A deep lesion tissue precise positioning guide system and device based on photoacoustic imaging

Abstract

The application belongs to the field of medical imaging, and particularly relates to a deep lesion tissue precise positioning guide system and device based on photoacoustic imaging. The application firstly processes photoacoustic signals to obtain original digital signals and performs frequency domain filtering on the original digital signals to obtain high-frequency digital signals; then performs correlation operation and demodulation processing on the high-frequency digital signals and a preset matching signal to obtain an envelope signal; in order to further eliminate invalid interference signals, the envelope signal is screened according to statistical distribution characteristics of the envelope signal, so that signal purity and reliability are greatly improved; finally, the sound wave arrival time of each receiving unit of an ultrasonic transducer is calculated according to the time characteristic point of the effective envelope signal; according to the position of each receiving unit of the ultrasonic transducer and the arrival time, a multi-point positioning algorithm is introduced to calculate and obtain the three-dimensional space position of the target tissue; the application can directly and accurately determine the real position information of the target tissue to be removed, and realizes high efficiency, real-time and intelligence in the positioning process.

Description

Technical Field

[0001] This invention belongs to the field of medical imaging, specifically relating to a precise positioning and guidance system and device for deep lesions based on photoacoustic imaging. Background Technology

[0002] In surgical resection of soft organs such as the lungs and breasts, the lesion often presents as a deep micro-tumor or nodule (hereinafter referred to as "target tissue"), which is not visible on the body surface, difficult to directly touch during surgery, and completely surrounded by normal tissue. For the above-mentioned deep micro-tumor or nodule, surgical resection is usually the preferred treatment option. The ability to achieve real-time and accurate localization of the lesion during surgery directly determines the radical resection effect of the surgery.

[0003] For the localization and guidance of small tumors or nodules deep within soft organs such as the lungs and breasts, existing technologies mainly include the following categories, but all have certain limitations: Percutaneous puncture with physical or liquid marking (such as hook wire, microcoil, methylene blue, radioactive tracer, etc.) is currently the most commonly used method. The principle is to place the marker near the target tissue under the guidance of computed tomography before the operation, and to find the marker by palpation or detection equipment during the operation. However, this technique has problems such as marker detachment or liquid diffusion leading to blurred boundaries, and there are certain difficulties in locating markers in deep tissues. Transbronchial positioning techniques (such as electromagnetic navigation bronchoscopy and radial endobronchial ultrasound) use an external magnetic field or ultrasound probe to guide the patient to the peripheral lung field, inject staining agents or place markers. The incidence of complications such as pneumothorax is significantly lower than that of percutaneous puncture. However, due to respiratory motion, the dynamic interventional device trajectory is difficult to accurately integrate with the static three-dimensional anatomical image, and the positive diagnostic rate is low. Intraoperative ultrasound localization displays deep lesions in real time by placing the probe directly on the surface of the organ. It is radiation-free and can be repeated. However, in air-containing organs such as the lungs, the ultrasound energy is significantly attenuated due to residual gas in the alveoli, producing artifacts that prevent deep nodules from being visualized. In the breast, it is highly dependent on the operator's experience and lesions are easily missed in two-dimensional sections. Radiofrequency magnetic positioning and tagging technology (such as radio frequency identification tags or magnetic tracer seeds) is implanted percutaneously and signals are received by a handheld detector during the operation. It can be implanted several days in advance and the operation time can be shortened, but it is still invasive and only provides static positioning guidance. Fluorescence and near-infrared optical imaging use fluorescent probes to enrich around the target tissue and capture signals through a near-infrared endoscope to display the boundary. However, due to the strong scattering and absorption of near-infrared light by biological tissue, the effective penetration depth is only a few millimeters to more than ten millimeters, and it cannot directly locate deep, unexposed lesions.

[0004] Existing technologies have proposed solutions to the challenge of precise tumor resection and localization in relevant patents. For example, patent CN109310363A integrates an ultrasonic transducer into the surgical instrument and uses trilateration to calculate the relative distance between the guidewire and the instrument; patent CN114587591A implants the lesion localization source and the scalpel localization source into photoacoustic sources respectively, and uses ultrasonic radar (composed of three miniature ultrasonic transducers) to obtain their positions. However, both solutions use a fixed number of transducers and do not involve an analysis of the impact of transducer array layout on localization accuracy. At the same time, at the localization algorithm level, there is a lack of specific processing procedures for the original photoacoustic signals and a systematic method for quantifying and evaluating localization errors. Therefore, how to achieve high-precision estimation of lesion location and quantify its error through optimized transducer array design and high-precision localization algorithms without the need for external markers remains an unresolved problem in current technology.

[0005] In summary, existing technologies generally suffer from insufficient penetration depth, are greatly affected by tissue deformation, provide only static guidance, and cannot provide accurate positioning information during surgery. Therefore, there is an urgent need to develop a dynamic positioning and guidance system that can achieve real-time, high-precision positioning of deep lesions during surgery. Summary of the Invention

[0006] To overcome the limitations of existing intraoperative positioning and guidance technologies for deep small tumors or nodules in soft organs such as the lungs and breasts, which suffer from insufficient penetration depth for deep tissue positioning, are greatly affected by tissue deformation, provide only static guidance, and cannot provide accurate positioning information during surgery, this invention designs a precise positioning and guidance system and device for deep lesions based on photoacoustic imaging. The system combines an optical fiber with a metal positioning device at its end, and implants the positioning device into the area of ​​the tissue to be removed through percutaneous puncture before surgery. During surgery, the position information of the positioning device is calculated using photoacoustic imaging technology, thereby achieving real-time acquisition of the position information of deep lesions during the resection surgery.

[0007] This invention proposes a precise localization and guidance system for deep lesions based on photoacoustic imaging, the system comprising: Pulsed laser module, used to generate nanosecond pulsed lasers; The guiding excitation module, connected to the pulsed laser module, includes an excitation device, a connection device, and a positioning device connected in sequence; the nanosecond pulsed laser generates a photoacoustic signal by exciting a photoacoustic signal source located in the target tissue, the photoacoustic signal source being either the positioning device or a chromophore with high absorption rate; The signal receiving module receives photoacoustic signals from the surface of the target tissue via an ultrasonic transducer, processes them to obtain raw digital signals, and then transmits them to the data processing module. The data processing module performs frequency domain filtering on the original digital signal to extract high-frequency digital signals; performs correlation operations on the high-frequency digital signals and demodulates them with a preset matching signal to obtain an envelope signal; filters valid envelope signals based on the statistical distribution characteristics of the envelope signals; calculates the time of arrival (TOA) of the sound waves of each receiving unit of the ultrasonic transducer based on the time feature points of the valid envelope signals; and executes a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue based on the position of each receiving unit and the TOA of the sound waves.

[0008] The deep lesion tissue precise positioning guidance system proposed in this invention also includes: The display module is used to visualize the location in three-dimensional space. The control module is used for synchronous control and management of the entire system.

[0009] Specifically, the pulsed laser module includes a pulsed laser, a coupling lens group, and a first multimode fiber; wherein the pulsed laser is used to generate nanosecond pulsed laser, the coupling lens group is used to shape the nanosecond pulsed laser, and the shaped nanosecond pulsed laser is coupled into the first multimode fiber and transmitted to the guiding excitation module.

[0010] Specifically, in the data processing module, a high-frequency filter is used to achieve frequency domain filtering. The preset matching signal is generated by the matching filter and demodulated by Hilbert transform to obtain the envelope signal. The skewness threshold is used as a screening index for statistical distribution characteristics. The sampling time corresponding to the maximum value of the effective envelope signal is taken and multiplied by the sampling interval to obtain the arrival time of the sound waves of each receiving unit of the ultrasonic transducer.

[0011] This invention also proposes a precise positioning and guidance device for deep lesions based on photoacoustic imaging, the device comprising: Pulsed laser equipment used to generate nanosecond pulsed lasers; The guiding excitation device, connected to the pulsed laser device, includes an excitation device, a connection device, and a positioning device connected in sequence; the nanosecond pulsed laser generates a photoacoustic signal by exciting a photoacoustic signal source located in the target tissue, the photoacoustic signal source being either the positioning device or a chromophore with a high absorption rate; The signal receiving device receives photoacoustic signals from the surface of the target tissue through an ultrasonic transducer, processes them to obtain raw digital signals, and then transmits them to the data processing device. The data processing device performs frequency domain filtering on the original digital signal to extract high-frequency digital signals; performs correlation operations on the high-frequency digital signals and demodulates them with a preset matching signal to obtain an envelope signal; filters effective envelope signals based on the statistical distribution characteristics of the envelope signals; calculates the arrival time of sound waves of each receiving unit of the ultrasonic transducer based on the time feature points of the effective envelope signals; and executes a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue based on the position and arrival time of each receiving unit.

[0012] The deep lesion tissue precise positioning and guidance device proposed in this invention also includes: Display devices are used to visualize three-dimensional spatial positions; Control equipment is used to synchronously control and manage the entire system.

[0013] Compared with the prior art, the present invention has the following advantages: (1) The present invention first processes the photoacoustic signal to obtain the original digital signal and performs frequency domain filtering to obtain the high-frequency digital signal; then performs correlation operation and demodulation processing on the high-frequency digital signal and the preset matching signal to obtain the envelope signal; in order to further eliminate invalid interference signals, the statistical distribution characteristics of the envelope signal are used to screen the effective envelope signal, which greatly improves the signal purity and reliability; finally, the arrival time of the sound wave of each receiving unit of the ultrasonic transducer is calculated according to the time feature points of the effective envelope signal; according to the position and arrival time of each receiving unit, a multi-point positioning algorithm is introduced to calculate the three-dimensional spatial position of the target tissue; the present invention can directly and accurately determine the real position information of the target tissue to be removed, and realize the efficiency, real-time and intelligent positioning process.

[0014] (2) This invention couples nanosecond pulsed laser into an optical fiber, and sends the light into the tissue through the optical fiber, causing the positioning device or chromophore in the area to be removed to excite photoacoustic signals. Then, an ultrasonic probe is used to receive the photoacoustic signals excited in the area to be removed on the surface of the tissue. Finally, the received photoacoustic signals are processed by photoacoustic imaging technology to obtain the position of the positioning device or chromophore in the area to be removed, thereby obtaining the location information of the deep lesion tissue to be removed. This system makes full use of the dual advantages of photoacoustic imaging, which has the high specificity of optical imaging for tissue components and the deep penetration capability of acoustic imaging. It can accurately locate deep tissues, provide surgeons with clear location information of the tissue to be removed, minimize the surgical resection range of the lesion area of ​​the patient, and avoid unnecessary damage to the patient. In addition, this invention can solve the problem of positioning deviation caused by the soft texture of tissue organs and easy deformation during surgery when positioning the guidewire before surgery, and avoid the situation where the guidewire travel path is difficult to predict and cannot accurately point to the deep target tissue. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A block diagram of a precise localization and guidance system for deep lesions based on photoacoustic imaging provided by the present invention; Figure 2 This is a schematic diagram illustrating the implementation of the guiding and excitation module used in this invention; Figure 3 This is a schematic diagram illustrating the usage process of the positioning and guidance system proposed in this invention; Figure 4 This is a flowchart illustrating the usage process of the positioning and guidance system proposed in this invention. Figure 5 This is a waveform diagram showing the result of the data processing process in this invention; Figure 6 This is a diagram showing the positioning results of the multi-point positioning algorithm based on sound wave arrival time according to the present invention. Detailed Implementation

[0017] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0018] like Figure 1 As shown, this invention proposes a precise localization and guidance system for deep lesions based on photoacoustic imaging, the system comprising: Pulsed laser module 1 is used to generate nanosecond pulsed lasers; The guiding excitation module 2 is connected to the pulsed laser module 1 and includes an excitation device 2.1, a connecting device 2.2, and a positioning device 2.3 connected in sequence. The nanosecond pulsed laser generates a photoacoustic signal by exciting a photoacoustic signal source located in the target tissue. The photoacoustic signal source is either the positioning device 2.3 or a chromophore 2.1.4 with a high absorption rate. The signal receiving module 3 receives the photoacoustic signal from the surface of the target tissue through the ultrasonic transducer 3.1, processes it to obtain the raw digital signal, and then transmits it to the data processing module 4. Data processing module 4 performs frequency domain filtering on the original digital signal to extract high-frequency digital signals; performs correlation operations on the high-frequency digital signals and a preset matching signal and demodulates them to obtain an envelope signal; filters effective envelope signals based on the statistical distribution characteristics of the envelope signals; calculates the arrival time of sound waves of each receiving unit of the ultrasonic transducer 3.1 based on the time feature points of the effective envelope signals; and executes a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue based on the position of each receiving unit and the arrival time of sound waves.

[0019] The deep lesion tissue precise positioning guidance system proposed in this invention also includes: Display module 5 is used to visualize the three-dimensional spatial position; Control module 6 is used for synchronous control and management of the entire system.

[0020] Specifically, the pulsed laser module 1 includes a pulsed laser 1.1, a coupling lens group 1.2, and a first multimode fiber 1.3; wherein the pulsed laser 1.1 is used to generate nanosecond pulsed laser, the coupling lens group 1.2 is used to shape the nanosecond pulsed laser, and the shaped nanosecond pulsed laser is coupled into the first multimode fiber 1.3 and transmitted to the guiding excitation module 2; since the basic process of photoacoustic imaging begins with the target tissue receiving nanosecond pulsed laser irradiation, and the nanosecond pulsed laser is absorbed by specific molecules after passing through the target tissue, generating instantaneous thermal expansion, and then radiating ultrasonic signals, this module needs to control parameters such as the output wavelength, energy, pulse width, and repetition rate of the nanosecond pulsed laser to ensure the quality and safety of the photoacoustic signal.

[0021] Specifically, in the guided excitation module 2, the connecting device 2.2 connects the positioning device 2.3 and the excitation device 2.1 to form a whole; the positioning device 2.3 is a metal component connected to the target tissue to be removed, and it has a biocompatible coating; the excitation device 2.1 is implemented using the same type of optical fiber as in the pulsed laser module 1, and is connected to the first multimode optical fiber 1.3 in the pulsed laser module 1 through an optical fiber connector; the excitation device 2.1 can be implemented in the following two ways, such as... Figure 2 As shown: Option 1: The excitation device consists of a second multimode fiber 2.1.2. (For example...) Figure 2As shown in Figure (1), the diameter of the second multimode fiber 2.1.2 used is smaller than that of the puncture needle sheath. The tail of the second multimode fiber 2.1.2 is connected to the tail of the positioning device 2.3 through the connecting device 2.2. After puncturing the target tissue, it remains in the tissue together with the positioning device 2.3. The head of the second multimode fiber 2.1.2 is equipped with an optical fiber connector 2.1.1. The patient does not need to be connected to the pulse laser module 1 at all times while waiting for the operation, which facilitates patient movement and instrument disinfection. The tail of the positioning device 2.3 is coated with a biocompatible metal material with high photoacoustic effect. During the operation, the nanosecond pulse laser generated by the pulse laser module 1 excites the positioning device 2.3 inside the target tissue to generate a photoacoustic signal. Then, through subsequent photoacoustic signal acquisition and processing, the position information of the positioning device 2.3 is obtained, thereby obtaining the position information of the target tissue.

[0022] Option 2: The excitation device is implemented using a second multimode optical fiber 2.1.2 and a transparent guide tube 2.1.3. For example... Figure 2 As shown in Figure (2), the outer diameter of the transparent catheter 2.1.3 is smaller than the inner diameter of the puncture needle sheath. One end of the transparent catheter 2.1.3 is connected to the tail of the positioning device 2.3 via the connecting device 2.2. The diameter of the second multimode optical fiber 2.1.2 is smaller than the inner diameter of the transparent catheter 2.1.3. It is placed inside the transparent catheter 2.1.3 and connected to the transparent catheter 2.1.3. The head of the second multimode optical fiber 2.1.2 is equipped with an optical fiber connector 2.1.1. The patient does not need to be constantly connected to the pulsed laser module 1 while waiting for surgery, which facilitates patient movement and instrument disinfection. The tail of the second multimode optical fiber 2.1.2 is connected to the tail of the transparent catheter 2.1.3. A very small gap is left between the ends, in which a chromophore 2.1.4 with high absorption rate is placed and integrally connected to the positioning device 2.3 via the connecting device 2.2. During surgery, the nanosecond pulsed laser generated by the pulsed laser module 1 excites the chromophore 2.1.4 inside the target tissue to generate a photoacoustic signal. Subsequent photoacoustic signal acquisition and processing yields the positional information of the chromophore 2.1.4, thus obtaining the positional information of the target tissue. Unlike the above scheme, in this scheme, the tail end of the positioning device 2.3 is not coated with a biocompatible metal material with high photoacoustic effect; instead, the photoacoustic signal is generated by the chromophore 2.1.4. Specifically, the signal receiving module 3 also includes a preamplifier 3.2 and a data acquisition card 3.3; the ultrasonic transducer 3.1 uses a handheld miniature area array probe; one of the corner array elements is defined as a reference point, and the positioning results output by the subsequent display module are all represented as the spatial position of the tissue under test relative to this reference point; during operation, the nanosecond pulsed laser excites the target tissue to generate a photoacoustic signal, and the ultrasonic transducer 3.1 receives the photoacoustic signal on the surface of the target tissue and converts it into an electrical signal; since the amplitude of the original electrical signal is weak, the preamplifier 3.2 amplifies it with low noise and performs bandpass filtering and impedance matching to improve the signal amplitude and signal-to-noise ratio, and reduce noise and distortion during transmission; the data acquisition card 3.3 is synchronously connected to the pulsed laser 1.1; when the data acquisition card 3.3 receives a trigger signal from the pulsed laser 1.1, it immediately performs a synchronous sampling, performs analog-to-digital conversion on the analog electrical signal output by the preamplifier 3.2, converts the continuous signal into an original digital signal, and transmits it to the data processing module 4 in real time.

[0023] In one specific embodiment, the ultrasonic transducer 3.1 adopts a 5×5 array of array elements with a center-to-center spacing of 1mm, covering a range of 4mm×4mm, and all array elements are arranged coplanarly on a plane of Z=-40mm.

[0024] Specifically, in data processing module 4, a high-frequency filter is used to achieve frequency domain filtering. The preset matching signal is generated by the matching filter and demodulated by Hilbert transform to obtain the envelope signal. The skewness threshold is used as a screening index for statistical distribution characteristics. The sampling time corresponding to the maximum value of the effective envelope signal is taken and multiplied by the sampling interval to obtain the arrival time of the sound wave of each receiving unit of the ultrasonic transducer.

[0025] In one specific embodiment, a high-frequency filter, such as a fourth-order Butterworth high-pass filter, is used to perform high-frequency filtering on the photoacoustic signal to obtain a high-frequency digital signal.

[0026] In one specific embodiment, a matched filter is pre-constructed, whose impulse response is consistent with the bipolar pulse shape of the aforementioned photoacoustic signal; the correlation operation adopts convolution calculation. Therefore, when performing correlation calculation between the high-frequency digital signal and the preset matched feature signal, the high-frequency digital signal obtained after filtering is convolved with the matched filter, so that the real signal has obvious peaks, while the noise is effectively smoothed, thereby significantly improving the signal-to-noise ratio. This step is the key to accurately extracting the arrival time of the sound wave.

[0027] In one specific embodiment, to obtain a stable time reference point from the output of the matched filter, a Hilbert transform is performed on the convolution result to obtain the envelope signal; the envelope signal reflects the time-domain distribution of the signal energy, and its peak position corresponds to the most likely time when the sound wave arrives at the receiving unit; the calculation results of the above process are as follows: Figure 5 As shown.

[0028] In one specific embodiment, the skewness threshold is used as a screening index for statistical distribution characteristics. First, the skewness coefficient of the envelope signal is calculated, which reflects the asymmetry of the waveform. For signals with high signal-to-noise ratio, the envelope usually exhibits a sharp single-peak shape with a large skewness; conversely, the skewness is small. This invention only retains those channels with a skewness greater than the skewness threshold as valid channels, and the remaining channels are considered invalid and discarded.

[0029] In a specific embodiment, when calculating the three-dimensional spatial location of the target tissue based on the multi-point localization algorithm, a nonlinear least squares objective function is first constructed. This objective function is to calculate the Euclidean distance between the location of the sound source to be determined and the array element, the product of the arrival time of the array element and the speed of sound, for each array element corresponding to the effective channel. The residual is calculated using the difference between the Euclidean distance and the product. The sum of the squared residuals of all effective array elements is accumulated as the nonlinear least squares objective function. This invention uses the Levenberg-Marquardt algorithm for solving the problem. This algorithm combines the advantages of gradient descent and Newton's method, which can guarantee global convergence and converge quickly when close to the optimal solution.

[0030] Specifically, the control module 6 is responsible for the overall synchronous control and management of the system, including the nanosecond pulse laser triggering timing, signal acquisition startup, data processing process, and image display. The control module can also adjust the nanosecond pulse laser frequency, acquisition gain, and reconstruction algorithm parameters as needed to adapt to different surgical scenarios and tissue characteristics. In addition, the control unit can set the working mode and parameters through the human-machine interface to realize the intelligent and integrated operation of the system.

[0031] This invention also proposes a precise positioning and guidance device for deep lesions based on photoacoustic imaging, the device comprising: Pulsed laser equipment used to generate nanosecond pulsed lasers; The guiding excitation device, connected to the pulsed laser device, includes an excitation device, a connection device, and a positioning device connected in sequence; the nanosecond pulsed laser generates a photoacoustic signal by exciting a photoacoustic signal source located in the target tissue, the photoacoustic signal source being either the positioning device or a chromophore with a high absorption rate; The signal receiving device receives photoacoustic signals from the surface of the target tissue through an ultrasonic transducer, processes them to obtain raw digital signals, and then transmits them to the data processing device. The data processing device performs frequency domain filtering on the original digital signal to extract high-frequency digital signals; performs correlation operations on the high-frequency digital signals and demodulates them with a preset matching signal to obtain an envelope signal; filters effective envelope signals based on the statistical distribution characteristics of the envelope signals; calculates the arrival time of sound waves of each receiving unit of the ultrasonic transducer based on the time feature points of the effective envelope signals; and executes a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue based on the position and arrival time of each receiving unit.

[0032] The deep lesion tissue precise positioning and guidance device proposed in this invention also includes: Display devices are used to visualize three-dimensional spatial positions; Control equipment is used to synchronously control and manage the entire system.

[0033] Figure 3 The diagram illustrates the usage process of this system. In a specific embodiment, taking the removal of a pulmonary nodule as an example, the specific implementation process of the system is described, and the workflow is as follows: Figure 4 As shown, where Figure 1 and Figure 2 The functions implemented by each module and the data acquisition and processing flow are as follows: The first step is the implantation of the preoperative guidance and stimulation module. Under CT guidance, the positioning device is percutaneously implanted into the area adjacent to the pulmonary nodule. Simultaneously, the first multimode fiber connected to the positioning device is fixed in the puncture path via a transparent catheter, while the second multimode fiber retains a fiber optic connector at its tip for easy connection to the pulsed laser module during the procedure. Two options are available for the positioning device implantation: option one is to use a positioning device with a high photoacoustic effect metal material coated at the tail end, and option two is to use a chromophore with a high absorption rate that is integrally connected to the positioning device via a connecting device. Both techniques can achieve photoacoustic excitation in the pulmonary nodule area during the subsequent procedure. After implantation, the puncture needle sheath is withdrawn, leaving only the positioning device and the second multimode fiber in the lung tissue.

[0034] The second step is intraoperative system connection and parameter setting. After the patient enters the operating room, the pulsed laser module is connected to the guided excitation module. The parameters of the pulsed laser are set as follows: wavelength is 800 nm, single pulse energy is 1–3 mJ, pulse width is 8–10 ns, and repetition frequency is 10 Hz. The control module completes the synchronization timing configuration between the pulsed laser, data acquisition card, display module and ultrasonic transducer.

[0035] Step 3: Photoacoustic excitation of the lung nodule area The system is activated when the suspected resection area is determined; the nanosecond pulsed laser is shaped by the coupling lens group and enters the first multimode fiber and the second multimode fiber, and is transmitted to the positioning device near the lung nodule. If a positioning device with a high photoacoustic effect metal material coated at the tail end is used, the high photoacoustic effect metal material absorbs the pulsed laser energy and expands instantaneously with thermoelasticity, generating a high signal-to-noise ratio photoacoustic signal inside the lung tissue; if a chromophore with a high absorption rate is used and is integrally connected to the positioning device through a connecting device, the high absorption rate chromophore absorbs light energy and generates a photoacoustic signal.

[0036] The fourth step is the reception of body surface signals and three-dimensional spatial positioning. Medical staff attach the ultrasound transducer to the corresponding area on the lung surface; the signal receiving module simultaneously receives photoacoustic signals from the area adjacent to the lung nodule, which are amplified by the preamplifier and then converted into raw digital signals by the data acquisition card at high speed, and transmitted to the data processing module in real time; the data processing module processes the raw digital signals and uses a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue.

[0037] Step 5: Precise intraoperative resection guidance The display module shows the three-dimensional position coordinates of the lung nodule relative to the reference point of the ultrasound transducer in real time. Based on the displayed coordinates, the doctor adjusts the direction of the resection instruments and the cutting margin under thoracoscopy to perform wedge resection. Since the system can refresh the positioning results in real time, it can still continuously provide updates to the spatial coordinates of the nodule during the respiratory movement and traction deformation of the lung tissue, thereby significantly reducing the offset error in the traditional static positioning method.

[0038] Step 6: Complete the removal and exit the system. After completing the lung nodule resection, turn off the pulsed laser module, remove the guidance and excitation module, and turn off the data acquisition and display module.

[0039] This invention uses the k-Wave three-dimensional finite-difference time-domain (FDTD) acoustic simulation platform to construct a simulation system, acquire multi-channel photoacoustic signals, and perform three-dimensional reconstruction based on a multi-point localization algorithm of sound wave arrival time to obtain localization results. Finally, the localization results are quantitatively verified.

[0040] The simulation system uses a uniform Cartesian mesh with dimensions of 200×200×500 and a spatial step of 0.2mm, covering a physical space of 40mm×40mm×100mm (±20mm for each of the X / Y axes, and -50mm to +50mm for the Z axis). Soft tissue acoustic parameters are used throughout the medium, with a background sound velocity set to 1520m / s and a density set to 1000kg / m³. 3To simulate tissue sound velocity inhomogeneity, a random perturbation of ±20 m / s was superimposed. Simultaneously, 30 microbubbles with radii of 0.2–2 mm and a sound velocity of 500 m / s were randomly implanted throughout the space as scattering interference sources. The photoacoustic source was defined as a point source, with its geometric center located at coordinates (10 mm, 10 mm, 32.6 mm) (relative to the plane of the ultrasonic transducer array). The ultrasonic transducer adopted a 5×5 lattice element planar array with an element center spacing of 1 mm, covering a range of 4 mm × 4 mm. All elements were arranged coplanarly on the Z = -40 mm plane. The linear acoustic wave equation was solved using the finite-difference time-domain method in the k-Wave toolbox, and the perfect-matched layer absorbed boundary reflections to record the time-domain signals of all elements.

[0041] Figure 6 The localization results of the multi-point localization algorithm based on the time of arrival of sound waves are shown. The estimated location is at (9.90mm, 10.04mm, 32.63mm), with a localization error of 0.109mm from the true center (10mm, 10mm, 32.6mm), verifying the sub-millimeter level localization capability under the system configuration. The reconstruction process is completed within a few seconds, demonstrating the real-time performance of the system. This method can be flexibly extended to different array layouts and media parameters, providing reliable numerical basis and theoretical support for the hardware design, algorithm optimization, and clinical application of photoacoustic imaging systems.

[0042] It should be noted that the specific parameters given in this invention (such as grid step size, sound velocity, number and spacing of array elements, filter order and cutoff frequency, template waveform of matched filter, skewness threshold, optimization algorithm type and iteration tolerance, etc.) are all preferred examples and do not constitute a limitation on the scope of protection. Those skilled in the art can flexibly adjust the above parameters and function forms according to actual application scenarios (such as different imaging depths, different frequency responses, and different noise levels). For example, a Chebyshev or elliptic filter can be used instead of a high-pass filter, the template of the matched filter can be reconstructed based on the measured impulse response, and other algorithms such as the simplex method, quasi-Newton method, or particle swarm optimization can be used for optimization. The initial iteration value can also be roughly estimated based on the first arriving channel. Any equivalent substitution or adjustment based on the same principle is an equivalent substitution of this invention and should be considered to fall within the scope of protection of this invention.

[0043] In the embodiments provided by this invention, it should be understood that the disclosed apparatus / terminal devices and methods can be implemented in other ways. For example, the apparatus / terminal device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0044] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A precise localization and guidance system for deep lesions based on photoacoustic imaging, characterized in that, The system includes: Pulsed laser module (1), used to generate nanosecond pulsed laser; The guiding excitation module (2) is connected to the pulsed laser module (1) and includes an excitation device (2.1), a connection device (2.2), and a positioning device (2.3) connected in sequence. The nanosecond pulsed laser generates a photoacoustic signal by exciting a photoacoustic signal source located in the target tissue. The photoacoustic signal source is either the positioning device (2.3) or a chromophore with a high absorption rate (2.1.4). The signal receiving module (3) receives the photoacoustic signal from the surface of the target tissue through the ultrasonic transducer (3.1), processes it to obtain the original digital signal, and then transmits it to the data processing module (4). The data processing module (4) performs frequency domain filtering on the original digital signal to extract high-frequency digital signals; performs correlation operations on the high-frequency digital signals and preset matching signals and demodulates them through Hilbert transform to obtain envelope signals; filters effective envelope signals according to the statistical distribution characteristics of the envelope signals; calculates the arrival time of sound waves of each receiving unit of the ultrasonic transducer (3.1) according to the time feature points of the effective envelope signals; and executes a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue according to the position of each receiving unit and the arrival time of sound waves. Specifically, the skewness threshold is used as a screening index for statistical distribution characteristics; the sampling time corresponding to the maximum value of the effective envelope signal is taken and multiplied by the sampling interval to obtain the sound wave arrival time of each receiving unit of the ultrasonic transducer.

2. The deep lesion tissue precise positioning guidance system according to claim 1, characterized in that, The system also includes a display module (5) for visualizing the three-dimensional spatial position.

3. The deep lesion tissue precise positioning guidance system according to claim 1, characterized in that, The system also includes a control module (6) for synchronous control and management of the entire system.

4. The deep lesion tissue precise positioning guidance system according to claim 1, characterized in that, The excitation device (2.1) consists of a second multimode fiber (2.1.2), and the tail of the second multimode fiber (2.1.2) is connected to the tail of the positioning device (2.3) through a connecting device (2.2).

5. The deep lesion tissue precise positioning guidance system according to claim 1, characterized in that, The excitation device (2.1) is realized by a second multimode optical fiber (2.1.2) and a transparent conduit (2.1.3). The transparent conduit (2.1.3) is made of a biocompatible material, and one end of the transparent conduit (2.1.3) is connected to the tail of the positioning device (2.3) through a connecting device (2.2).

6. The deep lesion tissue precise positioning guidance system according to claim 5, characterized in that, A gap is left between the tail end of the second multimode optical fiber (2.1.2) and the tail end of the transparent conduit (2.1.3), in which a chromophore (2.1.4) with high absorption rate is placed and integrated with the positioning device (2.3) via the connecting device (2.2).

7. The deep lesion tissue precise positioning guidance system according to claim 1, characterized in that, In the data processing module (4), a high-frequency filter is used to implement frequency domain filtering, and the preset matching signal is generated by the matching filter.

8. A device for precise localization and guidance of deep lesions based on photoacoustic imaging, characterized in that, The device includes: Pulsed laser equipment used to generate nanosecond pulsed lasers; The guiding excitation device, connected to the pulsed laser device, includes an excitation device, a connection device, and a positioning device connected in sequence; the nanosecond pulsed laser generates a photoacoustic signal by exciting a photoacoustic signal source located in the target tissue, the photoacoustic signal source being either the positioning device or a chromophore with a high absorption rate; The signal receiving device receives photoacoustic signals from the surface of the target tissue through an ultrasonic transducer, processes them to obtain raw digital signals, and then transmits them to the data processing device. The data processing device performs frequency domain filtering on the original digital signal to extract high-frequency digital signals; performs correlation operations on the high-frequency digital signals and a preset matching signal, and demodulates them using Hilbert transform to obtain an envelope signal; filters effective envelope signals based on the statistical distribution characteristics of the envelope signals; calculates the arrival time of sound waves in each receiving unit of the ultrasonic transducer based on the time feature points of the effective envelope signals; and executes a multi-point positioning algorithm to calculate the three-dimensional spatial position of the target tissue based on the position and arrival time of each receiving unit. Specifically, the skewness threshold is used as a screening index for statistical distribution characteristics; the sampling time corresponding to the maximum value of the effective envelope signal is taken and multiplied by the sampling interval to obtain the sound wave arrival time of each receiving unit of the ultrasonic transducer.

9. The precise positioning and guiding device for deep lesions according to claim 8, characterized in that, In the data processing device, a high-frequency filter is used to achieve frequency domain filtering, and the preset matching signal is generated by the matching filter.

Images