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

Abstract

The present application relates to a kind of based on optical wavefront shaping and acoustic focusing to realize multimodal photoacoustic angiography method, comprising the following steps: carrying out regional positioning output optimal matching region coordinate, excitation optimal matching region coordinate photoacoustic effect;Focus on laser by wavefront shaping module;Through pulse generator excitation ultrasonic transducer generates ultrasonic pulse;Photoacoustic pressure wave signal and ultrasonic signal are in turn through amplification filter and analog-digital converter;The excited photoacoustic pressure wave and ultrasonic signal are in turn through acoustic focusing adjustment module enhancement;Digital enhancement photoacoustic signal and enhanced ultrasonic signal are carried out image reconstruction.The present application is based on optical wavefront shaping and acoustic focusing to realize multimodal photoacoustic angiography method, system, device, processor and its computer readable storage medium, improve laser energy utilization efficiency, reduce laser threshold, reduce equipment cost, improve deep tissue photoacoustic signal intensity and distribution uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of angiography, in particular to the field of angiography, and more particularly to a method, system, device, processor and computer readable storage medium for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing. BACKGROUND

[0002] With the increasing demand for imaging of blood vessel microstructure and function in clinical practice, photoacoustic imaging technology has gradually been widely used in the fields of angiography, tumor detection and tissue function analysis due to its advantages of high optical contrast, high directivity and ultrasonic resolution. The photoacoustic angiography technology can realize low-cost high-resolution imaging of blood vessel structure by exciting photoacoustic signals from target chromophores in biological tissues with laser, combined with a conventional ultrasonic imaging receiving system, and is particularly suitable for identifying small blood vessels and low-contrast tissue structures. However, the traditional photoacoustic imaging system still faces many challenges in practical application.

[0003] On the one hand, there are diffraction limits and tissue scattering problems in the optical excitation path. In the visible light band, the traditional optical microscope relies on ballistic light imaging. Since the intensity of the ballistic light decreases exponentially with the increase of the imaging depth, the imaging depth is about 100 microns. This leads to uneven propagation of photons in the tissue, limiting the excitation depth, especially when imaging deep microvascular structures, it is difficult to maintain sufficient signal-to-noise ratio, which manifests as low imaging resolution. The optical focusing method realized by adjusting the spatial distribution of the optical lens in the past does not take into account the influence of the biological tissue inside on the propagation of photons. Moreover, the lens focusing structure is heavy, precise and difficult to maintain, and the cost is high. In large-scale production, there may be waste caused by assembly errors, resulting in waste of resources.

[0004] On the other hand, the insufficient focusing ability of the transducer on the acoustic receiving side also leads to a decrease in spatial resolution, especially in areas with strong tissue heterogeneity or dense target blood vessel distribution. The focal point of the geometrically designed acoustic reflection probe in the past is fixed, and only clear imaging can be achieved at the fixed depth where the focal point is located, which cannot adapt to the needs of multi-layer imaging, affecting the clarity and tomographic effect of the image. In addition, the size of the transducer aperture and the size of the bandwidth are the main factors limiting the imaging resolution and imaging depth.

[0005] Finally, conventional photoacoustic imaging is limited by the cost of device manufacturing, making it difficult to use laser light sources with adjustable wavelength capabilities, such as optical parametric oscillators (OPO). A single optical wavelength can only image a small number of specific chromophores and determine their content. However, in biological tissue imaging, in addition to the content of the target chromophore, its distribution in the tissue cannot be ignored. For example, in angiography, not only is the blood feature in the blood vessel, such as blood oxygen saturation and flow rate information, concerned, but also the relative position of the blood vessel in the deep skin. Moreover, even if a multi-wavelength light source is used, the demixing of the multi-spectral algorithm also 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, dynamically regulate the enhanced spatial focusing capability, and thus improve the imaging depth, resolution, and multi-parameter characterization capability of angiography. Meanwhile, in terms of results, combining the advantages of photoacoustic imaging results and ultrasound imaging results, the two modalities are fused to better meet the actual needs of precision medicine and microvascular function research. SUMMARY

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

[0008] In order to achieve the above-mentioned purpose, the method, system, device, processor and computer readable storage medium based on optical wavefront shaping and acoustic focusing for realizing multi-modal photoacoustic angiography according to the present application are as follows:

[0009] The method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, the main feature of which is that the method comprises the following steps:

[0010] (1) acquiring a prior image, collecting a target imaging area, and outputting optimal matching region coordinates by combining the prior image for region positioning, and exciting the photoacoustic effect of the optimal matching region coordinates by a laser;

[0011] (2) focusing the laser by a wavefront shaping module;

[0012] (3) exciting an ultrasonic transducer to generate an ultrasonic pulse by a pulse generator;

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

[0014] (5) enhancing the excited photoacoustic pressure wave and the ultrasonic signal by an acoustic focusing adjustment module in sequence.

[0015] (6) Image reconstruction of the digitized enhanced photoacoustic signal and the enhanced ultrasound signal, and multi-modal fusion output of angiography images.

[0016] Preferably, the region positioning in step (1) specifically comprises the following steps:

[0017] (1.1) constructing a prior image feature map and a target imaging region current frame feature map by feature extraction of features of the prior image and the target imaging region;

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

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

[0020] (2.1) using a method of mapping an input structured light pattern and its corresponding measurement results to construct a transmission matrix;

[0021] (2.2) after obtaining the transmission matrix, a phase conjugation method can be used to modulate the incident laser with a digital micromirror, and focusing on any position of the output plane.

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

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

[0024] (4.2) performing sparse sampling on the preliminary frequency range signal through an adaptive compressive sensing modulator to obtain a sensing compressed signal;

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

[0026] (4.4) adjusting the gain of an amplifier according to the pre-estimated signal amplitude, and amplifying the signal under the condition of ensuring the dynamic range;

[0027] (4.5) extracting the direct current component through a low-pass filter to eliminate the direct current component by a bias current source, to obtain the preliminary dynamic range enhanced ultrasound signal and the preliminary dynamic range enhanced photoacoustic signal;

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

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

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

[0031] (5.2) extracting envelope of the multi-channel ultrasonic signal and photoacoustic signal, and superimposing the ultrasonic signal and photoacoustic signal of each channel.

[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) of delay control specifically includes the following steps:

[0035] (5.1.1) obtaining system clock, and outputting stable clock through phase-locked loop for frequency division, frequency multiplication, phase adjustment and duty cycle adjustment of the system clock;

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

[0037] (5.1.3) delaying the logic control signal through a shift register to obtain delay control signal.

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

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

[0040] (6.2) reconstructing the absorption of laser pulse by the imaging target through deconvolution point spread function to obtain specific information;

[0041] (6.3) reading the pre-stored acquisition time stamp to align the acquisition time;

[0042] (6.4) superimposing the ultrasonic image and the photoacoustic imaging result to complete the fusion of ultrasonic modal and photoacoustic modal.

[0043] The system for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, wherein the system comprises 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.

[0044] The signal excitation module comprises 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, irradiate the target imaging area to generate a photoacoustic effect, and the ultrasonic pulse generator generates a voltage sufficient to excite the ultrasonic transducer to emit ultrasonic waves and switch modulation into a pulse form.

[0045] The region matching module is used to acquire a prior image, collect a target imaging region, and combine the prior image to output optimal matching region coordinates for region positioning, and the laser obtains a photoacoustic signal of the optimal matching region coordinates.

[0046] The analog-digital conversion module is connected with the region matching module and is used to convert the photoacoustic and ultrasonic signals into digital ultrasonic and photoacoustic signals.

[0047] The signal focusing module is connected with the analog-digital conversion module and is used to enhance the ultrasonic and photoacoustic signals through a focusing adjustment module and focus the pulsed laser of the light source through a wavefront shaping module.

[0048] The hardware signal preprocessing module is connected with the signal focusing module and is used to preliminarily amplify and filter the original signal from the transducer, eliminate direct current to enhance the signal dynamic range, and maximize the performance of the analog-digital conversion module.

[0049] The modal fusion module is connected with the hardware signal preprocessing module and is used to perform multi-modal fusion on the enhanced ultrasonic and photoacoustic signals to output an angiogram.

[0050] The device for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing mainly comprises:

[0051] The processor is configured to execute computer executable instructions.

[0052] The memory stores one or more computer executable instructions, and the computer executable instructions are executed by the processor to realize the steps of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0053] The processor for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing is mainly characterized in that the processor is configured to execute computer executable instructions, and the computer executable instructions are executed by the processor to realize the steps of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0054] The computer readable storage medium is characterized in that a computer program is stored thereon, and the computer program can be executed by the processor to realize each step of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0055] The method, system, device, processor and computer readable storage medium for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing have the advantages that, by using the region matching and positioning mechanism based on prior images, the laser irradiation region is optimized by optical wavefront shaping, so that the laser energy is more concentrated on the targeted microvessel region, the problem of photoacoustic excitation depth limitation caused by biological tissue scattering and absorption is effectively overcome, the laser energy utilization efficiency is improved, the laser threshold is reduced, the equipment cost is reduced, and the photoacoustic signal intensity and distribution uniformity of deep tissue are significantly improved. Finally, the efficient angiography of multi-modal photoacoustic and ultrasonic fusion based on optical wavefront shaping and acoustic focusing is realized. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The signal receiving link block diagram of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing is a microcontroller.

[0057] Figure 2 The receiving focusing principle diagram of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0058] Figure 3 The intermediate process diagram of delay alignment of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0059] Figure 4 The DC bias elimination dynamic range enhancement diagram of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0060] Figure 5 The skin tissue temperature change simulation diagram of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing. DETAILED DESCRIPTION

[0061] In order to more clearly describe the technical content of the present application, the following further describes in combination with specific embodiments.

[0062] The method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing includes the following steps:

[0063] (1) acquiring a prior image, collecting a target imaging area, and combining the prior image to output optimal matching area coordinates, and exciting the photoacoustic effect of the optimal matching area coordinates by a laser;

[0064] (2) focusing the laser by a wavefront shaping module;

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

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

[0067] (5) enhancing the excited photoacoustic pressure wave and the ultrasonic signal through an acoustic focusing adjustment module in sequence;

[0068] (6) reconstructing the digital enhanced photoacoustic signal and the enhanced ultrasonic signal into images, and outputting a blood vessel angiogram through multi-modal fusion.

[0069] As a preferred embodiment of the present application, the step (1) of region positioning specifically comprises the following steps:

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

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

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

[0073] (2.1) using a method of mapping input structured light patterns and their corresponding measurement results to construct a transmission matrix;

[0074] (2.2) after obtaining the transmission matrix, the phase conjugation method can be used to modulate the incident laser with a digital micromirror, and focus on any position of the output plane.

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

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

[0077] (4.2) performing sparse sampling on the preliminary frequency range signal by an adaptive compressive sensing modulator to obtain a perceptual compression signal;

[0078] (4.3) maximum norm approximation estimation of the perceptual compressed signal to obtain signal amplitude;

[0079] (4.4) gain adjustment of the amplifier according to the pre-estimated signal amplitude, amplifying the signal under the condition of ensuring the dynamic range;

[0080] (4.5) the direct current 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;

[0081] (4.6) automatic conversion to digital signal by the high-resolution high-speed analog-to-digital conversion unit according to the signal amplitude;

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

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

[0084] (5.2) envelope extraction of the multi-channel ultrasonic signal and photoacoustic signal, and superposition of the ultrasonic signal and photoacoustic signal of each channel.

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

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

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

[0088] (5.1.1) obtaining system clock, frequency division, frequency multiplication, phase adjustment, duty cycle adjustment of the system clock by phase-locked loop to output stable clock;

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

[0090] (5.1.3) time delay of the logic control signal by shift register to obtain time delay control signal.

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

[0092] (6.1) reconstruction of the attenuation of ultrasonic pulse inside the imaging target by maximum value mapping to obtain structural information;

[0093] (6.2) Reconstructing the situation that the laser pulse is absorbed by the imaged target to obtain specific information by using the deconvolution point spread function;

[0094] (6.3) Reading the pre-stored acquisition time stamp to align the acquisition time;

[0095] (6.4) Superimposing the ultrasound image and the photoacoustic imaging result to complete the fusion of the ultrasound mode and the photoacoustic mode.

[0096] The system for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing comprises a region matching module, an analog-digital conversion module, a signal focusing module, a hardware signal preprocessing module, a modal fusion module and a signal excitation module.

[0097] The signal excitation module comprises 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, irradiate the target imaging area to generate a photoacoustic effect, and the ultrasonic pulse generator generates a voltage sufficient to excite the ultrasonic transducer to emit ultrasonic waves and is switched to a pulse form.

[0098] The region matching module is used to acquire a prior image, collect a target imaging area, and combine the prior image to output optimal matching region coordinates for region positioning, and obtain photoacoustic signals of the optimal matching region coordinates by a laser.

[0099] The analog-digital conversion module is connected with the region matching module and is used to convert the photoacoustic and ultrasonic signals into digital ultrasonic signals and photoacoustic signals.

[0100] The signal focusing module is connected with the analog-digital conversion module and is used to enhance ultrasonic signals by focusing adjustment of the ultrasonic and photoacoustic signals and focus the pulsed laser of the light source by a wavefront shaping module.

[0101] The hardware signal preprocessing module is connected with the signal focusing module and is used to preliminarily amplify and filter the original signals from the transducer, eliminate direct current to enhance the signal dynamic range, and maximize the performance of the analog-digital conversion module.

[0102] The modal fusion module is connected with the hardware signal preprocessing module and is used to perform multi-modal fusion of the enhanced ultrasonic signals and the enhanced photoacoustic signals to output an angiography image.

[0103] The device for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing comprises:

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

[0105] a memory storing one or more computer executable instructions that, when executed by the processor, implement the steps of the method for multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0106] The processor for multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present application, wherein the processor is configured to execute computer executable instructions that, when executed by the processor, implement the steps of the method for multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0107] The computer readable storage medium of the present application, on which a computer program is stored, the computer program can be executed by the processor to implement the steps of the method for multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing.

[0108] In the specific embodiment of the present application, a blood vessel imaging method with adjustable imaging depth, strong specificity, low cost, good result interpretation and clear imaging is provided, which belongs to the technical field of angiography. Based on the hardware of traditional ultrasonic imaging angiography, the problems of unclear results, poor specificity and unclear spatial distribution in traditional non-invasive angiography are solved. A feasible improvement scheme based on traditional ultrasonic imaging hardware equipment is provided.

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

[0110] S1: acquiring a prior image, collecting a target imaging area, and outputting optimal matching region coordinates by combining the prior image for region positioning; exciting the photoacoustic effect of the optimal matching region coordinates by a laser;

[0111] S2: focusing the laser by a wavefront shaping module to enhance the excited photoacoustic signal;

[0112] S3: exciting an ultrasonic transducer to generate an ultrasonic pulse by a pulse generator;

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

[0114] S5: enhancing the excited photoacoustic pressure wave and the ultrasonic signal in sequence by an acoustic focusing adjustment module;

[0115] S6: image reconstruction of the digitized enhanced photoacoustic signal and the enhanced ultrasonic signal, and multi-modal fusion output of an angiography image.

[0116] Specifically, the positioning process of the region positioning in the step S1 comprises:

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

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

[0119] Specifically, the structure of the probe in the step S1 is that a plurality of cluster fiber cores are additionally installed on both sides of an original ultrasonic transducer array probe to transmit light of a laser to a measured position; the output form of the laser is a collimated light beam, which is coupled to the multi-core multimode optical fiber by a collimation-to-fiber coupler after the wavefront shaping is completed in the step S2.

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

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

[0122] S201: using a method of mapping an input structured light mode and a corresponding measurement result to construct a transmission matrix.

[0123] S202: after obtaining the transmission matrix, a phase conjugation method can be used to modulate the incident laser by a digital micromirror (Digital Micromirror Devices, DMD), and focus on any position of the output plane. The complex light field of each output point can be represented as the superposition of multiple input light modes, that is, E in =T H E out . Wherein T is the transmission matrix.

[0124] One row vector of the transmission matrix needs to traverse all input modes of the structured light modulator. Under this physical model, the essence of realizing the focusing of the light field at a specific position E m is to maximize the amplitude of the light field at the target position. To achieve this goal, the phase mode of the structured light is obtained, and then the rotation and alignment of all phases are realized.

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

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

[0127] S402: performing sparse sampling on the preliminary frequency range signal by an adaptive compressive sensing modulator to obtain a sensing compressed signal;

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

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

[0130] S405: as shown, Figure 4 the direct current component extracted by the low-pass filter is eliminated by a bias current source, and the preliminary dynamic range enhanced ultrasonic signal and the preliminary dynamic range enhanced photoacoustic signal are obtained;

[0131] S406: automatically converting into a digital signal by a high-resolution high-speed analog-to-digital conversion unit according to the signal amplitude.

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

[0133] In the embodiment, sampling is performed to reduce the data transmission rate and relieve the pressure of the backend processing. Assuming that 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 for imaging real-time performance and increases the computing cost of the system.

[0134] In the embodiment, the step S4 uses a multi-resolution analog-to-digital conversion unit to dynamically switch the gain and sampling bit width according to the input signal amplitude. Under weak photoacoustic signals, it is automatically switched to high gain and small bit width (such as 16-bit high precision); under large amplitude ultrasonic signals, it is switched to low gain wideband sampling to prevent saturation distortion; and a delta-sigma modulation + pipeline structure is used to realize fast sampling switching.

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

[0136] S501: performing delay control on the ultrasonic signal and the photoacoustic signal by a delay module to obtain aligned multi-channel ultrasonic signals and photoacoustic signals;

[0137] S502: Envelope extraction is performed on the multi-channel ultrasonic signal and the photoacoustic signal in S501, and the ultrasonic signal and the photoacoustic signal of each channel are superimposed respectively.

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

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

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

[0141] S501-3: Delay the logic control signal by a shift register to obtain a delay control signal.

[0142] Figure 3 In the step S501, the phase selection module is used because: after down-sampling, the effective data samples become more sparse on the time axis, so the interpolation accuracy required to achieve the same delay resolution is also improved. Phase rotation can overcome the problem of reduced integer delay accuracy caused by the reduction of available samples.

[0143] In S502, envelope extraction mainly uses a hardware IQ demodulation device. I is the abbreviation of in-phase, and Q is the abbreviation of quadrature. A signal can be decomposed into in-phase and quadrature components: x n (t) = I(t)cos(ω c t) + Q(t)sin(ω c t). The original signal can be represented as the product of the envelope and the cosine signal (carrier) with a frequency of ω c . (The envelope can also be written in natural exponential form using Euler's formula, which can be seen directly.) Thus, the envelope can be extracted by IQ demodulation: For multiple channel signals, I and Q need to be superimposed and then the square root is taken.

[0144] In the embodiment, an EP4CE10F17C8N chip of Altera Company is used as the master control chip, the master control chip belongs to a Cyclone IV E series, a large number of logic units and sufficient available I / O pins are internally contained, and the module design requirement is met. A crystal oscillator with a frequency of 50MHz is used as a clock signal input to guarantee source synchronization of the FPGA clock and meet the clock needs of other structures in the system. A phase delay module is programmed using Verilog HDL, a development environment is Quartus II 13.1, and a simulation platform is ModelSim 10.4. A switch mode amplifier is used for the phased array excitation unit, and a power amplification circuit is built around the amplifier.

[0145] Specifically, the process of the multi-modal fusion output in the step S6 is:

[0146] S601: The attenuation of the ultrasonic pulse inside the imaging target is reconstructed by a maximum value mapping method to obtain structure information;

[0147] S602: The absorption of the laser pulse by the imaging target (blood vessels and blood therein) is reconstructed by using a deconvolution point spread function method to obtain specific information;

[0148] S603: A pre-stored acquisition time stamp is read to align the acquisition time;

[0149] S604: The ultrasonic image and the photoacoustic imaging result are superimposed to complete the fusion of the ultrasonic modal and the photoacoustic modal.

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

[0151] Wherein, s is the spatial coordinate of the image, * represents a 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] Wherein, c is the sound velocity, and f co is the medium frequency of the transducer. The above formula shows that the axial resolution upper limit caused by the bandwidth is spatially uniform. According to the image degradation model of formula 1, a calculation expression calculated using a vector matrix can be generated: y = Cx + n

[0153] where C is an L 2 x N 2 matrix containing the point spread functions, x is an N 2 x 1 ideal image vector, and y and n are L 2 x 1 degraded image and noise vectors, respectively. In the ideal case, the noise is ignored and each point spread function is written as an M x M matrix, while the image is written as an L x L matrix. Before matrix-vector multiplication, the ideal image x is padded to an N (= M + L - 1) x N matrix and vectorized. The C matrix is generated following a similar procedure, where the point spread functions are zero-padded, vectorized, and the resulting vectors are used to generate the rows of the C matrix, each of which corresponds to a pixel in x.

[0154] In the embodiment, a multi-modal 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 modal fusion module, and the functions of each module are described as follows.

[0155] The region matching module is configured to acquire a prior image, collect a target imaging region, and output optimal matching region coordinates by combining the prior image for region positioning, and obtain photoacoustic signals of the optimal matching region coordinates through a laser.

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

[0157] The signal focusing module is configured to obtain enhanced ultrasonic signals by adjusting the ultrasonic and photoacoustic signals through a focusing adjustment module, and improve the directivity and intensity of the photoacoustic signals excited by the light source by focusing the pulsed laser of the light source through a wavefront shaping module.

[0158] The hardware signal preprocessing module is configured to perform preliminary amplification and filtering processing on the original signals from the transducer, eliminate direct current to enhance the dynamic range of the signals, and maximize the performance of the analog-to-digital conversion module.

[0159] The modal fusion module is configured to perform multi-modal fusion on the enhanced ultrasonic signals and the enhanced photoacoustic signals to output an angiography image.

[0160] Figure 1 In the embodiment, LNA, which stands for Low Noise Amplifier, VCA, which stands for Voltage Control Attenuator, PGA, which stands for Programmable Gain Amplifier, LPF, which stands for Low Pass Filter, and ADC, which stands for Analog Digital Converter.

[0161] A delay control mechanism based on a phase-locked loop-stabilized clock and a shift register is adopted, combined with a phased array excitation module to achieve precise timing control of multiple channels, dynamically forming an adjustable-focus ultrasound beam, effectively adapting to tissue heterogeneity and complex vascular structures, and improving signal focusing intensity and lateral resolution.

[0162] By constructing an image enhancement module, the light absorption and pressure wave distribution in biological tissues are restored using the point spread function deconvolution method. This significantly enhances the ability to characterize the boundaries and contrast features of microvessels, overcomes the blurring problem of traditional defocused images, and achieves high-fidelity, high-contrast restoration of biological tissue structures.

[0163] By effectively fusing tissue structure information and functional signal characteristics, the multi-scale resolution and microstructure tomography performance of angiography images can be improved, meeting the needs of precise vascular function assessment. Ultrasound imaging, as a common clinical imaging technique, can effectively utilize the acoustic impedance mismatch of biological tissues to provide anatomical information. Therefore, by modal fusion of the anatomical results from ultrasound imaging with the specificity of photoacoustic imaging, spatial distribution information of target chromophores can be obtained based on existing anatomical information.

[0164] The technical solution of this invention is a specific implementation of an angiography system. In this imaging system, step 6 includes a corresponding point spread function deconvolution algorithm to reconstruct the vascular imaging and, combined with ultrasound imaging results, complete the angiography. This solution includes front-end hardware for data acquisition, as well as image enhancement and image reconstruction methods to process and reconstruct the acquired raw data. Angiography results cannot be obtained with only image enhancement methods and without the original data.

[0165] The technical solution of this 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 as a two-dimensional image. Image enhancement is then performed on this two-dimensional image. If the receiving link in this solution is directly used... Figure 1 , 2 If optical signals are input in (3, 4), angiography results cannot be obtained.

[0166] The technical solution of this invention uses photoacoustic imaging as the primary imaging method, possessing the functional imaging capabilities of fluorescein and enabling vascular imaging without the external introduction of contrast agents. Ultrasound is used only as a supplementary, auxiliary method to photoacoustic angiography, providing spatial structural detail.

[0167] For the specific implementation scheme of this embodiment, please refer to the relevant descriptions in the above embodiments, which will not be repeated here.

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

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

[0170] Any process or method descriptions in flow charts or described herein otherwise can be understood as representing code modules, segments, or portions of code that include one or more executable instructions for performing specific logic functions or steps in the process, and the various embodiments of the present application include additional implementations in which the order of steps can be different, including use of a different order of executing hardware steps, or executing hardware steps in substantially simultaneous with each other, or in reverse order, all of which are within the scope of embodiments of the present application, as will be understood by those of ordinary skill in the art.

[0171] It should be understood that parts of the present application can be realized in hardware, software, firmware or a combination thereof. In the above embodiments, a plurality of steps or methods can be realized by software or firmware stored in a memory and executed by a suitable instruction execution device. For example, if realized in hardware, and as in another embodiment, it can be realized by any one or a combination of the following technologies known in the art: discrete logic circuit with logic gate circuit for implementing logic functions on data signals, application specific integrated circuit with suitable combination logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA) and the like.

[0172] Those of ordinary skill in the art can understand that all or part of the steps carried out by the above-mentioned embodiments can be instructed by a program to complete the relevant hardware, and the corresponding program can be stored in a computer readable storage medium, which includes one or a combination of the steps of the method embodiments when executed.

[0173] In addition, each functional unit in each embodiment of the present application can be integrated in one processing module, or each unit can exist physically separately, or two or more units can be integrated in one module. The above integrated module can be realized in the form of hardware or in the form of a software function module. If the integrated module is realized in the form of a software function module and sold or used as an independent product, it can 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] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0176] The method, system, device, processor and computer readable storage medium thereof for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing of the present application, through the region matching and positioning mechanism based on prior image, combined with the optimization of laser irradiation area by optical wavefront shaping, makes the laser energy more concentrated on the targeted microvessel area, effectively overcomes the problem of photoacoustic excitation depth limitation caused by biological tissue scattering and absorption, improves the energy utilization efficiency of the laser, reduces the laser threshold, reduces the equipment cost, and significantly improves the photoacoustic signal intensity and distribution uniformity of the deep tissue. Finally, the multi-modal photoacoustic and ultrasonic fusion efficient angiography based on optical wavefront shaping and acoustic focusing is realized.

[0177] In this specification, the present application has been described with reference to its specific embodiments. However, it is obvious that various modifications and changes can be made without departing from the spirit and scope of the present application. Therefore, the specification and drawings should be considered as illustrative rather than limiting.

Claims

1. A method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, characterized in that, The method comprises the following steps: (1) obtaining a prior image, collecting a target imaging area, and combining the prior image to output optimal matching area coordinates for region positioning, and exciting the photoacoustic effect of the optimal matching area coordinates by a laser; (2) focusing the laser by a wavefront shaping module; (3) exciting the ultrasonic transducer to generate ultrasonic pulses by a pulse generator; (4) passing the photoacoustic pressure wave signal and the ultrasonic signal through an amplification filter and an analog-to-digital converter in sequence; (5) enhancing the excited photoacoustic pressure wave and the ultrasonic signal through an acoustic focusing adjustment module; (6) reconstructing the digital enhanced photoacoustic signal and the enhanced ultrasonic signal into images, and outputting a blood vessel angiogram through multi-modal fusion. 2.The method of claim 1, wherein, The region positioning in step (1) comprises the following steps: (1.1) extracting the features of the prior image and the target imaging area to construct a prior image feature map and a target imaging area current frame feature map; (1.2) performing region matching on the prior image feature map and the target imaging area current frame feature map through similarity measurement to output the optimal matching area coordinates. 3.The method of claim 1, wherein, The step (2) comprises the following steps: (2.1) using a method of mapping input structured light patterns and their corresponding measurement results to construct a transmission matrix; (2.2) after obtaining the transmission matrix, the phase conjugation method can be used to modulate the incident laser with a digital micromirror, and focus on any position on the output plane. 4.The method of claim 1, wherein, The step (4) comprises the following steps: (4.1) performing fast spectral analysis on the photoacoustic signal excited by the laser pulse to obtain a preliminary frequency range signal; wherein the fast spectral analysis comprises FFT pre-sampling and bandwidth detection; (4.2) performing sparse sampling on the preliminary frequency range signal through an adaptive compressive sensing modulator to obtain a sensing compressed signal; (4.3) performing maximum norm approximation estimation on the sensing compressed signal to obtain a signal amplitude; (4.4) adjusting the gain of the amplifier according to the pre-estimated signal amplitude, and amplifying the signal under the condition of ensuring the dynamic range; (4.5) eliminating the direct current component extracted by the low-pass filter by the bias current source to obtain a preliminary dynamic range enhanced ultrasonic signal and a preliminary dynamic range enhanced photoacoustic signal; (4.6) automatically converting the signal into a digital signal through a high-resolution high-speed analog-to-digital conversion unit according to the signal amplitude.

5. The method of claim 1, wherein, The step (5) comprises the following steps: (5.1) delaying the ultrasonic signal and the photoacoustic signal through a delay module to obtain aligned multi-channel ultrasonic signals and photoacoustic signals; wherein the delay control comprises the following steps: (5.1.1) obtaining a system clock, and outputting a stable clock through phase-locked loop frequency division, frequency multiplication, phase adjustment, and duty cycle adjustment on the system clock; (5.1.2) generating a logic control signal based on the stable clock and the ultrasonic signal through a waveform generator; (5.1.3) delaying the logic control signal through a shift register to obtain a delay control signal; (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; wherein the envelope extraction comprises hardware IQ demodulation.

6. The method of claim 1, wherein, The step (6) specifically comprises the following steps: (6.1) The attenuation of the ultrasonic pulse inside the imaging target is reconstructed by maximum mapping to obtain structural information; (6.2) The absorption of the laser pulse by the imaging target is reconstructed by using the deconvolution point spread function to obtain specific information; (6.3) The pre-stored acquisition time stamp is read to align the acquisition time; (6.4) The ultrasonic image and the photoacoustic imaging result are superimposed to complete the fusion of the ultrasonic mode and the photoacoustic mode.

7. An apparatus for realizing multi-modal 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, which, when executed by the processor, implement each step of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to any one of claims 1 to 6.

8. A processor for implementing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing, the processor comprising: The processor is configured to execute computer executable instructions, which, when executed by the processor, implement each step of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, A computer program is stored thereon, which can be executed by the processor to implement each step of the method for realizing multi-modal photoacoustic angiography based on optical wavefront shaping and acoustic focusing according to any one of claims 1 to 6.

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