A dual line simultaneous scanning excitation fluorescence diffuse tomography system

Abstract

This application discloses a dual-line simultaneous scanning excitation fluorescence diffusion tomography (FDT) system, relating to the fields of optics and biomedical engineering. The system includes: a rotating stage for placing and rotating a sample; a laser scanning module for emitting dual-line excitation light to scan and excite the sample, causing fluorescent targets within the sample to fluoresce; and a detection module for detecting the dual-line excitation light and fluorescence, and performing inverse image reconstruction based on the dual-line excitation light and fluorescence to generate a three-dimensional image of the fluorescent targets inside the sample. This application can further improve the overall reconstruction quality of FDT imaging while maintaining a high imaging rate.

Description

Technical Field

[0001] This application relates to the fields of optical and biomedical engineering, and in particular to a fluorescence diffusion tomography system for simultaneous dual-line scanning excitation. Background Technology

[0002] Fluorescence diffusion tomography (FDT), also known as fluorescence molecular tomography (FMT), is a macroscopic optical imaging technique used in the biomedical field. FDT uses near-infrared excitation light to sequentially illuminate the surface of biological tissue from multiple angles. The excitation light diffuses through the tissue, exciting fluorescent targets within the tissue that are specifically labeled with molecular probes, resulting in fluorescence signals. These signals are then collected by an optical signal detection device, obtaining the diffused excitation light and fluorescence signals that reach the tissue surface. Based on a light transport model and corresponding reconstruction algorithms, three-dimensional reconstruction of fluorescent targets within the biological body can be achieved. This technology can locate and quantify fluorescent probes in small animals or specific human organs, featuring a large imaging range, deep imaging depth, low cost, and no radiation. It is currently widely used in early cancer diagnosis, drug development, brain functional imaging, and gene therapy.

[0003] In recent years, due to its unique advantages, FDT (Fluorescence Diffusion Tomography) technology has begun to be applied in dynamic imaging fields with extremely high real-time requirements, such as surgical navigation and pharmacokinetics studies. However, traditional FDT technology relies on a point source scanning excitation mode, which results in a slow imaging rate, severely hindering its further expansion and application in dynamic imaging. To overcome this problem, a full-angle line-scan excitation fluorescence diffusion tomography method and system has been proposed. This system uses a line source instead of a point source for scanning excitation and is accompanied by corresponding forward process modeling and system calibration techniques, aiming to significantly improve FDT imaging speed without sacrificing reconstruction accuracy. Experimental data from phantom bodies strongly confirm that the line-scan FDT system not only significantly shortens the imaging data acquisition cycle but also improves reconstruction quality to a certain extent.

[0004] Nevertheless, both the traditional point scan excitation mode and the previously proposed single-line scan excitation mode face a common problem: after excitation at many angles, the fluorescence signal intensity received by the opposite detection surface is weak. The weaker fluorescence signal is more susceptible to noise interference or even completely masked, which severely restricts the reconstruction quality of FDT. Moreover, the difference in fluorescence signal intensity is not significant with the change of excitation angle, which also severely restricts the reconstruction quality of FDT. Summary of the Invention

[0005] The purpose of this application is to provide a fluorescence diffusion tomography system with dual-line simultaneous scanning excitation, which can improve the overall reconstruction quality of FDT imaging.

[0006] To achieve the above objectives, this application provides the following solution.

[0007] This application provides a dual-line simultaneous scanning excited fluorescence diffusion tomography system, including the following devices.

[0008] A rotating stage is used to place the sample and rotate the sample.

[0009] The laser scanning module is used to emit dual-line excitation light to scan and excite the sample, causing the fluorescent targets in the sample to fluoresce.

[0010] The detection module is used to detect the double-line excitation light and the fluorescence, and to perform inverse image reconstruction based on the double-line excitation light and the fluorescence to generate a three-dimensional image of the fluorescent target inside the sample.

[0011] Optionally, the laser scanning module includes the following devices.

[0012] Near-infrared lasers are used to emit near-infrared excitation beams.

[0013] A first lens is disposed in the output optical path of the near-infrared laser to focus the near-infrared excitation beam.

[0014] A small aperture is set in the transmission light path of the first lens to filter the focused near-infrared excitation beam.

[0015] The second lens is disposed in the outgoing light path of the small hole and is used to parallelize the filtered near-infrared excitation beam.

[0016] An aperture stop is placed in the transmission light path of the second lens to limit the diameter of the near-infrared excitation beam after parallel processing.

[0017] A beam shaper, disposed in the output optical path of the aperture, is used to convert the near-infrared excitation beam with limited diameter from a Gaussian beam into a uniform flat-top beam.

[0018] A beam splitter is disposed in the output optical path of the beam shaper to split a uniform flat-top beam into two beams, namely a first beam and a second beam.

[0019] The first optical path is set on the output optical path of the beam splitter to adjust the direction of the first beam and focus the adjusted first beam on the surface of the sample.

[0020] The second optical path is set on the output optical path of the beam splitter to adjust the direction of the second beam and focus the adjusted second beam on the surface of the sample; the adjusted first beam and the adjusted second beam constitute a bilinear excitation beam.

[0021] Optionally, the first conversion optical path includes the following devices.

[0022] A first cylindrical lens is disposed in the output optical path of the beam splitter to focus the first beam in the horizontal direction to form a first line beam.

[0023] The first reflecting mirror is disposed in the transmission light path of the first cylindrical lens and is used to reflect the first line beam.

[0024] The first biaxial galvanometer is disposed in the reflected light path of the first reflector and is used to change the direction of the first reflected line beam to generate the first beam after adjustment.

[0025] The first flat-field scanning lens is disposed in the output light path of the first biaxial galvanometer and is used to focus the first beam after it has been oriented.

[0026] Optionally, the second conversion optical path includes the following devices.

[0027] A second reflector is disposed in the output optical path of the beam splitter to reflect the second beam.

[0028] The second cylindrical lens is placed in the reflected light path of the second reflector to focus the reflected second beam in the horizontal direction to form a second linear beam.

[0029] The second biaxial galvanometer is positioned in the transmission path of the second cylindrical lens to change the direction of the second line beam and generate a second beam after directional adjustment.

[0030] The second flat-field scanning lens is disposed in the output light path of the second biaxial galvanometer and is used to focus the second beam after it has been oriented.

[0031] Optionally, the angle between the first beam and the second beam after adjustment is 0 degrees to 180 degrees, and the intersection of the first beam and the second beam after adjustment is located on the rotation axis of the rotating platform.

[0032] Optionally, the angle between the first beam and the second beam after reorientation is 90 degrees, and the intersection of the first beam and the second beam after reorientation is located on the rotation axis of the rotating platform.

[0033] Optionally, the laser scanning module further includes a shutter, disposed in the transmission light path of the second lens, for controlling the opening and closing of the transmission light path.

[0034] Optionally, the detection module includes: a filter group, a camera lens, an electron multiplier charge-coupled device (ECC), and a computer; the filter group, the camera lens, and the ECC are arranged sequentially.

[0035] The bilinear excitation light or the fluorescence is filtered out by the filter group, and the filtered light beam is focused by the camera lens onto the electron multiplication charge-coupled device, which then detects the focused light beam.

[0036] The computer is connected to the electron multiplication charge-coupled device; the computer is used to receive and store detection data, and to perform reverse image reconstruction based on the detection data to generate a three-dimensional image of the fluorescent target inside the sample; the detection data includes: bilinear excitation light and fluorescence.

[0037] The computer is also connected to the near-infrared laser and is used to control the near-infrared laser to emit a near-infrared excitation beam.

[0038] The computer is also connected to the first biaxial mirror and the second biaxial mirror respectively, for controlling the operating voltage of the first biaxial mirror and the second biaxial mirror, and changing the beam angle according to the operating voltage.

[0039] The computer is also connected to the rotating platform and is used to control the rotating platform to rotate.

[0040] Optionally, the filter group includes the following devices.

[0041] A fluorescent filter, mounted on a rotating disk, is used to filter out the bilinear excitation light and allow the fluorescence to pass through.

[0042] An excitation light filter is disposed on the rotating disk to filter out the fluorescence and allow the bilinear excitation light to pass through.

[0043] The turntable is used to adjust the positions of the fluorescence filter and the excitation filter.

[0044] Optionally, the fluorescent filter, the excitation filter, and the rotating disk may be one or more.

[0045] According to the specific embodiments provided in this application, this application has the following technical effects.

[0046] This application provides a fluorescence diffusion tomography system with dual-line simultaneous scanning excitation. By rotating the sample through a rotating stage, the laser scanning module scans and excites the dual-line excitation light emitted by the sample from multiple angles. This causes the fluorescent targets in the sample to produce fluorescence signals with higher intensity that vary significantly with the excitation angle, thereby providing better data support for subsequent FDT image reconstruction. Finally, the detection module receives the dual-line excitation light and fluorescence from multiple angles to reconstruct a three-dimensional image of the fluorescent targets inside the sample, thus improving the overall reconstruction quality of the final FDT imaging. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a dual-line simultaneous scanning excited fluorescence diffusion tomography system provided in an embodiment of this application.

[0049] Figure 2 This is a schematic diagram of a three-dimensional image and a slice image of a heterogeneous cylinder simulation model provided in an embodiment of this application; wherein, (a) is a three-dimensional image of the heterogeneous cylinder simulation model, and (b) is a slice image of the heterogeneous cylinder simulation model.

[0050] Figure 3 The following are schematic cross-sectional views of single-line and double-line excitation modes provided in an embodiment of this application; wherein, (a) is a schematic cross-sectional view of the single-line excitation mode and (b) is a schematic cross-sectional view of the double-line excitation mode.

[0051] Figure 4 This is a line graph illustrating the maximum fluorescence intensity of a dual fluorophore as a function of the excitation angle under single-line excitation and excitation with a 90° angle between the two lines, according to an embodiment of this application.

[0052] Figure 5 This is a schematic diagram of the image reconstruction results of a dual fluorophore under single-line and dual-line (90° angle) scanning excitation modes according to an embodiment of this application; wherein, (a) is a three-dimensional distribution map of the real fluorophore, (b) is a slice of the intermediate layer of the real fluorophore, (c) is a three-dimensional distribution map of the fluorophore reconstructed by single-line excitation, (d) is a slice of the intermediate layer of the fluorophore reconstructed by single-line excitation, (e) is a three-dimensional distribution map of the fluorophore reconstructed by dual-line excitation, and (f) is a slice of the intermediate layer of the fluorophore reconstructed by dual-line excitation.

[0053] Reference numerals: 1-Near-infrared laser; 2-First lens; 3-Pinhole; 4-Second lens; 5-Shutter; 6-Aperture; 7-Beam shaper; 8-Beam splitter; 9-First cylindrical lens; 10-First reflecting mirror; 11-First biaxial galvanometer; 12-First flat-field scanning lens; 13-Second reflecting mirror; 14-Second cylindrical lens; 15-Second biaxial galvanometer; 16-Second flat-field scanning lens; 17-Rotating stage; 18-Filter group; 19-Camera lens; 20-Electron multiplier charge-coupled device; 21-Computer. Detailed Implementation

[0054] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0055] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] In one exemplary embodiment, such as Figure 1 As shown, a fluorescence diffusion tomography system for simultaneous dual-line scanning excitation is provided, including: a rotating stage 17, a laser scanning module, and a detection module.

[0057] The rotating stage 17 is used to place the sample and rotate the sample.

[0058] The laser scanning module is used to emit dual-line excitation light to scan and excite the sample, causing the fluorescent targets in the sample to fluoresce.

[0059] The detection module is used to detect the double-line excitation light and fluorescence, and to perform inverse image reconstruction based on the double-line excitation light and fluorescence to generate a three-dimensional image of the fluorescent target inside the sample.

[0060] Specifically, such as Figure 1 As shown, the laser scanning module includes: a near-infrared laser 1, a first lens 2, a pinhole 3, a second lens 4, an aperture 6, a beam shaper 7, a beam splitter 8, a first conversion optical path, and a second conversion optical path.

[0061] Near-infrared laser 1 is used to emit a near-infrared excitation beam. A 750nm semiconductor laser multimode is used as the light source because near-infrared light scatters and absorbs less in tissues compared to visible light, which is beneficial for improving FDT imaging quality. First lens 2 is positioned in the output optical path of near-infrared laser 1 to focus the near-infrared excitation beam, facilitating pinhole filtering and subsequent collimation. Pinhole 3 is positioned in the transmission optical path of first lens 2 to filter the focused near-infrared excitation beam, achieving multimode laser filtering. Second lens 4 is positioned in the output optical path of pinhole 3 to parallelize the filtered near-infrared excitation beam, converting the focused laser into parallel light. Aperture 6 is positioned in the transmission optical path of second lens 4 to limit the parallelized beam. The beam consists of: a diameter of the near-infrared excitation beam; a beam shaper 7, disposed on the output optical path of the aperture 6, used to convert the Gaussian beam in the near-infrared excitation beam with limited diameter into a uniform flat-top beam; a beam splitter 8, disposed on the output optical path of the beam shaper 7, used to split the uniform flat-top beam into two beams, namely a first beam and a second beam, with the first beam and the second beam having equivalent intensities; a first conversion optical path, disposed on the output optical path of the beam splitter, used to adjust the direction of the first beam and focus the adjusted first beam onto the surface of the sample; a second conversion optical path, disposed on the output optical path of the beam splitter, used to adjust the direction of the second beam and focus the adjusted second beam onto the surface of the sample; the adjusted first beam and the adjusted second beam constitute a bilinear excitation beam.

[0062] Specifically, the first conversion optical path includes: a first cylindrical lens 9, a first reflecting mirror 10, a first biaxial galvanometer 11, and a first flat-field scanning lens 12.

[0063] The first cylindrical lens 9 is disposed in the output optical path of the beam splitter 8 and is used to gradually focus the first beam in the horizontal direction to form a first line beam; the first reflecting mirror 10 is disposed in the transmission optical path of the first cylindrical lens 9 and is used to reflect the first line beam; the first biaxial galvanometer 11 is disposed in the reflection optical path of the first reflecting mirror 10 and is used to change the direction of the reflected first line beam to generate the first beam after adjustment, thereby realizing two-dimensional scanning; the first flat-field scanning lens 12 is disposed in the output optical path of the first biaxial galvanometer 11 and is used to focus the first beam after adjustment, so that the first beam after adjustment is focused on the sample surface.

[0064] Specifically, the second conversion optical path includes: a second reflecting mirror 13, a second cylindrical lens 14, a second biaxial galvanometer 15, and a second flat-field scanning lens 16.

[0065] The second reflecting mirror 13 is disposed in the output light path of the beam splitter 8 and is used to reflect the second beam. The second cylindrical lens 14 is disposed in the reflection light path of the second reflecting mirror 13 and is used to gradually focus the second beam in the horizontal direction to form a second line beam. The second biaxial galvanometer 15 is disposed in the transmission light path of the second cylindrical lens 14 and is used to change the direction of the reflected second line beam to generate a second beam after directional adjustment, thereby realizing two-dimensional scanning. The second flat-field scanning lens 16 is disposed in the output light path of the second biaxial galvanometer 15 and is used to focus the second beam after directional adjustment, so that the second beam after directional adjustment is focused on the sample surface.

[0066] As an optional implementation, the laser scanning module also includes a shutter 5; the shutter 5 is disposed on the transmission light path of the second lens 4 and is used to control the opening and closing of the transmission light path.

[0067] Specifically, the angle between the first beam and the second beam after adjustment is 0 degrees to 180 degrees, and the intersection of the first beam and the second beam after adjustment is located on the rotation axis of the rotating stage 17.

[0068] Specifically, the angle between the first and second beams after reorientation is 90 degrees, and the intersection of the first and second beams after reorientation is located on the rotation axis of the rotating stage 17. For example... Figure 1 As shown, by adjusting the placement of the optical components, the first beam after adjustment, the second beam after adjustment, and the rotation axis of the rotating stage can form a certain angle. Figure 1 The diagram shows a dual-line scanning FDT system with a 90° angle between the two lines.

[0069] Specifically, the detection module includes: a filter group 18, a camera lens 19, an electron multiplier charge-coupled device 20, and a computer 21; the filter group 18, the camera lens 19, and the electron multiplier charge-coupled device 20 are arranged in sequence; the computer 21 is connected to the electron multiplier charge-coupled device 20.

[0070] The dual-line excitation light or fluorescence is filtered out by the filter group 18, and the filtered light beam is focused by the camera lens 19 onto the electron multiplication charge-coupled device 20. The electron multiplication charge-coupled device 20 detects the focused light beam. The computer 21 is used to receive and store the detection data, and to perform reverse image reconstruction based on the detection data to generate a three-dimensional image of the fluorescent target inside the sample. The detection data includes: dual-line excitation light and fluorescence. The computer 21 is also connected to the near-infrared laser 1 to control the near-infrared laser 1 to emit near-infrared laser light. The camera lens 19 is used to collect the light beam and converge it to the electron multiplier charge-coupled device 20. The converged light beam detected by the electron multiplier charge-coupled device 20 is either bilinear excitation light or fluorescence. The computer 21 is also connected to the shutter and is used to control the opening and closing of the shutter. The computer 21 is also connected to the rotating stage 17 and is used to control the rotation of the rotating stage 17. The computer 21 is also connected to the first biaxial galvanometer 11 and the second biaxial galvanometer 15 respectively and is used to control the operating voltage of the first biaxial galvanometer 11 and the second biaxial galvanometer 15, and change the beam angle according to the operating voltage to realize the change of beam angle.

[0071] Specifically, the filter group 18 includes: a fluorescence filter, an excitation filter, and a rotating disk.

[0072] A fluorescence filter, mounted on a rotating disk, filters out the bilinear excitation light while allowing fluorescence to pass through. An excitation light filter, also mounted on the rotating disk, filters out the fluorescence while allowing bilinear excitation light to pass through. The two filters are placed at different positions on the rotating disk. When detecting different wavelengths, the appropriate filter (fluorescence filter or excitation light filter) needs to be adjusted to be in front of the lens using the rotating disk.

[0073] Specifically, there are one or more fluorescent filters, excitation filters, and rotating disks.

[0074] In a specific embodiment, the specific imaging steps of the fluorescence diffusion tomography system excited by the above-mentioned dual-line simultaneous scanning are as follows.

[0075] A sample containing a fluorescent target is placed on a rotating stage. The near-infrared laser 1 and shutter 5 are turned on. The near-infrared light is focused by the first lens 2, filtered by the pinhole 3, and then formed into a parallel beam by the second lens 4. It then passes sequentially through the shutter 5, aperture 6, and beam shaper 7 to become collimated and uniformly parallel light. Next, the beam is split into two beams of equal intensity by the beam splitter 8. The first beam is focused horizontally by a cylindrical lens, reflected by a mirror, and enters a dual-axis galvanometer. After the scanning direction is adjusted by the dual-axis galvanometer, it passes through a flat-field scanning lens to form a linear first beam focused on the sample surface. The second beam, after passing through a mirror and then focused horizontally by a cylindrical lens, is also focused horizontally by the dual-axis galvanometer and then through a flat-field scanning lens to form a linear second beam focused on the sample surface. By controlling the rotation of the rotating stage 17, scanning of the sample at different angles is achieved.

[0076] After the two excitation beams strike the surface of the sample tissue, they diffuse within it. Upon reaching the fluorescent target, they excite fluorophores to produce fluorescence. The fluorescence, like the excitation light, then diffuses within the tissue before reaching the surface and being detected by the EMCCD. When using the EMCCD to detect fluorescence, a fluorescence filter is first placed in front of the lens to filter out the excitation light, and then the beam is focused onto the EMCCD through the camera lens 19. The operation for detecting excitation light using the EMCCD is similar; simply place an excitation light filter in front of the lens to filter out the fluorescence, and then focus the beam onto the EMCCD through the camera lens 19.

[0077] Finally, by combining the dual-line scanning FDT forward model, the excitation light and fluorescence data obtained from the detection are used to perform inverse image reconstruction, thereby realizing dual-line scanning fluorescence diffusion tomography and finally obtaining a three-dimensional image of the fluorescent target inside the sample.

[0078] For the forward modeling process in dual-line scanning FDT image reconstruction, the field intensity distribution of the excitation band from the dual-line source can be considered as the superposition of the field intensity distributions of the excitation bands from two single-line sources. For a single-line source, it can be modeled as a whole composed of multiple point sources. Therefore, the field intensity distribution of the excitation band diffused by the dual-line source can be considered as a weighted superposition of the field intensity distributions of the excitation band diffused by multiple point sources. By applying the normalized Born approximation to the processed field intensity distributions of the excitation and fluorescence bands, the forward system matrix A of the dual-line scanning FDT can be obtained. The forward model of the dual-line scanning FDT system is further obtained as follows.

[0079] .

[0080] in, This represents the ratio of fluorescence detection data to excitation light detection data. This represents the three-dimensional distribution of fluorescent targets within the sample under test. Using the above formula, combined with the excitation light and fluorescence data obtained from the detection, dual-line scanning FDT image reconstruction can be performed.

[0081] To verify the image reconstruction quality improvement effect of the proposed dual-line scanning FDT method and system, a heterogeneous cylinder simulation experiment was designed. The heterogeneous cylinder simulation model is as follows: Figure 2 As shown, there are multiple regions inside, representing different organizational structures. The optical parameters for different organizational structures are shown in Table 1.

[0082] Table 1 Optical parameters of various structures in the simulation model of the heterogeneous cylinder.

[0083]

[0084] This application sets up simulation experiments of FDT image reconstruction under single-line and dual-line scanning excitation modes. Figure 3 In the figure, (a) and (b) represent cross-sectional schematic diagrams of single-line excitation and double-line excitation of dual fluorophores, respectively. In the simulation experiment, the power of each single-line light source was set to be the same; the size of the fluorophore was set to 2 mm in length, 2 mm in width, and 6 mm in height; and the angle between the double line and the rotation axis was set to 90°.

[0085] First, the effects of single-line and dual-line scanning excitation modes on the intensity of the detected fluorescence signal were investigated. In the experiment, each line light source was set to 10 mm in length and was uniformly divided into 20 point light sources. The detector was selected from all side surface nodes within 150° of the light source on the opposite side. Figure 4 This diagram illustrates the variation of the maximum fluorescence intensity detected on the opposite detection surface with excitation angle after single-line and double-line excitation when two fluorophores are present in the model. Solid lines represent double-line excitation at a 90° angle, and dashed lines represent single-line excitation. Figure 4 It can be seen that the fluorescence signal intensity detected by single-line excitation is relatively weak, and the intensity difference with the excitation angle is not obvious. This makes FDT reconstruction very sensitive to noise, limiting the image reconstruction quality. In contrast, for the dual-line simultaneous excitation mode, the detected fluorescence signal intensity is significantly enhanced, and the intensity difference with the excitation angle is also more obvious.

[0086] Next, FDT simulations and reconstructions were performed under single-line and dual-line scanning excitation modes. Each line source in the experiment was also set to a length of 10 mm and was uniformly divided into 20 point sources. The detector selection range included all sample surface nodes within the z-axis range [-12, 12] within 150° of the light source on the opposite side, and half of these nodes were selected as detectors using a staggered selection method. The reconstruction regularization method employed was Iteratively reweighted L1 regularization (IRL1), and the split Bregman algorithm was chosen as the optimization method. The specific parameter settings for the simulation reconstruction experiment are shown in Table 2.

[0087] Table 2 Simulation Reconstruction Experiment Parameter Settings

[0088]

[0089] Table 3 shows the quantitative indicators of simulated reconstruction for dual fluorophores under two scanning excitation modes. Here, RMSE represents the root mean square error, CNR represents the contrast signal-to-noise ratio, Dice is the similarity metric coefficient, and LE represents the localization error. The smaller the RMSE and LE, and the larger the CNR and Dice, the better the FDT image reconstruction quality. Figure 5 These are the image reconstruction results of dual fluorophores under single-line and dual-line (90° angle) scanning excitation modes. Figure 5 Images (a) and (b) show the three-dimensional distribution of the actual fluorophores and a slice of the intermediate layer. Figure 5 Images (c) and (d) show the three-dimensional distribution map and intermediate layer slice of the fluorophore reconstructed by single-line excitation. Figure 5 (e) and (f) in the figure are the three-dimensional distribution map and the intermediate layer slice map of the fluorophore reconstructed by double-line excitation.

[0090] Table 3. Quantitative indices of simulated reconstruction of dual fluorophores under single-line and dual-line excitation scanning modes.

[0091]

[0092] As can be seen from the results in Table 3, when the angle between the two lines is 90°, the image reconstruction performance of the dual-line simultaneous excitation scanning mode is significantly improved compared to the single-line excitation FDT mode. Figure 5It can be seen that the reconstructed image from single-line scanning FDT has many artifacts and struggles to reconstruct the square cross-sectional morphology of the fluorophore. In contrast, the reconstructed image from dual-line scanning FDT with a 90° angle between the two lines has fewer artifacts and reconstructs the cross-sectional morphology of the fluorophore very well. Simulation experiments verify that the dual-line scanning FDT system can further improve the FDT image reconstruction quality while maintaining the high imaging rate of the line scanning excitation mode. It should be noted that different imaging samples and different fluorophore distributions may correspond to different optimal dual-line excitation angles, making it impossible to satisfy the optimal excitation mode for all situations. Therefore, when building a dual-line scanning FDT system, a relatively moderate dual-line angle, such as 90°, can be selected.

[0093] To address the limitations of weak detection fluorescence intensity and insignificant variation with excitation angle in previously proposed single-line scanning FDT systems, which restricts image reconstruction quality, this application further improves the excitation mode and innovatively proposes a dual-line scanning FDT system. This system can further enhance FDT image reconstruction quality while retaining the high imaging rate of the line scanning excitation mode. This application offers the following advantages.

[0094] The dual-line scanning FDT system proposed in this application simultaneously excites the sample under test using two light sources at a certain angle to the rotation axis each time, and detects the excitation light signal and fluorescence signal diffused to the sample surface on the opposite side. The sample under test is rotated by a rotating stage, thus achieving full-angle scanning excitation and detection, after which FDT imaging data is acquired and can be used for subsequent FDT image reconstruction. This dual-line scanning FDT system can further enhance the intensity of the detected fluorescence signal and the degree of difference with the excitation angle while retaining the high imaging rate of the line scanning excitation mode. Combined with a corresponding dual-line FDT forward process modeling method, this dual-line simultaneous scanning excitation fluorescence diffusion tomography system can significantly improve the image reconstruction quality.

[0095] A forward modeling method for dual-line scanning FDT image reconstruction is proposed, which models the field intensity distribution of the excitation light band of the dual-line source as the superposition of the field intensity distributions of the excitation light bands of two single-line sources. Since a single line source can be discretized into multiple point sources, the field intensity distribution of the excitation light band diffused by each line source in the tissue can be considered as a weighted sum of the field intensity distributions of the excitation light bands of the point sources. This method can accurately describe the diffusion motion of the dual-line source within the sample, ensuring the accuracy of both forward modeling and inverse reconstruction.

[0096] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A fluorescence diffusion tomography system for simultaneous dual-line scanning excitation, characterized in that, The dual-line simultaneous scanning excitation fluorescence diffusion tomography system uses a dual-line light source at a certain angle to the rotation axis to simultaneously excite the sample under test in each excitation. The dual-line simultaneous scanning excitation fluorescence diffusion tomography system includes: A rotating stage is used to place the sample and rotate the sample. A laser scanning module is used to emit dual-line excitation light to scan and excite the sample, causing the fluorescent targets in the sample to fluoresce. The laser scanning module includes: Near-infrared lasers are used to emit near-infrared excitation beams. A first lens is disposed in the output optical path of the near-infrared laser to focus the near-infrared excitation beam; A small hole is set in the transmission light path of the first lens to filter the focused near-infrared excitation beam; The second lens is disposed in the outgoing light path of the small hole and is used to parallelize the filtered near-infrared excitation beam. An aperture stop is set in the transmission light path of the second lens to limit the diameter of the near-infrared excitation beam after parallel processing. A beam shaper is disposed in the output optical path of the aperture to convert the near-infrared excitation beam with limited diameter from a Gaussian beam into a uniform flat-top beam. A beam splitter is disposed in the output optical path of the beam shaper to split the uniform flat-top beam into two beams, namely a first beam and a second beam; the intensity of the first beam and the second beam are equivalent. The first conversion optical path is set on the output optical path of the beam splitter, and is used to adjust the direction of the first beam and focus the adjusted first beam on the surface of the sample. The second conversion optical path is set in the output optical path of the beam splitter, and is used to adjust the direction of the second beam and focus the adjusted second beam on the surface of the sample; the adjusted first beam and the adjusted second beam constitute a bilinear excitation beam; The detection module is used to detect the double-line excitation light and the fluorescence, and to perform inverse image reconstruction based on the double-line excitation light and the fluorescence to generate a three-dimensional image of the fluorescent target inside the sample.

2. The fluorescence diffusion tomography system with dual-line simultaneous scanning excitation according to claim 1, characterized in that, The first conversion optical path includes: A first cylindrical lens is disposed in the output optical path of the beam splitter to focus the first beam in the horizontal direction to form a first line beam; The first reflecting mirror is disposed in the transmission light path of the first cylindrical lens and is used to reflect the first line beam. The first biaxial galvanometer is disposed in the reflected light path of the first reflector and is used to change the direction of the first line beam after reflection to generate the first beam after adjustment. The first flat-field scanning lens is disposed in the output light path of the first biaxial galvanometer and is used to focus the first beam after it has been oriented.

3. The fluorescence diffusion tomography system with dual-line simultaneous scanning excitation according to claim 2, characterized in that, The second conversion optical path includes: A second reflector is disposed in the output optical path of the beam splitter to reflect the second beam. The second cylindrical lens is set in the reflected light path of the second reflector to focus the reflected second beam in the horizontal direction to form a second line beam; The second biaxial galvanometer is set in the transmission light path of the second cylindrical lens and is used to change the direction of the second line beam to generate the second beam after adjustment. The second flat-field scanning lens is disposed in the output light path of the second biaxial galvanometer and is used to focus the second beam after it has been oriented.

4. The fluorescence diffusion tomography system with dual-line simultaneous scanning excitation according to claim 3, characterized in that, The angle between the first beam and the second beam after adjustment is 90 degrees, and the intersection of the first beam and the second beam after adjustment is located on the rotation axis of the rotating platform.

5. The fluorescence diffusion tomography system excited by dual-line simultaneous scanning according to claim 1, characterized in that, The laser scanning module further includes a shutter, which is disposed in the transmission light path of the second lens and is used to control the opening and closing of the transmission light path.

6. The fluorescence diffusion tomography system with dual-line simultaneous scanning excitation according to claim 3, characterized in that, The detection module includes: a filter group, a camera lens, an electron multiplier charge-coupled device (ECC), and a computer; the filter group, the camera lens, and the ECCC are arranged sequentially. The bilinear excitation light or the fluorescence is filtered out by the filter group, and the filtered light beam is focused by the camera lens onto the electron multiplier charge-coupled device, which then detects the focused light beam. The computer is connected to the electron multiplication charge-coupled device; the computer is used to receive and store detection data, and to perform reverse image reconstruction based on the detection data to generate a three-dimensional image of the fluorescent target inside the sample; the detection data includes: bilinear excitation light and fluorescence; The computer is also connected to the near-infrared laser and is used to control the near-infrared laser to emit a near-infrared excitation beam; The computer is also connected to the first biaxial mirror and the second biaxial mirror respectively, for controlling the operating voltage of the first biaxial mirror and the second biaxial mirror, and changing the beam angle according to the operating voltage; The computer is also connected to the rotating platform and is used to control the rotating platform to rotate.

7. The fluorescence diffusion tomography system excited by dual-line simultaneous scanning according to claim 6, characterized in that, The filter group includes: A fluorescent filter, mounted on a rotating disk, is used to filter out the bilinear excitation light and allow the fluorescence to pass through. An excitation light filter is disposed on the rotating disk to filter out the fluorescence and allow the bilinear excitation light to pass through; The turntable is used to adjust the positions of the fluorescence filter and the excitation filter.

8. The fluorescence diffusion tomography system with dual-line simultaneous scanning excitation according to claim 7, characterized in that, The fluorescent filter, the excitation filter, and the turntable may be one or more.

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