Embodiments of the invention relate generally to a transducer assembly, and more specifically to a transducer assembly for real-time imaging in space-constrained applications.
Transducers, such as acoustic transducers, have found application in medical imaging where an acoustic probe is held against a patient and the probe transmits and receives ultrasound waves. The received energy may, in turn, facilitate the imaging of the internal tissues of the patient. For example, transducers may be employed to image the heart of a patient.
A typical invasive probe may include a miniaturized transducer assembly disposed at a distal end of the probe. The probe may include, for example, a one-dimensional phased array transducer. As will be appreciated, spatial resolution of the transducer assembly is an important factor in imaging applications, such as ultrasound imaging. Additionally, acquisition of high quality real-time three-dimensional imaging volumes in space-constrained applications is disadvantageously dependent upon the number of signal conductors that may be accommodated within the limited space of the probe. Also, the relatively small physical size of a transducer assembly sized and configured for space-constrained applications unfortunately limits the aperture of the transducer assembly. This results in the generation of ultrasound beams that diverge rapidly with distance, thereby resulting in poor spatial resolution and degraded image quality. Consequently, the ability of a clinician to identify anatomical and physiological regions of interest may be hampered.
Currently available imaging catheters, such as ultrasound imaging catheters, typically have a side-viewing orientation where the ultrasound beam direction is generally perpendicular to a long axis of the imaging catheter. Although forward-looking catheters have emerged, the apertures are small and fixed resulting in poor resolution and penetration. Also, previously conceived solutions have incorporated one-dimensional catheter transducers to obtain three-dimensional images by rotating the entire catheter. However, the resulting images are not obtained in real-time.
Furthermore, previously conceived solutions for real-time three-dimensional imaging employ two-dimensional arrays to steer and focus the ultrasound beam over a pyramidal-shaped volume. However, many of these two-dimensional arrays require a relatively large number of interconnections in order to adequately sample the acoustic aperture space, resulting in increased cost and complexity.
Briefly, in accordance with aspects of the invention, a transducer assembly is presented. The transducer assembly includes a support structure configured to be reversibly changed between a first position and a second position. Additionally, the transducer assembly includes a multi-dimensional transducer array comprising a plurality ‘N’ of one-dimensional sub-groups of transducer elements arranged on the support structure, wherein each of the ‘N’ sub-groups of transducer elements is disposed in a spatial relationship such that an angle formed between one of the ‘N’ sub-groups of transducer elements and at least one other sub-group of transducer elements is less than about 180 degrees, and wherein ‘N’ is an integer.
In accordance with further aspects of the technique, an invasive probe configured to image an anatomical region is presented. The invasive probe includes an outer envelope sized and configured to be disposed in the anatomical region. Further, the invasive probe includes a transducer assembly movably disposed in the outer envelope, where the transducer assembly includes a support structure configured to be reversibly changed between a first position and a second position, where the support structure includes a central guide member having a proximal end and a distal end, a plurality of support struts movably coupled to the distal end of the central guide member, and a sliding member coupled to the central guide member and the plurality of support struts to facilitate changing the support structure between the first position and the second position. The transducer assembly also includes a multi-dimensional transducer array comprising a plurality ‘N’ of sub-groups of transducer elements arranged on the support structure, wherein each of the ‘N’ sub-groups of transducer elements is disposed in a spatial relationship such that an angle formed between each of the ‘N’ sub-groups of transducer elements and at least one other sub-group of transducer elements is less than about 180 degrees, and wherein ‘N’ is an integer.
In accordance with yet another aspect of the present technique, a system is presented. The system includes an acquisition subsystem configured to acquire image data, where the acquisition subsystem comprises an invasive probe configured to image an anatomical region, where the invasive probe includes an outer envelope sized and configured to be disposed in the anatomical region, and a transducer assembly movably disposed in the outer envelope. Furthermore, the transducer assembly includes a support structure configured to be reversibly changed between a first position and a second position and a multi-dimensional transducer array comprising a plurality ‘N’ of sub-groups of transducer elements arranged on the support structure, wherein each of the ‘N’ sub-groups of transducer elements is disposed in a spatial relationship such that an angle formed between each of the ‘N’ sub-groups of transducer elements and at least one other sub-group of transducer elements is less than about 180 degrees, and wherein ‘N’ is an integer. The support structure in the transducer assembly includes a central guide member having a proximal end and a distal end, a plurality of support struts coupled to the distal end of the central guide member and a sliding member movably coupled to the central guide member and the plurality of support struts to facilitate changing the support structure between the first position and the second position. Additionally, the system includes a processing subsystem in operative association with the acquisition subsystem and configured to process the image data acquired via the acquisition subsystem.
In accordance with further aspects of the present technique, a method of using an invasive probe having a transducer assembly is presented. The method includes positioning the invasive probe proximate a region of interest within an anatomical region, wherein the transducer assembly is in a first position and disposed in an outer envelope of the invasive probe. The method also includes extending the transducer assembly from within the outer envelope such that the transducer assembly is positioned outside a distal end of the invasive probe. Further, the method includes deploying the transducer assembly to change the position of the transducer assembly from the first position to a second expanded position, where the transducer assembly includes a support structure configured to be reversibly changed between a first position and a second position and a multi-dimensional transducer array comprising a plurality ‘N’ of sub-groups of transducer elements arranged on the support structure, wherein each of the ‘N’ sub-groups of transducer elements is disposed in a spatial relationship such that an angle formed between each of the ‘N’ sub-groups of transducer elements and at least one other sub-group of transducer elements is less than about 180 degrees, and wherein ‘N’ is an integer.
In accordance with yet another aspect of the present technique, a method of using an invasive probe having a transducer assembly is presented. The method includes positioning the invasive probe proximate a region of interest within an anatomical region, where the transducer assembly is in a first position and disposed in an outer envelope of the invasive probe. Further, the method includes extending the transducer assembly from within the outer envelope such that the transducer assembly is positioned outside a distal end of the invasive probe. Additionally, the method includes imaging in a first retracted position. The method also includes transitioning the position of the transducer assembly from the first retracted position to a second expanded position to create an expanded acoustic aperture. Moreover, the method includes imaging in the second expanded position, where the transducer assembly includes a support structure configured to be reversibly changed between a first position and a second position and a multi-dimensional transducer array comprising a plurality ‘N’ of sub-groups of transducer elements arranged on the support structure, wherein each of the ‘N’ sub-groups of transducer elements is disposed in a spatial relationship such that an angle formed between each of the ‘N’ sub-groups of transducer elements and at least one other sub-group of transducer elements is less than about 180 degrees, and wherein ‘N’ is an integer.
These and other features, aspects, and advantages of the invention will become better understood when the following detailed description is read with reference to the accompanying drawings, which are provided for illustrative purposes and in which like characters represent like parts throughout the drawings, wherein:
As will be described below, embodiments of the present technique include a transducer assembly having a support structure and a multi-dimensional transducer array configured such that the transducer array may be reversibly transitioned from first radially collapsed position to a second radially expanded position.
Although the exemplary embodiments illustrated hereinafter are described in the context of a medical imaging system, such as an ultrasound imaging system, other imaging systems and applications such as industrial imaging systems and non-destructive evaluation and inspection systems, such as pipeline inspection systems, liquid reactor inspection systems are also contemplated. Additionally, the exemplary embodiments illustrated and described hereinafter may find application in multi-modality imaging systems that employ an ultrasound imaging in conjunction with other imaging modalities, position-tracking systems or other sensor systems.
In accordance with aspects of the present technique, the probe 14 may be configured to facilitate interventional procedures in which the probe 14 may be configured to function as an invasive probe. It should also be noted that, although the illustrated embodiments are described in the context of a catheter-based probe, other types of probes such as endoscopes, laparoscopes, surgical probes, transrectal probes, transvaginal probes, intracavity probes, probes adapted for interventional procedures, or combinations thereof are also contemplated in conjunction with the present technique. Reference numeral 16 is representative of a portion of the probe 14 disposed inside the patient 12.
Further, in the illustrated embodiment, an imaging system 18 is in operative association with the invasive probe 14. The imaging system 18 may be configured to display an image representative of a current position of the invasive probe 14 within a region of interest in the patient 12. The imaging system 18 may include a display 20 and a user interface 22. In accordance with aspects of the present technique, the display 20 of the imaging system 18 may be configured to display images generated by the imaging system 18 based on image data acquired via the invasive probe 14.
Turning now to
As illustrated, the invasive probe 28 generally includes a proximal end 29 and a distal end 31, and is shown as including an outer envelope 30. In one embodiment, the transducer assembly 26 is illustrated as being disposed within the outer envelope 30 of the invasive probe 28. Alternatively, in another embodiment, the transducer assembly 26 may be disposed at an end of the outer envelope 30 of the transducer assembly. In one embodiment, the transducer assembly 26 may be disposed at the distal end 31 of the outer envelope 30 of the invasive probe 28, for example. In accordance with aspects of the present technique, the transducer assembly 26 may include a support structure configured to be reversibly changed between at least a first position and a second position. Further, for the illustrated embodiment, the first position may include a radially collapsed position, while the second position may include a radially expanded position. Accordingly, the size of the expanded transducer array need not be limited by the catheter diameter. Moreover, in one embodiment, the size of the transducer array in the expanded position may be larger than catheter diameter as measured in at least two dimensions. In an embodiment where the expanded transducer array may be represented with a diameter, the diameter of the expanded transducer array may be larger than the catheter diameter as measured in a direction orthogonal to the axis of the catheter. In the first radially collapsed position, the transducer assembly 26 may be configured in a compact folded state having a form factor designed to fit within the outer envelope 30 for delivery to a region of interest. In one embodiment, the transducer assembly 26 may be configured to facilitate imaging in the radially collapsed position, the radially expanded position, or both.
The support structure may include a central guide member 34 that extends through the center of the transducer assembly 26 and is defined to include a proximal end 29 and a distal end 31 corresponding to that of the invasive probe 28. In one embodiment, the central guide member 34 may constructed from metals suitable for medical devices, such as stainless steel, nitinol, titanium, etc. Also, the central guide member 34 may include any of a variety of cross-sections including a circular cross-section, in certain embodiments. In such an embodiment, the central guide member 34 may have a diameter in a range from about 0.1 mm to 2 mm.
In one embodiment, a first end (for example, a distal end) of the support structure may be movably coupled to the central guide at or about the distal end 31 of the invasive probe 28 and a second end (for example, a proximal end) of the support structure may be movably coupled to an intermediate portion of the central guide member 34. In one embodiment the support structure includes multiple radial struts 36 coupled between the two ends of the support structure. The support structure may also include a sliding member 40 such as a slip ring and a hinge connection 42 coupled to the central guide member 34 as shown to facilitate transitioning the support structure between the collapsed and expanded positions. Reference numeral 46 is representative of a first direction of movement of the transducer assembly 26 whereas a subsequent direction of movement of the sliding member 40 along the central guide member 34 is indicated by reference numeral 44. In one embodiment, the radial struts 36 are movably coupled to the central guide member 34 via the sliding member 40 and hinge connection 42. Also, in accordance with one embodiment, at least one of the plurality of radial struts 36 may include a flexible circuit. The flexible circuit may include single or multi-layer copper circuit(s) on a polyimide substrate, in certain embodiments.
In certain embodiments, two or more transducer elements (not shown) may be arranged on the support structure to facilitate imaging of a region of interest. In one embodiment, one or more transducer elements may be disposed on each of the radial struts 36. Reference numeral 38 is representative of radial struts having two or more transducer elements disposed thereon. Furthermore, the transducer elements may be arranged on the radial struts in a pseudo-random pattern, a vernier pattern or other patterns to facilitate minimizing grating lobes and other beamforming artifacts. The transducer elements may include lead zirconate titanate (PZT) transducer elements, capacitively micromachined ultrasound transducer (cMUT) elements or polyvinylidene fluoride array (PVDF) transducer elements.
In a presently contemplated configuration, the transducer elements may be arranged on the radial struts 38 to form sub-groups of transducer elements. In one embodiment, the radial struts 38 may contain a number “N’ (where N is an integer value) of sub-groups of transducer elements. In one embodiment, a number ‘N’ of sub-groups of transducer elements may be arranged on the support structure such that an angle formed between one of the sub-groups of transducer elements on one radial strut and at least one other sub-group of transducer elements on another radial strut is less than about 180 degrees. In one embodiment, the angles of separation between each neighboring radial strut of the transducer assembly 26 may be substantially equivalent and may be determined according to the following relationship:
where the separation angle may be measured in degrees.
For example, in one embodiment the measure of an angle between each neighboring radial strut in a transducer assembly having 4 radial struts may be equal to about 90 degrees. In one embodiment, the support structure may also include spacers (not shown) coupled to the radial struts 36. As will be discussed in further detail below with reference to
According to further aspects of the present technique, the invasive probe 28 having a mechanically expanding transducer assembly, such as the transducer assembly 26, may be employed to facilitate imaging in space-constrained applications, such as, but not limited to, intracardiac echocardiography, transesophageal echocardiography, pediatric echocardiography, laparoscopic surgery. More particularly, the invasive probe 28 equipped with the transducer assembly 26 may be employed to obtain high quality RT3D image volumes.
The method of imaging employing the invasive probe 28 having the exemplary transducer assembly 26 may include positioning the invasive probe 28 proximate a region of interest within an anatomical region in the patient 12. The invasive probe 28 may be guided from the point of entry through the vasculature of the patient 12 to the desirable anatomical location employing a method such as fluoroscopy to monitor and guide the invasive probe 28 within the vasculature. The invasive probe could be delivered over a guide wire or through a sheath, where the sheath or wire had previously been guided to the desired location using e.g., fluoroscopic imaging. Once delivered to the region to be imaged, the transducer elements in the multi-dimensional transducer array may be energized and image data representative of the region of interest may be acquired. Image data may be acquired via the transducer assembly 26 while positioned within the outer envelope 30 of the invasive probe 28 (e.g., in a radially collapsed configuration) or while positioned outside of the outer envelope 30 (e.g., in the radially collapsed configuration or an expanded configuration). It may be noted that by employing the transducer assembly 26 in the radially collapsed position, multiple image planes may be acquired. For example, each “arm” of the transducer assembly 26 may be configured to operate independently to acquire a separate image plane.
As alluded to above, the transducer assembly 26 may be moved from within the outer envelope 30 such that the transducer assembly 26 is positioned outside the distal end 31 of the invasive probe 28 in order to image a region of interest. Reference numeral 48 is representative of the invasive probe 28 in which the transducer assembly 26 is positioned outside the distal end 31 of the invasive probe 28. In one embodiment, the transducer assembly 26 and the central guide member 34 may be extended out of the distal end 31.
Once the transducer assembly 26 has been positioned outside the distal end 31 of the invasive probe 28, the transducer assembly 26 may be transitioned from the first radially collapsed position to a second radially expanded position, in which the aperture of the transducer assembly 26 is not limited by the diameter of the catheter. Moreover, in one embodiment, the size of the transducer array in the expanded position may be larger than catheter diameter as measured in at least two dimensions. In an embodiment where the expanded transducer array may be represented with a diameter, the diameter of the expanded transducer array may be larger than the catheter diameter as measured in a direction orthogonal to the axis of the catheter. For example, the diameter of an intracardial catheter may be in the range of about 1 mm to 4 mm, while the aperture of the transducer assembly 26 in the second expanded position may be in a range from about 3 mm to 30 mm.
Reference numeral 52 is representative of the invasive probe 28 in which the transducer assembly 26 is depicted in an intermediate or partially deployed position that is between the radially collapsed position and the radially expanded position. Image data representative of the region of interest may also be acquired via the transducer assembly 26 in the partially deployed position. It may be noted that the transducer assembly 26 in the partially deployed position may be employed to obtain multiple image planes. For example, the arms of the transducer assembly 26 may be phased together depending upon the position of the arms during the intermediate position of deployment. Alternatively, the arms may act independently to acquire multiple image planes. In one embodiment, imaging of the entire forward hemisphere may be accomplished while the arms of the transducer assembly 26 are positioned at about 45 degrees as measured with respect to the catheter axis.
Deployment of the transducer assembly 26 to the radially expanded position may be achieved via the use of mechanical wires, in certain embodiments. Alternatively, shape memory material may be utilized to facilitate the deployment of the transducer assembly 26. Furthermore, hinges made using electro-actuated polymer actuators may also be employed to aid in transitioning the transducer assembly 26 from the radially collapsed position to the radially expanded position. In certain other embodiments, the transducer assembly 26 may be transitioned from the radially collapsed position to the intermediate or partially deployed position by retracting the hinge connection 42 with respect to the radial struts 36 in a direction represented by reference numeral 58 In other embodiments, the transducer assembly 26 may be transitioned to the intermediate or partially deployed position by extending the slip ring 40 over the central guide member 34 in a direction indicated by reference numeral 56, while maintaining the hinge connection 42 in a fixed location.
Reference numeral 60 is representative of the invasive probe 28 having the transducer assembly 26 in a full radially expanded position. As previously noted, the acoustic aperture of the transducer assembly 26 in the radially expanded position may be in a range from about 3 mm to 30 mm, however larger acoustic apertures are possible. It may be noted that the transducer assembly 26 in the radially expanded position may be configured to have a forward viewing orientation. Additionally, the transducer assembly 26 in the radially expanded position may be used to acquire image data representative of the region of interest. More particularly, image data may be acquired employing the transducer assembly 26 in the radially expanded position.
Once the image data is acquired via the transducer assembly 26 in the expanded configuration of 60, the transducer assembly 26 may be transitioned back to the radially collapsed position. The transducer assembly 26 may be transitioned to the radially collapsed position from the radially expanded position by moving the sliding member 40 in a second direction (opposite to direction 44) along the central guide member 34. In certain other embodiments, the transducer assembly 26 may be transitioned to a radially collapsed position through use of a pull wire (not shown) or active hinges (not shown).
The transducer assembly 26 in the radially collapsed position subsequently may be retracted such that the transducer assembly 26 is once again positioned within the outer envelope 30 of the invasive probe 28. The invasive probe 28 along with the transducer assembly 26 in the radially collapsed position may then be removed from the anatomy of the patient by a clinician, for example.
As will be appreciated, the respective positions of the plurality of transducer elements may experience a positional shift while the transducer assembly 26 is transitioned between the radially collapsed position and the radially expanded position. As such, it is desirable to determine precise locations (e.g., to within a fraction of a wavelength to allow for proper phasing) of the plurality of transducer elements in the transducer assembly 26 to facilitate generation of a high-quality image using image data acquired via the plurality of transducer elements. In certain embodiments, adaptive beamforming techniques may be used to compensate for the variations and/or positional shifts of the plurality of transducer elements. The acquired image data may then be utilized to generate an image for display on the display 20 (see
By implementing the transducer assembly 26 as described hereinabove, RT3D image volumes having relatively enhanced quality may be obtained employing the transducer assembly 26 in the radially expanded position. Additionally, the transducer assembly 26 described hereinabove may be configured to have an alternative compact structure such that the transducer assembly 26 in the radially collapsed position may be configured to fit within a space-constrained invasive probe 28. Consequently, high quality RT3D image volumes may be acquired using the large aperture transducer assembly 26 that may also be inserted and removed using a narrow probe configured for minimally invasive applications, such as, but not limited to, intracardiac echocardiography, transesophageal echocardiography, pediatric echocardiography, laparoscopic surgery.
Turning now to
As previously described with respect to the transducer assembly 26 of
Additionally, the transducer assembly 72 may include a plurality of support struts 76, in which the plurality of support struts has a respective proximal end and a distal end. In a presently contemplated configuration, the respective proximal ends of the plurality of support struts 76 may be coupled to the central guide member 74 at the distal end of the central guide member 74 as shown in
Furthermore, a plurality of transducer elements (not shown) may be disposed on the plurality of support struts 76. The transducer elements may be physically or electrically configured into sub groups of transducer elements that together form a multi-dimensional transducer array. In one embodiment, the support struts 76 may contain a number ‘N’ (where N is an integer value) of sub-groups of transducer elements. In one embodiment, a number ‘N’ of sub-groups of transducer elements may be arranged on the support structure such that an angle formed between one of the sub-groups of transducer elements on one support strut and at least one other sub-group of transducer elements on another support strut is less than about 180 degrees.
A method of imaging employing the invasive probe 28 having the exemplary transducer assembly 72 may include positioning the invasive probe 28 at a region of interest within an anatomical region, as previously described with reference to
Reference numeral 84 is indicative of the invasive probe 28 where the transducer assembly 72 is configured in the radially expanded position. As previously noted, the transducer assembly 72 may be transitioned to the radially expanded position to create an acoustic aperture that is larger than the diameter of the catheter. Image data representative of the region of interest may be acquired via the transducer assembly 72 in the radially expanded position. Furthermore, as previously described with reference to
Following acquisition of image data using the transducer assembly 72 in the radially expanded position, the transducer assembly 72 may subsequently be retracted into the outer envelope 30 of the invasive probe 28. In one embodiment, retraction of the transducer assembly 72 in the radially expanded position into the outer envelope 30 of the invasive probe 28 urges the support struts 76 together causing the transducer assembly 72 to transition to the radially collapsed position.
Moreover, adaptive beamforming techniques may be employed to compensate for positional shifts and/or variations of the plurality of transducer elements, as previously described with reference to
In the mechanically expanding transducer assembly depicted in
Advantages of using spacers, including circumferential struts, include more accurate and reproducible positioning of the radial struts to reduce phasing errors, or requirement to use adaptive imaging to compensate for positional variations. Additionally, if the spacers support transducer elements, they help fill-in the aperture and thereby improve the image quality (e.g., penetration & contrast).
Referring now to
As described hereinabove, the invasive probe 28 equipped with the various configurations of the mechanically expanding transducer assembly such as the configurations illustrated in
In addition to facilitating imaging of a region of interest, the invasive probe 28 having the mechanically expanding transducer assembly 26/72 may also be employed to facilitate delivery of therapy to one or more regions of interest in an anatomical region. As previously described, the invasive probe 28 may be positioned in the region of interest prior to imaging and/or delivery of therapy. In certain embodiments, placement of the invasive probe 28 within the anatomy may be performed under fluoroscopic guidance.
In accordance with aspects of the present technique, the invasive probe 28 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 (see
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, or biopsy forceps for example. Additionally, as used herein, “delivering” may include various means of 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.
In one embodiment, the imaging system, such as the imaging system 18 (see
By implementing the invasive probe 28 having a mechanically expanding transducer assembly such as the transducer assembly 26 or the transducer assembly 72 and the therapy component 142 as described hereinabove, the therapy component 142 is generally in alignment with the imaged volume 134, thereby allowing clinicians to efficiently guide and place the therapy component 142 at a desired location with enhanced ease.
The various embodiments of the mechanically expanding transducer assemblies and the invasive probes having the mechanically expanding transducer assemblies configured to image and provide therapy and method of imaging and providing therapy described hereinabove dramatically enhance efficiency of the process of imaging and delivering therapy, by integrating the imaging and therapy mapping aspects of the procedure. Employing the transducer assembly described hereinabove allows acquisition of high quality RT3D images from within a space-constrained environment, such as the invasive probe. In addition, the unfolding of the transducer assemblies to obtain a relatively large acoustic aperture facilitates generation of images with relatively higher spatial resolution as compared to those images generated by transducer assemblies having relatively small acoustic apertures. Additionally, the forward viewing configuration of the transducer assembly integrated with diagnostic and/or therapeutic tools advantageously result in enhanced visualization of regions of interest, and simplified interventional procedures.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.