U.S. patent application number 11/044987 was filed with the patent office on 2005-06-30 for method for removing plaque from blood vessels using ultrasonic energy.
This patent application is currently assigned to OmniSonics Medical Technologies, Inc.. Invention is credited to Hare, Brad A., Rabiner, Robert A..
Application Number | 20050143660 11/044987 |
Document ID | / |
Family ID | 25519805 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050143660 |
Kind Code |
A1 |
Rabiner, Robert A. ; et
al. |
June 30, 2005 |
Method for removing plaque from blood vessels using ultrasonic
energy
Abstract
A method and apparatus for removing plaque, fatty deposits, and
other occlusions from blood vessels using ultrasonic energy. The
method and apparatus has particular application in removing plaque
from the carotid artery in a non-thermal manner. The apparatus is
designed to have as small a cross-sectional profile as possible,
therefore allowing the apparatus to be used in a minimally-invasive
manner. As a result, the apparatus can be used in both surgical and
outpatient treatment with minimal post-operative complications and
minimal damage to areas other than the area of treatment. An
ultrasonic probe may include aspiration channels on its outer
surface. An aspiration sheath may surround the ultrasonic probe,
such that the location of an aspiration port may be varied axially
relative to the ultrasonic tip.
Inventors: |
Rabiner, Robert A.; (North
Reading, MA) ; Hare, Brad A.; (Chelmsford,
MA) |
Correspondence
Address: |
PALMER & DODGE, LLP
RICHARD B. SMITH
111 HUNTINGTON AVENUE
BOSTON
MA
02199
US
|
Assignee: |
OmniSonics Medical Technologies,
Inc.
|
Family ID: |
25519805 |
Appl. No.: |
11/044987 |
Filed: |
January 27, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11044987 |
Jan 27, 2005 |
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10635200 |
Aug 6, 2003 |
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6866670 |
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10635200 |
Aug 6, 2003 |
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09972555 |
Oct 5, 2001 |
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6660013 |
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09972555 |
Oct 5, 2001 |
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09618352 |
Jul 19, 2000 |
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6551337 |
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60157824 |
Oct 5, 1999 |
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60178901 |
Jan 28, 2000 |
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Current U.S.
Class: |
600/467 |
Current CPC
Class: |
A61B 17/00234 20130101;
A61B 2017/293 20130101; A61B 2017/00274 20130101; A61B 2017/22007
20130101; A61B 2017/22015 20130101; A61B 17/22012 20130101; A61B
2017/22002 20130101; A61B 2217/007 20130101; A61B 2017/320073
20170801; A61B 2017/22008 20130101; A61B 2017/22018 20130101; A61B
2017/320084 20130101; A61B 2217/005 20130101; A61B 2017/22051
20130101; A61B 2017/00137 20130101 |
Class at
Publication: |
600/467 |
International
Class: |
A61B 008/14 |
Claims
What is claimed is:
1. A method for removing plaque from a blood vessel using an
ultrasonic energy, comprising the steps of: inserting an ultrasonic
probe into the blood vessel; extending a portion of the ultrasonic
probe to an area adjacent to the plaque on an inner surface of the
blood vessel; transmitting ultrasonic vibrations to the portion of
the ultrasonic probe; reducing the plaque to a particulate material
by producing cavitation in a vicinity of the plaque.
2. A method of claim 1 wherein the ultrasonic vibrations are
transmitted in an axial direction along the ultrasonic probe and in
a direction transverse to an axial direction of the ultrasonic
probe.
3. The method of claim 1 further comprising irrigating the plaque
with a fluid before transmitting the ultrasonic vibrations to the
portion of the ultrasonic probe.
4. The method of claim 1 further comprising aspirating the
particulate material after reducing the plaque to the particulate
material.
5. The method of claim 1 wherein the blood vessel is a carotid
artery.
6. The method of claim 1 wherein the transmitting of the ultrasonic
vibrations is at a power level sufficient to reduce the plaque to
the particulate material having individual particles with a
diameter at least as small as about 10 microns.
7. The method of claim 1 further comprising monitoring a location
of the distal end of the ultrasonic probe in the blood vessel.
8. The method of claim 7 wherein the location of the distal end of
the ultrasonic probe is monitored using ultrasound.
9. A method for reducing plaque in a blood vessel comprising:
providing a flexible member comprising a proximal end, a distal end
and a longitudinal axis between the proximal end and the distal
end; inserting the flexible member into the blood vessel; moving
the flexible member in the blood vessel and placing the flexible
member in communication with the plaque; and providing an
ultrasonic vibration to the flexible member, creating a transverse
ultrasonic vibration along at least a portion of the longitudinal
axis of the flexible member with a plurality of anti-nodes along
the flexible member.
10. The method of claim 9 wherein the flexible member is an
ultrasonic probe.
11. The method of claim 9 further comprising reducing the plaque to
a particulate material having a diameter less than about 10
microns.
12. The method of claim 9 wherein the plurality of anti-nodes
create a cavitation in a fluid surrounding the flexible member to
ablate the plaque.
13. The method of claim 9 wherein an ultrasonic vibration generator
produces the ultrasonic vibration in a range of about 20 kHz to
about 80 kHz.
14. The method of claim 9 further comprising moving the flexible
member in an axial direction within an aspiration sheath to move
the distal end of the flexible member axially inwardly and axially
outwardly relative to a distal end of the aspiration sheath.
15. The method of claim 9 wherein the flexible member comprises a
flexibility to support the transverse ultrasonic vibration.
16. A method for removing a fatty deposit from a carotid artery
comprising: providing an ultrasonic probe comprising a proximal
end, a distal end and a longitudinal axis between the proximal end
and the distal end; inserting the ultrasonic probe into the carotid
artery; moving the ultrasonic probe in the carotid artery and
placing the ultrasonic probe in communication with the fatty
deposit; providing an ultrasonic vibration to the ultrasonic probe,
creating a transverse ultrasonic vibration along at least a portion
of the longitudinal axis of the ultrasonic probe with a plurality
of anti-nodes along the ultrasonic probe; and reducing the fatty
deposit to a particulate material by producing an area of
non-thermal cavitation in a vicinity of the fatty deposit.
17. The method of claim 16 wherein the fatty deposit is reduced to
a diameter less than or equal to about 10 microns.
18. The method of claim 16 wherein an ultrasonic vibration
generator produces the ultrasonic vibration in a range of about 20
kHz to about 80 kHz.
19. The method of claim 16 further comprising irrigating the fatty
deposit with a fluid before providing the ultrasonic vibration to
the ultrasonic probe.
20. The method of claim 16 further comprising aspirating the
particulate material after reducing the fatty deposit to the
particulate material.
Description
RELATED APPLICATIONS
[0001] This is a divisional of application Ser. No. 10/635,200,
filed Aug. 6, 2003, which is a divisional of application Ser. No.
09/972,555, now U.S. Pat. No. 6,660,013, filed Oct. 5, 2001, which
is a continuation-in-part of application Ser. No. 09/618,352, now
U.S. Pat. No. 6,551,337, filed Jul. 19, 2000, which claims priority
from Provisional Application No. 60/157,824, filed Oct. 5, 1999,
and Provisional Application No. 60/178,901, filed Jan. 28, 2000,
the entirety of all these applications are hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to a method and an apparatus for
removing plaque, including fatty deposits and other occlusions from
blood vessels. More particularly, the invention relates to a method
and apparatus for ablating plaque from the carotid artery by
utilizing ultrasonic energy.
BACKGROUND OF THE INVENTION
[0003] A blockage of a blood vessel is the most frequent cause of
stroke and is responsible for about 75 percent of the nearly
150,000 U.S. stroke deaths each year. Stroke ranks as the third
leading killer in the United States after heart disease and cancer.
There are 500,000 to 600,000 new strokes in the United States each
year. As many as 3 million Americans have survived a stroke with
more than 2 million of them sustaining some permanent disability.
The overall cost of stroke to the nation is $30 billion a year.
[0004] A carotid endarterectomy is a surgical procedure in which a
doctor removes fatty deposits from one of the two main arteries in
the neck supplying blood to the brain. Carotid artery problems
become more common as people age. The disease process that causes
the buildup of fat and other material on the artery walls is called
atherosclerosis, commonly known as "hardening of the arteries." The
fatty deposits are called plaque, and the resulting narrowing of
the artery is called stenosis. The degree of stenosis is usually
expressed as a percentage of the normal diameter of the opening.
Carotid endarterectomies are performed to prevent stroke. Two large
clinical trials supported by the National Institute of Neurological
Disorders and Stroke (NINDS) have identified specific individuals
for whom the surgery is highly beneficial when performed by
surgeons and in institutions that can match the standards set in
those studies. The surgery has been found highly beneficial for
persons who have already had a stroke or experienced the warning
signs of a stroke and have a severe stenosis of 70 percent to 99
percent. In this group, surgery reduces the estimated 2-year risk
of stroke by more than 80 percent, from greater than 1 in 4 to less
than 1 in 10. In a second trial, the procedure has also been found
highly beneficial for persons who are symptom-free but have a
severe stenosis of 60 percent to 99 percent. In this group, the
surgery reduces the estimated 5-year risk of stroke by more than
one-half, from about 1 in 10 to less than 1 in 20.
[0005] A stroke occurs when brain cells die because of decreased
blood flow to the brain. In some cases, small pieces of plaque in
the carotid artery may break loose and block an artery in the
brain. The narrowed opening in the carotid artery can be a source
of blood clots that travel to the brain, can trap blood clots from
other areas of the body, or can become completely clogged.
[0006] U.S. Pat. No. 4,867,141 discloses a medical treatment
apparatus which utilizes ultrasonic energy for medical treatment,
particularly to break up a stone formed in a living body. An
endoscopic channel is used to insert a portion of the apparatus
into a body cavity, where an ultrasonic transmission member is used
to transmit ultrasonic vibrations to the stone which is in contact
with the distal end of the apparatus. A perfusion liquid is
supplied to the area of the stone as the stone is being broken up
by mechanical ultrasonic vibrations. This perfusion liquid is
suctioned away from the area of the stone. As a result of the
suction, the perfusion liquid and broken pieces of the stone are
drained away from the body cavity. The apparatus of that patent is
configured with an ultrasonic transmission member which is aligned
and coaxial with the central axis of the probe, and therefore is
effective in treating conditions--such as stones--where the
irregularity or condition to be removed is aligned with the body
vessel through which the endoscope passes. The device of that
patent is used on non-hydrated calcified tissue, and uses direct
mechanical vibration of the calcified tissue in order to result in
tissue fracture and destruction.
[0007] U.S. Pat. No. 5,176,677 discloses an endoscopic ultrasonic
rotary electrocauterizing aspirator. The background section of that
patent includes some discussion of medical literature relating to
prostatectomies, and in particular the Krawitt et al. technique, in
which a gland can be removed using ultrasonic treatment without
effecting to the prostatic capsule. However, the apparatus shown in
that patent is disclosed as being useful for arthroscopic surgery.
The apparatus shown in that patent includes a feature for providing
irrigating fluid to the tip of the ultrasonic probe, as well as
mechanisms for aspirating the area around the tip. The aspiration
and irrigation features of that invention require individual
passageways coaxial with the ultrasonic working tip, each connected
to a source of pressurized fluid, for irrigation, or to a source of
reduced pressure, for aspiration. The apparatus of that invention
also includes other features adjacent the tip, such as an insulated
hood for removing obstructions, and a telescopic viewing apparatus.
The irrigation, aspiration, insulated hood and telescopic viewing
apparatuses all increase the cross-sectional profile of the
apparatus. The design of that apparatus also is such that it may
only treat areas which are directly axially in front of the
ultrasonic probe, and therefore which are axially aligned with the
lumen or incision through which the probe is inserted.
[0008] Various other patents show apparatuses which use ultrasonic
energy to fragment or transform body tissue. U.S. Pat. Nos.
5,112,300; 5,180,363; 4,989,583; 4,931,047; and 3,805,787 each show
ultrasonic treatment apparatuses for use in treating various
medical conditions. In each of these patents, some mechanism is
shown for providing irrigation and/or aspiration in the area where
the ultrasonic treatment is being performed. In each of these
patents, however, the mechanisms for irrigation or aspiration are
structured such that they increase the overall cross-sectional
profile of the instrument. In addition, in each of those patents,
the irrigation and aspiration ports are a fixed distance from one
another, which may not be varied.
[0009] "Ultrasonic processing," as used in the prior art for, inter
alia, orthopedic surgery, is a technique wherein a body--either
liquid or solid--is, in effect, "blasted" by ultrasonic energy. In
ultrasonic processing, the ultrasonic energy produced by the
ultrasonic vibrator influences water molecules found within the
body tissue. The ultrasonic energy is in the form of very intense
sound vibrations at a very high frequency. These intense,
high-frequency sound vibrations result in powerful chemical and
physical reactions in the water molecules within the body tissue.
The reactions in the water molecules ultimately results in a
process called "cavitation," which can be thought of as a form of
cold (i.e., non-thermal) boiling of the water in the body tissue,
wherein there is a rapid creation and collapse of numerous
microscopic bubbles in the water.
[0010] The result of cavitation in water is a "breaking" of that
fluid. The rapid vibrations in water caused by the application of
ultrasonic energy to the water and the resultant cavitation can
cause fatigue in the water molecules which will break bonds between
the water molecules. The result is that the water changes from a
liquid form into a gaseous form, i.e., converts into steam, but
this conversion is done without the need for application of thermal
energy to the water. The result is a "cold boiling" of the
water.
[0011] When a steam bubble is created in a cold liquid, such as
upon the application of ultrasonic energy to water, the steam will
condense because it is surrounded by a cold liquid. As a result, a
void or cavity is created. The surrounding water molecules rush in
to fill that cavity; when they reach the center of the cavity, they
collide with each other with great force. This process is called
cavitation. Cavitation is a known phenomenon which results in shock
waves running outward from the collapsed bubble. The shock waves
caused by cavitation can wear away or destroy material. For
example, such shock waves are known to wear away metal at the edges
of an outboard motor propeller.
[0012] Ultrasonic processing or ultrasonics is the application of
sound at extremely high intensity and high frequency (normally
above human hearing; 20 kHz and above) so as to result in material
changes. Ultrasonics are used in a number of different applications
in order to change a variety of different materials. Ultrasonics
accelerates both physical and chemical reactions in the materials
to which ultrasonic energy is applied and these reactions, among
many other things, are accomplished largely due to the action of
cavitation. There are more actions inherent in bubble collapse
which are of significance. As used herein, the term "bubble" refers
to a space within a liquid which contains a gas or vapor. However,
after that gas or vapor condenses, there is still a void or cavity
in that space until an implosion occurs. Therefore the term
"bubble," as used herein, also refers to the void or cavity.
[0013] One description of the manner in which cavitation is used in
medical applications has been provided by Professor Lawrence Crum
of the Applied Physics Laboratory at the University of Washington
in Seattle, and can be found at the website:
<http://nero.apl.washington.edu/harle-
tt2/artgwww/acoustic/medical/medical.html>. Professor Crum,
writing about lithotriptry--in which a kidney stone is broken with
ultrasonic energy--has stated that "[w]hen pressure surrounding a
bubble falls below the vapor pressure of the liquid, the bubble
fills with vapor and grows explosively. The bubble collapses
violently when pressure returns. If the collapse occurs near a
boundary, such as [a]targeted kidney stone, a high velocity liquid
jet is formed that impacts the boundary with great force. These
extremely violent processes are thought to play a major role in
stone destruction and associated tissue damage."
[0014] In addition to erosion or ablation of surfaces by the jet,
cavitation causes many other actions. Notable among these in a
purely physical sense is the action of intense shock fronts
generated by imploding cavitation bubbles against kidney stones
(lithotriptry), gall stones, tumors, and other intrusions in the
body. Some of this action can also be accomplished by direct impact
of a vibrating ultrasonic tool tip, but no (or minimal) cavitation
is involved.
SUMMARY OF THE INVENTION
[0015] It is an object of the invention to provide a method and an
apparatus for removing plaque, fatty deposits and other occlusions
from the inner lining of blood vessels, particularly the carotid
artery, using ultrasonic energy.
[0016] It is another object of the invention to provide an
ultrasonic medical device capable of destroying and emulsifying
plaque, fatty deposits and other occlusions, which can develop
along the wall of the carotid artery, through cavitation with a
high efficiency by means of a flexible probe operating in a
transverse mode. As used herein, a transverse mode of operation is
used to describe a flexible probe with a plurality of nodes and
anti-nodes along the length of the probe.
[0017] It is a further object of the invention to provide a method
and apparatus for removing plaque buildup from arterial walls which
does not require direct contact with the wall and thereby avoids
any potential damage to the artery.
[0018] The apparatus of the present invention is designed to have a
small cross-sectional profile, therefore allowing the apparatus to
be used in a minimally-invasive manner, either through the use and
application of a small surgical cut down procedure to expose the
artery or through the insertion of a small vascular introducer and
the subsequent insertion of an ultrasonic probe to apply the energy
source. In particular, the device according to the present
invention may operate to remove deposits in the carotid artery from
the internal lumen of the vessel outwards without necessarily
requiring touching or direct abrasion of the vessel walls of the
artery, which might otherwise be necessary with conventional
methods and which can lead to damage of the artery walls. The
application of the ultrasonic energy is applied in the lumen,
wherein the energy migrates from the probe outward towards the
obstruction or luminal constriction. Thus the microfragmentation of
the materials occurs in a controlled fashion. On the other hand,
traditional means of carotid surgery typically requires the peeling
of the occlusive materials from that of the vessel wall. This
maximum contact fashion--where the plaque is "torn" from the
vessel--causes secondary damage to the vessel. The present
invention is advantageous in that it can be used in both
traditional surgical sites and out-patient treatment with minimal
postoperative complications and minimal damage to areas other than
the area of treatment. The present invention therefore provides
distinct advantages over the prior art in the treatment, and
therefore provides an improved method of removing plaque from the
carotid artery. It is to be understood, however, that although the
present invention is designed for removing plaque from the carotid
artery, its small cross-sectional profile makes it useful for
treatment of any condition wherein minimally invasive techniques
are advantageous and reduce post-surgical complications, and the
present invention is therefore not limited to the treatment of
removing plaque from the carotid artery. For example, the removal
of plaque, fatty deposits and other occlusions in other blood
vessels is possible using the invention.
[0019] The probe of the present invention is specifically designed
to have a minimal cross-section, particularly for use for removing
plaque from the carotid artery, thereby minimizing post-procedure
complications and discomfort to the patient because larger sizes
are more difficult to insert and uncomfortable. One way in which
the present invention allows the cross-sectional profile of the
probe to be minimized is by allowing aspiration to occur through
grooves or channels on the outer surface of the probe. In this way,
there is no need for an additional tubular aspiration sheath to be
inserted into the carotid artery, to thereby provide a aspirating
path.
[0020] The device is capable of reducing materials to levels equal
to or smaller than 10 microns. With regard to remaining in the
blood stream, it is known that particulate material of this size
does not pose any health concerns. There are several ways to
accomplish aspiration. For instance, a series of grooves or
channels on the probe may be used. Instead, a standard vascular
introducer can be used whereby aspiration is caused by the
placement of an aspiration source on the luer lock fitting of the
vascular introducer. In another embodiment, hollow tubes (as in a
central lumen or an outer sheath that sits around the probe) can be
used to draw and remove destroyed materials from the surgical site.
This can be accomplished with a suction source at the handle or via
the use of an induced aspiration through the ultrasonic motion of
the probe or negative wave to pull the particulate back and out of
the probe and surgical site. In each of these methods a relatively
small amount of irrigation, e.g., approximately 10 ml per minute,
may be provided to act as a lubricant to the site.
[0021] The terminus or termini of the irrigation passage can be
located at the tip of the probe. Alternatively, the terminus or
termini can be lateral to the probe tip--determined by the
frequency of the system and the location of the nodes and anti
nodes.
[0022] An object of the present invention is to provide a device
and method for removing plaque from a vessel that is non-thermal.
This is accomplished by the application of transverse ultrasonic
energy which is extremely efficient, requiring substantially less
energy to be delivered to the probe to stimulate cavitation. As a
result of the reduced energy required, less actual losses in energy
are realized during operation. Accordingly, because of the use of
cavitation as the mechanism for destroying and emulsifying plaque,
together with the use of irrigation and aspiration, the method and
apparatus of the present invention can destroy and remove plaque
within a range of temperatures of .+-.3.degree. C. from normal body
temperature. Studies now show that this temperature range can be
reduced even further. Therefore, complications attendant with the
use of thermal destruction or necrosis of tissue--such as swelling
or edema--as well as loss of elasticity are avoided.
[0023] Various means to remove plaque from blood vessels are known
in the art. For instance, carotid surgery can be accomplished by
making an incision through a patient's skin to expose the vessel,
cross clamping the vessel to preclude flow, making an incision to
open the vessel itself, removal of the occlusion, and closure of
the vessel and the skin. Additionally, in a similar procedure, a
bypass line can be used to allow for the small flow of blood to the
brain during the procedure prior to the cross clamping and
cessation of flow.
[0024] It is an object of the invention to provide a means to
remove plaque from blood vessels without precluding blood flow.
This is accomplished by avoiding contact with the arterial wall by
inserting the probe into the vessel--like that of a standard
vascular introducer stick. The probe sits in the vessel--in the
middle of the lumen--surrounded by the occlusive materials.
[0025] The probe of the present invention, because of its
significantly reduced cross-sectional profile, can be made to be
flexible or bendable. The probe can be of a cross-section
sufficiently small that the material of the probe is bendable
through a wide range of articulation angles. The probe may housed
in an articulated catheter or sheath, which catheter or sheath can
be fabricated to be bendable or articulated. As a result, the
present invention can be adapted to allow for the probe to activate
and treat even areas of the body which are not axially aligned with
the channel or lumen through which the probe is inserted. The
articulation of the probe of the present invention allows for a
"windshield wiper" action of the probe tip, thereby creating a cone
or arc sweep, greatly increasing the area of effect of the
treatment through an incision.
[0026] The probe of the present invention is particularly useful in
a treatment technique in which the treated area may be imaged by
ultrasound imaging, in particular color ultrasound. The vibrating
length of the probe echogenically produces a pronounced and bright
image on ultrasound, and therefore is readily viewable by the
surgeon or physician, greatly increasing the ease of use and
effectiveness of treatment.
[0027] The probe of the present invention is particularly amenable,
because of its small size, to the use of a flexible fiberoptic
viewing device. The device preferably includes a fiberoptic cable
tip which is fed with the probe--either attached to the probe or
separate from the probe--and which cable is connected to a
fiberoptic viewing eyepiece which is not connected to the handle or
other equipment of the ultrasonic mechanism. In this way,
manipulation of the viewing system is reduced to a minimum. The
fiberoptic cable preferably includes a central optical viewing
cable surrounded by illumination fibers. The fiberoptic cable may
be located inside of a flexible sheath portion of the device,
located on top of the flexible sheath, or may be located on top of
a rigid sheath of the device.
[0028] The method of the present invention, because it uses
ultrasonic energy prevents damage to the surrounding artery during
insertion, treatment and removal, and also reduces or eliminates
tissue damage, irritation and swelling in the patient.
[0029] The present invention also provides advantages to the
physician rendering the treatment. The present invention is safer
for the physician, because the components of the apparatus and
method of the present invention deliver only ultrasonic energy, and
as a result the ultrasonic energy's affect is based on tissue
planes and their hydration levels. Furthermore, the area in which
the cavitation is effective in the apparatus of the present
invention is an area on the order of 1-2 mm around the ultrasonic
probe. As a result, the present invention allows a much higher
degree of control of the affected area than prior art techniques.
The present invention results in the destruction of no carotid
artery wall tissue.
[0030] Another advantage of the present invention relates to the
size of the particulate material broken down from the plaque. In
all other applications used to remove occlusive materials, the
operator is required to be vigilant in removing large particulate
within the blood stream. This is because particulate larger than
500 microns may have significance to the patients overall health.
However, in the present method, the application of ultrasonic
energy towards the controlled destruction and removal of plaque
results in particulate on the order of 10 microns or less. Thus,
unlike with previously known methods, there does not appear to be a
need for the down stream filters.
[0031] Traditional methods for removal of materials and exudate is
through the use of an aspiration mechanism which provides suction
through a suction passage which is part of the probe. These
traditional methods use irrigation fluid flow that is injected into
the site where the procedure is being conducted, in conjunction
with aspiration to remove the tissue from the surgical site. As
discussed above, however, providing both irrigation and aspiration
to the surgical site has, in prior art apparatuses, resulted in a
probe of relatively large cross-sectional profile, and therefore
that the treatment apparatus be substantially larger than the
ultrasonic probe needed for conducting the procedure. These prior
art apparatuses used concentric tubes wherein the irrigant is
normally provided through a central core of the probe and the
aspirant is provided through an outer concentric tube and
lumen.
[0032] Prior art apparatuses also maintain a strict orientation of
the suction and the irrigation mechanism, such that the inner and
outer lumens for irrigation and aspiration remain in a fixed
position relative to one another, generally in a position closely
adjacent the area of treatment. Additionally, if the probe is
turned into an aspiration system, a problem arises in that the only
location for fluid flow is at the tip of the probe. As a result,
all the pressure (suction force) is focused there at this point
within the vascular tree. Because of the tortuous nature of the
vessels, single point suction tends to either clog or cause minor
damage to the vessel.
[0033] One of the means of irrigation and aspiration in the present
invention is to drill small holes or fenestrations along the length
of the probe. Such fenestrations are strategically placed at
specific points of minimal stress due to the transverse cavitation.
The use of fenestrations provides additional benefits. For example,
in irrigation mode there is less of a focal pressure point out of
which fluid is blown. Instead, fenestrations allow for relatively
diffuse irrigation along and around a length of the probe.
Similarly, as for aspiration, by allowing suction to occur along
the length of the probe, the suction pattern is greater. Among
other possible benefits, this helps to prevent damage to the vessel
wall and results in relatively more complete aspiration because of
the larger suction pattern.
[0034] Thus, the irrigation lumen does not extend beyond the
suction lumen (i.e., there is no movement of the lumens relative to
one another) and the suction is designed to pick up any fluid
and/or tissue remnants within the defined distance between the two
lumens. The present invention, which uses grooves or channels on
the outside of the probe for aspiration, or very small diameter
hollow probes (.about.30 micron ID) allows for the distance between
the irrigation and aspiration lumens to be varied, thereby allowing
a reduced cross-sectional profile of the instrument inserted into
the patient's body. In the present invention, an axially movable
aspirating catheter or sheath may move along the length of the
probe, to thereby vary the position of the aspiration lumen
relative to the probe tip and the irrigation lumen or lumens.
Central aspiration within hollow probes--especially those that are
.about.0.020 in. diameter or smaller--allows for a flexible probe
as well. This allows for the aspiration lumen, and the associated
aspiration structure--except for the grooves or channels on the
probe--to be located outside the patient's body.
[0035] In the application of the ultrasonic energy of the present
invention the probe diameter is substantially smaller than that of
traditional ultrasonic probes, and therefore is ideally designed
for minimally invasive procedures. The present invention therefore
relates to the application of small diameter probes, which can be
inserted into a small diameter body vessel to thereafter use a
cavitational effect to remove plaque. In order to increase the area
of treatment which is effective in the small probe of the present
invention, the irrigation lumens can be transverse to the axis of
the probe, i.e., can open on the sides of the probe body. In this
way, the maximum area of the probe tip is used to provide
ultrasonic treatment and cavitational energy.
[0036] The probes used with the present invention are shaped to
allow easy insertion, and so that they are not sharp so as to
present the risk of tissue damage during insertion. The probes
preferably include a taper that accommodates the insertion of the
probe into the tissue through the application of the ultrasonic
energy, wherein the energy is amplified through the transition from
a larger mass to a smaller mass. The tapered shape of the probe,
usually that of a cone, sphere, or hemisphere, ovoid tear drop
shape is particularly useful in surgical applications as the tissue
rent or tear caused by the insertion of the probe into the vessel
is usually caused via a mechanical action of a needle or other
sharp object, and not usually as a result of ultrasonic drilling of
the probe. Irrespective, as the energy deposited by the probe is
very low, and the round shape of the probe tip is formed, there is
no additional energy departed upon the vessel to cause it to tear
or that would otherwise cause a tear to expand beyond that of the
initial penetration point.
[0037] Similarly, the tapered shape of the probe minimizes the
overall size of the penetration point through the tissue, as the
ultrasonic energy is focused at the extreme length of the flexible
portion of the probe. The energy emanates for a defined length
along this portion of the probe, and diminishes in transverse
amplitude once specific transition barriers and shapes have been
induced into the design.
[0038] In accordance with a preferred embodiment of the invention,
an ultrasonic medical device comprises an ultrasonic vibration
generator that generates vibration along its longitudinal axis. The
ultrasonic vibration is transmitted through an ultrasonic coupler
and a series of transformer sections that amplify the ultrasonic
vibration. A flexible member is coupled to the distal end of the
transformer sections, and is thus supplied with a longitudinal
vibration at its base by the transformer sections. The flexible
member is designed so that it converts the longitudinal vibration
into a standing wave that runs along the length of the flexible
member. The standing wave produces a series of nodes and anti-nodes
along the length of the flexible member. Each of the anti-nodes
produces cavitation in fluids in contact with the probe. The
cavitation of the fluids causes destruction of adjacent plaque.
Thus, in this manner, the entire length of the flexible member
becomes a working surface that may be utilized for destroying
plaque.
[0039] The invention, therefore, includes a number of advantageous
features which make it particularly useful for minimally-invasive
procedures. First, it allows for the application of ultrasonic
energy to plaque, such as that which lines the carotid artery, via
a small diameter probe that is able to traverse a vessel or
opening, and which can remove plaque through the action of
cavitation on the plaque. Second, the invention has the ability to
make a small penetration into and through a body vessel, or to
create a small penetration in the body, and thereafter allows the
probe to be directed to the blood vessel to be treated, such as the
carotid artery. Third, the invention allows, through the action of
cavitation and a movement by the surgeon of the ultrasonic tip
throughout the treated area, the creation of a large cavity, so
that the cavity is larger than the size of the probe. Fourth, the
apparatus of the invention may be designed with a stiffened outer
member, within which a softer malleable or bendable member resides,
which therefore allows the ability to insert a probe into the body,
without extreme torsion and bending on the anatomy. This
malleability also allows the probe to be bent or articulated so
that it can reach areas which are not axially aligned with the
lumen or passage into which the probe is inserted. Fifth, the
invention allows the ability to remove debris at the point of the
procedure. Sixth, the present invention allows the ability to
irrigate the cavitation site via the ultrasonic probe--both when
the probe is rigid and when the probe is flexible and malleable.
Seventh, the present invention allows the use of ultrasonic energy
which is applied to plaque and fatty deposits selectivity, because
it uses energy in a frequency range -20 kHz to 80 kHz--such that it
imparts the energy specifically to hydrated (water-laden) plaque
and fatty deposits. As a result, there is little or no energy
imparted to the arterial wall itself. This selectivity in the
application of energy therefore avoids damage to the artery.
Eighth, the present invention allows the use of bending, flexing or
articulated probe, which limits the amount of force placed upon the
probe as it is advanced forwards. In this way, the force applied on
the probe is decreased through the bend, i.e., less pressure is
imparted on the tip of the probe, thereby decreasing the potential
for accidental penetration of tissue by the probe through pure
physical force. That disadvantageous result might have occurred in
a similar application of force using a straight probe into the
prostatic capsule.
[0040] An important feature of the present invention is that it is
non-thermal. The use of a procedure in which heat or thermal energy
is not used is important, and the present invention produces very
low heat, and the excursion of heat is limited to the immediate
area associated with the acoustic wave that is ablating the plaque.
The present invention, through the use of ultrasonic energy
together with irrigation and aspiration, can produce treatment
within a range of normal body temperature in the treated area of
.+-.3.degree. C. Furthermore, collateral irrigation causes the
residual tissue to remain within a narrow range around normal
physiologic temperatures throughout the procedure of the present
invention. Due to the lack of heat in the present invention, and
the immediacy of the plaque removal process, the residual tissue
exhibits remarkably little to no inflammatory response, thereby
producing little fibro intimal hyperplasia edema (swelling) of the
vessel. As such, loss of vessel patency or vessel internal diameter
is avoided.
[0041] The ultrasonic tip of the present invention, because it uses
cavitation as the mode of plaque removal, does not have to be
sharp. Rather, soft flexible shapes are preferred because
penetration is caused by a mechanical penetration of the vessel not
cavitation, and not by the physical shape of the probe. Therefore,
the tip can be smooth and small, making insertion less traumatic
and less prone to residual tissue damage.
[0042] In the present invention, the location of the probe can be
determined via the use of a medical visual ultrasound device. Once
the probe is located, the bending or flexure of the probe tip can
be monitored. This enhances the physician's ability to see and
direct the ultrasonic probe during treatment, and is the result of
the high frequency vibrations at the tip.
[0043] The ultrasonic energy to be applied to a particular
treatment site is a function of the amplitude and frequency. In
general, the throw rate or amplitude of the energy supplied by the
apparatus of the present invention is in the range of 150 microns
to 350 microns, and the frequency in the range of 20-80 kHz. Larger
probes will use the lower frequencies while smaller probes will use
the higher frequencies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 is a side elevation view of handle of the ultrasonic
treatment apparatus of the present invention;
[0045] FIG. 2 is a perspective view of a first embodiment of the
ultrasonic treatment apparatus of the present invention;
[0046] FIG. 3 is a side elevation view of the embodiment of FIG.
2;
[0047] FIG. 4 is a perspective view of one embodiment of an
ultrasonic tip of the present invention,
[0048] FIG. 5 is a perspective view of a second embodiment of an
ultrasonic tip of the present invention;
[0049] FIG. 6 is a side elevation view of a second embodiment of an
ultrasonic treatment apparatus of the present invention;
[0050] FIG. 7 is a radial cross-sectional view through an
embodiment of an ultrasonic probe of the present invention;
[0051] FIG. 8 is an axial cross-section of one embodiment of an
ultrasonic treatment probe of the present invention;
[0052] FIG. 9 is an axial cross-section of one embodiment of an
ultrasonic treatment probe of the present invention;
[0053] FIG. 10 is a cross-sectional view of a patient's carotid
artery during a debulking operation using one embodiment of the
present invention; and
[0054] FIG. 11 is a cross-sectional view of a patient's carotid
artery during a debulking operation as shown in FIG. 10 after
plaque has been ablated.
DETAILED DESCRIPTION
[0055] FIG. 1 shows an embodiment of a handle 5 used with the
present invention. The handle 5 is composed of an irrigation
fitting or luer 2, a grasping area 3, and a probe fitting 4. The
irrigation fitting or luer 2 is configured for connection with a
flexible tube which is in turn connected to a source of pressurized
irrigating fluid, such as water. The grasping area 3 is shaped for
grasping by the hand of the apparatus operator, such as a surgeon,
and may include one or more trigger or button mechanisms for
activating and deactivating various features of the apparatus, such
as suction, irrigation, power, etc.
[0056] FIGS. 2 and 3 show an embodiment of the ultrasonic treatment
apparatus 1 of the present invention, which includes the handle 5
shown in FIG. 1. The ultrasonic treatment apparatus 1 includes an
ultrasonic probe 6 with an ultrasonic probe tip 7. The ultrasonic
probe 6 is axially movably mounted within an aspiration sheath or
catheter 70, so that the probe tip 7 may move axially inwardly and
outwardly relative to the distal end of the aspiration sheath or
catheter 70. The ultrasonic probe 6 and aspiration sheath or
catheter 70 are both mounted in an aspiration shroud 9, which
includes an aspiration shroud housing 8. Within aspiration shroud
housing 8 is an aspiration end 10 of aspiration sheath or catheter
70, which transmits suction or negative pressure to the interior of
aspiration sheath or catheter 70. The aspiration end surrounds, and
is sealed against, the ultrasonic transmission element 11 which
extends to, and forms a proximal portion of, the ultrasonic probe
6. The aspiration end 10 is connected to an aspiration fitting or
luer 13. The aspiration fitting or luer 13 is configured for
connection with a flexible tube which is in turn connected to a
source of reduced pressure. The aspiration sheath is slidable
relative to handle 5 and probe 6, thereby allowing the distance
between the ultrasonic tip 7 and the distal end of the aspiration
sheath or catheter 70 to be varied. An actuation mechanism 12 may
extend from the aspiration shroud 9 to the handle 5, and is
surrounded by suitable covers 14 and 15.
[0057] FIG. 4 shows an embodiment of an ultrasonic probe 16 and
ultrasonic probe tip 17 of the present invention. The body of the
ultrasonic probe 16 in the embodiment of FIG. 4 is preferably
slightly tapered from the distal end to the proximal end. The
ultrasonic tip 17 is in the form of a ball-shaped projection from
the end of the ultrasonic probe 16. This shape of the ultrasonic
tip 17 eliminates any sharp edges or surfaces on the tip which
could result in damage to tissue during insertion, treatment or
removal. Similarly, although not shown in the Figs., the ultrasonic
tip 17 may take on a variety of other shapes. For instance, the tip
can be bent into a d-shape. As tip 17 is constructed from a
flexible wire--which can be bent and shaped without affect to the
energy that is distributed to the probe--tip 17 can be configured
such that it conforms to a pre-defined shape once within the
lumen.
[0058] The ultrasonic tip 17, at its distal surface, includes one
or more irrigation ports 18. The irrigation ports 18 are all
connected to an internal irrigation passage, preferably centrally
located in the ultrasonic tip 17 and the ultrasonic probe 16.
Although not shown in FIG. 4, the ultrasonic probe 16 could have,
extending along its length, one or more grooves or channels for
aspiration, as discussed in more detail below.
[0059] FIG. 5 shows a second embodiment of the ultrasonic probe
aspiration sheath or catheter of the present invention. The
embodiment of FIG. 5 is particularly useful for treating conditions
wherein the treatment area dangles or is loose; in particular, the
embodiment of FIG. 5 is useful in gynecological treatments. In the
embodiment of FIG. 5, the tip 75 of the aspiration sheath or
catheter 70 is a rounded end. The aspiration sheath or catheter 70
includes a lateral slot or opening 19 on one side. The ultrasonic
probe 23, with an ultrasonic tip 21 which may include a bevel 20 is
mounted for axial sliding movement within the aspiration sheath or
catheter 70. At least one aspiration passage 23 is created in the
space between the ultrasonic probe 22 and the interior wall of the
aspiration sheath or catheter 70. Accordingly, as suction is
applied to the aspiration fitting or luer 13, a negative pressure
or suction is formed at the aspiration passage 23, to draw away any
destroyed or cavitated plaque and any residual or irrigation
fluid.
[0060] At the proximal end of the tip 75 is a grasping surface or
backstop 76. This grasping surface or backstop 76 serves as an
opposed surface to the ultrasonic tip 21, thereby allowing dangling
or loose treatment areas to be grasped during treatment. In
operation, the aspiration sheath or catheter 70 is directed to a
treatment area, until the dangling or loose treatment area falls
into the lateral slot or opening 19. During this step, the
ultrasonic probe 23 is in a retracted position, as shown in FIG. 5.
Thereafter, the ultrasonic probe 23 is advanced axially outward,
until the dangling or loose treatment area is clamped between the
ultrasonic tip 21 and the grasping surface or backstop 76.
Thereafter, the ultrasonic vibration generator is activated, such
that ultrasonic energy is transmitted to the ultrasonic tip 21. As
a result, the grasped treatment area is treated using ultrasonic
energy and the resulting cavitation.
[0061] FIGS. 7 and 9 show a radial cross-section through an
ultrasonic probe 6 according to one embodiment of the invention.
The probe 6 includes a central passage 62 which is connected to the
irrigation fitting or luer 2. The central passage 62 terminates in
two lateral lumens 61, located on the sides of the probe 6. The
central passage 62 is used to transmit an irrigating fluid to the
area around the ultrasonic tip 7, to thereby regulate the
temperature of the treatment site. The irrigation fluid, together
with the cavitational action of the ultrasonic tip 7, allows the
treatment site to be regulated to a temperature of .+-.3.degree. C.
of normal body temperature. Furthermore, because the lumens 61 do
not pass through the ultrasonic tip 7, the effective area of
treatment of the ultrasonic tip 7 is increased.
[0062] As shown in FIGS. 7 and 9, the outer surface of the
ultrasonic probe 6 includes one or more grooves or channels 60.
These grooves or channels, although straight in FIG. 8, could
spiral along the length of the ultrasonic probe 6. The grooves or
channels 60 are used to aspirate fluid and tissue fragments from
the treatment site, as the result of negative pressure or suction
applied at the proximal ends of the grooves or channels 60. As a
result, fluid and tissue fragments travel down the grooves or
channels 60 and away from the treatment site, thereby preventing
fluid and fragments from interfering with the ultrasonic processing
and cavitation of additional tissue.
[0063] FIGS. 6 and 8 show features of an ultrasonic treatment
apparatus of another embodiment of the present invention. As shown
in FIG. 6, the ultrasonic treatment apparatus has an ultrasonic
probe 6 with an ultrasonic tip 7. The ultrasonic probe 6 is housed
in, for slidable movement within, a flexible articulation sheath
70. The flexible articulation sheath 70 is, in turn, housed in, for
slidable movement within, a rigid sheath 80. Rigid sheath 80 is
connected to, for movement with, a retracting housing 90. The
retracting housing 90 is connected to a retracting trigger 94,
which is pivoted on the handle 5. The retracting housing 90 may
include an aspiration fitting or luer 13, which is configured for
connection with a flexible tube which is in turn connected to a
source of reduced pressure. As discussed in more detail below, the
aspiration fitting or luer 13 is connected to the interior of the
flexible articulation sheath 70.
[0064] An articulation trigger 91 may be housed on the retracting
housing 90. Articulation trigger 91 is connected to an articulation
wire 71 discussed in more detail below. A trigger 92 may also be
housed on the retracting housing 90. A cover 93 may cover
components between the retracting housing 90 and the handle 5.
[0065] FIG. 8 shows the details of the proximal end of the
ultrasonic apparatus of FIG. 6. The ultrasonic probe 6 may include
one or more grooves or channels 60 which are used to provide
aspiration to the area around the ultrasonic tip 7. One or more
irrigation lumens 61 may provide irrigating fluid to the area
around the ultrasonic tip 7. The ultrasonic probe 6, which, because
of its small cross-sectional profile and the material of which it
is constructed, is somewhat flexible so that it may be bent or
articulated. The ultrasonic probe 6 fits within, for axial
movement, the articulation sheath 70, which is made of a relatively
flexible and resilient material. The space 72 between the
ultrasonic probe 6 and the articulation sheath 70, together with
the grooves or channels 60, form aspiration passages. The
articulation sheath 70 may include, at one or more locations around
the circumference of the articulation shaft 70, one or more
embedded articulation wires 71, with a distal end affixed to the
articulation sheath 70. The proximal end of the articulation wire
71 is affixed to the articulation trigger 91. The articulation
sheath 70 is housed within, for axial movement, the rigid sheath
80. Rigid sheath 80 is made of a relatively rigid material.
[0066] When the rigid sheath 80 is slid back away from the distal
end of the articulation sheath 70, and the articulation wire 71 is
pulled axially inwardly by the articulation trigger 91, the
articulation sheath will bend or articulate in a bending or
articulation direction A. As a result, the ultrasonic probe 6 and
ultrasonic tip 7 will bend or articulate in articulation direction
A. In this way, the ultrasonic can be used to reach locations which
are not axially aligned with the lumen or vessel through which the
ultrasonic probe 6 is inserted.
[0067] FIGS. 10 and 11 show the manner in which the embodiment
shown in FIGS. 6 and 8 may be used to debulk the carotid
artery.
[0068] In a preferred embodiment of the invention, maximum
vibratory motion is not confined to the tip of the probe as in the
case of prior art ultrasonic instruments. Rather, the probe of the
invention is specially designed to provide a multiplicity of
so-called anti-nodes (i.e., points along the probe where maximum
vibration occur) at spaced intervals along the axial length of the
probe, in addition to the tip of the probe. This construction best
suits the method of the invention because removal of plaque 102 in
artery 100 will not be confined to those regions coming into
contact with the tip of the probe. Rather, as the probe is inserted
through artery 100, plaque 102 is removed in all areas adjacent to
the multiplicity of anti-nodes located along the entire length of
the probe. In this way, the apparatus of the invention allows for
removal of plaque 102 in accordance with the method of the
invention to be carried out most efficiently so that actual
treatment time is greatly reduced as compared to prior art
methods.
[0069] As shown in FIG. 11, the energy reduces plaque 102 (shown in
FIG. 10) to a particulate material 104 and simultaneously the probe
moves towards areas of greater mass within the lumen. The term
"plaque" is used herein to denote not only fatty deposits but any
other type of build-up that can cause or contribute to stenosis or
occlusion within a blood vessel, such as calcium deposits. This is
due to negative pressure gradients around and near the probe. The
probe can make contact with the inner surface of the vessel without
causing damage to the tissue. The probe is a non-fibro intimal
hyuperplasia causing device.
[0070] The mode of vibration of the ultrasound probe in the
apparatus of the invention differs from the axial mode of vibration
which is conventional in the prior art. Rather than vibrating
exclusively in the axial direction, the probe in the apparatus of
the present invention vibrates in a direction transverse to the
axial direction. Because of this transverse mode of vibration, the
probe of the invention removes plaque not just at those points
where the probe makes actual contact with the tissue, but also
typically in a region having a radius up to 1.0-1.5 mm around the
probe. Hence, the transverse mode of vibration of the probe used in
the present apparatus also contributes to the efficiency of the
method of the invention by expanding the coverage area around the
probe where tissue is removed.
[0071] In general, in order to increase the number of anti-nodes
occurring along the axial length of the probe, the vibration
frequency imparted to the probe should be increased. The frequency,
however, is not critical and a generator run at 20 kHz is generally
sufficient to provide for an effective number of anti-nodes along
the axial length of the probe. In addition, as will be appreciated
by those skilled in the art, it is possible to adjust the
dimensions of the probe, including diameter, length and location of
coupling to the ultrasonic energy source, in order to space the
anti-nodes at desired intervals.
[0072] An ultrasonic medical apparatus which operates in the
transverse mode and which is suitable for carrying out the method
of the present invention is disclosed in application Ser. No.
09/618,352, now U.S. Pat. No. 6,551,337, the disclosure of which is
incorporated herein by reference.
[0073] Thus, there is shown and described a unique design and
concept of an ultrasonic treatment device and method of its use.
While this description is directed to particular embodiments, it is
understood that those skilled in the art may conceive modifications
and/or variations to the specific embodiments shown and described
herein. Any such modifications or variations which fall within the
purview of this description are intended to be included as part of
the invention. It is understood that the description herein is
intended to be illustrative only and is not intended to be
limitative. Rather, the scope of the invention described herein is
limited only by the claims.
* * * * *
References