U.S. patent application number 13/527145 was filed with the patent office on 2012-10-11 for controlling acoustic modes in tissue healing applications.
This patent application is currently assigned to SMITH & NEPHEW, INC.. Invention is credited to Robin A. Chivers, F. Javier de Ana, Neill M. Pounder.
Application Number | 20120259251 13/527145 |
Document ID | / |
Family ID | 38446036 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120259251 |
Kind Code |
A1 |
de Ana; F. Javier ; et
al. |
October 11, 2012 |
CONTROLLING ACOUSTIC MODES IN TISSUE HEALING APPLICATIONS
Abstract
A modal converter assembly for healing tissue, the modal
converter assembly comprises a transducer and a body. The
transducer is configured to transmit acoustic waves into the tissue
from a tissue surface. The body is configured to house the
transducer above the tissue surface such that the acoustic waves
transmitted into the tissue are transmitted at an oblique angle
relative to the tissue surface. The acoustic waves are transferred
as shear waves and longitudinal waves to treat a damaged portion of
the tissue.
Inventors: |
de Ana; F. Javier; (Chapel
Hill, NC) ; Chivers; Robin A.; (Dunnington, GB)
; Pounder; Neill M.; (Germantown, TN) |
Assignee: |
SMITH & NEPHEW, INC.
Memphis
TN
|
Family ID: |
38446036 |
Appl. No.: |
13/527145 |
Filed: |
June 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12296333 |
Apr 27, 2009 |
8226582 |
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PCT/US2007/066197 |
Apr 7, 2007 |
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13527145 |
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60790502 |
Apr 7, 2006 |
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60870934 |
Dec 20, 2006 |
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Current U.S.
Class: |
601/2 |
Current CPC
Class: |
A61N 7/00 20130101; A61B
8/4281 20130101 |
Class at
Publication: |
601/2 |
International
Class: |
A61N 7/00 20060101
A61N007/00 |
Claims
1. A device for healing tissue, the device comprising: a transducer
configured to transmit acoustic waves into the tissue from a tissue
surface; and a body configured to house the transducer above the
tissue surface, wherein the acoustic waves are transmitted into the
tissue as shear waves and longitudinal waves to treat a damaged
portion of the tissue, the acoustic waves being temporally shifted
such that a sum of the acoustic waves transmitted into the tissue
are transmitted at an oblique angle relative to the tissue
surface.
2. The device of claim 1, wherein the transducer includes a
piezoelectric element.
3. The device of claim 1, further comprising a spring configured to
bias the transducer toward the tissue surface.
4. The device of claim 3, further comprising a cap configured to
attach to the body, the spring having a first end and a second end,
the first end being attached to the cap and the second end being
attached to the transducer.
5. The device of claim 1, wherein the transducer comprises a
plurality of acoustic wave generating elements oriented along the
tissue surface.
6. The device of claim 5, wherein the device is configured for
controlling a time delay between sequential operations of the
plurality of acoustic wave generating elements such that an amount
of the shear waves and the longitudinal waves delivered into the
tissue are controlled.
7. The device of claim 1, further comprising a signal generator
that is configured to control the acoustic waves transmitted by the
transducer.
8. The device of claim 1, wherein the oblique angle is in a range
from about 18 to 71 degrees from normal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/296,333, filed Apr. 27, 2009, now allowed, which is a
national stage application under 35 U.S.C. 371 of PCT/US2007/66197,
filed Apr. 7, 2007, which claims priority from U.S. Provisional
Patent Application 60/790,502 filed Apr. 7, 2006, titled
"Controlling Acoustic Modes in Tissue Healing Applications" and
U.S. Provisional Patent Application 60/870,934 filed Dec. 20, 2006,
titled "Angle Dependence of Low Intensity Pulsed Ultrasound
Transmission in Bone." The applications are herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to therapeutic ultrasound
devices for treating a human body and, more particularly, to
controlling the angles at which the acoustic waves are delivered
from a transducer to the human body.
[0004] 2. Related Art
[0005] Ultrasound has been used as a therapeutic technique in
physical medicine for over 45 years. It has been a recommended
treatment technique for adjunctive therapy for the treatment of
pain, soft tissue injury, and joint dysfunction including
osteoarthritis, periarthritis, bursitis, tenosynovitis, and a
variety of musculoskeletal syndromes. Additionally, ultrasound has
been used in applications such as acceleration of wound healing,
phonophoresis of topical drugs, treatment of scar tissue, and
treatment of sports injuries.
[0006] The therapeutic biological effects of ultrasound may be
characterized into two major areas: thermal and nonthermal. The
nonthermal effects can include acoustic streaming, cavitation, and
other mechanical effects over the broad range of ultrasonic
frequencies from about 0.05 MHz (megahertz) to about 5.0 MHz. The
electrical output from a signal generator is converted into
mechanical vibration through a transducer which is generally made
of a piezoelectric material such as lead zirconate titanate (PZT),
single-crystal ferroelectric relax ors such as PMN-PZ-PT, or the
like. The mechanical vibration produces an acoustic wave which
travels through the tissue and is absorbed in the propagating
process. The rate of viscous absorption and the associated increase
in temperature are dependent on the micro-structural properties of
the tissue-type encountered, the frequency of the acoustic wave,
the spatial-temporal acoustic intensity and the degree of nonlinear
propagation in tissue. The acoustic energy may be in the form of a
continuous wave or a pulsed wave, depending on the therapeutic
application, and is typically transferred from the transducer to
the patient's tissue using an acoustic coupling material, such as
an ultrasonic gel, lotion, hydrogel, or water. Acoustic intensities
of 0.03 to 3.0 W/cm.sup.2 (Watts per square centimeter) are
typically applied for therapeutic purposes, in pulsed or continuous
modes, allowing treatment of bone fractures and acute, as well as
chronic, tissue injury.
[0007] Typically, therapeutic ultrasound treatment is administered
by utilizing a piezoelectric transducer normal to the skin tissue
interface to generate acoustic longitudinal waves that propagate in
tissue, primarily as longitudinal waves, to the treatment area. If
the incident longitudinal waves are not normal to the piezoelectric
transducer/skin tissue interface, the resulting refracted acoustic
waves in the subsequent soft tissue propagate as quasi-longitudinal
waves and quasi-shear waves at various refraction angles. As a
result, it is often difficult to administer the acoustic waves to
patients in the desired alignment with the targeted tissue area
using the means for therapeutic ultrasound devices that are
currently available.
[0008] International Publication No. WO 03/013654A1 taught that
shear and longitudinal waves could be controlled and delivered to a
tissue by means of a modal converter in the form of a trapezoidal
shaped cross-section of a low viscous loss material. The modal
converter is a large block of rubber that needs ultrasound coupling
gel between the tissue surface area and the rubber block. The shape
and design of such a block is difficult to position and restrain on
a patient to allow consistent delivery of ultrasound. In addition,
the placement of the transducer and the rubber block in relation to
the injury requires the center of the block to be offset from the
fracture, which is counter-intuitive for most people applying the
device to a fracture. The acoustic requirements for this rubber
block are such that the material is highly attenuating and requires
a much higher incident intensity to be delivered to the first face
of the block and has a substantial drain on the battery life of the
device and thus on its usability.
[0009] Although International Publication No. WO 03/013654A1
explains how to maximize longitudinal and shear waves along the
surface of the bone to accelerate periosteal healing, it does not
consider the importance of shear waves for the other processes
involved in tissue repair. Periosteal direct bone formation is one
of the key processes involved in fracture repair, but bone and
tissue healing is not limited to only that process. If it is
important to provide longitudinal and shear waves to aid specific
types of tissue healing, then it would also be important to
identify critical angles that result in the desired type of tissue
healing.
[0010] There remains a need in the art for improved methods and
systems for delivering ultrasonic waves to damaged tissue. Further,
there remains a need in the art for methods and systems that use
ultrasonic waves applied at critical angles to achieve specific
types of tissue healing.
SUMMARY OF THE INVENTION
[0011] An aspect of the invention provides a modal converter
assembly for healing tissue. The modal converter assembly comprises
a transducer and a body. The transducer is configured to transmit
acoustic waves into the tissue from a tissue surface. The body is
configured to house the transducer above the tissue surface such
that the acoustic waves transmitted into the tissue are transmitted
at an oblique angle relative to the tissue surface. The acoustic
waves are transferred as shear waves and longitudinal waves to
treat a damaged portion of the tissue.
[0012] An embodiment of the invention provides a modal converter
assembly wherein the transducer is a piezoelectric element.
[0013] Another embodiment of the invention further comprises a
modal converter being made of a material having a speed of sound
similar to the speed of sound of the soft tissue. The modal
converter is placed within the body and between the transducer and
the soft tissue such that the angle between the transducer and the
tissue surface is an oblique angle.
[0014] Another embodiment of the invention further comprises a
spring configured to bias the transducer toward the tissue
surface.
[0015] Yet another embodiment of the invention further comprises a
cap configured to attach to the body. The spring has a first end
and a second end. The first end is attached to the cap and the
second end is attached to the transducer.
[0016] Another embodiment of the invention provides a modal
converter assembly wherein the transducer comprises a plurality of
acoustic wave generating elements. The plurality of acoustic wave
generating elements are oriented along the tissue surface.
[0017] Another embodiment of the invention further comprises a
signal generator. The signal generator is configured to control the
acoustic waves generated in the transducer.
[0018] Another embodiment of the invention provides a modal
converter assembly wherein acoustic waves are temporally shifted
such that the sum of the acoustic waves transmitted into the tissue
are transmitted at an oblique angle relative to the tissue
surface.
[0019] Another embodiment of the invention provides a modal
converter assembly wherein the oblique angle is in the range from
about 18 to 71 degrees from normal.
[0020] Another aspect of the invention provides a modal converter
assembly for healing tissue. The modal converter assembly comprises
a transducer, a body, and a modal converter. The transducer is
configured to transmit acoustic waves into the tissue from a tissue
surface. The body is configured to house the transducer above the
tissue surface. The modal converter is made of a material having a
speed of sound similar to the speed of sound of the soft tissue.
The modal converter is placed within the body and between the
transducer and the soft tissue such that the angle between the
transducer and the tissue surface is an oblique angle. The acoustic
waves are transferred as shear waves and longitudinal waves to
treat a damaged portion of the tissue.
[0021] Another aspect of the invention provides a modal converter
assembly for healing tissue. The modal converter assembly comprises
a transducer and a body. The transducer includes a plurality of
acoustic wave generating elements configured to transmit acoustic
waves into the tissue from a tissue surface. The plurality of
acoustic wave generating elements are oriented along the tissue
surface. The body is configured to house the transducer above the
tissue surface such that the acoustic waves transmitted into the
tissue are transmitted at an oblique angle relative to the tissue
surface. The acoustic waves are transferred as shear waves and
longitudinal waves to treat a damaged portion of the tissue.
[0022] Yet another aspect of the invention provides a modal
converter assembly for healing tissue. The modal converter assembly
comprises a transducer and a body. The transducer is configured to
transmit acoustic waves into the tissue from a tissue surface. The
body is configured to house the transducer above the tissue surface
such that the acoustic waves transmitted into the tissue are
transmitted at an oblique angle relative to the tissue surface. The
acoustic waves are temporally shifted such that the sum of the
acoustic waves transmitted into the tissue are transmitted at an
oblique angle relative to the tissue surface. The acoustic waves
are transferred as shear waves and longitudinal waves to treat a
damaged portion of the tissue.
[0023] Yet another aspect of the invention provides a method for
treating tissue. The method orients a transducer over a tissue
surface. The method rotates the transducer relative to the tissue
surface. The method also transmits an acoustic wave into the
tissue. The acoustic waves are transmitted at an oblique angle
relative to the tissue surface. The acoustic waves are transferred
as shear waves and longitudinal waves to treat a damaged portion of
the tissue.
[0024] An advantage of the invention provides healing of tissue by
implementing acoustical waves at an oblique angle to the tissue
surface. At oblique angles, shear waves or a combination of shear
waves and longitudinal waves may treat a damaged portion of the
tissue.
[0025] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0027] FIG. 1 is a cross-sectional side view of a first embodiment
of a modal converter assembly;
[0028] FIG. 2 is a top view of a body of the modal converter
assembly;
[0029] FIG. 3 is a side view of the body shown in FIG. 2;
[0030] FIG. 4 is a perspective view of the body shown in FIG.
2;
[0031] FIG. 5 is a cross-sectional side view of the body shown in
FIG. 2;
[0032] FIG. 6 is a graph illustrating longitudinal and shear
waves;
[0033] FIG. 7 is a graph comparing longitudinal and shear
waves;
[0034] FIG. 8 is a second embodiment of the modal converter
assembly;
[0035] FIG. 9 is a third embodiment of the modal converter
assembly;
[0036] FIG. 10 is a fourth embodiment of the modal converter
assembly; and
[0037] FIG. 11 is a fifth embodiment of the modal converter
assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0039] FIGS. 1-5 illustrate a modal converter assembly 10 to
deliver ultrasound waves into a medium B which may be composed of
soft tissue and/or bone. The ultrasound waves promote healing of a
wound in the soft issue and/or healing of a fracture in the bone.
The modal converter assembly 10 includes a cap 2, a spring 4, a
transducer 5, a base 7, a body 8, and a modal converter 9. The cap
2, base 7, and body 8 form a housing structure to house the
transducer 5, spring 4, and modal converter 9. The transducer 5 is
electrically coupled to a signal generator 19 and controller 18 to
control wave propagation through the modal converter 9 and the
medium B.
[0040] In the depicted embodiments, the base 7 is shown assuming
that the interface with the medium B is flat. However, those
skilled in the art would understand that the base 7 can be shaped
to fit the interface with medium B at a position above medium B
where the generation of shear waves is controlled. For example, the
base 7 may be curved to fit over an arm or a leg of a patient, or
may be irregularly shaped to fit over irregular surfaces.
[0041] In some embodiments, the base 7 includes an aperture 3, such
as a hole or slot. The aperture 3 may be used to store the modal
converter assembly 10 or to attach the base 7 to the medium B. In
addition, the aperture may be used as a locator for positioning the
modal converter assembly 10 over the medium B. The base 7, in the
embodiments of FIGS. 1-5, has dimensions F, G, and K. Dimension F
is about 102 millimeters, dimension G is about 38 millimeters, and
dimension K is about 1.5 millimeters. Such an embodiment may be
easily wielded and manageable over the majority of body surfaces,
other dimensions may be used for body surfaces that may require
smaller or larger dimensions of the modal converter assembly 10.
The body 8 is shaped to receive the transducer 5.
[0042] The transducer 5 is constructed of materials and designs
that are commonly used in ultrasound applications. The transducer 5
may have piezoelectric properties and may be made from, as
examples, a ceramic material, a single-crystal relaxor
ferroelectric, lead zirconate titanate, lead metaniobate, barium
titanate, and piezoelectric co-polymers of polyvinylidene fluoride
(PVDF). Alternatively, the transducer 5 may have magnetostrictive
properties. The transducer 5 generates an ultrasound wave to be
transmitted into the medium B via the modal converter 9. The
ultrasound waves are generated from a driving signal received in
the transducer 5 through the signal generator 19. The spring 4
biases the transducer 5 against the modal converter 9 so that the
ultrasound waves travel from the transducer 5 through the modal
converter 9 and into the medium B.
[0043] In the embodiment depicted in FIGS. 1-5, the body 8 is a
cylindrical, hollow tube, as the transducer 5 has a circular
cross-section, but other shapes may be used. The body 8 has an
inner portion 14 and an outer portion 15. In the embodiments
depicted in FIGS. 1-5, the body 8 has an inner wall 12 and an outer
wall 13 which define the inner portion 14 and the outer portion 15,
respectively. The inner wall 12 of the body 8 is dimensioned such
that the transducer 5 fits tightly within the body 8. The inner
wall 12 may have a diameter the same as or slightly larger than the
diameter of the transducer 5. For example, the diameter of the
inner wall 12 may be about 0 to about 2 mm larger than the diameter
of the transducer 5. The body 8 also has a proximal end 16 and a
distal end 17. The cap 2 is connected to the body 8 at the distal
end 17. For example, the body 8 may have a lip 11 such that the cap
2 snaps onto the body 8. Further, the spring 4 is mounted between
the cap 2 and the transducer 5 in order to exert pressure and
positively bias the transducer 5. In some embodiments, the spring 4
may be mounted to the cap 2. The spring 4 biases the transducer 5
toward the proximal end 16 of the body 8. The body 8 is mounted at
an oblique angle A relative to the base 7. The body 8 has
dimensions H and J. In the embodiment depicted in FIGS. 1-5,
dimension H is about 33 millimeters and dimension J is about 31
millimeters but other dimensions may be used.
[0044] The modal converter 9 may be composed of suitable low
attenuation materials which include, but are not limited to,
thermoplastics, thermosets, elastomers and mixtures thereof. Useful
thermoplastics include, but are not limited to, ethyl vinyl
acetate, available from USI Corp (c/o Plastic Systems, Marlboro,
Mass.), ecothane CPC 41, available from Emerson and Cumming (Deway
and Almay Chemical division, Canton, Mass.), and polyurethane RP
6400, available from Ren Plastics (a Division of Ciba Geigy,
Fountain Valley, Calif.). Useful thermosets include, but are not
limited to, epoxies such as Spurr epoxy, available from Ernest F.
Fullam, Inc. (Schenectady, N.Y.) and Stycast, available from
Emerson and Cumming. Other thermosets may include polymerized
esters of acrylic acid, such as n-octyl ester of acrylic acid,
n-nonyl ester of acrylic acid, or 2-ethyl pentyl acrylate. Useful
elastomers include, but are not limited to, RTV 60 and RTV 90,
which are available from General Electric (Silicon Products
Division, Waterford, N.Y.). Other elastomers may include natural
rubber, synthetic rubber, such as oil-filled and peroxide-cured
cis-butadiene rubber, or gel pad material, such as polyglycerol
hydrogel.
[0045] The modal converter 9 is fitted between the transducer 5 and
the medium B. The modal converter 9 may have a low ultrasound
attenuation and speed of sound similar to that of soft tissue. The
bottom surface of the modal converter 9 that is in contact with the
medium B is at an oblique angle relative to the body 8. The
dimension E of the modal converter 9 is such that the spring 4
exerts at least some pressure on the transducer 5. Two thin layers
of coupling material, such as hydrogel, mineral oil, or water, are
applied to ensure that the maximum ultrasound power gets
transmitted into the tissue from the transducer 5. A first layer 1
is applied between the transducer 5 and the modal converter 9. A
second layer 6 is applied between the modal converter 9 and the
medium B.
[0046] The modal converter 9 is acoustically coupled to the
transducer 5 with the first layer 1 having an acoustic impedance
comparable to the acoustic impedance of the modal converter 9,
preferably an acoustic impedance within plus or minus ten percent
of the acoustic impedance of the modal converter 9. In some
embodiments, the acoustic impedance of the modal converter 9 is
almost equal to that of human soft tissue. Additionally, the modal
converter 9 is composed of materials preferably having a
longitudinal velocity that is less than the longitudinal velocity
for human musculo- skeletal soft tissue and that is less than the
longitudinal velocity for bone tissue.
[0047] The acoustic waves which emanate from the transducer 5 are
controlled spatially and temporally by the system controller 18.
The design and fabrication of the system controller 18 are well
known to those who practice the art. The system controller 18 is
electrically connected to the signal generator 19, and the signal
generator 19 is electrically connected to the transducer 5. The
system controller 18 triggers the programmable signal generator 19
to produce ultrasonic excitation signals that are sent to the
transducer 5. The transducer 5 receives the excitation signal and
emits an acoustic longitudinal wave that propagates through the
modal converter material 9 and on to medium B.
[0048] The transducer 5 produces specific sequential or
simultaneous transmissions of acoustic waves, controlled by the
system controller 18, in order to noninvasively irradiate or
interrogate the medium B ultrasonically. The system controller 18
may be a programmable microprocessor, but may also include, though
is not limited to, integrated circuits, analog devices,
programmable logic devices, personal computers or servers. The
timing sequences may be established by the user at any time or
established during the manufacturing process.
[0049] The modal converter assembly 10 may be used to administer
therapeutic treatment composed of an ultrasound dosage administered
once or twice a day, and repeated daily for several months to
effectively stimulate the healing process. In some embodiments, one
dosage of acoustic waves ranges between 1 and 60 minutes in length
for the transducer 5. The modal converter assembly 10 may be used
to facilitate and enhance application of therapeutic ultrasound
dosages to shallow or deep anatomical structures, or both, in an
effort to expedite tissue wound healing, including both the
endosteal and periosteal healing phases in the bone fracture
healing process.
[0050] FIG. 6 graphically illustrates incident waves IW onto an
interface between soft tissue and bone and the resulting reflected
waves RW, refracted shear waves W, and refracted longitudinal waves
V. Ultrasonic waves emanate from the transducer 5 (not shown in
FIG. 6), travel through the modal converter 9, which is at an angle
.THETA. with respect to the normal, and enter into a first medium,
such as soft tissue, as the incident wave IW at an angle .theta..
The incident wave IW continues through the first medium until it
reaches a second medium, such as bone. At that point, a portion of
the incident wave IW is reflected off the second medium as the
reflected wave RW at an angle .PHI., a portion is refracted as the
refracted shear wave W at an angle .gamma., and a portion is
refracted as the longitudinal wave V at an angle .beta.. As it is
believed that refracted shear waves W and refracted longitudinal
waves V promote different types of healing, it is important to
identify critical angles of .gamma. and .beta. that maximize the
respective type of wave. By identifying the critical angles and
comparing the critical angles to the corresponding angle .theta. of
the incident wave IW, the modal converter 9 can be constructed and
arranged to provide predetermined specific types of healing or
combinations thereof.
[0051] FIG. 7 graphically illustrates an exemplary method of
determining the modal converter angle .THETA. for a desired amount
of shear waves W (best seen in FIG. 6) and/or longitudinal waves V
(best seen in FIG. 6). Four plots are included in the graph showing
the angle at which the refracted waves travel in medium 2 (bone)
assuming four different combinations of material properties for
soft tissue, bone and the modal converter. For example, if only
shear waves W parallel to the interface were desired, the modal
converter angle .THETA. would be selected to be about 60 degrees.
However, if only shear waves W into the medium were desired, the
modal converter angle .THETA. would be selected to be about 55
degrees. If a combination of shear waves W and longitudinal waves V
into the medium are desired, the angle .THETA. of the modal
converter 9 would be selected to be about 35 degrees. However, FIG.
7 is only exemplary as the relevant angles depend largely upon the
material of the modal converter, the material of the second medium,
and may further depend upon the geometry of the interface between
each material. Assuming sound waves travel through the modal
converter material at a speed of about 1390 msec, longitudinal
sound waves travel through the second medium at a speed in the
range of about 3000 msec to about 3800 msec, and shear sound waves
travel through the second medium at a speed in the range of about
1630 msec to about 1890 msec, the actual critical angles have been
determined to be from about 22 to about 28 degrees to maximize
longitudinal waves V traveling parallel to the interface between
the first and second media, from about 48 to about 59 degrees to
maximize shear waves W traveling parallel to the interface, and
from about 36 to about 41 degrees to maximize the combination of
longitudinal waves V traveling parallel to the interface and shear
waves W traveling into the second medium. In general, the range of
the modal converter angle to achieve longitudinal waves is from
about 9 degrees to about 71 degrees, whereas the range of the modal
converter angle to achieve shear waves is from about 18 degrees to
about 76 degrees.
[0052] FIG. 8 illustrates a second embodiment of the modal
converter assembly, generally indicated by reference numeral 100.
The modal converter assembly 100 includes a transducer 110, a modal
converter 112, and a body 114. The transducer 110 and the modal
converter 112 are mounted to the body 114. The modal converter 112
provides a grating on the surface of the transducer 110 to direct
the ultrasonic waves in a predetermined direction. Selection of the
grating pattern and the grating spacing of the modal converter 112
enables the longitudinal waves emitted from the transducer 110 to
undergo an angular shift.
[0053] FIG. 9 illustrates a third embodiment of the modal converter
assembly, generally indicated by reference numeral 200. The modal
converter assembly 200 includes a piezoelectric element 210, a
modal converter 212, and a body 214. The piezoelectric element 210
and the modal converter 212 are mounted within the body 214. The
piezoelectric element 210 is mounted at an angle relative the
bottom surface of the body 210. The modal converter 212 redirects
the waves produced by the piezoelectric element 210.
[0054] FIG. 10 illustrates a fourth embodiment of the modal
converter assembly, generally indicated by reference numeral 300.
The modal converter assembly 300 includes a piezoelectric element
310 and a modal converter 312. In this embodiment, the modal
converter 312 also functions as a housing or body for the
piezoelectric element 310. The piezoelectric element 310 is mounted
at an angle relative the bottom surface of the modal converter 312.
The modal converter 312 redirects the waves produced by the
piezoelectric element 310.
[0055] FIG. 11 illustrates a fifth embodiment of the modal
converter assembly, generally indicated by reference numeral 400.
The modal converter assembly 400 includes a plurality of
transducers 410, 412, 414, 416. The transducers 410, 412, 414, 416
produce corresponding waves 420, 422, 424, 426. A system
controller, similar to the system controller shown in FIG. 1, can
be used to control the engagement of each respective transducer
410, 412, 414, 416. Thus, as an example, the system controller can
sequentially engage each transducer 410, 412, 414, 416 to provide
gross angular shear or longitudinal waves. By controlling the time
delay between sequential operations of the transducers 410, 412,
414, 416, the modal converter assembly 400 can provide waves at a
predetermined angle. Thus, the modal converter assembly 400 can
control the amount of delivered shear and/or longitudinal
waves.
[0056] As shown in the embodiments, the piezoelectric may deliver
shear waves as a therapy by changing the angle of the piezoelectric
transducer relative to the medium either physically or temporally.
Materials such as a modal converter may be shaped to adjust the
angle of the piezoelectric relative to the medium. Additionally,
multiple piezoelectric elements may be used sequentially to achieve
a similar effect.
[0057] As various modifications could be made to the exemplary
embodiments, as described above with reference to the corresponding
illustrations, without departing from the scope of the invention,
it is intended that all matter contained in the foregoing
description and shown in the accompanying drawings shall be
interpreted as illustrative rather than limiting. Thus, the breadth
and scope of the present invention should not be limited by any of
the above-described exemplary embodiments, but should be defined
only in accordance with the following claims appended hereto and
their equivalents.
* * * * *