Super-resolution microwave thermo-acoustic imaging method and device based on nonlinear saturated response absorption

Abstract

This invention relates to a super-resolution microwave thermoacoustic imaging method and apparatus based on nonlinear saturated response absorption, belonging to the field of medical imaging and nondestructive testing technology. The invention utilizes pulse-width modulated microwave signals to excite biological tissues to generate microwave thermoacoustic signals. These signals are received by an ultrasonic transducer and collected and stored for microwave thermoacoustic image reconstruction. During imaging, different pulse widths are sequentially switched to excite the tissue under test, resulting in microwave thermoacoustic images under different pulse widths. Multiple sets of microwave thermoacoustic images are then fused and analyzed to obtain a super-resolution microwave thermoacoustic image. This method achieves selective imaging of biological tissues of different sizes with high contrast, overcoming the limitations of traditional microwave thermoacoustic imaging resolution caused by factors such as contrast. This invention achieves super-resolution microwave thermoacoustic imaging of tissue components of different sizes, and microwave thermoacoustic imaging has good biological tissue penetration performance, thus showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of medical imaging and non-destructive testing technology, specifically relating to a microwave thermoacoustic imaging technology, and particularly a super-resolution microwave thermoacoustic imaging method and device based on nonlinear saturated response absorption. Background Technology

[0002] Microwave thermoacoustic imaging technology is based on the microwave thermoacoustic effect. It is a non-invasive biomedical imaging method where pulsed microwaves irradiate biological tissue, causing the tissue to absorb microwave energy and undergo thermoelastic expansion, which in turn generates ultrasound waves. By detecting these ultrasound waves, an image of the microwave absorption distribution within the tissue can be reconstructed. This technology is achieved through the following core processes: pulsed energy excitation, selective energy absorption and instantaneous thermoelastic expansion, broadband ultrasound emission, microwave thermoacoustic signal acquisition, and image reconstruction. The spatial resolution of traditional microwave thermoacoustic imaging is mainly limited by the bandwidth and center frequency of the ultrasound detector, and its diffraction limit is usually at the half-wavelength level (hundreds of micrometers). For microstructures smaller than this scale (such as microvessels and early tumor lesions), it is impossible to clearly distinguish them, which seriously affects its application in precision medicine. Furthermore, existing super-resolution technologies (such as stimulated emission depletion microscopy (STED), photoactivated localization microscopy (PALM), and stochastic optical reconstruction microscopy (STORM)) are complex, costly, or unsuitable for in vivo deep imaging. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a microwave thermoacoustic super-resolution imaging technology that does not rely on complex optical systems or special markers, and can break through the diffraction limit to achieve resolution of objects at the subwavelength scale.

[0004] The technical problem addressed by this invention is solved by the following technical solution:

[0005] This invention first proposes a super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption, comprising: firstly, acquiring microwave thermoacoustic signals of samples under different pulse width excitations; reconstructing microwave thermoacoustic images of a single pulse width using an imaging algorithm; obtaining microwave thermoacoustic images of all pulse widths through parallel processing; then analyzing the microwave thermoacoustic signal intensity variation curve of each pixel in the microwave thermoacoustic image under different pulse widths; and clustering or color encoding the image according to the saturation feature parameters of different pixels.

[0006] The saturation feature parameters include the saturation threshold pulse width, the slope of the linear region, and the amplitude of the saturation region. The pulse width corresponding to the inflection point where the slope of the microwave thermoacoustic signal intensity change curve changes from linear to gentle is the saturation pulse width of the sample at that pixel.

[0007] Furthermore, the method specifically includes the following sub-steps:

[0008] Step 1: Set the initial short pulse width, and apply microwave or laser pulses with the same energy but continuously increasing pulse width to the object being detected; the microwave frequency, pulse power, and pulse repetition frequency are the same;

[0009] Step 2: Use an ultrasonic detector to receive the microwave thermoacoustic signal generated by each pulse excitation, and use a microwave thermoacoustic image reconstruction algorithm to reconstruct the microwave thermoacoustic image corresponding to each pulse width;

[0010] Step 3: For each pixel in the microwave thermoacoustic image, extract its signal amplitude under different pulse widths to obtain a signal amplitude-pulse width relationship curve;

[0011] Step 4: Analyze the signal amplitude-pulse width relationship curve and extract the saturation feature parameters for each pixel;

[0012] Step 5: Using saturation feature parameters, generate a new super-resolution image, where pixel values ​​represent the size information or small size probability of that point.

[0013] Furthermore, the sequence of laser pulses includes at least 10 different pulse widths.

[0014] Furthermore, the microwave thermoacoustic image reconstruction algorithm is a back projection algorithm, a delay and overlay algorithm, a filtered back projection algorithm, a time reversal algorithm, or compressed sensing.

[0015] Furthermore, the super-resolution image is generated using thresholding, size mapping, or curve decomposition methods, and the specific generation process is as follows:

[0016] Threshold filtering: Select a microwave thermoacoustic image acquired under a short pulse width in a pulse sequence. In this image, the microwave thermoacoustic signal of the target absorber with a size smaller than the threshold has been saturated, while the signal of larger objects is still increasing linearly. The small-sized structures smaller than the threshold are highlighted by the image processing algorithm.

[0017] Size mapping: The value of each pixel is converted into the corresponding feature size through a pre-defined linear relationship, thereby generating a size distribution map;

[0018] Curve decomposition: The entire microwave thermoacoustic image sequence is regarded as a data cube. Taking advantage of the fact that objects of different sizes have different growth curves, blind source separation or deconvolution algorithms are used to separate the different size components that contribute to the microwave thermoacoustic signal, and finally synthesize a super-resolution image with a resolution far exceeding that of a single image.

[0019] Another aspect of the present invention provides a super-resolution microwave thermoacoustic imaging device based on nonlinear saturated response absorption, including a microwave excitation module, an ultrasonic coupling module, a microwave thermoacoustic signal data acquisition module, and a real-time image reconstruction and analysis module.

[0020] The microwave excitation module includes a pulse width modulation microwave source and a microwave antenna. The pulse width modulation microwave source generates microwaves with different pulse widths, which are transmitted to the antenna via a coaxial cable to radiate the microwaves to the sample under test.

[0021] The ultrasonic coupling module is an ultrasonic transducer. The sample under test absorbs microwave energy to generate ultrasonic waves, i.e., microwave thermoacoustic signals. Microwave thermoacoustic signals under microwave excitation with different pulse widths are detected by the ultrasonic transducer and transmitted to the microwave thermoacoustic signal data acquisition module.

[0022] The microwave thermoacoustic signal data acquisition module includes a data acquisition card and a multi-channel microwave thermoacoustic signal amplifier; the microwave thermoacoustic signal is amplified by the amplifier, and the amplified signal is acquired by the data acquisition card to obtain microwave thermoacoustic data under different pulse width excitation, which is then transmitted to the real-time image reconstruction and analysis module.

[0023] The real-time image reconstruction and analysis module controls the microwave excitation module, the ultrasonic coupling module, and the microwave thermoacoustic signal data acquisition module. Then, based on the relationship between the temporal information and spatial location in the microwave thermoacoustic data, it uses a microwave thermoacoustic image reconstruction algorithm to reconstruct a single-pulse-width microwave thermoacoustic image, obtaining a multi-pulse-width microwave thermoacoustic image. Then, it analyzes the microwave thermoacoustic signal intensity variation curve of each pixel in the microwave thermoacoustic image under different pulse widths. Based on the saturation feature parameters of different pixels, it performs clustering or color coding on the image to distinguish biological tissues of different sizes.

[0024] Furthermore, the microwaves with different pulse widths generated by the pulse width modulation microwave source are generated by the same variable pulse width microwave source or by multiple pulse width microwave sources; the microwaves with different pulse widths need to maintain the same center frequency and peak power; the pulse width modulation microwave source has real-time feedback and programmable control functions for pulse width monitoring.

[0025] Furthermore, during the switching of microwave excitation with different pulse widths, the ultrasonic transducer, amplifier, data acquisition card, antenna, and the tested biological tissue all remain stationary.

[0026] The core of this invention lies in discovering and utilizing the dependence of the "microwave thermoacoustic signal saturation effect" on object size. There is a non-monotonic dependence between the amplitude of the microwave thermoacoustic signal and the excitation pulse width: when the pulse width is much smaller than the thermal diffusion characteristic time of the object, the amplitude of the microwave thermoacoustic signal is proportional to the pulse width; when the pulse width approaches or exceeds the thermal diffusion characteristic time of the object, the amplitude of the microwave thermoacoustic signal no longer increases, and a "saturation effect" occurs. Objects of different sizes have different saturation threshold pulse widths. The smaller the object, the shorter its saturation threshold pulse width, and the earlier it enters the saturation region.

[0027] Utilizing the aforementioned phenomena, pulse width serves as a new and adjustable key to resolution. This invention innovatively combines "pulse width modulation" and "microwave thermoacoustic saturation effect." By systematically and continuously modulating the pulse width of the excitation source and acquiring a series of microwave thermoacoustic images with different pulse widths, and analyzing the amplitude variation curves of the microwave thermoacoustic signal under different pulse widths, the saturation characteristics of each imaging point can be extracted, thereby retrieving the size information of the scattering object corresponding to that point. This achieves the realization of using the correspondence between the saturation threshold pulse width and the object size as a physical mechanism for achieving super-resolution.

[0028] The microwave thermoacoustic imaging technology employed in this invention combines the high contrast characteristics of purely optical imaging methods with the high resolution characteristics of purely ultrasonic imaging methods, thereby overcoming the limitations of existing single-modal imaging techniques. Its significant advantages are specifically reflected in the following two aspects: high contrast and high spatial resolution.

[0029] High contrast advantage: The image contrast obtained by the imaging technology directly stems from the differences in the absorption coefficients of different components within biological tissues to pulsed electromagnetic energy. When excited using optical bands (i.e., photoacoustic imaging), this technology can specifically respond to and distinguish biomolecules with characteristic optical absorption spectra, such as hemoglobin (including its oxygenated and deoxygenated states), lipids, and melanin. Therefore, this invention can achieve high-contrast imaging of physiological functional states and specific molecular distributions, such as quantifying tissue blood oxygen saturation and monitoring tumor-related angiogenesis. Compared to traditional ultrasound imaging, which mainly relies on differences in acoustic impedance, this invention possesses an essential and significant contrast advantage in revealing functional and molecular-level information.

[0030] Advantages of high spatial resolution: The imaging technology reconstructs images by detecting ultrasound waves, which have extremely weak scattering effects in biological media. Its spatial resolution depends primarily on the center frequency and bandwidth performance of the ultrasound sensor used, rather than being limited by the diffraction limit determined by optical scattering. Therefore, within an effective imaging depth of several millimeters to several centimeters, this invention can achieve high spatial resolution on the order of hundreds of micrometers. This resolution characteristic, at the same penetration depth, is significantly superior to diffusion-based imaging techniques, solving the long-standing technical challenge of balancing high resolution and deep penetration in purely optical imaging methods.

[0031] The beneficial effects of this invention are:

[0032] 1. Breaking the diffraction limit: For the first time, the saturation effect of microwave thermoacoustic signals is applied to imaging, providing a brand-new super-resolution imaging mechanism, and the spatial resolution is no longer limited by the ultrasonic diffraction limit.

[0033] 2. Rich in functional information: It can not only provide traditional microwave absorption contrast images, but also provide additional size-related structural information, which helps to distinguish different pathological tissues (such as new microvessels and mature blood vessels).

[0034] 3. Simple to implement and low cost: It does not require modification of complex ultrasonic detection arrays or optical systems. It only requires adding pulse width modulation and scanning functions to the pulse source of the existing microwave thermoacoustic imaging system, which is easy to implement and promote. Attached Figure Description

[0035] Figure 1 This is a schematic block diagram of the device of the present invention.

[0036] Figure 2 A schematic diagram of the nonlinear saturation curve between the amplitude of a microwave thermoacoustic signal and the pulse width for an object with a diameter of 3 mm. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] This embodiment provides a super-resolution microwave thermoacoustic imaging method and apparatus based on nonlinear saturated response absorption, which utilizes the saturation effect of microwave thermoacoustic signals by modulating microwave pulse width to achieve super-resolution imaging. The method includes an image acquisition process and an image analysis process. First, microwave thermoacoustic signals of samples under different pulse width excitations are acquired. A single-pulse-width microwave thermoacoustic image is reconstructed using an imaging algorithm. Multiple microwave thermoacoustic images with different pulse widths are obtained using a parallel processing algorithm. Then, the microwave thermoacoustic signal intensity variation curve of each pixel in the microwave thermoacoustic image under different pulse widths is analyzed. Based on the saturation characteristic parameters of different pixels, the image is clustered or color-coded. The pulse width corresponding to the inflection point where the slope of the microwave thermoacoustic signal intensity variation curve changes from linear to flat is the saturated pulse width of the sample at that pixel. A super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption specifically includes the following steps:

[0039] Step 1: Apply an excitation pulse sequence; set an initial short pulse width, and apply a series of (microwave) or laser pulses with the same energy but continuously increasing pulse widths to the object being detected. The object being detected can include, but is not limited to, fat, blood vessels, muscle, and tumor tissue. The laser pulse sequence should include at least 10 different pulse widths (e.g., starting from 50 ns and increasing in 100 ns increments), with the same microwave frequency, pulse power, pulse repetition frequency, and other parameters.

[0040] Step 2: Acquire microwave thermoacoustic signals; use an ultrasonic detector to receive the microwave thermoacoustic signals generated by each pulse excitation, and reconstruct the microwave thermoacoustic image corresponding to each pulse width using a microwave thermoacoustic image reconstruction algorithm. The microwave thermoacoustic image reconstruction algorithm can be a back projection algorithm, a delay and superposition algorithm, a filtered back projection algorithm, a time reversal algorithm, or compressed sensing, etc.

[0041] Step 3: Construct a signal growth curve; For each pixel in the image, extract its signal amplitude under different pulse widths to form a signal amplitude-pulse width relationship curve.

[0042] Step 4: Feature extraction and pixel classification; Analyze the signal amplitude-pulse width relationship curve and extract the saturation feature parameters of each pixel, including the saturation threshold pulse width, the slope of the linear region, and the amplitude of the saturation region.

[0043] Step 5: Generate a super-resolution image; using saturation feature parameters, generate a new image where pixel values ​​represent the size information or "small size probability" of a point, thereby achieving specific enhanced display of sub-resolution structures in a large background. This can be achieved through thresholding, size mapping, or curve decomposition methods.

[0044] Thresholding: Select a microwave thermoacoustic image acquired with a relatively short pulse width (e.g., 50 ns). In this image, the microwave thermoacoustic signal of target absorbers smaller than a certain threshold is saturated, while the signal of larger objects continues to increase linearly. Highlight these small-sized structures using image processing algorithms (e.g., enhancing the signal values ​​of saturated pixels or assigning specific pseudocolors).

[0045] Size mapping: Mapping the value of each pixel through a predefined linear relationship, such as... Figure 2 The linear region shown is converted into its corresponding feature size, thus generating a size distribution map. This map itself is a super-resolution image because it reveals structural information at the subwavelength scale.

[0046] Curve decomposition: The entire image sequence is regarded as a data cube. Taking advantage of the fact that objects of different sizes have different growth curves, blind source separation or deconvolution algorithms are used to separate the components of different sizes that contribute to the microwave thermoacoustic signal, and finally synthesize a super-resolution image with a resolution far exceeding that of a single image.

[0047] During the image analysis process in steps 2-5, such as Figure 2 As shown, the thermoacoustic signal generated by microwave absorption from a target with a radius of 3 mm exhibits a phenomenon of first increasing linearly and then saturating with the pulse width. Because biological tissues of different sizes have nonlinear saturation response absorption characteristics to microwave excitation with different pulse widths, when the incident microwave pulse width is less than the saturation absorption pulse width for a certain size, the intensity of the microwave thermoacoustic signal increases linearly with the pulse width (unsaturated); when the microwave pulse width reaches or exceeds the saturation response absorption pulse width for that size of biological tissue, the intensity of the microwave thermoacoustic signal no longer increases (absorption saturation), and may even decrease slightly due to the microwave bleaching effect. Analyzing the microwave thermoacoustic signal intensity variation curves of each pixel in the microwave thermoacoustic image under different pulse widths, the pulse width corresponding to the "inflection point" where the curve slope changes from linear to flat is the saturation pulse width of the biological tissue at that pixel. Based on the differences in the saturation pulse widths of different pixels, the image is clustered or color-coded to distinguish biological tissues of different sizes. Because this method utilizes the nonlinear saturation absorption characteristics between the microwave thermoacoustic signals of biological tissues of different sizes and the width of the excitation microwave pulse, it can achieve selective imaging of biological tissues of different sizes with high contrast. Based on differential or saturation threshold imaging, it can further obtain super-resolution microwave thermoacoustic imaging.

[0048] A super-resolution microwave thermoacoustic imaging device based on nonlinear saturated response absorption, such as Figure 1 As shown, it includes a microwave excitation module, an ultrasonic coupling module, a microwave thermoacoustic signal data acquisition module, and a real-time image reconstruction and analysis module;

[0049] The microwave excitation module includes a pulse width modulation (PWM) microwave source and a microwave antenna. The PWM microwave source generates microwaves with different pulse widths, which are transmitted to the antenna via a coaxial cable to radiate the microwaves onto the sample (biological tissue) being tested. The microwaves with different pulse widths generated by the PWM microwave source are generated by the same variable pulse width microwave source or by multiple pulse width microwave sources. The microwaves with different pulse widths need to maintain a consistent center frequency and peak power. Alternatively, the PWM microwave source has real-time feedback and programmable control functions for pulse width monitoring.

[0050] The ultrasonic coupling module is an ultrasonic transducer. The sample under test absorbs microwave energy to generate ultrasonic waves, i.e., microwave thermoacoustic signals. Microwave thermoacoustic signals under microwave excitation with different pulse widths are detected by the ultrasonic transducer and transmitted to the microwave thermoacoustic signal data acquisition module.

[0051] The microwave thermoacoustic signal data acquisition module includes a data acquisition card and a multi-channel microwave thermoacoustic signal amplifier; the microwave thermoacoustic signal is amplified by the amplifier, and the amplified signal is acquired by the data acquisition card to obtain microwave thermoacoustic data under different pulse width excitation, which is then transmitted to the real-time image reconstruction and analysis module.

[0052] The real-time image reconstruction and analysis module controls the microwave excitation module, the ultrasonic coupling module, and the microwave thermoacoustic signal data acquisition module. Based on the relationship between the temporal information and spatial location in the microwave thermoacoustic data, it uses imaging algorithms to reconstruct single-pulse-width microwave thermoacoustic images. Then, it uses analysis methods to obtain multi-pulse-width microwave thermoacoustic images from the single-pulse-width microwave thermoacoustic data or images. The pulse width in multi-pulse-width microwave thermoacoustic imaging refers to the duration of microwave emission. Single-pulse-width microwave thermoacoustic images are used to analyze biological tissue imaging under single-pulse-width microwave energy irradiation. The microwave thermoacoustic signal intensity variation curves for each pixel in the microwave thermoacoustic images at different pulse widths, with the pulse width corresponding to the "inflection point" where the curve slope changes from linear to flat, represent the saturation pulse width of the biological tissue at that pixel. Based on the differences in the saturation pulse widths of different pixels, the images are clustered or color-coded to distinguish biological tissues of different sizes.

[0053] During the switching of multi-pulse width microwave excitation, the ultrasonic transducer, amplifier, data acquisition card, antenna, and the tested biological tissue all remain stationary.

[0054] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption, characterized in that, include: First, microwave thermoacoustic signals of samples under different pulse width excitations are acquired. Microwave thermoacoustic images with a single pulse width are reconstructed using an imaging algorithm. Microwave thermoacoustic images with all pulse widths are obtained through parallel processing. Then, the microwave thermoacoustic signal intensity variation curve of each pixel in the microwave thermoacoustic image under different pulse widths is analyzed. Based on the saturation feature parameters of different pixels, the images are clustered or color-coded.

2. The super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption according to claim 1, characterized in that, The saturation feature parameters include the saturation threshold pulse width, the slope of the linear region, and the amplitude of the saturation region. The pulse width corresponding to the inflection point where the slope of the microwave thermoacoustic signal intensity change curve changes from linear to gentle is the saturation pulse width of the sample at that pixel.

3. The super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption according to claim 2, characterized in that, The method specifically includes the following sub-steps: Step 1: Set the initial short pulse width, and apply microwave or laser pulses with the same energy but continuously increasing pulse width to the object being detected; the microwave frequency, pulse power, and pulse repetition frequency are the same; Step 2: Use an ultrasonic detector to receive the microwave thermoacoustic signal generated by each pulse excitation, and use a microwave thermoacoustic image reconstruction algorithm to reconstruct the microwave thermoacoustic image corresponding to each pulse width; Step 3: For each pixel in the microwave thermoacoustic image, extract its signal amplitude under different pulse widths to obtain a signal amplitude-pulse width relationship curve; Step 4: Analyze the signal amplitude-pulse width relationship curve and extract the saturation feature parameters for each pixel; Step 5: Using saturation feature parameters, generate a new super-resolution image, where pixel values ​​represent the size information or small size probability of that point.

4. The super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption according to claim 3, characterized in that, The sequence of laser pulses includes at least 10 different pulse widths.

5. The super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption according to claim 4, characterized in that, The microwave thermoacoustic image reconstruction algorithm is a back projection algorithm, a delay and overlay algorithm, a filtered back projection algorithm, a time reversal algorithm, or compressed sensing.

6. The super-resolution microwave thermoacoustic imaging method based on nonlinear saturated response absorption according to claim 5, characterized in that, The super-resolution image is generated through thresholding, size mapping, or curve decomposition methods. The specific generation process is as follows: Threshold filtering: Select a microwave thermoacoustic image acquired under a short pulse width in a pulse sequence. In this image, the microwave thermoacoustic signal of the target absorber with a size smaller than the threshold has been saturated, while the signal of larger objects is still increasing linearly. The small-sized structures smaller than the threshold are highlighted by the image processing algorithm. Size mapping: The value of each pixel is converted into the corresponding feature size through a pre-defined linear relationship, thereby generating a size distribution map; Curve decomposition: The entire microwave thermoacoustic image sequence is regarded as a data cube. Taking advantage of the fact that objects of different sizes have different growth curves, blind source separation or deconvolution algorithms are used to separate the different size components that contribute to the microwave thermoacoustic signal, and finally synthesize a super-resolution image with a resolution far exceeding that of a single image.

7. A super-resolution microwave thermoacoustic imaging device based on nonlinear saturated response absorption, characterized in that, It includes a microwave excitation module, an ultrasonic coupling module, a microwave thermoacoustic signal data acquisition module, and a real-time image reconstruction and analysis module; The microwave excitation module includes a pulse width modulation microwave source and a microwave antenna. The pulse width modulation microwave source generates microwaves with different pulse widths, which are transmitted to the antenna via a coaxial cable to radiate the microwaves to the sample under test. The ultrasonic coupling module is an ultrasonic transducer. The sample under test absorbs microwave energy to generate ultrasonic waves, i.e., microwave thermoacoustic signals. Microwave thermoacoustic signals under microwave excitation with different pulse widths are detected by the ultrasonic transducer and transmitted to the microwave thermoacoustic signal data acquisition module. The microwave thermoacoustic signal data acquisition module includes a data acquisition card and a multi-channel microwave thermoacoustic signal amplifier; the microwave thermoacoustic signal is amplified by the amplifier, and the amplified signal is acquired by the data acquisition card to obtain microwave thermoacoustic data under different pulse width excitation, which is then transmitted to the real-time image reconstruction and analysis module. The real-time image reconstruction and analysis module controls the microwave excitation module, the ultrasonic coupling module, and the microwave thermoacoustic signal data acquisition module. Then, based on the relationship between the temporal information and spatial location in the microwave thermoacoustic data, it uses a microwave thermoacoustic image reconstruction algorithm to reconstruct a single-pulse-width microwave thermoacoustic image, obtaining a multi-pulse-width microwave thermoacoustic image. Then, it analyzes the microwave thermoacoustic signal intensity variation curve of each pixel in the microwave thermoacoustic image under different pulse widths. Based on the saturation feature parameters of different pixels, it performs clustering or color coding on the image to distinguish biological tissues of different sizes.

8. The super-resolution microwave thermoacoustic imaging device based on nonlinear saturated response absorption according to claim 7, characterized in that, The microwaves with different pulse widths generated by the pulse width modulation microwave source can be generated by the same variable pulse width microwave source or by multiple pulse width microwave sources; microwaves with different pulse widths need to maintain the same center frequency and peak power; the pulse width modulation microwave source has real-time feedback and programmable control functions for pulse width monitoring.

9. A super-resolution microwave thermoacoustic imaging device based on nonlinear saturated response absorption according to claim 8, characterized in that, When switching between microwave excitation with different pulse widths, the ultrasonic transducer, amplifier, data acquisition card, antenna, and the tested biological tissue all remain stationary.

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