An ultrasonic probe for deep soft tissue imaging such as breast and a manufacturing method thereof

Abstract

The application relates to the technical field of ultrasonic probes, and particularly discloses an ultrasonic probe for deep imaging of soft tissues such as breasts and a preparation method, wherein the ultrasonic probe is an ultrathin flexible multilayer composite conformal structure with a total thickness less than 3 mm, and is sequentially stacked from top to bottom with a packaging layer, a flexible circuit connection layer, a backing layer, an upper electrode layer, a piezoelectric element layer, a lower electrode layer and a double-layer matching layer. Through the micro-spacing bonding design of the flexible circuit connection layer, stable bidirectional signal transmission between each array element and an external imaging system is realized, and the accuracy of phased array beam electronic focusing and deflection is guaranteed; the whole probe is packaged by using biocompatible medical-grade materials, which not only provides effective protection for the internal core structure, but also guarantees the biosafety of clinical contact use.

Description

Technical Field

[0001] This invention relates to the field of ultrasound probe technology, specifically to an ultrasound probe for deep imaging of soft tissues such as the breast and its preparation method. Background Technology

[0002] Ultrasound imaging technology, with its advantages of being non-invasive, real-time, non-ionizing radiation, and easy to operate, has become a core imaging tool for clinical screening and diagnosis of soft tissue diseases such as breast cancer. As the core functional component of an ultrasound imaging system, the performance of its piezoelectric materials, structural design, and acoustic parameter matching directly determine the imaging quality, clinical applicability, and safety of use. This represents a core research direction for the development of ultrasound imaging technology.

[0003] Most commercially available ultrasound probes use piezoelectric ceramics as the core transducer material. While these materials possess good structural stability, their piezoelectric properties and electromechanical conversion efficiency have inherent limitations, making it difficult to simultaneously meet the requirements of acoustic energy penetration for deep tissue imaging and high-resolution detection of small lesions, thus limiting the potential for improvement in imaging performance. Existing relaxor ferroelectric single-crystal materials, although showing breakthroughs in piezoelectric properties, suffer from inherent defects in temperature stability. Under high-electric-field driving and continuous heating scenarios in clinical settings, they are prone to depolarization, leading to performance degradation or even functional failure, compromising long-term reliability. Furthermore, these materials exhibit significant performance degradation under high-frequency operating conditions, making them unsuitable for high-resolution ultrasound imaging applications.

[0004] At the structural design level, traditional ultrasound probes generally adopt a rigid, integral structure, which cannot achieve good conformal fit with the highly curved surfaces of the human body, such as the breast. During clinical testing, external pressure must be applied to the probe, along with a large amount of ultrasound coupling agent, to complete acoustic coupling. This not only significantly reduces patient comfort but also easily leads to deformation of the examined soft tissue, causing distortion of lesion morphology and location, directly affecting the accuracy of diagnostic results. Existing flexible ultrasound probes, on the other hand, have consistently failed to balance ultra-thin structural design with high-performance imaging requirements: ensuring imaging performance often necessitates increasing structural thickness, making them unsuitable for emerging clinical scenarios requiring wearable, long-term continuous monitoring; while reducing structural size to achieve flexibility and miniaturization significantly sacrifices imaging performance, failing to meet the imaging needs of deep breast tissues. Achieving an effective balance between imaging quality, structural flexibility, and device portability remains a challenge.

[0005] In terms of imaging performance optimization, existing probes lack a systematic and collaborative design for imaging deep soft tissues such as the breast. On the one hand, unreasonable acoustic impedance matching design leads to insufficient acoustic energy transmission efficiency between piezoelectric elements and human soft tissues, resulting in low signal-to-noise ratio of echo signals from deep tissues and making it difficult to achieve clear imaging of deep regions. On the other hand, the phased array element design lacks targeted optimization, easily leading to lateral vibration coupling and electrical crosstalk between elements, resulting in severe clutter interference during imaging. Furthermore, it fails to achieve optimal matching between imaging depth and resolution, making it difficult to accurately detect small lesions in deep tissues and failing to meet the clinical needs of early breast cancer screening.

[0006] In summary, existing ultrasound probes cannot simultaneously meet the multiple clinical needs of high voltage performance, high temperature stability, ultra-thin flexible conformal fit, and high-resolution imaging of deep tissues. There is a need to develop a high-performance ultrasound probe that is suitable for deep imaging of soft tissues such as the breast, in order to solve many technical pain points in the existing technology. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an ultrasound probe for deep imaging of soft tissues such as the breast and its preparation method, thus solving the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: an ultrasound probe for deep imaging of soft tissues such as the breast, wherein the ultrasound probe is an ultra-thin flexible multilayer composite conformal structure with a total thickness of less than 3mm, and from top to bottom, an encapsulation layer, a flexible circuit connection layer, a backing layer, an upper electrode layer, a piezoelectric element layer, a lower electrode layer, and a double matching layer are stacked sequentially. The piezoelectric element layer is made of Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal material, and is formed into 64 linearly equally spaced one-dimensional phased array independent elements through cutting and filling processes; The upper electrode layer consists of patterned independent electrodes corresponding one-to-one with 64 independent array elements, and the lower electrode layer consists of a full-coverage common ground electrode. The dual-layer matching layer is located on the side of the probe facing the human skin and is used to achieve gradient acoustic impedance matching between the piezoelectric element layer and the human soft tissue. The backing layer is located on the side of the piezoelectric element layer away from human skin, and is used to absorb back-propagating ultrasonic waves and suppress noise interference. The flexible circuit connection layer is electrically connected to the patterned independent electrodes of the upper electrode layer in a one-to-one correspondence, which is used to realize bidirectional signal transmission between the probe and the external ultrasound imaging system. The rated operating frequency of the probe Fixed at 7.0MHz, it can achieve phased array fan-shaped imaging of breast tissue at a depth of 30mm-80mm.

[0009] Preferably, the chemical composition of the Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal is xPb(In1 / 2Nb1 / 2)O3-yPb(Mg1 / 3Nb2 / 3)O3-zPbTiO3+aYb2O3+bBi2O3, where x+y+z=100mol%, x=20mol%, y=40mol%, z=40mol%, a is the molar percentage of Yb2O3 doping, which is 0.8mol%, and b is the molar percentage of Bi2O3 doping, which is 0.5mol%. The single crystal material is polarized along the

[001] crystal orientation, and its comprehensive performance meets the material screening and evaluation formula: solving the core defect that the existing technology cannot simultaneously achieve piezoelectric performance and temperature stability. ; in, This is a comprehensive performance evaluation factor for single crystals, used to quantify and balance piezoelectric properties, high-temperature stability, and dielectric loss. It serves as the basis for screening suitable single crystal materials for deep breast imaging. ; This refers to the piezoelectric coefficient of a single crystal, expressed in pC / N. The value is 2100~2800 pC / N; The reference piezoelectric coefficient is fixed at 1500 pC / N, which is the typical industry value for existing commercial PMN-PT single crystals; The rhombohedral-tetragonal phase transition temperature of a single crystal, in °C. ; The reference phase transition temperature is fixed at 95℃, which is the typical industry value for existing commercial PMN-PT single crystals. For the dielectric loss of a single crystal, single crystal ; The Curie temperature of the single crystal There is no risk of depolarization under high electric field drive and continuous operation with rising temperature.

[0010] Preferably, the geometric parameters of the independent array elements of the one-dimensional phased array satisfy the following formula, which optimizes the grating lobe suppression and imaging aperture for deep breast imaging: solving the problem that the imaging depth and resolution cannot be balanced in the existing technology. ; in, The width of a single array element is expressed in μm. The distance between the centers of adjacent array elements, in μm; The slit width between adjacent array elements, in μm; The rated operating frequency of the probe The corresponding wavelength of ultrasound in human soft tissue, in μm; The longitudinal wave velocity in human soft tissue is fixed at 1540 m / s. The probe's rated operating frequency is fixed at 7.0MHz; The center-to-center distance between adjacent array elements kerf width single element width The array element length is 8mm; low dielectric and low acoustic impedance epoxy resin is filled between adjacent array elements to eliminate lateral vibration coupling and electrical crosstalk between array elements; after the array elements are prepared, an impedance analyzer is used to test each point to screen out qualified array elements with a resonant frequency deviation of less than 3% and a capacitance deviation of less than 2%.

[0011] Preferably, the dual-layer matching layer includes a first matching layer closely attached to the lower electrode layer, and a second matching layer located outside the first matching layer and in direct contact with human skin. Its parameters satisfy the following gradient acoustic impedance matching formula, which is compatible with the piezoelectric single-crystal material to maximize acoustic energy transmission efficiency and improve the signal-to-noise ratio of deep tissue echo signals. ; in, The acoustic impedance of the first matching layer is expressed in MRayl. The acoustic impedance of the second matching layer is expressed in MRayl. The equivalent acoustic impedance of the piezoelectric single crystal is 30~35MRayl; The acoustic impedance of human soft tissue is fixed at 1.5 MRayl. For the first The design thickness of the layer matches the layer. =1 corresponds to the first matching layer. =2 corresponds to the second matching layer, in μm; For ultrasound in the first Longitudinal wave velocity in the layer-matching layer, in m / s; The probe's rated operating frequency is fixed at 7.0MHz; The first matching layer has an acoustic impedance of 8.6 MRayl and a thickness of 92 μm; the second matching layer has an acoustic impedance of 2.2 MRayl and a thickness of 98 μm. The preparation process of the double-layer matching layer is as follows: using epoxy resin as the matrix and zirconium oxide powder as the filler, the mixture is mixed according to the designed volume ratio, centrifuged at 2000 rpm for 10 min to remove bubbles, molded and cured, and double-sided grinding and polished to the target thickness. Then, it is bonded to the lower electrode layer and the piezoelectric element layer in sequence with low viscosity epoxy resin, and cured in a vacuum environment at 65°C for 2 h to complete the integration.

[0012] Preferably, the backing layer is made of a high-attenuation epoxy resin-based composite material with an acoustic impedance of 6.5 MRayl, which matches the acoustic impedance of the piezoelectric single crystal, and the longitudinal wave attenuation coefficient is ≥20 dB / cm@7 MHz; The backing layer is prepared by mixing epoxy resin as the matrix and 1~5μm tungsten powder as a high attenuation filler at a volume ratio of 1:4. It is used to absorb ultrasonic waves emitted from the piezoelectric element layer in the opposite direction, suppress noise interference, and at the same time broaden the -6dB relative bandwidth of the probe. The preparation process is as follows: after mixing the raw materials according to the ratio, centrifuge at 2500rpm for 10min to remove bubbles, pour into a customized mold and cure at 65℃ for 2h, after demolding, grind and polish on both sides to the designed thickness, and then bond to the upper surface of the upper electrode layer with epoxy resin, and complete the integration under vacuum.

[0013] Preferably, the overall thickness of the probe satisfies the following formula, achieving an ultra-thin flexible design with a total thickness of less than 3mm, thus solving the problems that existing rigid probes cannot conform to the curved surface of the human body and thick flexible probes cannot be integrated into wearable systems: ; in, The total thickness of the probe is in mm. ; The thickness of the backing layer is in mm; The thickness of the piezoelectric element layer is in mm; , The thicknesses of the first and second matching layers are in mm. The thickness of the flexible circuit connection layer is in mm. The thickness of the encapsulation layer is in mm; The flexible circuit connection layer uses a 64-channel anisotropic conductive film flexible cable, which is bonded one-to-one with the 64 independent electrodes of the upper electrode layer through a micro-pitch pulse thermoforming process. The bonding process parameters are: temperature 140~160℃, pressure 0.2~0.4MPa, and holding time 10~20s. After bonding, the connection resistance and insulation performance are tested channel by channel to ensure that the single-channel connection resistance is ≤5Ω and the inter-channel insulation resistance is ≥10Ω. 9 Ω; The encapsulation layer uses biocompatible medical-grade epoxy resin or silicone to impregnate or spray the entire probe. After encapsulation, the surface roughness Ra of the skin contact surface is ≤50nm, and the insulation resistance of the encapsulation layer is ≥10 Ω·cm. 12 Ω.

[0014] Preferably, the imaging performance of the probe satisfies the following correlation formula, and is fully compatible with the array element parameters and the operating frequency, achieving an optimal balance between depth and resolution in deep breast imaging: ; in, Axial resolution, in mm, characterizes the probe's ability to resolve minute lesions in the direction of ultrasound propagation. Lateral resolution, in mm, characterizes the probe's ability to resolve minute lesions perpendicular to the direction of ultrasound propagation. The probe's -6dB relative bandwidth, ; The target imaging depth is expressed in mm. The effective aperture of the array element component is expressed in mm. The number of array elements is fixed at 64. The distance between the centers of adjacent array elements; The probe has an axial resolution at an imaging depth of 30mm. Lateral resolution With a maximum imaging depth of ≥80mm and a contrast sensitivity of ≥3dB, it can clearly detect small breast lesions with a diameter of ≥0.3cm. The imaging performance verification process of the probe is as follows: connect the probe to a multi-channel ultrasound imaging system, perform point-by-point testing on a 040GSE ultrasound tissue phantom, record the resolution, imaging depth, and contrast sensitivity data at different depths, and simultaneously complete the thermal stability test to ensure that the surface temperature change is less than 7% after continuous operation at 50V working voltage for 10 minutes.

[0015] A method for preparing an ultrasound probe for deep imaging of soft tissues such as the breast includes the following steps: Step S1: Piezoelectric single crystal preparation and screening. The Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal is grown using the improved vertical Bridgman method. After the grown single crystal rod is sliced, polished, and polarized, its piezoelectric properties, phase transition temperature, and dielectric properties are tested. Single crystal wafers that meet the requirements are screened as piezoelectric element layer substrates through a comprehensive performance evaluation formula. Step S2: Fabrication of one-dimensional phased array elements. The selected single crystal wafer is polished on both sides to the designed thickness. Using a cutting and filling process, 65 equally spaced grooves are cut on the single crystal wafer using a precision dicing machine to form 64 independent array elements according to the parameters. Low-viscosity epoxy resin is filled into the grooves and vacuum degassed and heated to cure. After curing, the surface is ground and polished to complete the fabrication of the array element structure. Step S3: Electrode layer preparation. The piezoelectric wafer with completed array element preparation is ultrasonically cleaned and dried in anhydrous ethanol, acetone and deionized water. A chromium adhesion layer and a gold conductive layer are deposited on the upper and lower surfaces of the wafer in sequence using a vacuum electron beam evaporation process. Then, the upper surface electrode is patterned into an independent electrode corresponding to each of the 64 array elements by a photolithography-lifting process, forming the upper electrode layer and the lower electrode layer. Step S4: Integrate the matching layer and the backing layer. Prepare the first matching layer and the second matching layer according to the parameters. Prepare the backing layer according to the parameters. Bond the backing layer to the upper surface of the upper electrode layer with epoxy resin. Bond the first matching layer and the second matching layer to the lower surface of the lower electrode layer in sequence. Heat and cure in a vacuum environment to form the probe core stacked structure. Step S5: Flexible circuit connection and encapsulation. The 64-channel flexible cable is bonded to the independent electrodes of the upper electrode layer one by one through a pulse thermoforming process. After the signal path connection is completed, the probe is encapsulated with biocompatible materials to control the total thickness to be less than 3mm. Step S6: Performance testing and calibration. Perform electrical, acoustic, thermal stability and imaging performance tests on the packaged probe to verify the imaging performance. Perform laser fine-tuning calibration on array elements with performance parameter deviations that exceed the standard to finally obtain an ultrasonic probe that meets the design requirements.

[0016] Preferably, the piezoelectric single crystal preparation and screening in step S1 specifically includes the following sub-steps: S11: Precursor pre-synthesis: In2O3 and Nb2O5 powders were weighed and mixed in a 1:1 molar ratio, wet-milled in anhydrous ethanol for 12 h, dried, and then kept at 1100℃ in air for 6 h to synthesize a pure-phase InNbO4 precursor; MgO and Nb2O5 powders were weighed and mixed in a 1:2 molar ratio, wet-milled in anhydrous ethanol for 12 h, dried, and then kept at 1200℃ in air for 6 h to synthesize a pure-phase MgNb2O6 precursor. S12: Ingredient preparation and mixing: Weigh Pb3O4, pre-synthesized InNbO4, MgNb2O6, TiO2, Yb2O3, and Bi2O3 powders according to stoichiometric ratio, with Pb3O4 in excess by 0.5~1.0 mol% to compensate for lead volatilization during crystal growth; Place all raw materials into a ball mill jar and wet-mill with zirconium balls at a material-to-ball ratio of 1:3 for 24 hours using anhydrous ethanol as the medium to obtain a uniformly mixed raw material slurry; S13: Pre-calcination synthesis: The raw material slurry is dried in a vacuum environment at 60℃, passed through a 200-mesh sieve, and then calcined in an air atmosphere at 850℃ for 2 hours to allow the raw materials to fully react and form perovskite phase powder. After calcination, it is wet ball-milled again for 24 hours, dried, and sieved to obtain refined synthetic powder. S14: Crystal growth. The synthesized powder is loaded into a platinum crucible with a

[001] crystal orientation seed crystal at the bottom, and placed in a three-temperature zone vertical Bridgman furnace. The powder is heated to 1250℃ in an oxygen atmosphere to melt it. The cooling rate is controlled at 2℃ / h and the crucible descent rate is 0.3~0.5mm / h to carry out crystal growth. After the growth is completed, a single crystal rod is obtained. S15: Annealing and slicing polarization: The single crystal rod is kept at 1200℃ for 10h to eliminate internal stress, and then slowly cooled to room temperature at a rate of 20℃ / h. Then it is cut into wafers of a set thickness along the

[001] crystal direction. The wafers are polished on both sides until the surface roughness Ra≤10nm. After cleaning, a DC electric field of 1kV / mm is applied in a silicone oil medium at room temperature for 10min to polarize the wafers. After standing for 24h, the polarized single wafers are obtained. S16: Performance screening involves cutting multiple test samples from different locations on the single crystal rod and testing the piezoelectric coefficient of each sample. rhombohedral-tetragonal phase transition temperature Dielectric loss Calculated using the comprehensive performance evaluation formula Values, filter out Single-crystal wafers with a value ≥ 2.8 are used as substrates for piezoelectric element layers.

[0017] Preferably, the method for controlling deep breast imaging scanning with the ultrasound probe includes the following steps: Step T1: Conformal fit positioning. After applying medical ultrasound coupling agent to the surface of the second matching layer of the probe, it is attached to the area of ​​the breast to be tested in the subject. The ultra-thin flexible structure achieves conformal fit with the curved surface of the breast skin, and acoustic coupling can be completed without applying external pressure, avoiding compression of breast tissue and deformation of lesions. Step T2: Imaging system connection and parameter preset. Connect the probe to the multi-channel ultrasound imaging system through the flexible circuit connection layer. Preset the transmission and reception timing parameters corresponding to the rated working frequency of 7.0MHz in the system, including the transmission focusing delay, reception dynamic focusing delay, apodization coefficient and beamforming parameters of 64 array elements. At the same time, preset three imaging modes: shallow mode, conventional mode and deep mode. Step T3: Phased array scanning in different modes. Select the corresponding imaging mode according to the detection requirements. The system applies pulse excitation voltages of a specific time sequence to 64 array elements according to a preset time sequence. The array elements generate ultrasound waves based on the inverse piezoelectric effect and emit them to the breast tissue. The system achieves electronic focusing and deflection of the sound beam by controlling the emission delay of each array element, and can complete the fan-shaped imaging of the corresponding depth area without mechanically moving the probe. Among them, the superficial mode corresponds to an imaging depth of 0~30mm, the conventional mode corresponds to an imaging depth of 30~60mm, and the deep mode corresponds to an imaging depth of 60~80mm. Step T4: Standardized scanning of the entire breast region. The scanning position and path of the probe are fixed by a medical honeycomb positioning patch. Multi-position and multi-angle scanning of the entire breast region is completed in sequence. The system automatically collects the echo signal of each position and generates a two-dimensional ultrasound image, while recording the scanning position and angle information. Step T5: 3D reconstruction and lesion identification. The system matches the acquired multiple sets of 2D ultrasound images with the corresponding position and angle information, generates a 3D ultrasound volume image of breast tissue through a 3D reconstruction algorithm, identifies and marks tiny lesions in the image based on the resolution parameters, and outputs the imaging results. Step T6: Image quality verification. The output imaging results are tested for resolution, signal-to-noise ratio, and contrast to verify their axial resolution. Lateral resolution The lesion detection limit meets the design requirements, and the imaging results are cross-compared with those of commercial breast ultrasound probes to ensure the accuracy of the imaging results.

[0018] This invention provides an ultrasound probe for deep imaging of soft tissues such as the breast and its preparation method, which has the following beneficial effects: 1. This invention uses a doped and modified relaxor ferroelectric single crystal material as the piezoelectric element layer. While significantly improving the piezoelectric performance and electromechanical conversion efficiency of the material, it also significantly optimizes the phase transition temperature and Curie temperature of the material, effectively avoiding the depolarization risk under high electric field driving and continuous operation heating scenarios, and ensuring the performance stability and reliability of the probe in long-term clinical use. At the same time, the modified material has better adaptability to high-frequency operating conditions and can still maintain excellent piezoelectric and dielectric properties under high-frequency operating conditions, providing a solid material foundation for high-resolution imaging of the probe.

[0019] 2. This invention, through its multi-layered integrated design, keeps the probe within an ultra-thin thickness range, endowing it with excellent flexibility and conformal capabilities to curved surfaces. It can achieve a pressure-free, tight fit with curved tissues such as the breast, achieving good acoustic coupling without the need for external pressure. This significantly improves patient comfort during the testing process and fundamentally avoids lesion morphology distortion caused by pressure deformation of the examined tissue, ensuring the accuracy of diagnostic results. Simultaneously, the ultra-thin, flexible structure design allows the probe to be adapted to diverse clinical application scenarios such as bedside testing, wearable continuous monitoring, and standardized scanning of the entire breast region, greatly expanding its applicability.

[0020] 3. This invention addresses the core requirements of deep imaging of soft tissues such as the breast by systematically and collaboratively optimizing the phased array elements, dual-layer gradient matching layer, and backing layer of the probe. The dual-layer gradient matching layer design achieves acoustic impedance gradient matching between the piezoelectric element and the human soft tissue, maximizing acoustic energy transmission efficiency and significantly enhancing the signal-to-noise ratio of deep tissue echo signals. The high-attenuation backing layer design effectively absorbs ultrasonic waves propagating backward from the piezoelectric element, suppressing clutter interference and broadening the probe's operating bandwidth. The optimized one-dimensional phased array element design effectively eliminates lateral vibration coupling and electrical crosstalk between elements, ensuring high consistency in element performance. It also achieves optimal matching between imaging penetration depth and lesion resolution, enabling precise detection of minute lesions in deep breast tissue and providing reliable imaging support for the early screening and accurate diagnosis of soft tissue diseases such as breast cancer.

[0021] In summary, this invention achieves stable bidirectional signal transmission between each array element and the external imaging system through a micro-pitch bonding design of the flexible circuit connection layer, ensuring the accuracy of electronic focusing and deflection of the phased array acoustic beam. The use of biocompatible medical-grade materials to encapsulate the entire probe provides effective protection for the internal core structure, ensures biocompatibility for clinical use, and optimizes the smoothness of the skin contact surface, further enhancing acoustic coupling and user comfort. The overall manufacturing process is highly controllable, resulting in consistent product performance and a high yield, providing a solid foundation for large-scale mass production and clinical application. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an ultrasound probe structure for deep imaging of soft tissues such as the breast, as described in this invention. Figure 2 A comparison of the imaging depth between the commercial GEML6-15 and this ultrasonic probe; Figure 3 Comparison of imaging scans at positions 1, 3, and 5 between the commercial GEML6-15 and this ultrasound probe. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figures 1-3 As shown, the present invention provides an ultrasound probe for deep imaging of soft tissues such as the breast and a method for its preparation.

[0025] The ultrasound probe disclosed in this invention for deep imaging of soft tissues such as the breast features an ultra-thin, flexible, multi-layered composite conformal structure design. Through the synergistic combination of novel doped relaxor ferroelectric single crystal materials, gradient-matched acoustic structures, and one-dimensional phased array optimization design, it simultaneously achieves pressure-free conformal fitting of curved breast tissue, high-resolution imaging of deep tissues from 30mm to 80mm, and high stability for long-term clinical use. This solves the core pain point of existing ultrasound probes that cannot simultaneously achieve flexible conformal imaging, deep penetration, and high-resolution imaging.

[0026] Example 1: Structure of an ultrasound probe for deep imaging of soft tissues such as the breast: like Figure 1 As shown, the ultrasound probe for deep imaging of soft tissues such as the breast provided in this embodiment is an ultra-thin flexible multilayer composite conformal structure with a total thickness of less than 3mm. The probe is stacked from top to bottom as follows: encapsulation layer, flexible circuit connection layer, backing layer, upper electrode layer, piezoelectric element layer, lower electrode layer, and double matching layer. The layers are bonded and cured into an integrated structure by vacuum bonding with low-viscosity medical-grade epoxy resin.

[0027] The piezoelectric element layer is the core transducer layer of the probe. It is made of Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal material, and is formed into 64 linearly and equally spaced one-dimensional phased array independent elements through cutting and filling processes. In this embodiment, the chemical composition of the Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal is xPb(In1 / 2Nb1 / 2)O3-yPb(Mg1 / 3Nb2 / 3)O3-zPbTiO3+aYb2O3+bBi2O3, where x+y+z=100mol%, x=20mol%, y=40mol%, z=40mol%, a is the molar percentage of Yb2O3 doping, which is 0.8mol%, and b is the molar percentage of Bi2O3 doping, which is 0.5mol%.

[0028] Single-crystal materials are polarized along the

[001] crystal orientation, and their comprehensive properties satisfy the material screening and evaluation formula: ; in, This is a comprehensive performance evaluation factor for single crystals, used to quantify and balance piezoelectric properties, high-temperature stability, and dielectric loss. It serves as the basis for screening suitable single crystal materials for deep breast imaging. ; The piezoelectric coefficient of a single crystal is expressed in pC / N. The reference piezoelectric coefficient is fixed at 1500 pC / N, which is the typical industry value for existing commercial PMN-PT single crystals; The rhombohedral-tetragonal phase transition temperature of a single crystal is expressed in °C. The reference phase transition temperature is fixed at 95℃, which is the typical industry value for existing commercial PMN-PT single crystals. This represents the dielectric loss of a single crystal.

[0029] The measured properties of the single-crystal material used in this embodiment are: piezoelectric coefficient. rhombohedral-tetragonal phase transition temperature dielectric loss Comprehensive performance evaluation factors Curie temperature It eliminates the risk of depolarization under high electric field drive and continuous operation with rising temperature, thus solving the core defect of existing technologies that cannot simultaneously achieve piezoelectric performance and temperature stability.

[0030] The geometric parameters of the independent elements of a one-dimensional phased array satisfy the following formula, which is used to optimize the grating lobe suppression and imaging aperture for deep breast imaging, thus solving the problem of the inability to balance imaging depth and resolution in existing technologies: ; in, The width of a single array element is expressed in μm. The distance between the centers of adjacent array elements, in μm; The slit width between adjacent array elements, in μm; The rated operating frequency of the probe The corresponding wavelength of ultrasound in human soft tissue, in μm; The longitudinal wave velocity in human soft tissue is fixed at 1540 m / s. The probe's rated operating frequency is fixed at 7.0MHz.

[0031] In this embodiment, the center-to-center spacing between adjacent array elements kerf width single element width The array element length is 8mm; low dielectric and low acoustic impedance epoxy resin is filled between adjacent array elements to eliminate lateral vibration coupling and electrical crosstalk between array elements; after the array elements are prepared, an impedance analyzer is used to test each point to screen out qualified array elements with a resonant frequency deviation of less than 3% and a capacitance deviation of less than 2%, ensuring the performance consistency of the 64 array elements.

[0032] The upper electrode layer consists of patterned independent electrodes corresponding to 64 independent array elements, and the lower electrode layer is a fully covered common ground electrode. In this embodiment, the electrode layer is prepared by vacuum electron beam evaporation process. The bottom layer is a 10nm thick chromium adhesion layer, the top layer is a 300nm thick gold conductive layer, and the upper electrode layer is formed by photolithography-lifting process to form independent lead structures corresponding to the array elements.

[0033] The dual-layer matching layer is located on the side of the probe facing the human skin. It is used to achieve gradient acoustic impedance matching between the piezoelectric element layer and the human soft tissue. Its parameters satisfy the following gradient acoustic impedance matching formula, are compatible with piezoelectric single crystal materials, maximize acoustic energy transmission efficiency, and improve the signal-to-noise ratio of deep tissue echo signals: ; in, The acoustic impedance of the first matching layer is expressed in MRayl. The acoustic impedance of the second matching layer is expressed in MRayl. The equivalent acoustic impedance of the piezoelectric single crystal is 30~35MRayl; The acoustic impedance of human soft tissue is fixed at 1.5 MRayl. For the first The design thickness of the layer matches the layer. =1 corresponds to the first matching layer. =2 corresponds to the second matching layer, in μm; For ultrasound in the first Longitudinal wave velocity in the layer-matching layer, in m / s; The probe's rated operating frequency is fixed at 7.0MHz.

[0034] In this embodiment, the dual-layer matching layer includes a first matching layer that is in close contact with the lower electrode layer, and a second matching layer located outside the first matching layer and in direct contact with human skin. The first matching layer has an acoustic impedance of 8.6 MNayl and a thickness of 92 μm; the second matching layer has an acoustic impedance of 2.2 MNayl and a thickness of 98 μm. Both matching layers are prepared using epoxy resin as the matrix and zirconia powder as the filler. The volume ratio of epoxy resin to zirconia in the first matching layer is 1:3, and the volume ratio of epoxy resin to zirconia in the second matching layer is 1:1.

[0035] The backing layer is located on the side of the piezoelectric element layer away from the human skin. It is used to absorb back-propagating ultrasonic waves and suppress clutter interference, while also widening the operating bandwidth of the probe. In this embodiment, the backing layer is made of a high-attenuation epoxy resin-based composite material with an acoustic impedance of 6.5 MNayl, which matches the acoustic impedance of the piezoelectric single crystal, and a longitudinal wave attenuation coefficient ≥20 dB / cm@7 MHz. The backing layer is prepared by mixing epoxy resin as the matrix and 1~5 μm tungsten powder as a high-attenuation filler at a volume ratio of 1:4.

[0036] The flexible circuit connection layer is electrically connected one-to-one with the patterned independent electrodes of the upper electrode layer to achieve bidirectional signal transmission between the probe and the external ultrasound imaging system. In this embodiment, the flexible circuit connection layer uses a 64-channel anisotropic conductive film flexible cable, which is bonded one-to-one with the 64 independent electrodes of the upper electrode layer through a micro-pitch pulse thermoforming process. The bonding process parameters are: temperature 150℃, pressure 0.3MPa, and holding time 15s. After bonding, the connection resistance and insulation performance are tested channel by channel. The single-channel connection resistance is ≤5Ω, and the inter-channel insulation resistance is ≥10Ω. 9 Ω ensures the stability of signal transmission and the isolation between channels.

[0037] The encapsulation layer uses biocompatible medical-grade silicone to spray-encapsulate the entire probe, providing protection for the internal core structure and ensuring biocompatibility for clinical use. In this embodiment, the surface roughness Ra of the probe's skin contact surface after encapsulation is ≤50nm, and the insulation resistance of the encapsulation layer is ≥10 Ω·cm. 12 Ω; The overall thickness of the probe satisfies the following formula, achieving an ultra-thin and flexible design with a total thickness of less than 3mm: ; in, The total thickness of the probe is in mm. In this embodiment, the measured total thickness is 2.6 mm. The thickness of the backing layer is in mm; The thickness of the piezoelectric element layer is in mm; , The thicknesses of the first and second matching layers are in mm. The thickness of the flexible circuit connection layer is in mm. The thickness of the encapsulation layer is in mm.

[0038] The rated operating frequency of the probe in this embodiment With a fixed frequency of 7.0MHz, the imaging performance satisfies the following correlation formula, perfectly matching the array element parameters and operating frequency, achieving the optimal balance between depth and resolution in deep breast imaging: ; in, Axial resolution, in mm, characterizes the probe's ability to resolve minute lesions in the direction of ultrasound propagation. Lateral resolution, in mm, characterizes the probe's ability to resolve minute lesions perpendicular to the direction of ultrasound propagation. The probe's -6dB relative bandwidth, ; The target imaging depth is expressed in mm. The effective aperture of the array element component is expressed in mm. The number of array elements is fixed at 64. This represents the center-to-center distance between adjacent array elements.

[0039] The probe in this embodiment has a measured -6dB relative bandwidth of 72% and an axial resolution at an imaging depth of 30mm. Lateral resolution With a maximum imaging depth of ≥80mm and a contrast sensitivity of ≥3dB, it can clearly detect small breast lesions with a diameter of ≥0.3cm; after continuous operation at 50V for 10 minutes, the surface temperature change is less than 7%, and the thermal stability meets the requirements for long-term clinical use.

[0040] like Figure 2 As shown in the comparison of the imaging field of view of the probe in this embodiment and the commercial GEML6-15 probe, the probe of this invention, through its one-dimensional phased array fan-forming imaging design, can achieve full field-of-view coverage of breast tissue at a depth of 30mm-80mm. Compared with commercial linear array probes, it has a wider field of view at the same imaging depth, while maintaining high signal-to-noise ratio imaging in the 60-80mm deep region, solving the problem of insufficient deep imaging penetration of commercial probes. The field of view comparison area in the figure is the core depth region for clinical breast examination, 30mm below the skin and fat layer. The effective imaging width of the probe of this invention can reach 50mm, which is far superior to the imaging range of commercial linear array probes at the same depth.

[0041] Example 2: Method for fabricating an ultrasound probe for deep imaging of soft tissues such as the breast: This embodiment provides a method for preparing the ultrasonic probe of Example 1, which specifically includes the following steps: Step S1: Preparation and screening of piezoelectric single crystals: Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystals were grown using a modified vertical Bridgman method. After slicing, polishing, and polarizing the grown single crystal rods, their piezoelectric properties, phase transition temperature, and dielectric properties were tested. Single crystal wafers meeting the requirements were selected as substrates for piezoelectric element layers using a comprehensive performance evaluation formula. The specific steps include the following: S11: Precursor pre-synthesis: In2O3 and Nb2O5 powders were weighed and mixed in a 1:1 molar ratio, wet-milled in anhydrous ethanol for 12 h, dried, and then kept at 1100℃ in air for 6 h to synthesize a pure-phase InNbO4 precursor; MgO and Nb2O5 powders were weighed and mixed in a 1:2 molar ratio, wet-milled in anhydrous ethanol for 12 h, dried, and then kept at 1200℃ in air for 6 h to synthesize a pure-phase MgNb2O6 precursor. S12: Ingredient preparation and mixing: Weigh Pb3O4, pre-synthesized InNbO4, MgNb2O6, TiO2, Yb2O3, and Bi2O3 powders according to stoichiometric ratio, with Pb3O4 in excess by 0.8 mol% to compensate for lead volatilization during crystal growth; Place all raw materials into a ball mill jar and wet-mill with zirconium balls at a material-to-ball ratio of 1:3 for 24 hours at a speed of 300 r / min using anhydrous ethanol as the medium to obtain a uniformly mixed raw material slurry; S13: Pre-calcination synthesis: The raw material slurry is dried in a vacuum environment at 60℃, passed through a 200-mesh sieve, and then calcined in an air atmosphere at 850℃ for 2 hours with a heating rate of 5℃ / min to allow the raw materials to fully react and form perovskite phase powder. After calcination, it is wet ball-milled again for 24 hours, dried, and sieved to obtain refined synthetic powder. S14: Crystal growth. The synthetic powder is loaded into a platinum crucible with a

[001] crystal orientation seed crystal at the bottom and placed in a three-temperature zone vertical Bridgman furnace. The powder is heated to 1250°C in an oxygen atmosphere to melt it. The cooling rate is controlled at 2°C / h and the crucible descent rate is controlled at 0.4mm / h to grow the crystal. After the growth is completed, a single crystal rod with a diameter of 40mm and a length of 50mm is obtained. S15: Annealing and slicing polarization: The single crystal rod is kept at 1200℃ for 10h to eliminate internal stress, and then slowly cooled to room temperature at a rate of 20℃ / h. Then it is cut into wafers of a set thickness along the

[001] crystal direction. The wafers are polished on both sides until the surface roughness Ra≤10nm. After cleaning, a DC electric field of 1kV / mm is applied in a silicone oil medium at room temperature for 10min to polarize the wafers. After standing for 24h, the polarized single wafers are obtained. S16: Performance screening. Five sets of test samples were cut from different locations of the single crystal rod, and the piezoelectric coefficient of each set of samples was tested. rhombohedral-tetragonal phase transition temperature Dielectric loss Calculated using the comprehensive performance evaluation formula Values, filter out Single-crystal wafers with a value ≥ 2.8 are used as substrates for piezoelectric element layers.

[0042] Step S2: Fabrication of one-dimensional phased array elements: The selected single-wafer crystals were polished on both sides to the designed thickness. A cutting and filling process was used, employing a DISCODAD321 precision dicing machine equipped with a 15μm thick synthetic diamond blade. 65 equally spaced grooves were cut into the single-wafer crystals at a dicing speed of 0.25mm / s, forming 64 independent array elements according to the parameters of Example 1. The dicing depth was slightly greater than the designed thickness of the single-wafer crystals for subsequent polishing. Low-viscosity epoxy resin was filled into the grooves and vacuum degassed, then heated to 65°C for 2 hours for curing. After curing, the surface was ground and polished to complete the array element structure preparation. The low-dielectric, low-acoustic-impedance epoxy resin filling between adjacent array elements can eliminate lateral vibration coupling and electrical crosstalk between array elements.

[0043] Step S3: Electrode layer preparation: The piezoelectric wafers with completed array element fabrication were sequentially ultrasonically cleaned for 10 minutes each with anhydrous ethanol, acetone, and deionized water, and then dried with nitrogen. A 10 nm chromium adhesion layer and a 300 nm gold conductive layer were deposited sequentially on the upper and lower surfaces of the wafer using a vacuum electron beam evaporation process. Then, the upper surface electrode was patterned into an independent electrode corresponding to each of the 64 array elements using a photolithography-lifting process, forming an upper electrode layer and a lower electrode layer. The lower electrode layer is a fully covered common ground electrode.

[0044] Step S4: Integration of the matching layer and the backing layer: The first matching layer, the second matching layer, and the backing layer were prepared according to the parameters of Example 1: Matching layer preparation: using epoxy resin as the matrix and zirconia powder as the filler, the mixture is mixed according to the designed volume ratio, centrifuged at 2000 rpm for 10 min to remove bubbles, cured in a mold, and ground and polished on both sides to the target thickness. Backing layer preparation: Epoxy resin is used as the matrix and 1~5μm tungsten powder is used as the filler. The mixture is mixed at a volume ratio of 1:4 and centrifuged at 2500rpm for 10min to remove bubbles. The mixture is then poured into a custom mold and cured at 65℃ for 2h. After demolding, it is ground and polished on both sides to the designed thickness. The backing layer is bonded to the upper surface of the upper electrode layer using low-viscosity epoxy resin, and the first matching layer and the second matching layer are bonded to the lower surface of the lower electrode layer in sequence. The integration is completed by curing in a vacuum environment at 65°C for 2 hours, forming the core stacked structure of the probe.

[0045] Step S5: Flexible circuit connection and packaging: The 64-channel anisotropic conductive film flexible cable is bonded one-to-one with the independent electrodes of the upper electrode layer through a pulse hot pressing process to complete the signal path connection. After that, the entire probe is sprayed and encapsulated with biocompatible medical-grade silicone, with the total thickness controlled to be less than 3mm. After encapsulation, the edges of the probe are trimmed to ensure that the skin contact surface is smooth and burr-free.

[0046] Step S6: Performance Testing and Calibration The packaged probe was tested for electrical performance, acoustic performance, thermal stability, and imaging performance. Electrical performance testing: The impedance spectrum of a single array element was tested using an impedance analyzer. Array elements with a resonant frequency deviation of less than 3% and a capacitance deviation of less than 2% were selected. Array elements with performance parameter deviations exceeding the standard were calibrated by laser fine-tuning. Acoustic performance testing: The probe was connected to the Verasonics Vantage 256 multi-channel ultrasound imaging system, and point-by-point testing was performed on the 040GSE ultrasound tissue phantom to record the resolution, imaging depth, and contrast sensitivity data at different depths. Thermal stability test: The probe surface temperature was monitored using a FLIR thermal imager after continuous operation at 50V for 10 minutes, ensuring that the surface temperature change was less than 7%. The final product is an ultrasonic probe that meets the design requirements.

[0047] Example 3, Method for controlling deep breast imaging scanning with ultrasound probe: This embodiment provides a method for controlling deep breast imaging scanning using an ultrasound probe as described in Embodiment 1, specifically including the following steps: Step T1: Conformal Fitting and Positioning: After uniformly applying medical ultrasound coupling agent to the surface of the second matching layer of the probe, it is attached to the area of ​​the subject's breast to be tested. The ultra-thin flexible structure achieves conformal fit with the curved surface of the breast skin, and acoustic coupling can be completed without applying external pressure, avoiding compression of breast tissue that could cause lesion deformation and ensuring the accuracy of the test results.

[0048] Step T2: Imaging system connection and parameter preset: The probe is connected to a multi-channel ultrasound imaging system via a flexible circuit connection layer. The system is pre-set with transmission and reception timing parameters corresponding to the rated operating frequency of 7.0MHz, including the transmission focusing delay, reception dynamic focusing delay, apodization coefficient, and beamforming parameters for 64 array elements. At the same time, three imaging modes are pre-set: shallow mode, normal mode, and deep mode. The shallow mode corresponds to an imaging depth of 0~30mm, the normal mode corresponds to an imaging depth of 30~60mm, and the deep mode corresponds to an imaging depth of 60~80mm.

[0049] Step T3: Mode-separated phased array scanning: Select the corresponding imaging mode according to the detection requirements. The system applies pulse excitation voltages of a specific time sequence to 64 array elements according to the preset time sequence. The array elements generate ultrasound waves based on the inverse piezoelectric effect and emit them to the breast tissue. The system achieves electronic focusing and deflection of the sound beam by controlling the emission delay of each array element, and can complete the fan-shaped imaging of the corresponding depth area without mechanically moving the probe.

[0050] Step T4: Standardized scan of the entire breast region: The system uses a medical honeycomb positioning patch to fix the scanning position and path of the probe, and sequentially completes multi-position and multi-angle scanning of the entire breast area. The system automatically collects the echo signal of each position and generates a two-dimensional ultrasound image, while recording the scanning position and angle information to provide a positioning basis for subsequent three-dimensional reconstruction.

[0051] Step T5: 3D Reconstruction and Lesion Identification The system matches multiple sets of acquired two-dimensional ultrasound images with corresponding position and angle information, generates a three-dimensional ultrasound volume image of breast tissue through a three-dimensional reconstruction algorithm, identifies and marks tiny lesions in the image based on the resolution parameters of Example 1, and outputs the imaging results.

[0052] Step T6: Image quality verification: The output imaging results were tested for resolution, signal-to-noise ratio, and contrast to verify that their axial resolution, lateral resolution, and lesion detection limit met the design requirements. The results were cross-compared with those of the commercial GEML6-15 breast ultrasound probe to ensure the accuracy of the imaging results.

[0053] like Figure 3 As shown, in the imaging comparison at three different scanning positions (Position 1, Position 3, and Position 5), the imaging clarity and small lesion detection capability of the probe of this invention are consistent with those of the commercial GEML6-15 probe. In breast tissue regions deeper than 30 mm, the imaging signal-to-noise ratio and contrast of the probe of this invention are superior, and it can clearly identify small cystic lesions with a diameter of 0.3 cm, verifying the clinical applicability of this invention in deep breast imaging.

[0054] Example 4: Performance comparison and verification example of the ultrasound probe of the present invention and a commercial breast ultrasound probe: This embodiment compares the performance of the ultrasound probe prepared in Example 1 with that of the commercially available GEML6-15 breast ultrasound linear array probe commonly used in clinical settings. The comparison verifies the performance advantages of this invention in deep breast imaging scenarios. The specific implementation process is as follows: Test samples and test environment: The test samples were divided into two groups: the experimental group consisted of the ultrathin flexible phased array ultrasonic probe of the present invention prepared in Examples 1-2, with a rated operating frequency of 7.0 MHz, a total thickness of 2.6 mm, and a 64-element one-dimensional phased array structure; the control group consisted of the commercial GEML6-15 high-frequency linear array ultrasonic probe, with a nominal operating frequency of 6-15 MHz, which was set to a center frequency of 7.0 MHz during testing to match the operating parameters of the experimental group.

[0055] The testing environment was a clean ultrasound laboratory with a room temperature of 23℃ and a relative humidity of 50%. All tests were performed under the same environmental parameters to avoid interference from environmental factors on the test results.

[0056] The core testing equipment used in this embodiment includes: Verasonics Vantage 256 multi-channel ultrasound imaging system, 040GSE ultrasound tissue phantom, impedance analyzer, FLIRT 640 thermal imager, precision three-dimensional displacement stage, and oscilloscope.

[0057] Among them, the 040GSE ultrasound tissue phantom is an internationally recognized standard phantom for testing ultrasound imaging performance. Its sound velocity and sound attenuation coefficient are consistent with those of human breast soft tissue, which can accurately quantify the core imaging performance of the test probe, such as resolution, imaging depth, and contrast sensitivity.

[0058] Test items and test methods: Electrical performance testing: The impedance spectrum of each element of the two sets of probes was tested using an impedance analyzer. The resonant frequency, anti-resonant frequency, and effective electromechanical coupling coefficient of each element were recorded. The parameter deviation rate of the 64 elements was statistically analyzed to verify the consistency of the element performance. At the same time, the insulation resistance between probe channels and the single-channel connection resistance were tested to verify the reliability of the electrical connection.

[0059] Acoustic and Imaging Performance Testing: Two sets of probes were fixed to a precision three-dimensional displacement stage, perpendicularly contacting the 040GSE ultrasound tissue phantom. Medical ultrasound coupling agent was applied to the contact surfaces to ensure acoustic coupling. Both sets of probes were connected to a Verasonics Vantage 256 ultrasound imaging system, with the same transmit voltage of 50 volts (V) and sampling frequency of 40 MHz. The following tests were performed: Resolution test: The axial and lateral resolutions of the two sets of probes were tested at depths of 10mm, 30mm, 50mm, and 80mm, respectively. The average value was taken for each depth after three tests. Maximum imaging depth test: Gradually increase the imaging depth and record the maximum imaging depth at which the target line can be clearly distinguished by the two sets of probes; Contrast sensitivity test: The ability of two sets of probes to identify targets with different acoustic impedance differences within the phantom is tested, and the smallest acoustic impedance difference that can be clearly identified is recorded, i.e., the contrast sensitivity. Imaging Field of View Test: The effective imaging width of the two sets of probes at a depth of 30mm was tested, and the field of view coverage was compared. The test results were compared with... Figure 2 The image field of view comparison diagram shown Figure 1 To.

[0060] Thermal stability test: Both probes were set to the routine clinical continuous scanning mode and operated continuously for 10 minutes at a working voltage of 50 volts (V). The highest temperature on the probe surface was recorded every minute (min) using a FLIR thermal imager. The temperature change rate after continuous operation was calculated to verify the safety for clinical use.

[0061] Clinical imaging performance verification: Subjects with microcysts (0.3 cm in diameter) in their breasts were selected. With approval from the hospital ethics committee and informed consent from the subjects, two sets of probes were used to perform clinical breast ultrasound imaging. The experimental group used the scanning control method described in Example 3, while the control group used the standard clinical breast ultrasound scanning procedure. Ultrasound images of the same location were acquired in both groups. The detection capability and image clarity of microcysts were compared. The test results were compared with... Figure 3 Multi-position imaging scan comparison shown Figure 1 To.

[0062] Test Results and Analysis: Electrical performance test results: The average resonant frequency of a single element of the probe in the experimental group was 5.9 MHz, the anti-resonant frequency was 8.1 MHz, and the effective electromechanical coupling coefficient keff reached 0.68; the maximum resonant frequency deviation of the 64 elements was 2.1%, and the maximum capacitance deviation was 1.6%, both far exceeding the industry-standard compliance; the average connection resistance of a single channel was 3.2 ohms, and the insulation resistance between channels was greater than 10 ohms. 10 It has a high ohm (Ω) rating and stable and reliable electrical connection performance.

[0063] The effective electromechanical coupling coefficient keff of the control group commercial probe was 0.62, and the maximum deviation of the array element resonant frequency was 3.5%. The probe of this invention is superior to the commercial probe in both electromechanical conversion efficiency and array element consistency.

[0064] Acoustic and imaging performance test results: The core imaging performance of the two sets of probes is compared in the table below: ; The test results show that the probe of this invention is significantly superior to the commercial control group probe in terms of imaging resolution, maximum imaging depth, contrast sensitivity, and imaging field of view. It can still achieve clear imaging at a depth of 80mm, and at the same time has higher resolution at a depth of 30mm. It perfectly solves the technical problem that existing probes cannot achieve both imaging depth and resolution, and can accurately detect tiny lesions deep in the breast.

[0065] Thermal stability test results: In the experimental group, the probe of this invention operated continuously for 10 minutes at 50 volts (V). The initial surface temperature was 22.8℃, and the highest surface temperature after 10 minutes was 24.3℃, with a temperature change rate of 6.6%, less than the design requirement of 7%, and no significant heat generation. In the control group, the commercial probe's surface temperature rose from 23.1℃ to 26.8℃ after 10 minutes of continuous operation, with a temperature change rate of 16.0%. The probe of this invention exhibits superior thermal stability, meeting the needs of long-term continuous scanning and wearable continuous monitoring in clinical settings, and offering higher safety in use.

[0066] Clinical imaging performance verification results: Both probes could detect tiny cystic lesions with a diameter of 0.3 cm in the subject's breast. The lesion boundary of the probe of this invention was clearer, and the contrast between the inside of the lesion and the surrounding tissue was higher. At the same time, due to the flexible conformal fit design, no external pressure was required on the breast, avoiding the problem of lesion deformation due to pressure. The imaging results were more consistent with the actual morphology of the lesion. The commercial rigid probe in the control group required a certain pressure to achieve good acoustic coupling, which easily caused slight deformation of the lesion. Moreover, the signal-to-noise ratio of the image in the deep breast region was lower than that of the probe of this invention.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An ultrasound probe for deep imaging of soft tissues such as the breast, characterized in that, The ultrasonic probe is an ultra-thin, flexible, multi-layer composite conformal structure with a total thickness of less than 3mm. From top to bottom, it consists of an encapsulation layer, a flexible circuit connection layer, a backing layer, an upper electrode layer, a piezoelectric element layer, a lower electrode layer, and a double-layer matching layer. The piezoelectric element layer is made of Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal material, and is formed into 64 linearly equally spaced one-dimensional phased array independent elements through cutting and filling processes; The upper electrode layer consists of patterned independent electrodes corresponding one-to-one with 64 independent array elements, and the lower electrode layer consists of a full-coverage common ground electrode. The dual-layer matching layer is located on the side of the probe facing the human skin and is used to achieve gradient acoustic impedance matching between the piezoelectric element layer and the human soft tissue. The backing layer is located on the side of the piezoelectric element layer away from human skin, and is used to absorb back-propagating ultrasonic waves and suppress noise interference. The flexible circuit connection layer is electrically connected to the patterned independent electrodes of the upper electrode layer in a one-to-one correspondence, which is used to realize bidirectional signal transmission between the probe and the external ultrasound imaging system. The rated operating frequency of the probe Fixed at 7.0MHz, it can achieve phased array fan-shaped imaging of breast tissue at a depth of 30mm-80mm.

2. The ultrasound probe for deep imaging of soft tissues such as the breast according to claim 1, characterized in that, The chemical composition of the Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal is xPb(In1 / 2Nb1 / 2)O3-yPb(Mg1 / 3Nb2 / 3)O3-zPbTiO3+aYb2O3+bBi2O3, where x+y+z=100mol%, x=20mol%, y=40mol%, z=40mol%, a is the molar percentage of Yb2O3 doping, which is 0.8mol%, and b is the molar percentage of Bi2O3 doping, which is 0.5mol%. The single-crystal material is polarized along the [001] crystal orientation, and its comprehensive performance satisfies the material screening and evaluation formula: ； in, As a comprehensive performance evaluation factor for single crystals, ; This refers to the piezoelectric coefficient of a single crystal, expressed in pC / N. The value is 2100~2800 pC / N; The reference piezoelectric coefficient is fixed at 1500 pC / N; The rhombohedral-tetragonal phase transition temperature of a single crystal, in °C. ; The reference phase transition temperature is fixed at 95℃; For the dielectric loss of a single crystal, single crystal ; The Curie temperature of the single crystal There is no risk of depolarization under high electric field drive and continuous operation with rising temperature.

3. An ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 2, characterized in that, The geometric parameters of the independent elements of the one-dimensional phased array satisfy the following formula, which is used to optimize the grating lobe suppression and imaging aperture for deep breast imaging: ； in, The width of a single array element is expressed in μm. The distance between the centers of adjacent array elements, in μm; The slit width between adjacent array elements, in μm; The rated operating frequency of the probe The corresponding wavelength of ultrasound in human soft tissue, in μm; The longitudinal wave velocity in human soft tissue is fixed at 1540 m / s. The probe's rated operating frequency is fixed at 7.0MHz; The center-to-center distance between adjacent array elements kerf width single element width The array element length is 8mm; low dielectric and low acoustic impedance epoxy resin is filled between adjacent array elements to eliminate lateral vibration coupling and electrical crosstalk between array elements; after the array elements are prepared, an impedance analyzer is used to test each point to screen out qualified array elements with a resonant frequency deviation of less than 3% and a capacitance deviation of less than 2%.

4. An ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 3, characterized in that, The dual-layer matching layer includes a first matching layer that is in close contact with the lower electrode layer, and a second matching layer located outside the first matching layer and in direct contact with human skin. Its parameters satisfy the following gradient acoustic impedance matching formula, which is compatible with the piezoelectric single crystal material to maximize acoustic energy transmission efficiency and improve the signal-to-noise ratio of deep tissue echo signals. ； in, The acoustic impedance of the first matching layer is expressed in MRayl. The acoustic impedance of the second matching layer is expressed in MRayl. The equivalent acoustic impedance of the piezoelectric single crystal is 30~35MRayl; The acoustic impedance of human soft tissue is fixed at 1.5 MRayl. For the first The design thickness of the layer matches the layer. =1 corresponds to the first matching layer. =2 corresponds to the second matching layer, in μm; For ultrasound in the first Longitudinal wave velocity in the layer-matching layer, in m / s; The probe's rated operating frequency is fixed at 7.0MHz; The first matching layer has an acoustic impedance of 8.6 MRayl and a thickness of 92 μm; the second matching layer has an acoustic impedance of 2.2 MRayl and a thickness of 98 μm. The preparation process of the double-layer matching layer is as follows: using epoxy resin as the matrix and zirconium oxide powder as the filler, the mixture is mixed according to the designed volume ratio, centrifuged at 2000 rpm for 10 min to remove bubbles, molded and cured, and double-sided grinding and polished to the target thickness. Then, it is bonded to the lower electrode layer and the piezoelectric element layer in sequence with low viscosity epoxy resin, and cured in a vacuum environment at 65°C for 2 h to complete the integration.

5. An ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 4, characterized in that, The backing layer is made of high-attenuation epoxy resin-based composite material with an acoustic impedance of 6.5MRayl, which matches the acoustic impedance of the piezoelectric single crystal, and the longitudinal wave attenuation coefficient is ≥20dB / cm@7MHz; The backing layer is prepared by mixing epoxy resin as the matrix and 1~5μm tungsten powder as a high attenuation filler at a volume ratio of 1:

4. It is used to absorb ultrasonic waves emitted from the piezoelectric element layer in the opposite direction, suppress noise interference, and at the same time broaden the -6dB relative bandwidth of the probe. The preparation process is as follows: after mixing the raw materials according to the ratio, centrifuge at 2500rpm for 10min to remove bubbles, pour into a customized mold and cure at 65℃ for 2h, after demolding, grind and polish on both sides to the designed thickness, and then bond to the upper surface of the upper electrode layer with epoxy resin, and complete the integration under vacuum.

6. An ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 5, characterized in that, The overall thickness of the probe satisfies the following formula, achieving an ultra-thin and flexible design with a total thickness of less than 3mm: ； in, The total thickness of the probe is in mm. ; The thickness of the backing layer is in mm; The thickness of the piezoelectric element layer is in mm; , The thicknesses of the first and second matching layers are in mm. The thickness of the flexible circuit connection layer is in mm. The thickness of the encapsulation layer is in mm; The flexible circuit connection layer uses a 64-channel anisotropic conductive film flexible cable, which is bonded one-to-one with the 64 independent electrodes of the upper electrode layer through a micro-pitch pulse thermoforming process. The bonding process parameters are: temperature 140~160℃, pressure 0.2~0.4MPa, and holding time 10~20s. After bonding, the connection resistance and insulation performance are tested channel by channel to ensure that the single-channel connection resistance is ≤5Ω and the inter-channel insulation resistance is ≥10Ω. 9 Ω; The encapsulation layer uses biocompatible medical-grade epoxy resin or silicone to impregnate or spray the entire probe. After encapsulation, the surface roughness Ra of the skin contact surface is ≤50nm, and the insulation resistance of the encapsulation layer is ≥10 Ω·cm. 12 Ω.

7. An ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 6, characterized in that, The imaging performance of the probe satisfies the following correlation formula, and is fully compatible with the array element parameters and the operating frequency, achieving an optimal balance between depth and resolution in deep breast imaging: ； in, Axial resolution, in mm, characterizes the probe's ability to resolve minute lesions in the direction of ultrasound propagation. Lateral resolution, in mm, characterizes the probe's ability to resolve minute lesions perpendicular to the direction of ultrasound propagation. The probe's -6dB relative bandwidth, ; The target imaging depth is expressed in mm. The effective aperture of the array element component is expressed in mm. The number of array elements is fixed at 64. The distance between the centers of adjacent array elements; The probe has an axial resolution at an imaging depth of 30mm. Lateral resolution With a maximum imaging depth of ≥80mm and a contrast sensitivity of ≥3dB, it can clearly detect small breast lesions with a diameter of ≥0.3cm. The imaging performance verification process of the probe is as follows: connect the probe to a multi-channel ultrasound imaging system, perform point-by-point testing on a 040GSE ultrasound tissue phantom, record the resolution, imaging depth, and contrast sensitivity data at different depths, and simultaneously complete the thermal stability test to ensure that the surface temperature change is less than 7% after continuous operation at 50V working voltage for 10 minutes.

8. A method for preparing an ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 7, characterized in that, Includes the following steps: Step S1: Piezoelectric single crystal preparation and screening. The Yb / Bi co-doped PIN-PMN-PT relaxor ferroelectric single crystal is grown using the improved vertical Bridgman method. After the grown single crystal rod is sliced, polished, and polarized, its piezoelectric properties, phase transition temperature, and dielectric properties are tested. Single crystal wafers that meet the requirements are screened as piezoelectric element layer substrates through a comprehensive performance evaluation formula. Step S2: Fabrication of one-dimensional phased array elements. The selected single crystal wafer is polished on both sides to the designed thickness. Using a cutting and filling process, 65 equally spaced grooves are cut on the single crystal wafer using a precision dicing machine to form 64 independent array elements according to the parameters. Low-viscosity epoxy resin is filled into the grooves and vacuum degassed and heated to cure. After curing, the surface is ground and polished to complete the fabrication of the array element structure. Step S3: Electrode layer preparation. The piezoelectric wafer with completed array element preparation is ultrasonically cleaned and dried in anhydrous ethanol, acetone and deionized water. A chromium adhesion layer and a gold conductive layer are deposited on the upper and lower surfaces of the wafer in sequence using a vacuum electron beam evaporation process. Then, the upper surface electrode is patterned into an independent electrode corresponding to each of the 64 array elements by a photolithography-lifting process, forming the upper electrode layer and the lower electrode layer. Step S4: Integrate the matching layer and the backing layer. Prepare the first matching layer and the second matching layer according to the parameters. Prepare the backing layer according to the parameters. Bond the backing layer to the upper surface of the upper electrode layer with epoxy resin. Bond the first matching layer and the second matching layer to the lower surface of the lower electrode layer in sequence. Heat and cure in a vacuum environment to form the probe core stacked structure. Step S5: Flexible circuit connection and encapsulation. The 64-channel flexible cable is bonded to the independent electrodes of the upper electrode layer one by one through a pulse thermoforming process. After the signal path connection is completed, the probe is encapsulated with biocompatible materials to control the total thickness to be less than 3mm. Step S6: Performance testing and calibration. Perform electrical, acoustic, thermal stability and imaging performance tests on the packaged probe to verify the imaging performance. Perform laser fine-tuning calibration on array elements with performance parameter deviations that exceed the standard to finally obtain an ultrasonic probe that meets the design requirements.

9. A method for preparing an ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 8, characterized in that, The piezoelectric single crystal preparation and screening in step S1 specifically includes the following sub-steps: S11: Precursor pre-synthesis: In2O3 and Nb2O5 powders were weighed and mixed in a 1:1 molar ratio, wet-milled in anhydrous ethanol for 12 h, dried, and then kept at 1100℃ in air for 6 h to synthesize a pure-phase InNbO4 precursor; MgO and Nb2O5 powders were weighed and mixed in a 1:2 molar ratio, wet-milled in anhydrous ethanol for 12 h, dried, and then kept at 1200℃ in air for 6 h to synthesize a pure-phase MgNb2O6 precursor. S12: Ingredient preparation and mixing: Weigh Pb3O4, pre-synthesized InNbO4, MgNb2O6, TiO2, Yb2O3, and Bi2O3 powders according to stoichiometric ratio, with Pb3O4 in excess by 0.5~1.0 mol% to compensate for lead volatilization during crystal growth; Place all raw materials into a ball mill jar and wet-mill with zirconium balls at a material-to-ball ratio of 1:3 for 24 hours using anhydrous ethanol as the medium to obtain a uniformly mixed raw material slurry; S13: Pre-calcination synthesis: The raw material slurry is dried in a vacuum environment at 60℃, passed through a 200-mesh sieve, and then calcined in an air atmosphere at 850℃ for 2 hours to allow the raw materials to fully react and form perovskite phase powder. After calcination, it is wet ball-milled again for 24 hours, dried, and sieved to obtain refined synthetic powder. S14: Crystal growth. The synthesized powder is loaded into a platinum crucible with a [001] crystal orientation seed crystal at the bottom, and placed in a three-temperature zone vertical Bridgman furnace. The powder is heated to 1250℃ in an oxygen atmosphere to melt it. The cooling rate is controlled at 2℃ / h and the crucible descent rate is 0.3~0.5mm / h to carry out crystal growth. After the growth is completed, a single crystal rod is obtained. S15: Annealing and slicing polarization: The single crystal rod is kept at 1200℃ for 10h to eliminate internal stress, and then slowly cooled to room temperature at a rate of 20℃ / h. Then it is cut into wafers of a set thickness along the [001] crystal direction. The wafers are polished on both sides until the surface roughness Ra≤10nm. After cleaning, a DC electric field of 1kV / mm is applied in a silicone oil medium at room temperature for 10min to polarize the wafers. After standing for 24h, the polarized single wafers are obtained. S16: Performance screening involves cutting multiple test samples from different locations on the single crystal rod and testing the piezoelectric coefficient of each sample. rhombohedral-tetragonal phase transition temperature Dielectric loss Calculated using the comprehensive performance evaluation formula Values, filter out Single-crystal wafers with a value ≥ 2.8 are used as substrates for piezoelectric element layers.

10. A method for preparing an ultrasound probe for deep imaging of soft tissues such as the breast, as described in claim 9, characterized in that, The method for controlling deep breast imaging scanning with the ultrasound probe includes the following steps: Step T1: Conformal fit positioning. After applying medical ultrasound coupling agent to the surface of the second matching layer of the probe, it is attached to the area of ​​the breast to be tested in the subject. The ultra-thin flexible structure achieves conformal fit with the curved surface of the breast skin, and acoustic coupling can be completed without applying external pressure, avoiding compression of breast tissue and deformation of lesions. Step T2: Imaging system connection and parameter preset. Connect the probe to the multi-channel ultrasound imaging system through the flexible circuit connection layer. Preset the transmission and reception timing parameters corresponding to the rated working frequency of 7.0MHz in the system, including the transmission focusing delay, reception dynamic focusing delay, apodization coefficient and beamforming parameters of 64 array elements. At the same time, preset three imaging modes: shallow mode, conventional mode and deep mode. Step T3: Phased array scanning in different modes. Select the corresponding imaging mode according to the detection requirements. The system applies pulse excitation voltages of a specific time sequence to 64 array elements according to a preset time sequence. The array elements generate ultrasound waves based on the inverse piezoelectric effect and emit them to the breast tissue. The system achieves electronic focusing and deflection of the sound beam by controlling the emission delay of each array element, and can complete the fan-shaped imaging of the corresponding depth area without mechanically moving the probe. Among them, the superficial mode corresponds to an imaging depth of 0~30mm, the conventional mode corresponds to an imaging depth of 30~60mm, and the deep mode corresponds to an imaging depth of 60~80mm. Step T4: Standardized scanning of the entire breast region. The scanning position and path of the probe are fixed by a medical honeycomb positioning patch. Multi-position and multi-angle scanning of the entire breast region is completed in sequence. The system automatically collects the echo signal of each position and generates a two-dimensional ultrasound image, while recording the scanning position and angle information. Step T5: 3D reconstruction and lesion identification. The system matches the acquired multiple sets of 2D ultrasound images with the corresponding position and angle information, generates a 3D ultrasound volume image of breast tissue through a 3D reconstruction algorithm, identifies and marks tiny lesions in the image based on the resolution parameters, and outputs the imaging results. Step T6: Image quality verification. The output imaging results are tested for resolution, signal-to-noise ratio, and contrast to verify their axial resolution. Lateral resolution The lesion detection limit meets the design requirements, and the imaging results are cross-compared with those of commercial breast ultrasound probes to ensure the accuracy of the imaging results.

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