U.S. patent application number 11/289926 was filed with the patent office on 2007-07-19 for rotatable transducer array for volumetric ultrasound.
Invention is credited to Abdulrahman Abdallah Al-Khalidy, Weston Blaine Griffin, Warren Lee, Douglas Glenn Wildes.
Application Number | 20070167821 11/289926 |
Document ID | / |
Family ID | 38056253 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070167821 |
Kind Code |
A1 |
Lee; Warren ; et
al. |
July 19, 2007 |
Rotatable transducer array for volumetric ultrasound
Abstract
A rotating transducer assembly and method for use in volumetric
ultrasound imaging and catheter-guided procedures are provided. The
rotating transducer assembly comprises a transducer array mounted
on a drive shaft and the transducer array is rotatable with the
drive shaft, a motion controller coupled to the transducer array
and the drive shaft for rotating the transducer, and at least one
interconnect assembly coupled to the transducer for transmitting
signals between the transducer and an imaging device, wherein the
interconnection assembly is configured to reduce its respective
torque load on the transducer and motion controller due to a
rotating motion of the transducer.
Inventors: |
Lee; Warren; (Clifton Park,
NY) ; Wildes; Douglas Glenn; (Ballston Lake, NY)
; Al-Khalidy; Abdulrahman Abdallah; (Niskayuna, NY)
; Griffin; Weston Blaine; (Guilderland, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Family ID: |
38056253 |
Appl. No.: |
11/289926 |
Filed: |
November 30, 2005 |
Current U.S.
Class: |
600/463 |
Current CPC
Class: |
A61B 8/4488 20130101;
A61B 8/4461 20130101; A61B 8/445 20130101; A61B 8/483 20130101;
A61B 8/12 20130101 |
Class at
Publication: |
600/463 |
International
Class: |
A61B 8/14 20060101
A61B008/14 |
Claims
1. A rotating transducer array assembly for use in volumetric
ultrasound imaging procedures, the assembly comprising: a
transducer array; a motion controller coupled to the transducer
array for rotating the transducer array; at least one interconnect
assembly coupled to the transducer array for transmitting signals
between the transducer and an imaging device, wherein the
interconnection assembly is configured to reduce its respective
torque load on the transducer and motion controller due to a
rotating motion of the transducer.
2. The rotating transducer array assembly of claim 1 wherein the
transducer array is mounted on a drive shaft and the transducer
array is rotatable with the drive shaft.
3. The rotating transducer array assembly of claim 1 further
comprising a catheter housing for enclosing the rotating transducer
assembly.
4. The rotating transducer array assembly of claim 3 wherein the
catheter housing further comprises an acoustic window to allow for
coupling of acoustic energy from the transducer array to a region
of interest.
5. The rotating transducer array assembly of claim 3 wherein the
motion controller comprises: a micromotor coupled to the drive
shaft for rotating the transducer; and, a motor controller for
controlling the micromotor.
6. The rotating transducer array assembly of claim 5 wherein the
motor controller is contained internal to the catheter housing.
7. The rotating transducer array assembly of claim 5 wherein the
motor controller is external to the catheter housing.
8. The rotating transducer array assembly of claim 1 wherein the
interconnect comprises a plurality of conductors for transmitting
image data acquired by the transducer to an imaging device.
9. The rotating transducer array assembly of claim 1 wherein the
interconnect assembly is adapted to reduce rotational stiffness of
at least a rotating portion of the interconnect assembly.
10. The rotating transducer array assembly of claim 9 wherein the
interconnect assembly comprises flexible cable that is
de-ribbonized in the rotating portion.
11. The rotating transducer array assembly of claim 10 wherein the
flexible cable is de-ribbonized by at least one of the following
methods: removal of any common substrate, ground plane, or other
connection between adjacent conducers of the flexible cable or
reducing dielectric or shield layers around individual conductors
or coaxes of the flexible cable.
12. The rotating transducer array assembly of claim 9 wherein the
interconnect cable comprises slits in non-conducting portions of
the flexible cable.
13. The rotating transducer array assembly of claim 1 wherein the
transducer array comprises a one-dimensional (1D) transducer
array.
14. The rotating transducer array assembly of claim 1 wherein the
motion controller comprises one or more actuators attached to the
transducer array and used to effect rotation of the transducer
array.
15. The rotating transducer array assembly of claim 1 wherein the
motion controller comprises one or more actuators and springs
attached to the transducer array and used to effect rotation of the
transducer array
16. The rotating transducer array assembly of claim 1 wherein the
motion controller comprises at least one bladder in contact with
the transducer array wherein the bladders are controlled to effect
rotation of the transducer array about a pivot point.
17. The rotating transducer array assembly of claim 16 wherein the
bladders are filled with at least one of a gas and liquid and the
bladders are controlled by inflation and deflation of the
bladders.
18. The rotating transducer array assembly of claim 14 wherein the
motion controller further comprises a cable and pulley assembly
coupled to the transducer for effecting rotation of the transducer
array.
19. The rotating transducer array assembly of claim 14 wherein the
motion controller further comprises a gear interface coupled to the
transducer for effecting rotation of the transducer array.
20. A method for performing volumetric ultrasound imaging, the
method comprising: obtaining imaging data for at least one region
of interest using an imaging catheter, wherein the imaging catheter
comprises: a transducer array; a motion controller coupled to the
transducer array for rotating the transducer; at least one
interconnect assembly coupled to the transducer for transmitting
signals between the transducer and an imaging device, wherein the
interconnection assembly is configured to reduce its respective
torque load on the transducer and motion controller due to a
rotating motion of the transducer; and displaying the imaging data
for use in at least one of imaging and treatment of a selected
region of interest.
21. The method of claim 20 wherein the transducer array is mounted
on a drive shaft and the transducer array is rotatable with the
drive shaft.
22. The method of claim 20 wherein the transducer array is used to
scan an ultrasound beam in an azimuth direction and the motion
controller is used to rotate the transducer array in an elevation
dimension in order to obtain three-dimensional (3D) volumetric
imaging data of the region of interest.
23. The method of claim 20 wherein the imaging catheter further
comprises a fluid-filled acoustic window to allow for coupling of
acoustic energy from the transducer array to the region of
interest.
24. The method of claim 20 wherein the interconnect assembly is
adapted to reduce rotational stiffness of at least a rotating
portion of the interconnect assembly.
25. The method of claim 20 wherein the motion controller comprises
at least one of motors, actuators and mechanical devices coupled to
the transducer array for effecting at least one of oscillation and
rotation of the transducer array for obtaining volumetric imaging
data of the region of interest.
26. The method of claim 20 further comprising the step of
delivering treatment to the selected regions of interest.
Description
BACKGROUND
[0001] The invention relates generally to a rotating transducer
array system, and more particularly to a rotatable transducer array
assembly for use in volumetric ultrasound imaging and
catheter-guided treatment such as cardiac interventional
procedures.
[0002] Cardiac interventional procedures such as the ablation of
atrial fibrillation are complicated due to the lack of an efficient
method to visualize the cardiac anatomy in real-time. Intracardiac
echocardiography (ICE) has recently gained interest as a potential
method to visualize interventional devices as well as cardiac
anatomy in real-time. Current commercially available catheter-based
intracardiac probes used for clinical ultrasound B-scan imaging
have limitations associated with the monoplanar nature of the
B-scan images. Real-time three-dimensional (RT3D) imaging may
overcome these limitations. Existing one-dimensional (1D) catheter
transducers have been used to make 3D ICE images by rotating the
entire catheter, but the resulting images are not real-time. Other
available RT3D ICE catheters use a two-dimensional (2D) array
transducer to steer and focus the ultrasound beam over a
pyramidal-shaped volume. Unfortunately, 2D array transducers
require prohibitively large numbers of interconnections in order to
adequately sample the acoustic aperture space to achieve sufficient
spatial resolution and image quality. In addition, other challenges
exist with 2D arrays, such as low sensitivity due to the small
element size, and increases in system cost and complexity.
Additionally, due to catheter size constraints, 2D arrays have
fewer elements than desirable as well as small apertures thereby
contributing to poor resolution and contrast and ultimately poor
image quality.
[0003] The issue of acquiring three-dimensional volumes has been
addressed with the advent of 2D array transducers (e.g., Philips X4
or GE 3V probes), however, their applicability to space-constrained
applications such as intracardiac echocardiography is limited due
to the unachievable number of signal conductors and/or beamforming
electronics that are required in order to adequately sample the
aperture space and generate images with sufficient resolution.
Further, there are rotating single-element or annular array
transducers in catheters (e.g., Boston Scientific), however images
are 2D or cone images, not 3D volumes. Mechanically scanning
one-dimensional transducer arrays currently exist (e.g., GE Kretz
"4D" probes), but have only been applied to much larger abdominal
probes, where space constraints do not exist.
[0004] As intracardiac interventional procedures are more commonly
used, there is a need to overcome the problems described above.
Further, there is a need to enable improved intracardiac imaging
and interventional procedures, particularly where there are space
constraints.
BRIEF DESCRIPTION
[0005] In a first aspect of the invention, a rotating transducer
assembly for use in volumetric ultrasound imaging and
catheter-guided procedures is provided. The rotating transducer
assembly comprises a transducer array mounted on a drive shaft, a
motion controller coupled to the transducer array and the drive
shaft for rotating the transducer, and at least one interconnect
assembly coupled to the transducer for transmitting signals between
the transducer and an imaging device, wherein the interconnection
assembly is configured to reduce its respective torque load on the
transducer and motion controller due to a rotating motion of the
transducer.
[0006] In a second aspect of the invention, a method for volumetric
imaging and catheter-guided procedures is provided. The method
comprises obtaining imaging data for at least one region of
interest using an imaging catheter and displaying the imaging data
for use in at least one of imaging and treatment of a selected
region of interest. The imaging catheter comprises a transducer
array mounted on a drive shaft, the transducer array rotatable with
the drive shaft, a motion controller coupled to the transducer
array and the drive shaft for rotating the transducer, and at least
one interconnect assembly coupled to the transducer for
transmitting signals between the transducer and an imaging device,
wherein the interconnection assembly is configured to reduce its
respective torque load on the transducer and motion controller due
to a rotating motion of the transducer.
DRAWINGS
[0007] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a block diagram of an exemplary ultrasound imaging
and therapy system, in accordance with aspects of the present
technique;
[0009] FIG. 2 is a side and internal view of an exemplary
embodiment of a rotating transducer array assembly for use in the
imaging system of FIG. 1;
[0010] FIG. 3 is an illustration of components of a rotating
transducer array that are applicable to embodiments of the present
invention;
[0011] FIG. 4 is another illustration of a catheter for use in the
imaging system of FIG. 1;
[0012] FIG. 5 is an illustration of an interconnect assembly to
which embodiments of the present invention are applicable;
[0013] FIG. 6 is an illustration of an interconnect assembly to
which embodiments of the present invention are applicable;
[0014] FIG. 7 is an illustration of an interconnect assembly to
which embodiments of the present invention are applicable;
[0015] FIG. 8 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0016] FIG. 9 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0017] FIG. 10 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0018] FIG. 11 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0019] FIG. 12 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0020] FIG. 13 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0021] FIG. 14 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable;
[0022] FIG. 15 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable; and,
[0023] FIG. 16 is an illustration of an alternative embodiment of a
motion controller to which embodiments of the present invention are
applicable.
DETAILED DESCRIPTION
[0024] As will be described in detail hereinafter, a rotating
transducer array assembly in accordance with exemplary aspects of
the present technique is presented. Based on image data acquired by
the rotating transducer array via an imaging and therapy catheter,
diagnostic information and/or the need for therapy in an anatomical
region may be obtained.
[0025] In accordance with aspects of the present invention, the
aforementioned limitations are overcome by using a mechanically
rotating, one-dimensional transducer array that sweeps out a
three-dimensional volume. The elements of the transducer array are
electronically phased in order to acquire a sector image parallel
to the long axis of the catheter, and the array is mechanically
rotated around the catheter axis in order to acquire the
three-dimensional volume through assembly of two-dimensional
images. This method results in a spatial resolution and contrast
resolution far superior to what may be achieved using a
two-dimensional array transducer and current interconnection
technology. In addition, problems associated with 2D arrays such as
sensitivity and system cost and complexity are avoided using this
method. It is to be appreciated that transducer arrays other than
1D arrays may be used, but then complexity is added
[0026] FIG. 1 is a block diagram of an exemplary system 10 for use
in imaging and providing therapy to one or more regions of interest
in accordance with aspects of the present technique. The system 10
may be configured to acquire image data from a patient 12 via a
catheter 14. As used herein, "catheter" is broadly used to include
conventional catheters, endoscopes, laparoscopes, transducers,
probes or devices adapted for imaging as well as adapted for
applying therapy. Further, as used herein, "imaging" is broadly
used to include two-dimensional imaging, three-dimensional imaging,
or preferably, real-time three-dimensional imaging. Reference
numeral 16 is representative of a portion of the catheter 14
disposed inside the body of the patient 12.
[0027] In certain embodiments, an imaging orientation of the
imaging and therapy catheter 14 may include a forward viewing
catheter or a side viewing catheter. However, a combination of
forward viewing and side viewing catheters may also be employed as
the catheter 14. Catheter 14 may include a real-time imaging and
therapy transducer (not shown). According to aspects of the present
technique, the imaging and therapy transducer may include
integrated imaging and therapy components. Alternatively, the
imaging and therapy transducer may include separate imaging and
therapy components. The transducer in an exemplary embodiment is a
one-dimensional (1D) transducer array and will be described further
with reference to FIG. 2. It should be noted that although the
embodiments illustrated are described in the context of a
catheter-based transducer, other types of transducers such as
transesophageal transducers or transthoracic transducers are also
contemplated.
[0028] In accordance with aspects of the present technique, the
catheter 14 may be configured to image an anatomical region to
facilitate assessing need for therapy in one or more regions of
interest within the anatomical region of the patient 12 being
imaged. Additionally, the catheter 14 may also be configured to
deliver therapy to the identified one or more regions of interest.
As used herein, "therapy" is representative of ablation,
percutaneous ethanol injection (PEI), cryotherapy, and
laser-induced thermotherapy. Additionally, "therapy" may also
include delivery of tools, such as needles for delivering gene
therapy, for example. Additionally, as used herein, "delivering"
may include various means of guiding and/or providing therapy to
the one or more regions of interest, such as conveying therapy to
the one or more regions of interest or directing therapy towards
the one or more regions of interest. As will be appreciated, in
certain embodiments the delivery of therapy, such as RF ablation,
may necessitate physical contact with the one or more regions of
interest requiring therapy. However, in certain other embodiments,
the delivery of therapy, such as high intensity focused ultrasound
(HIFU) energy, may not require physical contact with the one or
more regions of interest requiring therapy.
[0029] The system 10 may also include a medical imaging system 18
that is in operative association with the catheter 14 and
configured to image one or more regions of interest. The imaging
system 10 may also be configured to provide feedback for therapy
delivered by the catheter or separate therapy device (not shown).
Accordingly, in one embodiment, the medical imaging system 18 may
be configured to provide control signals to the catheter 14 to
excite a therapy component of the imaging and therapy transducer
and deliver therapy to the one or more regions of interest. In
addition, the medical imaging system 18 may be configured to
acquire image data representative of the anatomical region of the
patient 12 via the catheter 14. As used herein, "adapted to",
"configured" and the like refer to mechanical, electrical or
structural connections between elements to allow the elements to
cooperate to provide a described effect; these terms also refer to
operation capabilities of electrical elements such as analog or
digital computers or application specific devices (such as an
application specific integrated circuit (ASIC)) that are programmed
to perform a sequel to provide an output in response to given input
signals.
[0030] As illustrated in FIG. 1, the imaging system 18 may include
a display area 20 and a user interface area 22. However, in certain
embodiments, such as in a touch screen, the display area 20 and the
user interface area 22 may overlap. Also, in some embodiments, the
display area 20 and the user interface area 22 may include a common
area. In accordance with aspects of the present technique, the
display area 20 of the medical imaging system 18 may be configured
to display an image generated by the medical imaging system 18
based on the image data acquired via the catheter 14. Additionally,
the display area 20 may be configured to aid the user in defining
and visualizing a user-defined therapy pathway. It should be noted
that the display area 20 may include a three-dimensional display
area. In one embodiment, the three-dimensional display may be
configured to aid in identifying and visualizing three-dimensional
shapes. It should be noted that the display area 20 and respective
controls could be remote from the patient, for example a control
station and a boom display disposed over the patient and/or a
control station and display in a separate room, e.g. the control
area for an EP suite or catheterization lab.
[0031] Further, the user interface area 22 of the medical imaging
system 18 may include a human interface device (not shown)
configured to facilitate the identification of one or more regions
of interest for delivering therapy using the image of the
anatomical region displayed on the display area 20. The human
interface device may include a mouse-type device, a trackball, a
joystick, a stylus, or a touch screen configured to assist the user
to identify the one or more regions of interest requiring therapy
for display on the display area 20.
[0032] As depicted in FIG. 1, the system 10 may include an optional
catheter positioning system 24 configured to reposition the
catheter 14 within the patient 12 in response to input from the
user. Moreover, the system 10 may also include an optional feedback
system 26 that is in operative association with the catheter
positioning system 24 and the medical imaging system 18. The
feedback system 26 may be configured to facilitate communication
between the catheter positioning system 24 and the medical imaging
system 18.
[0033] FIG. 2 is an illustration of an exemplary embodiment of a
rotating transducer array assembly 100 for use in the imaging
system of FIG. 1. As shown, the transducer array assembly 100
comprises a transducer array 110, a micromotor 120, which may be
internal or external to the space-critical environment, a drive
shaft 130 or other mechanical connections between motor controller
140 and the transducer array 110. The assembly further includes
interconnect 150, which will be described in greater detail with
reference to FIG. 3. The assembly 100 further includes a catheter
housing 160 for enclosing the transducer array 110, micromotor 120,
interconnect 150 and drive shaft 130. In this embodiment, the
transducer array 110 is mounted on drive shaft 130 and the
transducer array 110 is rotatable with the drive shaft 130. Further
in this embodiment, the rotation motion of the transducer array 110
is controlled by motor controller 140 and micromotor 120. Motor
controller 140 and micromotor 120 control the motion of transducer
array 100 for rotating the transducer. In an embodiment, the
micromotor is placed in proximity to the transducer array for
rotating the transducer and drive shaft and the motor controller is
used to control and send signals to the micromotor 120.
Interconnect 150 refers to, for example, cables and other
connections coupled between the transducer array 110 and the
imaging system shown in FIG. 1 for use in receiving/transmitting
signals between the transducer and the imaging system. In an
embodiment, interconnect 150 is configured to reduce its respective
torque load on the transducer and motion controller due to a
rotating motion of the transducer which will be described in
greater detail with reference to FIG. 3 below. Catheter housing 160
is of a material, size and shape adaptable for internal imaging
applications and insertion into regions of interest. The catheter
further includes a fluid-filled acoustic window 170 shown in FIG.
4. Fluid-filled acoustic window 170 is provided to allow coupling
of acoustic energy from the rotating transducer array to the region
or medium of interest. In embodiments, catheter housing 160 is
acoustically transparent, e.g. low attenuation and scattering,
acoustic impedance near that of blood and tissue (Z.about.1.5M
Rayl) in the acoustic window region. Further, in embodiments, the
space between the transducer and the housing is filled with an
acoustic coupling fluid, e.g., water, with acoustic impedance and
sound velocity near those of blood and tissue (Z.about.1.5 M Rayl,
V.about.1540 m/sec).
[0034] In an embodiment, the motor controller is external to the
catheter housing as shown in FIG. 2. In another embodiment, the
motor controller is internal to the cathether housing. It is to be
appreciated that as micromotors and motor controllers are becoming
available in miniaturized configurations that may be applicable to
embodiments of the present invention. Micromotor and motor
controller dimensions are selected to be compatible with the
desired application, for example to fit within the catheter for a
particular intracavity or intravascular clinical application. For
example, in ICE applications, the catheter housing and components
contained therein may be in the range of about 1 mm to about 4 mm
in diameter. As is well-known, most catheters include a disposable
and non-disposable component if there is an opportunity to re-use a
portion of the catheter. Motion controller and/or motor may be
enclosed in the disposable or non-disposable portion of the probe
in embodiments.
[0035] Referring to FIG. 3, an internal view of the catheter
assembly 14 of FIG. 1 is illustrated showing the internal
components and arrangement of transducer 110 and interconnect 150.
In an exemplary embodiment, transducer array 110 is a 64-element 1D
array having .110 mm azimuth pitch, 2.5 mm elevation and 6.5 MHz
frequency. A cylindrical transducer assembly 210 is adapted to fit
and rotate effectively within a cylinder of about 2.8 mm inner
diameter which would be an appropriate inner dimension of catheter
housing 160 (shown in FIG. 2) for intracardiac applications such as
ICE. Interconnect 150 is coupled to the transducer 110 and
comprises the necessary cables and conductors for transmitting
image information between the transducer 110 and imaging system 18
(FIG. 1). As used herein, the terms "cables" and "conductors" are
used interchangeably to refer to the cables and conductor
assemblies within the catheter. Additionally, the catheter may
include one or more wires 114 that may be used at the insertion end
of the catheter and pass by the transducer 110 to the tip of the
cathether and these wires 114 may be used for, including but not
limited to motor control power, position sensing, thermistors,
catheter position sensors (e.g. electromagnetic coils), transducer
rotation sensors (optical or magnetic encoder), EP sensor or
ablation electrodes, and so forth. Further in this embodiment,
within the catheter 14 of FIG. 1, there is a flexible region 116 of
the interconnect 150. The length of the flexible region 116 is
desirably selected such that during rotation or oscillation of
transducer 110 the conductors 180 exert torque that will not
interfere or hamper rotation of the transducer, drive shaft or
motor. As used herein, the term "rotate" will refer to oscillatory
or rotary motion or movement between a selected +/- degrees of
angular range. Oscillatory or rotary motion includes but is not
limited to full or partial motion in a clock-wise or
counter-clockwise direction or motion between a positive and
negative range of angular degrees. Further embodiments for
interconnect 150 will be described with reference to FIG. 5-7.
[0036] In an embodiment, transducer array 110 is a one-dimensional
(1D) transducer array. Rotation of a 1D transducer array provides
improved three-dimensional (3D) image resolution for the following
reasons: the ultrasound beam profile and image resolution depend on
the active aperture size; relative to 2D arrays, the active
aperture for a 1D array is not as restricted by available system
channels, nor by interconnect requirements. Using a 1D transducer
array in the rotating configuration enables generation of
high-quality real-time three-dimensional ultrasound images. Thus,
limitations associated with the monoplanar nature of the current
commercially available ICE catheters are overcome, and the guidance
of cardiac interventional procedures may be substantially
simplified.
[0037] Referring to FIG. 5-7, embodiments for interconnect 150 are
further illustrated. The signal and ground electrical connections
from the transducer array through a catheter to the imaging system
may be implemented with either 1) flex circuits, 2) coax cables
(one coax per signal), or 3) ribbon cable (e.g., Gore microFlat).
The bundle of electrical connections can be quite stiff in torsion
and will create a substantial spring or drag force opposing
rotation of the transducer array. In accordance with embodiments of
the present invention, interconnect 150 is configured to reduce the
torque or drag force exerted by the interconnect against the
rotation of the transducer and/or drive shaft. Referring to FIG. 5,
in one embodiment, a section of the interconnect (conductors 180)
is coiled to reduce torque. Referring to FIG. 6, in one embodiment,
in order to reduce the stiffness of the connections, a region of
conductors near the transducer may be de-ribbonized (use, e.g. a
laser, to remove any common substrate, ground plane, or other
connection between adjacent conducers; perhaps reduce the
dielectric or shield layers around individual conductors or coaxes)
to create a loose group of conductors 190. During assembly of the
catheter, this group of loose conductors 190 should be left slack,
not taut, to further facilitate movement of the conductors relative
to each other and rotation of the transducer array 110. Referring
to FIG. 6, a section of conductors 200 and 202 adjacent to the
loose section 190 may be left ribbonized as a ribbonized section,
to facilitate termination of the conductors on ribbonized section
202 to the transducer 110 or to the transducer flex circuit(s) and
the conductors on ribbonized section 200 to a non-rotating cable
through the catheter. The majority of the length of the conductors
in the catheter, beyond the loose section, may be ribbonized, for
ease of assembly, or may be loose insulated wires, for maximum
flexibility of the catheter, or the conductors may be coaxial
conductors for control of impedance and crosstalk. Alternatively,
referring to FIG. 7, a rotating section 202 of conductors
terminated at the transducer array 110 may be constructed or
modified to ease the torque requirements necessary for rotation.
For example, the rotational stiffness may be reduced by cutting
slits 230 into the ribbon or flex circuit and by making this
section of the interconnect thinner relative to the non-rotating
section 200 coupled to the cable end of the catheter. In additional
embodiments utilizing ribbon-based cables, the substrate on which
the conductors lie may be thinned or removed in the rotating
section of the interconnect 150. In further embodiments utilizing
ribbon-based cables having ground planes, the ground planes may be
thinned or removed in the rotating section. It is to be appreciated
that combinations of the techniques described above may be used to
reduce the torque requirements of the interconnect 150 under
rotating conditions.
[0038] Referring now to FIG. 8, an alternative embodiment for a
rotating transducer array assembly comprises an external motor 320
used to rotate the drive shaft 130 and an external motor controller
330 for driving motor 320. A rotary encoder or position sensor 340
provides feedback to compensate for any wind-up in the drive shaft.
In this embodiment the drive shaft 130 would desirably be made of
torsionally rigid material, e.g. steel wire, to minimize wind-up or
twisting of the drive shaft due to torque applied by the motor and
friction of components rotating within the catheter and to further
enable effective rotation of the transducer.
[0039] Referring now to FIG. 9-13, various alternative embodiments
for the motion controller for rotating the transducer array
assembly are provided. In these embodiments, the motion controller
converts internal or external linear motion to oscillatory rotary
motion of the transducer array instead of using the micromotor 120
and motor controller 140 of FIG. 2. Similar components common to
FIG. 2 and subsequent figures will have the same reference
numbers.
[0040] Referring first to FIG. 9, an embodiment for the motion
controller comprises an actuator 400, which can be internal or
external to the catheter, used to effect oscillation and/or
rotation of the transducer array. The actuator 400 creates a linear
motion of the drive shaft 130 which is converted to an oscillatory
rotary motion. A sleeve 410 is slidable over transducer cylinder
210 which encloses transducer array 110. The sleeve 410 includes
small pins 420 which engage in spiral guide tracks 430. In
operation, as the sleeve 420 moves along the length of the
cylinder/encapsulation, the cylinder/encapsulation rotates a given
amount determined by the spiral guide tracks 430. The reciprocating
linear motion of the sleeve creates an oscillatory motion of the
cylinder/encapsulation housing the transducer array 110, allowing
the transducer array to rotate and acquire a 3D pyramidal volume.
The linear motion part that engages the spiral guide track 430 may
be partially constrained for one degree of freedom along the axis
of the catheter. A rotary encoder or position sensor 340 may
provide feedback to compensate for flexibilities in the system,
e.g. the drive shaft, linear-rotary converter, and the like.
[0041] Referring now to FIG. 10, another exemplary embodiment for
the motion controller comprises an actuator, either external or
internal (not shown), for driving a cable 440 for effecting
rotation of transducer array 110. Cable 440 is a beaded or studded
cable including beads 450 placed along the length of cable 440 to
engage in spiral guide track 430. In one embodiment, as bead 450
engages the spiral guide track 430 and travels the length of
cylinder 210 terminating at drive pulley 460, the cylinder 210
rotates 90 degrees. After a quarter revolution, another bead 450
engages the spiral guide track on the opposite side of the cylinder
(shown by dashed lines) and causes the cylinder to rotate 90
degrees in the opposite direction. Thus the cylinder 210 containing
the transducer array 110 oscillates 90 degrees total or +/- 45
degrees. The oscillation described herein is for exemplary
purposes. It is to be appreciated that other angles may be used to
effect oscillation in the manners described in this embodiment. In
a further embodiment, a rotary encoder or position sensor (not
shown) such as one described with reference to FIG. 9 may be
included to provide feedback to compensate for flexibilities and
errors in the system. Alternative embodiments are also
contemplated. For example, in another embodiment, only two beads
are needed and spaced to allow motion of cable the full length of
cylinder 210. After one bead moves the length of the cylinder, the
cable is driven in the opposite direction and pulled back, thereby
allowing the cylinder housing containing the transducer array to
oscillate +/- 90 degrees. In a further embodiment, a variety of
angular ranges could be used.
[0042] Referring to FIG. 11-13, various alternative embodiments for
motion control comprise cable and pulley systems for effecting
oscillatory rotary motion of the transducer array. In FIG. 11,
cables 440 engage with drive pulley 460. An actuator (not shown)
drives a cable and pulley 460 in a fixed direction with a
continuous motion. Attached to the drive pulley 460, which is
rotating, is an extension or flapper 470 which impacts a catch 480
attached to the transducer array 110 once per revolution. The
flapper 470 forces the rotation of the array cylinder 210 along the
long axis. Once the flapper 470 clears the catch 480, the cylinder
210 returns to a nominal position with the aid of a torsion spring
490 and the velocity is limited by a rotary vane damper 500. By
driving the pulley 460 with flapper 470 at a constant rate, the
cylinder 210 containing the transducer array 110 will undergo an
oscillatory motion. Thus the transducer array 110 will oscillate
such that the acquisition of a 3D pyramidal volume can be obtained.
The torsion spring 490 and rotary vane damper 500 may be adjusted
for appropriate timing of the motion of the cylinder 210. A rotary
encoder or position sensor (not shown) may also be used in further
embodiments to provide feedback to compensate for flexibilities and
errors in the system.
[0043] Referring to FIG. 12 and 13, alternative embodiments to FIG.
11 are provided wherein the cylinder 210 further comprises a gear
interface 510 to engage with a gear portion of drive pulley 460. In
FIG. 12, the pulley 460 and cylinder housing 210 are connected
using a bevel gear interface or approximation thereof. In FIG. 13,
pulley 460 and cylinder 210 are connected using a bevel gear
interface and pulley 460 further comprises two different gear
sections, one on an upper section of pulley 460 and one on a lower
section, such that the gear sections of the pulley alternately
interface with the cylinder housing and drive motion in a fixed
direction. In both embodiments, the drive and pulley motion effects
rotation of the transducer array 110 in order to acquire a 3D
pyramidal imaging volume.
[0044] Referring now to FIG. 14-16, additional embodiments for the
motion controller are provided. Referring to FIG. 14A, a side view
shows one or more actuators 600 are attached to each side of the
transducer array 110 at a first end and fixed to the catheter tube
at the other end. Actuator control lines 610 are used to control
activation of the actuator. The actuators on either side of the
array are alternatively activated, which causes the array to
oscillate about pivot point 620. Actuators 600 may include
electroactive polymers. A rotary encoder 340 may provide positional
information as has been described in previous embodiments. FIG.
14B-D are end views of this embodiment in operation to effect
rotation of transducer 110. In FIG. 14B, a first actuator A is
fully activated and actuator B is fully deactivated. In FIG. 14B,
actuator A is partially activated and actuator B is partially
activated. In FIG. 14D, actuator A is fully deactivated and
actuator B is fully activated.
[0045] Referring to FIG. 15, a similar embodiment is shown but
rather than using two actuators, one actuator 600 is provided and
attached to the transducer array 110 at one end and a spring 630 is
attached at the other end and to the catheter cylinder 210.
Movement of the actuator extends or contracts the spring as shown
in FIG. 15A-C to effect rotation of transducer array 110. The
actuator and/or spring may also be torsional, as well as
linear.
[0046] Referring to FIG. 16, a further embodiment for motion
control is provided. In this embodiment, two bladders 640 are in
contact with the transducer array 110. The bladders may be filled
with a gas or liquid. The inflation and deflation of the bladders
is controlled in such a way as to oscillate the transducer 110
about pivot point 620. In this manner, a 3D volume may be
acquired.
[0047] In operation, in accordance with embodiments of the present
invention a miniature transducer array with elements along an
azimuth dimension (long axis of catheter), preferably capable of
operating at high frequencies for improved resolution is coupled to
a mechanical system that rotates the array along its elevation
dimension. The ultrasound beam is electronically scanned in the
azimuth dimension, creating a two-dimensional image, and
mechanically scanned in the elevation dimension. The
two-dimensional images may then be assembled into a full
three-dimensional volume by the ultrasound system. The transducer
may take on a variety of shapes, including (but not limited to):
(1) linear sector phased arrays which would result in
two-dimensional image in the shape of a sector, and a
three-dimensional volume in the shape of a pyramidal volume; (2)
linear sequential arrays which would result in a two-dimensional
image in the shape of a rectangle or trapezoid, and a
three-dimensional volume in the shape of an angular portion of a
cylinder; and, (3) multi-row arrays. A motion control system is
provided to accurately control the array rotation, and to enable
more accurate reconstruction of 3D images from the 2D image planes.
The acoustic energy is coupled between the transducer array and the
imaging medium (patient) through an acoustic window. The acoustic
window comprises a section of the catheter wall and may comprise a
coupling fluid between the array and the catheter wall. The
catheter wall preferably has an acoustic impedance and sound
velocity similar to that of the body (1.5 MRayl), to minimize
reflections. The coupling fluid preferably has an acoustic
impedance similar to that of the body and low viscosity, to
minimize drag on the array and motor. Portions of the transducer
array may be cylindrical in cross-section (the ends of the array;
the sides and back; the entire array assembly) to keep the array
centered and rotating smoothly within the catheter and/or to
control the fluid flow and viscous drag between the array and the
catheter wall. The transducer itself may be made of a variety of
materials, including, but not limited to, PZT, micromachined
ultrasound transducers (MUTs), PVDF. In addition to the
transduction material, other components (acoustic matching layers;
acoustic absorber/backing; electrical interconnect; acoustic
focusing lens) may be included in the array assembly.
[0048] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. It is, therefore, to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the
invention.
* * * * *