US20070167821A1 - Rotatable transducer array for volumetric ultrasound - Google Patents

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.

Description

BACKGROUND
• 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.
• 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.
• 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.
• 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
• 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.
• 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
• 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:
• FIG. 1 is a block diagram of an exemplary ultrasound imaging and therapy system, in accordance with aspects of the present technique;
• FIG. 2 is a side and internal view of an exemplary embodiment of a rotating transducer array assembly for use in the imaging system ofFIG. 1;
• FIG. 3 is an illustration of components of a rotating transducer array that are applicable to embodiments of the present invention;
• FIG. 4 is another illustration of a catheter for use in the imaging system ofFIG. 1;
• FIG. 5 is an illustration of an interconnect assembly to which embodiments of the present invention are applicable;
• FIG. 6 is an illustration of an interconnect assembly to which embodiments of the present invention are applicable;
• FIG. 7 is an illustration of an interconnect assembly to which embodiments of the present invention are applicable;
• FIG. 8 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 9 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 10 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 11 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 12 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 13 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 14 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable;
• FIG. 15 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable; and,
• FIG. 16 is an illustration of an alternative embodiment of a motion controller to which embodiments of the present invention are applicable.
DETAILED DESCRIPTION
• 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.
• 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
• FIG. 1 is a block diagram of anexemplary system10 for use in imaging and providing therapy to one or more regions of interest in accordance with aspects of the present technique. Thesystem10 may be configured to acquire image data from apatient12 via acatheter14. 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 numeral16 is representative of a portion of thecatheter14 disposed inside the body of thepatient12.
• In certain embodiments, an imaging orientation of the imaging andtherapy catheter14 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 thecatheter14.Catheter14 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 toFIG. 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.
• In accordance with aspects of the present technique, thecatheter14 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 patient12 being imaged. Additionally, thecatheter14 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.
• Thesystem10 may also include amedical imaging system18 that is in operative association with thecatheter14 and configured to image one or more regions of interest. Theimaging system10 may also be configured to provide feedback for therapy delivered by the catheter or separate therapy device (not shown). Accordingly, in one embodiment, themedical imaging system18 may be configured to provide control signals to thecatheter14 to excite a therapy component of the imaging and therapy transducer and deliver therapy to the one or more regions of interest. In addition, themedical imaging system18 may be configured to acquire image data representative of the anatomical region of thepatient12 via thecatheter14. 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.
• As illustrated inFIG. 1, theimaging system18 may include adisplay area20 and auser interface area22. However, in certain embodiments, such as in a touch screen, thedisplay area20 and theuser interface area22 may overlap. Also, in some embodiments, thedisplay area20 and theuser interface area22 may include a common area. In accordance with aspects of the present technique, thedisplay area20 of themedical imaging system18 may be configured to display an image generated by themedical imaging system18 based on the image data acquired via thecatheter14. Additionally, thedisplay area20 may be configured to aid the user in defining and visualizing a user-defined therapy pathway. It should be noted that thedisplay area20 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 thedisplay area20 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.
• Further, theuser interface area22 of themedical imaging system18 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 thedisplay area20. 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 thedisplay area20.
• As depicted inFIG. 1, thesystem10 may include an optionalcatheter positioning system24 configured to reposition thecatheter14 within thepatient12 in response to input from the user. Moreover, thesystem10 may also include anoptional feedback system26 that is in operative association with thecatheter positioning system24 and themedical imaging system18. Thefeedback system26 may be configured to facilitate communication between thecatheter positioning system24 and themedical imaging system18.
• FIG. 2 is an illustration of an exemplary embodiment of a rotatingtransducer array assembly100 for use in the imaging system ofFIG. 1. As shown, thetransducer array assembly100 comprises atransducer array110, amicromotor120, which may be internal or external to the space-critical environment, adrive shaft130 or other mechanical connections betweenmotor controller140 and thetransducer array110. The assembly further includesinterconnect150, which will be described in greater detail with reference toFIG. 3. Theassembly100 further includes acatheter housing160 for enclosing thetransducer array110,micromotor120,interconnect150 and driveshaft130. In this embodiment, thetransducer array110 is mounted ondrive shaft130 and thetransducer array110 is rotatable with thedrive shaft130. Further in this embodiment, the rotation motion of thetransducer array110 is controlled bymotor controller140 andmicromotor120.Motor controller140 andmicromotor120 control the motion oftransducer array100 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 themicromotor120.Interconnect150 refers to, for example, cables and other connections coupled between thetransducer array110 and the imaging system shown inFIG. 1 for use in receiving/transmitting signals between the transducer and the imaging system. In an embodiment,interconnect150 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 toFIG. 3 below.Catheter housing160 is of a material, size and shape adaptable for internal imaging applications and insertion into regions of interest. The catheter further includes a fluid-filledacoustic window170 shown inFIG. 4. Fluid-filledacoustic window170 is provided to allow coupling of acoustic energy from the rotating transducer array to the region or medium of interest. In embodiments,catheter housing160 is acoustically transparent, e.g. low attenuation and scattering, acoustic impedance near that of blood and tissue (Z˜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˜1.5 M Rayl, V˜1540 m/sec).
• In an embodiment, the motor controller is external to the catheter housing as shown inFIG. 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.
• Referring toFIG. 3, an internal view of thecatheter assembly14 ofFIG. 1 is illustrated showing the internal components and arrangement oftransducer110 andinterconnect150. In an exemplary embodiment,transducer array110 is a 64-element 1D array having .110 mm azimuth pitch, 2.5 mm elevation and 6.5 MHz frequency. Acylindrical transducer assembly210 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 housing160 (shown inFIG. 2) for intracardiac applications such as ICE.Interconnect150 is coupled to thetransducer110 and comprises the necessary cables and conductors for transmitting image information between thetransducer110 and imaging system18 (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 ormore wires114 that may be used at the insertion end of the catheter and pass by thetransducer110 to the tip of the cathether and thesewires114 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 thecatheter14 ofFIG. 1, there is aflexible region116 of theinterconnect150. The length of theflexible region116 is desirably selected such that during rotation or oscillation oftransducer110 theconductors180 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 forinterconnect150 will be described with reference toFIG. 5-7.
• In an embodiment,transducer array110 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.
• Referring toFIG. 5-7, embodiments forinterconnect150 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,interconnect150 is configured to reduce the torque or drag force exerted by the interconnect against the rotation of the transducer and/or drive shaft. Referring toFIG. 5, in one embodiment, a section of the interconnect (conductors180) is coiled to reduce torque. Referring toFIG. 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 ofconductors190. During assembly of the catheter, this group ofloose conductors190 should be left slack, not taut, to further facilitate movement of the conductors relative to each other and rotation of thetransducer array110. Referring toFIG. 6, a section ofconductors200 and202 adjacent to theloose section190 may be left ribbonized as a ribbonized section, to facilitate termination of the conductors onribbonized section202 to thetransducer110 or to the transducer flex circuit(s) and the conductors onribbonized section200 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 toFIG. 7, arotating section202 of conductors terminated at thetransducer array110 may be constructed or modified to ease the torque requirements necessary for rotation. For example, the rotational stiffness may be reduced by cuttingslits230 into the ribbon or flex circuit and by making this section of the interconnect thinner relative to thenon-rotating section200 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 theinterconnect150. 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 theinterconnect150 under rotating conditions.
• Referring now toFIG. 8, an alternative embodiment for a rotating transducer array assembly comprises anexternal motor320 used to rotate thedrive shaft130 and anexternal motor controller330 for drivingmotor320. A rotary encoder orposition sensor340 provides feedback to compensate for any wind-up in the drive shaft. In this embodiment thedrive shaft130 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.
• Referring now toFIG. 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 themicromotor120 andmotor controller140 ofFIG. 2. Similar components common toFIG. 2 and subsequent figures will have the same reference numbers.
• Referring first toFIG. 9, an embodiment for the motion controller comprises anactuator400, which can be internal or external to the catheter, used to effect oscillation and/or rotation of the transducer array. Theactuator400 creates a linear motion of thedrive shaft130 which is converted to an oscillatory rotary motion. Asleeve410 is slidable overtransducer cylinder210 which enclosestransducer array110. Thesleeve410 includessmall pins420 which engage in spiral guide tracks430. In operation, as thesleeve420 moves along the length of the cylinder/encapsulation, the cylinder/encapsulation rotates a given amount determined by the spiral guide tracks430. The reciprocating linear motion of the sleeve creates an oscillatory motion of the cylinder/encapsulation housing thetransducer array110, allowing the transducer array to rotate and acquire a 3D pyramidal volume. The linear motion part that engages thespiral guide track430 may be partially constrained for one degree of freedom along the axis of the catheter. A rotary encoder orposition sensor340 may provide feedback to compensate for flexibilities in the system, e.g. the drive shaft, linear-rotary converter, and the like.
• Referring now toFIG. 10, another exemplary embodiment for the motion controller comprises an actuator, either external or internal (not shown), for driving acable440 for effecting rotation oftransducer array110.Cable440 is a beaded or studdedcable including beads450 placed along the length ofcable440 to engage inspiral guide track430. In one embodiment, asbead450 engages thespiral guide track430 and travels the length ofcylinder210 terminating atdrive pulley460, thecylinder210 rotates 90 degrees. After a quarter revolution, anotherbead450 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 thecylinder210 containing thetransducer array110 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 toFIG. 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 ofcylinder210. 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.
• Referring toFIG. 11-13, various alternative embodiments for motion control comprise cable and pulley systems for effecting oscillatory rotary motion of the transducer array. InFIG. 11,cables440 engage withdrive pulley460. An actuator (not shown) drives a cable andpulley460 in a fixed direction with a continuous motion. Attached to the drivepulley460, which is rotating, is an extension orflapper470 which impacts acatch480 attached to thetransducer array110 once per revolution. Theflapper470 forces the rotation of thearray cylinder210 along the long axis. Once theflapper470 clears thecatch480, thecylinder210 returns to a nominal position with the aid of atorsion spring490 and the velocity is limited by arotary vane damper500. By driving thepulley460 withflapper470 at a constant rate, thecylinder210 containing thetransducer array110 will undergo an oscillatory motion. Thus thetransducer array110 will oscillate such that the acquisition of a 3D pyramidal volume can be obtained. Thetorsion spring490 androtary vane damper500 may be adjusted for appropriate timing of the motion of thecylinder210. 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.
• Referring toFIG. 12 and13, alternative embodiments toFIG. 11 are provided wherein thecylinder210 further comprises agear interface510 to engage with a gear portion ofdrive pulley460. InFIG. 12, thepulley460 andcylinder housing210 are connected using a bevel gear interface or approximation thereof. InFIG. 13,pulley460 andcylinder210 are connected using a bevel gear interface andpulley460 further comprises two different gear sections, one on an upper section ofpulley460 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 thetransducer array110 in order to acquire a 3D pyramidal imaging volume.
• Referring now toFIG. 14-16, additional embodiments for the motion controller are provided. Referring toFIG. 14A, a side view shows one ormore actuators600 are attached to each side of thetransducer array110 at a first end and fixed to the catheter tube at the other end.Actuator control lines610 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 aboutpivot point620.Actuators600 may include electroactive polymers. Arotary encoder340 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 oftransducer110. InFIG. 14B, a first actuator A is fully activated and actuator B is fully deactivated. InFIG. 14B, actuator A is partially activated and actuator B is partially activated. InFIG. 14D, actuator A is fully deactivated and actuator B is fully activated.
• Referring toFIG. 15, a similar embodiment is shown but rather than using two actuators, oneactuator600 is provided and attached to thetransducer array110 at one end and aspring630 is attached at the other end and to thecatheter cylinder210. Movement of the actuator extends or contracts the spring as shown inFIG. 15A-C to effect rotation oftransducer array110. The actuator and/or spring may also be torsional, as well as linear.
• Referring toFIG. 16, a further embodiment for motion control is provided. In this embodiment, twobladders640 are in contact with thetransducer array110. 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 thetransducer110 aboutpivot point620. In this manner, a 3D volume may be acquired.
• 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.
• 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.

Claims (26)

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 ofclaim 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 ofclaim 1 further comprising a catheter housing for enclosing the rotating transducer assembly.

4. The rotating transducer array assembly ofclaim 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 ofclaim 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 ofclaim 5 wherein the motor controller is contained internal to the catheter housing.

7. The rotating transducer array assembly ofclaim 5 wherein the motor controller is external to the catheter housing.

8. The rotating transducer array assembly ofclaim 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 ofclaim 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 ofclaim 9 wherein the interconnect assembly comprises flexible cable that is de-ribbonized in the rotating portion.

11. The rotating transducer array assembly ofclaim 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 ofclaim 9 wherein the interconnect cable comprises slits in non-conducting portions of the flexible cable.

13. The rotating transducer array assembly ofclaim 1 wherein the transducer array comprises a one-dimensional (1D) transducer array.

14. The rotating transducer array assembly ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 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 ofclaim 20 wherein the transducer array is mounted on a drive shaft and the transducer array is rotatable with the drive shaft.

22. The method ofclaim 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 ofclaim 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 ofclaim 20 wherein the interconnect assembly is adapted to reduce rotational stiffness of at least a rotating portion of the interconnect assembly.

25. The method ofclaim 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 ofclaim 20 further comprising the step of delivering treatment to the selected regions of interest.

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