A miniature interventional ultrasound catheter transducer based on impedance-mismatched backing

Abstract

The application discloses a small-sized interventional ultrasonic catheter transducer design based on impedance anti-matching backing. The small-sized interventional ultrasonic catheter transducer comprises, from bottom to top, a packaging layer, an FPC circuit, a second anti-matching layer, a first anti-matching layer, a piezoelectric layer, a first matching layer, a second matching layer and an acoustic lens layer. The total thickness of the second and first anti-matching layers is close to the thickness of the piezoelectric layer, and the extremely high reflectivity of the second and first anti-matching layers makes almost no acoustic wave energy be transmitted into the backing layer, so that the traditional thick backing structure can be eliminated, and the size of the transducer is greatly reduced. The reduction of the size of the transducer provides a large amount of available space for laying of the FPC circuit, so that the small-sized interventional ultrasonic catheter transducer can have a more reasonable design in space. The proposed catheter transducer design based on impedance anti-matching backing provides a feasible scheme for miniaturization of the interventional ultrasonic catheter transducer.

Description

Technical Field

[0001] This invention relates to the field of medical ultrasound testing equipment technology, and in particular to a small interventional ultrasound transducer and the design and manufacturing method of the ultrasound transducer. Background Technology

[0002] With the increasing popularity of minimally invasive interventional surgery, the application of ultrasound image-guided technology in this field has become particularly crucial. However, existing ultrasound imaging technologies face numerous challenges. Surface ultrasound is limited by its small acoustic window, insufficient deep resolution, and the significant impact of factors such as obesity, gas, and bone on image quality. Transcavitary ultrasound, such as intracardiac ultrasound and cardiovascular ultrasound, while allowing direct observation of intracavitary structures, still offers insufficient field of view. Rigid laparoscopic ultrasound, due to its rigid tube design, causes significant trauma and is inflexible in operation. Therefore, developing a small interventional ultrasound catheter transducer capable of providing precise, real-time high-resolution imaging guidance is of great significance for advancing minimally invasive interventional surgery.

[0003] However, the design of miniature interventional ultrasound catheter transducers faces a significant challenge: optimizing the transducer structure within a very small space to balance imaging quality and catheter size. Traditional ultrasound transducer structures include an acoustic matching layer, a piezoelectric layer, and a backing layer. The piezoelectric layer, as the core component, is responsible for both ultrasound transmission and reception. The acoustic matching layer addresses the acoustic impedance mismatch between the piezoelectric layer and human tissue to improve sound wave transmission efficiency. However, the backing layer accounts for over 80% of the thickness in traditional structures to eliminate sound waves entering the backing layer and avoid image artifacts. While this design ensures imaging quality, it severely restricts the miniaturization of the transducer.

[0004] To achieve transducer miniaturization without sacrificing image quality, traditional structures must be optimized. Therefore, this patent proposes a miniaturized interventional ultrasound catheter transducer based on impedance-matched backing technology. This technology, through a carefully designed backing structure, effectively reduces the thickness of the backing layer while maintaining its function of eliminating acoustic waves and preventing image artifacts. This not only significantly reduces the overall size of the transducer, making it more suitable for interventional catheters, but also maintains or even improves image quality, providing strong support for precise minimally invasive surgery. Summary of the Invention

[0005] This invention aims to address the problem of miniaturization in existing ultrasonic catheter transducers while maintaining imaging quality, and provides a miniaturized interventional ultrasonic catheter transducer based on an impedance-matched backing. The transducer's thickness can be controlled to 1-2 mm, and its width to within 3 mm, facilitating its passage through tissue spaces and proximity to the surgical area via interventional routes, enabling high-resolution real-time imaging guidance.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a small interventional ultrasound catheter transducer based on impedance anti-matching backing. Its basic structure, from bottom to top, includes an FPC circuit, a second anti-matching layer, a first anti-matching layer, a piezoelectric layer, a first matching layer, a second matching layer, an acoustic lens layer, and an external encapsulation layer.

[0008] The FPC circuit adopts a flexible design to connect the electrodes of each array of piezoelectric layers, and can be bent inside the transducer to adapt to the shape of the conduit, achieving a reliable connection with the external connector. Its total thickness is controlled at the level of hundreds of micrometers to ensure the compactness of the overall size of the transducer. The FPC circuit and the bottom encapsulation layer constitute the equivalent backing layer of the transducer.

[0009] The anti-matching layer is designed to increase the reflection coefficient between the piezoelectric layer and the equivalent backing layer, thereby effectively reducing the ultrasonic energy entering the equivalent backing layer. The anti-matching layer design has two different implementation methods: one is an anti-matching structure based on equivalent ultra-low acoustic impedance, including a double-layer structure and a single-layer structure; the other is an anti-matching structure based on equivalent ultra-high acoustic impedance, usually a single-layer structure. This design significantly reduces the thickness of the backing layer while ensuring imaging quality, thereby achieving miniaturization of the transducer.

[0010] The piezoelectric layer, as a core component, is used to receive voltage excitation signals and generate forward and backward ultrasonic waves. The forward ultrasonic waves are ultrasonic waves transmitted from the piezoelectric layer to the matching layer. The backward ultrasonic waves are ultrasonic waves transmitted from the piezoelectric layer to the anti-matching layer. The piezoelectric layer can also be used to receive ultrasonic waves and generate electrical signals.

[0011] The first and second matching layers are used to solve the problem of interfacial acoustic impedance mismatch between ultrasound waves and human tissue and piezoelectric layer. By optimizing the material and thickness of the matching layers, the transmission efficiency of ultrasound waves is improved, thereby increasing the bandwidth of the transducer and ensuring the clarity of the imaging.

[0012] The acoustic lens layer is used to focus the acoustic beam of the duct transducer in the elevation direction to enhance the transducer's sensitivity and further improve image quality.

[0013] The encapsulation layer protects the transducer and its internal structure, while also providing excellent insulation to ensure the transducer's safety and lifespan.

[0014] Optionally, in the dual-layer anti-matching structure based on equivalent ultra-low acoustic impedance, the thickness of the first anti-matching layer and the second anti-matching layer is generally 0.1-0.4 times the wavelength of the ultrasonic wave, preferably 0.25 times the wavelength; the ultrasonic wave wavelength is the ultrasonic wave wavelength when the ultrasonic wave is transmitted to the functional layer.

[0015] Optionally, the anti-matching based on equivalent ultra-low acoustic impedance can be a single-layer structure or a double-layer structure. If it is a single-layer structure, the first anti-matching layer uses a low acoustic impedance material, such as epoxy resin, polyvinyl chloride, and polypropylene, while the second anti-matching layer has zero thickness, but the backing is required to be a thicker high acoustic impedance material. If it is a double-layer structure, the first anti-matching layer also uses a low acoustic impedance material, while the second anti-matching layer uses a high acoustic impedance material, such as elemental metals, steel, and tungsten steel, without the need for a backing layer.

[0016] Optionally, the anti-matching based on equivalent ultra-high acoustic impedance is generally a single-layer structure. The anti-matching layer uses a high acoustic impedance material, such as elemental metal, steel, or tungsten steel, and its thickness is generally 0.1-0.3 times the wavelength of the ultrasonic wave within the material. The anti-matching structure based on equivalent ultra-high acoustic impedance requires a piezoelectric layer thickness of 0.25 times the ultrasonic wave wavelength to satisfy the "fixed-free" resonance relationship of the piezoelectric layer.

[0017] Optionally, the piezoelectric layer material includes, but is not limited to, piezoelectric ceramics, piezoelectric single crystals, and / or piezoelectric composite materials.

[0018] Optionally, the thickness of each matching layer is typically 0.15-0.35 times the ultrasonic wavelength.

[0019] Optionally, the acoustic lens material includes, but is not limited to, low-velocity rubber materials and high-velocity polystyrene materials.

[0020] Optionally, the shape and type of the ultrasonic transducer with power output and imaging capabilities include, but are not limited to, single-element planar type, single-element focusing type, planar array type, and curved array type.

[0021] The beneficial effects of this invention are as follows: This invention designs a small interventional ultrasound catheter transducer based on an impedance-matched backing, which greatly hinders the penetration efficiency of ultrasonic energy at the backing, thus eliminating the need for a thick backing layer to attenuate backward ultrasonic waves, thereby eliminating the traditional thick backing structure and greatly reducing the transducer size; at the same time, by optimizing the matching layer parameters to improve the bandwidth of the catheter transducer, its imaging quality is only slightly lower than that of traditional ultrasound transducers; the impedance-matched backing structure described in this invention is not only applicable to small interventional ultrasound catheter transducers, but also to other application scenarios where probe size is limited. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a basic structural diagram of an ultrasonic catheter transducer based on impedance-matched backing provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of a product provided for an embodiment of the present invention;

[0025] Symbol explanation: 1-FPC circuit, 2-second anti-matching layer, 3-first anti-matching layer, 4-piezoelectric layer, 5-first matching layer, 6-second matching layer, 7-acoustic lens layer, 8-encapsulation layer, 9-electrode solder point, 10-handle, 11-direction wheel, 12-sheath, 13-catheter transducer. Detailed Implementation

[0026] 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 specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. 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.

[0027] This invention aims to provide a compact interventional ultrasound catheter transducer based on an impedance-matched backing. By employing an impedance-matched backing structure, this transducer significantly reduces the penetration efficiency of backward ultrasound energy, thus eliminating the need for a thick backing layer to eliminate backward ultrasound. This design not only reduces the overall size of the transducer but also provides support and sensitivity enhancement to the piezoelectric layer through the impedance-matched backing structure, thereby improving the imaging depth and contrast of the ultrasound catheter transducer.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 This is a basic structural diagram of a small interventional ultrasound catheter transducer based on impedance-matched backing, provided in an embodiment of the present invention. Figure 1 As shown, the ultrasonic transducer in this embodiment includes, in order from bottom to top, an FPC circuit 1, a second anti-matching layer 2, a first anti-matching layer 3, a piezoelectric layer 4, a first matching layer 5, a second matching layer 6, an acoustic lens layer 7, an external encapsulation layer 8, and array electrode solder joints 9.

[0030] The FPC circuit 1 is used to connect each array of transducers to each channel of the host receiver, and has the functions of electrical signal excitation and pulse echo signal reception. It has the characteristics of small size and flexibility.

[0031] The second anti-matching layer 2 is generally made of a high acoustic impedance material. In this specific embodiment, tungsten steel is selected, which has an acoustic impedance of about 97M ayl and a thickness of 0.24λ.

[0032] The first anti-matching layer 3 is generally made of a low acoustic impedance material, so that its equivalent acoustic impedance with the second anti-matching layer 2 becomes extremely low. In this specific embodiment, epoxy resin is selected, with an acoustic impedance of 2.7Mayl and a thickness of 0.24λ.

[0033] In this embodiment, the piezoelectric layer 4 is made of PZT-5H ceramic material to meet the high bandwidth requirements. It consists of two micro-elements in one array, and its acoustic impedance is approximately 20 MRayl.

[0034] The first matching layer 5 and the second matching layer 6 are used to increase the transmission of sound waves between the piezoelectric layer 4 and the medium, thereby improving the bandwidth and transmission efficiency of the ultrasonic transducer. In this specific embodiment, the first matching layer 5 is made of a mixture of tungsten powder and epoxy resin with an acoustic impedance of 8.5 MNayl, and the second matching layer 6 is made of epoxy resin with an acoustic impedance of 2.7 MNayl. Both have a thickness of 0.24λ.

[0035] The acoustic lens layer 7 is used to focus the acoustic field of the catheter transducer, making its energy more concentrated and improving the quality of ultrasound imaging. It also serves as insulation and protection.

[0036] The outer encapsulation layer 8 is used to protect the conduit transducer and provide a certain strength support for the transducer.

[0037] The electrode solder joint 9 is used to connect each transducer element to each solder joint of the FPC circuit 1, ensuring electrical contact with high stability.

[0038] Figure 2 This is a schematic diagram of a product provided for an embodiment of the present invention. For example... Figure 2 As shown, the product in this embodiment includes a handle 10, a steering wheel 11, a sheath 12, and a catheter transducer 13.

[0039] The handle 10 provides an operable platform for the operator and integrates the steering wheel 11 and the sheath 12.

[0040] The directional wheel 11 is used to control the change of the shape and orientation of the conduit. In this embodiment, it is operated by mechanical transmission. The main control methods are the rotation of the rotating parts, the turning of the steering rod, and the bending of the deformable parts.

[0041] The sheath 12 is used to provide access for the catheter during surgery or interventional imaging, and includes a main body, an adjustable bend, and a distal bend.

[0042] The catheter transducer 13 is used to perform uniform and high-resolution ultrasound imaging of lesions in the human body, and it has the characteristic of small size.

[0043] The present invention relates to a small interventional ultrasound catheter transducer based on impedance anti-matching, which features a small size, uses an impedance anti-matching backing structure, has a head size of about 1 mm, and a transducer diameter of less than 3 mm, thus meeting the miniaturization requirements of interventional catheter transducers.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A miniature interventional ultrasound catheter transducer based on impedance-matched backing, characterized in that, It includes, from bottom to top, an encapsulation layer, an FPC circuit, a second anti-matching layer, a first anti-matching layer, a piezoelectric layer, a first matching layer, a second matching layer, and an acoustic lens layer; The encapsulation layer serves as insulation and protection, and its width is less than or equal to 3 mm, and its total thickness is less than or equal to 2 mm. The FPC circuit is used to connect each array of the transducer to each channel of the host receiver. The FPC circuit adopts a flexible design and can be bent inside the transducer to adapt to the shape of the catheter, and achieves a reliable connection with the external connector. The second anti-matching layer and the first anti-matching layer are used to eliminate the traditional thick backing layer, reduce the size of the interventional ultrasound catheter transducer, and prevent echo artifacts caused by insufficient backing thickness in the transducer design, which seriously affect the imaging quality. The second anti-matching layer is made of tungsten carbide, with an acoustic impedance of 97M ayl and a thickness of 0.24λ. The first anti-matching layer is made of low acoustic impedance epoxy resin with an acoustic impedance of 2.7 MRayl and a thickness of 0.24λ. The piezoelectric layer is used to receive electrical signal excitation to generate ultrasonic waves, and to generate electrical signals by receiving ultrasonic waves. The piezoelectric layer array contains 8 to 512 elements, each of which can be controlled to transmit and receive ultrasonic waves; the -6dB center frequency of the ultrasonic transducer is within the range of 4 to 40MHz; and a piezoelectric layer material with broadband characteristics is selected. The -6dB center frequency refers to the average of the upper and lower limits of the -6dB spectrum for each operating frequency band. The piezoelectric layer material with broadband characteristics is PZT-5H ceramic material with an acoustic impedance of 20 MRayl. The first matching layer and the second matching layer are used to increase the transmission degree of ultrasonic waves, improve the transducer sensitivity, improve the ultrasonic waveform, and increase the bandwidth of the ultrasonic transducer. The first matching layer is made of a mixture of tungsten powder and epoxy resin, with an acoustic impedance of 8.5 MRayl and a thickness of 0.24λ. The second matching layer is made of epoxy resin material with an acoustic impedance of 2.7 MRayl and a thickness of 0.24λ. The acoustic lens layer serves as insulation and protection, and also focuses the sound field in the elevation direction of the transducer, reducing the adverse effects caused by the large diffusion angle.

2. The miniature interventional ultrasound catheter transducer based on impedance-matched backing according to claim 1, characterized in that, The encapsulation layer uses a flexible material such as rubber or plastic, and its shape is selected from one of cylindrical, square, and ellipsoidal shapes.

3. The miniature interventional ultrasound catheter transducer based on impedance-matched backing according to claim 1, characterized in that, The thickness of the FPC circuit is less than 100μm; the line spacing is determined according to the specific frequency and is less than or equal to 0.3mm; the length is equal to the number of arrays multiplied by the line spacing; the width is the width of the FPC itself, and the array width is reduced to less than 3mm by folding.

4. The miniature interventional ultrasound catheter transducer based on impedance-matched backing according to claim 1, characterized in that, The acoustic lens material is selected from rubber or epoxy resin, and its shape is selected from one of the following: spherical, ellipsoidal, parabolic, and hyperboloid.

Images