Non-collimation single photon tomography method and system

Abstract

The invention relates to the technical field of radiation detection imaging, and discloses a non-collimation single photon tomography method and system. The system is based on a non-collimation single photon tomography system and comprises scintillation media of at least two layers of latticed structures, the scintillation media of the upper and lower layers of latticed structures have preset displacement in the left-right direction, and a preset distance is formed between the scintillation media of each layer of latticed structure; the scintillation medium of each layer of latticed structure is formed by long-strip-shaped scintillation media in an orthogonal distribution mode; photons to be measured penetrate through the scintillation medium of the latticed structure and interact once or multiple times; and determining an imaging processing method according to the occurrence frequency of the interaction and the energy deposited in the scintillation medium to obtain a single photon cross-sectional image. According to the invention, the collimation of photons is realized through the dislocation of the latticed structure, and the restriction of a mechanical collimator is overcome; and image reconstruction in two modes is combined, so that the system is suitable for detection of photons with different energy.

Description

Technical Field

[0001] The present invention relates to the field of radiation detection imaging technology, and in particular to a non-collimated single-photon tomography method and system. Background Art

[0002] Radiopharmaceuticals are radionuclide preparations or their labeled drugs used in nuclear medicine for clinical diagnosis and treatment. In clinical practice, radiopharmaceuticals will be enriched in the target tumor tissue area, and diagnosis and treatment will be carried out through the decay of the medical radionuclides mounted on them. Therefore, imaging analysis of the distribution of radionuclides is of great significance for clinical diagnosis and treatment.

[0003] At present, the radionuclide imaging devices commonly used in clinical practice mainly include single photon emission tomography (SPECT) equipment and positron emission tomography (PET) equipment. Among them, traditional SPECT detects and images the gamma rays produced by the decay of radionuclides, but is limited by the mechanical collimator and is only suitable for the detection of low-energy rays; while PET detects and images a pair of annihilation photons with an energy of 511keV produced by the decay of radionuclides by time coincidence. Therefore, the energy range that can be detected by the currently commonly used radionuclide imaging equipment is limited, and it is impossible to image multiple nuclides at the same time.

[0004] Therefore, there is an urgent need for a non-collimated single-photon tomography method and system that can increase the photon measurement range. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a non-collimated single-photon tomography method, which is implemented based on a non-collimated single-photon tomography system; the imaging system includes at least two layers of scintillating media with a grid structure, and the upper and lower layers of scintillating media with a grid structure are arranged with a preset displacement in the left and right directions, and a preset spacing is provided between each layer of scintillating media with a grid structure; each layer of scintillating media with a grid structure is composed of long strips of scintillating media in an orthogonal distribution manner; The photons to be measured pass through the scintillation medium of the grid structure and interact with each other, and the number of interactions of the photons to be measured in the scintillation medium and the energy deposited in the scintillation medium are obtained. The imaging processing method is determined according to the number of interactions and the energy deposited in the scintillation medium to obtain a single photon tomographic image: If only one interaction occurs, and the interaction is a photoelectric effect, and the energy deposited in the scintillation medium is within a preset energy range threshold, a low-photon energy imaging processing method is used to obtain a single-photon tomographic image; If multiple interactions occur, and the order of the interactions is at least one Compton scattering and then one photoelectric effect, and the energy deposited by the photon in the scintillation medium after all interactions is greater than the preset energy range threshold, a high-photon energy imaging processing method is used to obtain a single-photon tomographic image.

[0006] Preferably, the low photon energy imaging processing method is: The number of interactions that occurred, the energy deposited in the scintillation medium, and the location where the interaction occurred were recorded; After pixelating the detector space, the count of the photons that interact with each other corresponding to each pixel in the detector space is determined according to the location where the interaction occurs; A single photon tomographic image is obtained by using a reconstruction algorithm according to the count of interacting photons corresponding to each pixel and the energy deposited in the scintillation medium.

[0007] Preferably, the high photon energy imaging processing method is: The number of interactions that occurred, the energy deposited in the scintillation medium, and the location where the interaction occurred were recorded; After pixelating the imaging space, the cone surface corresponding to the Compton scattering event is obtained according to the energy deposited in the scintillation medium and the location where the interaction occurs, and it is determined whether each pixel in the imaging space is located on the cone surface; At each imaging space pixel located on the cone surface, all eligible Compton events are traversed to obtain the initial reconstructed image and system matrix; A single photon tomographic image is obtained by a reconstruction algorithm according to the initial reconstructed image and the system matrix.

[0008] Another aspect of the present invention provides a non-collimated single-photon tomography system, which implements any of the non-collimated single-photon tomography methods described above, wherein the imaging system specifically comprises a detection module and a data processing module; the detection module comprises a scintillation medium array (1), a signal conversion unit (2) and a signal amplification unit (3); the data processing module comprises a signal transmission unit (4), a data acquisition unit (5) and an image reconstruction unit (6); The scintillation medium array (1) is composed of at least two layers of scintillation medium in the grid-like structure; The scintillation medium array (1) is used to interact with the photons to be measured to generate optical signals; the optical signals are converted into electrical signals by a signal conversion unit (2), amplified by a signal amplification unit (3), and then transmitted by a signal transmission unit (4) and collected by a data collection unit (5), and data processing is performed by an image reconstruction unit (6) to obtain the distribution of the photons to be measured in an imaging space.

[0009] Preferably, the scintillation medium is a scintillation optical fiber or a long strip scintillator.

[0010] Preferably, the light yield of the scintillating medium is greater than 30,000 ph / MeV.

[0011] Preferably, the decay time of the scintillation medium is less than 40 μs.

[0012] Preferably, the scintillating medium is a cerium-doped yttrium-lutetium silicate crystal, or a cerium-doped gadolinium-gallium-aluminum crystal, or a cerium-doped lutetium-aluminum garnet crystal.

[0013] Preferably, the relative angle between the imaging system and the object to which the photon to be measured belongs is rotated.

[0014] Preferably, the surface of the scintillation medium is coated with a reflective material.

[0015] The embodiments of the present invention have the following technical effects: The present application is based on a non-collimated single-photon tomography system, comprising at least two layers of scintillating media in a grid structure, wherein the upper and lower layers of scintillating media in a grid structure have a preset displacement in the left-right direction, and a preset spacing is provided between each layer of scintillating media in a grid structure; each layer of scintillating media in a grid structure is composed of long strips of scintillating media in an orthogonal distribution manner; the photons to be measured pass through the scintillating media in the grid structure, and the photons to be measured pass through the scintillating media in the grid structure, and interact with each other to obtain the distribution of the photons to be measured in the scintillating media; and then, according to the detection situation, the distribution of the photons to be measured in the imaging space is obtained through a reconstruction algorithm method. The system overcomes the constraints of the mechanical collimator, is suitable for the detection of photons of different energies, and combines the two modes of image reconstruction, so that the system is suitable for the detection of photons of different energies. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 is a structural schematic diagram of a non-collimated single-photon tomography system provided by an embodiment of the present invention; Figure 2 is a schematic diagram of a grid structure of a scintillation medium array (1) of a non-collimated single photon tomography system provided by an embodiment of the present invention; Figure 3 is a schematic diagram of a non-collimated structure of a non-collimated single-photon tomography system provided by an embodiment of the present invention; Figure 4 is a schematic diagram of the concept of non-collimation of a non-collimation single photon tomography system provided by an embodiment of the present invention; Figure 5 It is a schematic diagram of a flow chart of an imaging processing method selection process of a non-collimated single photon tomography imaging method provided by an embodiment of the present invention; Figure 6 is a schematic diagram of multi-angle detection of a non-collimated single-photon tomography system provided by an embodiment of the present invention; Figure 7 It is a schematic diagram of the process flow of the low photon energy imaging processing method provided by an embodiment of the present invention; Figure 8 It is a schematic flow chart of a high photon energy imaging processing method provided by an embodiment of the present invention; Fig. 9 It is a schematic diagram of location information provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0019] When detecting radionuclides that emit a single gamma photon, the currently commonly used radionuclide imaging equipment has a limited detectable energy range and cannot image multiple nuclides at the same time. For example, traditional SPECT requires the use of a mechanical collimator. Currently commonly used collimators are usually made of tungsten or lead. These materials block low-energy rays better than high-energy rays. If you want to use them for high-energy ray detection, you need to increase the thickness of the collimator, which will greatly reduce the detection efficiency. In addition, it is also related to the detectors used in traditional SPECT. Sodium iodide (NaI(Tl)) detectors are usually used. The density of NaI is (3.67 g / cm³), which has a poor blocking effect on high-energy rays, resulting in a significant decrease in the detection efficiency of high-energy rays.

[0020] In order to solve the above technical problems, the present invention provides a non-collimated single-photon tomography method, which is implemented based on a non-collimated single-photon tomography system; the imaging system includes at least two layers of scintillating media with a grid structure, and the upper and lower layers of scintillating media with a grid structure are arranged with a preset displacement in the left and right directions, and a preset spacing is provided between each layer of scintillating media with a grid structure; each layer of scintillating media with a grid structure is composed of long strips of scintillating media in an orthogonal distribution manner; The photons to be measured pass through the scintillation medium of the grid structure and interact with each other, and the number of interactions of the photons to be measured in the scintillation medium and the energy deposited in the scintillation medium are obtained. The imaging processing method is determined according to the number of interactions and the energy deposited in the scintillation medium to obtain a single photon tomographic image: If only one interaction occurs, and the interaction is a photoelectric effect, and the energy deposited in the scintillation medium is within a preset energy range threshold, a low-photon energy imaging processing method is used to obtain a single-photon tomographic image; In some embodiments, the low photon energy imaging processing method is: The number of interactions that occurred, the energy deposited in the scintillation medium, and the location where the interaction occurred were recorded; After pixelating the detector space, the count of the photons that interact with each other corresponding to each pixel in the detector space is determined according to the location where the interaction occurs; A single photon tomographic image is obtained by using a reconstruction algorithm according to the count of interacting photons corresponding to each pixel and the energy deposited in the scintillation medium.

[0021] Exemplarily, single photon emission tomography (SPECT) is used as a low-photon energy imaging processing method.

[0022] If multiple interactions occur, and the order of the interactions is at least one Compton scattering and then one photoelectric effect, and the energy deposited by the photon in the scintillation medium after all interactions is greater than the preset energy range threshold, a high-photon energy imaging processing method is used to obtain a single-photon tomographic image.

[0023] In some embodiments, the high photon energy imaging processing method is: The number of interactions that occurred, the energy deposited in the scintillation medium, and the location where the interaction occurred were recorded; After pixelating the imaging space, a cone surface corresponding to the Compton scattering event is obtained according to the energy deposited in the scintillation medium and the location where the interaction occurs, and it is determined whether each pixel in the imaging space is located on the cone surface; On each detector spatial pixel located on the cone surface, all valid Compton events are traversed to obtain the initial reconstructed image and system matrix; A single photon tomographic image is obtained by a reconstruction algorithm according to the initial reconstructed image and the system matrix.

[0024] Exemplarily, Compton imaging is used as a high photon energy imaging processing method.

[0025] Exemplarily, the reconstruction algorithm of the low / high photon energy imaging processing method during reconstruction all uses the same algorithm, including but not limited to: direct back projection method, iterative algorithm, artificial intelligence, etc., which are all existing mature technologies and will not be repeated here.

[0026] Exemplarily, the photons to be detected may be radioactive nuclides or prompt gamma rays generated by the interaction between protons / neutrons and other rays and matter.

[0027] Figure 5 FIG. 1 is a schematic diagram of a flow chart of an imaging processing method selection process of a non-collimated single photon tomography imaging method provided by an embodiment of the present invention, comprising Figure 5 It can be seen that the main steps of realizing wide energy range X-ray imaging in this application are: the detector detects the incident photons, and if the energy of the incident photons is within the preset low-energy photon energy range, the uncollimated SPECT mode is used to process the detection data and form an image; if the energy of the incident photons is within the preset high-energy photon energy range, the Compton imaging mode is used to process the detection data and form an image.

[0028] If the incident photon generates only one photoelectric effect in the detector, the first response position and the first energy deposition of the photon in the detector are recorded, and it is determined whether the deposition energy is within the preset energy range threshold. If it is within the energy range, the corresponding position and energy data are stored in the non-collimated SPECT imaging data set; the above imaging data set is statistically analyzed to obtain the photon counts at different positions in the detector, and a reconstruction algorithm is used to reconstruct a three-dimensional image. The preset energy range threshold can be set according to the processing capacity range of SPECT.

[0029] Exemplarily, an iterative algorithm can be used to achieve image reconstruction, and the core process of the iterative method includes: initializing the reconstructed image, estimating and calculating the predicted value of each detection unit based on the current image, obtaining the correction factor by comparing the actual measurement value of the detection unit with the predicted value, and back-projecting the correction factor to the imaging space to calculate the cumulative correction amount of each pixel, and then updating the pixel value of the imaging space; repeating the above process until convergence, and finally outputting the reconstructed image. Therefore, the input parameters required for the reconstruction process include: the initialized reconstructed image, the measurement data of the detector, the system matrix, the pixel size and the number of iterations, and the output result is the reconstructed image after the iteration is completed. The main difference between the iterative reconstruction of non-collimated SPECT and the iterative reconstruction of traditional SPECT lies in the measurement data of the detector. Due to the blocking effect of the mechanical collimator on photons, the traditional SPECT can only use the data collected by the part of the detector that is not blocked by the collimator; and the detection data used in the present invention is the full data set of all detection units, which does not need to be limited by the physical blocking of the mechanical collimator, thereby significantly improving the data utilization and reconstruction accuracy.

[0030] Exemplarily, the low photon energy imaging processing method process is as follows Figure 7 As shown, first, the detector space and the imaging space are pixelated, and the acquired data is processed to obtain the photon count corresponding to each pixel; then the system matrix is ​​calculated, where the system matrix represents the probability that each pixel in the imaging space is detected by each pixel in the detector space; finally, an iterative algorithm is used, and after a certain number of iterations, the value corresponding to each pixel in the imaging space is obtained, and then the distribution of the radiation source in the imaging space is obtained.

[0031] If the incident photon first undergoes one or more Compton scatterings in the detector and then a photoelectric effect occurs, the position and energy deposition of the photon in the detector where Compton scattering and photoelectric effect occur are recorded, and it is determined that the sum of the energy deposition is higher than the preset energy range threshold. If higher, the positions and energies of the above multiple responses are stored in the Compton imaging data set; the above imaging data set is screened to obtain valid Compton events, and a reconstruction algorithm is used to reconstruct a three-dimensional image. Combining the above two image reconstruction methods, an uncollimated single-photon tomography result containing low-energy and high-energy ray distributions can be obtained.

[0032] Among them, the imaging data set is screened based on the position and deposition energy of Compton scattering and the position and deposition energy of photoelectric effect recorded in a Compton event (that is, a photon undergoes one or more Compton effects in the scintillation medium and then undergoes a photoelectric effect). The cosine value of the Compton scattering angle calculated is between -1 and 1. If so, the Compton event is considered valid, otherwise the event is eliminated.

[0033] Exemplary high photon energy imaging processing methods are as follows Figure 8 As shown, the imaging space is first pixelated, and then the cone surface corresponding to a Compton event in the data set is obtained, and each pixel in the imaging space is traversed to determine whether each pixel is located on the cone surface; then all Compton events in the data set are traversed to obtain the initial reconstructed image and system matrix; finally, an iterative algorithm is used to obtain the value of each pixel in the imaging space after a certain number of iterations, and then the distribution of the radiation source in the imaging space is obtained.

[0034] Another aspect of the present invention provides a non-collimated single-photon tomography system for implementing the non-collimated single-photon tomography method described in one of the above items. The imaging system specifically comprises a detection module and a data processing module; the detection module comprises a scintillation medium array (1), a signal conversion unit (2) and a signal amplification unit (3); the data processing module comprises a signal transmission unit (4), a data acquisition unit (5) and an image reconstruction unit (6). Figure 1 As shown; illustratively, the signal conversion unit (2) may be a photomultiplier tube array.

[0035] The collimation of photons is mainly achieved by using a scintillating medium array (1), see Figure 4 , relying on the staggered arrangement of adjacent upper and lower grid structures, the photons can be collimated; and all the detection data detected by the grid structure can also be used in subsequent imaging processes.

[0036] Figure 3 Schematic diagram of the non-collimation structure of the non-collimation single photon tomography system provided by an embodiment of the present invention, comprising a radiation source ( Figure 3 The photons emitted by 11) enter the detector composed of scintillation array medium ( Figure 3 12 of them), occurs once ( Figure 3 13) or multiple times ( Figure 3 According to the number of interactions and the amount of energy deposited in the scintillation medium, the corresponding data processing method is selected and combined with the reconstruction algorithm to finally obtain the distribution of radionuclides in the imaging space.

[0037] The scintillation medium array (1) is used to generate a photoelectric effect with the photons to be measured to generate an optical signal; the optical signal is converted into an electrical signal by a signal conversion unit (2), amplified by a signal amplification unit (3), and then transmitted by a signal transmission unit (4) and collected by a data collection unit (5), and data processing is performed by an image reconstruction unit (6) to obtain the distribution of the photons to be measured in an imaging space.

[0038] Exemplarily, the signal conversion unit (2) may be a photomultiplier tube, the signal amplification unit (3) may be a channel compression and operational amplifier board, the signal transmission unit (4) may be an adapter board, and the data acquisition unit (5) may be a data acquisition card. Photons are incident on the scintillation medium array (1) and interact with it; then the generated optical signal is detected by the signal conversion unit (2) and the optical signal is converted into an electrical signal, which is amplified by the signal amplification unit (3) to facilitate subsequent recording and processing of the signal. The amplified signal transmission unit (4) is transmitted to the back-end data acquisition unit (5); then the data acquisition unit (5) digitizes the transmitted signal to generate data required for image reconstruction (including the position, energy and time information of the ray), and transmits the data to the image reconstruction unit (6). Finally, image reconstruction is achieved based on the acquired data and combined with relevant reconstruction algorithms (such as direct back projection, iteration, artificial intelligence, etc.).

[0039] The scintillation medium array (1) is composed of at least two layers of scintillation medium in the grid-like structure; For example, Figure 2As shown, the scintillation medium array part in the above detection module includes: staggered long strips of scintillation medium, the staggered arrangement is that the upper and lower layers of the grid structure have a certain displacement in the left and right directions, the above grid structure is composed of two layers of long strips of scintillation medium in an orthogonal distribution, each layer is arranged with scintillation medium and air intervals; each layer of the grid structure can be separated by air, or scintillation medium with very different densities can be arranged to form a grid structure. That is, N scintillation media are arranged without gaps as a group, M groups of scintillation media are arranged side by side, and two layers of scintillation media arranged side by side are orthogonally distributed vertically and horizontally to form a grid structure, such as Figure 2 As shown; a certain number of layers of the grid structure are arranged, and the next layer of grid structure has a certain spacing d and a fixed sequential displacement x relative to the previous layer of grid structure, such as Figure 3 As shown, the photons are collimated by relying on this misalignment, overcoming the restriction of the mechanical collimator on the photon measurement range. Among them, the number of layers of the grid structure, the spacing d between the grid structures, and the misalignment displacement x are mainly determined according to the required position resolution of the equipment and the imaging energy range. If only low-energy rays are detected, fewer layers of grid structures are required; if high-energy rays need to be detected or the energy range span is relatively large, from low energy to high energy, more layers of grid structures are required. This is because low-energy rays have relatively low energy and poor penetration. If a large number of grid structures are still used, it is not necessary; for high-energy rays, due to their relatively high energy and large penetration, if you want to have good detection efficiency, you need to set up a multi-layer grid structure.

[0040] The smaller the displacement x, the better the position resolution, but more layers of scintillating media are required. The number of scintillating media in each layer of the mesh structure is determined according to the required detection efficiency. The more the number, the higher the detection efficiency. In one embodiment, 5 scintillators of 1mm×1mm×100mm are closely arranged as a group, and 10 groups are arranged in each layer. The scintillators of the next layer are closely connected with the scintillators of the previous layer, and are orthogonally distributed to form a mesh structure; the spacing between the upper and lower layers of the mesh structure is 10mm, and the displacement is 1mm.

[0041] In some embodiments, the scintillation medium is a scintillation optical fiber or a long strip scintillator. The surface of the scintillation medium is coated with an enhanced mirror reflection film. The function of the reflection film is to improve the light collection efficiency, reduce the light loss in the scintillation medium, enhance the light output intensity, and improve the energy resolution and spatial resolution; in addition, it can also prevent optical crosstalk between adjacent scintillation media. The enhanced mirror reflection film is a high-performance reflection material, usually composed of multiple layers of materials, and has a higher reflectivity and better reflection performance than ordinary reflection films. The enhanced mirror reflection film is only one of the materials coated on the surface of the scintillation medium, and can also be Teflon, metal reflection film such as aluminum, polyester film, etc.

[0042] In some embodiments, the light yield of the scintillation medium is 30000ph / MeV-40000ph / MeV. If the light yield is too small, the brightness of the scintillation light after the reaction will be poor, affecting the monitoring of the reaction position and the determination of the energy.

[0043] In some embodiments, the decay time of the scintillation medium is 20 μs-40 μs. If the screening time is too long, the reaction time of the scintillation medium will be long and the real-time performance will be poor.

[0044] In some embodiments, the scintillating medium is a cerium-doped yttrium lutetium silicate crystal, or a cerium-doped gadolinium gallium aluminum crystal, or a cerium-doped lutetium aluminum garnet crystal. The structure includes but is not limited to scintillating optical fiber (round, square), a long strip scintillator with a reflector, etc. The material includes but is not limited to cerium-doped yttrium lutetium silicate crystal (LYSO:Ce), cerium-doped gadolinium gallium aluminum crystal (GAGG:Ce) or cerium-doped lutetium aluminum garnet crystal (LuAG:Ce), etc. The size includes but is not limited to 1mm×1mm×100mm, 0.8mm×0.8mm×100mm, 0.5mm×0.5mm×100mm. The scintillation medium with a grid structure plays a dual role of light collimation and reaction. The density of the material must be compatible with the monitoring needs of high-energy and low-energy photons. The greater the density of the material, the stronger the light absorption. However, if the density is too large, it will block and shield the photons, reduce the intake of photons, and is not conducive to the monitoring of low-energy photons. If the density of the material is too small, the blocking effect is poor, which is not conducive to the detection of high-energy photons.

[0045] The photons to be measured can be radioactive nuclides or prompt gamma rays generated by the interaction between protons / neutrons and other rays and matter.

[0046] Exemplarily, the photomultiplier tube in the detection module is coupled with a photodetector at both ends of each scintillation medium, and the position information and energy information of the incident photon in the scintillation medium are obtained by reading the optical signals at both ends. For the same scintillation medium, the energy is different, the light intensity generated in the scintillation medium is different, and the strength of the electrical signal converted from the optical signal is different. The energy information is represented by the obtained electrical signal strength.

[0047] For the above-mentioned double-ended coupled photodetector device, deep position discrimination (DOI) is required. This application uses double-ended readout to measure and correct the depth information of the interaction event, so as to obtain the specific location information of the photon reaction (including three coordinates of x, y, and z). Double-ended readout refers to the connection of photodetectors at both ends of the long strip or columnar scintillation fiber array. When the incident photon enters the scintillation fiber, an interaction will occur to generate scintillation photons, which will then be captured by the photodetectors at both ends of the crystal. Double-ended readout measures the signal intensity received by the photodetectors at both ends to infer the location of the photon interaction in the crystal. Photon interactions at different depths will cause changes in the propagation mode of the scintillation light. The ratio of the signal amplitude (i.e., light intensity) at both ends of the crystal can reflect the location of the photon interaction. Specifically, the detector closer to the interaction location will receive a stronger signal.

[0048] Among them, the depth information is the z coordinate where the corresponding photon reacts in the scintillation medium, because for the scintillation medium array in the figure ( Fig. 9 A in Figure 1), when obtaining the position information of photon interactions, the x and y coordinates are generally represented by pixels, that is, by the double-ended photomultiplier tube array ( Fig. 9 B and C) indicates that the z coordinate ( Fig. 9 The D in the figure is usually considered to be at the center of the scintillating medium array, but the actual z coordinate is not always at the center of the scintillating medium array. Therefore, it is necessary to further obtain the z coordinate, that is, the depth information.

[0049] Furthermore, in order to determine the depth information of the reaction of the ray in the scintillation fiber, the present application performs summation processing on the signals received by the photodetectors at both ends of the scintillation fiber, and compares the signal at one end with the sum of the signals at both ends, thereby deriving the specific depth position of the photon interaction. Specifically, the signal intensity is usually reflected in the form of energy value in the recorded data. Therefore, the sum of the signals at both ends of the scintillation fiber can be expressed as the sum of the energies received by the photodetectors at both ends. By calculating the ratio of the energy of the left or right end signal to the sum of the energies at both ends, the depth information of the ray interaction can be effectively obtained. Because when the position of the interaction is different, the signals obtained at both ends are also different, then the ratio of the signal at one end to the signals at both ends will also change, so that the relationship between the position and the ratio can be obtained, and then the depth information can be obtained based on this relationship. Therefore, the ratio provides depth information about the position of the interaction of photons in the scintillation fiber, which helps to achieve accurate depth position discrimination (DOI).

[0050] In some embodiments, the relative angle between the imaging system and the object to which the photons to be measured belong is rotated.

[0051] Exemplarily, by rotating the relative angle between the imaging system and the object to which the photon to be detected belongs, detection at multiple angles can be achieved, such as Figure 6 As shown, the rotation center is the space where the object to be measured is located. By rotating a single detection module, the imaging effect can be further improved.

[0052] The present invention uses a detector as a collimator, which realizes photon collimation and photon detection at the same time. Compared with the traditional SPECT using a mechanical collimator, the detection efficiency of the overall structure is greatly improved. In addition, by combining the non-collimated SPECT imaging method and the Compton imaging method, imaging of rays in a wide energy range is achieved, wherein the non-collimated SPECT method is suitable for low-energy ray imaging, and the Compton imaging method is suitable for high-energy ray imaging. In addition, a scintillation medium is used as a detector, and the small size and overall structural design of the scintillation medium are utilized to achieve high spatial resolution imaging. Compared with the existing radionuclide imaging technology, the present invention has two advantages: (1) the non-collimated SPECT imaging method and the Compton imaging method are combined to broaden the imaging energy range, thereby realizing simultaneous imaging of multiple radionuclides; (2) the detection efficiency and spatial resolution are improved, and accurate imaging of radionuclides is realized. The improvement of detection efficiency is reflected in: because the present invention does not use a mechanical collimator, it will not have a blocking effect on photons; in addition, all detection data of the entire detector can be used in subsequent image reconstruction; so the detection efficiency can be improved. The improvement in spatial resolution is reflected in the fact that using small-sized long strips of scintillation media or scintillation optical fibers can obtain more accurate position information, which helps to obtain more accurate reconstructed images.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A non-collimated single photon tomography method, characterized in that: It is realized based on an uncollimated single photon tomography imaging system; the imaging system comprises at least two layers of scintillating media in a grid structure, wherein the upper and lower layers of scintillating media in a grid structure have a preset displacement in the left and right directions, and a preset spacing is provided between each layer of scintillating media in a grid structure; each layer of scintillating media in a grid structure is composed of long strips of scintillating media in an orthogonal distribution manner; The photons to be measured pass through the scintillation medium of the grid structure and interact with each other, and the number of interactions of the photons to be measured in the scintillation medium and the energy deposited in the scintillation medium are obtained. The imaging processing method is determined according to the number of interactions and the energy deposited in the scintillation medium to obtain a single photon tomographic image: If only one interaction occurs, and the interaction is a photoelectric effect, and the energy deposited in the scintillation medium is within a preset energy range threshold, a low-photon energy imaging processing method is used to obtain a single-photon tomographic image; If multiple interactions occur, and the order of the interactions is at least one Compton scattering and then one photoelectric effect, and the energy deposited by the photon in the scintillation medium after all interactions is greater than the preset energy range threshold, a high-photon energy imaging processing method is used to obtain a single-photon tomographic image.

2. The non-collimated single photon tomography method according to claim 1, characterized in that: The low photon energy imaging processing method is: The number of interactions that occurred, the energy deposited in the scintillation medium, and the location where the interaction occurred were recorded; After pixelating the detector space, the count of the photons that interact with each other corresponding to each pixel in the detector space is determined according to the location where the interaction occurs; A single photon tomographic image is obtained by using a reconstruction algorithm according to the count of interacting photons corresponding to each pixel and the energy deposited in the scintillation medium.

3. The non-collimated single photon tomography method according to claim 1, characterized in that: The high photon energy imaging processing method is: The number of interactions that occurred, the energy deposited in the scintillation medium, and the location where the interaction occurred were recorded; After pixelating the imaging space, a cone surface corresponding to the Compton scattering event is obtained according to the energy deposited in the scintillation medium and the location where the interaction occurs, and it is determined whether each pixel in the imaging space is located on the cone surface; At each imaging space pixel located on the conical surface, all eligible Compton scattering events are traversed to obtain an initial reconstructed image and a system matrix; A single photon tomographic image is obtained by a reconstruction algorithm according to the initial reconstructed image and the system matrix.

4. A non-collimated single photon tomography system, implementing a non-collimated single photon tomography method according to any one of claims 1 to 3, characterized in that: The imaging system specifically comprises a detection module and a data processing module; the detection module comprises a scintillation medium array (1), a signal conversion unit (2) and a signal amplification unit (3); the data processing module comprises a signal transmission unit (4), a data acquisition unit (5) and an image reconstruction unit (6); The scintillation medium array (1) is composed of at least two layers of scintillation medium in the grid-like structure; The scintillation medium array (1) is used to interact with the photons to be measured to generate optical signals; the optical signals are converted into electrical signals by a signal conversion unit (2), amplified by a signal amplification unit (3), and then transmitted by a signal transmission unit (4) and collected by a data collection unit (5), and data processing is performed by an image reconstruction unit (6) to obtain the distribution of the photons to be measured in an imaging space.

5. The non-collimated single photon tomography system according to claim 4, characterized in that: The scintillation medium is a scintillation optical fiber or a long strip scintillator.

6. The non-collimated single photon tomography system according to claim 4, characterized in that: The light yield of the scintillating medium is greater than 30,000 ph / MeV.

7. The non-collimated single photon tomography system according to claim 4, characterized in that: The decay time of the scintillation medium is less than 40 μs.

8. The non-collimated single photon tomography system according to claim 4, characterized in that: The scintillating medium is a cerium-doped yttrium-lutetium silicate crystal, or a cerium-doped gadolinium-gallium-aluminum crystal, or a cerium-doped lutetium-aluminum garnet crystal.

9. The non-collimated single photon tomography system according to claim 4, characterized in that: The relative angle between the imaging system and the object to which the photons to be measured belong is rotated.

10. The non-collimated single photon tomography system according to claim 4, characterized in that: The surface of the scintillation medium is coated with a reflective material.

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