Rotatable transducer array for volumetric ultrasound
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.
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 DESCRIPTIONIn 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.
DRAWINGSThese 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:
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
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
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.
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.
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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.
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In an embodiment, the motor controller is external to the catheter housing as shown in
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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.
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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
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.
Type: Application
Filed: Nov 30, 2005
Publication Date: Jul 19, 2007
Inventors: Warren Lee (Clifton Park, NY), Douglas Wildes (Ballston Lake, NY), Abdulrahman Al-Khalidy (Niskayuna, NY), Weston Griffin (Guilderland, NY)
Application Number: 11/289,926
International Classification: A61B 8/14 (20060101);