Imaging and therapy device for mechanical line ablation

Abstract

An ultrasound-based surgical system is provided for image-guided and mechanical ablation for minimally invasive surgery, particularly surgery requiring removal of tissue. The system includes a device having an elongated body portion supporting a therapeutic ultrasound transducer assembly including a piezoelectric composite material and an annular electrode array. The electrodes may be driven to generate focused ultrasound pulses for ablating tissue via cavitation. The device may be controlled to scan focused ultrasound pulses within an elongated axial region for performing linear ablation. An electrical isolation layer is formed over the ring electrode array to prevent arcing within the backing when a high voltage electrical pulse is delivered to the ring electrode array to generate an ultrasonic pulse for cavitation. The elongated body may support an imaging transducer assembly within a central aperture of the therapeutic ultrasound transducer assembly to facilitate image guidance during an ablation procedure.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202480065385.1 (22) Application Date 2024.09.13 (30) Priority Data 63 / 538,163 2023.09.13 US (85) PCT International Application Entering National Phase Date 2026.04.10 (86) PCT International Application Application Data PCT / CA2024 / 051224 2024.09.13 (87) PCT International Application Publication Data WO2025 / 054735 EN 2025.03.20 (71) Applicant: Daxon Sonic Ultrasonic Company Address: Canada (72) Inventors: M.G. Malley, J.A. Brown (74) Patent Agency: Beijing Zhucheng Law Firm 11313 Patent Attorneys Li Wenying and Wang Mo (51) Int.Cl. A61B 17 / 32 (2006.01) A61B 8 / 00 (2006.01) A61B 8 / 12 (2006.01) A61B 17 / 22 (2006.01) A61N 7 / 00 (2006.01) (54) Title of Invention Imaging and Therapeutic Device for Mechanical Linear Ablation (57) Abstract An ultrasound-based surgical system is provided for image-guided and mechanical ablation for minimally invasive surgery, particularly for procedures requiring tissue removal. The system includes a device having an elongated body portion that supports a therapeutic ultrasound transducer assembly comprising a piezoelectric composite material and an array of ring electrodes. The electrodes can be driven to generate focused ultrasound pulses for ablation of tissue via cavitation. The device can be controlled to scan the focused ultrasound pulses within the elongated axial region for performing linear ablation. An electrical isolation layer is formed above the annular electrode array to prevent arcing within the backing when a high-voltage electrical pulse is delivered to the annular electrode array to generate an ultrasonic pulse for cavitation. An elongated body can support an imaging transducer assembly within the central aperture of the therapeutic ultrasound transducer assembly to facilitate image guidance during ablation procedures. Claims 4 pages, Description 20 pages, Drawings 25 pages, CN 122028860 A 2026.05.12 CN 1 22 02 88 60 A 1. A therapeutic ultrasound system for performing tissue ablation via cavitation, the therapeutic ultrasound system comprising: a therapeutic ultrasound transducer assembly, the therapeutic ultrasound transducer assembly comprising: a piezoelectric composite layer having a proximal surface and a distal surface; an annular electrode array disposed on the proximal surface of the piezoelectric composite layer; a common electrode disposed on the distal surface of the piezoelectric composite layer;An electrical isolation layer disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer; an elongated body wherein the therapeutic ultrasound transducer assembly is supported at a position remote from the proximal end of the elongated body; An electrical signal transmission assembly disposed along at least a portion of the elongated body, wherein the electrical signal transmission assembly is operatively connected to the therapeutic ultrasound transducer assembly such that the electrodes of the annular electrode array are electrically connected to corresponding electrical channels of the electrical signal transmission assembly, and the common electrode is electrically connected to a common electrical channel of the electrical signal transmission assembly; and a control and processing circuit operatively coupled to the therapeutic ultrasound transducer assembly via the electrical signal transmission assembly, the control and processing circuit being configured to generate electrical pulses transmitted via the electrical signal transmission assembly to the annular electrode array for generating focused ultrasound pulses suitable for generating cavitation in water; and wherein the thickness of the electrical insulating layer is less than the wavelength of the focused ultrasound pulse within the electrical insulating layer; and wherein the thickness of the electrical insulating layer and the dielectric breakdown strength of the electrical insulating layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within the backing of the therapeutic ultrasound transducer assembly during the generation of the focused ultrasound pulse for cavitation. 2. The therapeutic ultrasound system of claim 1, wherein the piezoelectric composite layer is configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least one pair of adjacent electrodes of the annular electrode array, and wherein an electrically insulating material forming the electrically insulating layer is located within each annular slit. 3. The therapeutic ultrasound system of claim 2, wherein at least one annular slit extends from the proximal surface into the distal surface. 4. The therapeutic ultrasound system of claim 2, wherein each annular slit extends from the proximal surface into the distal surface. 5. The therapeutic ultrasound system of claim 2, wherein at least one annular slit is a partial slit extending from the proximal surface into the piezoelectric composite layer but not into the distal surface. 6. The therapeutic ultrasound system of claim 2, wherein each annular slit is a partial slit extending from the proximal surface into the piezoelectric composite layer but not into the distal surface. 7. The therapeutic ultrasound system of claim 5 or 6, wherein the partial slit has a depth between 5% and 95% of the thickness of the piezoelectric composite layer. 8. The therapeutic ultrasound system of claim 5 or 6, wherein the partial slit has a depth between 5% and 90% of the thickness of the piezoelectric composite layer. 9. The therapeutic ultrasound system of claim 5 or 6, wherein the partial slit has a depth between 5% and 75% of the thickness of the piezoelectric composite layer.10. The therapeutic ultrasound system according to claim 5 or 6, wherein the partial slit has a depth between 50% and 95% of the thickness of the piezoelectric composite layer. 11. The therapeutic ultrasound system according to claim 5 or 6, wherein the partial slit has a depth between 50% and 90% of the thickness of the piezoelectric composite layer. 12. The therapeutic ultrasound system according to claim 5 or 6, wherein the partial slit has a depth between 50% and 75% of the thickness of the piezoelectric composite layer. 13. The therapeutic ultrasound system according to any one of claims 2 to 12, wherein the thickness of the electrical isolation layer located on each electrode of the annular electrode array exceeds the width of the annular slit. 14. The therapeutic ultrasound system of any one of claims 2 to 13, wherein the piezoelectric composite layer comprises an array of piezoelectric pillars embedded in a substrate, the piezoelectric pillars extending from the proximal surface to the distal surface, and wherein the piezoelectric pillars are arranged in a segmented annular array, the segmented annular array comprising a plurality of concentric piezoelectric pillar arrays, such that each electrode of the annular electrode array is electrically actuated by one or more radially extending piezoelectric pillar arrays, and such that each annular slit is aligned with and extends into an annular substrate region located between a corresponding pair of radially adjacent concentric piezoelectric pillar arrays. 15. The therapeutic ultrasound system of any one of claims 1 to 14, wherein the electrically insulating layer has a dielectric breakdown strength between 10 kV / mm and 280 kV / mm. 16. The therapeutic ultrasound system of any one of claims 1 to 15, wherein the therapeutic ultrasound transducer assembly is an air-backed type. 17. The therapeutic ultrasound system of any one of claims 1 to 15, wherein the therapeutic ultrasound transducer assembly comprises a backing layer embedded with microballoons. 18. The therapeutic ultrasound system of any one of claims 1 to 17, wherein the annular electrode array is defined such that the lateral electrode spacing is between 20 micrometers and 80 micrometers. 19. The therapeutic ultrasound system of any one of claims 1 to 17, wherein the outer diameter of the annular electrode array is between 10 mm and 25 mm, and wherein the number of electrodes forming the annular electrode array is between 8 and 64. 20. The therapeutic ultrasound system of claim 1, wherein the piezoelectric composite layer comprises an array of piezoelectric pillars embedded in a substrate, the piezoelectric pillars extending from the proximal surface to the distal surface, and wherein the piezoelectric pillars are arranged in a segmented annular array, the segmented annular array comprising a plurality of concentric piezoelectric pillar arrays, such that each electrode of the annular electrode array is electrically actuated by one or more radially continuing piezoelectric pillar arrays, and such that the spacing between each annular electrode is such that...The annular substrate regions located between corresponding pairs of radially adjacent concentric piezoelectric column arrays are aligned. 21. The therapeutic ultrasound system according to any one of claims 1 to 20, wherein the electrical signal transmission component is operatively connected to the therapeutic ultrasound transducer component via a plurality of wire bonds. 22. The therapeutic ultrasound system according to claim 21, wherein each wire bond electrically connects a corresponding electrode of the annular electrode array to a corresponding conductive channel of the electrical signal transmission component via an aperture formed in the electrical isolation layer. 23. The therapeutic ultrasound system according to any one of claims 1 to 20, wherein the common electrode is electrically connected to the electrical signal transmission component via a grounding ring extending along at least a portion of the outer peripheral edge of the piezoelectric composite layer. 24. The therapeutic ultrasound system according to any one of claims 1 to 20, wherein the electrical signal transmission component comprises a flexible printed circuit board. 25. The therapeutic ultrasound system of claim 24, wherein the flexible printed circuit board is operatively connected to the therapeutic ultrasound transducer assembly via a direct bond from the distal region of the flexible printed circuit board to the therapeutic ultrasound transducer assembly through an aperture formed in the electrical isolation layer. 26. The therapeutic ultrasound system of any one of claims 1 to 25, wherein the thickness of the electrical isolation layer is equal to one-quarter of the wavelength of the focused ultrasound pulse within the electrical isolation layer. 27. The therapeutic ultrasound system of any one of claims 1 to 25, wherein the thickness of the electrical isolation layer is equal to half the wavelength of the focused ultrasound pulse within the electrical isolation layer. 28. The therapeutic ultrasound system of any one of claims 1 to 27, wherein the therapeutic ultrasound transducer assembly further comprises a fixed acoustic lens. 29. The therapeutic ultrasound system of claim 28, wherein the fixed acoustic lens has an f-number between 0.5 and 3. 30. The therapeutic ultrasound system of any one of claims 1 to 29, wherein the control and processing circuitry is configured to control the therapeutic ultrasound transducer assembly to scan the focused ultrasound pulse in an elongated axial region, the elongated axial region being located in a distal direction from the distal energy emitting surface of the therapeutic ultrasound transducer assembly. 31. The therapeutic ultrasound system of claim 30, wherein the control and processing circuitry is configured to unidirectionally scan the focused ultrasound pulse within the elongated axial region. 32. The therapeutic ultrasound system of claim 30 or 31, wherein the control and processing circuitry is configured to scan the focused ultrasound pulse at a scan rate between 0.3 m / s and 1.3 m / s.33. The therapeutic ultrasound system of any one of claims 30 to 32, further comprising an imaging transducer assembly supported by the elongated body such that a distal surface of the imaging transducer assembly lies within a central aperture defined within the therapeutic ultrasound transducer assembly, and wherein the control and processing circuitry is operatively coupled to the imaging transducer assembly via the electrical signal transmission assembly; and wherein the control and processing circuitry is configured to control the imaging transducer assembly to acquire and process ultrasound image data to generate one or more ultrasound images representing an imaging region spatially overlapping with the elongated axial region. 34. The therapeutic ultrasound system of claim 33, wherein the control and processing circuitry is further configured to control the therapeutic ultrasound transducer assembly and the imaging transducer assembly such that scanning of the focused ultrasound pulse to perform linear ablation is initiated only after cavitation in the ultrasound image is detected. 35. The therapeutic ultrasound system of claim 33 or 34, wherein the control and processing circuitry is further configured to control the therapeutic ultrasound transducer assembly and the imaging transducer assembly such that the collection of ultrasound image data by the imaging transducer assembly is interleaved with the transmission of the focused ultrasound pulse. 36. The therapeutic ultrasound system of claim 35, wherein the control and processing circuitry is configured such that the ultrasound image data collected between successively generated focused ultrasound pulses represents a subset of complete image frames of a B-mode image. 37. The therapeutic ultrasound system of claim 36, wherein the control and processing circuitry is configured to acquire ultrasound image data corresponding to a selected subset of complete B-mode image frames before and after the generation of a given focused ultrasound pulse, thereby obtaining first ultrasound image data and second ultrasound image data characterizing the selected subset of complete B-mode image frames, and wherein the control and processing circuitry is configured to process the first ultrasound image data and the second ultrasound image data to generate a differential image characterizing time variations within the selected subset of complete B-mode image frames. Claims 3 / 4, page 4, CN 122028860, A 38. The therapeutic ultrasound system of claim 37, wherein the control and processing circuitry is configured to display the complete B-mode image frame and annotate the complete B-mode image frame based on the differential image. 39. The therapeutic ultrasound system of any one of claims 33 to 38, wherein the central aperture has a segmented shape resulting in the inner electrodes of the annular electrode array, and wherein the segmented portions of the inner electrodes are electrically connected to facilitate actuation of the segmented portions via a single channel of the electrical signal transmission component.40. A method of performing tissue ablation via cavitation, the method comprising: acoustically contacting a distal energy-emitting surface of a therapeutic ultrasound transducer assembly with tissue, the therapeutic ultrasound transducer assembly comprising: a piezoelectric composite layer having a proximal surface and a distal surface; an annular electrode array disposed on the proximal surface of the piezoelectric composite layer; a common electrode disposed on the distal surface of the piezoelectric composite layer; an electrical isolation layer disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer; and generating an electrical pulse and transmitting the electrical pulse to the annular electrode array to generate a focused ultrasound pulse suitable for generating cavitation in a subsurface focused region; wherein the thickness of the electrical isolation layer is less than the wavelength of the focused ultrasound pulse within the electrical isolation layer; and wherein the thickness of the electrical isolation layer and the dielectric breakdown strength of the electrical isolation layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within a backing of the therapeutic ultrasound transducer assembly during the generation of the focused ultrasound pulse for cavitation. 41. The method of claim 40, further comprising controlling the delay between the electrical pulses delivered to the annular electrode array such that the subsurface focusing region is scanned to perform linear ablation on the tissue. 42. A therapeutic ultrasound device for performing tissue ablation via cavitation, the therapeutic ultrasound device comprising: a therapeutic ultrasound transducer assembly, the therapeutic ultrasound transducer assembly comprising: a piezoelectric composite layer having a proximal surface and a distal surface; an annular electrode array disposed on the proximal surface of the piezoelectric composite layer; a common electrode disposed on the distal surface of the piezoelectric composite layer; an electrical isolation layer disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer; an elongated body, wherein the therapeutic ultrasound transducer assembly is supported at a proximal end remote from the elongated body; wherein the piezoelectric composite layer is configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least a pair of adjacent electrodes of the annular electrode array, and wherein an electrical isolation material forming the electrical isolation layer is located within each annular slit. 43. The therapeutic ultrasound device according to claim 42, wherein at least one annular slit is a partial slit extending from the proximal surface into the piezoelectric composite layer but not extending to the distal surface. Claims 4 / 4 Page 5 CN 122028860 A Imaging and Treatment Device for Mechanical Linear Ablation

[0001] Cross-Reference to Related Applications

[0002] This application claims the application filed on September 13, 2023, entitled "IMAGING AND THERAPY DEVICE"Priority is given to U.S. Provisional Patent Application No. 63 / 538,163, entitled "Imaging and Therapeutic Device for Mechanical Line Ablation," the entire contents of which are incorporated herein by reference. Background Art

[0003] This disclosure relates to therapeutic ultrasound. More particularly, this disclosure relates to devices for performing tissue ablation via histotripsy.

[0004] Numerous tools are specifically designed for minimally invasive surgery, exhibiting varying sizes and tissue removal mechanisms. These tools include more conventional excision tools such as micro-cutters, micro-forceps, and micro-grasping forceps. These can be adopted by using the shape specifications of endoscopes or laparoscopes. There are also many instruments based on endoscopic thermal ablation, which use various techniques to remove tumor tissue through high-temperature damage, including RF ablation, microwave ablation, focused ultrasound ablation, or laser ablation, as well as cryoablation using liquefied gas to enhance the efficacy of RF ablation. Currently, almost all endoscopic ablation tools are thermal ablation type, which has the disadvantage of substantially damaging adjacent tissue outside the treatment area and leaving scar tissue in situ within the ablation zone.

[0005] One of the few examples of non-thermal endoscopic ablation tools is the ultrasonic surgical aspirator, which acts as a miniature vibrating saw. While these instruments effectively ablate tissue without heating, they lack precision at the target ablation site. However, the most significant shortcoming of these conventional endoscopic ablation tools is the contact between the ablation zone and the tip of the endoscope. This means that when ablating superficial lesions directly beneath the surface of the skin (or tongue), an open wound must be created to access the lesion, leading to complications such as bleeding and infection.

[0006] While cavitation is known to be used for tissue ablation, recent techniques in ultrasound cavitation-based ablation (tissue fragmentation) involve very large transducers designed to ablate tissue from a distance. This means that the transducers are required to be large in size and operate at low frequencies.

[0007] Recently, there has been some work on developing smaller, higher-frequency endoscopic tissue fragmentation transducers with higher precision. These have been developed for minimally invasive and small-aperture procedures. However, these devices are based on using unit-piece piezoelectric transducers with a passive fixed-focus acoustic lens applied in front to passively focus the ultrasound beam (e.g., J. K. Woodacre and J. Brown, “TRANSDUCER ASSEMBLY FOR GENERATING FOCUSED ULTRASOUND”, US 2020 / 0346044 A1, 2020; T. G. Landry et al., “Endoscopic CoregisteredUltrasound Imaging and Precision Histotripsy: Initial In Vivo Evaluation, BME Front., 2022, doi: 10.34133 / 2022 / 9794321; and Maxwell, R. Hsi, T. Lendvay, P. Casale and M. Bailey, “FOCUSED ULTRASOUND APPARATUS AND METHODS OF USE”, US 2016 / 0287909 A1, 2016.

[0008] A disadvantage of this type of lens-based design is that acoustic coupling to the tissue can be difficult due to the strong curvature of the fixed-focus lens, as the area between the curved lens surface and the tissue to be ablated needs to be completely filled with coupling material. Another disadvantage of this type of lens-based histotripsy endoscope is that the ablation zone is limited by the fixed focus of the lens. Due to the specification 1 / 20 pages 6 CN 122028860 A Increasing the ablation zone requires relatively slow mechanical translation of the transducer, which may limit the ablation rate. Summary of the Invention

[0009] An ultrasound-based surgical system is provided for image-guided and mechanical ablation for minimally invasive surgery, particularly for procedures requiring tissue removal. The system includes a device having an elongated body portion that supports a therapeutic ultrasound transducer assembly comprising a piezoelectric composite material and an array of annular electrodes. The electrodes can be driven to generate focused ultrasound pulses for ablation of tissue via cavitation. The device can be controlled to scan the focused ultrasound pulses within an elongated axial region for performing linear ablation. An electrical isolation layer is formed above the annular electrode array to prevent arcing within the backing when high-voltage electrical pulses are delivered to the annular electrode array to generate ultrasound pulses for cavitation. The elongated body can support an imaging transducer assembly within a central aperture of the therapeutic ultrasound transducer assembly to facilitate image guidance during ablation procedures.

[0010] Accordingly, in a first aspect, a therapeutic ultrasound system for performing tissue ablation via cavitation is provided. The therapeutic ultrasound system includes:

[0011] a therapeutic ultrasound transducer assembly, the therapeutic ultrasound transducer assembly including:

[0012] a piezoelectric composite layer having a proximal surface and a distal surface;

[0013] a ring electrode array disposed on the proximal surface of the piezoelectric composite layer;

[0014] a common electrode disposed on the distal surface of the piezoelectric composite layer;

[0015] an electrical isolation layer disposed on the ring electrode array on the proximal surface of the piezoelectric composite layer;

[0016] An elongated body, wherein a therapeutic ultrasound transducer assembly is supported at a proximal end remote from the elongated body;

[0017] an electrical signal transmission assembly disposed along at least a portion of the elongated body, wherein the electrical signal transmission assembly is operatively connected to the therapeutic ultrasound transducer assembly such that electrodes of the annular electrode array are electrically connected to corresponding electrical channels of the electrical signal transmission assembly, and a common electrode is electrically connected to a common electrical channel of the electrical signal transmission assembly; and

[0018] a control and processing circuit operatively coupled to the therapeutic ultrasound transducer assembly via the electrical signal transmission assembly, the control and processing circuit being configured to generate electrical pulses, the electrical pulses being transmitted via the electrical signal transmission assembly to the annular electrode array for generating focused ultrasound pulses suitable for generating cavitation in water; and

[0019] wherein the thickness of the electrical insulating layer is less than the wavelength of the focused ultrasound pulse within the electrical insulating layer; and

[0020] The thickness of the electrical isolation layer and the dielectric breakdown strength of the electrical isolation layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within the backing of the therapeutic ultrasound transducer assembly during the generation of the focused ultrasound pulse for cavitation.

[0021] In some example embodiments of the system, the piezoelectric composite layer is configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least one pair of adjacent electrodes of the annular electrode array, and wherein an electrically insulating material forming the electrical isolation layer is located within each annular slit.

[0022] In some example embodiments of the system, at least one annular slit extends from the proximal surface to the distal surface. Each annular slit may extend from the proximal surface to the distal surface. At least one annular slit may be a partial slit extending from the proximal surface into the piezoelectric composite layer but not into the distal surface. Each annular slit may be a partial slit extending from the proximal surface into the piezoelectric composite layer but not into the distal surface. The partial slit may have a depth between 5% and 95% of the thickness of the piezoelectric composite layer. The partial slit may have a depth between 5% and 90% of the thickness of the piezoelectric composite layer. The partial slit may have a depth between 5% and 75% of the thickness of the piezoelectric composite layer. The partial slit may have a depth between 50% and 95% of the thickness of the piezoelectric composite layer. The partial slit may have a depth between 50% and 90% of the thickness of the piezoelectric composite layer.

[0023] In some example embodiments of the system, the thickness of the electrically insulating layer on each electrode of the annular electrode array exceeds the width of the annular slit.

[0024] In some example embodiments of the system, the piezoelectric composite layer includes an array of piezoelectric pillars embedded in a substrate.The piezoelectric pillars extend from the proximal surface to the distal surface, and wherein the piezoelectric pillars are arranged in a segmented annular array, the segmented annular array comprising a plurality of concentric piezoelectric pillar arrays, such that each electrode of the annular electrode array is electrically actuated by one or more radially continuing piezoelectric pillar arrays, and such that each annular slit is aligned with and extends into an annular matrix region located between a corresponding pair of radially adjacent concentric piezoelectric pillar arrays.

[0025] In some example embodiments of the system, the electrically insulating layer has a dielectric breakdown strength between 10 kV / mm and 280 kV / mm.

[0026] In some example embodiments of the system, the therapeutic ultrasound transducer assembly is an air-backed type.

[0027] In some example embodiments of the system, the therapeutic ultrasound transducer assembly includes a backing layer embedded with microballoons.

[0028] In some example embodiments of the system, the annular electrode array is defined such that the lateral electrode spacing is between 20 micrometers and 80 micrometers.

[0029] In some example embodiments of the system, the outer diameter of the annular electrode array is between 10 mm and 25 mm, and the number of electrodes forming the annular electrode array is between 8 and 64.

[0030] In some example embodiments of the system, the piezoelectric composite layer includes an array of piezoelectric pillars embedded in a substrate, the piezoelectric pillars extending from a proximal surface to a distal surface, and wherein the piezoelectric pillars are arranged in a segmented annular array, the segmented annular array comprising a plurality of concentric piezoelectric pillar arrays, such that each electrode of the annular electrode array is electrically actuated by one or more radially continuing piezoelectric pillar arrays, and such that each annular electrode gap is aligned with an annular substrate region located between a corresponding pair of radially adjacent concentric piezoelectric pillar arrays.

[0031] In some example embodiments of the system, the electrical signal transmission component is operatively connected to the therapeutic ultrasound transducer component via a plurality of wire bonds. Each wire bond can electrically connect a corresponding electrode of the annular electrode array to a corresponding conductive channel of the electrical signal transmission component via an aperture formed in an electrically insulating layer.

[0032] In some example embodiments of the system, the common electrode is electrically connected to the electrical signal transmission assembly via a grounding ring extending along at least a portion of the outer periphery of the piezoelectric composite layer towards the edge.

[0033] In some example embodiments of the system, the electrical signal transmission assembly includes a flexible printed circuit board. The flexible printed circuit board can be operatively connected to the therapeutic ultrasound transducer assembly via a direct bonding of a distal region of the flexible printed circuit board to the therapeutic ultrasound transducer assembly through an aperture formed in the electrical isolation layer.

[0034] In some example embodiments of the system, the thickness of the electrical isolation layer is equal to one-quarter of the wavelength of the focused ultrasound pulse within the electrical isolation layer.

[0035] In some example embodiments of the system, the thickness of the electrical isolation layer is equal to half the wavelength of the focused ultrasound pulse within the electrical isolation layer.

[0036] In some example embodiments of the system, the therapeutic ultrasound transducer assembly further includes a fixed acoustic lens.

[0037] In some example embodiments of the system, the fixed acoustic lens has an f-number between 0.5 and 3.

[0038] In some example embodiments of the system, the control and processing circuitry is configured to control the therapeutic ultrasound transducer assembly to scan focused ultrasound pulses in an elongated axial region located in a direction distal to the distal energy emitting surface of the therapeutic ultrasound transducer assembly specification (page 3 / 20, CN 122028860 A). The control and processing circuitry may be configured to scan focused ultrasound pulses unidirectionally within the elongated axial region. The control and processing circuitry may be configured to scan focused ultrasound pulses at a scan rate between 0.3 m / s and 1.3 m / s.

[0039] In some example embodiments, the system further includes an imaging transducer assembly supported by an elongated body, such that the distal surface of the imaging transducer assembly lies within a central aperture defined within a therapeutic ultrasound transducer assembly, and wherein control and processing circuitry is operatively coupled to the imaging transducer assembly via an electrical signal transmission assembly, wherein the control and processing circuitry is configured to control the imaging transducer assembly to acquire and process ultrasound image data to generate one or more ultrasound images characterizing an imaging region spatially overlapping with the elongated axial region.

[0040] In some example embodiments of the system, the control and processing circuitry is further configured to control the therapeutic ultrasound transducer assembly and the imaging transducer assembly such that scanning of focused ultrasound pulses to perform linear ablation is initiated only after cavitation in the ultrasound image is detected. The control and processing circuitry may be further configured to control the therapeutic ultrasound transducer assembly and the imaging transducer assembly such that the acquisition of ultrasound image data by the imaging transducer assembly and the transmission of focused ultrasound pulses are interleaved.

[0041] In some example embodiments of the system, the control and processing circuitry is configured such that ultrasound image data collected between successively generated focused ultrasound pulses represents a subset of complete image frames of a mode B image. The control and processing circuitry may be configured to acquire ultrasound image data corresponding to a selected subset of complete mode B image frames before and after the generation of a given focused ultrasound pulse, thereby obtaining first and second ultrasound image data characterizing the selected subset of complete mode B image frames, wherein the control and processing circuitry is configured to process the first and second ultrasound image data to generate a differential image characterizing the time variation within the selected subset of complete mode B image frames. The control and processing circuitry may be configured to display complete mode B image frames and annotate the complete mode B image frames based on the differential image.

[0042] In some example implementations of the system, the central aperture has a shape that results in the segmentation of the inner electrodes of the annular electrode array, and wherein the segmented portions of the inner electrodes are electrically connected so as to actuate the segmented portions via a single channel of the electrical signal transmission component.

[0043] In another aspect, a method for performing tissue ablation via cavitation is provided, the method comprising:

[0044] acoustically contacting a distal energy emitting surface of a therapeutic ultrasound transducer assembly with tissue, the therapeutic ultrasound transducer assembly comprising:

[0045] a piezoelectric composite layer having a proximal surface and a distal surface;

[0046] a ring electrode array disposed on the proximal surface of the piezoelectric composite layer;

[0047] a common electrode disposed on the distal surface of the piezoelectric composite layer;

[0048] an electrical isolation layer disposed on the ring electrode array on the proximal surface of the piezoelectric composite layer; and

[0049] generating an electrical pulse and transmitting the electrical pulse to the ring electrode array to generate a focused ultrasound pulse suitable for generating cavitation in a subsurface focusing region;

[0050] wherein the thickness of the electrical isolation layer is less than the wavelength of the focused ultrasound pulse within the electrical isolation layer; and

[0051] The thickness of the electrical isolation layer and the dielectric breakdown strength of the electrical isolation layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within the backing of the therapeutic ultrasound transducer assembly during the generation of focused ultrasound pulses for cavitation.

[0052] In some example embodiments, the method further includes controlling the delay between electrical pulses delivered to the annular electrode array, such that the subsurface focused region is scanned to perform linear ablation on the tissue.

[0053] In another aspect, a therapeutic ultrasound device for performing tissue ablation via cavitation is provided, the therapeutic ultrasound device comprising:

[0054] a therapeutic ultrasound transducer assembly comprising:

[0055] a piezoelectric composite layer having a proximal surface and a distal surface;

[0056] an annular electrode array disposed on the proximal surface of the piezoelectric composite layer;

[0057] a common electrode disposed on the distal surface of the piezoelectric composite layer;

[0058] an electrical isolation layer disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer;

[0059] an elongated body, wherein the therapeutic ultrasound transducer assembly is supported at a position proximal to the elongated body;

[0060] The piezoelectric composite layer is configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least one pair of adjacent electrodes of the annular electrode array, and wherein an electrically insulating material forming an electrically insulating layer is located within each annular slit.

[0061] In some example embodiments of the device, at least one annular slit is a partial slit extending from the proximal surface into the piezoelectric composite layer but not to the distal surface.

[0062] A further understanding of the functional and advantageous aspects of this disclosure can be achieved by referring to the following detailed description and drawings. Brief Description of the Drawings

[0063] Various embodiments are described with reference to the accompanying drawings. In the drawings, the same reference numerals may indicate the same or functionally similar elements.

[0064] FIG1A shows a non-limiting example embodiment of an imaging and treatment device for performing tissue ablation via cavitation.

[0065] FIG1B shows a cross-sectional view of the example embodiment in FIG1A to highlight internal details.

[0066] FIG1C shows a cross-sectional view of the example embodiment in FIG1A, showing a representative ultrasound image field of view and treatment area of ​​the treatment transducer.

[0067] FIG1D shows an example of a piezoelectric composite layer slit to define an annular electrode array.

[0068] FIG2A illustrates the conditions for dielectric breakdown through a low-density backing when no electrical isolation layer is applied.

[0069] Figure 2B illustrates how an electrically insulating layer applied between the piezoelectric composite substrate and the low-density backing can prevent dielectric breakdown in the backing.

[0070] Figure 2C shows a 2D cross-section of a therapeutic ultrasound transducer assembly with only the electrodes etched.

[0071] Figure 2D shows a 2D cross-section of a therapeutic ultrasound transducer assembly with shallow partial slits.

[0072] Figure 2E shows a 2D cross-section of a therapeutic ultrasound transducer assembly with deep partial slits.

[0073] Figure 2F shows a 2D cross-section of a therapeutic ultrasound transducer assembly with the composite material fully slit.

[0074] Figure 3A illustrates the fabrication of an example therapeutic ultrasound transducer assembly, showing an isometric cross-sectional view of the annular piezoelectric composite material before the electrodes are applied.

[0075] Figure 3B illustrates the fabrication of an example therapeutic ultrasound transducer assembly, showing the device of Figure 3A with electrodes on the top and bottom surfaces.

[0076] Figure 3C illustrates the fabrication of an example therapeutic ultrasound transducer assembly, showing the device of Figure 3B with partial slits made in the composite material to define the array elements. Specification 5 / 20 pages 10 CN 122028860 A

[0077] Figure 3D illustrates the fabrication of an example therapeutic ultrasound transducer assembly, showing the device of Figure 3C after the application of an insulating layer, wherein the strip region is retained in a shielding manner to allow electrical connection with the array elements.

[0078] Figure 3E illustrates the fabrication of an example therapeutic ultrasound transducer assembly, showing the device of Figure 3D after the application of a low-density backing layer on the electrical insulating layer.

[0079] Figure 3F illustrates the fabrication of an example therapeutic ultrasound transducer assembly, showing the device on the bottom surface of a piezoelectric composite material.The device in FIG3E after the application of the acoustic matching layer.

[0080] FIG4A shows an example cut-filled type 1-3 piezoelectric composite substrate.

[0081] FIG4B shows the example composite material from FIG4A after partial slits are made to define the array elements.

[0082] FIG4C shows a piezoelectric column for an example type 1-3 piezoelectric composite substrate with radially defined columns.

[0083] FIG4D shows an example type 1-3 piezoelectric composite substrate with radially defined columns but without filler material.

[0084] FIG4E shows an example type 1-3 piezoelectric composite substrate with radially defined columns after partial slits are made to define the array elements.

[0085] FIG5 shows an example system for performing tissue ablation via cavitation.

[0086] FIG6A is a block diagram of an imaging and treatment system.

[0087] FIG6B is a block diagram of a therapeutic electronics system forming part of a treatment system.

[0088] FIG7A is a photograph showing a pulse generator connected to a cable bundle.

[0089] Figure 7B is a voltage versus time graph showing the pulses from a single channel during operation.

[0090] Figure 7C shows a typical delay distribution for the entire 16-element array.

[0091] Figure 8 shows a bubble cloud tested in a tissue phantom, where individual ablation regions are compared to gridded ablation (far right).

[0092] Figure 9 shows a non-limiting example embodiment of the imaging and treatment device form factor.

[0093] Figure 10 is a representative image obtained in vivo during treatment (left) and after tissue ablation (right), with arrows indicating lines of mechanically ablated tissue.

[0094] Figures 11A, 11B, 11C, and 11D illustrate the steps involved in manufacturing a first example method of interconnecting the treatment array to an interposer PCB.

[0095] Figures 12A, 12B, 12C, 12D, and 12E illustrate the steps involved in manufacturing a second example method of interconnecting the treatment array to an interposer PCB.

[0096] Figure 13A shows an example embodiment where the four inner elements are discontinuous around a central square hole.

[0097] Figure 13B shows a first example method of electrically connecting four sections of the disconnected elements.

[0098] Figure 13C shows a second example method of electrically connecting four sections of the disconnected elements.

[0099] Figure 14 shows a series of photographs of the manufactured design, showing a) the array and interconnects mounted coplanarly to each other, b) the electrical connection between the array elements and exposed pads on the interconnects, c) the connection protected by potting epoxy, d) an enlarged view of the electrical connection, and e) an enlarged view of the PCB section used to reassemble the elements disconnected due to the hole for the imaging array.

[0100] Figure 15 is a photograph of a side-view treatment array where the imaging array is centered.

[0101] Figure 16 shows the radial composite material before (left) and after (right) electrode patterning. Detailed Description

[0102] Various embodiments and aspects of this disclosure will be described with reference to the details discussed below. The following description and drawings are illustrative of this disclosure and should not be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of this disclosure. However, in some instances, well-known or conventional details are not described for the sake of a concise discussion of embodiments of this disclosure.

[0103] As used herein, the terms “comprises” and “comprising” should be interpreted as inclusive and open-ended, not exclusive. Specifically, when used in the specification and claims, the term “comprises” and variations thereof mean to include the specified features, steps, or components. These terms should not be construed as excluding the presence of other features, steps, or components.

[0104] As used herein, the term “exemplary” means “serving as an example, instance, or illustration” and should not be construed as being preferred or advantageous relative to other configurations disclosed herein.

[0105] As used herein, the terms “about” and “approximately” mean variations that may exist within the upper and lower limits of the range of values, such as variations in properties, parameters, and dimensions. Unless otherwise specified, the terms “about” and “approximately” mean plus or minus 25% or less.

[0106] It should be understood that, unless otherwise specified, any specified range or group is a shorthand way of referring individually to each member of the range or group, and each possible subrange or subgroup covered therein, and the same applies to any subrange or subgroup therein. Unless otherwise specified, this disclosure relates to and explicitly includes combinations of each specific member and subrange or subgroup.

[0107] As used herein, the term “on the order of” when used in conjunction with a quantity or parameter means a range spanning approximately one-tenth to ten times the stated quantity or parameter.

[0108] Unless otherwise defined, all technical and scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art. Unless otherwise indicated (e.g., by context), the following terms are intended to have the following meanings as used herein:

[0109] This disclosure provides a tool capable of performing image-guided and mechanical ablation during minimally invasive surgery, particularly surgery requiring tissue removal. Non-contact, non-thermal endoscopic linear ablation procedures can be performed using the systems, devices, and methods disclosed herein, with the advantage of providing imaging feedback to monitor treatment and target the treated lesion. Unlike conventional and known ultrasound-based tissue ablation devices, the embodiments described herein enable form factors favorable to minimally invasive procedures.Invasive, depth-adjustable mechanical ablation combined with real-time, co-registered (co-aligned) ultrasound image-guided ablation.

[0110] Referring now to FIG1A, an example therapeutic ultrasound device 100 for performing linear ablation via ultrasound-induced cavitation is shown. The example device includes a therapeutic ultrasound transducer assembly 200 housing an array of annular ultrasound transducers capable of generating focused ultrasound pulses. An elongated body 120 supports the therapeutic ultrasound transducer assembly 200 at a location proximal to a point 121 remote from the elongated body 120. The therapeutic ultrasound transducer assembly 200 may be supported relative to the elongated body 120 such that the distal functional axis (e.g., the ultrasound beam delivery axis) associated with the therapeutic ultrasound transducer assembly 200 is angled relative to the longitudinal axis (or rigidly or via a flexible tip) of the elongated body 120, for example, to facilitate placement and access to the target tissue.

[0111] As shown, the elongated body 120 may have a narrow cross-section that expands in the distal region to accommodate the radial range of the therapeutic ultrasound transducer assembly 200. In some example embodiments, the body portion may serve as a handle (e.g., a pinch handle) manually supported and positioned by a user, or alternatively supported and manipulated by a user-controlled, autonomous, or semi-autonomous robotic positioning system.

[0112] Furthermore, in some example embodiments, such as the example embodiment illustrated in FIG1A, the device 100 also includes a centrally located imaging transducer assembly 300, which facilitates imaging during, for example, tissue ablation procedures to provide image guidance that facilitates image-based monitoring and / or feedback. Accordingly, the device includes a set of annular ultrasound elements (therapeutic array) capable of performing mechanical ablation within a certain depth of focus, as described on page 7 / 20 of the specification 12 CN 122028860 A, and a second set of ultrasound elements (imaging array) configured for high-frequency, high-resolution ultrasound imaging.

[0113] Although not shown in FIG. 1A, an electrical signal transmission component (such as a printed circuit board or one or more cables) is disposed along or within at least a portion of the elongated body 120, and is operatively connected to the therapeutic ultrasound transducer assembly 200 (and the imaging transducer assembly 300, if included). A proximal portion of the electrical signal transmission component is connected to or may be connected to control and processing circuitry for transmitting electrical pulses to the therapeutic ultrasound transducer assembly 200 and optionally controlling the imaging transducer assembly 300 to acquire ultrasound image data.

[0114] FIG. 1B shows a detailed isometric view of the distal region of the device, including the therapeutic ultrasound transducer assembly 200, shown in cross-section cut through a central longitudinal plane. The therapeutic ultrasound transducer assembly 200 includes piezoelectric complexes.The composite layer (e.g., a disk) 210, in this example embodiment, is also shown having a backing layer 215 and a matching layer 220, with the external energy emitting surface shown at 225. As shown, the elongated body 120 may also include a centrally located elongated support 122 for the imaging transducer assembly 300. The region 124 between the elongated body 120, the centrally located elongated support 122, and the lateral portion of the imaging transducer assembly 300 may be filled with a material such as epoxy resin or a rigid gasket. The imaging transducer assembly 300 may be axially aligned with the therapeutic ultrasound transducer assembly and fixed in place with epoxy resin, or compressed into the space formed by the aperture and housing in the therapeutic array.

[0115] It will be understood that the backing material 215 may be a solid backing material, or in some example embodiments, it may be air or an inert gas. In some example embodiments, the backing material is made of a low acoustic impedance material. The low acoustic impedance material is, for example, epoxy resin incorporating low-density fillers (microballoons). The epoxy resin incorporating low-density filler provides rigidity to the device and enables a very thin profile. The thickness of the backing layer can be on the order of millimeters and does not require a housing like an air-backed array.

[0116] FIG1B illustrates an example embodiment in which an interconnecting ring 230 at least partially surrounds the outer portion of the piezoelectric composite layer 210 in the circumferential direction. The interconnecting ring 230 facilitates a common (grounded) connection between a common electrical path within the electrical signal transmission assembly and a common electrode located on the distal surface of the piezoelectric composite layer 210, and facilitates ease of manufacture of the device. The interconnecting ring may include features for mounting and sealing into a housing of the device. This example embodiment illustrates one or more possible embodiments that form an electrical connection with the common electrode of the therapeutic ultrasound transducer assembly 200, and other example embodiments will be described in further detail below.

[0117] As illustrated in the figure, the therapeutic ultrasound transducer assembly 200 is circular and has a square aperture 235 at the center to accommodate the imaging transducer assembly 300. However, it will be understood that the shapes illustrated in the figures are merely illustrative and not limiting. For example, the therapeutic ultrasound transducer assembly 200 and its annular element need not have a circular shape (e.g., an elliptical shape may be used in an alternative), and the aperture 235 (and the shape of the imaging transducer assembly 300) can take various shapes other than square, including, for example, rectangular, circular, and elliptical.

[0118] FIG1C schematically illustrates the spatial co-registration and spatial overlap between a two-dimensional image slice 320 obtained from the central imaging transducer assembly 300 and the elongated axial region 240 where the scanned focused ultrasound pulse of the therapeutic ultrasound transducer assembly 200 is located. The elongated axial region 240 corresponding to the therapeutic transducer treatment area represents the area where treatment can be guided electronically.The transducer focus achieves cavitation and ablation in the tissue region, as will be described in further detail below. In some example embodiments, the elongated axial region 240 shares axial symmetry with the therapeutic ultrasound transducer assembly 200.

[0119] The imaging transducer assembly 300 may be a 1D, 1.5D, 2D, or annular imaging transducer, provided that its imaging volume spatially overlaps with the elongated axial region 240 associated with the treatment performed by the therapeutic ultrasound transducer assembly 200. An example embodiment of a suitable imaging ultrasound assembly for integration into a device is described in U.S. Patent No. 10,149,660, page 8 / 20, 13 CN 122028860 A, the entire contents of which are incorporated herein by reference.

[0120] Figure 1D illustrates an example embodiment of an annular piezoelectric array formed of a piezoelectric composite material located within the therapeutic ultrasound transducer assembly 200. The figure illustrates a piezoelectric composite layer 210, in which a ring electrode array 260 is disposed on a first surface of the piezoelectric composite layer 210, the electrodes 260 being formed of a metal layer 250. A common electrode 255 is disposed on a second surface of the piezoelectric composite layer 210. The ring piezoelectric array is integrated into a therapeutic ultrasound transducer assembly 200 such that the first surface where the ring electrode array 260 is located is the proximal surface (facing the proximal portion of the device), and the second surface where the common electrode 255 is located is the distal surface, which faces the tissue region to be ablated during use. The figure also illustrates an example where the central aperture 235 is circular.

[0121] In the example annular piezoelectric array shown in FIG. 1D, the annular electrodes are shown as being separated by slits 270 extending from the proximal surface of the piezoelectric composite layer 210 toward the distal surface of the piezoelectric composite layer 210 (e.g., as further described below, during manufacturing, the piezoelectric composite elements can be separated by slits that pass through the top electrode and partially or completely through the piezoelectric composite layer / substrate). The inventors have found that including slits 270 can be beneficial in improving the mechanical isolation of the piezoelectric composite material located below the annular electrodes. As explained in further detail below, the slit configuration shown in FIG. 1D is not intended to be limiting, and in other example embodiments, the piezoelectric composite layer 210 may be without slits, may include one or more partial slits, and / or may include one or more full slits extending from the proximal surface of the piezoelectric composite layer 210 to the distal surface. In some example embodiments, the slit width may be between 5% and 15% of the thickness of the piezoelectric composite material. When slit, the volume fraction of the piezoelectric composite material can, for example, range from 30% to 90%.

[0122] While the annular piezoelectric array shown in FIG. 1D is advantageous for providing a compact configuration with a flat surface facing the distal side, the inventors incorporated such a structure into a therapeutic ultrasound transducer assembly 200 and operated the device to perform the assembly.Significant challenges have been encountered in tissue fragmentation for achieving tissue ablation. It has been found that a very high potential difference is typically created between adjacent electrodes, especially when the voltage pulses delivered to adjacent annular electrodes are out of phase, due to the high-voltage pulses applied to adjacent electrodes of the annular electrode array to generate focused ultrasound pulses. This is due to the high pulse voltage required to generate the acoustic pressure needed for cavitation, and the relatively large delay between elements required to focus to a low f-number, resulting in a high voltage difference between adjacent electrodes during the pulse. This can lead to arcing between adjacent electrodes when the electric field within the backing exceeds the dielectric breakdown strength of the backing material (e.g., a solid material or a gas, such as air in the case of an air backing).

[0123] In practice, more than eight elements are typically used to achieve the cavitation threshold when using an annular piezoelectric composite array for focusing. When the array is divided into rings of annular elements (e.g., by the presence of annular electrodes), the elements gradually narrow towards the edges to maintain equal element areas. Narrow elements impede the option of widening the slits to prevent arcing between elements. For example, in an example device with a 15 mm diameter annular array and 16 elements, the outer element is only 120 μm when a 60 μm slit is used between the elements. The electrical breakdown in air (or epoxy resin incorporating microballoons) is 3 kV / mm, thus limiting the drive voltage to 180 V, which is insufficient to achieve mechanical cavitation.

[0124] This problem is illustrated in Figure 2A, which shows a cross-sectional view through the piezoelectric composite layer 210 and the application of a voltage relative to the common electrode 250 to two adjacent annular electrodes 260A and 260B, resulting in a high inter-electrode voltage ΔV between the adjacent annular electrodes 260A and 260B. When the electric field resulting in the backing 215 exceeds the dielectric breakdown strength of the backing in the region 280 near the two adjacent electrodes 260A and 260B, dielectric breakdown (arc) 285 occurs between the electrodes, which may cause array damage. Furthermore, if the piezoelectric composite layer 210 includes a slit 270, an electric arc may also occur across the slit, especially if the slit is filled with air or a material or gas with a low dielectric breakdown strength. This problem is exacerbated for miniaturized device designs, as it is desirable to have the electrode spacing and / or slit gap as small as possible to achieve a high volume fill factor in the piezoelectric composite layer 210. Specification 9 / 20 pages 14 CN 122028860 A

[0125] In order to mitigate or avoid dielectric breakdown and arcing problems in the backing, the inventors realized that this problem can be solved by including a thin layer of electrically insulating material. The electrically insulating layer is provided with a thickness that reduces the penetration of the electric field into the backing, such that the electric field in the backing region near the electrode is lower than the dielectric breakdown strength of the backing. Moreover, the electrically insulating layer is composed of a material withA material with sufficiently high dielectric breakdown strength is formed to avoid dielectric breakdown within the insulating material. In some example embodiments, the electrical isolation layer may be epoxy resin, which increases the dielectric breakdown by a factor of 6.6 kV / mm to 20 kV / mm.

[0126] In some example embodiments, the electrical isolation layer has a subwavelength thickness to avoid or reduce the impact on the acoustic performance of the device. Moreover, in some example embodiments, the electrical isolation layer may have a quarter-wavelength thickness or a half-wavelength thickness, depending on the wavelength of the ultrasonic pulse within the electrical isolation layer.

[0127] In some example embodiments, the electrical isolation layer has a dielectric strength of 20 kV / mm, 10 kV / mm to 225 kV / mm (e.g., parylene C), 10 kV / mm to 280 kV / mm (e.g., including parylene N), and may be formed of parylene.

[0128] As illustrated in FIG2B, the inclusion of the electrical isolation layer 290 prevents dielectric breakdown because the thickness of the electrical isolation layer 290 reduces the strength of the electric field penetrating into the backing region 280, and because the high dielectric breakdown strength of the electrical isolation layer 290 prevents dielectric breakdown in the electrical isolation layer 290. Moreover, in an example embodiment involving the slit 270, as illustrated in FIG2B, the electrically insulating material forming the electrical isolation layer 290 extends into and substantially fills the slit 270, and during the application of an electrical pulse to the device for generating an ultrasonic pulse sufficient to cause cavitation, the high dielectric breakdown strength of the electrically insulating material forming the electrical isolation layer 290 prevents dielectric breakdown in the slit 270.

[0129] Accordingly, in various example embodiments of this disclosure, a therapeutic ultrasound device configured to perform linear ablation via ultrasound-induced cavitation includes a therapeutic ultrasound transducer assembly that houses a ring-shaped ultrasound transducer array based on a piezoelectric composite material. The annular ultrasound transducer array is formed by the following structure: a piezoelectric composite layer having a proximal surface and a distal surface; an annular electrode array disposed on the proximal surface; a common electrode disposed on the distal surface of the piezoelectric composite layer; and an electrically insulating layer disposed on the annular electrode array on the proximal surface. The thickness and dielectric breakdown strength of the electrically insulating layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within the backing of the therapeutic ultrasound transducer assembly during the generation of focused ultrasound pulses for performing cavitation in water (or, for example, in tissues such as tumor tissue, adipose tissue, or soft tissue lesions). The thickness of the electrically insulating layer may also be less than the wavelength of the focused ultrasound pulse within the electrically insulating layer. The insulating layer can be configured to prevent arcing when a -20 MPa peak negative pressure is generated at the focal point in water using the therapeutic ultrasound transducer assembly to achieve shock scattering tissue fragmentation (>3 cycles), where the peak positive pressure is typically greater than 80 MPa.

[0130] In some example embodiments, the piezoelectric composite layer can be configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least one pair of adjacent electrodes of the annular electrode array. An electrically insulating material forming an electrical isolation layer extends into and is located within each annular slit, thereby preventing arcing within the slit during the generation of a focused ultrasound pulse sufficient to induce cavitation.

[0131] Figures 2C through 2F illustrate various example embodiments of a therapeutic ultrasound transducer assembly 200 in which an electrically insulating layer 290 is incorporated into the device structure to prevent dielectric breakdown in the backing 215 when a focused ultrasound pulse for cavitation is generated; each figure shows a cross-sectional view. These figures also show a matching layer 295 defined on a common electrode 250. Figure 2C illustrates an example embodiment in which electrodes 260 of the annular electrode array are defined on the proximal surface of the piezoelectric composite layer 210, with no slit between adjacent electrodes. For example, in such an example embodiment, electrodes 260 may be defined on the proximal surface by photolithography. An electrically insulating layer 290 formed above electrode 260 prevents dielectric breakdown in backing 215.

[0132] FIG2D illustrates an alternative example embodiment in which electrodes 260 of the annular electrode array are defined on the proximal surface of piezoelectric composite layer 210, and shallow slits are defined between adjacent electrodes, wherein the material forming the electrically insulating layer 290 extends into the slits. FIG2E illustrates an alternative example embodiment in which electrodes 260 of the annular electrode array are defined on the proximal surface of piezoelectric composite layer 210, and deep slits are defined between adjacent electrodes, each slit extending almost from the proximal surface to the distal surface of piezoelectric composite layer 210. The material forming the electrically insulating layer 290 extends into the slits.

[0133] FIG2F illustrates another alternative example embodiment in which electrodes 260 of the annular electrode array are defined on the proximal surface of the piezoelectric composite layer 210, and a complete slit is defined between adjacent electrodes, each slit extending completely through the piezoelectric composite layer 210 from the proximal surface to the distal surface. As shown in FIG2E, the material forming the electrically insulating layer 290 extends into the slits.

[0134] In some embodiments, the distal portion of the therapeutic ultrasound transducer assembly 200 may include an acoustic lens. The lens provides a focal point at a fixed depth, and the phase delay distribution applied to the element is selected to bring the focal depth closer to the energy emission surface of the therapeutic ultrasound transducer assembly 200. In some example embodiments, the lens is made of metal. In some embodiments, the lens is integrated with a grounding ring as a whole, featuring a thickness that controls the bonding layer thickness between the lens and the therapeutic array. In some embodiments, the lens has an f-number between 0.5 and 3.

[0135] Referring now to Figures 3A through 3F, an example method for manufacturing a therapeutic ultrasound transducer assembly 200 is illustrated. In Figure 3A, a piezoelectric composite layer 210 disk is provided (the figure shows half of the disk in a cross-section taken along the midline). In Figure 3B, an electrode 260A (which will be processed into annular electrodes) is deposited on the proximal surface of the piezoelectric composite layer 210, and a common electrode 250 is deposited on the distal surface. The electrodes can be deposited, for example, by evaporation, sputtering, or other thin-film deposition techniques. The electrode material is a conductive metal, such as copper, aluminum, gold, silver, chromium, tin, or a combination thereof. The electrode thickness is generally between 0.25 μm and 5 μm.

[0136] As shown in Figure 3C, a set of annular slits 270 are cut into the electrode 260A and a first portion of the piezoelectric composite layer 210, such that the slits extend partially toward the distal surface of the piezoelectric composite layer 210. This set of annular electrodes 260 is fabricated by slitting the electrode 260A. As described above, in the example embodiment, the kerf is just deep enough (e.g., ≤5 μm) to remove electrode 260A for segmenting electrode 260A into ring electrodes 260, while in other embodiments, the partial kerf extends partially through the piezoelectric composite layer 210 but not to the distal surface to reduce mechanical coupling of the element and improve the element's directivity (≤90% of the total thickness). The method of partially kerfing the piezoelectric composite layer 210 from the proximal surface provides a significant advantage in keeping the electrodes on the distal surface of the therapeutic transducer intact, which simplifies electrical connections to the common (front, distal) electrodes.

[0137] In one example embodiment, where the element defines a partial kerf and the composite material is not kerfed, the patterning process can be performed by photolithography. In a positive photolithography process, a mask is created by exposing the photoresist to UV light in the area to be removed (kerf) of the electrode, which allows the photoresist to be dissolved by a developer. The electrode in the area exposed by the photoresist mask is then removed using an etchant.

[0138] In another example embodiment, the slits can extend from the proximal side of the piezoelectric composite layer 210 all the way to the distal side. This can be achieved, for example, by the example manufacturing methods described below. The slits can be formed according to various processes, including but not limited to laser micromachining and photolithography. In other example embodiments where no slits are present, the annular electrode array 260 can be formed via photolithography. In laser micromachining, short-duration, high-power laser pulses are used to precisely remove material (e.g., electrodes, ceramics, epoxy resins) with minimal local heating or damage.

[0139] In FIG. 3D, an electrically insulating layer 290 is formed on the proximal surface of the piezoelectric composite layer 210 and above the annular electrode 260, such that the material forming the electrically insulating layer 290 extends into each slit, thereby filling the slits and avoiding or reducing the cavitation within the slits and the backing (not yet covered) when electrical pulses are delivered to the annular electrode to generate focused ultrasound pulses suitable for achieving cavitation within the tissue.The possibility of dielectric breakdown occurring within the enclosure. By providing an aperture (window) 292 within the electrical isolation layer 290, a portion of each bottom ring electrode 260 can be electrically connected, thereby enabling the formation of an electrical connection between the ring electrode 260 and the conductive channel within the electrical signal transmission assembly (page 11 / 20 of the specification, 16 CN 122028860 A), which connects the therapeutic ultrasound transducer assembly 200 to external drive and beamforming electronics. For example, a small portion of the ring array can be retained by shielding, allowing the array electrodes to be electrically connected by methods such as ultrasonic wire bonding. After the electrical connection is completed, the electrical isolation layer can be applied to this portion to complete the electrode coverage.

[0140] In FIG. 3E, a backing 215 is optionally added proximally, above the electrical isolation layer 290, and above the distal portion of the electrical signal transmission assembly that is electrically connected to the ring electrode 260. Optionally, the device can be an air-backed type (or backed with an inert gas), as shown in FIG. 3D. As noted above, the backing 215 can be a low-density backing layer formed of a low acoustic impedance material (e.g., acoustic impedance in the range of 428 Rayls to 2 MRayls), such as epoxy resin incorporating low-density fillers (e.g., microballoons), which provides rigidity to the device and enables very thin profiles. The solid backing layer 215 can have a thickness of 0.5 mm to 10 mm and does not require a shell as in the case of an air-backed configuration.

[0141] Figure 3F shows an acoustic impedance matching layer 295 included on the distal surface of the therapeutic ultrasound transducer assembly 200, which faces the tissue and enhances the coupling of focused ultrasound pulses.

[0142] Figure 4A shows a segment of a piezoelectric composite material 210 disk. The piezoelectric composite material consists of ceramics (e.g., pillars or rods) embedded in an epoxy resin matrix. The composite material is designed to reduce the acoustic impedance of the material to more closely match the tissue and improve electromechanical efficiency. In the example embodiment shown in Figure 4A, a conventional 1-3 type composite structure is used, wherein slits are cut into the ceramic in the x and y directions. This creates a grid of 350 square ceramic pillars with a rectangular prism (cube) geometry. The pillars are embedded in an epoxy resin (e.g., Epotek 301) filler material. The selected ceramic material can be a hard piezoelectric ceramic (e.g., PZT-5A) or a soft piezoelectric ceramic (e.g., PZT-5H), an electrostrictive ceramic (e.g., PMN38), or a specialized ceramic developed for therapeutic applications (e.g., PZ54). Tissue fragmentation uses a low duty cycle (<1%) and low time-averaged power, so ceramic loss is not a critical parameter. Therefore, a wide variety of ceramic materials are suitable and will have the corresponding driving voltage required to reach the cavitation threshold.

[0143] The composite structure has the added benefit of providing some mechanical separation between the elements defined by the annular electrodes. However, this mechanical separation is incomplete if the elongated linear channels of the epoxy matrix (see 355 in FIG. 4A) are not spatially aligned with the gaps between the electrodes of the annular array to be formed over the piezoelectric composite layer 210 during manufacturing.

[0144] In embodiments where the substrate is a solid, low acoustic impedance ceramic (e.g., PZ39 or PZ37), a degree of mechanical isolation can be achieved simply by slits. For example, FIG. 4B shows the piezoelectric composite 210 from FIG. 4A, where partial slits 270 are cut into the material. As described above, these partial slits are filled with an electrically insulating material during manufacturing to prevent arcing between adjacent electrodes of the annular array. The material used for the electrically insulating layer can be the same as the composite filler material, or it can be a different material selected independently as needed to select the preferred mechanical properties and dielectric breakdown strength of each material.

[0145] Figure 4C shows a segment of a piezoelectric composite disk 210A with an alternative composite structure prior to the epoxy resin matrix, showing only the piezoelectric pillars. In this example embodiment, the pillars 350 are segments of annular rings, rather than rectangular prisms. This structure of the piezoelectric composite disk 210A enables a higher volume fraction of ceramic compared to the structure of Figure 4B. Moreover, mechanical isolation between adjacent ultrasonic elements (defined by adjacent annular electrodes) is increased by aligning the slits 360 that segment the piezoelectric composite material (and form spatially separated piezoelectric pillars) with the annular element gaps (and optional additional slits) after the annular electrode deposition. The structure shown in Figure 4C can be fabricated, for example, by laser cutting to obtain curved slits. Figure 4D shows the piezoelectric composite material 210A completed after the piezoelectric material mesh fills the matrix filler material to form the composite structure. As can be seen in the figure, the matrix filler material (e.g., epoxy resin) forms radially continuous filler material channels 355A and annular continuous filler material channels 355B.

[0146] Figure 4E shows a piezoelectric composite material 210A from Figure 4D with a partial slit (the upper ring electrode is not shown in this figure, page 12 / 20, CN 122028860 A-shaped electrode). The second annular array element 370 (which will be defined by the annular electrode) is shaded to show the spatial alignment between the array element and the underlying structure of the composite material. As described above, during subsequent steps of the manufacturing process, the slit 270 is filled with an electrical insulating layer material (the insulating layer will also cover the entire top surface of the piezoelectric composite material, as shown in the previous figure).

[0147] As noted above, an electrical signal transmission component (such as a printed circuit board or one or more cables) is disposed along or within at least a portion of the elongated body 120, and the electrical signal transmission component is connected toThe therapeutic ultrasound transducer assembly 200 is configured such that each electrode of the annular electrode array 260 is electrically connected to a corresponding electrical channel of the electrical signal transmission assembly, and that the common electrode 250 is electrically connected to a common electrical channel of the electrical signal transmission assembly. Similarly, the electrical signal transmission assembly is connected to the imaging transducer assembly 300 such that each electrode of the electrode array associated with the imaging ultrasound element of the imaging transducer assembly 300 is electrically connected to a corresponding electrical channel of the electrical signal transmission assembly.

[0148] The proximal end of the electrical signal transmission assembly is operatively coupled to or connected to control and processing circuitry for controlling the generation and transmission of focused ultrasound pulses by the therapeutic ultrasound transducer assembly 200, and the collection of ultrasound image data by the imaging transducer assembly 300. As described in further detail below, the processing and control circuitry includes ancillary electronics for generating focused ultrasound pulses from the therapeutic ultrasound transducer assembly 200 and acquiring ultrasound image data from the imaging transducer assembly 300.

[0149] Referring now to FIG5, an example system for performing mechanical linear ablation via an ultrasound therapy device is illustrated. The example system includes a therapeutic ultrasound device 100, as described above, comprising: a therapeutic ultrasound transducer assembly 200 and an imaging transducer assembly 300; a transmitting circuit 500 for transmitting transmitting voltage pulses to a ring electrode array of the therapeutic ultrasound transducer assembly 200; a transmitting circuit 505 and a receiving circuit 510 for transmitting transmitting voltage pulses to and receiving ultrasound signals from an imaging ultrasound array of the imaging transducer assembly 300, respectively; a transmitter-receiver switch 515; and a control and processing circuit 400 (e.g., a controller, computer, or other computing system). Although not shown in the figure, the system also includes a beamforming circuit for beamforming transmitted signals to the therapeutic ultrasound transducer assembly 400 and the imaging transducer assembly 300, and for beamforming ultrasound signals received by the imaging transducer assembly 300. This beamforming circuit can be implemented as, for example, a sub-component of the control and processing circuitry 400, a sub-component of the transmitting circuitry and the receiving circuitry, or as a separate component.

[0150] The control and processing circuitry 400 is used to control the transmitting circuits 500, 505 and the receiving circuitry 510, the Tx / Rx switch 515, and to process the received signals obtained from the imaging receiving circuitry 510. As shown in FIG5, in one embodiment, the control and processing circuitry 400 may include a processor 410, a memory 420, a system bus 405, one or more input / output devices 430, and a plurality of optional additional devices, such as a communication interface 460, a display 440, an external storage device 450, and a data acquisition interface 470.

[0151] The example methods of ultrasonic mechanical, cavitation-based linear ablation and ultrasound image-guided ablation in this disclosure can be implemented via processor 410 and / or memory 420. As shown in FIG5, control for delivering electrical pulses to the annular electrodes for generating focused ultrasound pulses and scanning the focused position for linear ablation can be implemented via control and processing circuitry 400, via executable instructions represented by focused ultrasound scanning module 480. Control and processing circuitry 400 may include and run scan conversion software (e.g., real-time scan conversion software) or other image processing functions represented by image processing module 490.

[0152] Transmitting circuitry 500 for controlling the delivery of voltage pulses to therapeutic ultrasound transducer assembly 200 is capable of high-voltage, monopolar or bipolar, multi-cycle excitation. Each annular electrode of therapeutic ultrasound transducer assembly 200 is connected to a corresponding channel of transmitting circuitry 500 with programmable phase delay.

[0153] The functions described herein may be implemented in part via hardware logic in processor 410 and in part by causing the specification pages 13 / 20 18 CN 122028860 A to use instructions stored in memory 420. Some embodiments may be implemented using processor 410 without additional instructions stored in memory 420. Some embodiments may be implemented by using instructions stored in memory 420 to be run by one or more general-purpose microprocessors. In some example embodiments, a custom processor, such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA), may be employed. Thus, this disclosure is not limited to a particular configuration of hardware and / or software.

[0154] Referring again to FIG5, it should be understood that the example system shown in the figure is not intended to be limited to the components that may be employed in a given implementation. For example, the system may include one or more additional processors. And one or more components of the control and processing circuitry 400 may be provided as external components that interface with the processing device. For example, as shown in the figure, any one or more of the transmit / receive circuits 500, 505, and 510 and the Tx / Rx switch 515 may be included as a component of the control and processing circuit 400 (as shown in the dashed lines) or may be provided as one or more external devices.

[0155] While some embodiments may be implemented in fully functional computers and computer systems, various embodiments may also be distributed as computing products in a wide variety of forms, and these embodiments may be applied regardless of the specific type of machine-readable or computer-readable medium actually used to implement the distribution.

[0156] At least some aspects disclosed herein may be embodied at least in part in software. That is, these techniques may respond to the processor (e.g., microprocessor) of a computer system or other data processing system by running memory (e.g., ROM, ...A sequence of instructions contained in volatile RAM, non-volatile memory, cache, or remote storage device is implemented in a computer system or other data processing system.

[0157] A computer-readable storage medium can be used to store software and data that, when run by a data processing system, enable the system to perform various methods. The operable software and data can be stored in various places, such as ROM, volatile RAM, non-volatile memory, and / or cache. A portion of the software and / or data can be stored in any of these storage devices. As used herein, the terms “computer-readable material” and “computer-readable storage medium” refer to all computer-readable media, but not to transient propagation signals themselves.

[0158] Figure 6A shows a block diagram of an example control subsystem for generating electrical pulses and providing electrical pulses to a therapeutic ultrasound transducer assembly 200 and an imaging transducer assembly 300. The delay generator hardware is digitally synchronized with the imaging pulses via a trigger pulse using a firmware-based programmable microprocessor (e.g., an FPGA). The microprocessor splits the trigger pulse into N channels corresponding to the number of elements in the therapeutic array. The microprocessor then delays the pulses of each channel to create a distribution map such that the wavefront from each element converges to the focal position. This distribution map corresponds to the time difference of flight from each element to the focal depth. The delayed pulses are then converted into a series of short trigger pulses separated by one wavelength, with a duty cycle of less than 50%. This corresponds to the desired number of cycles in the excitation pulse. The delayed multi-cycle pulses of each channel are then split into a positive pulse train and a copy of that pulse train with a nominally separated half-wavelength for the negative pulse. The half-wavelength separation between the pulse trains can be adjusted to compensate for the FET switching time to give the desired output duty cycle. The digital pulse trains (two per channel) are then directed to a high-voltage peak power pulse generator. For each channel, one copy of the pulse train is used to drive the positive side of the high-voltage pulse, and one copy is used to drive the negative side of the high-voltage pulse.

[0159] Figure 6B shows a block diagram illustrating an example system configured to split a delayed pulse train into two pulse trains for each channel and delay them by half a wavelength to trigger the positive and negative sides of a therapeutic pulse. This process is repeated for each incoming trigger pulse, and within the delay generator, the depth of focus can be altered by changing the delay distribution.

[0160] Figure 7A shows a photograph of an example therapeutic pulse generator subsystem. Figure 7B shows the electrical pulses generated from a single channel during operation. Figure 7C shows a portion of a typical delay distribution across the entire 16-element array during the generation of focused ultrasound pulses.

[0161] As described above, the annular electrode is excited by a voltage signal with a corresponding phase delay, causing the sound wave to be focused in therapeutic ultrasound.Constructive interference occurs at the focal point at a predetermined depth in front of the distal energy emission surface of the transducer assembly. By constructively combining the pressures generated from each annular array element, a threshold for mechanical ablation or cavitation can be reached, and the phase delay between the annular electrodes is controlled so that the focused region where cavitation can be sustained can be scanned in the elongated axial region for tissue ablation. The pressure threshold for mechanical ablation (cavitation) is much higher than that for thermal ablation; however, the pulse duration is short (duty cycle <1%), thus essentially avoiding tissue heating in the peripheral region around the ablation area.

[0162] Cavitation typically initiates at low f-numbers (i.e., at the minimum ablation depth), under which the pressure will be highest. Once a bubble cloud is formed, maintaining cavitation becomes easier because the bubble cloud itself is a strong reflector, and constructive interference increases the pressure at the boundary of the bubble cloud. Accordingly, cavitation can be maintained while the pressure generated by focusing at higher f-numbers is lower. Similarly, cavitation can be initiated at a higher frequency, where the focal gain is higher, and then the frequency can be reduced to complete linear ablation at a lower operating frequency. This method of cavitation generation and linear ablation can be used to increase the width of the ablation region, but initiate cavitation at a lower threshold. To broaden the operating frequency range, a matching layer can be applied to the front plane of the device.

[0163] The rasterization rate during linear ablation is typically based on the number of pulses per focal point, the pulse repetition frequency, and the focal point step size resolution. For example, the rasterization rate can be determined according to the following formula: Rasterization rate = (Z step size × PRF) / N pulses, where Z step size is the focal point step size resolution, PRF is the pulse repetition frequency, and N pulses is the number of pulses per focal point.

[0164] It has been found that the number of pulses per focal point generally affects the cavitation threshold and tissue erosion efficiency. If the focus is kept at a single focal position for several cycles (e.g., 2, 3, 4, or 5 cycles), this can improve the initiation of bubble clouds in tissue in some cases. Conversely, rapidly scanning the focal point and dwelling for less time can, in some cases, increase the rate of tissue erosion.

[0165] In some non-limiting exemplary embodiments, the therapeutic ultrasound device according to the embodiments described herein can perform tissue fragmentation in tissue with focused ultrasound parameters of PRF = 0.5 kHz to 2 kHz, 1 kHz to 2 kHz, or 0.5 kHz to 5 kHz, and N pulses between 1 and 16. For example, for a device operating at a frequency of 1.6 kHz to 2.4 kHz within a PRF of 0.5 kHz to 2 kHz and with N pulses between 1 and 16, and having an outer annular array diameter in the range of 20 mm to 25 mm, the step size during the ablation linear scan can, for example, be 0.4.The rasterization rate is, for example, between 0.7 m / s and 1.3 m / s within the range of mm to 0.6 mm. In another example, for a device operating at PRF = 0.5 kHz to 2 kHz, at frequencies between 2.4 kHz and 3.6 kHz, and with N pulses between 1 and 16, and having an outer annular array diameter in the range of 13 mm to 17 mm, the step size during the ablation linear scan can, for example, be in the range of 0.2 mm to 0.4 mm, where the rasterization rate is, for example, between 0.3 m / s and 0.7 m / s.

[0166] In an embodiment where an imaging transducer assembly is incorporated within the central portion of a therapeutic ultrasound transducer assembly, and where the imaging transducer assembly is controlled to acquire image data in a spatial region overlapping with the scanning focal region of the focused therapeutic ultrasound pulse, mechanical ablation due to cavitation can be confirmed by observing the formation and collapse of bubble clouds in the ultrasound image presented on a user interface (e.g., an image-guided system). For example, image data can be processed to generate one or more ultrasound images from image modalities, such as, but not limited to, B-mode, power Doppler images, or other ultrasound image modalities, such as the subframe differential method described below.

[0167] As explained above, during tissue ablation surgery, the phase delay distribution of each emission excitation delivered to the annular electrode array of the therapeutic ultrasound transducer assembly can be controlled to rasterize the focus position (e.g., focusing depth, page 15 / 20 of the specification, 20 CN 122028860 A) along a line (or axis) extending from a first position to a second position further away from the energy emission surface of the therapeutic ultrasound transducer assembly. In some example embodiments, the phase delay distribution can be controlled by a control unit (e.g., an FPGA, a microcontroller) at a sufficiently fast rate to rasterize the ablation spot at a rate >20 Hz (generally considered "real-time"), where the delay is accurate to less than 1 / 20 of the wavelength.

[0168] The control and processing circuitry can be programmed to jointly (e.g., synchronously) control the transmit / beamforming electronics associated with the therapeutic ultrasound transducer assembly and the transmit / receive / beamforming electronics associated with the imaging transducer assembly, so that therapeutic and imaging excitations are interleaved while avoiding interference with either process.

[0169] It will be understood that, according to a variety of embodiments (which are not limited to collecting complete image frames between therapeutic pulses), therapeutic pulses can be interleaved with imaging pulses. For example, a first subset of focused image lines (a subset of complete image frames) can be collected by the imaging transducer assembly between therapeutic sonications, and a second subset of focused image lines (a subset of complete image frames) can be collected between the next pair of therapeutic sonications. This sequence can continue until captureA complete image frame is acquired, and then the staggered image acquisition sequence can be repeated. Ultrasound images (e.g., full-frame B-mode images) can be updated after each full-frame image data is acquired, or locally updated each time a corresponding subset of image data is acquired. This method avoids the limitation of the imaging frame rate on the frequency of treatment pulse repetition.

[0170] By making tissue types (muscle, fat, blood vessels, and nerves) visible before initiating mechanical ablation, the acquisition of image data and the generation and display of guiding images provide surgeons with preoperative image guidance. Image guidance allows surgeons to assess the size and location of the area to be treated (including the target depth range) and confirm that all sensitive tissues (such as arteries, large blood vessels, and nerves) are clearly outside the treatment area. Part of the surgical plan may include assessing structures (i.e., blood vessels and nerves) that will not be damaged near the target tissue. When cavitation begins, a cloud of bubbles becomes visible on the imaging plane (e.g., in B-mode images, and optionally in image enhancement overlays). After cavitation, blood may fill and accumulate in the ablation area and coagulate, becoming highly echogenic and therefore bright in B-mode ultrasound images.

[0171] As noted above, the imaging array can be a linear array or a phased array, thereby providing 2D slices that are co-aligned and co-registered with the ablation region. Alternatively, a high-resolution imaging array is capable of 3D imaging. Embodiments of the device may include a 2D array or a 1D array on a mechanically tilting jig, both of which capture the plane surrounding the ablation region to provide additional background information in image guidance.

[0172] The ultrasound-guided image can be enhanced according to several techniques. Conventional power Doppler methods can be used to highlight cavitation bubble clouds. Alternatively, elastography can be used to highlight differences in tissue elasticity between the treated and untreated areas.

[0173] In one example embodiment, a subframe differencing method can be used to enhance the B-mode image to provide image enhancement associated with the time-related characteristics of cavitation. In one example implementation of this method, two image subframes or subframes collected with low latency are subtracted row by row, and the resulting differencing (subtracted) image is superimposed on the B-mode image. In some example implementations, because only a subset (subframe) of the complete image frame is collected, the time delay between the acquisition of successive images used for subtraction is low. For such a subframe differencing method, repetitive imaging acoustic transmission can also be flexibly interleaved with therapeutic pulses. For example, subframes corresponding to eight image rows are collected, then the same subframes are recollected (optionally after one or more therapeutic acoustic irradiations (pulses), and subtraction is performed to generate a subtracted image for image annotation. This sequence can be performed within subframes of different sizes and time intervals of different sizes for therapeutic purposes. Thus, the repetition frequency of the therapeutic pulses andThe interval between subframe collections is not dependent on the time required to collect a complete B-mode image. This improves the highlighting capability of the subframe difference method by capturing the faster movement of the bubble cloud.

[0174] Figure 8 shows the results of the subframe difference method superimposed on the B-mode image for single-focus depth ablation at 3 mm, 5 mm, and 7 mm, and for real-time linear ablation between 3 mm and 8 mm. The tissue is shown in the B-mode image, and the bubble cloud is highlighted in bright white in this example; however, color mapping further distinguishes the cavitation.

[0175] It will be understood that the cavitation threshold varies depending on the tissue type. For example, fat has a lower threshold than muscle, nerve, and blood vessel, making this tool ideal for volume reduction surgery targeting fat. The mechanical ablation device enables tissue selectivity, which increases the safety level of the procedure. Patient-specific threshold setting is possible with a mechanical ablation device co-aligned with the imaging device. At the start of the procedure, the surgeon can confirm the minimum emission voltage required for ablation in the fat region by using images for cavitation confirmation. Ultrasound-guided images facilitate threshold tuning. The threshold can be set based on the excitation required to induce an incomplete ablation line for tissue reduction surgery.

[0176] An incomplete ablation line observed in ultrasound-guided images means that fat is being ablated while muscle remains undamaged. Depending on risk and adjacent structures, the procedure can be performed at a voltage with a small margin (10-20%) above the established threshold. In one example embodiment, the system can be used to autonomously monitor the bubble cloud during the procedure and notify the surgeon if ablation unexpectedly stops, or if the guided images meet (or do not meet) predetermined image criteria associated with an acceptable or desired spatial ablation distribution (e.g., by processing image data according to a predetermined mask or surgical plan). The system can also interrupt the delivery of focused ultrasound treatment pulses if the ablation line becomes a complete, continuous line, thereby triggering the surgeon to re-establish the cavitation threshold. The system can automatically increase the excitation voltage for the treatment array within safe limits to maintain the bubble cloud.

[0177] Design decisions regarding transducer size, element count, and operating frequency will be based on the requirements of the individual surgical procedure, including the maximum probe diameter compatible with the surgical approach, the depth of the relevant anatomical feature, the size of the relevant anatomical feature, and the size and type of tissue to be ablated. It will be understood that the dual-modal imaging and therapeutic ultrasound transducer according to this disclosure can be provided in a variety of configurations, such as, for example, forward-looking orientation, side-looking orientation, or custom orientation tailored for laparoscopic or endoscopic applications. Similarly, the length of the extension portion can be selected to access the target anatomical structure.

[0178] An example embodiment of the form factor is shown in Figure 9. In the example embodiment shown in the figure, high frequency, high...The resolution ultrasound imaging array can operate at frequencies ranging from, for example, 15 MHz to 25 MHz. The diameter of the treatment array and the bimodal device is between 10 mm and 25 mm. The thickness of the side-viewing device can be between 1 mm and 5 mm. The treatment array is capable of real-time mechanical linear ablation, adjusted to grid the depth of focus or range corresponding to an f-number of 0.3 to 1.2.

[0179] In some embodiments, the probe is rigid, and the handheld portion is connected to the extended portion and the angled portion, such that the probe bends to better access the desired anatomical region, such as the tongue. Additionally, the imaging transducer assembly and the therapeutic ultrasound transducer assembly can be oriented at an angle to further facilitate access to the desired anatomical region, such as the base of the tongue. In some example embodiments, the length of the first (extended) portion of the handle body is between 5 cm and 15 cm, and the length of the angled portion is between 2 cm and 8 cm. The angled portion can be at an angle between 15° and 45° relative to the extended portion. Imaging transducers and therapeutic ultrasound transducers can be oriented at an angle between 70° and 90° relative to the angled portion of the probe.

[0180] In some example embodiments, the annular array defined by the outer diameter of the outer annular electrode ranges from 8 mm to 50 mm and operates in a frequency range from 600 kHz to 6 MHz. The therapeutic annular array is constructed of a series of element counts (N = 8 to N = 64) to scan and focus within a series of depths (e.g., f# 0.4 to f# 1.5). Apertures on the annular array are made to accommodate the imaging array. In some embodiments, the aperture is circular with a diameter ranging from 3 mm to 10 mm; while in other embodiments, the aperture is rectangular (with a width ranging from 3 mm to 10 mm). The imaging array can be a 1D, 1.5D, 2D, or ring array; however, one or more imaging lines generated by the array overlap with the treatment focus line. Specification 17 / 20 pages 22 CN 122028860 A

[0181] In one example embodiment, the diameter of the dual-modal imaging and treatment transducer at the distal end is between 12 mm and 17 mm. The treatment elements capable of mechanical ablation can be arranged in a ring array pattern and operate at a frequency between 2.5 MHz and 3.5 MHz. The ablation area can be approximately 1 mm wide and can vary in depth from 5 mm to 15 mm. The treatment element has a central aperture in which the imaging element is co-aligned with the central axis of the treatment element. The imaging element can operate at a frequency between 15 MHz and 25 MHz, and the imaging window has a maximum depth of 2.5 cm to 3.5 cm. This set of linear imaging elements has a width of 4 mm to 5 mm. mm, with a height of 4 mm to 5 mm, and in a series of f numbers (f# 0.4 toFocusing within a range of depths (f# 1.5).

[0182] For an array of 16 elements with an outer diameter between 8 mm and 23 mm and a frequency between 2 MHz and 5 MHz, the outer elements are typically between 60 μm and 230 μm, respectively. Narrow elements hinder the option of widening the slit to prevent arcing between elements. For the series of embodiments listed above, the slit width between elements is typically in the range of 20 μm to 80 μm when an isolation layer is present.

[0183] In this example embodiment, the 2D imaging plane can be oriented in one of two directions relative to the handpiece. First, it is in the same plane as the extended portion of the probe. In the case of tongue reduction, this will produce an image along the length of the tongue. In an alternative embodiment, the imaging array and the corresponding plane will be rotated 90°. Again, in the tongue reduction example, this will produce an image of the tongue in cross-section, thereby making the lingual arteries and nerves extending along both sides of the tongue visible during surgery.

[0184] Embodiments of this disclosure enable non-invasive removal of tissue in minimally invasive surgery. The ablation area is below the contact surface. Therefore, the procedure is performed without creating an open wound. The non-invasive nature of this method eliminates the risk of complications and infection before and after wound healing. A non-limiting list of example applicable procedures includes superficial, endoscopic, and laparoscopic procedures for the skin, nose, tongue, prostate, thyroid, brain, esophagus, stomach, and colon.

[0185] In one example embodiment, the above-described therapeutic ultrasound device can be used in tissue reduction surgery. For ease of illustration, tongue reduction for the treatment of sleep apnea is used as an example procedure. In imaging mode, the probe is positioned on the tongue. The surgeon assesses the tissue to be reduced and the structure to be protected. Based on the size of the target tissue, the surgeon can plan the number, location, and depth range of a set of non-overlapping ablation lines. When the surgical plan is finalized, the surgeon uses the system to test the cavitation threshold in areas containing fat. This procedure determines a series of safe excitation voltages for the treatment array.

[0186] Ablation can begin at a first location. The bubble cloud is monitored in the image while being rasterized. Motion enhancement overlays can be placed on top of the B-mode image to highlight the rapidly changing bubble cloud. After the treatment dose, the blood will coagulate in the empty space. In the B-mode ultrasound image, the coagulated blood appears hyperechoic (as shown in Figure 10). Therefore, the treatment area remains visible throughout the procedure. The surgeon will use the image as a guide to reposition the device for the next ablation line and initiate cavitation on the system. Because rasterization is performed in real time, cavitation at each location takes only a few seconds to complete. This process is repeated until the surgical plan is completed.

[0187] Figure 11A shows an example of an example of the interconnection between an electrical signal transmission component and a therapeutic ultrasound transducer component.Example. In this example embodiment, the electrical signal transmission component is implemented as a two-pin flexible interconnect PCB 600. Both pins have exposed pads for electrical connection to an exposed annular electrode 260 and an interconnect ring 230. Figure 11B shows details of the electrical interconnect. The end portions of the two external pins 610 are each bonded to the back of the array. The electrical connection implemented in this example, by wire bonding 630, is established between the interconnect PCB pads 620 and the exposed annular array element 620 (accessible via a aperture formed within the electrical isolation layer 290), and between the ground pad 640 and the interconnect ring 230 electrically connected to the common electrode on the distal side of the piezoelectric composite layer. In some example embodiments, the front (distal) side electrical connection to the common electrode is achieved through physical metal-to-metal contact, thin metal deposition, conductive epoxy, soldering, or wire bonding. Figure 11C shows the electrical connection protected by potting epoxy, and the isolation layer 192 cast over the entire remaining surface of the array. Finally, a low-impedance backing layer 215 is cast on top of the isolation layer, as shown in Figure 11D. Depending on the desired profile, the interconnect (45) may remain flat or be bent upwards before casting the isolation layer (145) and the backing layer (150).

[0188] Figures 12A to 12E show a similar example embodiment of the interconnect between the electrical signal transmission assembly (flexible printed circuit board 600) and the therapeutic ultrasound transducer assembly 200. In addition to the two external pins 610, the internal pin 640 is used to connect to a common electrode on the front (far) surface of the piezoelectric composite material, instead of a grounding ring. Figures 12A and 12B show the far portion of the flexible circuit board bonded to the array via electrical connections 630. The inner pin 640 is bent such that its end is perpendicular to the surface of the piezoelectric composite material, and an electrical connection is established from the thickness (cross-section) of the interconnecting trace to a common electrode located on the distal (positive) surface of the piezoelectric composite material, thereby creating a ground connection.

[0189] FIG12C shows a view from FIG12B after the addition of the potting layer, insulating layer, and backing layer 215. FIG12D shows a front view of the therapeutic device before the application of the backing layer to highlight the ground electrical connection 645 to the front of the therapeutic array before the backing layer, and shows the imaging transducer assembly 300 located within the central aperture. FIG12E shows a front view after the addition of the potting layer 650, insulating layer, and backing layer 215.

[0190] In some cases, the aperture for the imaging transducer assembly interferes with the annular array pattern, thereby creating discontinuous annular electrode elements near the center of the annular array. Figure 13A shows a therapeutic ultrasound transducer assembly 200 (example with a diameter of 8 mm), where a partial slit 270 and an example therapeutic element 700 are shown in shaded areas. These elements can be spliced ​​together to restore an effective treatment area.

[0191] Figure 13B illustrates an example embodiment of connecting segmented ring electrodes. A partial ring PCB 720 (not shown in the figure) with traces is used for wiring and electrical connections to each quadrant. A backing 725 (e.g., as shown in Figure 3E) may be applied under the partial ring PCB before wire bonding to the components as shown at 730. The remaining portion of the array may be coated with an electrical isolation layer and backed as previously discussed.

[0192] An alternative example involves contact points using small (~0.5 mm square) segments of a PCB 750 with exposed pads or trace cross-sections, as shown in Figure 13C. The number of pads / traces in each PCB segment corresponds to the number of components divided by the aperture. The segments of the PCB may be bonded to the ring array, for example, near the three interior corners of the ring array. Jumper connections 755 may be established from one segment of the component to a PCB segment and then to the next segment of the component. Electrical connections may be accomplished by wire bonding. Using this method, electrical connections to the PCB will be completed from a single area, as described.

[0193] Examples

[0194] The following examples are intended to enable those skilled in the art to understand and practice embodiments of the present disclosure. They should not be considered as limitations on the scope of the disclosure, but merely as examples and representations.

[0195] Figures 14 through 16 show photographs of various therapeutic devices manufactured according to embodiments disclosed above.

[0196] Figure 14 shows a detailed assembly of an example side-view therapeutic array, focusing on electrical interconnections. Figure 14a shows the array and interconnecting PCBs coplanarly mounted to each other. Figure 14b shows electrical connections between array elements and exposed pads on the interconnecting PCB, and PCB segments interrupted by holes used for the imaging array for splicing elements. In Figure 14c, the connections are protected by potting with epoxy resin. Figure 14d provides an enlarged view of the electrical connections before the application of potting or isolation layers. Figure 14e highlights PCB segments used for re-splicing elements interrupted by a central hole, which is configured to accommodate the imaging array to maximize the effective portion of the aperture.

[0197] Figure 15 is a photograph of a side-view treatment array with the imaging array centered. In this example, the imaging array is 3.5 mm wide and operates at 30 MHz. The treatment array is 8 mm wide and focused over a range of approximately 3 mm to 8 mm. A high-frequency imaging array is monitored throughout the treatment process.

[0198] Figure 16 highlights the process of patterning and aligning annular electrodes on a radial composite material. The left-hand image (pages 19 / 20, CN 122028860 A) shows the composite structure before electrode patterning, while the right-hand image shows the structure after electrode patterning. Aligning the composite pattern with the annular array element pattern maximizes the achievable volume fraction and mechanical separation of the array elements.

[0199] The specific embodiments described above are illustrated by way of example, and it should be understood that various modifications and alternatives may easily arise from these embodiments. It should be further understood that the claims are not intended to limit the specific forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure. Instruction Manual 20 / 20 Page 25 CN 122028860 A Figure 1A Figure 1B Instruction Manual Drawings 1 / 25 Page 26 CN 122028860 A Figure 1C Figure 1D Instruction Manual Drawings 2 / 25 Page 27 CN 122028860 A Figure 2A Figure 2B Figure 2C Instruction Manual Drawings 3 / 25 Page 28 CN 122028860 A Figure 2D Figure 2E Figure 2F Instruction Manual Drawings 4 / 25 Page 29 CN 122028860 A Figure 3A Figure 3B Instruction Manual Drawings 5 / 25 Page 30 CN 122028860 A Figure 3C Figure 3D Instruction Manual Drawings 6 / 25 Page 31 CN 122028860 A Figure 3E Figure 3F Instruction Manual Drawings 7 / 25 Page 32 CN 122028860 A Figure 4A Figure 4B Instruction Manual Drawings 8 / 25 Page 33 CN 122028860 A Figure 4C Figure 4D Figure 4E Instruction Manual Drawings Page 9 / 25 34 CN 122028860 A Figure 5 Instruction Manual Drawings Page 10 / 25 35 CN 122028860 A Figure 6A Figure 6B Instruction Manual Drawings Page 11 / 25 36 CN 122028860 A Figure 7A Instruction Manual Drawings Page 12 / 25 37 CN 122028860 A Figure 7B Figure 7C Instruction Manual Drawings Page 13 / 25 38 CN 122028860 A Figure 8 Figure 9 Instruction Manual Drawings Page 14 / 25 39 CN 122028860 A Figure 10 Figure 11A Instruction Manual Drawings Page 15 / 25 40 CN 122028860 A Figure 11B Figure 11C Instruction Manual Drawings Page 16 / 25 41 CN 122028860 A Figure 11D Figure 12A, page 42, CN 122028860 A; Figure 12B, page 43, CN 122028860 A; Figure 12C, page 44, CN 122028860 A; Figure 12C, page 45, CN 122028860 A.Figure 12D Appendix to the Instruction Manual, Page 21 / 25, 46 CN 122028860 A Figure 12E Appendix to the Instruction Manual, Page 22 / 25, 47 CN 122028860 A Figure 13A Figure 13B Appendix to the Instruction Manual, Page 23 / 25, 48 CN 122028860 A Figure 13C Figure 14 Appendix to the Instruction Manual, Page 24 / 25, 49 CN 122028860 A Figure 15 Figure 16 Appendix to the Instruction Manual, Page 25 / 25, 50 CN 122028860 A

Claims

1. A therapeutic ultrasound system for performing tissue ablation via cavitation, said therapeutic ultrasound system comprising: A therapeutic ultrasound transducer assembly, the therapeutic ultrasound transducer assembly comprising: A piezoelectric composite layer having a proximal surface and a distal surface; A ring electrode array, wherein the ring electrode array is disposed on the proximal surface of the piezoelectric composite layer; A common electrode is disposed on the distal surface of the piezoelectric composite layer; An electrical isolation layer is disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer; An elongated body, wherein the therapeutic ultrasound transducer assembly is supported at a proximal end remote from the elongated body; An electrical signal transmission assembly is disposed along at least a portion of the elongated body, wherein the electrical signal transmission assembly is operatively connected to the therapeutic ultrasound transducer assembly such that the electrodes of the annular electrode array are electrically connected to corresponding electrical channels of the electrical signal transmission assembly, and the common electrode is electrically connected to a common electrical channel of the electrical signal transmission assembly; and A control and processing circuit, operatively coupled to the therapeutic ultrasound transducer assembly via the electrical signal transmission component, is configured to generate electrical pulses that are transmitted via the electrical signal transmission component to the annular electrode array for generating focused ultrasound pulses suitable for inducing cavitation in water; and Wherein, the thickness of the electrically insulating layer is less than the wavelength of the focused ultrasonic pulse within the electrically insulating layer; and The thickness of the electrical isolation layer and the dielectric breakdown strength of the electrical isolation layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within the backing of the therapeutic ultrasound transducer assembly during the generation of the focused ultrasound pulse for cavitation.

2. The therapeutic ultrasound system according to claim 1, wherein, The piezoelectric composite layer is configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least one pair of adjacent electrodes in the annular electrode array, and wherein an electrically insulating material forming the electrically insulating layer is located within each annular slit.

3. The therapeutic ultrasound system according to claim 2, wherein, At least one annular slit extends from the proximal surface to the distal surface.

4. The therapeutic ultrasound system according to claim 2, wherein, Each annular slit extends from the proximal surface to the distal surface.

5. The therapeutic ultrasound system according to claim 2, wherein, At least one annular slit is a partial slit that extends from the proximal surface into the piezoelectric composite layer but does not extend to the distal surface.

6. The therapeutic ultrasound system according to claim 2, wherein, Each annular slit is a partial slit that extends from the proximal surface into the piezoelectric composite layer but not into the distal surface.

7. The therapeutic ultrasound system according to claim 5 or 6, wherein, The slit has a depth between 5% and 95% of the thickness of the piezoelectric composite layer.

8. The therapeutic ultrasound system according to claim 5 or 6, wherein, The slit has a depth between 5% and 90% of the thickness of the piezoelectric composite layer.

9. The therapeutic ultrasound system according to claim 5 or 6, wherein, The slit has a depth between 5% and 75% of the thickness of the piezoelectric composite layer.

10. The therapeutic ultrasound system according to claim 5 or 6, wherein, The slit has a depth between 50% and 95% of the thickness of the piezoelectric composite layer.

11. The therapeutic ultrasound system according to claim 5 or 6, wherein, The slits have a depth between 50% and 90% of the thickness of the piezoelectric composite layer.

12. The therapeutic ultrasound system according to claim 5 or 6, wherein, The slit has a depth between 50% and 75% of the thickness of the piezoelectric composite layer.

13. The therapeutic ultrasound system according to any one of claims 2 to 12, wherein, The thickness of the electrical isolation layer on each electrode of the annular electrode array exceeds the width of the annular slit.

14. The therapeutic ultrasound system according to any one of claims 2 to 13, wherein, The piezoelectric composite layer includes an array of piezoelectric pillars embedded in a substrate, the piezoelectric pillars extending from the proximal surface to the distal surface, wherein the piezoelectric pillars are arranged in a segmented annular array, the segmented annular array comprising a plurality of concentric piezoelectric pillar arrays, such that each electrode of the annular electrode array is electrically actuated by one or more radially extending piezoelectric pillar arrays, and such that each annular slit is aligned with and extends into an annular substrate region located between a corresponding pair of radially adjacent concentric piezoelectric pillar arrays.

15. The therapeutic ultrasound system according to any one of claims 1 to 14, wherein, The electrical isolation layer has a dielectric breakdown strength between 10 kV / mm and 280 kV / mm.

16. The therapeutic ultrasound system according to any one of claims 1 to 15, wherein, The therapeutic ultrasound transducer assembly is an air-backed type.

17. The therapeutic ultrasound system according to any one of claims 1 to 15, wherein, The therapeutic ultrasound transducer assembly includes a backing layer embedded with microballoons.

18. The therapeutic ultrasound system according to any one of claims 1 to 17, wherein, The ring electrode array is configured such that the lateral electrode spacing is between 20 micrometers and 80 micrometers.

19. The therapeutic ultrasound system according to any one of claims 1 to 17, wherein, The outer diameter of the annular electrode array is between 10 mm and 25 mm, and the number of electrodes forming the annular electrode array is between 8 and 64.

20. The therapeutic ultrasound system according to claim 1, wherein, The piezoelectric composite layer includes an array of piezoelectric pillars embedded in a substrate, the piezoelectric pillars extending from the proximal surface to the distal surface, wherein the piezoelectric pillars are arranged in a segmented annular array, the segmented annular array comprising a plurality of concentric piezoelectric pillar arrays, such that each electrode of the annular electrode array is electrically actuated by one or more radially extending piezoelectric pillar arrays, and such that each annular electrode gap is aligned with an annular substrate region located between a corresponding pair of radially adjacent concentric piezoelectric pillar arrays.

21. The therapeutic ultrasound system according to any one of claims 1 to 20, wherein, The electrical signal transmission component is operatively connected to the therapeutic ultrasound transducer component via multiple wire bonds.

22. The therapeutic ultrasound system according to claim 21, wherein, Each wire bond electrically connects the corresponding electrode of the annular electrode array to the corresponding conductive channel of the electrical signal transmission component via an aperture formed in the electrical isolation layer.

23. The therapeutic ultrasound system according to any one of claims 1 to 20, wherein, The common electrode is electrically connected to the electrical signal transmission component via a grounding ring extending along at least a portion of the outer peripheral edge of the piezoelectric composite layer.

24. The therapeutic ultrasound system according to any one of claims 1 to 20, wherein, The electrical signal transmission component includes a flexible printed circuit board.

25. The therapeutic ultrasound system according to claim 24, wherein, The flexible printed circuit board is operatively connected to the therapeutic ultrasound transducer assembly via a direct bond from the distal region of the flexible printed circuit board through an aperture formed in the electrical isolation layer.

26. The therapeutic ultrasound system according to any one of claims 1 to 25, wherein, The thickness of the electrical isolation layer is equal to one-quarter of the wavelength of the focused ultrasound pulse within the electrical isolation layer.

27. The therapeutic ultrasound system according to any one of claims 1 to 25, wherein, The thickness of the electrical isolation layer is equal to half the wavelength of the focused ultrasound pulse within the electrical isolation layer.

28. The therapeutic ultrasound system according to any one of claims 1 to 27, wherein, The therapeutic ultrasound transducer assembly further includes a fixed acoustic lens.

29. The therapeutic ultrasound system according to claim 28, wherein, The fixed acoustic lens has an f-number between 0.5 and 3.

30. The therapeutic ultrasound system according to any one of claims 1 to 29, wherein, The control and processing circuitry is configured to control the therapeutic ultrasound transducer assembly to scan the focused ultrasound pulses in an elongated axial region located distal to the distal energy emitting surface of the therapeutic ultrasound transducer assembly.

31. The therapeutic ultrasound system according to claim 30, wherein, The control and processing circuit is configured to unidirectionally scan the focused ultrasound pulse within the elongation axial region.

32. The therapeutic ultrasound system according to claim 30 or 31, wherein, The control and processing circuitry is configured to scan the focused ultrasound pulses at a scan rate between 0.3 m / s and 1.3 m / s.

33. The therapeutic ultrasound system according to any one of claims 30 to 32, further comprising an imaging transducer assembly supported by the elongated body such that the distal surface of the imaging transducer assembly lies within a central aperture defined within the therapeutic ultrasound transducer assembly, and wherein, The control and processing circuitry is operatively coupled to the imaging transducer assembly via the electrical signal transmission component; and The control and processing circuit is configured to control the imaging transducer assembly to acquire and process ultrasound image data to generate one or more ultrasound images, wherein the ultrasound images represent an imaging region that spatially overlaps with the elongation axial region.

34. The therapeutic ultrasound system according to claim 33, wherein, The control and processing circuitry is further configured to control the therapeutic ultrasound transducer assembly and the imaging transducer assembly such that scanning of the focused ultrasound pulses to perform linear ablation is initiated only after cavitation in the ultrasound image is detected.

35. The therapeutic ultrasound system according to claim 33 or 34, wherein, The control and processing circuit is further configured to control the therapeutic ultrasound transducer assembly and the imaging transducer assembly, such that the collection of ultrasound image data by the imaging transducer assembly and the transmission of the focused ultrasound pulses are performed alternately.

36. The therapeutic ultrasound system according to claim 35, wherein, The control and processing circuitry is configured such that the ultrasound image data collected between successively generated focused ultrasound pulses represents a subset of the complete image frames of the B-mode image.

37. The therapeutic ultrasound system according to claim 36, wherein, The control and processing circuit is configured to acquire ultrasound image data corresponding to a selected subset of complete B-mode image frames before and after the generation of a given focused ultrasound pulse, thereby obtaining first ultrasound image data and second ultrasound image data characterizing the selected subset of complete B-mode image frames, wherein the control and processing circuit is configured to process the first ultrasound image data and the second ultrasound image data to generate a differential image characterizing time variations within the selected subset of complete B-mode image frames.

38. The therapeutic ultrasound system according to claim 37, wherein, The control and processing circuit is configured to display the complete B-mode image frame and annotate the complete B-mode image frame based on the differential image.

39. The therapeutic ultrasound system according to any one of claims 33 to 38, wherein, The central aperture has a segmented shape that results in the inner electrodes of the annular electrode array, and wherein the segmented portions of the inner electrodes are electrically connected so as to be actuated by a single channel of the electrical signal transmission component.

40. A method for performing tissue ablation via cavitation, the method comprising: The distal energy-emitting surface of the therapeutic ultrasound transducer assembly is acoustically contacted with tissue, the therapeutic ultrasound transducer assembly comprising: A piezoelectric composite layer having a proximal surface and a distal surface; A ring electrode array, wherein the ring electrode array is disposed on the proximal surface of the piezoelectric composite layer; A common electrode is disposed on the distal surface of the piezoelectric composite layer; An electrically insulating layer is disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer; and An electrical pulse is generated and transmitted to the annular electrode array to generate a focused ultrasonic pulse suitable for generating cavitation in the subsurface focusing region; Wherein, the thickness of the electrical isolation layer is less than the wavelength of the focused ultrasonic pulse within the electrical isolation layer; and The thickness of the electrical isolation layer and the dielectric breakdown strength of the electrical isolation layer are sufficiently high to prevent arcing between adjacent electrodes of the annular electrode array within the backing of the therapeutic ultrasound transducer assembly during the generation of the focused ultrasound pulse for cavitation.

41. The method of claim 40, further comprising controlling the delay between the electrical pulses delivered to the annular electrode array such that the subsurface focusing region is scanned to perform linear ablation on the tissue.

42. A therapeutic ultrasound device for performing tissue ablation via cavitation, the therapeutic ultrasound device comprising: A therapeutic ultrasound transducer assembly, the therapeutic ultrasound transducer assembly comprising: A piezoelectric composite layer having a proximal surface and a distal surface; A ring electrode array, wherein the ring electrode array is disposed on the proximal surface of the piezoelectric composite layer; A common electrode is disposed on the distal surface of the piezoelectric composite layer; An electrical isolation layer is disposed on the annular electrode array on the proximal surface of the piezoelectric composite layer; An elongated body, wherein the therapeutic ultrasound transducer assembly is supported at a proximal end remote from the elongated body; The piezoelectric composite layer is configured such that an annular slit extends from the proximal surface into the piezoelectric composite layer between at least one pair of adjacent electrodes in the annular electrode array, and wherein an electrically insulating material forming the electrically insulating layer is located within each annular slit.

43. The therapeutic ultrasound device according to claim 42, wherein, At least one annular slit is a partial slit that extends from the proximal surface into the piezoelectric composite layer but does not extend to the distal surface.

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