U.S. patent application number 17/182981 was filed with the patent office on 2021-06-17 for catheter with multiple ultrasound radiating members.
This patent application is currently assigned to EKOS CORPORATION. The applicant listed for this patent is EKOS CORPORATION. Invention is credited to TIM ABRAHAMSON, WM. GERRIT BARRERE, AMY COHEN, CURTIS GENSTLER, GEORGE KEILMAN, LEONARD R. OLIVER, NATALYA PESKIN, ROBERT L. WILCOX, RICHARD R. WILSON.
Application Number | 20210178140 17/182981 |
Document ID | / |
Family ID | 1000005418151 |
Filed Date | 2021-06-17 |
United States Patent
Application |
20210178140 |
Kind Code |
A1 |
WILSON; RICHARD R. ; et
al. |
June 17, 2021 |
CATHETER WITH MULTIPLE ULTRASOUND RADIATING MEMBERS
Abstract
A method of delivery ultrasonic energy and a therapeutic
compound to a treatment site and an ultrasonic catheter system are
disclosed. The ultrasonic catheter system comprises a tubular body
having a proximal end, a distal end and a treatment zone located
between the distal end and the proximal end, a fluid delivery
lumen, at least one ultrasound radiating element positioned in the
treatment zone, wiring electrically coupled to the at least one
ultrasound radiating element and extending through the tubular body
and terminating at a connector, and a control system comprising
external circuitry and an isolation pod that is configured to be
electrically connected to the connector, the isolation pod being
positioned between the tubular body and the external system and
comprising an isolation barrier and circuitry for driving the
ultrasound radiating element.
Inventors: |
WILSON; RICHARD R.;
(SEATTLE, WA) ; WILCOX; ROBERT L.; (BOTHELL,
WA) ; GENSTLER; CURTIS; (SNOHOMISH, WA) ;
ABRAHAMSON; TIM; (SEATTLE, WA) ; BARRERE; WM.
GERRIT; (LAKE FOREST PARK, WA) ; COHEN; AMY;
(SEATTLE, WA) ; KEILMAN; GEORGE; (SEATTLE, WA)
; OLIVER; LEONARD R.; (SEATTLE, WA) ; PESKIN;
NATALYA; (REDMOND, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EKOS CORPORATION |
BOTHELL |
WA |
US |
|
|
Assignee: |
EKOS CORPORATION
BOTHELL
WA
|
Family ID: |
1000005418151 |
Appl. No.: |
17/182981 |
Filed: |
February 23, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16112364 |
Aug 24, 2018 |
10926074 |
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17182981 |
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15207371 |
Jul 11, 2016 |
10080878 |
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16112364 |
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14196225 |
Mar 4, 2014 |
9415242 |
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15207371 |
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13431798 |
Mar 27, 2012 |
8696612 |
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14196225 |
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12762254 |
Apr 16, 2010 |
8167831 |
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13431798 |
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11643471 |
Dec 21, 2006 |
7727178 |
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12762254 |
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10309388 |
Dec 3, 2002 |
7220239 |
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11643471 |
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60336630 |
Dec 3, 2001 |
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60336744 |
Dec 3, 2001 |
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60394093 |
Jul 3, 2002 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/2202 20130101;
A61M 25/0029 20130101; A61M 25/0032 20130101; A61B 2017/22088
20130101; A61N 2007/0078 20130101; A61N 7/00 20130101; A61M 37/0092
20130101; A61B 2017/22084 20130101 |
International
Class: |
A61M 37/00 20060101
A61M037/00; A61B 17/22 20060101 A61B017/22; A61M 25/00 20060101
A61M025/00; A61N 7/00 20060101 A61N007/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED R & D
[0002] The invention was made with government support under Grant
No. NIH R44 HL057739 awarded by the National Institutes of Health.
The government has certain rights in the invention.
Claims
1. An isolation pod for use with an ultrasound system, the
isolation pod comprising: a catheter connector configured to be
electrically connected to an ultrasound catheter including at least
one ultrasound radiating element, the isolation pod configured to
be positioned between the ultrasound catheter and an external
system circuitry, the isolation pod including an isolation barrier
and circuitry for driving the ultrasound radiating element.
2. The isolation pod of claim 1, wherein the isolation pod is
configured to receive a radio frequency signal from the external
system circuitry.
3. The isolation pod of claim 2, wherein the isolation pod includes
a transformer for converting the radio frequency to a drive signal
for driving the ultrasound radiating element.
4. The isolation pod of claim 1, wherein the isolation pod includes
a transformer loop that is configured to measure leakage current
through the ultrasound catheter.
5. The isolation pod of claim 1, wherein the isolation pod includes
tuning circuitry that adjusts an input impedance based upon the
activation of an ultrasound transducer.
6. An ultrasonic catheter system comprising: a catheter having a
proximal end, a distal end and a treatment zone located between the
distal end and the proximal end; an inner core comprising at least
one ultrasound radiating element, the at least one ultrasound
radiating element being positioned within the treatment zone; a
control system comprising external circuitry and an isolation pod
that is configured to be electrically connected to the inner core,
the isolation pod being positioned between the catheter body and
the control system and comprising an isolation barrier and
circuitry for driving the ultrasound radiating element.
7. The ultrasonic catheter system of claim 6, wherein the external
circuitry provides a radio frequency signal to the isolation
pod.
8. The ultrasonic catheter system of claim 7, wherein the isolation
pod includes a transformer for converting the radio frequency to a
drive signal for driving the ultrasound radiating element.
9. The ultrasonic catheter system of claim 6, wherein the isolation
pod includes a transformer loop that is configured to measure
leakage current through the catheter.
10. The ultrasonic catheter system of claim 6, wherein the
isolation pod includes tuning circuitry that adjusts an input
impedance based upon the activation of an ultrasound
transducer.
11. The ultrasound catheter system of claim 6, wherein the inner
core comprises more than one ultrasound radiating elements.
12. The ultrasonic catheter system of claim 6, wherein the catheter
includes a memory device that stores information relating to the
catheter.
13. The ultrasonic catheter system of claim 6, wherein the catheter
includes a plurality of fluid delivery lumens defined within a wall
of the catheter and extending from the proximal end to the
treatment zone.
14. The ultrasonic catheter system of claim 6, wherein the catheter
includes a plurality of cooling fluid channels extending from the
proximal end to the treatment zone, the plurality of cooling fluid
channels being formed between an inner surface of the catheter and
an outer surface of the inner core.
15. An ultrasound system comprising: an ultrasound catheter having
a proximal end, a distal end and a treatment zone located between
the distal end and the proximal end, at least one ultrasound
radiating element positioned in the treatment zone, wiring coupled
to the at least one ultrasound radiating element and extending
through the ultrasound device and terminating at a connector; and a
control system comprising external circuitry and an isolation pod
that is configured to be electrically connected to the connector,
the isolation pod being positioned between the tubular body and the
external system circuitry and comprising an isolation barrier and
circuitry for driving the ultrasound radiating element.
16. The ultrasound system of claim 16, wherein the external
circuitry provides a radio frequency signal to the isolation
pod.
17. The ultrasound system of claim 16, wherein the isolation pod
includes a transformer for converting the radio frequency to a
drive signal for driving the ultrasound radiating element.
18. The ultrasound system of claim 15, wherein the isolation pod
includes a transformer loop that is configured to measure leakage
current through the ultrasound catheter.
19. The ultrasound system of claim 15, wherein the isolation pod
includes tuning circuitry that adjusts an input impedance based
upon the activation of an ultrasound transducer.
20. The ultrasound system of claim 15, wherein the ultrasound
catheter defines a fluid delivery lumen.
Description
PRIORITY APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/112,364, filed Aug. 24, 2018, now U.S. Pat.
No. 10,926,074, which is a continuation of U.S. patent application
Ser. No. 15/207,371, filed Jul. 11, 2016, now U.S. Pat. No.
10,080,878, which is a continuation of U.S. patent application Ser.
No. 14/196,225, filed Mar. 4, 2014, now U.S. Pat. No. 9,415,242,
which is a continuation of U.S. patent application Ser. No.
13/431,798, filed Mar. 27, 2012, now U.S. Pat. No. 8,696,612, which
is a continuation of U.S. patent application Ser. No. 12/762,254,
filed Apr. 16, 2010, now U.S. Pat. No. 8,167,831, which is a
divisional of U.S. patent application Ser. No. 11/643,471, filed
Dec. 21, 2006, now U.S. Pat. No. 7,727,178, which is a divisional
of U.S. patent application Ser. No. 10/309,388, filed Dec. 3, 2002,
now U.S. Pat. No. 7,220,239, which claims the benefit of U.S.
Provisional Patent Application No. 60/336,744, filed Dec. 3, 2001,
U.S. Provisional Patent Application No. 60/336,630, filed Dec. 3,
2001, and U.S. Provisional Patent Application No. 60/394,093, filed
Jul. 3, 2002. The entire disclosure of all of these priority
documents is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0003] The present invention relates generally to an ultrasonic
catheter and more specifically to an ultrasonic catheter configured
to deliver ultrasonic energy and a therapeutic compound to a
treatment site.
Description of the Related Art
[0004] Several medical applications use ultrasonic energy. For
example, U.S. Pat. Nos. 4,821,740, 4,953,565 and 5,007,438 disclose
the use of ultrasonic energy to enhance the effect of various
therapeutic compounds. An ultrasonic catheter can be used to
deliver ultrasonic energy and a therapeutic compound to a treatment
site in a patient's body. Such an ultrasonic catheter typically
includes an ultrasound assembly configured to generate ultrasonic
energy and a fluid delivery lumen for delivering the therapeutic
compound to the treatment site.
[0005] As taught in U.S. Pat. No. 6,001,069, such ultrasonic
catheters can be used to treat human blood vessels that have become
partially or completely occluded by plaque, thrombi, emboli or
other substances that reduce the blood carrying capacity of the
vessel. To remove or reduce the occlusion, the ultrasonic catheter
is used to deliver solutions containing dissolution compounds
directly to the occlusion site. Ultrasonic energy generated by the
ultrasound assembly enhances the therapeutic effect of the
dissolution compounds. For example, in one application of such an
ultrasonic catheter, an ultrasound-enhanced thrombolytic therapy
dissolves blood clots in arteries and veins in the treatment of
diseases such as peripheral arterial occlusion or deep vein
thrombosis. In such applications, ultrasonic energy enhances
thrombolysis with agents such as urokinase, tissue plasminogen
activator ("TPA") and the like.
[0006] Ultrasonic catheters can also be used to enhance gene
therapy at a treatment site within the patient's body. For example,
U.S. Pat. No. 6,135,976 discloses an ultrasonic catheter having one
or more expandable sections capable of occluding a section of a
body lumen, such as a blood vessel. A gene therapy composition is
then delivered to the occluded vessel through the catheter fluid
delivery lumen. Ultrasonic energy generated by the ultrasound
assembly is applied to the occluded vessel, thereby enhancing the
delivery of a genetic composition into the cells of the occluded
vessel.
[0007] Ultrasonic catheters can also be used to enhance delivery
and activation of light activated drugs. For example, U.S. Pat. No.
6,176,842 discloses methods for using an ultrasonic catheter to
treat biological tissues by delivering a light activated drug to
the biological tissues and exposing the light activated drug to
ultrasound energy.
SUMMARY OF THE INVENTION
[0008] In certain medical procedures, it is desirable to provide
ultrasonic energy along a substantial length of a body lumen. For
example, long segment peripheral arterial occlusions, such as those
in the arteries of the leg, may have an axial length in the range
of 10 to 50 cm. To date, it has been difficult to design an
ultrasonic catheter capable of efficiently applying ultrasound
energy over such lengths.
[0009] One method for emitting ultrasonic energy over such lengths
is to provide the ultrasonic catheter with a plurality of
ultrasonic transducers spaced along a distal region of the
catheter. Such an arrangement faces several technical hurdles. For
example, because the ultrasonic transducers are relatively rigid,
the catheter may become too inflexible to be navigated through the
lumens of the patient's body. One solution is to use smaller
transducers. However, smaller transducers may not be capable of
producing sufficient energy at the proper frequency to enhance the
therapeutic effect of a therapeutic agent.
[0010] Another solution is disclosed in U.S. Pat. No. 6,296,610.
This patent discloses a catheter with a plurality of transducers
that are moved back and forth within the catheter through the
treatment zone. However, this arrangement is generally undesirable
because it requires a translation system for moving the ultrasonic
elements within the catheter.
[0011] Additionally, for ease of manufacturing and reduced costs,
it is generally desirable to use ultrasonic transducers that are in
the form of rectangular bars as compared to, for example,
cylindrical transducers. However, such arrangements should still
generate a therapeutically effective ultrasonic energy field.
[0012] A need, therefore, exists for an improved ultrasonic
catheter capable of providing ultrasonic energy over a substantial
length of a body lumen with little or no movement of the ultrasonic
elements within the patient during treatment. Such a catheter
preferably uses flat rectangular ultrasonic transducers.
[0013] As such, according to one embodiment of the present
invention, a catheter system for delivering ultrasonic energy and a
therapeutic compound to a treatment site within a body lumen
comprises a tubular body. The tubular body has a proximal end, a
distal end and an energy delivery section positioned between the
proximal end and the distal end. The catheter system further
comprises a fluid delivery lumen extending at least partially
through the tubular body. The fluid delivery lumen has at least one
outlet in the energy delivery section. The catheter system further
comprises an inner core configured for insertion into the tubular
body. The inner core comprises an elongate electrical conductor
having a plurality of flattened regions. Each flattened region has
a first flat side and a second flat side opposite the first flat
side. The inner core further comprises a plurality of ultrasound
radiating members mounted in pairs to the flattened regions of the
elongate electrical conductor. A first ultrasound radiating member
is mounted to the first flat side of the elongate electrical
conductor, and a second ultrasound radiating member is mounted to
the second flat side of the elongate electrical conductor. The
inner core further comprises wiring such that a voltage can be
applied from the elongate electrical conductor across the first and
second ultrasound radiating members. The first and second
ultrasound radiating members can be driven simultaneously.
[0014] According to another embodiment of the present invention, a
catheter system for delivering ultrasonic energy to a treatment
site comprises a tubular body. The tubular body has a proximal end,
a distal end and a treatment zone located between the distal end
and the proximal end. The catheter system further comprises an
ultrasonic assembly positioned within the treatment zone. The
ultrasonic assembly comprises an electrical conductor and an
ultrasonic transducer pair. The ultrasonic transducer pair includes
a first ultrasound transducer having a first portion and a second
ultrasound transducer having a second portion. The first portion of
the first transducer and the second portion of the second
transducer face each other and are electrically coupled to the
electrical conductor.
[0015] According to another embodiment of the present invention a
catheter system for delivering ultrasonic energy to a treatment
site comprises a tubular body. The tubular body has a proximal end,
a distal end and a treatment zone located between the distal and
proximal ends. The catheter system further comprises an ultrasonic
assembly positioned within the treatment zone. The ultrasonic
assembly comprises an electrical conductor and an ultrasonic
transducer pair. The ultrasonic transducer pair includes a
rectangular solid first ultrasonic element and a rectangular solid
second ultrasonic element. The first and second ultrasonic elements
are mounted on opposite sides of the electrical conductor.
[0016] According to another embodiment of the present invention, an
apparatus comprises an elongate tubular body having a fluid
delivery lumen. The apparatus further comprises an inner core
configured for insertion into the tubular body. The inner core
comprises a common wire and a plurality of ultrasound radiating
members. The plurality of ultrasound radiating members are
positioned and electrically coupled to the common wire in pairs.
The apparatus further comprises a control system configured to
drive each pair of ultrasound radiating members.
[0017] According to another embodiment of the present invention, a
method of delivering ultrasonic energy and a therapeutic compound
to a treatment site comprises providing a catheter with a plurality
of ultrasound radiating members. The plurality of ultrasound
radiating members are allocated into electrical groups comprising
more than one ultrasound radiating member. The method further
comprises independently driving each group of ultrasonic radiating
members. The method further comprises delivering the therapeutic
compound through the catheter to the treatment site.
[0018] According to another embodiment of the present invention, an
ultrasonic catheter comprises a tubular body. The tubular body has
a proximal end, a distal end and a treatment zone located between
the distal end and the proximal end. The ultrasonic catheter
further comprises a plurality of fluid delivery lumens defined
within the tubular body. The ultrasonic catheter further comprises
an inner core comprising at least one ultrasound radiating element.
The ultrasonic catheter further comprises a plurality of cooling
fluid channels defined between at least an inner surface of the
tubular body and an outer surface of the inner core. Each cooling
fluid channel is positioned generally radially between two fluid
delivery lumens.
[0019] According to another embodiment of the present invention, an
ultrasonic catheter system comprises a tubular body. The tubular
body has a proximal end, a distal end and a treatment zone located
between the distal end and the proximal end. The ultrasonic
catheter system further comprises a fluid delivery lumen. The
ultrasonic catheter system further comprises at least one
ultrasound radiating element positioned in the treatment zone. The
ultrasonic catheter system further comprises wiring electrically
coupled to the at least one ultrasound radiating element. The
wiring extends through the tubular body and terminates at a
connector. The ultrasonic catheter system further comprises a
control system. The control system comprises external circuitry and
an isolation pod. The isolation pod is configured to be
electrically connected to the connector. The isolation pod is also
positioned between the tubular body and the external system. The
isolation pod comprises an isolation barrier and circuitry for
driving the ultrasound radiating element.
[0020] According to another embodiment of the present invention, an
ultrasonic catheter comprises a tubular body. The tubular body has
a proximal end, a distal end and a treatment zone located between
the distal end and the proximal end. The ultrasonic catheter
further comprises at least one fluid delivery lumen incorporated
into the tubular body. The ultrasonic catheter further comprises a
plurality of ultrasound radiating members mounted within an inner
core. The inner core is positioned within the tubular body such
that at least one of the ultrasound radiating members is located
within the treatment zone. The ultrasonic catheter further
comprises means for independently driving each of the ultrasound
transducers.
[0021] For purposes of summarizing the invention and the advantages
achieved over the prior art, certain objects and advantages of the
invention have been described above. It is to be understood that
not necessarily all such objects or advantages may be achieved in
accordance with any particular embodiment of the invention. Thus,
for example, those skilled in the art will recognize that the
invention may be embodied or carried out in a manner that achieves
or optimizes one advantage or group of advantages as taught herein
without necessarily achieving other objects or advantages as may be
taught or suggested herein.
[0022] All of these embodiments are intended to be within the scope
of the invention herein disclosed. These and other embodiments of
the present invention will become readily apparent to those skilled
in the art from the following detailed description of the preferred
embodiments having reference to the attached figures, the invention
not being limited to any particular preferred embodiment(s)
disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic illustration of an ultrasonic catheter
configured for insertion into large vessels of the human body.
[0024] FIG. 2 is a cross-sectional view of the ultrasonic catheter
of FIG. 1 taken along line 2-2.
[0025] FIG. 3 is a schematic illustration of an elongate inner core
configured to be positioned within the central lumen of the
catheter illustrated in FIG. 2.
[0026] FIG. 4 is a cross-sectional view of the elongate inner core
of FIG. 3 taken along line 4-4.
[0027] FIG. 5 is a schematic wiring diagram illustrating a
preferred technique for electrically connecting five groups of
ultrasound radiating members to form an ultrasound assembly.
[0028] FIG. 6 is a schematic wiring diagram illustrating a
preferred technique for electrically connecting one of the groups
of FIG. 5.
[0029] FIG. 7A is a schematic illustration of the ultrasound
assembly of FIG. 5 housed within the inner core of FIG. 4.
[0030] FIG. 7B is a cross-sectional view of the ultrasound assembly
of FIG. 7A taken along line 7B-7B.
[0031] FIG. 7C is a cross-sectional view of the ultrasound assembly
of FIG. 7A taken along line 7C-7C.
[0032] FIG. 7D is a side view of an ultrasound assembly center wire
twisted into a helical configuration.
[0033] FIG. 8 illustrates the energy delivery section of the inner
core of FIG. 4 positioned within the energy delivery section of the
tubular body of FIG. 2.
[0034] FIG. 9 illustrates a wiring diagram for connecting a
plurality of temperature sensors with a common wire.
[0035] FIG. 10 is a block diagram of a feedback control system for
use with an ultrasonic catheter.
[0036] FIG. 11A is a side view of a treatment site.
[0037] FIG. 11B is a side view of the distal end of an ultrasonic
catheter positioned at the treatment site of FIG. 11A.
[0038] FIG. 11C is a cross-sectional view of the distal end of the
ultrasonic catheter of FIG. 11B positioned at the treatment site
before a treatment.
[0039] FIG. 11D is a cross-sectional view of the distal end of the
ultrasonic catheter of FIG. 11C, wherein an inner core has been
inserted into the tubular body to perform a treatment.
[0040] FIG. 12 is a circuit diagram of an isolation pod.
[0041] FIG. 13 illustrates the connection of ultrasound radiating
members within a catheter to an isolation pod.
[0042] FIG. 14 illustrates a selective activation of ultrasound
radiating members within a catheter.
[0043] FIG. 15 illustrates a second selective activation of
ultrasound radiating members within a catheter.
[0044] FIG. 16 illustrates a third selective activation of
ultrasound radiating members within a catheter.
[0045] FIG. 17 illustrates one embodiment for connecting ultrasound
radiating members within a catheter to an isolation pod.
[0046] FIG. 18 illustrates a second embodiment for connecting
ultrasound radiating members within a catheter to an isolation
pod.
[0047] FIG. 19 illustrates the connection of temperature sensors
within a catheter to an isolation pod.
[0048] FIG. 20 is a cross-sectional view of a catheter
connector.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0049] As described above, it is desired to provide an ultrasonic
catheter having various features and advantages. Examples of such
features and advantages include the ability to apply ultrasonic
energy to a treatment site. In another embodiments, the catheter
has the ability to deliver a therapeutic compound to the treatment
site. Preferred embodiments of an ultrasonic catheter having
certain of these features and advantages are described herein.
Methods of using such an ultrasonic catheter are also described
herein.
[0050] The ultrasonic catheters described herein can be used to
enhance the therapeutic effects of therapeutic compounds at a
treatment site within a patient's body. As used herein, the term
"therapeutic compound" refers broadly, without limitation, to a
drug, medicament, dissolution compound, genetic material or any
other substance capable of effecting physiological functions.
Additionally, any mixture comprising any such substances is
encompassed within this definition of "therapeutic compound", as
well as any substance falling within the ordinary meaning of these
terms. The enhancement of the effects of therapeutic compounds
using ultrasonic energy is described in U.S. Pat. Nos. 5,318,014,
5,362,309, 5,474,531, 5,628,728, 6,001,069 and 6,210,356, the
entire disclosure of which are hereby incorporated by herein by
reference. Specifically, for applications that treat human blood
vessels that have become partially or completely occluded by
plaque, thrombi, emboli or other substances that reduce the blood
carrying capacity of a vessel, suitable therapeutic compounds
include, but are not limited to, an aqueous solution containing
Heparin, Uronkinase, Streptokinase, TPA and BB-10153 (manufactured
by British Biotech, Oxford, UK).
[0051] Certain features and aspects of the ultrasonic catheters
disclosed herein may also find utility in applications where the
ultrasonic energy itself provides a therapeutic effect. Examples of
such therapeutic effects include preventing or reducing stenosis
and/or restenosis; tissue ablation, abrasion or disruption;
promoting temporary or permanent physiological changes in
intracellular or intercellular structures; and rupturing
micro-balloons or micro-bubbles for therapeutic compound delivery.
Further information about such methods can be found in U.S. Pat.
Nos. 5,261,291 and 5,431,663, the entire disclosure of which are
hereby incorporated by herein by reference.
[0052] The ultrasonic catheters described herein are configured for
applying ultrasonic energy over a substantial length of a body
lumen, such as, for example, the larger vessels located in the leg.
However, it should be appreciated that certain features and aspects
of the present invention may be applied to catheters configured to
be inserted into the small cerebral vessels, in solid tissues, in
duct systems and in body cavities. Additional embodiments that may
be combined with certain features and aspects of the embodiments
described herein are described in U.S. patent application, Attorney
Docket EKOS.026A, entitled "Ultrasound Assembly For Use With A
Catheter" and filed Nov. 7, 2002, the entire disclosure of which is
hereby incorporated herein by reference.
[0053] With initial reference to FIG. 1 schematically illustrates
an ultrasonic catheter 10 configured for use in the large vessels
of a patient's anatomy. For example, the ultrasonic catheter 10
illustrated in FIG. 1 can be used to treat long segment peripheral
arterial occlusions, such as those in the vascular system of the
leg.
[0054] As illustrated in FIG. 1, the ultrasonic catheter 10
generally comprises a multi-component, elongate flexible tubular
body 12 having a proximal region 14 and a distal region 15. The
tubular body 12 includes a flexible energy delivery section 18
located in the distal region 15 of the catheter 10. The tubular
body 12 and other components of the catheter 10 can be manufactured
in accordance with any of a variety of techniques well known in the
catheter manufacturing field. Suitable materials and dimensions can
be readily selected based on the natural and anatomical dimensions
of the treatment site and on the desired percutaneous access
site.
[0055] For example, in a preferred embodiment the proximal region
14 of the tubular body 12 comprises a material that has sufficient
flexibility, kink resistance, rigidity and structural support to
push the energy delivery section 18 through the patient's
vasculature to a treatment site. Examples of such materials
include, but are not limited to, extruded polytetrafluoroethylene
("PTFE"), polyethylenes ("PE"), polyamides and other similar
materials. In certain embodiments, the proximal region 14 of the
tubular body 12 is reinforced by braiding, mesh or other
constructions to provide increased kink resistance and pushability.
For example, nickel titanium or stainless steel wires can be placed
along or incorporated into the tubular body 12 to reduce
kinking.
[0056] In an embodiment configured for treating thrombus in the
arteries of the leg, the tubular body 12 has an outside diameter
between about 0.060 inches and about 0.075 inches. In another
embodiment, the tubular body 12 has an outside diameter of about
0.071 inches. In certain embodiments, the tubular body 12 has an
axial length of approximately 105 centimeters, although other
lengths may by appropriate for other applications.
[0057] The energy delivery section 18 of the tubular body 12
preferably comprises a material that is thinner than the material
comprising the proximal region 14 of the tubular body 12 or a
material that has a greater acoustic transparency. Thinner
materials generally have greater acoustic transparency than thicker
materials. Suitable materials for the energy delivery section 18
include, but are not limited to, high or low density polyethylenes,
urethanes, nylons, and the like. In certain modified embodiments,
the energy delivery section 18 may be formed from the same material
or a material of the same thickness as the proximal region 18.
[0058] In certain embodiments, the tubular body 12 is divided into
at least three sections of varying stiffness. The first section,
which preferably includes the proximal region 14, has a relatively
higher stiffness. The second section, which is located in an
intermediate region between the proximal region 14 and the distal
region 15 of the tubular body 12, has a relatively lower stiffness.
This configuration further facilitates movement and placement of
the catheter 10. The third section, which preferably includes the
energy delivery section 18, is generally lower stiffness than the
second section in spite of the presence of the ultrasound radiating
members 40.
[0059] FIG. 2 illustrates a cross section of the tubular body 12
taken along line 2-2 in FIG. 1. In the embodiment illustrated in
FIG. 2, three fluid delivery lumens 30 are incorporated into the
tubular body 12. In other embodiments, more or fewer fluid delivery
lumens can be incorporated into the tubular body 12. The
arrangement of the fluid delivery lumens 30 preferably provides a
hollow central lumen 51 passing through the tubular body 12. The
cross-section of the tubular body 12, as illustrated in FIG. 2, is
preferably substantially constant along the length of the catheter
10. Thus, in such embodiments, substantially the same cross-section
is present in both the proximal region 14 and the distal region 15
of the catheter 10, including the energy delivery section 18.
[0060] In certain embodiments, the central lumen 51 has a minimum
diameter greater than about 0.030 inches. In another embodiment,
the central lumen 51 has a minimum diameter greater than about
0.037 inches. In one preferred embodiment, the fluid delivery
lumens 30 have dimensions of about 0.026 inches wide by about
0.0075 inches high, although other dimensions may be used in other
applications.
[0061] As described above, the central lumen 51 preferably extends
through the length of the tubular body 12. As illustrated in FIG.
1, the central lumen 51 preferably has a distal exit port 29 and a
proximal access port 31. The proximal access port 31 forms part of
the backend hub 33, which is attached to the proximal region 14 of
the catheter 10. The backend hub preferably further comprises
cooling fluid fitting 46, which is hydraulically connected to the
central lumen 51. The backend hub 33 also preferably comprises a
therapeutic compound inlet port 32, which is in hydraulic
connection with the fluid delivery lumens 30, and which can be
hydraulically coupled to a source of therapeutic compound via a hub
such as a Luer fitting.
[0062] The central lumen 51 is configured to receive an elongate
inner core 34 of which a preferred embodiment is illustrated in
FIG. 3. The elongate inner core 34 preferably comprises a proximal
region 36 and a distal region 38. Proximal hub 37 is fitted on the
inner core 34 at one end of the proximal region 36. One or more
ultrasound radiating members are positioned within an inner core
energy delivery section 41 located within the distal region 38. The
ultrasound radiating members 40 form an ultrasound assembly 42,
which will be described in detail below.
[0063] As shown in the cross-section illustrated in FIG. 4, which
is taken along lines 4-4 in FIG. 3, the inner core 34 preferably
has a cylindrical shape, with an outer diameter that permits the
inner core 34 to be inserted into the central lumen 51 of the
tubular body 12 via the proximal access port 31. Suitable outer
diameters of the inner core 34 include, but are not limited to,
about 0.010 inches to about 0.100 inches. In another embodiment,
the outer diameter of the inner core 34 is between about 0.020
inches and about 0.080 inches. In yet another embodiment, the inner
core 34 has an outer diameter of about 0.035 inches.
[0064] Still referring to FIG. 4, the inner core 34 preferably
comprises a cylindrical outer body 35 that houses the ultrasound
assembly 42. The ultrasound assembly 42 comprises wiring and
ultrasound radiating members, described in greater detail in FIGS.
5 through 7D, such that the ultrasound assembly 42 is capable of
radiating ultrasonic energy from the energy delivery section 41 of
the inner core 34. The ultrasound assembly 42 is electrically
connected to the backend hub 33, where the inner core 34 can be
connected to a control system 100 via cable 45 (illustrated in FIG.
1). Preferably, an electrically insulating potting material 43
fills the inner core 34, surrounding the ultrasound assembly 42,
thus preventing movement of the ultrasound assembly 42 with respect
to the outer body 35. In one embodiment, the thickness of the outer
body 35 is between about 0.0002 inches and 0.010 inches. In another
embodiment, the thickness of the outer body 35 is between about
0.0002 inches and 0.005 inches. In yet another embodiment, the
thickness of the outer body 35 is about 0.0005 inches.
[0065] In a preferred embodiment, the ultrasound assembly 42
comprises a plurality of ultrasound radiating members 40 that are
divided into one or more groups. For example, FIGS. 5 and 6 are
schematic wiring diagrams illustrating one technique for connecting
five groups of ultrasound radiating members 40 to form the
ultrasound assembly 42. As illustrated in FIG. 5, the ultrasound
assembly 42 comprises five groups G1, G2, G3, G4, GS of ultrasound
radiating members 40 that are electrically connected to each other.
The five groups are also electrically connected to the control
system 100.
[0066] As used herein, the terms "ultrasonic energy", "ultrasound
and "ultrasonic" are broad terms, having their ordinary meanings,
and further refer to, without limitation, mechanical energy
transferred through longitudinal pressure or compression waves.
Ultrasonic energy can be emitted as continuous or pulsed waves,
depending on the requirements of a particular application.
Additionally, ultrasonic energy can be emitted in waveforms having
various shapes, such as sinusoidal waves, triangle waves, square
waves, or other wave forms. Ultrasonic energy includes sound waves.
In certain embodiments, the ultrasonic energy has a frequency
between about 20 kHz and about 20 MHz. For example, in one
embodiment, the waves have a frequency between about 500 kHz and
about 20 MHz. In another embodiment, the waves have a frequency
between about 1 MHz and about 3 MHz. In yet another embodiment, the
waves have a frequency of about 2 MHz. The average acoustic power
is between about 0.01 watts and 300 watts. In one embodiment, the
average acoustic power is about 15 watts.
[0067] As used herein, the term "ultrasound radiating member"
refers to any apparatus capable of producing ultrasonic energy. For
example, in one embodiment, an ultrasound radiating member
comprises an ultrasonic transducer, which converts electrical
energy into ultrasonic energy. A suitable example of an ultrasonic
transducer for generating ultrasonic energy from electrical energy
includes, but is not limited to, piezoelectric ceramic oscillators.
Piezoelectric ceramics typically comprise a crystalline material,
such as quartz, that change shape when an electrical current is
applied to the material. This change in shape, made oscillatory by
an oscillating driving signal, creates ultrasonic sound waves. In
other embodiments, ultrasonic energy can be generated by an
ultrasonic transducer that is remote from the ultrasound radiating
member, and the ultrasonic energy can be transmitted, via, for
example, a wire that is coupled to the ultrasound radiating
member.
[0068] Still referring to FIG. 5, the control circuitry 100
preferably comprises, among other things, a voltage source 102. The
voltage source 102 comprises a positive terminal 104 and a negative
terminal 106. The negative terminal 106 is connected to common wire
108, which connects the five groups G1-G5 of ultrasound radiating
members 40 in series. The positive terminal 104 is connected to a
plurality of lead wires 110, which each connect to one of the five
groups G1-G5 of ultrasound radiating members 40. Thus, under this
configuration, each of the five groups G1-G5, one of which is
illustrated in FIG. 6, is connected to the positive terminal 104
via one of the lead wires 110, and to the negative terminal 106 via
the common wire 108.
[0069] Referring now to FIG. 6, each group G1-G5 comprises a
plurality of ultrasound radiating members 40. Each of the
ultrasound radiating members 40 is electrically connected to the
common wire 108 and to the lead wire 310 via one of two positive
contact wires 112. Thus, when wired as illustrated, a constant
voltage difference will be applied to each ultrasound radiating
member 40 in the group. Although the group illustrated in FIG. 6
comprises twelve ultrasound radiating members 40, one of ordinary
skill in the art will recognize that more or fewer ultrasound
radiating members 40 can be included in the group. Likewise, more
or fewer than five groups can be included within the ultrasound
assembly 42 illustrated in FIG. 5.
[0070] FIG. 7A illustrates one preferred technique for arranging
the components of the ultrasound assembly 42 (as schematically
illustrated in FIG. 5) into the inner core 34 (as schematically
illustrated in FIG. 4). FIG. 7A is a cross-sectional view of the
ultrasound assembly 42 taken within group G1 in FIG. 5, as
indicated by the presence of four lead wires 110. For example, if a
cross-sectional view of the ultrasound assembly 42 was taken within
group G4 in FIG. 5, only one lead wire 310 would be present (that
is, the one lead wire connecting group GS).
[0071] Referring still to FIG. 7A, the common wire 108 comprises an
elongate, flat piece of electrically conductive material in
electrical contact with a pair of ultrasound radiating members 40.
Each of the ultrasound radiating members 40 is also in electrical
contact with a positive contact wire 312. Because the common wire
108 is connected to the negative terminal 106, and the positive
contact wire 312 is connected to the positive terminal 104, a
voltage difference can be created across each ultrasound radiating
member 40. Lead wires 110 are preferably separated from the other
components of the ultrasound assembly 42, thus preventing
interference with the operation of the ultrasound radiating members
40 as described above. For example, in one preferred embodiment,
the inner core 34 is filled with an insulating potting material 43,
thus deterring unwanted electrical contact between the various
components of the ultrasound assembly 42.
[0072] FIGS. 7B and 7C illustrate cross sectional views of the
inner core 34 of FIG. 7A taken along lines 7B-7B and 7C-7C,
respectively. As illustrated in FIG. 7B, the ultrasound radiating
members 40 are mounted in pairs along the common wire 108. The
ultrasound radiating members 40 are connected by positive contact
wires 112, such that substantially the same voltage is applied to
each ultrasound radiating member 40. As illustrated in FIG. 7C, the
common wire 108 preferably comprises wide regions 108W upon which
the ultrasound radiating members 40 can be mounted, thus reducing
the likelihood that the paired ultrasound radiating members 40 will
short together. In certain embodiments, outside the wide regions
108W, the common wire 108 may have a more conventional, rounded
wire shape.
[0073] In a modified embodiment, such as illustrated in FIG. 7D,
the common wire 108 is twisted to form a helical shape before being
fixed within the inner core 34. In such embodiments, the ultrasound
radiating members 40 are oriented in a plurality of radial
directions, thus enhancing the radial uniformity of the resulting
ultrasonic energy field.
[0074] One of ordinary skill in the art will recognize that the
wiring arrangement described above can be modified to allow each
group G1, G2, G3, G4, G5 to be independently powered. Specifically,
by providing a separate power source within the control system 100
for each group, each group can be individually turned on or off, or
can be driven with an individualized power. This provides the
advantage of allowing the delivery of ultrasonic energy to be
"turned off" in regions of the treatment site where treatment is
complete, thus preventing deleterious or unnecessary ultrasonic
energy to be applied to the patient.
[0075] The embodiments described above, and illustrated in FIGS. 5
through 7, illustrate a plurality of ultrasound radiating members
grouped spatially. That is, in such embodiments, all of the
ultrasound radiating members within a certain group are positioned
adjacent to each other, such that when a single group is activated,
ultrasonic energy is delivered at a specific length of the
ultrasound assembly. However, in modified embodiments, the
ultrasound radiating members of a certain group may be spaced apart
from each other, such that the ultrasound radiating members within
a certain group are not positioned adjacent to each other. In such
embodiments, when a single group is activated, ultrasonic energy
can be delivered from a larger, spaced apart portion of the energy
delivery section. Such modified embodiments may be advantageous in
applications wherein it is desired to deliver a less focused, more
diffuse ultrasonic energy field to the treatment site.
[0076] In a preferred embodiment, the ultrasound radiating members
40 comprise rectangular lead zirconate titanate ("PZT") ultrasound
transducers that have dimensions of about 0.017 inches by about
0.010 inches by about 0.080 inches. In other embodiments, other
configuration may be used. For example, disc-shaped ultrasound
radiating members 40 can be used in other embodiments. In a
preferred embodiment, the common wire 108 comprises copper, and is
about 0.005 inches thick, although other electrically conductive
materials and other dimensions can be used in other embodiments.
Lead wires 110 are preferably 36 gauge electrical conductors, while
positive contact wires 112 are preferably 42 gauge electrical
conductors. However, one of ordinary skill in the art will
recognize that other wire gauges can be used in other
embodiments.
[0077] As described above, suitable frequencies for the ultrasound
radiating member 40 include, but are not limited to, from about 20
kHz to about 20 MHz. In one embodiment, the frequency is between
about 500 kHz and 20 MHz, and in another embodiment 1 MHz and 3
MHz. In yet another embodiment, the ultrasound radiating members 40
are operated with a frequency of about 2 MHz.
[0078] FIG. 8 illustrates the inner core 34 positioned within the
tubular body 12. Details of the ultrasound assembly 42, provided in
FIG. 7A, are omitted for clarity. As described above, the inner
core 34 can be slid within the central lumen 51 of the tubular body
12, thereby allowing the inner core energy delivery section 41 to
be positioned within the tubular body energy delivery section 18.
For example, in a preferred embodiment, the materials comprising
the inner core energy delivery section 41, the tubular body energy
delivery section 18, and the potting material 43 all comprise
materials having a similar acoustic impedance, thereby minimizing
ultrasonic energy losses across material interfaces.
[0079] FIG. 8 further illustrates placement of fluid delivery ports
58 within the tubular body energy delivery section 18. As
illustrated, holes or slits are formed from the fluid delivery
lumen 30 through the tubular body 12, thereby permitting fluid flow
from the fluid delivery lumen 30 to the treatment site. Thus, a
source of therapeutic compound coupled to the inlet port 32
provides a hydraulic pressure which drives the therapeutic compound
through the fluid delivery lumens 30 and out the fluid delivery
ports 58.
[0080] By evenly spacing the fluid delivery lumens 30 around the
circumference of the tubular body 12, as illustrated in FIG. 8, a
substantially even flow of therapeutic compound around the
circumference of the tubular body 12 can be achieved. In addition,
the size, location and geometry of the fluid delivery ports 58 can
be selected to provide uniform fluid flow from the fluid delivery
ports 30 to the treatment site. For example, in one embodiment,
fluid delivery ports closer to the proximal region of the energy
delivery section 18 have smaller diameters then fluid delivery
closer to the distal region of the energy delivery section 18,
thereby allowing uniform delivery of fluid across the entire energy
delivery section.
[0081] For example, in one embodiment in which the fluid delivery
ports 58 have similar sizes along the length of the tubular body
12, the fluid delivery ports 58 have a diameter between about
0.0005 inches to about 0.0050 inches. In another embodiment in
which the size of the fluid delivery ports 58 changes along the
length of the tubular body 12, the fluid delivery ports 58 have a
diameter between about 0.001 inches to about 0.005 inches in the
proximal region of the energy delivery section 18, and between
about 0.005 inches to 0.0020 inches in the distal region of the
energy delivery section 18. The increase in size between adjacent
fluid delivery ports 58 depends on the material comprising the
tubular body 12, and on the size of the fluid delivery lumen 30.
The fluid delivery ports 58 can be created in the tubular body 12
by punching, drilling, burning or ablating (such as with a laser),
or by any other suitable method. Therapeutic compound flow along
the length of the tubular body 12 can also be increased by
increasing the density of the fluid delivery ports 58 toward the
distal region 15 of the tubular body 12.
[0082] It should be appreciated that it may be desirable to provide
non-uniform fluid flow from the fluid delivery ports 58 to the
treatment site. In such embodiment, the size, location and geometry
of the fluid delivery ports 58 can be selected to provide such
non-uniform fluid flow.
[0083] Referring still to FIG. 8, placement of the inner core 34
within the tubular body 12 further defines cooling fluid lumens 44.
Cooling fluid lumens 44 are formed between an outer surface 39 of
the inner core 34 and an inner surface 16 of the tubular body 12.
In certain embodiments, a cooling fluid can is introduced through
the proximal access port 31 such that cooling fluid flow is
produced through cooling fluid lumens 44 and out distal exit port
29 (see FIG. 1). The cooling fluid lumens 44 are preferably evenly
spaced around the circumference of the tubular body 12 (that is, at
approximately 120.degree. increments for a three-lumen
configuration), thereby providing uniform cooling fluid flow over
the inner core 34. Such a configuration is desirably to remove
unwanted thermal energy at the treatment site. As will be explained
below, the flow rate of the cooling fluid and the power to the
ultrasound assembly 42 can be adjusted to maintain the temp of the
inner core energy delivery section 41 within a desired range.
[0084] In a preferred embodiment, the inner core 34 can be rotated
or moved within the tubular body 12. Specifically, movement of the
inner core 34 can be accomplished by maneuvering the proximal hub
37 while holding the backend hub 33 stationary. The inner core
outer body 35 is at least partially constructed from a material
that provides enough structural support to permit movement of the
inner core 34 within the tubular body 12 without kinking of the
tubular body 12. Additionally, the inner core outer body 35
preferably comprises a material having the ability to transmit
torque. Suitable materials for the inner core outer body 35
include, but are not limited to, polyimides, polyesters,
polyurethanes, thermoplastic elastomers and braided polyimides.
[0085] In a preferred embodiment, the fluid delivery lumens 30 and
the cooling fluid lumens 44 are open at the distal end of the
tubular body 12, thereby allowing the therapeutic compound and the
cooling fluid to pass into the patient's vasculature at the distal
exit port. Or, if desired, the fluid delivery lumens 30 can be
selectively occluded at the distal end of the tubular body 12,
thereby providing additional hydraulic pressure to drive the
therapeutic compound out of the fluid delivery ports 58. In either
configuration, the inner core 34 can prevented from passing through
the distal exit port by making providing the inner core 34 with a
length that is less than the length of the tubular body. In other
embodiments, a protrusion is formed on the internal side of the
tubular body in the distal region 15, thereby preventing the inner
core 34 from passing through the distal exit port.
[0086] In still other embodiments, the catheter 10 further
comprises an occlusion device (not shown) positioned at the distal
exit port 29. The occlusion device preferably has a reduced inner
diameter that can accommodate a guidewire, but that is less than
the inner diameter of the central lumen 51. Thus, the inner core 34
is prevented from extending through the occlusion device and out
the distal exit port 29. For example, suitable inner diameters for
the occlusion device include, but are not limited to, about 0.005
inches to about 0.050 inches. In other embodiments, the occlusion
device has a closed end, thus preventing cooling fluid from leaving
the catheter 10, and instead recirculating to the proximal region
14 of the tubular body 12. These and other cooling fluid flow
configurations permit the power provided to the ultrasound assembly
42 to be increased in proportion to the cooling fluid flow rate.
Additionally, certain cooling fluid flow configurations can reduce
exposure of the patient's body to cooling fluids.
[0087] In certain embodiments, as illustrated in FIG. 8, the
tubular body 12 further comprises one or more temperature sensors
20, which are preferably located within the energy delivery section
18. In such embodiments, the proximal region 14 of the tubular body
12 includes a temperature sensor lead which can be incorporated
into cable 45 (illustrated in FIG. 1). Suitable temperature sensors
include, but are not limited to, temperature sensing diodes,
thermistors, thermocouples, resistance temperature detectors
("RTDs") and fiber optic temperature sensors which use
thermalchromic liquid crystals. Suitable temperature sensor 20
geometries include, but are not limited to, a point, a patch or a
stripe. The temperature sensors 20 can be positioned within one or
more of the fluid delivery lumens 30 (as illustrated), and/or
within one or more of the cooling fluid lumens 44.
[0088] FIG. 9 illustrates one embodiment for electrically
connecting the temperature sensors 20. In such embodiments, each
temperature sensor 20 is coupled to a common wire 61 and is
associated with an individual return wire 62. Accordingly, n+1
wires can be used to independently sense the temperature at n
distinct temperature sensors 20. The temperature at a particular
temperature sensor 20 can be determined by closing a switch 64 to
complete a circuit between that thermocouple's individual return
wire 62 and the common wire 61. In embodiments wherein the
temperature sensors 20 comprise thermocouples, the temperature can
be calculated from the voltage in the circuit using, for example, a
sensing circuit 63, which can be located within the external
control circuitry 100.
[0089] In other embodiments, each temperature sensor 20 is
independently wired. In such embodiments, 2n wires through the
tubular body 12 to independently sense the temperature at n
independent temperature sensors 20. In still other embodiments, the
flexibility of the tubular body 12 can be improved by using fiber
optic based temperature sensors 20. In such embodiments,
flexibility can be improved because only n fiber optic members are
used to sense the temperature at n independent temperature sensors
20.
[0090] FIG. 10 illustrates one embodiment of a feedback control
system 68 that can be used with the catheter 10. The feedback
control system 68 can be integrated into the control system that is
connected to the inner core 34 via cable 45 (as illustrated in FIG.
1). The feedback control system 68 allows the temperature at each
temperature sensor 20 to be monitored and allows the output power
of the energy source 70 to be adjusted accordingly. A physician
can, if desired, override the closed or open loop system.
[0091] The feedback control system 68 preferably comprises an
energy source 70, power circuits 72 and a power calculation device
74 that is coupled to the ultrasound radiating members 40. A
temperature measurement device 76 is coupled to the temperature
sensors 20 in the tubular body 12. A processing unit 78 is coupled
to the power calculation device 74, the power circuits 72 and a
user interface and display 80.
[0092] In operation, the temperature at each temperature sensor 20
is determined by the temperature measurement device 76. The
processing unit 78 receives each determined temperature from the
temperature measurement device 76. The determined temperature can
then be displayed to the user at the user interface and display
80.
[0093] The processing unit 78 comprises logic for generating a
temperature control signal. The temperature control signal is
proportional to the difference between the measured temperature and
a desired temperature. The desired temperature can be determined by
the user (at set at the user interface and display 80) or can be
preset within the processing unit 78.
[0094] The temperature control signal is received by the power
circuits 72. The power circuits 72 are preferably configured to
adjust the power level, voltage, phase and/or current of the
electrical energy supplied to the ultrasound radiating members 40
from the energy source 70. For example, when the temperature
control signal is above a particular level, the power supplied to a
particular group of ultrasound radiating members 40 is preferably
reduced in response to that temperature control signal. Similarly,
when the temperature control signal is below a particular level,
the power supplied to a particular group of ultrasound radiating
members 40 is preferably increased in response to that temperature
control signal. After each power adjustment, the processing unit 78
preferably monitors the temperature sensors 20 and produces another
temperature control signal which is received by the power circuits
72.
[0095] The processing unit 78 preferably further comprises safety
control logic. The safety control logic detects when the
temperature at a temperature sensor 20 has exceeded a safety
threshold. The processing unit 78 can then provide a temperature
control signal which causes the power circuits 72 to stop the
delivery of energy from the energy source 70 to that particular
group of ultrasound radiating members 40.
[0096] Because, in certain embodiments, the ultrasound radiating
members 40 are mobile relative to the temperature sensors 20, it
can be unclear which group of ultrasound radiating members 40
should have a power, voltage, phase and/or current level
adjustment. Consequently, each group of ultrasound radiating member
40 can be identically adjusted in certain embodiments. In a
modified embodiment, the power, voltage, phase, and/or current
supplied to each group of ultrasound radiating members 40 is
adjusted in response to the temperature sensor 20 which indicates
the highest temperature. Making voltage, phase and/or current
adjustments in response to the temperature sensed by the
temperature sensor 20 indicating the highest temperature can reduce
overheating of the treatment site.
[0097] The processing unit 78 also receives a power signal from a
power calculation device 74. The power signal can be used to
determine the power being received by each group of ultrasound
radiating members 40. The determined power can then be displayed to
the user on the user interface and display 80.
[0098] As described above, the feedback control system 68 can be
configured to maintain tissue adjacent to the energy delivery
section 18 below a desired temperature. For example, it is
generally desirable to prevent tissue at a treatment site from
increasing more than 6.degree. C. As described above, the
ultrasound radiating members 40 can be electrically connected such
that each group of ultrasound radiating members 40 generates an
independent output. In certain embodiments, the output from the
power circuit maintains a selected energy for each group of
ultrasound radiating members 40 for a selected length of time.
[0099] The processing unit 78 can comprise a digital or analog
controller, such as for example a computer with software. When the
processing unit 78 is a computer it can include a central
processing unit ("CPU") coupled through a system bus. As is well
known in the art, the user interface and display 80 can comprise a
mouse, a keyboard, a disk drive, a display monitor, a nonvolatile
memory system, or any another. Also preferably coupled to the bus
is a program memory and a data memory.
[0100] In lieu of the series of power adjustments described above,
a profile of the power to be delivered to each group of ultrasound
radiating members 40 can be incorporated into the processing unit
78, such that a preset amount of ultrasonic energy to be delivered
is pre-profiled. In such embodiments, the power delivered to each
group of ultrasound radiating members 40 can then be adjusted
according to the preset profiles.
[0101] The ultrasound radiating members are preferably operated in
a pulsed mode. For example, in one embodiment, the time average
power supplied to the ultrasound radiating members is preferably
between about 0.1 watts and 2 watts and more preferably between
about 0.5 watts and 1.5 watts. In certain preferred embodiments,
the time average power is approximately 0.6 watts or 1.2 watts. The
duty cycle is preferably between about 1% and 50% and more
preferably between about 5% and 25%. In certain preferred
embodiments, the duty ratio is approximately 7.5% or 15%. The pulse
averaged power is preferably between about 0.1 watts and 20 watts
and more preferably between approximately 5 watts and 20 watts. In
certain preferred embodiments, the pulse averaged power is
approximately 8 watts and 16 watts. The amplitude during each pulse
can be constant or varied.
[0102] In one embodiment, the pulse repetition rate is preferably
between about 5 Hz and 150 Hz and more preferably between about 10
Hz and 50 Hz. In certain preferred embodiments, the pulse
repetition rate is approximately 30 Hz. The pulse duration is
preferably between about 1 millisecond and 50 milliseconds and more
preferably between about 1 millisecond and 25 milliseconds. In
certain preferred embodiments, the pulse duration is approximately
2.5 milliseconds or 5 milliseconds.
[0103] In one particular embodiment, the transducers are operated
at an average power of approximately 0.6 watts, a duty cycle of
approximately 7.5%, a pulse repetition rate of 30 Hz, a pulse
average electrical power of approximately 8 watts and a pulse
duration of approximately 2.5 milliseconds.
[0104] The ultrasound radiating member used with the electrical
parameters described herein preferably has an acoustic efficiency
greater than 50% and more preferably greater than 75%. The
ultrasound radiating member can be formed a variety of shapes, such
as, cylindrical (solid or hollow), flat, bar, triangular, and the
like. The length of the ultrasound radiating member is preferably
between about 0.1 cm and about 0.5 cm. The thickness or diameter of
the ultrasound radiating members is preferably between about 0.02
cm and about 0.2 cm.
[0105] FIGS. 11A through 11D illustrate a method for using the
ultrasonic catheter 10. As illustrated in FIG. 11A, a guidewire 84
similar to a guidewire used in typical angioplasty procedures is
directed through a patient's vessels 86 to a treatment site 88
which includes a clot 90. The guidewire 84 is directed through the
clot 90. Suitable vessels 86 include, but are not limited to, the
large periphery blood vessels of the body. Additionally, as
mentioned above, the ultrasonic catheter 10 also has utility in
various imaging applications or in applications for treating and/or
diagnosing other diseases in other body parts.
[0106] As illustrated in FIG. 10B, the tubular body 12 is slid over
and is advanced along the guidewire 84 using conventional
over-the-guidewire techniques. The tubular body 12 is advanced
until the energy delivery section 18 of the tubular body 12 is
positioned at the clot 90. In certain embodiments, radiopaque
markers (not shown) are positioned along the energy delivery
section 18 of the tubular body 12 to aid in the positioning of the
tubular body 12 within the treatment site 88.
[0107] As illustrated in FIG. 10C, the guidewire 84 is then
withdrawn from the tubular body 12 by pulling the guidewire 84 from
the proximal region 14 of the catheter 10 while holding the tubular
body 12 stationary. This leaves the tubular body 12 positioned at
the treatment site 88.
[0108] As illustrated in FIG. 10D, the inner core 34 is then
inserted into the tubular body 12 until the ultrasound assembly 42
abuts against the occlusion device and is positioned at least
partially within the energy delivery section 18 of the tubular body
12. Once the inner core 34 is properly positioned, the ultrasound
assembly 42 is activated to deliver ultrasonic energy through the
energy delivery section 18 to the clot 90. As described above,
suitable ultrasonic energy is delivered with a frequency between
about 20 kHz and about 20 MHz.
[0109] In a certain embodiment, the ultrasound assembly 42
comprises sixty ultrasound radiating members 40 spaced over a
length of approximately 30 to 50 cm. In such embodiments, the
catheter 10 can be used to treat an elongate clot 90 without
requiring movement of or repositioning of the catheter 10 during
the treatment. However, it will be appreciated that in modified
embodiments the inner core 34 can be moved or rotated within the
tubular body 12 during the treatment. Such movement can be
accomplished by maneuvering the proximal hub 37 of the inner core
34 while holding the backend hub 33 stationary.
[0110] Referring again to FIG. 11D, arrows 48 indicate that a
cooling fluid flows through the cooling fluid lumen 44 and out the
distal exit port 29. Likewise, arrows 49 indicated that a
therapeutic compound flows through the fluid delivery lumen 30 and
out the fluid delivery ports 58 to the treatment site 88.
[0111] The cooling fluid can be delivered before, after, during or
intermittently with the delivery of ultrasonic energy. Similarly,
the therapeutic compound can be delivered before, after, during or
intermittently with the delivery of ultrasonic energy.
Consequently, the steps illustrated in FIGS. 11A through 11D can be
performed in a variety of different orders than that described
above. The therapeutic compound and ultrasonic energy are
preferably applied until the clot 90 is partially or entirely
dissolved. Once the clot 90 has been dissolved to the desired
degree, the tubular body 12 and the inner core 34 are withdrawn
from the treatment site 88.
[0112] To reduce electric current leakage through the patient's
body to ground, in certain embodiments the control system 100 may
comprise an isolation pod 200. FIG. 12 illustrates one embodiment
of an isolation pod 200 that is contains certain portions of the
control system 100, as described in more detail below. Preferably,
the external control circuitry 100, including the isolation pod 200
(if any), is positioned proximal to the backend hub 33 (see FIG.
1), thereby preventing crosstalk between the wiring to the
plurality of groups of ultrasound radiating members.
[0113] The isolation pod 200 comprises an isolation barrier 228
configured to reduce or eliminate unwanted electrical current flow
through the patient's body. For example, in the illustrated
embodiment, two transformers 256, 276 form an isolation barrier
between the external control circuitry 100 and the certain
components of the isolation pod 200.
[0114] Referring still to FIG. 12, a transformer loop 278 is used
to measure the leakage current of the catheter 10. This leakage
current represents the current that does not return to the
isolation pod 200 through the return lines, but instead passes
through the patient's body to ground. A center tap from the
transformer loop 278 connects to two diodes that rectify the
leakage current. In this example, zener diodes with a low threshold
voltage are used to rectify the small signal provided from the
transformer loop.
[0115] The external control circuitry 100 provides a radio
frequency signal 224 for driving the ultrasound assembly 42. The
radio frequency signal 224 operates in the ultrasonic frequency
range, and is tuned to a frequency that activates the ultrasound
radiating members 40 in the inner core 34. The radio frequency
signal 224 is electromagnetically coupled to the isolation pod 200
using a transformer 256. The dielectric layers of the transformer
256 form an isolation barrier. This isolation barrier substantially
prevents electrical current from flowing from the isolation pod
200, through the patient's body, and back into the isolation pod
200. By electromagnetically coupling the driving radio frequency
signal to the isolation pod 200, the current loop is broken and
electric current is thereby prevented from flowing through the
patient's body.
[0116] In the embodiment illustrated in FIG. 12, the isolation pod
200 is compatible with multiple types of catheters. The different
catheters can use different types or quantities of ultrasound
radiating members, which in tum may cause variations in the input
impedance seen by the radio frequency amplifier. Even if the
ultrasound radiating members are configured to be identical,
fabrication defects will often cause the impedance of ultrasound
radiating members to vary. Additionally, the activation pattern or
configuration of ultrasound radiating members within a catheter can
also alter the input impedance.
[0117] The exemplary isolation pod 200 includes circuitry to enable
matching the output impedance of the radio frequency amplifier to
the input impedance of the ultrasound radiating members. For
example, many radio frequency amplifiers have an output impedance
of about 50 n. To maximize power efficiency, the isolation pod 200
attempts to match the impedance by providing a substantially
equivalent 50 Q at the input.
[0118] Still referring to FIG. 12, the isolation pod 200 provides
circuitry for tuning the input impedance of the isolation pod 200
to match the output impedance of the radio frequency amplifier. For
example, FIG. 12 illustrates the coupling transformer 256 with taps
258 on the secondary side. Selecting different taps modifies the
turns ratio of the transformer and thereby changes the input
impedance of the isolation pod 200.
[0119] Changing the turns ratio of the coupling transformer 256
also affects the amplitude of the current passing through the
ultrasonic assembly 42. As needed, the external control circuitry
100 compensates for these changes in amplitude for example by
driving the radio frequency signal at different levels.
[0120] The embodiment illustrated in FIG. 12 also shows the use of
inductors 260 for tuning the input impedance. As illustrated, the
isolation pod 200 further comprises three individually controlled
switches 262 that connect the three inductors with the radio
frequency input circuit. In this example, a total of eight tuning
settings are achievable by opening and closing the inductor
switches in various combinations. The tuning circuitry is not
limited to the use of inductors or transformer taps. Other
components, such as capacitors and resistors, may also be used to
tune the input impedance.
[0121] In one embodiment, tuning information is determined for a
catheter at the time of manufacture. The tuning information is then
embedded into the catheter, such as by saving the tuning
information in an identification programmable read-only memory
("PROM") 254. Alternatively, the serial number or other identifying
indicia of the catheter together with the tuning information is
entered into a database. The isolation pod 200 then retrieves the
tuning information from the database and appropriately adjusts the
tuning circuitry to the catheter that is attached to the isolation
pod 200.
[0122] In another embodiment, the isolation pod 200 includes
internal circuitry to detect the impedance of the ultrasound
assembly 42 in the catheter and adjusts the tuning circuitry
appropriately.
[0123] FIG. 12 further illustrates a configuration that is
particularly adapted for the use of multiple ultrasound radiating
members such as in the arrangements described above. In the
illustrated embodiment, ten ultrasound radiating members are
connected to the isolation pod 200 using five connections. The
ultrasound radiating members are controlled by multiplexing the
driving signal through five pairs of switches 268. The ultrasound
radiating member driving lines in the inner core 34 connect to the
pairs of switches 268 within the isolation pod 200. Each pair of
switches 268 has four settings: (open, open), (open, closed),
(closed, open) and (closed, closed). In operation, only three
settings are used because the (closed, closed) setting
short-circuits the driving signal. In the illustrated example,
wherein there are five ultrasound radiating member driving lines,
3.sup.5=243 modes of operation are available. Examples of these
modes are described in the embodiments that follow.
[0124] FIG. 13 illustrates an arrangement where the ultrasound
radiating members are linearly spaced within the catheter. In the
illustrated example, the catheter has five ultrasound radiating
member driving lines 302, 304, 306, 308, and 310.
[0125] In one embodiment, one pair of switches is in the (closed,
open) setting and the remaining four pairs of switches are in the
(open, closed) setting. In this such embodiments, four ultrasound
radiating members are active at a time. The remaining six
ultrasound radiating members have both terminals short circuited,
so they are not active.
[0126] FIG. 14 illustrates an embodiment wherein the pair of
switches for the first ultrasound radiating member driving line 302
is in the (closed, open) setting and the pairs of switches for the
remaining ultrasound radiating member driving lines 304, 306, 308,
310 are in the (open, closed) setting. In this configuration, four
ultrasound radiating members 312, 314, 316, 318 are active, and six
remaining ultrasound radiating members 320, 322, 324, 326, 328, 330
are inactive. The active ultrasound radiating members 312, 314,
316, 318 have substantially the same voltage differential appearing
across the ultrasound radiating members terminals.
[0127] FIG. 15 illustrates an embodiment wherein one pair of
switches is in the (closed, open) setting and another pair of
switches is in the (open, closed) setting. As illustrated, the pair
of switches for the first ultrasound radiating member driving line
302 is in the (closed, open) setting, the pair of switches for the
second ultrasound radiating member driving line 304 is in the
(open, closed) setting, and the pairs of switches for the remaining
ultrasound radiating member driving lines 306, 308, 310 are in the
(open, open) setting. The resulting network of connections between
the ultrasound radiating member form several voltage dividers. This
results in different voltage differences across the terminals of
the various ultrasound radiating members. Assuming the ultrasound
radiating members are equivalent, the first ultrasound radiating
member 312 will have the full driving signal appearing across its
terminals, six ultrasound radiating members 314, 316, 318, 320,
322, 324 will have a half-strength driving signal appearing across
their terminals, and the remaining three ultrasound radiating
members 326, 328, 330 will have no voltage differential appearing
across their terminals.
[0128] FIG. 16 illustrates an embodiment wherein the pairs of
switches for the first and third ultrasound radiating member
driving lines 302, 306 are in the (closed, open) setting and the
pairs of switches for the remaining ultrasound radiating member
driving lines 304, 308, 310 are in the (open, closed) setting. In
this configuration, six ultrasound radiating members 312, 316, 318,
320, 326, 328 are active, and the remaining four ultrasound
radiating members 314, 322, 324, 330 are inactive.
[0129] FIG. 17 shows a modified catheter configuration with seven
connections to the isolation pod 200. In such a configuration, the
isolation pod 200 uses four switches to connect the first terminal
278 of the driving signal to the first four ultrasound radiating
member driving lines 352, 354, 356, 358, and three switches to
connect the second terminal 280 of the driving signal to the
remaining three ultrasound radiating member driving lines 360, 362,
364. When all of the switches connected to the first terminal 278
are in the (closed) setting, each switch connected to the second
terminal 280 activates a bank of four ultrasound radiating members.
For example, if all the switches to the first terminal 278 are
closed, closing the switch for the ultrasound radiating member
driving line 360 activates four ultrasound radiating members 372,
378, 384, 390. Closing the switch for the ultrasound radiating
member driving line 362 activates four ultrasound radiating members
374, 380, 386, 392, and closing the switch for the ultrasound
radiating member driving line 364 activates four ultrasound
radiating members 376, 382, 388, 394. The banks are independently
operable, so zero, one or two banks can be active at any given
time.
[0130] Alternatively, when all of the switches connected to the
second terminal 280 are in the (closed) setting, each switch
connected to the first terminal 278 activates a bank of three
ultrasound radiating members. For example, if all the switches to
the second terminal 280 are closed, closing the switch for the
ultrasound radiating member driving line 352 activates three
ultrasound radiating members 372, 374, 376, 378. Other banks of
three ultrasound radiating members are activated by the closing
switches for the remaining three ultrasound radiating member
driving lines 354, 356, 358. Again, the banks are independently
operable, so zero, one, two, or three banks can be active at any
given time.
[0131] It is not necessary to activate the ultrasound radiating
members in banks, because the switches can be individually
controlled. A total of 2.sup.7=128 driving combinations are
possible. The non-bank configurations include voltage divider
circuits, so all of the ultrasound radiating members are not driven
at full strength in these configurations.
[0132] FIG. 18 illustrates another catheter embodiment where the
ultrasound radiating members are arranged in three banks with four
ultrasound radiating members in each bank. Closing the switch for
ultrasound radiating member driving line 430 activates four
ultrasound radiating members 402, 408, 414, 420. Closing the switch
for ultrasound radiating member driving line 432 activates four
ultrasound radiating members 404, 410, 416, 422. Closing the switch
for ultrasound radiating member driving line 434 activates four
ultrasound radiating members 406, 412, 418, 424.
[0133] One of ordinary skill in the art will understand that the
illustrated embodiments are exemplary and that the catheter design
is not limited to the illustrated configurations. For example, the
catheter may include different numbers of ultrasound radiating
members, ultrasound radiating member driving lines, or switches.
Some or all of the switches may alternately be included as part of
the catheter.
[0134] A catheter may include ultrasound radiating members tuned to
resonate at multiple frequencies. Ultrasound radiating members
having the same resonant frequency can be selected individually or
in groups. Alternatively, ultrasound radiating members having
different resonant frequencies can be driven by the same driving
signal. In such embodiments, the amount of ultrasonic energy
delivered by an ultrasound radiating member depends in part on the
frequency at which the ultrasound radiating member is driven.
[0135] Controlling the amplitude and frequency of the driving
signal and arranging the placement of the ultrasound radiating
members allows the catheter to deliver appropriate ultrasonic
energy levels to the treatment site. In certain applications, it is
desired that the catheter delivers a uniform dose of ultrasonic
energy to the treatment site. In other applications, it is desired
to deliver greater amounts of ultrasonic energy or ultrasonic
energy of a different frequency to different portions of the
treatment site. The individual control of the ultrasound radiating
members described above allows the ultrasound assembly to deliver
the appropriate amount and quality of ultrasonic energy to the
treatment site.
[0136] For example, piezoelectric transducers can be used to
generate ultrasonic energy. Piezoelectric transducers produce
ultrasonic energy when an electric voltage is applied to certain
crystalline structures. The characteristics of the ultrasonic
energy generated by a piezoelectric transducer is determined by the
crystalline structure of the transducer, as well as by the
frequency and voltage at which the transducer is driven.
[0137] As shown in FIG. 12, the isolation pod 200 includes
circuitry for controlling the generation of ultrasonic energy. In
one embodiment, an alternating current ("AC") signal is provided to
the isolation pod 200 from an external source. In another
embodiment, the AC signal is generated within the isolation pod 200
using circuitry such as a crystal oscillator. In one embodiment,
the AC signal drives the ultrasound radiating members directly. In
a modified embodiment, the isolation pod 200 includes additional
circuitry to modify the AC signal before driving the ultrasound
radiating members.
[0138] As discussed above, and as shown in FIG. 12, in certain
embodiments the catheter further comprises temperature sensors. As
illustrated, the current source applies a constant current bias
across a silicon P--N diode junction. At a constant current bias,
the voltage drop across a silicon P--N diode junction shows roughly
a -2 mV .degree. C.sup.-1 temperature coefficient. The arrangement
of temperature sensor diodes in the catheter together with the
diode path selection switches and the reversible current source
allows the isolation pod 200 to select a single diode from the set
of twelve diodes for measuring the temperature. The remaining
diodes are either switched out of the circuit or reverse biased. A
pre-amplifier circuit amplifies the voltage drop across the diode
and provides a signal to an analog to digital (AID) converter.
[0139] FIG. 19 illustrates a diode arrangement within a catheter.
In this embodiment, configuring a first set of switches in the
(open, closed) setting, a second set of switches in the (closed,
open) setting, and the remaining to sets of switches in the (open,
open) setting results in one diode being forward biased and a
second diode being reverse biased. The remaining diodes are left
floating at one or both terminals.
[0140] The direction of the current is controlled by a single-pull
double-throw (SPDT) switch as illustrated in FIG. 12. The direction
of the current determines which of the two non-floating diodes is
forward biased.
[0141] Because there may be some variance in the diodes when used
as temperatures sensors, one embodiment utilizes a calibration
process. For example, calibration data may be included in the ID
PROM 254. In modified embodiments, the diodes can be calibrated
against an ambient temperature reading.
[0142] In other embodiments, the temperature sensors 20 monitor the
temperature of the treatment site at which the catheter is
operating. For example, in one embodiment a temperature sensor is
placed near an ultrasound radiating member to measure the
temperature of the tissue near the catheter. In other embodiments,
a temperature sensor is positioned between two ultrasound radiating
members to measure the average energy delivered by the ultrasound
assembly.
[0143] Referring again to the isolation pod 200 illustrated in FIG.
12, power is provided through the power isolation transformer 276.
Communications data can be modulated with the power signal. For
example, the embodiment illustrated in FIG. 12 further comprises a
modulator/demodulator ("modem") configured to transmit and receive
signals modulated on the power signal. This allows a
microcontroller 272 to communicate with the external control
circuitry 100. In such embodiments, the external control circuitry
100 can effectively control the activation of ultrasound radiating
members and diodes by sending commands to the microcontroller. Or,
in modified embodiments, the microcontroller can execute control
sequences from memory. The microcontroller preferably includes
outputs to control the switches and other drivers within the
isolation pod 200.
[0144] Still referring to FIG. 12, a PROM 254 contains information
relating to a number of factors, including but not limited to the
catheter length, the number of ultrasound radiating members, the
center frequency at which each ultrasound radiating member should
be run, the tuning parameters for the ultrasound radiating members,
and the calibration factors for the temperature sensors. A catheter
connector 230, illustrated in FIG. 20, and which will be described
in detail below, provides connection between the wires in the
isolation pod 200 and the wires in the cable 45. These wires carry
electrical signals between the isolation pod 200 and the inner core
34 located within the catheter 10.
[0145] As illustrated in FIG. 20, the connection between the
isolation pod 200 and the catheter 10 generally comprises a
catheter connector 230. The catheter connector 230 is preferably
integral with the isolation pod 200, and generally comprises a
customized slot 240 into which the cable 45 fits. One advantage of
having the catheter connector 230 integral with the isolation pod
200 is the reduction in physical space and costs that are
associated with using an additional cable and connection device
outside the isolation pod 200. In the illustrated embodiment, a
toe-catch arrangement assures a proper fit and assists in keeping
the connecting end of the cable 45 within the customized slot. The
catheter connector 230 preferably includes a latch 244 to secure
the connecting end of the cable 45 within the customized slot
240.
[0146] Still referring to FIG. 20, the catheter connector 230
preferably comprises an array of gold spring contacts 246 which
provide an electrical connection between the isolation pod 200 and
the cable 45. The wire contacts at the connecting end of the cable
are configured to be aligned with the gold spring contacts 246 of
the connector 230. The catheter connector 230, the cable 45, and
their respective components can be manufactured in accordance with
any of the variety of techniques well known in the electrical
interfacing and wiring fields.
[0147] In the embodiment illustrated in FIG. 12, a catheter houses
the ultrasound radiating members and the temperature sensors. In
such embodiments, the catheter is connected to the isolation pod
200 which houses the electronics capable of driving the ultrasound
radiating members, as well as additional electronics capable of
processing temperature signals received from the catheter. In one
embodiment, the isolation pod 200 receives control signals from
external circuitry 300, and transmits data back to the external
circuitry using a data interface 252.
[0148] In another embodiment, all or part of the electronics for
driving the ultrasound radiating members is housed within the
backend hub 33. Similarly, all or part of the electronics for
processing the temperature signals is can be housed within the
backend hub 33 as well. However, because certain catheters
described herein are intended to be disposable, the cost of the
catheter can be reduced by minimizing the amount of electronics
contained within the catheter. Additionally, reducing the amount of
electronics contained within the catheter also reduces the catheter
size. Thus, catheters configured to operate in narrow passages such
as small vessels will also benefit from the reduction of
electronics contained within the catheter. Therefore, in other
embodiments, minimal electronics is incorporated within the
catheter.
[0149] A user may connect multiple types of catheter to a single
isolation pod 200. To identify the type of catheter connected to
the isolation pod 200, the catheter preferably includes electronics
containing an identifying code. The identifying code conveys
information such as the type of catheter, the serial number of the
catheter, the manufacturing location of the catheter, the date of
manufacture, or other identifying information. In one embodiment,
the circuitry for storing the identifying code is a PROM 254. Other
types of memory such as flash memory or non-volatile random access
memory ("RAM") can also serve to identify the catheter. Electronics
such as switches, jumpers, diodes, or hard wired connections can
also serve to identify the catheter. One of ordinary skill in the
art will recognize that other circuits not disclosed herein will
also provide identification of the catheter.
[0150] Information contained on the identification PROM 254 can
include, for example, the length of the catheter, the length of the
treatment zone, the number of ultrasound radiating members in the
catheter, the ultrasound radiating member layout, the resonant
frequency of the ultrasound radiating members, tuning information
for the ultrasound radiating members, compensation and/or
calibration data for the diodes, or patterns for driving the
ultrasound radiating members.
[0151] As illustrated in FIG. 12, in one embodiment, temperature
sensitive diodes 238 are used as sensors to measure a temperature
near the catheter. In such embodiments, a pair of temperature
sensitive diodes 238 is selectively enabled, and an output signal
is provided to an analog to digital ("AID") converter. Or, in
modified embodiments, multiple pairs of diodes are activated with
the output signals being provided to the AID converter
simultaneously. Other embodiments include a sensor to measure the
ambient temperature, which is used, for example, to calibrate the
temperature sensors. Additionally, the ambient temperature provides
information as to whether the catheter and isolation pod are
functioning properly.
[0152] Still referring to FIG. 12, the output of the AID converter
270 is provided to a microcontroller 272 for analysis. The
microcontroller 272 monitors the heat produced by the various
ultrasound radiating members and/or the temperature of the tissue
near the catheter, and uses such information to provide control
signals to adjust characteristics such as signal strength or
frequency of the driving signal provided to the individual
ultrasound radiating members.
[0153] One of ordinary skill m the art will recognize that the
various embodiments of the isolation pod described above, and
illustrated in FIGS. 14 through 20, can be used with the catheter
and various ultrasound radiating member and temperature sensor
configurations illustrated in FIGS. 2 through 8. In addition, the
various embodiments of the isolation pod described above, and
illustrated in FIGS. 14 through 20, can also be used with other
ultrasound radiating member and temperature sensor configurations
not specifically described herein. For example, the isolation pod
may also be used with an ultrasonic catheter that has only one
ultrasound radiating member and/or is configured to fit within the
small vessels of the body such as the small vessel catheters
described in co-pending U.S. patent application, entitled "Small
Vessel Ultrasound Catheter", filed on the same date as the present
application.
[0154] While the foregoing detailed description has described
several embodiments of the apparatus and methods of the present
invention, it is to be understood that the above description is
illustrative only and not limited of the disclosed invention. It
will be appreciated that the specific dimensions of the various
catheters and inner cores can differ from those described above,
and that the methods described can be used within any biological
conduit in a patient's body, while remaining within the scope of
the present invention. Thus, the present invention is to be limited
only by the claims that follow.
* * * * *