U.S. patent application number 10/228528 was filed with the patent office on 2003-01-02 for intrabody hifu applicator.
This patent application is currently assigned to Transurgical, Inc.. Invention is credited to Acker, David E., Harhen, Edward Paul, Pant, Bharat B..
Application Number | 20030004439 10/228528 |
Document ID | / |
Family ID | 22378545 |
Filed Date | 2003-01-02 |
United States Patent
Application |
20030004439 |
Kind Code |
A1 |
Pant, Bharat B. ; et
al. |
January 2, 2003 |
Intrabody HIFU applicator
Abstract
An apparatus and method for applying sonic energy within the
body of the living subject. A probe for applying sonic energy
within the body of a subject comprises a probe body having a
proximal and a distal end adapted for insertion into the body of a
subject, a spatially-distributed sonic transducer disposed adjacent
to the distal end of the probe body and a device for moving one
portion of the spatially-distributed transducer relative to another
portion of the transducer while the distal end of the probe is
disposed within the body of the subject.
Inventors: |
Pant, Bharat B.;
(Minneapolis, MN) ; Acker, David E.; (Setauket,
NY) ; Harhen, Edward Paul; (Duxbury, MA) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,
KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
Transurgical, Inc.
220 Belle Meade Road Suite 2
Setauket
NY
11733
|
Family ID: |
22378545 |
Appl. No.: |
10/228528 |
Filed: |
August 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10228528 |
Aug 27, 2002 |
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09496988 |
Feb 2, 2000 |
|
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6461314 |
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60118432 |
Feb 2, 1999 |
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Current U.S.
Class: |
601/2 |
Current CPC
Class: |
A61B 17/2202 20130101;
A61B 8/12 20130101; A61N 7/02 20130101; A61B 8/445 20130101; A61B
8/4281 20130101; A61B 2017/00274 20130101; A61B 2018/00547
20130101 |
Class at
Publication: |
601/2 |
International
Class: |
A61H 001/00 |
Claims
1. A probe for applying sonic energy within the body of a subject
comprising: (a) an elongated probe body having a proximal end and a
distal end adapted for insertion into the body of the subject, said
probe body having a direction of elongation; (b) a
spatially-distributed sonic transducer disposed adjacent said
distal end of said probe body, said distributed transducer being
movable between a collapsed condition and an expanded condition in
which said distributed extends outwardly from said probe body in
one or more directions transverse to the direction of elongation of
said probe body; and (c) means for controlling movement of said
distributed transducer between said collapsed condition and said
expanded condition.
2. A probe as claimed in claim 1 wherein said distributed
transducer is arranged to send sonic waves so that said sonic waves
converge in a focal region when said distributed transducer is in
said expanded condition.
3. A probe as claimed in claim 2 wherein said means for controlling
movement includes means for moving one portion of said distributed
transducer relative to another portion of said distributed
transducer while said distributed transducer is in said expanded
condition so as to vary the location of said focal region relative
to said distal end of said probe.
4. A distributed transducer comprising: (a) a deformable element;
(b) one or more piezoelectric layers mounted to said deformable
element or formed integrally with said deformable element; (c) a
plurality of electrode pairs, the electrodes of each said pair
being disposed on opposite sides of said one or more piezoelectric
layers, said electrode pairs being disposed at spaced-apart
locations; and (d) means for deforming said deformable element so
as to control curvature of said one or more piezoelectric
layers.
5. A transducer as claimed in claim 4 wherein said deformable
element includes a beam having a lengthwise extent and wherein
electrode pairs are disposed at spaced-apart locations along the
length of said beam, said means for deforming including means for
bending said beam transverse to said lengthwise extent.
6. A transducer as claimed in claim 4 wherein said one or more
piezoelectric layers includes a continuous piezoelectric sheet
extending over at least a part of said deformable element, the
transducer including impedance-sensing electrodes in contact with
said sheet at spaced-apart locations thereon, said sheet varying in
impedance dependent upon strain in said sheet.
7. A transducer as claimed in claim 6 wherein said electrode pairs
include said impedance-sensing electrodes.
8. A method of applying ultrasonic energy within the body of a
living subject comprising the steps of: (a) introducing a
distributed ultrasonic transducer into the body of the subject; (b)
changing the configuration of the distributed transducer while the
transducer is disposed in the body of the subject; and (c)
actuating the transducer to apply ultrasonic energy within a focal
region.
9. A method as claimed in claim 8 wherein said step of changing the
configuration is performed so as to move the focal region of the
transducer within the body of the subject.
10. A method as claimed in claim 9 wherein said step of actuating
the transducer includes actuating the transducer before said step
of changing the geometry, while the transducer has a first
configuration and actuating the transducer after said step of
changing the configuration, when said transducer has a second
configuration different from said first configuration.
11. A method as claimed in claim 10 wherein said step of changing
the configuration includes the step of deforming the
transducer.
12. A method as claimed in claim 11 wherein said transducer
includes a piezoelectric sheet, the method further comprising the
step of monitoring the configuration of the transducer by
monitoring electrical impedance within said piezoelectric
sheet.
13. A probe for applying ultrasonic energy in the body of a subject
comprising a probe body having a hollow distal end with an axis of
elongation in a lengthwise direction, a thickness dimension in a
thickness direction transverse to said axis of elongation and a
width dimension in a widthwise direction transverse to said axis of
elongation and said thickness direction, said width dimension being
greater than said thickness dimension, and a distributed ultrasonic
transducer disposed in said body and extending in said width
direction and extending in said widthwise and lengthwise
directions.
14. A probe for applying ultrasonic energy in the body of a subject
comprising a probe body having a hollow body portion, a deformable,
spatially distributed transducer disposed in said hollow body
portion, one or more slide elements, each such slide element being
mounted in said hollow body portion for movement between an engaged
position in which the slide element is disposed between the wall of
the body and the transducer and a disengaged position in which the
slide element is out of engagement with the transducer, said
transducer changing shape upon movement of said slide elements
between engaged and disengaged positions, the probe further
comprising slide element movement devices for selectively moving
each slide element between its engaged and disengaged positions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 09/496,988, filed Feb. 2, 2000, which claims the benefit
of U.S. Provisional Patent Application Serial No. 60/118,432 filed
on Feb. 2, 1999, the disclosures of which are incorporated by
reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to application of sonic
energy, such as focused ultra sound energy within the body of a
living subject such a human or other mammalian subject.
[0003] Various forms of therapy can be applied within the body of a
human or other mammalian subject by applying energy from outside of
the subject. In hyperthermia, ultrasonic or radio frequency energy
is applied from outside of the subject's body to heat the tissues.
The applied energy can be focused to a small spot within the body
so as to heat the tissues at such spot to a temperature sufficient
to create a desired therapeutic effect. This technique can be used
to selectively destroy unwanted tissue within the body. For
example, tumors or other unwanted tissues can be destroyed by
applying heat to heat the tissue to a temperature sufficient to
kill the tissue, commonly to about 60.degree. to 80.degree. C.,
without destroying adjacent normal tissues. Such a process is
commonly referred to as "thermal ablation". Other hyperthermia
treatments include selectively heating tissues so as to selectively
activate a drug or promote some other physiologic change in a
selected portion of the subject's body. Other therapies use the
applied energy to destroy foreign objects or deposits within the
body as, for example, in ultrasonic lithotripsy.
[0004] In most cases, the focused ultrasound energy used in said
procedures is applied by an ultrasonic energy source disposed
outside of the body. For example, certain embodiments taught in
co-pending, commonly assigned U.S. patent application Ser. No.
09/083,414 filed May 22, 1998 and in the corresponding
International Application PCT/US98/10623, also filed May 22, 1998,
the disclosures of which are hereby incorporated by reference
herein, describe systems for applying focused ultrasound energy in
conjunction with a magnetic resonance device. An external
ultrasonic energy applicator is also taught for example, in FIG. 1
of Aida et al., U.S. Pat. No. 5,590,653 and in FIG. 1 of Oppelt et
al., U.S. Pat. No. 5,624,382. These external ultrasonic energy
sources transmit ultrasonic energy to the desired treatment
location through the tissues of the body. Various proposals have
been advanced for inserting ultrasonic energy sources into the body
and focusing energy from such intrabody sources on the desired
treatment regions. For example, FIG. 5 of the aforementioned Oppelt
et al. '382 patent illustrates a therapeutic ultrasound transducer
which may be inserted into the rectum so as to direct ultrasonic
energy onto the prostate gland through the wall of the rectum. Aida
et al. '653 discloses various forms of intrabody transducer arrays
(FIGS. 9-12). Diederich, Transuretheral Ultrasound Array For
Prostate Thermal Therapy: Initial Studies, IEEE Transactions On
Ultrasonics, Ferroelectrics and Frequency Control, Vol. 43, No. 6,
pp. 1011-1022 (November 1996) discloses a rod-like ultrasound
transducer housed within a catheter. Such a rod-like transducer
does not focus the ultrasound but instead provides a sound pressure
distribution which is at a maximum adjacent the transducer and
which diminishes with distance. In use, the transducer is inserted
into the urethra and the catheter is cooled by a flow of water. The
cooling water limits the temperature rise of the urethra wall.
Prostate tissue remote from the urethra is heated by the applied
energy.
[0005] Despite these and other attempts to utilize intrabody
ultrasonic transducers, still further improvement would be
desirable.
SUMMARY OF THE INVENTION
[0006] One aspect of the present invention provides a probe for
applying sonic energy within the body of the subject. The probe
according to this aspect of the invention includes a probe body
having a proximal and having a distal end adapted for insertion
into the body of the subject. The probe also includes a spatially
distributed ultrasonic transducer disposed adjacent the distal end
of the probe body. As used in this disclosure, the term "spatially
distributed sonic transducer" refers to a sonic transducer which is
capable of emitting sound from a plurality of locations spaced
apart from one another. One form of a spatially distributed
transducer includes a plurality of discrete transducer elements
mounted at spaced apart locations. Another form of spatially
distributed transducer includes a continuous sheet of transducer
material. In such a continuous-sheet transducer, various regions of
the sheet are spaced apart from one another and hence can emit
sound at spaced apart locations. The probe according to this aspect
of the invention further includes means for moving one portion of
the distributed transducer relative to another portion of the
distributed transducer while distal end of the probe and hence the
distributed transducer is disposed within the body of the subject.
Such movement changes the configuration of the distributed
transducer so as to focus the sound emitted from the distributed
transducer onto a focal spot at a selected location relative to the
probe.
[0007] The distributed transducer may include a deformable element,
which may be separate from the active elements of the transducer.
Alternatively, the deformable element may be integral with a
continuous transducer sheet. In the simplest embodiment, the entire
distributed transducer includes only a continuous sheet element,
such as an elongated strip formed from a piezoelectric material and
the electrodes used to actuate those portions of the material.
Alternatively, the distributed transducer may include plural
separate transducer elements mounted to the deformable element at
spaced-apart locations. The deformable element may incorporate an
elongated beam having a fixed end mounted to the probe body and a
fixed end. The means for controlling deformation may include a
control element moveable mounted to the probe body. The control
element desirably is a flexible cable having a distal end connected
to the free end of the beam and having a proximal end extending to
the proximal end of the probe body. Thus, the deformable element
may be bent to the desired degree of curvature by pulling the
flexible cable. Alternatively, the deformable element may include a
disc like element having a central region and a peripheral region
surrounding the central region. The means for controlling
deformation may include means from moving the peripheral and
central regions relative to one another.
[0008] In yet another alternative, the probe may include a
plurality of supports movably mounted to the probe body adjacent to
distal end thereof and the distributed transducer may include a
plurality of transducer elements mounted to the supports. The means
for moving one part of the transducer relative to the other may
include means for moving one or more of the supports relative to
the probe body. For example, the plurality of supports may include
a plurality of elongated supports arranged generally in the manner
of the radial ribs of an umbrella. Thus, the elongated supports may
have central ends pivotally connected to a common member and may
have peripheral ends remote from the central ends. The transducer
elements are mounted to the elongated supports adjacent the
peripheral ends thereof. The supports can be pivoted relative to
the common member between a collapsed condition in which the
peripheral ends are close to a central axis and an expanded
commission in which the peripheral ends are remote from the central
axis. The pivoting means may include a control member and a
plurality of struts. Each strut has a first end pivotally connected
to the control member and a second end connected to one of the
elongated supports remote from the central end of such support. The
means for pivoting the supports may include means for moving the
control member and common member relative to one another. For
example the probe body may include an elongated tubular element and
a flexible cable may be provided in the tubular element. The cable
may be attached to the control member and the distal end of the
tubular element may be connected to the common member or vice
versa.
[0009] In yet another arrangement, the distal end of the probe body
itself may be deformable and the distributed transducer may be
arranged along the distal end of the probe body so that deformation
of the probe body distal end will move one part of the transducer
relative to another part. For example, the probe body may be
elongated and the distributed transducer may include separate
transducers or portions of a continuous sheet spaced apart from one
another in the lengthwise direction along the probe body. The means
for deforming the distal end of the probe body may include means
for bending the distal end of the probe body transverse to its
lengthwise direction so as to vary the curvature of the distributed
transducer. The distal end of the probe body may be advanced into
an intrabody space and the probe body may be deformed while the
distal end is disposed in the intrabody space. For example, the
probe body may be advanced through the urethra into the urinary
bladder and the distal end of the probe body may be bent while the
distal end of the probe body is in the urinary bladder.
[0010] A further aspect of the present invention provides probe for
applying sonic energy within the body of the subject which includes
an elongated probe body having a distal end and a spatially
distributed sonic transducer disposed adjacent to the distal end of
the probe body. In a probe according to this aspect of the present
invention, the distributed transducer is moveable between a
collapsed condition in which the distributed transducer has
relatively small dimensions in directions transverse to the
direction of elongation of the probe body and an expanded condition
in which the distributed transducer has relatively large transverse
dimensions and hence extends outwardly from the probe body in one
or more directions transverse to the direction of elongation of the
probe body. A probe according to this aspect of the invention
desirably includes means for controlling movement of the
distributed transducer between the collapsed condition and the
expanded condition. In a probe according to this aspect of the
invention, the movement control means optionally may be adapted to
vary the configuration of the distributed transducer while the
transducer is in the expanded condition so as to vary the focus of
sound waves emitted by the transducer.
[0011] Still further aspects of the present invention provide
methods of ultrasonic treatment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagrammatic view depicting a probe in
accordance with one embodiment of the invention in conjunction with
other apparatus.
[0013] FIG. 2 is a fragmentary, diagrammatic sectional view
depicting a portion of the probe of FIG. 1.
[0014] FIG. 3 is a fragmentary electrical schematic of the probe of
FIGS. 1-2.
[0015] FIG. 4 is a fragmentary, perspective view depicting the
probe of FIGS. 1-3 in one condition.
[0016] FIG. 5 is a view similar to FIG. 4 but depicting the probe
in a different condition.
[0017] FIGS. 6, 7 and 8 are diagrammatic views of probe in
accordance with further embodiments of the invention.
[0018] FIG. 9 is a fragmentary, diagrammatic sectional view
depicting a probe in accordance with yet another embodiment of the
invention.
[0019] FIG. 10 is a fragmentary, perspective view depicting
portions of a probe in accordance with another embodiment of the
invention.
[0020] FIG. 11 is a view similar to FIG. 10 but depicting the a
probe of FIG. 10 in a different condition during operation.
[0021] FIG. 12 is a fragmentary diagrammatic elevational view
depicting portions of a probe in accordance with another embodiment
of the invention in one condition during operation.
[0022] FIG. 13 is a view similar to FIG. 10 but depicting the probe
of FIG. 12 in a different condition during operation.
[0023] FIG. 14 is a diagrammatic sectional view taken along line
14-14 in FIG. 12.
[0024] FIG. 15 is a fragmentary diagrammatic sectional view
depicting a probe in accordance with yet another embodiment of the
invention.
[0025] FIG. 16 is a fragmentary diagrammatic view depicting a probe
in accordance with yet another embodiment of the invention.
[0026] FIG. 17 is a fragmentary diagrammatic sectional view
depicting a probe in accordance with yet another embodiment of the
invention.
[0027] FIG. 18 is a sectional view along line 18-18 in FIG. 17.
DETAILED DESCRIPTION
[0028] A probe in accordance with one embodiment of the present
invention includes a probe body 20 having a proximal end 22 and a
distal end 24 adapted for insertion into the body of a subject.
Probe body 20 may be a conventional catheter, endoscope or other
conventional medical device. The particular probe body illustrated
is in the form of an elongated tube having an interior bore 26
extending between the proximal and distal ends. A deformable
distributed sonic transducer 30 is mounted to the distal end 24 of
the probe body. As best seen in FIG. 2, transducer 30 includes a
continuous sheet 32 of a piezoelectric polymeric material such as a
polyvinyledene fluoride piezoelectric material. Materials of this
type are described in U.S. Pat. Nos. 4,830,795, 4,268,653 and
4,577,132. Particularly preferred piezoelectric polymers are
available from Measurement Specialties, Inc. of Norristown, Pa. The
transducer further includes a backing layer 34 and electrodes 36
and 38 disposed on opposite sides of piezoelectric layer 32. Layer
34 may be formed, for example, from a flexible dielectric polymer,
a flexible metal strip, or the like. The electrodes are formed in
pairs. Each pair includes a first electrode 36 disposed on one side
of the piezoelectric layer 32 and a second electrode 38 disposed on
the opposite side of the piezoelectric layer, in alignment with the
first electrode. For example, electrodes 36a and 38a (FIGS. 2 and
3) form one such pair whereas electrodes 36b and 38b (FIG. 3) form
another such pair. The electrodes are connected to conductors 40
extending along layers 32 and 34. These conductors may be
fabricated, for example, by techniques such as those used in
formation of flexible printed circuits.
[0029] The thicknesses of the various elements are greatly
exaggerated for clarity of illustration in FIG. 2. In practice, the
entire transducer is formed as an integral, strip-like structure.
Thus, the electrodes may be provided as thin,
electrically-conductive coatings on opposite sides of layer 32.
[0030] Transducer 30 is generally in the shape of an elongated,
flexible beam having a fixed end 42 attached to the distal end 24
of probe body 20 and having a free end 44 remote from the fixed
end. The electrode pairs 36, 38 are arranged along the lengthwise
extent of the beam. Conductors 40 are connected to further
conductors 46, which a few are seen in FIG. 2. Conductors 46 extend
to the proximal end 22 of the probe body, and to an electrical
connector 48 (FIG. 1) at the proximal end of the probe body.
[0031] A control element in the form of a flexible cable 50 is
attached to the free end 44 of the beam or transducer 30. Cable 50
is slidably received within the bore 26 of the probe body and
extends to a proximal end element 52. End element 52 in turn is
connected through a linkage 54 to the proximal end 22 of the probe
body. Linkage 54 includes a mechanical device for controlling the
position of proximal end element 52 relative to the proximal end of
the probe body, and hence controlling the position of the control
element 50 relative to probe body 20. The particular linkage
illustrated includes a manually adjustable wheel 56, a threaded rod
58 and a nut 60 threadedly engaged on rod 58. Wheel 56 and screw 58
are rotatably mounted to one element of the linkage, whereas nut 60
is pivotally mounted to another element of the linkage, so that by
rotating knob 56 and screw 58, the linkage can be expanded or
collapsed, thereby driving proximal end element 52 forwardly and
rearwardly relative to the probe body. The particular linkage
depicted in FIG. 2 is merely exemplary. Any other conventional
positioning device capable of moving one element to a desired
position relative to the other can be employed. For example, cams,
levers, electromechanical actuators and hydraulic actuators may be
employed. Also, the linkage may be omitted, so that the proximal
end element 52 can be moved manually relative to the proximal end
of the probe body. The probe may also be provided with a separate
device (not shown) for selectively locking the control element or
cable 50 in position relative to the probe body.
[0032] Beam or transducer 30, in its free undeformed condition is
nearly flat, as indicated in broken lines at 30' in FIG. 1. By
moving control element or cable 50 in the retracting direction,
toward the proximal end 22 of the probe body, the free end 44 of
the beam can be brought closer to the fixed end 42, thereby
deforming the transducer or beam into configurations having a
greater curvature, including the fully bowed condition illustrated
in broken lines in FIG. 1 at 30" and also illustrated in FIG. 5. In
the fully elongated or collapsed condition 30', the beam lies close
to the axis 62 of the probe body distal end. In the fully bowed or
expanded condition 30", the probe projects laterally from axis
62.
[0033] As further discussed below, the transducer can be actuated
as a multi-element array to provide ultrasonic emissions focused on
a focal within a focal region 65 near the center of curvature 64 of
the beam. The focal spot can be moved within the focal region by
altering the phasing of the electrical signal supplied to the
array. However, bending the transducer moves the center of
curvature and moves the focal region. With the transducer in the
fully collapsed or flat condition, the focal spot will lie at a
large distance from axis 62. As the transducer becomes
progressively more bowed, the center of curvature 64 and hence the
focal region and focal spot move closer to axis 62. With the
transducer in the slightly bowed position illustrated in solid
lines in FIG. 1 and illustrated in FIG. 4, the center of curvature
64 is at the position indicated. With the transducer in a more
bowed position, as indicated in broken lines at 30" in FIG. 1 and
as shown in FIG. 5, the center of curvature is at position 64".
[0034] The probe is used in conjunction with monitoring and driving
elements (FIG. 1). A switch 70 is connected by a multiconductor
cable to a connector 72 matable with connector 48. An impedance
measuring device 74 is provided. The impedance measuring device can
be connected by switch 70 to a pair of electrodes 38a and 38g
disposed at opposite ends of transducer 30, so that the impedance
measuring device can measure the electrical impedance within
piezoelectric layer 32, from one end of the piezoelectric layer to
the other. Thus, electrodes 38a and 38g serve as impedance
measuring electrodes. The impedance monitoring device may include a
conventional bridge circuit, with the impedance between electrodes
38a and 38g on one leg of the bridge circuit. The impedance monitor
may also include temperature compensation elements (not shown)
mounted at the distal end of the probe and connected in the bridge
circuit so as to compensate for effects of temperature on the
impedance on layer 32. The impedance monitor may also include
conventional components such as operational amplifiers and
analog-to-digital converters for providing a digital readout of the
impedance between electrodes 38a and 38g. Desirably, the impedance
monitoring device is arranged to monitor AC impedance rather than
DC resistance.
[0035] The electrical impedance within piezoelectric layer 32
varies with mechanical strain on the layer. As the beam is bent
from undeformed, fully collapsed condition 30' toward the fully
expanded bowed condition 30", layer 32 is placed under
progressively increasing compression and the electrical impedance
within the layer. Thus, the electrical impedance between electrodes
38a and 38g through layer 32 varies with the degree of curvature in
the beam.
[0036] During operation of the impedance monitoring device,
electrodes 36 and 38 which are not connected to the resistance
monitoring device are inactive. Depending on the configuration and
placement of the electrodes, a significant portion of the impedance
along the piezoelectric layer may be shorted by conductivity along
the inactive electrodes. To avoid such shorting, and increase the
change in resistance between electrodes 38a and 38g, the
intermediate electrodes 38b, 38c . . . and 36b, 36c . . . may be
isolated from the piezoelectric layer by a very thin dielectric
layer (not shown) disposed between the electrodes and the surface
of the piezoelectric layer. Switch 70 is also arranged to
disconnect electrodes 38a and 38g from resistance monitor 74 and to
connect all of the electrodes 36 and 38 to a HIFU driver 76. HIFU
driver 76 includes conventional phased array driver components for
applying electrical potentials between the electrodes 36 and 38 of
each electrode pair. These electrical potentials vary at ultrasonic
frequencies. The varying potential is applied across the region of
piezoelectric film 32 between each pair of electrodes and causes
mechanical vibration of each such region.
[0037] HIFU driver 76 is controlled by a computer 78. The computer
controls the frequency and phase of the excitations applied to the
various electrode pairs in accordance with the known principles
governing operation of phased array ultrasonic emitters so that the
ultrasonic emissions from the various parts of the piezoelectric
layer reinforce one another at the desired focal spot. Computer 78
stores a value of the curvature of the transducer or beam 30 based
upon the resistance measurement from resistance monitor 74. This
value is incorporated into the parameters defining the geometry of
the emitter array, and such parameters are used in the normal
manner to calculate the appropriate signals to be applied to each
element of the array. As such calculations are well within the
skill of the art and employ known methods, they are not described
in detail herein.
[0038] Computer 78 is linked to conventional display and
input/output devices 80 such as a CRT or other pictorial display
and a mouse, joystick or other control elements. An imaging system
82 such as a magnetic resonance imaging, x-ray or CAT scan imaging
system 82 is also connected to the computer. The imaging system is
arranged to provide data in substantially real time constituting an
image of the internal structures within the patient's body in the
vicinity of probe distal end 24. This representation includes a
depiction of the probe distal end and the transducer 30.
[0039] A sensor 51 such as a sensor for detecting magnetic field
components is also mounted to the distal end of a probe. Sensor 51
is connected by additional conductors (not shown) extending through
the probe body to the proximal end thereof to a position sensing
unit 53. Position sensing unit 53 may be arranged to detect the
position and/or orientation of sensor 51 based upon magnetic or
electromagnetic fields transmitted to or from sensor 51. As
described for example, in international patent publication WO
95/09562, the disclosure of which is incorporated by reference
herein, sensor 51 may be arranged to receive or transmit magnetic
field components, and may be used in conjunction with additional
sensors (not shown) mounted in a fixed frame of reference or in a
frame of reference fixed to the appropriate portion of the
patient's body. As described in these publications, position
sensing unit 53 is arranged to determine the position and/or
orientation of the probe distal end in such frame of reference. As
also described in these patents and publications, computer 78 can
combine the position and orientation of the probe distal end with
the imaging data from imaging system 82 so that the position and
orientation data and the imaging data are in a common frame of
reference. Display 82 can display a representation of the probe
distal end and transducer in the correct position relative to the
displayed anatomical structures. Such a representation may be
displayed in multiple views.
[0040] In operation, the probe distal end is advanced into the
patient until the probe distal end is disposed adjacent the region
of the patient to be treated. The probe may be advanced into
naturally occurring body cavities as, for example, the
gastrointestinal tract circulatory system, respiratory tract or
urinary tract. While the probe is being advanced, the transducer 30
desirably is in its fully collapsed or flat position 30' (FIG. 1)
so that the extent of the transducer in the directions transverse
to the axis 62 of the probe distal end is small. This facilitates
advancement of the probe through confined spaces within the
patient's body.
[0041] Once the probe distal end is near the anatomical structure
to be treated, the physician adjusts the curvature of the
transducer by operating knob 56 and linkage 54 so as to move the
control element or cable 50 and thereby pull the free end 44 of the
transducer towards the fixed end 42 and the distal end of the
probe. As the linkage is adjusted, switch 70 and resistance monitor
74 detect the curvature of the transducer. Computer 78 displays a
mark on the display unit 80 at a location corresponding to the
location of the center of curvature 64 of the transducer. This
location and orientation is computed from the location of the probe
distal end, as detected by transducer 51 and the curvature of the
transducer, as measured by resistance monitor 74.
[0042] As the physician adjusts linkage 60, resistance monitor 74
registers the changed curvature of transducer 30. The computer
displays the new location of center of curvature 64 superposed on
the depiction of anatomical structures derived from imaging unit
82. The computer may also display a representation of focal region
65 superposed on the anatomical features. When the physician is
satisfied that the center of curvature is in the appropriate
location relative to the anatomical features to be treated, he then
actuates the computer and HIFU driver to apply focused ultrasonic
energy at one or more desired locations within the focal region 65.
The design of ultrasonic phased arrays, and computer simulations of
such arrays are disclosed in Ebbini, et al., Optimization of the
Intensity Gain of Multiple-Focused Phased Array Heating Patterns,
Int. J. Hyperthermia, 1991, Vol. 7, #6, pp. 953-973; Ebbini et al.,
Multiple-Focused Ultrasound Phased-Array Pattern Synthesis: Optimal
Driving Signal Distributions for Hyperthermia, IEEE Transactions on
Ultrasonics, Ferro Electrics and Frequency Control, Vol. 36, pp.
540-548 (1989) and Fan et al., Control Over the Necrosed Tissue
Volume During Non-Invasive Ultrasound Surgery Using a 16-Element
Phased Array, Medical Physics, Vol. 22 (#3), pp. 297-305 (1995).
The disclosures of these articles are hereby incorporated by
reference herein. The curvature of the transducer can be adjusted
after application of some ultrasonic treatments so as to move the
center of curvature and the beam steering region. Also, the probe
may be repositioned as desired so as to shift the center of
curvature and beam steering region relative to the patient.
[0043] In a variant of the system discussed above, the curvature of
the transducer is monitored by monitoring the position of the
control element or cable 50' relative to the probe body 20'. For
example, a potentiometer 49 (FIG. 6), an optical encoder or other
conventional position monitoring devices may be connected between
the proximal end element 52' on the control cable and the proximal
end 22' of the probe body. Measurements of the relative position of
the control cable or control element 50' relative to the probe body
20' can be translated directly into curvature of transducer 30. In
a further variant, two or more position sensors 151 (FIG. 7),
similar to the position sensor 51 discussed above with reference to
FIGS. 1 and 2 may be provided on the deformable transducer itself.
The location and orientation of these sensors can be translated
into curvature of the transducer, as well as the position and
orientation of the transducer in the patient's frame of
reference.
[0044] In a probe according to a further variant (FIG. 8), the
transducer is provided as a set of transducer elements 230 disposed
along the length of the probe body 220 itself adjacent the distal
end thereof. At least the distal region of the probe body having
the transducers 230 thereon is arranged for flex in a controlled
fashion. The probe body may be provided with conventional devices
(not shown) for bending the probe body in a controlled fashion.
Transducer elements 230 may be individual, discrete transducers or
else may be regions of a unitary piezoelectric sheet as discussed
above with reference to FIG. 2. The transducer elements or sheet
constitute a spatially-distributed transducer extending along the
catheter tip. Bending of the probe body curves the array of
transducer elements so that energy from the transducer elements can
be focused onto a focal region 264. A flexible transducer of this
type may be provided with elements such as position sensors
disposed along the length of the probe or devices for detecting the
degree of curvature of the probe directly. In a further variant,
flexible distributed transducers as discussed above can be provided
with strain gauges formed separately from the piezoelectric
elements. For example, a flexible beam-like transducer may include
a strain-sensitive layer forming part or all of backing layer 34,
with appropriate electrodes connected to such layer. Also, a
discrete strain gauge such as a strain-sensitive wire may be
adhered to the beam element or embedded therein. Such strain gauges
can be used to monitor the curvature of the beam or other
distributed transducer.
[0045] Alternatively or additionally, curvature of the probe can be
monitored by imaging the probe and detecting the curvature based
upon such imaging. Detection can be accomplished visually, as by a
human operator observing the displayed image of the probe and
measuring the curvature on the display. Curvature also can be
detected by using conventional pattern-recognition programs to
detect the curved line of the probe in the data representing the
image, with or without display of the image in a human perceptible
form. These techniques can also be used to monitor the curvature of
a separate flexible transducer such as the transducer 30 discussed
above.
[0046] In further variants, individual, discrete transducer
elements, rather than a single continuous piezoelectric layer, may
be mounted on a flexible beam as illustrated in FIG. 2 to form a
spatially-distributed transducer. In yet another variant, a
spatially-distributed transducer having a continuous piezoelectric
layer as discussed above with reference to FIG. 2 may be provided
with only two thin, flexible electrodes, one electrode being
disposed on each surface. Such a distributed transducer would not
be capable of acting as a phased array. However, ultrasonic energy
emitted from such a transducer can be focused by changing the
curvature of the transducer.
[0047] Apparatus according to a further embodiment of the invention
(FIG. 9) has a flexible transducer array 330 in the form of a
diaphragm. The diaphragm is mounted in a housing 332 so that a
chamber 331 defined by the housing is closed by the diaphragm. By
increasing or decreasing the pressure within chamber 331, diaphragm
330 can be adjusted to a condition 330' of greater curvature or to
a position of lesser curvature (not shown). Diaphragm 330 may have
a structure similar to the structure of the beam-type transducer
element discussed above, and desirably includes a continuous layer
of a piezoelectric film with electrodes 336 and 338 disposed on
opposite sides of the piezoelectric film. However, the electrodes
desirably are disposed in a two-dimensional array on the surface of
the diaphragm. In a variant of this arrangement, a control element
may be connected to the diaphragm at its center for bending the
diaphragm to a more curved or less curved condition. Curvature of
such a diaphragm may be detected by impedance monitoring or other
techniques as discussed above.
[0048] Apparatus according to a further embodiment of the invention
(FIGS. 10 and 11) includes a set of supports 402. Each support has
a central end 404 and a peripheral end 406. The central ends of
these supports are pivotally connected to a common member 408,
which in turn is connected to the control element or cable 450. A
set of struts 410 is also provided. Each strut is pivotally
connected to one of the supports 402 between its central end 404
and peripheral end 406. Each strut is also pivotally connected to a
control member 412. Control member 412 is mounted to the distal end
424 of the probe body 420. Individual transducer elements 430 are
mounted to the supports 402 adjacent the peripheral ends thereof.
The transducer may be moved between the collapsed or closed
configuration illustrated in FIG. 10 to the expanded condition
illustrated in solid lines in FIG. 11, and to the further expanded,
over-center condition partially illustrated in broken lines in FIG.
11 by moving the control cable or control element 450 relative to
the probe body 420 so as to move the common member 408 relative to
control member 412. In the collapsed or closed configuration (FIG.
10), supports 402 lie close to the axis 462 of the probe body. In
the expanded condition, the supports project outwardly away from
axis 462. In the expanded, over center position depicted in broken
lines in FIG. 11, the various individual transducers 430' will tend
to focus their ultrasonic energy on a common focal location. The
position of such focal location can be adjusted by moving the
common member 408 relative to control member 412 so as to pivot the
supports 402.
[0049] Alternatively or additionally, transducers 432 may be
provided on the opposite sides of the support. Transducers 432 are
directed towards a common focus when the supports are in the
condition illustrated in solid lines in FIG. 11. In still further
variants, the connection of the control member 412 and of common
member 408 may be reversed. Thus, control member 412 may be
connected to cable or control element 450 whereas common member 408
may be mounted to the probe body. Also, the initial positions of
the elements may be reversed so that in the collapsed condition,
the supports 402 and struts 410 extend rearwardly along the probe
body rather than forwardly from the distal tip of the probe body.
Of course, the number of supports and struts may be varied. Also,
the measures discussed above for monitoring the curvature of a
continuous curved transducer may be used in the case of a
transducer having discrete transducer elements and separate
supports. Thus, position sensors may be provided on supports 402.
Alternatively, the position of the control element 450 relative to
the probe body 420 may be monitored.
[0050] A transducer assembly as shown in FIGS. 10 and 11 can be
used by advancing it in the closed or collapsed condition into a
natural body cavity as, for example, the urinary bladder and then
expanding the transducer assembly and bringing the transducer
elements to the appropriate locations to focus energy on a lesion
as, for example, a lesion within the prostate gland. After therapy,
the assembly desirably is returned to the closed or collapsed
configuration and extracted from the patient.
[0051] Probes as discussed above may be provided with balloons or
other flexible shields (not shown) covering the ultrasonic
transducer. In use, such a shield is filled with a liquid such as
water or saline solution, so that the shield bears against the
surrounding tissues. Ultrasonic energy from the transducer is
transmitted through the liquid and the shield to the patient's
body. Liquid may be circulated through the probe body, into and out
of the shield, to cool the transducer.
[0052] A probe according to a further embodiment of the invention
(FIGS. 12-14) includes a spatially-distributed collapsible
transducer 500 mounted to the distal end of an elongated probe 502.
Transducer 500 incorporates a plurality of leaves 504. As seen in
plan view (FIGS. 12 and 13) each leaf is generally wedge-shaped,
having a narrow end and a broad end. As seen in section (FIG. 14)
each leaf is curved. Each leaf has one or more transducer elements
thereon. For example, each leaf may include a continuous
piezoelectric layer with one or more electrodes as discussed above,
or with a set of discrete transducers. The narrow ends of the
leaves are pivotally connected to one another and to the probe body
502 for movement about a common pivot axis 506 transverse to the
direction of elongation of the probe. The leaves are movable
between the collapsed condition of FIG. 13 the expanded condition
of FIG. 12. In the expanded condition, the leaves wholly or
partially overlie one another, whereas in the expanded condition at
least a portion of each leaf is exposed and is not covered by
another leaf. As the transducer expands or collapses, the leaves
slide over one another. The collapsing and expanding action is
similar to the action of a traditional Japanese fan. The collapsing
and expanding action can be controlled by control cables or other
elements (not shown) extending through the probe. Alternatively or
additionally, the collapsing or expanding action can be driven by
spring mechanisms, electrical, hydraulic or pneumatic mechanisms,
or even by a small electric motor disposed adjacent the distal end
of the probe. Thermally-responsive elements such as bimetallic or
shape-memory metals can be employed.
[0053] In the collapsed condition, the distributed transducer is
small; all of the leaves lie close to the axis of probe body 502.
Therefore, the transducer can be advanced readily into a body
cavity. For example, the probe may be inserted vaginally, rectally
or orally and expanded inside the body of the patient. Desirably,
the radius of curvature of each leaf is selected so that sonic
energy emitted from all of the leaves when the leaves are in the
expanded condition is focused to a common point, line or region.
The leaves may be rigid or flexible. If the leaves are flexible,
control elements (not shown) similar to those discussed above may
be provided for deforming the individual leaves or deforming the
leaves together, and devices for monitoring the deformation of the
leaves may be provided as discussed above for monitoring individual
deformable elements.
[0054] The embodiment depicted in FIG. 15 illustrates one way of
implementing a bendable catheter 700 or other probe with a
transducer 702 distributed lengthwise along its distal end, as
discussed above with reference to FIG. 8. The interior of the probe
distal end desirably is filled with a liquid, gel or other
energy-transmissive medium so that sound can be transmitted from
the transducers 702 through the accordion-pleated wall 704 of the
probe. A cable 710 is provided with one end attached to the distal
end of the probe so that the probe 700 can be bent. The side
opposite the accordion-pleated wall 704 of the probe may have
expandable sides 712 to accommodate the bending of the probe. As
shown in FIG. 16, movable transducer in the form of a rigid
emitting dish 706 of suitable diameter is housed inside a liquid or
gel filled probe body having a balloon-like transmission window
708. The emitting dish is movably mounted to the probe body, so
that the location of the focal spot can be moved by moving the
dish.
[0055] The probe depicted in FIGS. 17 and 18 has a hollow body 600
having a noncircular cross-sectional shape adjacent its distal end,
so that the probe body defines dimension w in a widthwise direction
larger than its dimension t in a thickness direction, both such
directions being transverse to the axis of elongation 602 of the
probe. The distal end of the probe body desirably is formed from a
rigid polymer such as polycarbonate, whereas the remainder of the
probe may be flexible or rigid. The cross-sectional shape may be
uniform throughout the length of the probe, or may gradually merge
into a circular or other shape adjacent the proximal end of the
probe body (not shown). The probe body has a window 604 extending
lengthwise along the probe and extending in the widthwise direction
of the probe. The window is covered by a thin energy-transmissive
membrane such as a film or shrink band formed from a polymer such
as polyimide or glycol-modified polyethelyene terephtalate
("PETG"). A spatially-distributed transducer 606 is mounted in the
probe body. Transducer 606 has an emitting surface facing towards
the window, generally in the thickness direction t. Transducer 606
also extends in the widthwise direction and lengthwise directions
of the probe body. The projected area of transducer 606 is greater
than the projected area of a transducer which could fit within a
probe body of circular cross section having the same
cross-sectional area. All else being equal, this provides greater
sonic energy emission in a probe which can be threaded into a given
bodily cavity or orifice.
[0056] Transducer 606 is deformable. The transducer may include a
unitary piezoelectric layer or a set of plural piezoelectric
devices mounted to a deformable element. The transducer may include
a beam-like element as discussed above, curved about an axis of
curvature 608 which extends in the widthwise direction of the probe
body. One end of the beam, desirably the proximal end 610, is fixed
to the probe body, whereas the opposite end 612 is free to slide
within the probe body. One or more slide elements 614 are disposed
within the probe body. The slide elements are connected to control
devices (not shown) allowing the user to selectively slide one or
more of the slide elements from the disengaged positions
illustrated in FIG. 17 to engaged positions in which the slide
elements are disposed between transducer 606 and the wall of the
probe body. The control devices may include portions of the slide
elements 614, or cables connected thereto, extending to the
proximal end of the probe body so that the user can selectively
manipulate the slide elements. Other devices such as hydraulic,
pneumatic or electromechanical actuators can be used. In a rest
condition, with all of the slide elements in their disengaged
positions, transducer 606 rests against the rear wall of the probe
body opposite from window 604. In this condition, transducer 606
has a minimum radius of curvature. The user can change the
curvature of the transducer by advancing one or more of the slide
elements to engaged positions as indicated at 614' in FIG. 17. As
the slide elements are engaged, the transducer is deformed to
less-curved positions 606', 606", etc. With each combination of
engaged and disengaged slide elements, the transducer has a known
curvature. Therefore, there is no need for measurement devices to
monitor the degree of curvature of the transducer.
[0057] The probe further includes cooling fluid passages 616 for
conducting a coolant such as water or other energy-transmissive
liquid into and out of the probe distal end. These passages may be
formed integrally with the probe body, or may be formed integrally
with one or more of the slide elements.
[0058] In a variant of the probe shown in FIGS. 17 and 18, the
transducer may be generally dome shaped, so that the transducer is
curved about a first axis transverse to the axis of elongation of
the probe body and along a second axis parallel to the axis of
elongation of the probe body. One spot on the transducer is secured
to the probe body. Here again, moving the slide elements into or
out of engaged positions serves to flatten the dome to some degree
or to allow the dome to return to a more curved condition. Also,
although the term "slide element" is used in the above discussion
for ease of reference, the slide elements can be brought into and
out of their respective engaged positions by rotary or other
movement rather than sliding motion.
[0059] In the embodiments discussed above, the ultrasonic
transducers include piezoelectric elements. However, the invention
can also be applied with other types of ultrasonic transducers as,
for example, magnetostrictive elements.
[0060] As these and other variations and combinations of the
features discussed above can be utilized, the foregoing description
of the preferred embodiment should be taken by way of illustration
rather than by way of limitation of the invention.
* * * * *