Method, system and device for realizing multi-mode photoacoustic angiography based on optical wavefront shaping and acoustic focusing, processor and medium

Abstract

The invention relates to a method for realizing multi-mode photoacoustic angiography based on optical wavefront shaping and acoustic focusing, which comprises the following steps of: carrying out region positioning to output an optimal matching region coordinate, and exciting a photoacoustic effect of the optimal matching region coordinate; the laser is focused through the wavefront shaping module; an ultrasonic transducer is excited by a pulse generator to generate ultrasonic pulses; enabling the photoacoustic pressure wave signal and the ultrasonic signal to pass through an amplification filter and an analog-to-digital converter in sequence; the excited opto-acoustic pressure waves and ultrasonic signals are sequentially enhanced through an acoustic focusing adjustment module; and performing image reconstruction on the digitalized enhanced photoacoustic signal and the enhanced ultrasonic signal. By adopting the method, system and device for realizing multi-mode photoacoustic angiography based on optical wavefront shaping and acoustic focusing, the processor and the computer readable storage medium thereof, the energy utilization efficiency of the laser is improved, the threshold of the laser is reduced, the equipment cost is reduced, and the photoacoustic signal intensity and distribution uniformity of deep tissues are improved.

Description

Technical Field

[0001] The present invention relates to the field of angiography technology, in particular to the field of angiography, and specifically refers to a method, system, device, processor and computer-readable storage medium thereof for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing. Background Art

[0002] With the increasing demand for clinical imaging of vascular microstructure and function, photoacoustic imaging technology has gradually been widely used in fields such as angiography, tumor detection, and tissue function analysis due to its advantages of high optical contrast, high directivity, and ultrasonic resolution. Photoacoustic angiography technology uses laser to excite the photoacoustic signal from the target chromophore in biological tissue, combined with a conventional ultrasound imaging receiving system, to achieve high-resolution imaging of vascular structures at low cost. It is especially suitable for identifying tiny blood vessels and low-contrast tissue structures. However, traditional photoacoustic imaging systems still face many challenges in practical applications:

[0003] On the one hand, the optical excitation path has diffraction limits and tissue scattering problems. In the visible light band, traditional optical microscopes rely on ballistic light imaging. Since the intensity of ballistic light decays exponentially with increasing imaging depth, its imaging depth is about 100 microns. This causes uneven propagation of photons in the tissue, limiting the excitation depth. In particular, it is difficult to maintain a sufficient signal-to-noise ratio when imaging deep microvascular structures, which manifests as a low imaging resolution. The optical focusing method achieved by adjusting the spatial distribution of optical lenses in the past did not take into account the impact of the internal biological tissue on photon propagation. Moreover, the lens focusing structure is bulky, precise, difficult to maintain, and expensive. In large-scale mass production, there may be scrap caused by assembly errors, resulting in a waste of resources.

[0004] On the other hand, insufficient transducer focusing capability on the acoustic receiving side can also lead to reduced spatial resolution, especially in areas with strong tissue heterogeneity or densely distributed target blood vessels. Previous geometrically designed reflectance probes had a fixed focus, which only allowed for clear imaging at a fixed depth. This made them difficult to adapt to multi-layer imaging requirements, affecting image clarity and tomographic quality. Furthermore, transducer aperture size and bandwidth are also major factors limiting imaging resolution and depth.

[0005] Finally, traditional photoacoustic imaging is limited by the cost of equipment manufacturing, and it is difficult to use laser light sources with adjustable wavelength capabilities, such as optical parametric oscillators (OPOs). A single optical wavelength can only image a specific few chromophores and measure their content. However, in biological tissue imaging, in addition to the content of the target chromophore, its distribution within the tissue cannot be ignored. Taking angiography as an example, it not only focuses on the blood characteristics in the blood vessels, such as blood oxygen saturation and flow rate information, but also on the relative position of the blood vessels in the deep skin. Moreover, even if a multi-wavelength light source is used, the unmixing of the multispectral algorithm affects the real-time performance of the imaging system and increases the computational cost of the imaging system.

[0006] In summary, there is an urgent need to improve the uniformity of photoacoustic signals and dynamically control and enhance spatial focusing capabilities, thereby enhancing the imaging depth, resolution, and multi-parameter characterization capabilities of angiography. Furthermore, combining the respective advantages of photoacoustic imaging and ultrasound imaging, and fusing the two modalities, can better meet the practical needs of precision medicine and microvascular function research. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method, system, device, processor and computer-readable storage medium thereof for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, which meets the requirements of clear imaging, low cost and wide application range.

[0008] To achieve the above objectives, the present invention provides a method, system, device, processor, and computer-readable storage medium for implementing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing as follows:

[0009] The method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing is mainly characterized in that the method comprises the following steps:

[0010] (1) obtaining a priori image, capturing a target imaging area, and combining the priori image to perform regional positioning and output optimal matching area coordinates, and stimulating the photoacoustic effect of the optimal matching area coordinates by laser;

[0011] (2) Focusing the laser through the wavefront shaping module;

[0012] (3) exciting the ultrasonic transducer to generate ultrasonic pulses through a pulse generator;

[0013] (4) passing the photoacoustic pressure wave signal and the ultrasonic signal through an amplifying filter and an analog-to-digital converter in sequence;

[0014] (5) The excited photoacoustic pressure wave and the ultrasonic signal are successively enhanced through the acoustic focusing adjustment module;

[0015] (6) The digitized enhanced photoacoustic signal and the enhanced ultrasound signal are reconstructed and multimodal fusion is used to output angiography images.

[0016] Preferably, performing regional positioning in step (1) specifically includes the following steps:

[0017] (1.1) extracting features of the prior image and the target imaging area by feature extraction to construct a prior image feature map and a current frame feature map of the target imaging area;

[0018] (1.2) Performing region matching on the prior image feature map and the current frame feature map of the target imaging area through similarity measurement to output the coordinates of the optimal matching area.

[0019] Preferably, the step (2) specifically includes the following steps:

[0020] (2.1) Constructing a transfer matrix using the method of mapping the input structured light pattern and its corresponding measurement results;

[0021] (2.2) After obtaining the transmission matrix, we can use the phase conjugation method to modulate the incident laser with a digital micromirror and focus it at any position on the output plane.

[0022] Preferably, the step (4) specifically includes the following steps:

[0023] (4.1) performing a rapid spectrum analysis on the photoacoustic signal excited by the laser pulse to obtain a preliminary frequency range signal;

[0024] (4.2) sparsely sampling the preliminary frequency range signal using an adaptive compressed sensing modulator to obtain a perceptually compressed signal;

[0025] (4.3) performing maximum norm approximation estimation on the perceived compressed signal to obtain a signal amplitude;

[0026] (4.4) Adjust the amplifier gain based on the predicted signal amplitude to amplify the signal while ensuring the dynamic range;

[0027] (4.5) The DC component extracted by the low-pass filter is eliminated by a bias current source to obtain the preliminary dynamic range enhanced ultrasonic signal and the preliminary dynamic range enhanced photoacoustic signal;

[0028] (4.6) automatically converting the signal into a digital signal according to the signal amplitude through a high-resolution and high-speed analog-to-digital conversion unit;

[0029] Preferably, the step (5) specifically includes the following steps:

[0030] (5.1) Delaying the ultrasonic signal and the photoacoustic signal by a delay module to obtain aligned multi-channel ultrasonic signals and photoacoustic signals;

[0031] (5.2) Envelope extraction is performed on the multi-channel ultrasonic signal and the photoacoustic signal, and the ultrasonic signal and the photoacoustic signal of each channel are superimposed respectively.

[0032] Preferably, the fast spectrum analysis in (4.1) specifically includes FFT pre-sampling and bandwidth detection.

[0033] Preferably, the envelope extraction in (5.2) includes hardware IQ demodulation.

[0034] Preferably, the step (5.1) performs delay control, specifically comprising the following steps:

[0035] (5.1.1) Obtaining a system clock, dividing, multiplying, adjusting the phase, and adjusting the duty cycle of the system clock through a phase-locked loop to output a stable clock;

[0036] (5.1.2) generating a logic control signal through a waveform generator based on the stable clock and the ultrasonic signal;

[0037] (5.1.3) The logic control signal is delayed by a shift register to obtain a delayed control signal.

[0038] Preferably, the step (6) specifically includes the following steps:

[0039] (6.1) Reconstruct the attenuation of the ultrasound pulse inside the imaging target through maximum mapping to obtain structural information;

[0040] (6.2) Using the deconvolution point spread function approach, reconstruct the absorption of the laser pulse by the imaging target to obtain specific information;

[0041] (6.3) Read the pre-stored acquisition timestamp and align the acquisition time;

[0042] (6.4) The ultrasound image is superimposed on the photoacoustic imaging results to complete the fusion of the ultrasound mode and the photoacoustic mode.

[0043] The system for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing has the following main features: the system includes a regional matching module, an analog-to-digital conversion module, a signal focusing module, a hardware signal preprocessing module, a modality fusion module, and a signal excitation module;

[0044] The signal excitation module includes a nanosecond laser light source and an ultrasonic pulse generator. The laser light source is used to excite the laser light source to generate nanosecond pulses, irradiating the target imaging area to produce a photoacoustic effect; the ultrasonic pulse generator generates a voltage sufficient to excite the ultrasonic transducer to emit ultrasonic waves, and switches to modulate it into a pulse form.

[0045] The region matching module is used to obtain a priori images, capture the target imaging area, and perform region positioning based on the priori images to output the coordinates of the optimal matching region, and obtain the photoacoustic signal of the optimal matching region coordinates through a laser;

[0046] The analog-to-digital conversion module is connected to the area matching module and is used to perform analog-to-digital conversion on the photoacoustic and ultrasonic signals to obtain digitized ultrasonic signals and photoacoustic signals;

[0047] The signal focusing module is connected to the analog-to-digital conversion module and is used to obtain an enhanced ultrasonic signal from the ultrasonic and photoacoustic signals through the focusing adjustment module, and to focus the pulsed laser of the light source through the wavefront shaping module;

[0048] The hardware signal preprocessing module is connected to the signal focusing module and is used to perform preliminary amplification and filtering on the original signal from the transducer, eliminate DC to enhance the signal dynamic range, and maximize the performance of the analog-to-digital conversion module;

[0049] The modality fusion module is connected to the hardware signal preprocessing module and is used to perform multimodal fusion of the enhanced ultrasound signal and the enhanced photoacoustic signal to output an angiography image.

[0050] The device for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing has the following main features:

[0051] a processor configured to execute computer-executable instructions;

[0052] A memory stores one or more computer-executable instructions, which, when executed by the processor, implement the various steps of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0053] The main feature of the processor for implementing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing is that the processor is configured to execute computer-executable instructions. When the computer-executable instructions are executed by the processor, the various steps of the above-mentioned method for implementing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing are implemented.

[0054] The main feature of this computer-readable storage medium is that it stores a computer program, which can be executed by a processor to implement the various steps of the above-mentioned method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0055] The present invention employs a method, system, device, processor, and computer-readable storage medium for multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing. By optimizing the laser irradiation area through a region matching and positioning mechanism based on a priori images and optical wavefront shaping, the laser energy is more concentrated on the targeted microvascular region. This effectively overcomes the photoacoustic excitation depth limitation caused by scattering and absorption in biological tissue, improves laser energy utilization efficiency, lowers the laser threshold, reduces equipment costs, and significantly enhances the photoacoustic signal intensity and distribution uniformity in deep tissue. Ultimately, this achieves efficient multimodal photoacoustic and ultrasound fusion angiography based on optical wavefront shaping and acoustic focusing. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a schematic diagram of a signal receiving link block diagram of a method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present invention, the back end of which is a microcontroller.

[0057] Figure 2 Schematic diagram of the receiving and focusing principle of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present invention.

[0058] Figure 3 Schematic diagram of the intermediate process of time delay alignment of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present invention.

[0059] Figure 4 Schematic diagram of the DC bias elimination dynamic range enhancement of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present invention.

[0060] Figure 5 This is a simulation diagram of the temperature change of skin tissue under light source irradiation in the method of realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present invention. DETAILED DESCRIPTION

[0061] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0062] The method of the present invention for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing comprises the following steps:

[0063] (1) obtaining a priori image, capturing a target imaging area, and combining the priori image to perform regional positioning and output optimal matching area coordinates, and stimulating the photoacoustic effect of the optimal matching area coordinates by laser;

[0064] (2) Focusing the laser through the wavefront shaping module;

[0065] (3) exciting the ultrasonic transducer to generate ultrasonic pulses through a pulse generator;

[0066] (4) passing the photoacoustic pressure wave signal and the ultrasonic signal through an amplifying filter and an analog-to-digital converter in sequence;

[0067] (5) The excited photoacoustic pressure wave and the ultrasonic signal are successively enhanced through the acoustic focusing adjustment module;

[0068] (6) The digitized enhanced photoacoustic signal and the enhanced ultrasound signal are reconstructed and multimodal fusion is used to output angiography images.

[0069] As a preferred embodiment of the present invention, performing regional positioning in step (1) specifically includes the following steps:

[0070] (1.1) extracting features of the prior image and the target imaging area by feature extraction to construct a prior image feature map and a current frame feature map of the target imaging area;

[0071] (1.2) Performing region matching on the prior image feature map and the current frame feature map of the target imaging area through similarity measurement to output the coordinates of the optimal matching area.

[0072] As a preferred embodiment of the present invention, the step (2) specifically includes the following steps:

[0073] (2.1) Constructing a transfer matrix using the method of mapping the input structured light pattern and its corresponding measurement results;

[0074] (2.2) After obtaining the transmission matrix, we can use the phase conjugation method to modulate the incident laser with a digital micromirror and focus it at any position on the output plane.

[0075] As a preferred embodiment of the present invention, the step (4) specifically includes the following steps:

[0076] (4.1) performing a rapid spectrum analysis on the photoacoustic signal excited by the laser pulse to obtain a preliminary frequency range signal;

[0077] (4.2) sparsely sampling the preliminary frequency range signal using an adaptive compressed sensing modulator to obtain a perceptually compressed signal;

[0078] (4.3) performing maximum norm approximation estimation on the perceived compressed signal to obtain a signal amplitude;

[0079] (4.4) Adjust the amplifier gain based on the predicted signal amplitude to amplify the signal while ensuring the dynamic range;

[0080] (4.5) The DC component extracted by the low-pass filter is eliminated by a bias current source to obtain the preliminary dynamic range enhanced ultrasonic signal and the preliminary dynamic range enhanced photoacoustic signal;

[0081] (4.6) automatically converting the signal into a digital signal according to the signal amplitude through a high-resolution and high-speed analog-to-digital conversion unit;

[0082] As a preferred embodiment of the present invention, the step (5) specifically includes the following steps:

[0083] (5.1) Delaying the ultrasonic signal and the photoacoustic signal by a delay module to obtain aligned multi-channel ultrasonic signals and photoacoustic signals;

[0084] (5.2) Envelope extraction is performed on the multi-channel ultrasonic signal and the photoacoustic signal, and the ultrasonic signal and the photoacoustic signal of each channel are superimposed respectively.

[0085] As a preferred embodiment of the present invention, the fast spectrum analysis in (4.1) specifically includes FFT pre-sampling and bandwidth detection.

[0086] As a preferred embodiment of the present invention, the envelope extraction in (5.2) includes hardware IQ demodulation.

[0087] As a preferred embodiment of the present invention, the step (5.1) performs delay control, specifically comprising the following steps:

[0088] (5.1.1) Obtaining a system clock, dividing, multiplying, adjusting the phase, and adjusting the duty cycle of the system clock through a phase-locked loop to output a stable clock;

[0089] (5.1.2) generating a logic control signal through a waveform generator based on the stable clock and the ultrasonic signal;

[0090] (5.1.3) The logic control signal is delayed by a shift register to obtain a delayed control signal.

[0091] As a preferred embodiment of the present invention, the step (6) specifically includes the following steps:

[0092] (6.1) Reconstruct the attenuation of the ultrasound pulse inside the imaging target through maximum mapping to obtain structural information;

[0093] (6.2) Using the deconvolution point spread function approach, reconstruct the absorption of the laser pulse by the imaging target to obtain specific information;

[0094] (6.3) Read the pre-stored acquisition timestamp and align the acquisition time;

[0095] (6.4) The ultrasound image is superimposed on the photoacoustic imaging results to complete the fusion of the ultrasound mode and the photoacoustic mode.

[0096] The system of the present invention for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing comprises a regional matching module, an analog-to-digital conversion module, a signal focusing module, a hardware signal preprocessing module, a modality fusion module, and a signal excitation module;

[0097] The signal excitation module includes a nanosecond laser light source and an ultrasonic pulse generator. The laser light source is used to excite the laser light source to generate nanosecond pulses, irradiating the target imaging area to produce a photoacoustic effect; the ultrasonic pulse generator generates a voltage sufficient to excite the ultrasonic transducer to emit ultrasonic waves, and switches to modulate it into a pulse form.

[0098] The region matching module is used to obtain a priori images, capture the target imaging area, and perform region positioning based on the priori images to output the coordinates of the optimal matching region, and obtain the photoacoustic signal of the optimal matching region coordinates through a laser;

[0099] The analog-to-digital conversion module is connected to the area matching module and is used to perform analog-to-digital conversion on the photoacoustic and ultrasonic signals to obtain digitized ultrasonic signals and photoacoustic signals;

[0100] The signal focusing module is connected to the analog-to-digital conversion module and is used to obtain an enhanced ultrasonic signal from the ultrasonic and photoacoustic signals through the focusing adjustment module, and to focus the pulsed laser of the light source through the wavefront shaping module;

[0101] The hardware signal preprocessing module is connected to the signal focusing module and is used to perform preliminary amplification and filtering on the original signal from the transducer, eliminate DC to enhance the signal dynamic range, and maximize the performance of the analog-to-digital conversion module;

[0102] The modality fusion module is connected to the hardware signal preprocessing module and is used to perform multimodal fusion of the enhanced ultrasound signal and the enhanced photoacoustic signal to output an angiography image.

[0103] The device for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present invention comprises:

[0104] a processor configured to execute computer-executable instructions;

[0105] A memory stores one or more computer-executable instructions, which, when executed by the processor, implement the various steps of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0106] The processor of the present invention implements multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, wherein the processor is configured to execute computer-executable instructions. When the computer-executable instructions are executed by the processor, the various steps of the above-mentioned method for implementing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing are implemented.

[0107] The computer-readable storage medium of the present invention stores a computer program thereon, and the computer program can be executed by a processor to implement the various steps of the above-mentioned method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0108] Specific embodiments of the present invention provide an angiography method with adjustable imaging depth, high specificity, low cost, easy interpretability, and clear imaging, belonging to the field of angiography technology. This method primarily builds upon the hardware foundation of traditional ultrasound imaging angiography and addresses the issues of unclear results, poor specificity, and ambiguous spatial distribution found in traditional noninvasive angiography. This method provides a feasible improvement to traditional ultrasound imaging hardware.

[0109] In a specific embodiment of the present invention, the following specific steps are included:

[0110] S1: Acquire a priori image, capture the target imaging area, and perform regional positioning based on the priori image to output the coordinates of the optimal matching area, and stimulate the photoacoustic effect of the optimal matching area coordinates through a laser;

[0111] S2: The laser is focused by the wavefront shaping module to enhance the stimulated photoacoustic signal;

[0112] S3: The ultrasonic transducer is excited by the pulse generator to generate an ultrasonic pulse;

[0113] S4: passing the photoacoustic pressure wave signal and the ultrasonic signal through an amplifying filter and an analog-to-digital converter in sequence;

[0114] S5: The excited photoacoustic pressure wave and the ultrasonic signal are successively enhanced through the acoustic focusing adjustment module;

[0115] S6: Reconstruct the digitized enhanced photoacoustic signal and the enhanced ultrasound signal, and output the angiography image through multimodal fusion.

[0116] Specifically, the regional positioning process in step S1 includes:

[0117] S101: constructing a priori image feature map and a current frame feature map of the target imaging area by feature extraction of the priori image and the target imaging area;

[0118] S102: Performing region matching on the prior image feature map and the current frame feature map of the target imaging region by similarity measurement to output the optimal matching region coordinates.

[0119] Specifically, the structure of the probe in step S1 is as follows: multiple clusters of optical fiber cores are additionally installed on both sides of the original ultrasonic transducer array probe to transmit the laser light to the measured position; the output form of the laser is a collimated beam, which is coupled to a multi-core multimode optical fiber by a collimator-to-fiber coupler after completing wavefront shaping in step S2.

[0120] Specifically, the imaging system designed by the present invention has a light source irradiation energy of 17.69 / cm 2 , wavelength 532nm, far lower than the 20mJ / cm specified in the national standard GB 7247.1 2 By inputting the selected light source parameters into the computer to perform simulation, the following Figure 5 The skin heating result is shown in Figure 2. It can be seen that the selected pulse light source is suitable for stimulating the photoacoustic effect and is safe for the human body.

[0121] Specifically, the wavefront shaping process in step S2 is:

[0122] S201: Constructing a transfer matrix using a method of mapping an input structured light pattern and its corresponding measurement results.

[0123] S202: After obtaining the transmission matrix, the incident laser can be modulated by a digital micromirror (DMD) using the phase conjugation method to focus at any position on the output plane. The complex light field of each output point can be represented as the superposition of multiple input light modes, i.e., E in =T H E out . Where T is the transmission matrix.

[0124] Constructing a row vector of the transfer matrix requires traversing all input modes of the structured light modulator. Under this physical model, achieving the output light field focusing at a specific position is essentially to achieve the target position E m To achieve this goal, we need to obtain the phase pattern of the structured light. This allows for rotation and alignment of all phases.

[0125] Receiving process as Figure 1 As shown, specifically, the signal conversion process of the analog-to-digital conversion in step S4 is:

[0126] S401: Performing a rapid spectrum analysis on the photoacoustic signal excited by the laser pulse to obtain a preliminary frequency range signal;

[0127] S402: Sparsely sampling the preliminary frequency range signal using an adaptive compressed sensing modulator to obtain a perceptual compressed signal;

[0128] S403: Perform maximum norm approximation estimation on the perceptually compressed signal to obtain a signal amplitude;

[0129] S404: adjusting the gain of the amplifier according to the pre-estimated signal amplitude, and amplifying the signal while ensuring the dynamic range;

[0130] S405: If Figure 4 As shown, the DC component extracted by the low-pass filter is eliminated by the bias current source to obtain the preliminary dynamic range enhanced ultrasonic signal and the preliminary dynamic range enhanced photoacoustic signal;

[0131] S406: Automatically convert the signal into a digital signal according to the signal amplitude through a high-resolution and high-speed analog-to-digital conversion unit.

[0132] The fast spectrum analysis in step S402 specifically includes FFT pre-sampling and bandwidth detection.

[0133] In this embodiment, sampling is performed to reduce the data transmission rate and alleviate the pressure on back-end processing. Assuming the sampling frequency of the analog-to-digital converter is 40 MHz and the resolution is 14 bits, the data rate can reach 560 million samples per second. This is a burden on real-time imaging and increases the system's computational cost.

[0134] In this embodiment, step S4 uses a multi-resolution analog-to-digital conversion unit to dynamically switch the gain and sampling bit width based on the input signal amplitude. For weak photoacoustic signals, the unit automatically switches to high gain and small bit width (e.g., 16-bit high precision). For high-amplitude ultrasonic signals, the unit switches to low gain and wideband sampling to prevent saturation distortion. A Δ∑ modulation and pipeline structure are used to achieve fast sampling switching.

[0135] like Figure 2 As shown, specifically, the modeling process of the focus adjustment module in step S5 is:

[0136] S501: Delay the ultrasonic signal and the photoacoustic signal by a delay module to obtain an aligned multi-channel ultrasonic signal and photoacoustic signal;

[0137] S502: performing envelope extraction on the multi-channel ultrasonic signal and photoacoustic signal in S501, and superimposing the ultrasonic signal and photoacoustic signal of each channel respectively.

[0138] like Figure 3 As shown, specifically, the delay process of the delay module in step S501 is:

[0139] S501-1: Obtain a system clock, and perform frequency division, frequency multiplication, phase adjustment, and duty cycle adjustment on the system clock through a phase-locked loop to output a stable clock;

[0140] S501-2: Generate a logic control signal through a waveform generator based on the stable clock and the ultrasonic signal;

[0141] S501 - 3 : Delaying the logic control signal through a shift register to obtain a delayed control signal.

[0142] Figure 3 The phase selection module is used because, after downsampling, the effective data samples become sparser on the time axis, so the interpolation accuracy required to achieve the same delay resolution also increases. Phase rotation can overcome the problem of reduced integer delay accuracy caused by the reduction in available samples.

[0143] The envelope extraction in S502 mainly uses a hardware IQ demodulator. I is the abbreviation of in-phase and Q is the abbreviation of quadrature. The signal can be decomposed into in-phase and quadrature components: n (t)=I(t)cos(ω c t)+Q(t)sin(ω c t). Original signal It can be expressed as an envelope and frequency ω c The product of the cosine signal (carrier) and the envelope (the envelope can be seen intuitively by writing it in natural exponential form using Euler's formula). Therefore, the envelope can be extracted using IQ demodulation: For signals from multiple channels, you need to add the I and Q values ​​separately and then take the square root.

[0144] In this embodiment, Altera's EP4CE10F17C8N chip, a member of the Cyclone IV E series, is used as the master control chip. It contains a rich set of logic cells and ample available I / O pins, meeting the module design requirements. A 50MHz crystal oscillator is used as the clock signal input to ensure source synchronization of the FPGA clock and meet the clock requirements of other components within the system. The phase delay module is programmed using Verilog HDL, developed in Quartus II 13.1, and simulated on ModelSim 10.4. The phased array excitation unit utilizes a switch-mode amplifier, with the power amplifier circuit built around it.

[0145] Specifically, the process of multimodal fusion output in step S6 is as follows:

[0146] S601: Reconstructing the attenuation of the ultrasonic pulse inside the imaging target by maximum value mapping to obtain structural information;

[0147] S602: Using a deconvolution point spread function approach, reconstruct the absorption of the laser pulse by the imaging target (blood vessel and blood therein) to obtain specific information;

[0148] S603: Read the pre-stored acquisition timestamp and align the acquisition time;

[0149] S604: Superimpose the ultrasound image and the photoacoustic imaging result to complete the fusion of the ultrasound modality and the photoacoustic modality.

[0150] The deconvolution of S602 uses a least mean square process with iterative weight updates combined with a conjugate gradient algorithm to resolve the problem into a series of standard least mean square problems reweighted by the previous solution. The image degradation process model measured by the point spread function can be expressed as: g(s) = p(s)*o(s) + n(s)

[0151] Where s is the spatial coordinate of the image, * represents the two-dimensional convolution operation, g is the observed / acquired image, o is the original image, n is the noise, and p is the image degradation / blurring process, that is, the point spread function of the system. In the photoacoustic imaging system, the transducer bandwidth determines the resolution along the acoustic axis, that is, the axial resolution: R bw =0.8·c / f co .

[0152] Where c is the speed of sound, f co is the medium frequency of the transducer. The above formula shows that the upper limit of the axial resolution caused by the bandwidth is uniform in space. According to the image degradation model of formula 1, a calculation expression using vector matrix calculation can be generated: y = Cx + n

[0153] Among them, C is an L 2 ×N 2 , the convolution matrix containing the point spread function, x is N 2 The ideal image vector of ×1, and y and n are L 2 ×1 degraded image and noise vector. Ideally, ignoring noise, each point spread function is written as an M-order square matrix, while the image is also written as an L-order square matrix. Before performing matrix-vector multiplication, the ideal image x is first padded to an N-order square matrix (= M + L - 1) and then quantized. The C matrix is ​​generated using a similar procedure: the point spread function is padded with zeros and then quantized to generate the corresponding rows of the C matrix, with each row corresponding one-to-one to a pixel in x.

[0154] In this embodiment, a multimodal photoacoustic angiography system based on optical wavefront shaping and acoustic focusing includes a region matching module, an analog-to-digital conversion module, a signal focusing module, and a modality fusion module. The functions of each module are described as follows:

[0155] The region matching module is used to obtain a priori images, capture the target imaging area, and perform region positioning based on the priori images to output the coordinates of the optimal matching region, and obtain the photoacoustic signal of the optimal matching region coordinates through a laser;

[0156] The analog-to-digital conversion module is used to perform analog-to-digital conversion on the photoacoustic and ultrasonic signals to obtain digitized ultrasonic signals and photoacoustic signals;

[0157] The signal focusing module is used to obtain an enhanced ultrasonic signal by the ultrasonic and photoacoustic signals through the focusing adjustment module; the pulsed laser of the light source is focused by the wavefront shaping module to improve the directionality and intensity of the photoacoustic signal excited by it;

[0158] The hardware signal preprocessing module is used to perform preliminary amplification and filtering on the original signal from the transducer, eliminate DC to enhance the signal dynamic range, and maximize the performance of the analog-to-digital conversion module;

[0159] The modality fusion module is used to perform multimodal fusion of the enhanced ultrasound signal and the enhanced photoacoustic signal to output an angiography image.

[0160] Figure 1 In the figure, LNA, namely Low Noise Amplifier, refers to low noise amplifier; VCA, namely Voltage Control Attenuator, refers to voltage controlled attenuator; PGA, namely Programmable Gain Amplifier, refers to programmable gain amplifier; LPF, namely Low Pass Filter, refers to low pass filter; ADC, namely Analog Digital Converter, refers to analog-to-digital converter.

[0161] A delay control mechanism based on a phase-locked loop (PLL) stable clock and shift registers is adopted, combined with a phased array excitation module to achieve precise multi-channel timing control, dynamically form an ultrasound beam with adjustable focus, effectively adapt to tissue heterogeneity and complex vascular structure, and improve signal focusing intensity and lateral resolution.

[0162] By constructing an image enhancement module and using the point spread function deconvolution method to restore the light absorption and pressure wave distribution in biological tissues, the ability to characterize the boundaries and contrast features of tiny blood vessels is significantly enhanced, overcoming the blur problem of traditional out-of-focus images and achieving high-fidelity, high-contrast restoration of biological tissue structures.

[0163] By effectively fusing tissue structure information with functional signal characteristics, the multi-scale resolution and microstructural tomography performance of angiographic images are enhanced to meet the needs of precise vascular function assessment. Ultrasound imaging, a common clinical imaging technique, can effectively utilize the acoustic impedance mismatch of biological tissues to provide anatomical information of biological tissues. Therefore, by fusing the anatomical results of ultrasound imaging with the specificity of photoacoustic imaging, it is possible to obtain the spatial distribution information of the target chromophore based on the existing anatomical information.

[0164] The technical solution of the present invention is a specific implementation of an angiography system. This imaging system (step 6) incorporates a corresponding point spread function deconvolution algorithm to restore vascular imaging and, combined with ultrasound imaging results, complete angiography. This solution includes front-end hardware for data acquisition, as well as image enhancement and reconstruction methods to process and restore the acquired raw data. Image enhancement alone, without the raw data, will not yield angiography results.

[0165] The technical solution of the present invention uses ultrasound and photoacoustic methods to obtain pressure wave signals, not optical signals. In this solution (step 6.1), the pressure wave signal is restored to the original blood vessel distribution, and this information is visualized in the form of a two-dimensional image, and image enhancement is performed on this two-dimensional image. If the receiving link ( Figure 1 、 2 If the optical signal is input in , 3, or 4), the angiography result cannot be obtained.

[0166] The present invention utilizes photoacoustic imaging as its primary imaging method, maintaining the functional imaging capabilities of fluorescein and enabling vascular imaging without the need for external contrast agents. Ultrasound is merely an auxiliary method, supplementing the spatial structure of photoacoustic angiography.

[0167] The specific implementation scheme of this embodiment can be found in the relevant descriptions in the above embodiments and will not be repeated here.

[0168] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0169] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is at least two.

[0170] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0171] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution device. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0172] Those skilled in the art will understand that all or part of the steps in the method for implementing the above-mentioned embodiment can be completed by instructing related hardware through a program, and the corresponding program can be stored in a computer-readable storage medium. When the program is executed, it includes one of the steps of the method embodiment or a combination thereof.

[0173] Furthermore, the functional units in the various embodiments of the present invention may be integrated into a single processing module, each unit may exist physically separately, or two or more units may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium.

[0174] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0175] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0176] The present invention employs a method, system, device, processor, and computer-readable storage medium for multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing. By optimizing the laser irradiation area through a region matching and positioning mechanism based on a priori images and optical wavefront shaping, the laser energy is more concentrated on the targeted microvascular region. This effectively overcomes the photoacoustic excitation depth limitation caused by scattering and absorption in biological tissue, improves laser energy utilization efficiency, lowers the laser threshold, reduces equipment costs, and significantly enhances the photoacoustic signal intensity and distribution uniformity in deep tissue. Ultimately, this achieves efficient multimodal photoacoustic and ultrasound fusion angiography based on optical wavefront shaping and acoustic focusing.

[0177] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. A method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, characterized in that: The method comprises the following steps: (1) obtaining a priori image, capturing a target imaging area, and combining the priori image to perform regional positioning and output optimal matching area coordinates, and stimulating the photoacoustic effect of the optimal matching area coordinates by laser; (2) Focusing the laser through the wavefront shaping module; (3) exciting the ultrasonic transducer to generate ultrasonic pulses through a pulse generator; (4) passing the photoacoustic pressure wave signal and the ultrasonic signal through an amplifying filter and an analog-to-digital converter in sequence; (5) The excited photoacoustic pressure wave and the ultrasonic signal are successively enhanced through the acoustic focusing adjustment module; (6) The digitized enhanced photoacoustic signal and the enhanced ultrasound signal are reconstructed and multimodal fusion is used to output angiography images.

2. The method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to claim 1, characterized in that: The regional positioning in step (1) specifically includes the following steps: (1.1) extracting features of the prior image and the target imaging area by feature extraction to construct a prior image feature map and a current frame feature map of the target imaging area; (1.2) Performing region matching on the prior image feature map and the current frame feature map of the target imaging area through similarity measurement to output the coordinates of the optimal matching area.

3. The method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to claim 1, characterized in that: The step (2) specifically includes the following steps: (2.1) Constructing a transfer matrix using the method of mapping the input structured light pattern and its corresponding measurement results; (2.2) After obtaining the transmission matrix, we can use the phase conjugation method to modulate the incident laser with a digital micromirror and focus it at any position on the output plane.

4. The method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to claim 1, characterized in that: The step (4) specifically includes the following steps: (4.1) performing a rapid spectrum analysis on the photoacoustic signal excited by the laser pulse to obtain a preliminary frequency range signal; wherein the rapid spectrum analysis specifically includes FFT pre-sampling and bandwidth detection; (4.2) sparsely sampling the preliminary frequency range signal using an adaptive compressed sensing modulator to obtain a perceptually compressed signal; (4.3) performing maximum norm approximation estimation on the perceived compressed signal to obtain a signal amplitude; (4.4) Adjust the amplifier gain based on the predicted signal amplitude to amplify the signal while ensuring the dynamic range; (4.5) The DC component extracted by the low-pass filter is eliminated by a bias current source to obtain the preliminary dynamic range enhanced ultrasonic signal and the preliminary dynamic range enhanced photoacoustic signal; (4.6) The signal is automatically converted into a digital signal according to the signal amplitude by a high-resolution and high-speed analog-to-digital conversion unit.

5. The method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to claim 1, wherein: The step (5) specifically includes the following steps: (5.1) Delaying the ultrasonic signal and the photoacoustic signal using a delay module to obtain aligned multi-channel ultrasonic signals and photoacoustic signals; wherein the delay control specifically includes the following steps: (5.1.1) Obtaining a system clock, dividing, multiplying, adjusting the phase, and adjusting the duty cycle of the system clock through a phase-locked loop to output a stable clock; (5.1.2) generating a logic control signal through a waveform generator based on the stable clock and the ultrasonic signal; (5.1.3) delaying the logic control signal by a shift register to obtain a delayed control signal; (5.2) performing envelope extraction on the multi-channel ultrasonic signal and the photoacoustic signal, and superimposing the ultrasonic signal and the photoacoustic signal of each channel respectively; wherein the envelope extraction includes hardware IQ demodulation.

6. The method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to claim 1, characterized in that: The step (6) specifically includes the following steps: (6.1) Reconstruct the attenuation of the ultrasound pulse inside the imaging target through maximum mapping to obtain structural information; (6.2) Using the deconvolution point spread function approach, reconstruct the absorption of the laser pulse by the imaging target to obtain specific information; (6.3) Read the pre-stored acquisition timestamp and align the acquisition time; (6.4) The ultrasound image is superimposed on the photoacoustic imaging results to complete the fusion of the ultrasound mode and the photoacoustic mode.

7. A system for multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, characterized in that: The system includes a region matching module, an analog-to-digital conversion module, a signal focusing module, a hardware signal preprocessing module, a modal fusion module, and a signal excitation module; The signal excitation module includes a nanosecond laser light source and an ultrasonic pulse generator. The laser light source is used to excite the laser light source to generate nanosecond pulses, irradiating the target imaging area to produce a photoacoustic effect; the ultrasonic pulse generator generates a voltage sufficient to excite the ultrasonic transducer to emit ultrasonic waves, and switches to modulate it into a pulse form. The region matching module is used to obtain a priori images, capture the target imaging area, and perform region positioning based on the priori images to output the coordinates of the optimal matching region, and obtain the photoacoustic signal of the optimal matching region coordinates through a laser; The analog-to-digital conversion module is connected to the area matching module and is used to perform analog-to-digital conversion on the photoacoustic and ultrasonic signals to obtain digitized ultrasonic signals and photoacoustic signals; The signal focusing module is connected to the analog-to-digital conversion module and is used to obtain an enhanced ultrasonic signal from the ultrasonic and photoacoustic signals through the focusing adjustment module, and to focus the pulsed laser of the light source through the wavefront shaping module; The hardware signal preprocessing module is connected to the signal focusing module and is used to perform preliminary amplification and filtering on the original signal from the transducer, eliminate DC to enhance the signal dynamic range, and maximize the performance of the analog-to-digital conversion module; The modality fusion module is connected to the hardware signal preprocessing module and is used to perform multimodal fusion of the enhanced ultrasound signal and the enhanced photoacoustic signal to output an angiography image.

8. A device for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, characterized in that: The device comprises: a processor configured to execute computer-executable instructions; A memory storing one or more computer-executable instructions, wherein when the computer-executable instructions are executed by the processor, the steps of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to any one of claims 1 to 6 are implemented.

9. A processor for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, characterized in that: The processor is configured to execute computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing as described in any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium, characterized in that A computer program is stored thereon, and the computer program can be executed by a processor to implement the various steps of the method for realizing multimodal photoacoustic angiography based on optical wavefront shaping and acoustic focusing as described in any one of claims 1 to 6.

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