U.S. patent application number 10/771690 was filed with the patent office on 2004-08-12 for apparatus and method for an ultrasonic probe device with rapid attachment and detachment means.
This patent application is currently assigned to OmniSonics Medical Technologies, Inc.. Invention is credited to Hare, Bradley A., Marciante, Rebecca I., Rabiner, Robert A., Ranucci, Kevin, Robertson, Roy, Varady, Mark J..
Application Number | 20040158151 10/771690 |
Document ID | / |
Family ID | 25523318 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040158151 |
Kind Code |
A1 |
Ranucci, Kevin ; et
al. |
August 12, 2004 |
Apparatus and method for an ultrasonic probe device with rapid
attachment and detachment means
Abstract
An ultrasonic tissue ablation device comprising a transversely
vibrating elongated probe, and a coupling assembly for probe
attachment and detachment that enables the probe assembly and
separation from the device body that includes the ultrasound energy
source and a sound conductor, and a method of use for removal of
vascular occlusions in blood vessels. The coupling assembly enables
incorporation of elongated probes with small cross sectional lumens
such as a catheter guidewires. The probe detachability allows
insertion manipulation and withdrawal independently of the device
body. The probe can be used with acoustic and/or aspirations
sheaths to enhance destruction and removal of an occlusion. The
horn assembly of the device that contains a sound conducting horn
functions as an energy regulator and reservoir for the probe, and
precludes loss of probe cavitation energy by its bending or damping
within the blood vessel.
Inventors: |
Ranucci, Kevin; (North
Attleboro, MA) ; Rabiner, Robert A.; (North Reading,
MA) ; Hare, Bradley A.; (Chelmsford, MA) ;
Varady, Mark J.; (Andover, MA) ; Marciante, Rebecca
I.; (North Reading, MA) ; Robertson, Roy;
(Ipswich, MA) |
Correspondence
Address: |
PALMER & DODGE, LLP
RICHARD B. SMITH
111 HUNTINGTON AVENUE
BOSTON
MA
02199
US
|
Assignee: |
OmniSonics Medical Technologies,
Inc.
|
Family ID: |
25523318 |
Appl. No.: |
10/771690 |
Filed: |
February 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10771690 |
Feb 4, 2004 |
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09975725 |
Oct 11, 2001 |
|
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|
6695782 |
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09975725 |
Oct 11, 2001 |
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09625803 |
Jul 26, 2000 |
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60157824 |
Oct 5, 1999 |
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Current U.S.
Class: |
600/439 ; 601/4;
604/22 |
Current CPC
Class: |
A61B 2017/32007
20170801; A61B 2017/00137 20130101; A61B 2017/320069 20170801; A61B
17/320068 20130101; A61B 2017/22018 20130101; A61B 17/22012
20130101; A61B 2017/00274 20130101; A61N 2007/0008 20130101; A61B
2017/22008 20130101; A61B 2017/22007 20130101; A61B 2017/00477
20130101; A61B 2018/00547 20130101; A61N 7/022 20130101; A61B
2017/320089 20170801; A61B 2017/320084 20130101 |
Class at
Publication: |
600/439 ;
601/004; 604/022 |
International
Class: |
A61N 007/00 |
Claims
What is claimed is:
1. An ultrasonic medical device comprising: an ultrasonic probe
having a proximal end, a distal end and a longitudinal axis between
the proximal end and the distal end; and a horn assembly having a
distal end engaged to the proximal end of the ultrasonic probe
through a coupling assembly, wherein the coupling assembly
transmits an ultrasound energy from the horn assembly to the
ultrasonic probe.
2. The ultrasonic medical device of claim 1 wherein the horn
assembly amplifies the ultrasound energy.
3. The ultrasonic medical device of claim 1 wherein the coupling
assembly reflects a substantial portion of the ultrasound energy
back into the horn assembly.
4. The ultrasonic medical device of claim 1 wherein the ultrasound
energy is transmitted along the longitudinal axis of the ultrasonic
probe, causing the ultrasonic probe to vibrate in a direction
transverse to the longitudinal axis of the ultrasonic probe,
producing a plurality of nodes and anti-nodes along a portion of
the longitudinal axis of the ultrasonic probe.
5. The ultrasonic medical device of claim 1 further comprising an
ultrasound energy source engaged to the horn assembly.
6. The ultrasonic medical device of claim 1 wherein the coupling
assembly presents an impedance mismatch between the horn assembly
and the ultrasonic probe.
7. The ultrasonic medical device of claim 1 wherein the coupling
assembly allows rapid attachment and detachment of the ultrasonic
probe and an ultrasound energy source engaged to the horn
assembly.
8. The ultrasonic medical device of claim 1 wherein the horn
assembly stores ultrasound energy.
9. The ultrasonic medical device of claim 1 wherein the coupling
assembly comprises a quick attachment-detachment collet.
10. The ultrasonic medical device of claim 8 wherein the quick
attachment-detachment collet is housed within an externally mounted
compressive clamp capable of exerting a compressive force on the
quick attachment-detachment collet after insertion of the
ultrasonic probe into the quick attachment-detachment collet.
11. The ultrasonic medical device of claim 8 wherein the quick
attachment-detachment collet applies a restraining inwardly
compressive force on the ultrasonic probe.
12. The ultrasonic medical device of claim 1 wherein a head segment
at the proximal end of the ultrasonic probe is inserted into a
cylindrical slot of the horn assembly.
13. The ultrasonic medical device of claim 1 wherein a locking nut
engages the horn assembly to the ultrasonic probe by engaging screw
threads of the locking nut and complimentary threads on the horn
assembly.
14. The ultrasonic medical device of claim 1 wherein a flexibility
of the ultrasonic probe allows movement of the ultrasonic probe
through a narrow, tortuous vessel.
15. The ultrasonic medical device of claim 1 further comprising a
sheath surrounding at least a portion of the ultrasonic probe.
16. The ultrasonic medical device of claim 1 wherein the ultrasonic
probe is an elongated wire.
17. An ultrasonic medical device for removing endovascular material
comprising: an elongated probe having a proximal end, a distal end
and a longitudinal axis between the proximal end and the distal
end; a horn assembly engaging the proximal end of the elongated
probe; a coupling assembly engaging the proximal end of the
elongated probe to a distal end of the horn assembly, wherein the
horn assembly amplifies an ultrasound energy and transmits the
ultrasound energy to the elongated probe, producing a transverse
ultrasonic vibration along at least a portion of the longitudinal
axis of the elongated probe and generating a plurality of
transverse vibration anti-nodes along at least a portion of the
longitudinal axis of the elongated probe.
18. The ultrasonic medical device of claim 17 further comprising an
ultrasound energy source engaging the horn assembly.
19. The ultrasonic medical device of claim 17 wherein the coupling
assembly presents an impedance mismatch between the horn assembly
and the elongated probe.
20. The ultrasonic medical device of claim 17 wherein the coupling
assembly reflects a substantial portion of the ultrasound energy
back into the horn assembly.
21. The ultrasonic medical device of claim 17 wherein the horn
assembly stores the ultrasound energy.
22. The ultrasonic medical device of claim 17 wherein a head
segment at the proximal end of the elongated probe is inserted into
a cylindrical slot of the horn assembly.
23. The ultrasonic medical device of claim 17 wherein a locking nut
engages the horn assembly to the elongated probe by engaging screw
threads of the locking nut and complimentary threads on the horn
assembly.
24. The ultrasonic medical device of claim 17 wherein the coupling
assembly comprises a quick attachment-detachment collet.
25. The ultrasonic medical device of claim 24 wherein the quick
attachment-detachment collet is housed within an externally mounted
compressive clamp capable of exerting a compressive force on the
quick attachment-detachment collet after insertion of the elongated
probe into the quick attachment-detachment collet.
26. A method of ablation of an endovascular material in a vessel
comprising: inserting an ultrasonic probe into the vessel; moving
the ultrasonic probe within the vessel to a site of the
endovascular material; engaging a horn assembly to the ultrasonic
probe with a coupling assembly; activating an ultrasound energy
source engaged to the horn assembly to transmit ultrasound energy
to the horn assembly; amplifying the ultrasound energy with the
horn assembly; and transmitting the ultrasound energy to the
ultrasonic probe to produce a transverse ultrasonic vibration along
at least a portion of a longitudinal axis of the ultrasonic probe,
producing a plurality of transverse anti-nodes along at least a
portion of the longitudinal axis of the ultrasonic probe.
27. The method of claim 26 further comprising disengaging the horn
assembly from the ultrasonic probe after the ablation of the
endovascular material.
28. The method of claim 26 further comprising surrounding at least
a portion of the longitudinal axis of the ultrasonic probe with a
sheath.
29. The method of claim 26 further comprising inserting a head
segment at a proximal end of the ultrasonic probe into a
cylindrical slot of the horn assembly and engaging the horn
assembly to the ultrasonic probe by engaging screw threads of a
locking nut surrounding the head segment onto complimentary threads
on the horn assembly.
30. The method of claim 26 further comprising inserting the
ultrasonic probe into the vessel with a flexibility that does not
damage the vessel.
31. The method of claim 26 further comprising providing the
coupling assembly has a quick attachment-detachment collet.
32. The method of claim 31 further comprising housing the quick
attachment-detachment collet within an externally mounted
compressive clamp capable of exerting a compressive force on the
quick attachment-detachment collet after insertion of the
ultrasonic probe into the quick attachment-detachment collet.
33. The method of claim 28 further comprising providing the
ultrasonic probe is a wire.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 09/975,725 filed on Oct. 11, 2001, which is a continuation in
part of U.S. application Ser. No. 09/625,803 filed on Jul. 26, 2000
which claims priority to U.S. Provisional Application No.
60/157,824 filed on Oct. 5, 1999, and claims the benefit of U.S.
Provisional Application No. 60/225,060 filed on Aug. 14, 2000, the
entirety of all these applications are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to medical devices,
and more particularly to an apparatus and method for using an
ultrasonic medical device operating in a transverse mode for
emulsification of endovascular materials by causing tissue
fragmentation of occlusion materials. The invention also relates to
an apparatus emitting ultrasonic energy in transverse mode used in
combination with an elongated flexible catheter wire, wherein the
probe is rapidly attachable to and detachable from the ultrasonic
energy source component of the device.
BACKGROUND OF THE INVENTION
[0003] Vascular occlusions (clots or thrombi and occlusional
deposits, such as calcium, fatty deposits, or plaque) result in the
restriction or blockage of blood flow in the vessels in which they
occur. Occlusions result in oxygen deprivation ("ischemia") of
tissues supplied by these blood vessels. Prolonged ischemia results
in permanent damage of tissue that can lead to myocardial
infarction, stroke, or death. Targets for occlusion include
coronary arteries, peripheral arteries and other blood vessels. The
disruption of an occlusion or thrombolysis can be effected by
pharmacological agents and/or mechanical means.
[0004] Ultrasonic probes are devices which use ultrasonic energy to
fragment body tissue (see, e.g., U.S. Pat. No. 5,112,300; U.S. Pat.
No. 5,180,363; U.S. Pat. No. 4,989,583; U.S. Pat. No. 4,931,047;
U.S. Pat. No. 4,922,902; and U.S. Pat. No. 3,805,787) and have been
used in many surgical procedures. The use of ultrasonic energy has
been proposed both to mechanically disrupt clots, and to enhance
the intravascular delivery of drugs to clot formations (see, e.g.,
U.S. Pat. No. 5,725,494; U.S. Pat. No. 5,728,062; and U.S. Pat. No.
5,735,811). Ultrasonic devices used for vascular treatments
typically comprise an extra-corporeal transducer coupled to a solid
metal wire that is attached to a plurality of wires at the distal
end, that is then threaded through the blood vessel and placed in
contact with the occlusion (see, e.g., U.S. Pat. No. 5,269,297). In
some cases, the transducer is delivered to the site of the clot,
the transducer comprising a bendable plate (see, U.S. Pat. No.
5,931,805).
[0005] The ultrasonic energy produced by an ultrasonic probe is in
the form of very intense, high frequency sound vibrations that
result in powerful chemical and physical reactions in the water
molecules within a body tissue or surrounding fluids in proximity
to the probe. These reactions ultimately result in a process called
"cavitation," which can be thought of as a form of cold (i.e.,
non-thermal) boiling of the water in the body tissue, such that
microscopic bubbles are rapidly created and destroyed in the water
creating cavities in their wake. As surrounding water molecules
rush in to fill the cavity created by collapsed bubbles, they
collide with each other with great force. This process is called
cavitation and results in shock waves running outward from the
collapsed bubbles which can fragment or ablate material such as
surrounding tissue in the vicinity of the probe.
[0006] Some ultrasonic probes include a mechanism for irrigating an
area where the ultrasonic treatment is being performed (e.g., a
body cavity or lumen) to wash tissue debris from the area.
Mechanisms used for irrigation or aspiration described in the art
are generally structured such that they increase the overall
cross-sectional profile of the probe, by including inner and outer
concentric lumens within the probe to provide irrigation and
aspiration channels for removal of particulate matter. In addition
to making the probe more invasive, prior art probes also maintain a
strict orientation of the aspiration and the irrigation mechanism,
such that the inner and outer lumens for irrigation and aspiration
remain in a fixed position relative to one another, which is
generally closely adjacent the area of treatment. Thus, the
irrigation lumen does not extend beyond the suction lumen (i.e.,
there is no movement of the lumens relative to one another) and any
aspiration is limited to picking up fluid and/or tissue remnants
within the defined distance between the two lumens.
[0007] Another drawback of existing ultrasonic medical probes is
that they typically remove tissue relatively slowly in comparison
to instruments that excise tissue by mechanical cutting. Part of
the reason for this is that existing ultrasonic devices rely on a
longitudinal vibration of the tip of the probe for their
tissue-disrupting effects. Because the tip of the probe is vibrated
in a direction in line with the longitudinal axis of the probe, a
tissue-destroying effect is only generated at the tip of the probe.
One solution that has been proposed is to vibrate the tip of the
probe in a direction other than perpendicular to the longitudinal
axis of the probe, in addition to vibrating the tip in the
longitudinal direction. It is proposed that such motions will
supplement the main point of tissue destruction, which is at the
probe tip, since efficiency is determined by surface area of the
probe tip. For example, U.S. Pat. No. 4,961,424 to Kubota, et al.
discloses an ultrasonic treatment device that produces both a
primary longitudinal motion, and a supplementary lateral motion of
the probe tip to increase the tissue disrupting efficiency. The
Kubota, et al. device, however, still relies primarily on the tip
of the probe to act as a working surface. The ancillary lateral
motion of the probe is intended to provide an incremental
efficiency for the device operation. Thus, while destruction of
tissue in proximity to the tip of the probe is more efficient,
tissue destruction is still predominantly limited to the area in
the immediate vicinity at the tip of the probe. The said invention
is therefore limited in its ability to ablate tissue within inner
surfaces of cylindrical blood vessels, for example, in vascular
occlusions. U.S. Pat. No. 4,504,264 to Kelman discloses an
ultrasonic treatment device containing a probe that is capable of
longitudinal vibrations and lateral oscillation. The said invention
is intended to improve the efficiency of ultrasonic tissue removal
by providing a dual function of a fragmentation and a cutting
device. Tissue fragmentation is caused primarily by oscillating the
tip of the probe in addition to relying on longitudinal vibrations
of the probe, while the lateral oscillations. Tissue fragmentation
is caused primarily at the tip of the device, while the oscillatory
motion can be employed by the surgeon to cut tissue, thereby
increasing efficiency of surgical procedures. The foregoing
inventions also require complex instrument design that require
incorporation of a plurality of electrodes, ultrasound frequency
generating elements, switches or voltage controllers.
[0008] The longitudinal probe vibration required for tissue
ablation in prior art devices necessitates the probe lengths to be
relatively short, since use of long probes result in a substantial
loss of ultrasonic energy at the probe tip due to thermal
dissipation and undesirable horizontal vibration that interferes
with the required longitudinal vibration.
[0009] Although narrow probe diameters are advantages especially
for negotiation through narrow blood vessels and occluded arteries,
the utilization of such probes have been precluded by inability to
effectively control the vibrational amplitude of thin probes, that
result in potential damage to the probe and greater risk of tissue
damage resulting from their use. The use of narrow-diameter probes
have been disclosed in the art for providing greater
maneuverability ease of insertion in narrow blood vessels. U.S.
Pat. No. 4,920,954 to Allinger discloses a narrow diameter
ultrasonic device wherein a rigid sleeve is used to prevent
transverse vibrations. U.S. Pat. No. 5,380,274 discloses a narrow
diameter probe for improved longitudinal vibration having a sheath
to inhibit transverse vibration. U.S. Pat. No. 5,469,853 to Law
discloses a thin, longitudinally vibrating ultrasonic device with a
bendable sheath that facilitates directing the probe within narrow
blood vessels. While the prior art has focused on the need for
using sheaths on thin ultrasonic devices, their use has been
entirely to prevent transverse vibrations of the device and to
protect such devices from damage resulting from such vibrations
[0010] Based on the aforementioned limitations of ultrasonic probes
in the art, there is a need for an ultrasonic probe functioning in
a transverse mode that further obviates the shortcomings and that
further overcomes limitations imposed by of narrow diameter
requirements for efficient operation of such probes for rapid
tissue ablation. Transversely vibrating ultrasonic probes for
tissue ablation are described in the Applicant's co-pending
provisional applications U.S. Ser. No. 60/178,901 and 60/225,060,
and Ser. No. 09/776,015, now U.S. Pat. No. 6,652,547, which further
describe the design parameters for such a probe and its use in
ultrasonic devices for tissue ablation. The entirety of these
applications are herein incorporated by reference.
[0011] This limitation has precluded the use of ultrasonic tissue
ablation devices in surgical procedures wherein access to vascular
occlusion requires traversing an anatomically lengthy or sharply
curved path along tubular vessels. The self-suggesting idea of
effecting ultrasonic transmission through a plurality of flexible
thin wires has been found impracticable because (1) relatively high
power (.about.25 watts) is required to deliver sufficient energy to
the probe tip, and (2) such thin wires tend to perform buckling
vibrations, resulting in almost the entire ultrasonic power
introduced in the probe is dissipated during its passage to the
probe tip.
[0012] The relatively high-energy requirement for such devices
causes probe heating that can cause fibrin to re-clot blood within
the occluded vessel (thermally induced re-occlusion). Additionally,
the elevation in probe temperature is not just limited to probe
tip, but also occurs at points wherein the narrow diameter wire
probes have to bend to conform to the shape of the blood vessel,
thereby limiting causing probe damage and limiting its reuse.
[0013] A single thick wire probe on the other hand, cannot
negotiate the anatomical curves of tubular arterial and venous
vessels due to its inflexibility, and could cause damage to the
interior wall of such vessels. Currently, such exchange procedures
are not possible because ultrasonic probes used in endovascular
procedures are permanently attached to the transducer energy source
or a probe handle coupled to such source, such as for example, by
welding, thereby precluding probe detachment. Moreover, since probe
vibration in such devices in a longitudinal mode, i.e. along the
probe longitudinal axis, a proximal contact with the transducer or
the probe handle segment connect is essential to prevent a
"hammering" effect that can result in probe damage.
SUMMARY OF THE INVENTION
[0014] The present invention relates to an ultrasonic device
comprising an elongated catheter probe vibrating substantially in a
direction transverse to the probe longitudinal axis and capable of
emulsifying endovascular materials, particularly tissue. The
diameter of the catheter probe is sufficiently small to confer
flexibility on said probe so as to enable its negotiation through
narrow and anatomically curved tubular vessels to the site of an
occlusion that is remotely located from the point of probe
insertion into the body. The catheter probe of the invention is
designed to work in conjunction with standard vascular introducers
and guide catheters. Another aspect of the invention is to provide
a rapidly attachable and detachable or "quick
attachment-detachment" means (referred to hereinafter as "QAD") for
the catheter probe to and from the ultrasonic energy source,
thereby enabling manipulation and positioning of the probe within
the body vessel without being limited by the relatively bulky
energy generating source. The catheter probe of the invention
additionally comprises a concentric tubular sheath to facilitate
fluid irrigation, aspiration of ablated tissue fragments and
introducing a therapeutic drug to the site of occlusion.
[0015] An ultrasonic probe vibrating in a transverse mode for
removal of occlusions in blood vessels has been disclosed in
applicants' co-pending application Ser. No. 09/776,015, now U.S.
Pat. No. 6,652,547, the entirety of which is incorporated herein as
reference. The said reference discloses an ultrasonic device in
which a transducer is connected to a probe with a flexible tip
capable of vibrating in a direction transverse to the probe
longitudinal axis. With such a probe a situation may arise where it
will be desirable to utilize an elongated probe resembling a
catheter guide-wire probe to make possible exchange procedures
often used in angioplasty.
[0016] In general, it is an object of the invention to provide an
ultrasonic medical device for removing vascular occlusions
comprising a detachable elongated catheter guide wire probe capable
of vibrating in a transverse mode.
[0017] Another object of the invention is to provide an elongated
guide wire probe of the above character of the above character that
is and comparable in size to existing guide wires.
[0018] Another object of the invention is to provide an elongated
guide wire probe of the above character which includes a quick
attachment-detachment means to an ultrasound energy source.
[0019] Another object of the invention is to provide an elongated
guide wire probe of the above characteristics which is compatible
with the existing guide wire exchange systems.
[0020] Another object of the invention is to provide a probe
attachment-detachment means comprising a coupling assembly.
[0021] Yet another object of the invention is to provide a guide
wire of the above character which can be inserted, retracted or
torqued in a detached mode to prevent interference with the probe
handle and the ultrasound transducer.
[0022] A further object of the invention is to provide a guide wire
assembly and system and apparatus utilizing the same of the above
character, which permits intravascular ultrasonic tissue
ablation.
[0023] Additional objects and features of the invention will appear
from the following description in which the preferred embodiments
are set forth in detail in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order that the invention may be more readily understood,
reference is made to the accompanying figures, which illustrate
diagramatically and by way of example, several embodiments thereof
and in which:
[0025] FIG. 1 is a general view of the elongated flexible wire
probe catheter of the invention.
[0026] FIGS. 2A and 2B show a varied diameter probe, QAD
collet-horn assembly and locking nut in disassembled (2A) and
assembled (2B) configurations. FIG. 2C shows an assembled
configuration of a uniformly small diameter wire probe.
[0027] FIG. 3 shows a cross sectional view of the probe assembled
to QAD collet (Version 1) assembly.
[0028] FIGS. 4A and 4B show the locking nut viewed from the
opposite cylindrical ends.
[0029] FIG. 5 shows a cross sectional view of the locking nut
coupling the probe to the QAD collet-horn assembly.
[0030] FIG. 6 shows the threaded horn component of the QAD
collet-horn assembly.
[0031] FIG. 7 shows scaled and cross-sectional views of a second
preferred version of the QAD collet assembly.
[0032] FIGS. 8A and 8B show the QAD collet rod and housing
assemblies of the second preferred version.
[0033] FIG. 9 shows scaled and cross-sectional views of a third
preferred version of the QAD collet assembly.
[0034] FIGS. 10A and 10B show the QAD collet rod and housing
assemblies of the third preferred version.
[0035] FIG. 11 shows scaled and cross-sectional views of a fourth
preferred version of the QAD collet assembly.
[0036] FIGS. 12A, 12B and 12C show the collet, QAD base component
and compression housing of the fourth preferred version.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The following terms and definitions are used herein:
[0038] "Cavitation" as used herein refers to shock waves produced
by ultrasonic vibration, wherein the vibration creates a plurality
of microscopic bubbles which rapidly collapse, resulting in
molecular collision by water molecules which collide with force
thereby producing the shock waves.
[0039] "Fenestration" as used herein refers to an aperture, window,
opening, hole, or space.
[0040] "Node" as used herein refers to a region of minimum energy
emitted by an ultrasonic probe at or proximal to a specific
location along the longitudinal axis probe.
[0041] "Anti-node" as used herein refers to a region of maximum
energy emitted by an ultrasonic probe at or proximal to a specific
location along the longitudinal axis probe.
[0042] "Probe" as used herein refers to a device capable of being
adapted to an ultrasonic generator means, which is capable of
propagating the energy emitted by the ultrasonic generator means
along its length, resolving this energy into effective cavitational
energy at a specific resonance (defined by a plurality of nodes and
anti-nodes at a pre-determined locations defined as "active area"
of the probe) and is capable of acoustic impedance transformation
of ultrasound energy to mechanical energy.
[0043] "Sheath" as used herein refers to a device for covering,
encasing, or shielding in whole or in part, a probe or portion
thereof connected to an ultrasonic generation means.
[0044] "Transverse" as used herein refers to vibration of a probe
at right angles to the axis of a probe. A "transverse wave" as used
herein is a wave propagated along an ultrasonic probe in which the
direction of the disturbance at each point of the medium is
perpendicular to the wave vector.
[0045] "Tuning" as used herein refers to a process of adjusting the
frequency of the ultrasonic generator means to select a frequency
that establishes a standing wave along the length of the probe.
[0046] The present invention provides an ultrasonic medical device
operating in a transverse mode for removing a vascular occlusion by
causing fragmentation of occlusion materials such as tissue.
Because the device is minimally invasive, flexible and articulable,
it can be inserted into narrow, tortuous blood vessels without
risking damage to those vessels. Transverse vibration of the probe
in such a device generates multiple nodes of cavitation energy
along the longitudinal axis of the probe, which are resolved into
caviational nodes emanating radially from these nodes at a specific
points along the active portion of the probe. The occlusion tissue
is fragmented to debris approximately of sub-micron sizes, and the
transverse vibration generates a retrograde flow of debris that
carries the debris away from the probe tip.
[0047] The transverse mode of vibration of the ultrasonic probe
according to the invention differs from the axial (or longitudinal)
mode of vibration that is conventional in the prior art. Rather
than vibrating in the axial direction, the probe vibrates
exclusively in a direction transverse (perpendicular) to the axial
direction. As a consequence of the transverse vibration of the
probe, the tissue-destroying effects of the device are not limited
to those regions of a tissue coming into contact with the tip of
the probe. Rather, as the active portion of the probe is positioned
in proximity to an occlusion or other blockage of a blood vessel,
the tissue is removed in all areas adjacent to the multiplicity of
energy anti-nodes that are produced along the entire length of the
probe, typically in a region having a radius of up to about 6 mm
around the probe.
[0048] By eliminating the axial motion of the probe and allowing
transverse vibrations only, fragmentation of large areas of tissue
spanning the entire length of the active portion of the probe due
to generation of multiple cavitational nodes along the probe length
perpendicular to the probe axis. Since substantially larger
affected areas within an occluded blood vessel can be denuded of
the occluded tissue in a short time, actual treatment time using
the transverse mode ultrasonic medical device according to the
invention is greatly reduced as compared to methods using prior art
probes that primarily utilize longitudinal vibration (along probe
axis) for tissue ablation. A distinguishing feature of the present
invention is the ability to utilize probes of extremely small
diameter (about 0.025" and smaller) compared to prior art probes
without loss of efficiency, since the tissue fragmentation process
in not dependent on area of the probe tip (distal end). Highly
flexible probes can therefore, be designed to mimic device shapes
that enable facile insertion into highly occluded or extremely
narrow interstices within blood vessels. Another advantage provided
by the present invention is its ability to rapidly remove occlusion
tissue from large areas within cylindrical or tubular surfaces such
as arteries and arterial valves or selected areas within the
tubular walls, which is not possible by previously disclosed
devices that rely on the longitudinal vibrating probe tip for
effecting tissue fragmentation.
[0049] The number of nodes occurring along the axial length of the
probe is modulated by changing the frequency of energy supplied by
the ultrasonic generator. The exact frequency, however, is not
critical and a ultrasonic generator run at, for example, 20 kHz is
generally sufficient to create an effective number of tissue
destroying nodes along the axial length of the probe. In addition,
as will be appreciated by those skilled in the art, it is possible
to adjust the dimensions of the probe, including diameter, length,
and distance to the ultrasonic energy generator, in order to affect
the number and spacing of nodes along the probe. The present
invention allows the use of ultrasonic energy to be applied to
tissue selectively, because the probe conducts energy across a
frequency range of from about 20 kHz through about 80 kHz. The
amount of ultrasonic energy to be applied to a particular treatment
site is a function of the amplitude and frequency of vibration of
the probe. In general, the amplitude or throw rate of the energy is
in the range of 150 microns to 250 microns, and the frequency in
the range of 20,000 to 80,000 Hertz (20-80 kHz). In the currently
preferred embodiment, the frequency of ultrasonic energy is from
20,000 Hertz to 35,000 Hertz (20-35 kHz). Frequencies in this range
are specifically destructive of hydrated (water-laden) tissues and
vascular occlusive material, while substantially ineffective toward
high-collagen connective tissue, or other fibrous tissues such as,
for example, vascular tissues, skin or muscle tissues.
[0050] In a preferred embodiment, the ultrasonic medical device of
the present invention, comprises an ultrasonic generator that is
mechanically coupled to a probe having a proximal and distal end
that is capable of oscillating in a direction transverse to its
longitudinal axis. Alternatively, a magneto-strictive generator may
be used for generation of ultrasound energy. The preferred
generator is a piezoelectric transducer that is mechanically
coupled to the probe to enable transfer of ultrasonic excitation
energy and cause the probe to oscillate in a transverse direction
relative to its longitudinal axis. The device is designed to have a
small cross-sectional profile, which also allows the probe to flex
along its length, thereby allowing it to be used in a minimally
invasive manner. Transverse oscillation of the probe generates a
plurality of cavitation nodes along the longitudinal axis of the
member, thereby efficiently destroying the occlusion. A significant
feature of the invention is the retrograde movement of debris,
e.g., away from the tip of the probe i.e. backwards up along the
shaft of the probe that results from the transversely generated
energy. The amount of cavitation energy to be applied to a
particular site requiring treatment is a function of the amplitude
and frequency of vibration of the probe, as well as the
longitudinal length of the probe tip, the proximity of the tip to a
tissue, and the degree to which the probe tip is exposed to the
tissues.
[0051] A distinguishing feature of the present invention is the
ability to utilize probes of extremely small diameter (narrow
diameter probes) compared to previously disclosed devices (large
diameter probes) without loss of efficiency or efficacy, since the
tissue fragmentation process in not dependent on area of the probe
tip (distal end). Highly flexible probes can therefore be obtained
to mimic device shapes that enable facile insertion into highly
occluded or extremely narrow interstices without resulting in
breakage of the probe or puncture or damage of the tissue or body
cavity while ensuring optimal results.
[0052] A second distinguishing feature of the small diameter probes
of the invention is that the probe diameter is approximately the
same over their entire length, that is,--the active tip segment
(distal end) and the rear segment (proximal end) of the probes are
approximately similar in diameter. In a preferred embodiment the
probe diameters at the proximal and distal ends respectively are
about 0.025 inch. An advantage of the shape configuration of the
probes of the invention is that they are adaptable to currently
used standard vascular introducers. Since the rear segment
(proximal end) of the probes have no non-cylindrical shape or
"bulk", catheters and guides can be introduced over the ends of the
elongated wire probes of the invention, thereby--allowing their use
in standard-configuration endovascular procedures.
[0053] The ultrasonic device of the invention comprises a
longitudinal resonator such as for example, a Mason (Langevin) horn
that is in intimate contact with an elongated catheter wire probe
through a coupling assembly. The horn assembly is in turn,
connected to an ultrasound energy source. Upon device activation,
ultrasonic energy from the source is transmitted to the horn
assembly wherein it is amplified by the horn and in turn,
transmitted to the probe thorough the coupling assembly. Transverse
vibrational modes along the longitudinal axis of the probe that lie
within the horn resonance are excited.
[0054] The coupling between the elongated probe and the horn is
adjusted so as to present a relatively large impedance mismatch,
and be located at a node of the horn. Longitudinal waves impinging
on the coupling interface are either reflected back into the horn
or transmitted out to the probe in proportion to the degree of
impedance mismatch at the said coupling interface. In a preferred
embodiment, the coupling interface is configured in a manner so as
to reflect most of the energy back into the horn. The horn
therefore, essentially acts as an energy storage device or
"reservoir", thereby allowing a substantial increase in drive
amplitude.
[0055] Since the energy coupled into the elongated probe is a small
portion of the energy reflected back to the horn, changes in the
transverse oscillation on the probe due to bending or damping have
minimal effect on the longitudinal resonance of the horn. By
decoupling the transverse probe oscillation from the longitudinal
horn resonance, the electrical source of the vibrations
(piezoelectric or magnetostrictive) to compensate only for shifts
in the resonant frequency of the horn (due to temperature,
manufacturing variations, etc.). The drive mechanism is therefore,
completely independent of vibrational motions on the probe.
[0056] The transverse vibrating elongated probe of the invention
does not require its terminal end be permanently affixed in
intimate contact to the horn assembly, since a "hammering" action
associated with longitudinal vibration is absent. The elongated
probe of the invention can therefore be coupled, and not welded, to
the horn via a coupling assembly that grips the probe along the
cylindrical surface near its terminal end in a non-permanent way.
The coupling assembly of the invention therefore, allows for quick
attachment and detachment of the probe from the horn assembly and
source components, thereby enabling manipulation of the elongated
flexible probe into anatomically curved blood vessels without
hindrance by the bulky horn and energy source components. The probe
of the invention can therefore be inserted into a venal cavity,
positioned near the occlusion site prior to coupling it to the horn
source assembly. The device is then activated to effect tissue
ablation and removal, after which the probe is decoupled from the
horn and source component for its easy removal from the cavity.
[0057] In a preferred embodiment a longitudinal horn is coupled to
an elongated wire catheter through a coupling assembly that is
rapidly attachable and detachable. In a most preferred embodiment,
the coupling assembly comprises a quick attachment-detachment (QAD)
collet. The attachment of the coupling assembly to the elongated
probe is located at a node and the dimensions are scaled (the
collet head has a relatively larger diameter at the attachment
point than the diameter of the probe) to produce an optimal
impedance mismatch. In another embodiment of the invention, the
elongated probe is permanently attached to the coupling assembly by
a welded joint.
[0058] The QAD collet of the invention is housed within an
externally mounted compressive clamp that is capable of exerting a
compressive force on the collet after insertion of the ultrasonic
probe into said collet, thereby causing a non-removable attachment
of the probe to the coupling assembly. The collet therefore,
applies a restraining inwardly compressive force on the probe in a
manner so as to not torque or twist the probe material. As a
result, the probe can be subject to a multiple attachment and
detachment procedures, without causing probe destruction, thereby
enabling its extended reuse in surgical procedures.
[0059] The collet of the invention comprises is at least one slit
in its terminal compressible segment; alternatively it comprises of
a plurality of slits. In a preferred embodiment, the collet,
compressive clamp and housing assembly are all attached to the
device handle by a mechanical assembly means, such as for example,
a screw thread comprising a locking nut, bayonet mount, keyless
chuck and cam fittings. Alternatively, the rear segment of the
mechanical assembly means is a hollow cylindrical segment
comprising a screw thread that allows insertion and attachment of
the ultrasonic device handle containing a drive assembly containing
a complementary thread arrangement to be inserted into and
non-removably attached to said cylindrical segment by applying a
torque. In another preferred embodiment, ultrasonic probe is
mounted to the attachment means such that the collet holds the
probe at a point greater than about 1 mm and less than about 30
from the probe terminal end, or is adjustable to any point in
between, to optimize probe vibration based on the frequency of the
ultrasound transducer in the device handle. In another preferred
embodiment, the probe attachment means comprising the external
compressive clamp, collet and collet housing are all attached to
the operating handle of the ultrasonic device.
[0060] In another preferred embodiment the collet is retained
within the confines of an outer shell that is attached to the
collet housing segment of the probe attachment means that to
precludes its disassembly, thereby preventing either loss or
disengagement of the collet. The outer shell compresses the collet
to engage contact with the probe upon its tightening to the collet
housing assembly by application of torque, causing the probe to be
attached to the collet in a non-removable manner. An inner bias is
maintained within the rear portion of the attachment means such
that a portion of the probe protruding from the proximal end of the
collet maintains contact with the surface of the collet housing
within the coupling assembly.
[0061] The terminal ends of the collet are tapered so as to allow
the collet to maintain a true axial orientation within the coupling
assembly, thereby enabling multiple insertions and retractions of
the probe into and from the collet prior to and after device use,
without causing the probe to kink. Additionally, the shape of the
proximal end of the segment (rear segment with respect to the
entering probe), so as to maximize contact area between the collet
and the distal end of the transducer-sound conductor assembly (the
"drive assembly"). The collet proximal end is shaped in any
suitable form providing maximal contact area, including conical,
frusto-conical, triangular, square, oblong, and ovoid, upon probe
attachment to the collet within the housing assembly, which in turn
maintains intimate contact with the drive assembly. The four
component assembly that include probe, outer ring, collet and rear
drive assembly, form a single assembled component in the device
operational state, in terms of their combined ability to transmit
sound energy from the transducer in the drive assembly to the probe
without energy loss thermally or mechanically. The collets of the
invention can be designed to accommodate a series of probe
diameters, or for a specific probe diameter by varying the inner
diameter of the cylindrical slot. The outer diameters of the
collets, however remain unchanged, thereby allowing attachment of
probes of differing diameters into a universal coupling and drive
assembly.
[0062] The elongated probe of the invention is either a single
diameter wire with a uniform cross section offering flexural
stiffness along its entire length, or is tapered or stepped along
its length to control the amplitude of the transverse wave along
its entire longitudinal axis. Alternatively, the probe can be
cross-sectionally non-cylindrical that is capable of providing both
flexural stiffness and support energy conversion along its entire
length. The length or the elongated probe of the invention is
chosen so as to be resonant in either in an exclusively transverse
mode, or be resonant in combination of transverse and longitudinal
modes to provide a wider operating range. In a preferred
embodiment, the elongated probe of the invention is chosen to be
from about 30 cm to about 300 cm in length. In a most preferred
embodiment, the elongated probe of the invention has a length of
about 70 cm to about 210 cm in length. Suitable probe materials
include metallic materials and metallic alloys suited for
ultrasound energy transmission. In a preferred embodiment the
metallic material comprising the elongated probe is titanium.
[0063] In another preferred embodiment, the elongated probe of the
invention is circumferentially enclosed in a sheath that provides a
conduit for irrigation fluids, aspiration of fragmented tissue, or
for delivery of therapeutic drugs to the occlusion site. The said
sheath can extend either partially or over the entirety of the
probe, and can additionally comprise of fenestrations for directing
ultrasonic energy from the probe at specific locations within venal
cavities for selective ablation of tissue. An ultrasonic tissue
ablation device comprising a sheath for removal of occlusions in
blood vessels has been disclosed in applicants' co-pending
application Ser. No. 09/776,015, now U.S. Pat. No. 6,652,547, the
entirety of which is incorporated herein as reference.
[0064] In one embodiment, the elongated catheter probe is comprised
of a proximal end and a distal end with respect to the horn
assembly, and is in the form of a long small diameter wire
incorporating a series of telescoping segments along its
longitudinal axis, such that the largest diameter segment is
proximal to the horn assembly, and either continually or segmental,
sequentially decreasing diameters from the proximal to the distal
end. With reference to the probe, coupling and horn assemblies as
shown in the figures describing the present invention, the proximal
end for each component refers to the end farthest from the probe
tip, while distal end refers to the end closest to the probe tip.
In another embodiment, the elongated probe is comprised of a
non-segmented, uniformly narrow diameter wire, such as for example
a guide wire, such as those used in insertion of catheters.
[0065] Referring now to FIG. 1, a preferred embodiment of the
elongated ultrasonic probe 10 of the invention comprising a
proximal end 12 and a distal end 22, is shown. Probe 10 is coupled
to a transducer and sound conductor assembly (not shown)
constructed in accordance with the present invention that function
as generation and transmission sources respectively, of ultrasound
energy for activation of said probe. The generation source may or
may not be a physical part of the device itself. The probe 10
transmits ultrasonic energy received from the sound conductor along
its length, and is capable of engaging the sound conductor
component at its proximal end 12 via a coupling assembly with
sufficient restraint to form an acoustical mass that can propagate
the ultrasonic energy provided by the source. The probe diameter
decreases at defined segment intervals 14, 18, and 20. Segment 20
because of its small diameter, is capable of flexing more than
segments 14 and 18, thereby enabling probe 10 to generate more
cavitation energy along segment 20 distal end 22. Energy from the
generator is transmitted along the length of the probe, causing the
probe to vibrate in a direction that is transverse to its
longitudinal axis. Probe interval 14 has a head segment 24 for
engaging the coupling assembly for attachment to the sound
conductor-transducer assembly. In a preferred embodiment, the sound
conductor component of the invention for providing, amplifying and
transferring ultrasonic energy to elongated probe 10 is a Mason
(Langevin) horn that is detachably connected to said probe through
a coupling assembly.
[0066] Referring now to FIGS. 2A-B, the unassembled and assembled
views of individual components comprising the varied diameter probe
and sound conductor elements, and the coupling assembly are
illustrated. FIG. 2A shows the individual components comprising
elongated probe 10, horn assembly 34 comprising a proximal end 38
and a comprising a cylindrical slot at the distal end 36, which
includes the horn and coupling assembly components, elongated probe
10 and locking nut 30. The coupling assembly components comprising
threading arrangements 40 and 42, cylindrical slot 36, and locking
nut 30. Attachment of proximal end 12 of probe 10 is accomplished
by insertion of probe head 24 into the cylindrical slot at distal
end 36 of the horn assembly, followed by "threading" the probe
through locking nut 30 to enable threads on the inner surface of
locking nut 30 (not shown) to engage complementary threads 40,
thereby providing intimate contact between probe proximal end 12
and the distal end 36 of the horn assembly. The probe attachment is
rendered to be mechanically rigid by tightening locking nut 30.
FIG. 2B shows the enlongated varied diameter probe attached to the
horn assembly and held rigidly by the coupling assembly and
maintaining intimate contact between the "coupled" components. FIG.
2C shows a similar assembly comprising a uniform narrow diameter
wire probe of the invention.
[0067] FIG. 3 shows a cross-sectional view of the probe-horn
assembly shown in a "coupled" mode. The attachment means comprising
the coupling assembly of the invention utilized to "couple" the
elongated probe to the horn assembly is chosen from conventional
means of connecting physically separated components in a manner so
as to provide a rigid joining of said components while maintaining
intimate material surface contact between the components in the
"coupled" state. Suitable attachment means of the present invention
include a locking nut comprising a screw thread, and a bayonet or
ring clamp mechanism to effect coupling between the elongated probe
and the horn assembly. FIGS. 4A and 4B show opposite-end views of a
preferred embodiment of the locking means, comprising a locking nut
30 consisting a screw thread arrangement 44 that is capable of
engaging a complementary thread arrangement located along the outer
diameter of the distal end of the horn assembly. When engaged with
the horn assembly 34 with the elongated probe 10 positioned
proximally to provide "coupling", locking nut 30 provides a rigid
interface between the probe and horn components and ensures
intimate contact between the terminal end surfaces of the said
components, which is important for efficient transmission of
ultrasound energy to the probe. FIG. 5 shows a cross-sectional view
of the horn assembly 34 and elongated probe 10 "coupled" by the
locking nut 30 of the invention by engaging screw thread 44 with
complementary threads 40 in the horn assembly.
[0068] Now referring to FIG. 6, the horn assembly 34 comprises of a
distal end 36 that is capable of being coupled to the enlongated
probe of the invention, and a proximal end 38 that is coupled to a
transducer (not shown) functioning as an ultrasound energy source
by screw threads 40 and 42 located terminally at either end. As
mentioned previously, horn assembly 34 comprising the sound
conductor or "horn" functions as an energy reservoir that allows
only a small fraction of the energy transmitted by the source to
the probe, thereby minimizing energy loss due to probe bending or
damping that can occur when it is inserted into blood vessels.
[0069] FIG. 7 shows disassembled and assembled views of another
preferred embodiment of the probe attachment means of the
invention, including cross-sectional views in the assembled state,
that includes a coupling assembly comprising a "quick
attachment/detachment" (QAD) collet rod 48 and housing assembly 54
that enables efficient coupling of the elongated catheter probe to
the horn assembly (not shown). As seen in the figure, collet rod 48
is configured to slideably receive and retain the proximal end of
the ultrasonic probe of the invention within the interior volume of
collet housing 64, and restrained in a rigid, non-removable manner
by socket screw 58, which comprises a cylindrical head 60 with a
uniformly flat end to facilitate its intimate contact with other
device components, including the terminal end of the horn assembly.
FIG. 7 also shows regular and expanded cross-sectional views of QAD
collet rod 48 inserted into collet housing 64 that is non-removably
retained within said housing by socket screw 58. As seen in segment
"C" of the cross-sectional view, the inner surface of collet
housing tapers circumferentially outwardly at the distal end so as
to enable partial insertion of the cylindrically slotted head of
the QAD collet rod. The inner diameter of the circumferentially
tapered section of the housing is chosen to be slightly larger then
the insertable segment QAD collet rod head so as to create a
"clearance" that facilitates easy insertion and retraction of the
said collet rod (shown in the detail cross-sectional view in FIG.
7).
[0070] As shown in FIG. 8A, QAD collet rod 48 is comprised of a
hollow cylindrical segment 49 with a proximal end 50 and a head
segment 51 at distal end 52 (the end farthest from the collet
housing and horn assembly) with a diameter larger than that of
cylindrical segment. The head segment at distal end 52 comprises a
compressible slit 54 that is capable of accommodating the proximal
end of the elongated probe. The proximal end 50 of the QAD collet
rod comprises a hollow cylindrical opening containing a screw
thread inscribed along the inner surface of said opening that is
capable of receiving a retaining a socket screw 58 (shown in FIG.
7) inserted from the proximal end of the QAD collet housing, so as
to render collet rod 48 with attached probe to be rigidly and
non-removably restrained within said collet housing. As shown in
FIG. 8B, collet housing 64 comprises a hollow cylinder with a
distal end 68 capable receiving the entire cylindrical segment 49
of the probe QAD collet rod (FIG. 8A) and part of the cylindrically
slotted head segment 51 when the collet rod is inserted at its
proximal end 50 into collet housing 64, and a proximal end 72
comprising a screw-thread 74 along the outer surface. The proximal
end 72 of collet housing further comprises a screw thread 74 on its
outer surface capable of engaging the terminal end of a horn
assembly in a manner so as to provide intimate contact between the
horn and the flat head of socket screw 58 restraining QAD collet
rod 48 attached to the elongated probe, thereby enabling
transmission of ultrasound energy from the horn to the elongated
probe.
[0071] The socket screw 58 of the invention is capable of being
"tightened" by applying a torque by conventional methods causing it
to simultaneously engage the thread assemblies if of collet rod
housing 64 and the QAD collet rod 48 respectively, after insertion
of the collet rod into said housing. Such a tightening action which
is performed after attachment of the elongated probe to collet rod
48 by insertion of the probe into slotted head 54 at the distal end
52 of the collet rod causes retraction of the said slotted head
into the collet housing. This in turn, results in elimination of
the "clearance" between the collet rod and the collet housing,
causing a contraction in the diameter of the slot in the head of
collet rod and in turn, resulting in 1) its intimate contact with
the surface of the proximal end of the inserted elongated probe,
and 2) restraining the probe in a non-detachable manner to the
collet rod-housing coupling assembly. The rigid and non-removable
mode of probe attachment to the said coupling assembly enables
transmission of ultrasound energy from a horn assembly attached to
the collet rod-housing coupling assembly to the elongated probe so
as to cause it to vibrate in a transverse mode, and hence provide
cavitation energy for tissue destruction. Conversely, the probe is
detached (or "de-coupled") from the collet rod-housing coupling
assembly by loosening the socket screw 58 by application of a
torque in a direction opposite to that used for the probe
attachment process.
[0072] FIG. 9 shows disassembled and assembled views of another
preferred embodiment of the probe attachment means of the
invention, including cross-sectional views in the assembled state,
consisting a QAD collet rod-housing assembly that comprises a
outwardly cylindrically tapered collet housing component 80 with a
proximal end 86 and a distal end 90, further comprising a centrally
located cylindrical bore with open ends extending through its
longitudinal axis that is capable of slideably receiving and
retaining a collet rod. As seen in segment "C" of the
cross-sectional view in FIG. 9, the inner surface of collet housing
tapers circumferentially outwardly at the distal end so as to
enable partial insertion of the cylindrically slotted head of the
QAD collet rod. The inner diameter of the circumferentially tapered
section of the housing is chosen to be slightly larger then the
insertable segment QAD collet rod head so as to create a
"clearance" that facilitates easy insertion and retraction of the
said collet rod (shown in the detail cross-sectional view). The
cross-sectional view of the FIG. 9 shows the QAD collet rod
restrained within the collet rod housing by a locking nut 88. FIGS.
10A and 10B show the collet rod and collet housing respectively, of
the embodiment. As seen in FIG. 10A, QAD collet rod comprises a
solid cylindrical body 94 with a head segment 98 attached at
proximal end 92. A longitudinal slit 99 extends from head segment
98 partially into the cylindrical body 94. The distal end 96 of
cylindrical body 94 comprises a thread assembly 100. As seen in
FIG. 10B, collet housing 80 comprises a cylindrical rod with a
continuously decreasing external diameter from proximal end 86 to
distal end 90, further comprising a centrally located cylindrical
inner bore extending along its entire length providing openings at
both ends. The diameter of the bore increases proximally to the
distal end so as to circumferentially taper outwardly in a manner
permitting partial insertion of head segment 98 of the collet rod.
The cylindrical bore of the collet housing 80 is capable of
slideably receiving a collet rod 94 such that thread assembly 100
of the said collet rod extends beyond proximal end 86 to permit a
rigid and non-removable attachment of the collet rod by engaging
thread assembly 100 with locking nut 88 (shown in FIG. 9). The
locking nut performs a similar function and in a manner that is
substantially similar to that of the restraining screw described in
a previous embodiment (FIG. 7) in enabling the elongated probe to
be non-removably attached to and detached from the QCD collet rod
for operation of the device as described previously. Upon rigid
non-removable attachment of the elongated probe to the coupling
assembly, the threading 88 of the collet housing is engaged to
complementary threading of the horn assembly (not shown) of the
assembly so as to render intimate contact of the sound conductor
(horn) in said horn assembly with the proximal end 92 of the collet
rod to enable transmission of ultrasound energy from the horn to
the elongated probe attached at distal end 96 of the collet
rod.
[0073] FIG. 11 shows another preferred embodiment of probe coupling
assembly of the invention, including a cross-sectional view,
comprising a QAD collet 105 that is insertable into a "compression"
collet housing component 115 comprising a circular bore 114 that is
detachably connected to a QAD base component 120. As seen in FIG.
12A, QAD collet 105 comprises a cylindrical segment 106 with a
cylindrical slot 108 extending through its longitudinal axis that
is capable of slideably receiving the proximal end of the elongated
probe, and symmetrically tapered at proximal and distal ends 110.
As seen in FIG. 12B, QAD base component 120 comprises a conical
slot 130 at the cylindrical distal end capable of accommodating the
one of the symmetrically tapered ends 110 of the collet. QAD base
component 120 further comprises a thread assembly 132 located along
its outer circumference proximal to its distal end, that is capable
of engaging complementary threads in the QAD compression housing
component 115. The proximal end 136 of the base component contains
a thread assembly 134 along the outer circumference that is capable
of engaging and attaching to the horn assembly (not shown) of the
invention. As seen in FIG. 12C, QAD compression housing component
115 comprises a hollow cylindrical segment with a proximal end 117
and a circular bore 114 (shown in FIG. 11) tapered distal end 119
capable of slideably receiving the proximal end of the elongated
probe. The inner diameter at the proximal end of the QCD
compression housing component 115 is chosen so as to accommodate
the symmetrically tapered terminal end 110 of collet 105 that is
distal to the base component, and further comprises a thread
assembly 118 that enables compression housing component to engage
with complementary threading 132 on the distal end of QAD base
component 120. The proximal end of the elongated probe of the
invention is inserted through the circular bore 114 at proximal end
of compression housing component 115 and the inserted symmetrically
tapered end 110 of collet 105 in a manner so as to occupy the
entire length of cylindrical slot 108 in collet 105. The other
symmetric end 110 distal to the compression housing 115 is then
placed inside conical pocket 130 of base component 120, following
which threads 118 of the compression housing is engaged with the
complementary threads 132 in QAD base component 120 by applying a
torque so as to render the collet 105 to be non-removably retained
inside the coupled base-compression housing assembly, thereby
restraining the inserted elongated probe rigidly and non-removably
within the coupling assembly. Additionally, the mode of restraint
provided by the coupling assembly of the embodiment enables the
probe to maintain intimate contact with said assembly and in turn
the horn assembly (not shown) of the invention attached to the
coupling assembly by engaging thread 134 in QAD base component 120
with complementary threading in the horn assembly. Ultrasound
energy transmitted from the horn is therefore communicated to the
probe via the coupling assembly. The elongated probe is detached by
disassembling the coupling assembly, thereby allowing the probe to
be withdrawn from collet 105 and compression housing component
115.
[0074] The device of the invention upon being activated causes the
ultrasound generator component to transmit ultrasonic energy to the
horn component. The transmitted energy is amplified by the horn
component, which in turn, due to it's intimate and proximal contact
with the elongated probe, transmits the amplified energy to the
said probe. Transverse vibration modes on the elongated probe that
fall within the horn resonance are therefore, excited. The
"coupling" between the elongated probe and the horn is configured
so to as to present a relatively large impedance mismatch. The
coupling is located at a node of the horn. Longitudinal waves
impinging on the coupling will be either reflected back inside the
horn, or transmitted outward to the elongated probe proportionally
to the degree of the impedance mismatch at the coupling interface.
In a preferred embodiment, the coupling is arranged in a manner so
as to cause reflection of a substantial portion of ultrasound
energy back into the horn. Under these conditions, the horn
essentially functions as an energy storage device or reservoir,
thereby allowing for a substantial increase in drive amplitude.
[0075] The ultrasonic device of the present invention provides
several advantages for tissue ablation within narrow arteries over
convention devices. The transverse energy is transmitted extremely
efficiently, and therefore the required force to cause cavitation
is low. The transverse probe vibration provides sufficient
cavitation energy at a substantially low power (.about.1 watt).
Because transverse cavitation occurs over a significantly greater
portion (i.e., along the entire probe longitudinal axis) that comes
in contact with the tissue, the rates of endovascular materials
that can be removed are both significantly greater and faster than
conventional devices. The transverse vibrational mode of the
elongated probe of the invention and its attachable/detachable
coupling mode to the horn assembly allows for the bending of the
probe without causing probe heating as heat in the probe.
[0076] Another advantage offered by the device of the invention is
that the mechanism for probe attachment and detachment by means of
a lateral wall compression and decompression provided by the
coupling assembly. The probe can therefore, be rapidly attached to
and detached from the coupling assembly without necessitating its
"screwing" or "torquing" that are utilized conventional modes of
attachment of ultrasonic probes to the probe handle. This feature
facilitates ease of manipulation of the probe within narrow and
torturous venal cavities, and its positioning at the occlusion site
in a manner substantially similar to narrow lumen catheters prior
to and after device use.
* * * * *