Compensation type photoacoustic receiver and method

Abstract

The invention discloses a compensation type photoacoustic receiver and a method. The receiver comprises a receiver shell, a hollow transducer, a compensation module and a planar transducer; the hollow transducer is arranged in the receiver shell, the hollow transducer comprises a hollow cylinder backing layer and an annular high-frequency piezoelectric element, the hollow cylinder backing layer and the receiver shell are coaxially arranged, and the annular high-frequency piezoelectric element is attached to the concave surface of the bottom of the hollow cylinder backing layer; the compensation module is sleeved in the hollow transducer and comprises a prism group and cylindrical transparent glass, the cylindrical transparent glass is coaxially positioned in a cavity of the hollow cylindrical backing layer, and the prism group is fixed at the top of the cylindrical transparent glass; and the planar transducer is arranged at the top of the compensation module. According to the method, lost sound signals can be compensated, and the collected sound signals can be more complete through superposition of the sound signals of the two sound fields, so that the detection sensitivity of a receiver and the quality of image reconstruction are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoacoustic imaging, and in particular relates to a compensating photoacoustic receiver and method. Background Art

[0002] Photoacoustic imaging is a biomedical imaging technology that combines the principles of optics and ultrasound. It uses the photoacoustic effect, that is, the sound waves generated after tissue or material absorbs the energy of laser pulses, to obtain structural and functional information of biological tissues. Photoacoustic imaging has high resolution and deep tissue penetration, so it has potential important applications in the field of medical imaging.

[0003] A key component of photoacoustic imaging is the photoacoustic receiver, which is used to receive the acoustic signals generated by the photoacoustic effect and convert these acoustic signals into electrical signal outputs for signal processing and image reconstruction. The patent application with application number CN202110085865.2 discloses a photoacoustic / ultrasound dual-modal high-frequency probe based on the curvature of an ellipsoid. This technical solution extends the depth of field through the shape of the ellipsoid and improves the imaging resolution. The cylindrical structure of the invention has a hole in the middle to facilitate the transmission of incident lasers and the reception of echo ultrasonic signals. However, the disadvantage is that the cavity structure it adopts lacks piezoelectric materials inside and cannot receive acoustic signals, causing part of the acoustic signal to be lost, thereby affecting the detection sensitivity of the receiver and the imaging quality of the system. The patent application with application number CN201810515835.9 discloses a transparent ultrasonic transducer. The invention can seamlessly integrate optical and ultrasonic components and has ultra-high optical transparency, allowing more light to pass through, which is beneficial to improving imaging quality. However, there are technical challenges in manufacturing a transparent ultrasonic transducer with high transparency and good acoustic performance. It is necessary to develop new materials and designs, such as transparent piezoelectric units, transparent electrodes, transparent backing layers, etc., and the preparation process is complicated and costly.

[0004] In addition, the cavity structure used by the hollow transducer commonly used in current photoacoustic imaging technology makes it easier for optical signals to propagate, but there are also defects such as loss of acoustic signals, which seriously affects the integrity of signal collection and the quality of image reconstruction. Summary of the invention

[0005] In order to solve at least one of the shortcomings of the prior art, the present invention provides a compensating photoacoustic receiver with a simple structure and reasonable construction. The compensation module of the photoacoustic receiver can compensate for the lost sound signal. The superposition of the sound signals of the two sound fields can make the collected sound signal more complete, thereby improving the detection sensitivity of the receiver and the quality of image reconstruction.

[0006] In order to achieve the purpose of the present invention, the present invention provides a compensated photoacoustic receiver, comprising a receiver housing, a hollow transducer, a compensation module and a planar transducer;

[0007] The hollow transducer is arranged in the receiver housing, and comprises a hollow cylindrical backing layer and an annular high-frequency piezoelectric element. The hollow cylindrical backing layer is coaxially arranged with the receiver housing, the cylinder is made of transparent glass, and the bottom is concave for focusing the acoustic signal, and the annular high-frequency piezoelectric element is fitted on the bottom concave surface of the hollow cylindrical backing layer;

[0008] The compensation module is mounted in the hollow transducer, and includes a prism group and a cylindrical transparent glass. The cylindrical transparent glass is coaxially located in the cavity of the hollow cylindrical backing layer, and the prism group is fixed on the top of the cylindrical transparent glass.

[0009] The planar transducer is arranged on the top of the compensation module.

[0010] The hollow transducer is a hollow structure, which can be fitted with a fixed compensation module.

[0011] Preferably, the annular high-frequency piezoelectric element is attached to the concave surface at the bottom of the hollow cylindrical backing layer, and the two are coaxial.

[0012] The prism group is bonded to the transparent cylindrical glass, the transparent cylindrical glass is sleeved in the hollow cylindrical backing layer; the planar transducer is attached to the top of the compensation module.

[0013] The hollow cylindrical backing layer is coaxially sleeved with the compensation module and the receiver shell.

[0014] Preferably, the receiver housing is made of aluminum.

[0015] Preferably, the hollow transducer is arranged inside the receiver housing, and the gap between the receiver housing and the hollow transducer is filled with a glue layer.

[0016] Preferably, the glue layer uses UV light curing glue and resin waterproof glue; first, the receiver shell and the hollow cylindrical backing layer are placed in a coaxial position, and filled and fixed with UV light curing glue; then the bottom is filled with resin waterproof glue. The glue layer not only can achieve the connection between the two, but also has a waterproof effect.

[0017] Preferably, the annular high-frequency piezoelectric element is adhered to the concave surface of the bottom of the hollow cylindrical backing layer by epoxy resin, which is flat and wrinkle-free, and the two are coaxial. The bottom of the hollow cylindrical backing layer is set as a concave surface, and the annular high-frequency piezoelectric element has a convex surface, which is fitted on the concave surface of the hollow cylindrical backing layer.

[0018] Preferably, the hollow cylindrical backing layer is made of epoxy resin-tungsten powder material, and the preparation process includes: adding epoxy resin curing agent to epoxy resin in a ratio of 1:0.35, pouring 66% to 71% tungsten powder and 6% boron nitride powder, stirring and mixing until gray liquid, then placing the sample in a vacuum box to remove bubbles and air, and finally pouring the sample into a mold, placing it in a constant temperature oven for heating and curing. The mass fraction of tungsten powder is about 66% to 71%, and its acoustic attenuation coefficient and acoustic impedance value are relatively high, with an acoustic impedance value of 5.5 MRayls to 6.6 MRayls, and an acoustic attenuation coefficient of 15.7 dB / cm to 16.3 dB / cm. The acoustic signal emitted by biological tissue is partially received by the high-frequency piezoelectric element, and a small part passes through the high-frequency piezoelectric element and is then reflected by the hollow cylindrical backing layer to the high-frequency piezoelectric element for reception, which improves the efficiency of receiving acoustic signals, thereby improving the detection sensitivity of the receiver, and is also used to support, isolate and protect the high-frequency piezoelectric element.

[0019] Preferably, the annular high-frequency piezoelectric element adopts a wide-band PVDF material and is formed by making the PVDF piezoelectric film into a ring shape. The annular high-frequency piezoelectric element is used to focus and receive sound signals; the PVDF piezoelectric film has a small acoustic impedance value, which is between 1.5 MRayls and 3.0 MRayls, and can achieve better acoustic impedance matching with water and human tissue without the need for a matching layer.

[0020] Preferably, the cylindrical transparent glass of the compensation module is fitted into the hollow transducer and bonded to the hollow cylindrical backing layer by epoxy resin; the curvature radius of the concave surface at the bottom of the cylindrical transparent glass is R=f(1-1 / n), where n is the ratio of the propagation speed of the sound signal in the glass and in the water, and f is the focusing focal length.

[0021] Preferably, the bottom of the prism group of the compensation module is bonded to the top of the cylindrical transparent glass by ultrasonic glue, and the centers of the prism group and the cylindrical transparent glass are aligned.

[0022] Preferably, the prism group is used for light reflection and sound transmission, and comprises two metal-coated prisms, and the two prisms are fixed to each other.

[0023] Further preferably, the prism group is composed of two aluminum-coated prisms bonded together by UV light-curing glue. The acoustic impedance of aluminum is about 17.1 MRalys, and the acoustic impedance of glass is about 18.9 MRayls. Aluminum and glass have good acoustic impedance matching, and the attenuation of ultrasonic waves inside this material is small, which is conducive to the transmission of ultrasonic waves.

[0024] Preferably, the planar transducer is attached to the top of the cylindrical transparent glass to receive the acoustic signal focused by the cylindrical transparent glass. The planar transducer is made of piezoelectric ceramic material, which has a high electromechanical coupling coefficient and is characterized by high sensitivity and high stability.

[0025] Preferably, the planar transducer and the prism assembly are bonded together by ultrasonic glue.

[0026] The present invention also provides a signal receiving method, using the above-mentioned photoacoustic receiver, the method comprising: placing the photoacoustic receiver on biological tissue, irradiating a laser pulse beam to a prism group, the beam is reflected by the prism group, then passes through a transparent cylindrical glass, and irradiates the biological tissue, the biological tissue absorbs the laser pulse energy, and generates an acoustic signal;

[0027] A part of the generated acoustic signal is focused and received by the annular high-frequency piezoelectric element to form a first part of the focused acoustic field; another part of the acoustic signal is focused by the compensation module, passes through the prism group, and then is received by the planar transducer to form a second part of the focused acoustic field;

[0028] The first part of the focused sound field is converted into an electrical signal output by the annular high-frequency piezoelectric element, and the second part of the focused sound field is converted into an electrical signal output by the planar transducer.

[0029] Compared with the prior art, the present invention has at least the following advantages and effects:

[0030] (1) Only part of the acoustic signal is received by a single hollow transducer, and the rest of the acoustic signal is lost from the middle cavity. The present invention adds a compensation module in the cavity of the hollow transducer, which can focus the lost acoustic signal to the planar transducer, thereby realizing the compensation reception of the acoustic signal.

[0031] (2) In the present invention, a part of the generated acoustic signal is received by the annular high-frequency piezoelectric element of the receiver to form a first part of the focused acoustic field; the other part passes through the compensation module and is received by the planar transducer to form a second part of the focused acoustic field; the acoustic signals of the two different acoustic fields work together to help compensate for the lost acoustic signal, making the acquired acoustic signal information more complete, thereby improving the detection sensitivity of the receiver and the quality of image reconstruction.

[0032] (3) The present invention provides a photoacoustic signal compensation receiver with a simple structure and can be well matched with a photoacoustic imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the appearance structure of a compensated photoacoustic receiver provided in an embodiment of the present invention;

[0034] Figure 2 A schematic cross-sectional structure diagram of a compensated photoacoustic receiver provided by an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of the explosion structure of a compensated photoacoustic receiver provided by an embodiment of the present invention;

[0036] Explanation of the accompanying figures: 1 is a planar transducer; 2 is a prism group; 3 is a cylindrical transparent glass; 4 is a receiver shell; 5 is a hollow cylindrical backing layer; 6 is an annular high-frequency piezoelectric element; wherein the prism group 2 and the cylindrical transparent glass 3 constitute a compensation module; wherein the hollow cylindrical backing layer 5 and 6 annular high-frequency piezoelectric elements constitute a hollow transducer. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, a photoacoustic signal compensation receiver provided by the present invention includes a receiver housing 4, a hollow transducer, a compensation module and a planar transducer 1. The compensation module includes a prism group 2 and a cylindrical transparent glass 3. The transparent glass has good light transmittance, which is convenient for focusing and transmitting optical signals, and the glass material has good mechanical stability and chemical stability; the hollow transducer includes a hollow cylindrical backing layer 5 and an annular high-frequency piezoelectric element 6, and the compensation module is mounted in the hollow transducer.

[0039] The planar transducer 1 is bonded to the prism group 2 by ultrasonic glue; the cylindrical transparent glass 3 is inserted into the cavity of the hollow cylindrical backing layer 5, and the cylindrical transparent glass 3 and the hollow cylindrical backing layer 5 are bonded together by epoxy resin, and the bottoms of the two are aligned; the prism group 2 and the transparent cylindrical glass 3 are bonded together by ultrasonic glue, the prism group 2 is located on the top of the transparent cylindrical glass 3, and the centers of the two are aligned; the bottom of the hollow cylindrical backing layer 5 is set as a concave surface, and the annular high-frequency piezoelectric element 6 is bonded to the bottom concave surface of the hollow cylindrical backing layer 5 by epoxy resin, and the two are coaxial; the receiver housing 4 and the hollow cylindrical backing layer 5 are filled and fixed by a glue layer.

[0040] The prism group 2 includes two metal-coated prisms, and the two prisms are bonded together by ultraviolet light curing adhesive. In some embodiments of the present invention, the prism group 2 includes two aluminum-coated prisms, and the two prisms are isosceles right triangles (one angle is 90 degrees, and the other two angles are 45 degrees), and the inclined surfaces of the two prisms are bonded together to form a cube.

[0041] In some embodiments of the present invention, the receiver housing 4 is made of aluminum, which can effectively reduce the surrounding electromagnetic influence.

[0042] In some embodiments of the present invention, the glue layer filled between the receiver housing 4 and the hollow cylindrical backing layer 5 includes UV-curing glue and resin waterproof glue, wherein the receiver housing 4 and the hollow cylindrical backing layer 5 are first placed in a coaxial position and filled and fixed with UV-curing glue; then the bottom is filled with resin waterproof glue. The glue layer not only enables the connection between the two to be achieved, but also has a waterproof effect.

[0043] In some embodiments of the present invention, the curvature radius of the concave bottom surface of the cylindrical transparent glass 3 is R=f(1-1 / n), where n is the ratio of the propagation speed of the acoustic signal in the glass and in the water, and f is the focusing focal length.

[0044] In some embodiments of the present invention, the hollow cylindrical backing layer 5 is made of epoxy resin-tungsten powder material. Further preferably, the preparation steps of the hollow cylindrical backing layer 5 include: adding epoxy resin curing agent to epoxy resin according to a preset ratio, pouring 66% to 71% of tungsten powder and 6% of boron nitride powder, stirring and mixing until gray liquid, obtaining a sample, and then placing the sample in a vacuum box to remove bubbles and air, and finally pouring the sample into a mold, placing it in a constant temperature oven for heating and curing.

[0045] In some embodiments of the present invention, the annular high-frequency piezoelectric element 6 is made of a broadband PVDF material and is formed by making a PVDF piezoelectric film into an annular shape. In a specific example, the inner diameter of the annular high-frequency piezoelectric element 6 is 4 mm, the outer diameter is 8 mm, and the center frequency is 50 MHz.

[0046] A signal receiving method, wherein the compensated photoacoustic receiver of the present invention is placed on the upper part of biological tissue, a laser light source emits a series of laser pulses, irradiates the prism group 2, the light beam is reflected by the prism group 2, then passes through the transparent cylindrical glass 3, and irradiates the biological tissue, the biological tissue absorbs the laser pulse energy, and generates an acoustic signal.

[0047] A part of the generated sound signal is focused and received by the annular high-frequency piezoelectric element 6 of the receiver to form a first partial focused sound field; another part of the sound signal is focused by the compensation module (transparent cylindrical glass 3), passes through the prism group 2, and then is received by the planar transducer 1 to form a second partial focused sound field; the first partial focused sound field is converted into an electrical signal output by the annular high-frequency piezoelectric element 6, and the second partial focused sound field is converted into an electrical signal output by the planar transducer 1.

[0048] For the hollow transducer, the acoustic signal is only received by the annular high-frequency piezoelectric element 6 of the hollow transducer, and the remaining acoustic signal is lost from the middle cavity of the hollow cylindrical backing layer 5; by adding a compensation module to the middle cavity of the hollow transducer, the lost acoustic signal in the sound field can be received by the planar transducer 1 to compensate for the lost acoustic signal.

[0049] The acoustic signals from two different sound fields work together to help compensate for the lost acoustic signals, making the acquired acoustic signal information more complete, thereby obtaining more accurate and informative images and improving the receiver detection sensitivity and image reconstruction quality.

[0050] The present invention aims to solve the problem of acoustic signal loss caused by the hollow structure in the photoacoustic imaging technology based on the hollow transducer. The cavity structure of the existing hollow transducer makes it easy for the light signal to pass through, but due to the lack of piezoelectric material in its cavity, it is impossible to receive the acoustic wave signal in the cavity, which leads to the loss of the acoustic wave signal in the cavity. In the compensated photoacoustic receiver provided by the aforementioned embodiment of the present invention, the hollow transducer can realize the light transmission function through its cavity structure, and the compensation module can collect the acoustic signal lost in the hollow structure through the reflective and sound-transmitting prism group and the light-transmitting and sound-transmitting cylindrical glass, and finally receive it by the planar transducer. The joint action of the hollow transducer and the compensation module can enable the entire device to compensate for the lost acoustic signal, realize the complete acoustic signal reception, and improve the integrity of the acoustic signal, thereby improving the detection sensitivity of the receiver and the quality of image reconstruction.

[0051] Although the embodiments disclosed in the present invention are as above, the above contents are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A compensated photoacoustic receiver, characterized in that: It includes a receiver housing, a hollow transducer, a compensation module and a planar transducer; The hollow transducer is arranged in the receiver housing, and the hollow transducer comprises a hollow cylindrical backing layer and an annular high-frequency piezoelectric element. The hollow cylindrical backing layer is arranged coaxially with the receiver housing, and the annular high-frequency piezoelectric element is arranged on the bottom concave surface of the hollow cylindrical backing layer. The compensation module is mounted in the hollow transducer, and includes a prism group and a cylindrical transparent glass. The cylindrical transparent glass is coaxially located in the cavity of the hollow cylindrical backing layer, and the prism group is fixed on the top of the cylindrical transparent glass. The planar transducer is arranged on the top of the compensation module.

2. A compensated photoacoustic receiver according to claim 1, characterized in that: The prism group is used for reflecting light and transmitting sound, and includes two metal-coated prisms, and the two prisms are fixed to each other.

3. A compensated photoacoustic receiver according to claim 1, characterized in that: The hollow cylindrical backing layer is made of epoxy resin-tungsten powder material.

4. A compensated photoacoustic receiver according to claim 1, characterized in that: The annular high-frequency piezoelectric element is made of PVDF material.

5. A compensated photoacoustic receiver according to claim 1, characterized in that: The receiver housing is made of aluminum.

6. A compensated photoacoustic receiver according to claim 1, characterized in that: A glue layer is used to fill the space between the receiver shell and the hollow cylindrical backing layer.

7. A compensated photoacoustic receiver according to claim 6, characterized in that: The glue layer includes ultraviolet light curing glue and resin waterproof glue. The receiver shell and the hollow cylindrical backing layer are filled and fixed by ultraviolet light curing glue, and the bottom is filled by the resin waterproof glue.

8. A compensated photoacoustic receiver according to claim 1, characterized in that: The prism set is aligned with the center of the cylindrical clear glass.

9. A compensated photoacoustic receiver according to any one of claims 1 to 8, characterized in that: The formula for the curvature radius of the concave surface at the bottom of the cylindrical transparent glass is R=f(1-1 / n), where n is the ratio of the propagation speed of the acoustic signal in the glass and in the water, and f is the focusing focal length.

10. A signal receiving method, characterized in that: Using the photoacoustic receiver described in any one of claims 1 to 9, the method comprises: placing the photoacoustic receiver on biological tissue, irradiating a laser pulse beam to a prism group, the beam is reflected by the prism group, then passes through a transparent cylindrical glass, and irradiates the biological tissue, the biological tissue absorbs the laser pulse energy, and generates an acoustic signal; A part of the generated acoustic signal is focused and received by the annular high-frequency piezoelectric element to form a first part of the focused acoustic field; another part of the acoustic signal is focused by the compensation module, passes through the prism group, and then is received by the planar transducer to form a second part of the focused acoustic field; The first part of the focused sound field is converted into an electrical signal output by the annular high-frequency piezoelectric element, and the second part of the focused sound field is converted into an electrical signal output by the planar transducer.

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