.
[0344] As illustrated in FIG. 23, the illustrative ExDUSTT
applicator 110 of the present invention preferably has a support
member 120 with an ultrasound transducer 130 mounted thereon within
an outer covering 150 that is typically an inflatable coupling
balloon such as is shown.
[0345] According to the further view shown in FIG. 24 during one
mode of use in treating a region 108 of an intervertebral disc 104
associated with a spinal joint 101, the transducer is generally
chosen to be a curvilinear panel that is both directional and
focusing (e.g. converging signals) to help highly localized deep
heating, in particular useful for applications from outside the
disc as shown. It is to be appreciated that "spinal joint" where
used throughout this disclosure generally includes intervertebral
discs, adjacent vertebral bodies, and associated structures such as
posterior vertebral elements such as facet joints.
[0346] As shown in FIGS. 25 and 26, respectively, ExDUSTT devices
of the present invention can be on many different delivery
platforms, such as a rigid pre-shaped platform shown in FIG. 25
with the transducer 130 on the distal bend section 116 and canted
at an angle A for angular directional ultrasound relative to the
proximal shaft 112 axis, or on a catheter-based platform shown in
FIG. 26. Both chassis are beneficial for respective purposes, and
each for common purposes. However, the pre-shaped probe is in
particular useful for angular directional heating at hard to reach
places in the body, such as certain spinal locations, and the
rigidity helps position control.
[0347] FIG. 27A shows an illustrative rigid probe device 200 in
finer detail for further understanding. Distal shaft 202 includes a
4 mm outer diameter brass tube 204 with 0.008'' silver lead wires
206 and water flow lines (e.g. 0.0226'' polyimide tubing) contained
therein and coupled at the proximal end portion (not shown) to a
proximal adapter. A distal 0.1135'' stainless steel tubing 208 is
shown secured with epoxy 210 within the brass tube 204, and has a
window 212 cut out leaving support ridges upon which the transducer
230 is mounted with Nusil 1137 Silicone, as shown in finer detail
in FIG. 27B. Further included beneath the transducer 230 are rubber
threads 236 strung across the window 212 to help provide a good
non-dampening support system. An outer inflation balloon is shown
at 240 and in shadow in the expanded condition for tissue coupling.
As can be appreciated from the figure, an air backing is thus
provided at 238 to provide highly directional ultrasound delivery
away from the central shaft of the device and out through the
eccentric inflation balloon 240 having a diameter D and into tissue
there. Moreover, as illustrated in FIG. 27B, the transducer 230 is
curvilinear having a radius R around an axis that is aligned with
the long axis of the support shaft and thus is focused into tissue
along the transducer and balloon length as such. For the purpose of
a complete description, one exemplary transducer that has been
observed to be useful in this and other ExDUSTT designs herein
shown and described has for example the following specifications:
0.394'' long.times.0.98'' wide.times.0.013'' thick PZT4, 0.59''
radius of curvature.
[0348] Various modifications may be made to the device just shown
and described. For example, the balloon according to that Figure
was elastomeric type, such as 0.005'' wall silicone balloon.
However, better repeatability of size and shape may be required
than what such elastomers can offer, and thus a less compliant
balloon of the preformed type may be used. This is shown for
example at balloon 248 in FIGS. 28A-B that is for example a
pre-shaped PET balloon having a wall thickness for example of
0.001''. Further considerations for materials may be considered,
such as for example thermal properties, ultrasound transmissivity,
profile, etc.
[0349] Moreover, similar features as just described for the ExDUSTT
device may be incorporated onto a different catheter chassis
without much required modification, as referenced in FIGS. 29A-B.
Here a proximal catheter shaft 250 is shown coupled to a distal 4
mm OD brass tube 254. Everything else may be the same as described
above for the rigid probe designs. The catheter shaft 250 may be
multi lumen, or may be a bundle of lumens, etc.
[0350] The transducers shown in the previous FIGS. are not the only
configurations contemplated, either. For example, FIGS. 30A-B show
a curvilinear transducer 260 with its radius of curvature R around
an axis that is transverse (e.g. orthogonal) to the long axis L of
the support shaft 280.
[0351] Further understanding of various modes of operating devices
of the rigid probe type just shown and described are provided in
FIGS. 31A-32B, which reflect operation at 5.6 MHz optimal
frequency, with peak efficiency at 40%, and linear output and
efficiency out to 12 W applied with 5.5 W emitted from the
transducer.
[0352] FIG. 33 shows a test set-up for ex-vivo pig spine treatment
using a catheter-based ExDUSTT device over 5 minute heating period,
and shows certain measured temperatures during a relatively low
temperature mode of operation. T1 is a temperature probe 5 mm deep
into tissue from the transducer coupling interface, whereas T2
temperature probe shows the temperature profile over varied depths
from the transducer.
[0353] In contrast to the ex-vivo data shown in FIG. 33, FIGS.
34A-B show results for in-vivo treatments in pig discs, and show
temperatures all exceeding 55 degrees, though temperatures close to
the transducer exceeded well over 65 degrees and even up to 80
degrees.
[0354] As illustrated in FIG. 35, various different sizes may be
used depending upon the particular need, and a kit of different
sizes, lengths, angles, A, radii R, etc. may be provided. The
devices 270, 280 shown in FIG. 35 generally differ in that the
larger device supports a 3.5 mm wide ultrasound transducer, whereas
the smaller device supports a 2.5 mm wide transducer. In general,
other features may be similar unless desired to change them,
whereas for the embodiment kit shown, each device has other
components scaled to meet the 2.5:3.5 comparison for the transducer
widths. Other variations may be made, however.
[0355] For the purpose of further characterization, and
understanding of directivity and focus of energy delivery as
relates to the present invention, FIGS. 36A-B and 37A-B show
certain output power profiles across the transducer faces for both
2.5 mm and 3.5 mm curvilinear transducers, respectively. The radius
of curvature for these transducers is around an axis that is
aligned with the long axis of these plots.
[0356] Various thermal treatment studies have been performed with
working prototypes of the present invention and will be explained
hereafter in part by reference to the test set-up for the rigid,
pre-shaped bent ExDUSTT device shown in FIG. 38.
[0357] For example, as shown in FIG. 41, all temperatures monitored
using 0 degree C. cooling during relatively high temperature mode
of operation were above 60 degrees C., even out to 10 mm deep, and
in particular were above 70 degrees C. for most all data taken at 5
mm depth, whereas temperatures predicted at 7 mm deep were also in
excess of 70 degrees. Other illustrative and informative results
are reported up through FIG. 53 with respect to additional modes of
ExDUSTT operation, which are best understood by further reference
to the Brief Description of the Drawings above.
[0358] Various different modes and embodiments for curvilinear
transducers may be suitable for use according to the various
embodiments herein described, such as for example the various
ExDUSTT device embodiments just described However, the following
provides some further detail for particular modes and variations
contemplated for the purpose of providing a more complete
understanding
[0359] In one regard, these transducer segments such as used in the
ExDUSTT devices (and per for example the earlier embodiment in FIG.
6C) are sectors of larger diameter cylinders or plated tubes, with
ultrasound energy emitted from the concave surface. Examples
include 0.394'' (+/-0.005'').times.0.098'' (+/-0.002'') linear
wide.times.0.013 thick which form an 14.2 deg. Arc segment of 0.4''
inner radius tube. One can realize different diameters or arc
segments, such as 9.5 deg. Arc segment of 0.591'' inner radius
tube. These can be purchased for example from vendors such as
Boston Piezo-optics using materials such as PZT-4, 5, or 8.
[0360] The radius of curvature can be selected to sharpen or
decrease the amount of energy concentration or apparent focusing
(i.e., radius of curvature of 0.5, 0.75, 1.0, 1.5, 2.0 cm can be
appreciated) with the higher radius of curvature and wider
transducers giving more penetrating distributions. The width can
vary to suit particular needs for operation or device
compatibility, but may be for example between about 1.5 mm to about
6 mm; whereas the length can also vary to meet particular needs,
such as for example from between about 2 mm to about 10 mm or
greater. Transducers meeting these specifications are in particular
useful for various of the embodiments herein described, provided
however that such embodiments nor other aspects of the invention
should not be considered to be so limited to only these
dimensions.
[0361] These transducers can be mounted in transducer assemblies
using a variety of suitable means. Flexible adhesives (e.g.
silicone adhesive, Nusil), rigid epoxies or conformal coatings (Dow
Corning) may be used. Rigid metal (brass or stainless steel) or
plastic assemblies can be machined to hold the transducers and
maintain air-backing. One more detailed example incorporated into
many of the ExDUSTT devices shown and described includes a filed
down, 15 mm long portion (or specified length) across a 180 degree
plane transversely through a distal stainless-steel support
hypotube. This forms a shelf for either side of the transducers to
be mounted. Lead wires (such as for example either silver lead wire
or miniature coaxial cable (Temflex, Inc)) are soldered to the
transducer surfaces for power application and can be run within the
central lumen of the SS.
[0362] A thin layer of silicone adhesive can be placed upon the
edges of the tube structure, and the transducer segment placed. The
transducer can then be sealed using silicone adhesive and/or
conformal coating. The conformal coating can be accelerated using
elevated heat for about 60 min. Alternatively, rubber thread can be
used for a spacer with silicone adhesive, to keep transducers from
contacting the metal surface. Other holding devices can be
implemented, including pieces machined from brass bar or rod with
gaps for the air space and offsets to support. In some
implementations, it may be desired to circulate water or fluid
behind the surface of the transducers.
[0363] These transducer assemblies can be either modular catheter
form insertion into target tissue (intra-discal) or rigid external
applicator. It is not necessary, but these transducers can be
sealed using epoxy and polyester layers a previously described, or
using mineral oil or other type of oil instead of Epotek, or the
transducer can be left bare, though in many applications would be
sealed on its edges and possibly top surface with conformal coating
for watertight integrity and durability. Custom multilumen
extrusions in materials such as pebax can form the flexible
catheter member of which the transducer assembly is attached. The
transducers are rigid, but if multiple segments are used, they may
be coupled in a manner providing flexible hinges for better
bendability in use.
[0364] Pre-shaped high-pressure balloons such as those herein shown
for ultrasound tissue coupling can be provided in various shapes.
Suitable sources include for example custom fabrication, such as
for example by Advanced Polymers, or may be made in house by
heat-stabilizing the PET heat-shrink in pre-determined shape using
molds and Teflon-coated mandrels. These balloons can have a neck
that is 3 mm OD and a one sided inflation with a 2 mm radius.
Compliant balloons using silicone, c-flex, polyurethane, or other
material can also be used for various applications indicating such
compliance or elastomeric properties.
[0365] These devices can have temperature regulated flow, flow in
general, or no flow at all. In addition, devices without
encapsulating balloons can be realized with sterile saline or fluid
flow used to cool and couple US to the interface.
Internal Directed Ultrasound Thermal Therapy ("InDUSTT.TM.") System
and Method
[0366] The following description relates to device and method
embodiments in particular adapted for use internally within
intervertebral discs or other joints, e.g. "InDUSTT" devices and
methods.
[0367] The following FIGS. and accompanying description is to be
read in conjunction with prior description herein made above, and
in any event relate to InDUSTT devices such as that shown at
catheter 290 in FIG. 54. More specifically, FIG. 54 illustrates
arrangements for two alternative modes of InDUSTT assemblies and
treatments as follows. Catheter 290 is shown at the top of the
Figure in a "direct coupling mode" and is adapted to be delivered
directly into a region of a spinal joint, e.g. within the disc or
bony structure, with the transducer coupled directly to tissue.
Thus, there is only shown a coupling 294 such as for electrical
leads 296, and fluid cooling coupling 298. As shown in the assembly
of FIG. 54 on the bottom, however, a catheter cooled or "cc"
arrangement differs from the direction coupling or "cc" arrangement
in that a catheter 290 is buried within a closed housing of an
outer delivery device 300 that has a sharp pointed tip 302 for
puncturing into an intervertebral disc. Water circulation ports
298,310 according to this arrangement cycle cooling fluids between
a lumen within the internal catheter 290 and over the internal
catheter 290 but within the outer sheath 300.
[0368] Further details of the cc arrangement are variously shown in
FIGS. 55A-C, wherein a transducer 320 is of a cylindrical tubular
type that has sectored grooves 322 (FIG. 55C) on either side of an
electroded and active portion 326 for directional ultrasound
delivery along about a 90 degree span of space radially outward
from that section, and thus both directionality is achieved, as
well as diverging US signal. Couplers shown include power lead
coupler 294, water inflow coupler 298, water outflow coupler 310.
As shown in FIG. 55B, the water cooling is aided by a distal port
299 in the internal catheter device 290. A thermocouple 330 is
shown along the active sector, as well as others may be provided
elsewhere (not shown) such as along the other dead sector as
temperature monitoring may still be important there to protect
certain tissues from conductive heating during US therapy on the
opposite side of the catheter. The transducer shown may be for
example 1.5 mm outer diameter, 0.9 mm inner diameter, by 10 mm long
and mounted over a plastic support ring. The outer catheter 300 may
be for example constructed from a simple polymeric tubing such as
made from CELCON.TM. from Best Industries typically used
conventionally for implanting radiation seeds in tumor therapy and
of 13 gauge construction.
[0369] For the purpose of providing a thorough understanding of the
many different aspects and considerations of using the InDUSTT
device just described, a significant amount of summary results from
multiple studies of working embodiments is herein provided by
reference to FIG. 56A and beyond. A thorough understanding of
various aspects of these results and experimental arrangements
shown is gleaned by review of the Brief Description of the Drawings
above. In general, where discs are indicated by an arrangement such
as "C3-4" or "C4/5" such designates the vertebrae in the animal
between which the disc was treated. In addition, curve legends
designating numbers for graphs (such as for example "Probe 1-1",
"Probe 1-2", etc. in FIG. 65A) designate thermocouples along
temperature monitoring probes in the disc tissue, typically spaced
by 5 mm apart.
[0370] Accordingly, as is reflected in the graphs and other
pictures and Figures, many different discs were treated. Still
further, the test results shown also reflect an understanding of
the effects of cooling at different temperatures, as well as direct
coupling versus catheter cooled coupling, as well as relatively
high versus relatively low temperature modes of use.
[0371] While the results shown in these latter FIGS are in
non-human animal models, the results, and in particular the
relationships between results between different treatment groups,
correlate to the human condition and are confirmed by earlier human
cadaver studies performed. Actual values may of course differ,
however, but it is believed that the extreme ends of the results
would apply across vertebrate animal species. Moreover, the date
suggests that directivity is confirmed, as is the ability to
achieve high temperatures over 70 degrees or even 75 degrees, as
well as control heating to lower temperatures for other intended
treatments.
[0372] In one example, FIGS. 59A and B show two sets of lines that
cross at time equal to about 900 seconds. This indicates a period
of time when the InDUSTT device, with sectored, directional
ultrasound emission, was rotated. Accordingly, the uniform change
in temperature reflects the preferential heating that can be
achieved with such device and not heretofore possible. For further
illustration, FIG. 65A shows similar results according also to
turning a directional device to realign the active sector to
different transducers.
[0373] Various embodiments have been herein described, including
ExDUSTT, InDUSTT, rigid-probe based, catheter based, directly
coupled, actively cooled, sectored transducers, curvilinear
transducers, axially aligned transducers, transversely aligned
transducers, relatively large transducers, relatively small
transducers, compliant elastomeric coupling balloons, relatively
non-compliant pre-formed coupling balloons, relatively high
temperature modes of operation, relatively low temperature modes of
operation, low temperature cooling, room temperature cooling,
preshaped, flexible, guidewire delivery, and deflectable/steerable
delivery platforms. It is to be appreciated that the more detailed
description for such embodiments provided herein is for the purpose
of illustration, and other modes of achieving such may be suitable
for inclusion according to the invention without departing from the
present scope. Moreover, the combinations of such features herein
shown are highly beneficial, but not intended to be limiting. Other
combinations may be made without departing from the intended scope
hereof. For example, the particular embodiments shown and described
for "ExDUSTT" applications are described as such merely according
to their highly beneficial ability to perform in that arrangement,
but they may be used as InDUSTT devices as well, despite their
particular external use benefits. The opposite is true, as well,
with respect to InDUSTT devices which may also be used in other
external locations such as for disc heating. The devices shown and
described may be used within or around the bony structures of
spinal joints, too. Moreover, where various of the features may be
highly beneficial for particular applications, they may not be
necessary for other applications. For example, directional energy
delivery is a highly beneficial aspect of the various ultrasound
embodiments herein shown and described, in particular where highly
localized heating is desired while other surrounding tissues need
to be protected such as nerves. However, in other applications,
such as some complete disc remodeling applications for example,
non-directional emission may be suitable to heat all the
surrounding tissue equally.
[0374] It is to be appreciated that the various modes of devices
and operation herein described, together with tissue
characterization studies performed and herein presented, provide a
significant understanding with respect to adapting and controlling
thermal therapy, or other modes of ultrasound delivery for therapy,
in special areas in the body such as joints, and in particular
spinal joints and their discs and bony structures. Back pain and
other issues in these joints are significant medical issues that
may be addressed with the present invention according to its many
different modes and aspects.
[0375] Although the description above contains many specificities,
these should not be construed as limiting the scope of the
invention but as merely providing illustrations of some of the
presently preferred embodiments of this invention. Thus the scope
of this invention should be determined by the appended claims and
their legal equivalents. Therefore, it will be appreciated that the
scope of the present invention fully encompasses other embodiments
which may become obvious to those skilled in the art, and that the
scope of the present invention is accordingly to be limited by
nothing other than the appended claims.
[0376] In the claims, reference to an element in the singular is
not intended to mean "one and only one" unless explicitly so
stated, but rather "one or more." All structural, chemical, and
functional equivalents to the elements of the disclosed embodiments
that are known to those of ordinary skill in the art are expressly
incorporated herein by reference and are intended to be encompassed
by the present claims. Furthermore, no element, component, or
method step in the present disclosure is intended to be dedicated
to the public regardless of whether the element, component, or
method step is explicitly recited in the claims. No claim element
herein is to be construed as a "means plus function" element unless
the element is expressly recited using the phrase "means for". No
claim element herein is to be construed as a "step plus function"
element unless the element is expressly recited using the phrase
"step for".
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