CN114587326B - Microwave thermo-acoustic microscopic imaging system and method - Google Patents

Abstract

The present invention claims protection for a microwave thermoacoustic microscopy system and method, which belongs to the field of microwave thermoacoustic imaging. Short pulse width microwaves are used to focus and radiate biological tissues to be imaged, and the tissues absorb microwave energy to generate ultrasonic waves, i.e., thermoacoustic signals. The thermoacoustic signals are received by reflective scanning using a point-focused ultrasonic detector, and the signals are amplified and collected by a data acquisition card for image reconstruction. In the process of receiving thermoacoustic signals, short pulse width microwaves are used for focusing and moving synchronously with the ultrasonic detector for reflective scanning, so that the thermoacoustic signals near the detection point are strong and the thermoacoustic signals far away from the detection point are weak, thereby improving the signal-to-noise ratio, making the microwave field in the imaging plane evenly distributed, thereby alleviating the image contrast deterioration caused by the uneven distribution of the microwave field in traditional thermoacoustic imaging, and not limiting the scanning position. The microwave thermoacoustic microscopy system constructed according to the imaging method of the present invention has high signal-to-noise ratio, high contrast, high resolution, and no restrictions on the scanning position, thereby achieving high imaging quality.

Description

Microwave thermoacoustic microscopy system and method

Technical Field

The present invention belongs to the technical field of microwave thermoacoustic imaging, and relates to an imaging method and system, and in particular to a microwave thermoacoustic microscopic imaging method and system.

Background technique

With the development of society and the improvement of living standards, the health awareness of the people has gradually increased, and the demand for the medical market has continued to grow. Compared with clinical manifestations and laboratory tests, medical imaging examinations can provide more objective or intuitive image evidence, and play an increasingly important role in disease diagnosis and efficacy monitoring. Therefore, the strategic layout of the medical imaging industry has been rapidly strengthened, and the scale of the medical imaging market has expanded rapidly. In recent years, conventional clinical imaging examination techniques and methods have been continuously innovated, the corresponding equipment has been continuously improved and perfected, and new imaging techniques and methods have also been continuously emerging. Modern medical imaging equipment has developed from the initial morphological analysis to the comprehensive analysis of human physiological functions, from the original single-modality imaging to the dual-modality or even multi-modality imaging that solves the limitations of a certain type of image information, and from the original two-dimensional planar tomographic images to three-dimensional stereoscopic image modeling, aiming to provide high-quality images and promote the realization of precision medicine.

As an emerging multi-physics hybrid imaging mode, microwave thermoacoustic imaging technology combines the high contrast and deep penetration depth of microwave imaging technology with the high resolution of ultrasound imaging technology. It can present the dielectric functional information of tissues and structural imaging at the same time. It is known as one of the most promising new medical imaging methods. Over the past two decades, microwave thermoacoustic imaging technology has developed rapidly, thanks to the continuous development of microwave radiation sources and ultrasound hardware. It has been used in breast cancer detection, brain imaging, joint imaging, bone imaging, kidney imaging and other related application fields, and has shown its potential in pre-clinical and clinical applications.

However, the imaging resolution reported in current microwave thermoacoustic imaging technology is mostly limited to the millimeter or sub-millimeter level, and the image contrast is deteriorated due to the uneven distribution of the traditional microwave radiation field. Based on the relationship between microwave pulse width, ultrasonic detection bandwidth and thermoacoustic imaging resolution, the relevant team of the University of Electronic Science and Technology of China proposed and built a microwave thermoacoustic microscopy imaging system for plant leaf moisture detection. This system uses a dipole antenna to radiate microwaves and a point-focused ultrasonic detector to transmit and receive acoustic signals. During the signal acquisition process, the antenna remains fixed and the detector moves in a zigzag shape to scan. The antenna radiates microwaves to irradiate the entire imaging target at the same time and irradiates the detector vertically, resulting in a low signal-to-noise ratio. The area between the antenna and the detector is very narrow, which limits the scanning position, especially the in vivo imaging, and there is still a limitation of uneven distribution of the imaging plane field. In order to overcome the shortcomings of current microwave thermoacoustic imaging and thermoacoustic microscopy, the present invention proposes a reflection scanning microwave thermoacoustic microscopy imaging method and system based on short pulse width microwave focusing and making it move synchronously with the point-focused ultrasonic detector.

After searching, the application publication number CN114176554A, a multi-pulse width microwave-excited multi-scale thermoacoustic imaging method and system, belongs to the field of microwave thermoacoustic imaging. By irradiating the biological tissue to be imaged with microwaves of different pulse widths, the biological tissue can be stimulated to produce thermoacoustic signals with different spectral information. The signal can be detected by ultrasonic detectors with different center frequencies, thereby presenting thermoacoustic images of different depths and resolutions. The microwave source outputs microwaves of different pulse widths to irradiate the biological tissue, causing the biological tissue to produce thermoacoustic signals with different spectral information. The thermoacoustic signal is detected by the ultrasonic detector and transmitted to the amplifier. After amplification and filtering by the amplifier, it is collected by the data acquisition card and finally transmitted to the computer. The thermoacoustic signal is reconstructed in the computer to restore the multi-scale thermoacoustic image. The multi-scale thermoacoustic imaging system is more flexible than the traditional thermoacoustic imaging system, and can reconstruct images of biological tissues of different scales to achieve the best imaging depth and resolution. The multi-scale resolution of this patent is still limited to the millimeter and sub-millimeter levels and is still affected by the uneven distribution of traditional microwave radiation fields, resulting in deteriorated image contrast. This patent addresses the limitations of traditional thermoacoustic imaging resolution and uneven field distribution, and uses short-pulse microwave excitation below 66ns combined with a point-focused ultrasonic detector to improve the imaging resolution to the micron level. It uses a focused antenna combined with a point-focused ultrasonic detector for synchronous movement to make the microwave field in the imaging plane evenly distributed, thereby alleviating the related contrast deterioration. At the same time, the microwave focusing area of the focused antenna is combined with the concentric point-focused ultrasonic detection focusing area to improve the signal-to-noise ratio.

CN106073779B, a microwave, thermoacoustic, and color ultrasound dual-mode breast imaging detection device includes a microwave generator, an ultrasound receiving and transmitting device, a transmitting antenna, a sample pool, an ultrasonic transducer, a data acquisition card, and a computer; the ultrasonic receiving and transmitting device includes an ultrasonic signal transmitter and an ultrasonic signal receiver; microwave thermoacoustic imaging, along the transmission direction of the input signal, the microwave generator, the transmitting antenna, and the sample pool are arranged in sequence; color ultrasound imaging, along the transmission direction of the input signal, the ultrasonic signal transmitter, the ultrasonic transducer, and the sample pool are arranged in sequence; microwave thermoacoustic imaging and color ultrasound imaging, along the transmission direction of the output signal, the sample pool, the ultrasonic transducer, the ultrasonic signal receiver, the data acquisition card, and the computer are arranged in sequence. It also relates to a microwave, thermoacoustic, and color ultrasound dual-mode breast imaging detection method. The present invention combines microwave thermoacoustic imaging and color ultrasound imaging to accurately detect the breast, and belongs to the technical field of thermoacoustic imaging and color ultrasound imaging. The microwave thermoacoustic imaging in the microwave thermoacoustic color ultrasound dual-modality breast imaging patent is still affected by the resolution of traditional thermoacoustic imaging and the uneven distribution of the radiation field. This patent uses short-pulse microwave excitation below 66ns and combines the point focusing function of the point focusing ultrasound detector with a center frequency above 15MHz to improve the imaging resolution to the micron level. The focus antenna is combined with the synchronous movement of the point focusing ultrasound detector to make the microwave field in the imaging plane uniformly distributed, thereby alleviating the deterioration of the related contrast and improving the signal-to-noise ratio at the same time. Therefore, this patent can be developed to optimize and improve the existing patent.

In addition, the microwave thermoacoustic color ultrasound dual-modality breast imaging has a certain scope of application, and is intended to use microwave thermoacoustic imaging and ultrasound imaging dual-modality imaging to conduct clinical or preclinical research on related applications; and this patent aims to break through the resolution and contrast limitations of traditional microwave thermoacoustic imaging and promote the development of microwave thermoacoustic imaging technology, and does not involve limitations on the scope of application. At the same time, using an amplifier with ultrasonic transmission/reception functions for ultrasonic imaging can not only perform ultrasonic imaging and thus realize dual-modality imaging in combination with microwave thermoacoustic microscopy, but also use the ultrasonic imaging results as prior information for thermoacoustic signal processing to further improve the quality of thermoacoustic microscopy imaging, and can also cross-validate the ultrasonic imaging results with the conceptual exploratory research results of microwave thermoacoustic microscopy.

Summary of the invention

The present invention aims to solve the above problems of the prior art. A microwave thermoacoustic microscopy imaging system and method is proposed, which has the advantages of high signal-to-noise ratio, high imaging contrast, high resolution, no restriction on scanning parts, etc., thereby achieving high-quality imaging. The technical solution of the present invention is as follows:

A microwave thermoacoustic microscopic imaging system comprises: a microwave generator (1-1), a coaxial line (1-2), a focusing antenna (1-3), a microwave focusing area (1-5), a point-focusing ultrasonic detector (1-6), a patch absorbing material (1-7), a motor controller (1-8), a three-dimensional stepping motor (1-9), an amplifying circuit, a data acquisition card (1-13) and a computer (1-14), wherein the microwave generator (1-1) generates short pulse microwaves or ultrashort pulse microwaves, which are transmitted to the focusing antenna (1-3) through the coaxial line (1-2) to focus and radiate the microwaves to the tissue to be tested (1-4), and the microwave focusing area (1-1) is located at the microstructure of the tissue to be tested. -5) tissue absorbs microwave energy to generate ultrasonic waves, i.e., thermoacoustic signals. The thermoacoustic signals are detected by a point-focused ultrasonic detector (1-6) in a reflective manner. The point-focused ultrasonic detector (1-6) is wrapped with a patch absorbing material (1-7). The point-focused ultrasonic detector (1-6) and the focusing antenna (1-3) are driven by a three-dimensional stepping motor (1-9) controlled by a motor controller (1-8) to synchronously move for multi-point detection. The detected signals are amplified by an amplifying circuit. The amplified signals are collected by a data acquisition card (1-13) and image reconstruction is performed based on the relationship between time domain information and spatial position. The entire process is controlled by a computer (1-14).

Furthermore, the amplification circuit includes a preamplifier (1-10), an amplifier (1-11) with ultrasonic transmission/reception function, and an addition circuit (1-12) which are cascaded in sequence. The preamplifier (1-10) is used for low-noise amplification of weak thermoacoustic signals to ensure a high signal-to-noise ratio. The amplifier (1-11) with ultrasonic transmission/reception function is used for high-power amplification of thermoacoustic signals, and can perform ultrasonic imaging at the same time, thereby combining microwave thermoacoustic microscopy imaging to achieve dual-modal imaging. The addition circuit (1-12) is actually a follower with a certain micro-amplification function, which is used to further improve the signal-to-noise ratio while reducing the number of acquisition averages controlled by the software, thereby saving acquisition time.

Furthermore, the microwave generator (1-1), coaxial line (1-2), focused ultrasonic detector (1-6), motor controller (1-8), three-dimensional stepping motor (1-9), preamplifier (1-10), amplifier with ultrasonic transmission/reception function (1-11) and data acquisition card (1-13) can respectively adopt the equipment with model GRL-VE2085 or GRS-5240FA Chengdu Guorui, A02-07-07-1 or A02-07-07-1.5 Maikebo, V324-SU OLYMPUS, MC600-4B Zhuoli Hanguan, TSA50-C and PSAV400-240ZF Zhuoli Hanguan, AU1291 MITEQ, DPR300 JSR and PCI5122 NI.

Furthermore, the point-focused ultrasound detector (1-6) can perform one-dimensional (2-1), two-dimensional (2-2), and three-dimensional (2-3) detection when driven by a three-dimensional stepping motor (1-9) controlled by a motor controller (1-8); according to the size of the imaging tissue, multiple focusing antennas can be combined with multiple focusing ultrasound detectors, and a multi-channel amplifier and multi-channel data acquisition can be used to perform multi-region synchronous detection to reduce acquisition time; according to specific needs, one-dimensional signal analysis, two-dimensional B-Scan reconstruction, projection plane reconstruction, and three-dimensional stereo image reconstruction can be performed.

A microwave thermoacoustic microscopy imaging method using any of the above systems specifically comprises the following steps: using short pulse width microwaves to focus and irradiate biological tissue to be imaged, the biological tissue to be imaged absorbs microwave energy to generate ultrasonic waves, i.e. thermoacoustic signals, using a point-focused ultrasonic detector to receive the thermoacoustic signals, and during the reflection-type reception of the thermoacoustic signals, the focused microwaves move synchronously with the ultrasonic detector, and the signals are amplified and collected by a data acquisition card for image reconstruction.

Furthermore, the selection basis of the short pulse width microwave is as follows: according to the relationship between microwave pulse width and the deep resolution of thermoacoustic imaging, a microwave pulse width less than the set value of 66ns is selected, which can stimulate microwave tissue to generate a high-frequency thermoacoustic signal of at least 15MHz, thereby increasing the frequency of the thermoacoustic signal, and the rich high-frequency thermoacoustic signal can greatly improve the limiting resolution of microwave thermoacoustic imaging determined by the pulse width; at the same time, according to the relationship between the bandwidth of the ultrasonic detector and the deep resolution of thermoacoustic imaging, in combination with the frequency of the thermoacoustic signal excited by the short pulse width microwave, a high center frequency ultrasonic detector of more than 15MHz is selected to further improve the resolution of thermoacoustic imaging by using the point focusing performance.

Furthermore, short-pulse microwaves are focused to radiate biological tissue to be imaged, and tissue in the microwave focusing area absorbs strong microwave energy to produce a large thermoacoustic signal. The non-microwave focusing area, including biological tissue in the non-focusing area and environmental objects in the non-focusing area, absorbs no microwave energy or absorbs weak microwave energy and produces no or little useless noise. At the same time, the center of the point-focused ultrasound detector needs to coincide with the center of the microwave focusing area, so that the thermoacoustic signal near the detection point is strong and the thermoacoustic signal far away from the detection point is weak, thereby improving the signal-to-noise ratio.

Furthermore, the focused microwave moves synchronously with the ultrasonic probe, so that the microwave field in the imaging plane is evenly distributed, thereby alleviating the image contrast deterioration caused by the uneven distribution of the microwave field in traditional thermoacoustic imaging, thereby improving the imaging contrast.

Furthermore, the point-focused ultrasound detector receives thermoacoustic signals in a reflective manner, and the reflective scanning method is not limited by the area between the antenna and the detector, and does not limit the scanning position, which is conducive to in vivo imaging; compared with the transmission scanning in which the antenna radiates microwaves vertically to the detector wafer, the reflective scanning can reduce the excitation noise generated by the detector being affected by the microwave field, thereby improving the signal-to-noise ratio; the patch absorbing material wrapped around the point-focused detector can absorb the microwave field excitation to further reduce the related noise, while reducing the reflection effect on the microwave transmission process and thereby reducing the impact on the focal area.

Furthermore, an amplifier with ultrasonic transmitting/receiving function can be used for ultrasonic imaging, and then combined with microwave thermoacoustic microscopy for dual-modal imaging; at the same time, the ultrasonic imaging results can be used as prior information for thermoacoustic signal processing to further improve the quality of thermoacoustic microscopy; the ultrasonic imaging results can also be cross-validated with the exploratory research results of microwave thermoacoustic microscopy.

The advantages and beneficial effects of the present invention are as follows:

The present invention utilizes short-pulse width or ultra-short-pulse width microwave excitation combined with a point-focused ultrasonic detector to alleviate the limitation of the resolution of traditional microwave thermoacoustic imaging, thereby realizing microwave thermoacoustic microscopic imaging with a resolution in the micrometer order. According to the relationship between microwave pulse width and the deep resolution of thermoacoustic imaging, a microwave pulse width less than a set value of 66ns is selected, which can stimulate microwave tissue to generate a high-frequency thermoacoustic signal of at least 15MHz, thereby greatly improving the limiting resolution of microwave thermoacoustic imaging determined by the pulse width. At the same time, according to the relationship between the bandwidth of the ultrasonic detector and the deep resolution of thermoacoustic imaging, a high center frequency ultrasonic detector of more than 15MHz is selected in combination with the frequency of the thermoacoustic signal excited by the short-pulse width microwave, and the point-focusing performance is utilized to further improve the resolution of the thermoacoustic imaging.

A focusing antenna is used to focus short-pulse microwaves to radiate the biological tissue to be imaged, and the antenna moves synchronously with the point-focused ultrasound detector for reflective multi-point detection. The center of the microwave focusing area coincides with the center of the point-focused ultrasound detector. The focused microwave moves synchronously with the ultrasound detector, which can make the microwave field in the imaging plane evenly distributed, thereby alleviating the image contrast deterioration caused by the uneven distribution of the microwave field in traditional thermoacoustic imaging, thereby improving the imaging contrast. The tissue in the microwave focusing area absorbs strong microwave energy to produce a large thermoacoustic signal, and the non-microwave focusing area includes biological tissues in the non-focusing area and environmental objects in the non-focusing area. There is no microwave energy absorption or weak microwave energy absorption, which does not generate or generates small useless noise. The center of the point-focused ultrasound detector coincides with the center of the microwave focusing area, making the thermoacoustic signal near the detection point strong and the thermoacoustic signal far away from the detection point weak, thereby improving the signal-to-noise ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of microwave thermoacoustic microscopy imaging according to a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram of one-dimensional, two-dimensional, and three-dimensional detection methods according to an example of the present invention.

FIG. 3 is a diagram showing multi-channel multi-region synchronous detection according to an example of the present invention.

FIG. 4 is a schematic diagram of dual-modality imaging of ultrasound/microwave thermoacoustic microscopy according to an example of the present invention.

Detailed ways

The following will describe the technical solutions in the embodiments of the present invention in detail in conjunction with the accompanying drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention.

The technical solution of the present invention to solve the above technical problems is:

As shown in FIG1 , a microwave thermoacoustic microscopy imaging system comprises: a microwave generator 1-1, a coaxial line 1-2, a focusing antenna 1-3, a microwave focusing area 1-5, a point-focused ultrasonic detector 1-6, a patch absorbing material 1-7, a motor controller 1-8, a three-dimensional stepping motor 1-9, an amplifier circuit, a data acquisition card 1-13 and a computer, wherein the amplifier circuit comprises a preamplifier 1-10, an amplifier 1-11 with ultrasonic transmitting/receiving functions and an adding circuit 1-12 connected in cascade in sequence; the microwave generator 1-1 generates short pulse microwaves or ultrashort pulse microwaves, which are focused and radiated to the measured group by the focusing antenna 1-3 through the coaxial line 1-2. The tissue 1-4, the tissue located in the microwave focusing area 1-5 absorbs microwave energy to generate ultrasonic, i.e., thermoacoustic signals, which are detected by a point-focused ultrasonic detector 1-6 in a reflective manner. The ultrasonic detector 1-6 is wrapped with a patch absorbing material 1-7. The detector 1-6 and the focusing antenna 1-3 are driven by a three-dimensional stepping motor 1-9 controlled by a motor controller 1-8 to synchronously move for multi-point detection. The detected signal is amplified successively by a preamplifier 1-10, an amplifier 1-11 with ultrasonic transmitting/receiving functions, and an adding circuit 1-12. The amplified signal is collected by a data acquisition card 1-13 and used for image reconstruction. The entire process is controlled by a computer 1-14.

The microwave generator 1-1, coaxial line 1-2, focused ultrasonic detector 1-6, motor controller 1-8, three-dimensional stepping motor 1-9, preamplifier 1-10, amplifier with ultrasonic transmitting/receiving function 1-11 and data acquisition card 1-13 can respectively adopt the equipment of model GRL-VE2085 or GRS-5240FA Chengdu Guorui, A02-07-07-1 or A02-07-07-1.5 Maikebo, V324-SU OLYMPUS, MC600-4B Zhuoli Hanguan, TSA50-C and PSAV400-240ZF Zhuoli Hanguan, AU1291MITEQ, DPR300 JSR and PCI5122 NI.

The detector 1-6 can perform one-dimensional 2-1, two-dimensional 2-2, and three-dimensional 2-3 detection under the control of the three-dimensional stepper motor 1-9 controlled by the motor controller 1-8; according to the size of the imaging tissue, multiple focused antennas can be combined with multiple focused ultrasound detectors, and multi-channel amplifiers and multi-channel data acquisition can be used to perform multi-region synchronous detection Figure 3 to reduce the acquisition time. According to specific needs, one-dimensional signal analysis, two-dimensional B-Scan reconstruction, projection plane reconstruction, and three-dimensional stereo image reconstruction can be performed.

Ultrasonic imaging 4-1 is performed using an amplifier with ultrasonic transmitting/receiving functions, and multimodal fusion imaging 4-3 is performed in combination with microwave thermoacoustic microscopy 4-2. At the same time, the ultrasonic imaging results can be used as prior information for thermoacoustic signal processing to further improve the quality of thermoacoustic microscopy 4-4; the ultrasonic imaging results can also be cross-validated with the results of exploratory research on microwave thermoacoustic microscopy 4-5.

Preferably, a microwave thermoacoustic microscopy imaging method specifically includes: using short-pulse microwaves to focus and radiate biological tissue to be imaged, the tissue absorbs microwave energy to generate ultrasonic waves, i.e., thermoacoustic signals, using a point-focused ultrasonic detector to receive the thermoacoustic signals, and during the reflection-type reception of the thermoacoustic signals, the focused microwaves move synchronously with the ultrasonic detector, and the signals are amplified and collected by a data acquisition card for image reconstruction.

Specifically, based on the relationship between microwave pulse width and the deep resolution of thermoacoustic imaging, short pulse width or even ultra-short pulse width microwaves are selected to increase the frequency of thermoacoustic signals. At the same time, based on the relationship between the bandwidth of the ultrasonic detector and the deep resolution of thermoacoustic imaging, a high center frequency ultrasonic detector is selected when the bandwidth covers the frequency of thermoacoustic signals excited by short pulse width microwaves or even ultra-short pulse width microwaves, and the point focusing performance is used to further improve the resolution of thermoacoustic imaging.

Specifically, short-pulse microwaves are focused to radiate biological tissue to be imaged, and tissue in the microwave focusing area absorbs strong microwave energy to produce a large thermoacoustic signal. The non-microwave focusing area includes biological tissue in the non-focusing area and environmental objects in the non-focusing area, which absorb no microwave energy or absorb weak microwave energy and produce no or small useless noise. At the same time, the center of the point-focused ultrasound detector needs to coincide with the center of the microwave focusing area, so that the thermoacoustic signal near the detection point is strong and the thermoacoustic signal far away from the detection point is weak, thereby improving the signal-to-noise ratio.

Specifically, the focused microwave moves synchronously with the ultrasonic probe, so that the microwave field in the imaging plane is evenly distributed, thereby alleviating the image contrast deterioration caused by the uneven distribution of the microwave field in traditional thermoacoustic imaging, thereby improving the imaging contrast.

Specifically, the patch absorbing material wrapped around the point focusing detector can absorb microwave field excitation to reduce related noise, while reducing the reflection effect on the microwave transmission process and thus reducing the impact on the focal area.

Specifically, the point-focused ultrasound probe receives thermoacoustic signals in a reflective manner. The reflective scanning method, especially compared with the projection scanning, is not limited by the area between the antenna and the detector, and does not limit the scanning position, which is conducive to in vivo imaging. Compared with the transmission scanning in which the antenna radiates microwaves vertically to the detector wafer, the reflective scanning can reduce the excitation noise generated by the detector being affected by the microwave field, thereby improving the signal-to-noise ratio.

Specifically, signal amplification uses a front low-noise amplifier, an amplifier with ultrasonic transmitting/receiving function, and an adding circuit to perform cascade amplification to improve the signal-to-noise ratio, reduce the average signal number and thus reduce the acquisition time; at the same time, the amplifier with ultrasonic transmitting/receiving function can also perform ultrasonic imaging, and combine microwave thermoacoustic microscopy imaging to achieve dual-modal imaging.

Specifically, it is necessary to choose a pulse microwave generator with a short pulse width or even an ultra-short pulse width such as a nanosecond pulse width as much as possible, which can stimulate the microwave tissue to produce a high-frequency thermoacoustic signal of at least tens of megahertz. The rich high-frequency thermoacoustic signal can greatly improve the limiting resolution of microwave thermoacoustic imaging; use a focusing antenna such as a coded metasurface to focus microwaves, so that the tissue in the microwave focusing area absorbs strong microwave energy to produce a large thermoacoustic signal, and the tissue in the non-microwave focusing area absorbs weak microwave energy or no microwave energy, thereby generating no noise or little noise, thereby improving the signal-to-noise ratio from the root.

Specifically, for the high-frequency thermoacoustic signal frequency excited by short-pulse or even ultra-short-pulse microwaves, a relatively matching high center frequency ultrasonic detector, such as at least tens of megahertz, is selected, and the point focusing performance is used to further improve the resolution of thermoacoustic imaging; the focusing point of the point-focused detector coincides with the microwave focusing area, so that the large thermoacoustic signal generated by the tissue close to the center of the microwave focusing area is detected, thereby ensuring the high signal-to-noise ratio brought by the antenna focusing area; the point-focused ultrasonic detector and the focusing antenna move synchronously, which can achieve high-resolution and high-signal-to-noise ratio imaging while alleviating the image contrast deterioration caused by the uneven distribution of the radiation field of the traditional antenna; the relative position of the ultrasonic detector and the focusing antenna is reflective, without limiting the scanning position, reducing the excitation noise generated by the antenna radiating microwaves vertically irradiating the detector wafer; the detector is wrapped with patch absorbing material to reduce the mutual influence between it and the microwave.

Specifically, the detector can perform one-dimensional, two-dimensional, and three-dimensional detection under the drive of a three-dimensional stepper motor controlled by a motor controller; according to the size of the imaging tissue, multiple focused antennas can be combined with multiple focused ultrasound detectors, coordinated with multi-channel amplifiers and multi-channel data acquisition, to perform multi-region synchronous detection and reduce acquisition time.

Specifically, an amplifier with ultrasonic transmitting/receiving functions can be used for ultrasonic imaging, and then combined with microwave thermoacoustic microscopy for dual-modal imaging; at the same time, the ultrasonic imaging results can be used as prior information for thermoacoustic signal processing to further improve the quality of thermoacoustic microscopy; the ultrasonic imaging results can also be cross-validated with the exploratory research results of microwave thermoacoustic microscopy.

Specifically, the collected thermoacoustic signals are reconstructed according to different one-dimensional, two-dimensional and three-dimensional detection methods. According to specific needs, one-dimensional signal analysis, two-dimensional B-Scan reconstruction, projection plane reconstruction, and three-dimensional stereo image reconstruction can be performed.

It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

The above embodiments should be understood to be only used to illustrate the present invention and not to limit the protection scope of the present invention. After reading the contents of the present invention, technicians can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims (10)

1. A microwave thermo-acoustic microscopy imaging system, comprising: the microwave generator (1-1), the coaxial line (1-2), the focusing antenna (1-3), the microwave focusing area (1-5), the point focusing ultrasonic detector (1-6), the patch wave absorbing material (1-7), the motor controller (1-8), the three-dimensional stepping motor (1-9), the amplifying circuit, the data acquisition card (1-13) and the computer, wherein the microwave generator (1-1) generates short pulse microwaves or ultrashort pulse microwaves, the microwave focusing antenna (1-3) is used for transmitting microwave focusing radiation to the tested tissue (1-4) through the coaxial line (1-2), the tissue in the microwave focusing area (1-5) absorbs microwave energy to generate ultrasonic waves, namely thermoacoustic signals, the thermoacoustic signals are reflected and detected by the point focusing ultrasonic detector (1-6), the patch wave absorbing material (1-7) is wrapped by the point focusing ultrasonic detector (1-6), the point focusing ultrasonic detector (1-3) is driven by the three-dimensional stepping motor (1-9) controlled by the motor controller (1-8) to move under the driving of the detection card to synchronously detect the probe, the point focusing ultrasonic signals are amplified by the amplifying circuit, the data acquisition signals are reconstructed through the time domain information acquisition circuit, and the spatial reconstruction is carried out according to the acquired data acquisition information, the whole flow is controlled by a computer (1-14).

2. The microwave thermo-acoustic microscopic imaging system according to claim 1, wherein the amplifying circuit comprises a pre-amplifier (1-10), an amplifier (1-11) with an ultrasonic transmitting/receiving function and an adding circuit (1-12) which are sequentially cascaded, the pre-amplifier (1-10) is used for low-noise amplification of weak thermo-acoustic signals to ensure high signal-to-noise ratio, the amplifier (1-11) with the ultrasonic transmitting/receiving function is used for high-power amplification of the thermo-acoustic signals, ultrasonic imaging is carried out at the same time so as to realize bimodal imaging in combination with microwave thermo-acoustic microscopic imaging, the ultrasonic imaging result is used as priori information to carry out thermo-acoustic signal processing to further improve the quality of thermo-acoustic microscopic imaging, and the ultrasonic imaging result is also subjected to cross verification with the research result of microwave thermo-acoustic microscopic imaging; the addition circuit (1-12) is a follower with a certain micro-amplification function, and is used for further improving the signal to noise ratio and reducing the acquisition average times controlled by software so as to save the acquisition time.

3. A microwave thermo-acoustic microscopic imaging system according to claim 1, characterized in that the microwave generator (1-1), coaxial line (1-2), focused ultrasound probe (1-6), motor controller (1-8), three-dimensional stepper motor (1-9), pre-amplifier (1-10), amplifier with ultrasound transmitting/receiving function (1-11) and data acquisition card (1-13) are devices of the model GRL-VE2085 or GRS-5240FA to the national Rui, A02-07-07-1 or A02-07-07-1.5 Micobbo, V324-SU OLYMPUS, MC600-4B Zhuo Lihan light, TSA50-C and PSAV400-240ZF Zhuo Lihan light, AU1291 MITEQ, DPR300 JSR and PCI5122 NI, respectively.

4. A microwave thermo-acoustic microscopic imaging system according to any of the claims 1, characterized in that the point focusing ultrasound detector (1-6) can perform one-dimensional (2-1), two-dimensional (2-2) and three-dimensional (2-3) detection under the drive of a three-dimensional stepping motor (1-9) controlled by a motor controller (1-8); according to the imaging tissue size, a plurality of focusing antennas are combined with a plurality of focusing ultrasonic detectors, and multi-region synchronous detection is carried out by taking a multi-channel amplifier and multi-channel data acquisition as cooperation, so that the acquisition time is reduced; and carrying out one-dimensional signal analysis, two-dimensional B-Scan reconstruction, projection plane reconstruction and three-dimensional stereo image reconstruction according to specific requirements.

5. A method of microwave thermo-acoustic microscopy using the system of any one of claims 1, comprising the steps of: the method comprises the steps of utilizing short pulse width microwaves to focus and radiate biological tissues to be imaged, absorbing microwave energy by the biological tissues to be imaged to generate ultrasonic waves, namely thermoacoustic signals, utilizing a point focusing ultrasonic detector to receive the thermoacoustic signals, enabling the focusing microwaves to synchronously move along with the ultrasonic detector in the process of reflectively receiving the thermoacoustic signals, and acquiring the signals for image reconstruction by a data acquisition card after the signals are amplified.

6. The method of claim 5, wherein the short pulse width microwaves are selected based on: according to the relation between the microwave pulse width and the deep resolution of the thermoacoustic imaging, the microwave pulse width smaller than the set value of 66ns is selected, and microwave tissues can be stimulated to generate high-frequency thermoacoustic signals of at least 15MHz, so that the frequency of the thermoacoustic signals is improved, and the abundant high-frequency thermoacoustic signals can greatly improve the limit resolution of the microwave thermoacoustic imaging, which is determined by the pulse width; meanwhile, according to the relation between the bandwidth of the ultrasonic detector and the deep resolution of the thermo-acoustic imaging, under the condition of matching with the frequency of the thermo-acoustic signal excited by the short pulse width microwave, the point focusing ultrasonic detector with the high center frequency of more than 15MHz is selected, and the resolution of the thermo-acoustic imaging is further improved by utilizing the point focusing performance.

7. The method of claim 5, wherein the short pulse width microwave focused radiation irradiates the biological tissue to be imaged, the microwave focal zone tissue absorbs the strong microwave energy to produce a loud thermoacoustic signal, the non-microwave focal zone includes non-focal zone biological tissue and non-focal zone environmental items do not have microwave energy absorption or weak microwave energy absorption and do not produce or produce small unwanted noise; the center of the simultaneous point focusing ultrasonic detector needs to coincide with the center of the microwave focusing area, so that the thermo-acoustic signal near the detection point is strong and the thermo-acoustic signal far from the detection point range is weak, thereby improving the signal-to-noise ratio.

8. The method of claim 5, wherein the focused microwaves move synchronously with the ultrasound probe to uniformly distribute the microwave field in the imaging plane to mitigate image contrast deterioration caused by uneven distribution of the microwave field in conventional thermo-acoustic imaging, thereby improving imaging contrast.

9. The method of claim 5, wherein the point focusing ultrasound probe receives thermo-acoustic signals in a reflective manner, the reflective scanning mode is not limited by the area between the antenna and the probe, the scanning position is not limited, and living body imaging is facilitated; compared with the transmission type scanning, the reflection type scanning method has the advantages that compared with the transmission type scanning method that the antenna radiates microwaves and irradiates the wafer of the detector vertically, excitation noise generated by the influence of microwave fields on the detector can be reduced, and the signal to noise ratio is improved; the patch wave absorbing material is wrapped around the simultaneous point gathering detector, so that microwave field excitation can be absorbed to further reduce related noise, and reflection influence on the microwave transmission process is reduced to reduce influence on a focusing area.

10. The method of micro-acoustic imaging of claim 5, wherein an amplifier with an ultrasonic transmitting/receiving function is used for ultrasonic imaging, and further, a micro-acoustic imaging of micro-wave is combined for bimodal imaging; meanwhile, the ultrasonic imaging result is used as priori information to carry out thermo-acoustic signal processing, so that the thermo-acoustic microscopic imaging quality is further improved; the ultrasound imaging results were also cross-validated with the microwave thermo-acoustic microscopy imaging exploratory study results.