A method and system for non-collimated single-photon tomography

Abstract

The present invention relates to the field of radiation detection imaging technology, and discloses a non-collimated single-photon tomography method and system. Based on the non-collimated single-photon tomography system, it 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 provided 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; the photons to be measured pass through the scintillating media with a grid structure and interact once or multiple times; the imaging processing method is determined according to the number of interactions and the energy deposited in the scintillating media to obtain a single-photon tomography image. The present invention utilizes the dislocation of the grid structure to achieve photon collimation, overcoming the constraints of the mechanical collimator; and combines the two modes of image reconstruction, so that the system is suitable for the detection of photons of different energies.

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 labeled drugs used in nuclear medicine for clinical diagnosis and treatment. In clinical practice, radiopharmaceuticals will accumulate in the target tumor tissue area, and diagnosis and treatment can be performed 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] Currently, the radionuclide imaging devices commonly used in clinical practice include single-photon emission tomography (SPECT) and positron emission tomography (PET). Conventional SPECT detects and images gamma rays produced by radionuclide decay, but due to limitations of mechanical collimators, it is only suitable for detecting low-energy rays. PET, on the other hand, detects and images a pair of annihilation photons with an energy of 511 keV produced by radionuclide decay through temporal coincidence. Consequently, the energy range detectable by currently used radionuclide imaging devices is limited, and they are unable to image multiple nuclides simultaneously.

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

[0005] To solve the above technical problems, the present invention provides, on one hand, a collimation-free single-photon tomography method, which is implemented based on a collimation-free single-photon tomography system; the imaging system includes at least two layers of scintillating media in a grid structure, wherein the upper and lower layers of scintillating media in the grid structure are arranged with a preset displacement in the left-right direction, and a preset spacing is provided between each layer of scintillating media in the grid structure; each layer of scintillating media in the grid structure is composed of elongated strips of scintillating media in an orthogonal distribution;

[0006] The photons to be measured pass through the scintillation medium of the grid structure and interact with each other. 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 based on the number of interactions and the energy deposited in the scintillation medium to obtain a single photon tomography image.

[0007] 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;

[0008] If multiple interactions occur, and the order of the interactions is at least one Compton scattering followed by 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.

[0009] Preferably, the low photon energy imaging processing method is:

[0010] Record the number of interactions, the energy deposited in the scintillation medium, and the location where the interaction occurred;

[0011] After pixelating the detector space, the count of the interacting photons corresponding to each pixel in the detector space is determined according to the location where the interaction occurs;

[0012] A single photon tomographic image is obtained using a reconstruction algorithm according to the count of interacting photons corresponding to each pixel and the energy deposited in the scintillation medium.

[0013] Preferably, the high photon energy imaging processing method is:

[0014] Record the number of interactions, the energy deposited in the scintillation medium, and the location where the interaction occurred;

[0015] After pixelating the imaging space, the cone surface corresponding to the Compton scattering event is obtained based on 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;

[0016] At each imaging space pixel on the cone surface, all eligible Compton events are traversed to obtain the initial reconstructed image and system matrix;

[0017] A single photon tomographic image is obtained by a reconstruction algorithm based on the initial reconstructed image and the system matrix.

[0018] Another aspect of the present invention provides a non-collimated single-photon tomography system for realizing 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);

[0019] The scintillation medium array (1) is composed of at least two layers of scintillation medium in the grid-like structure;

[0020] 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 the signal conversion unit (2), amplified by the signal amplification unit (3), and then transmitted by the signal transmission unit (4) and collected by the data collection unit (5). The image reconstruction unit (6) performs data processing to obtain the distribution of the photons to be measured in the imaging space.

[0021] Preferably, the scintillation medium is a scintillation optical fiber or a long strip scintillator.

[0022] Preferably, the light yield of the scintillating medium is greater than 30,000 ph / MeV.

[0023] Preferably, the decay time of the scintillation medium is less than 40 μs.

[0024] 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.

[0025] Preferably, the relative angle between the imaging system and the object to which the photons to be measured belong is rotated.

[0026] Preferably, the surface of the scintillation medium is coated with a reflective material.

[0027] The embodiments of the present invention have the following technical effects:

[0028] The present application is based on an uncollimated single-photon tomography system, comprising at least two layers of scintillating media in a grid structure. The upper and lower layers of the grid structured scintillating media are provided with a preset displacement in the left-right direction, and a preset spacing is provided between each layer of the grid structured scintillating media. Each layer of the grid structured scintillating media is composed of long strips of scintillating media in an orthogonal distribution. The photons to be measured pass through the scintillating media in the grid structured scintillating media, and the photons to be measured pass through the scintillating media in the grid structured scintillating media, interacting with each other to obtain the distribution of the photons to be measured in the scintillating media. Based on the detection results, a reconstruction algorithm is used to obtain the distribution of the photons to be measured in the imaging space. This overcomes the limitations of mechanical collimators, is applicable to the detection of photons of different energies, and combines two modes of image reconstruction to make this system applicable to the detection of photons of different energies. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 11 is a schematic structural diagram of a non-collimated single-photon tomography system provided by an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the grid structure of the scintillation medium array (1) of the non-collimated single photon tomography system provided by an embodiment of the present invention;

[0032] Figure 3 1 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;

[0033] Figure 4 1 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;

[0034] Figure 5 1 is a schematic diagram of a flow chart of an imaging processing method selection process for a non-collimated single photon tomography imaging method provided by an embodiment of the present invention;

[0035] Figure 6 1 is a schematic diagram of multi-angle detection of a non-collimated single photon tomography system provided by an embodiment of the present invention;

[0036] Figure 7 This is a flowchart of a low-photon energy imaging processing method provided by an embodiment of the present invention;

[0037] Figure 8 This is a flow chart of a high-photon energy imaging processing method provided by an embodiment of the present invention; Figure 9 This is a schematic diagram of location information provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0039] When detecting radionuclides that emit single gamma photons, currently used radionuclide imaging equipment has a limited detectable energy range and cannot image multiple nuclides simultaneously. For example, traditional SPECT requires the use of a mechanical collimator. Currently, commonly used collimators are usually composed of tungsten or lead. These materials block low-energy rays better than high-energy rays. If they are to be used for high-energy ray detection, the thickness of the collimator needs to be increased, which will greatly reduce detection efficiency. This is also related to the detectors used in traditional SPECT. Sodium iodide (NaI(Tl)) detectors are usually used. NaI has a density of (3.67 g / cm³), which has a poor blocking effect on high-energy rays, resulting in a significant decrease in detection efficiency for high-energy rays.

[0040] To solve the above technical problems, the present invention provides, on one hand, a collimation-free single-photon tomography method, which is implemented based on a collimation-free single-photon tomography system; the imaging system includes at least two layers of scintillating media in a grid structure, wherein the upper and lower layers of scintillating media in the grid structure are arranged with a preset displacement in the left-right direction, and a preset spacing is provided between each layer of scintillating media in the grid structure; each layer of scintillating media in the grid structure is composed of elongated strips of scintillating media in an orthogonal distribution;

[0041] The photons to be measured pass through the scintillation medium of the grid structure and interact with each other. 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 based on the number of interactions and the energy deposited in the scintillation medium to obtain a single photon tomography image.

[0042] 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;

[0043] In some embodiments, the low photon energy imaging processing method is:

[0044] Record the number of interactions, the energy deposited in the scintillation medium, and the location where the interaction occurred;

[0045] After pixelating the detector space, the count of the interacting photons corresponding to each pixel in the detector space is determined according to the location where the interaction occurs;

[0046] A single photon tomographic image is obtained using a reconstruction algorithm according to the count of interacting photons corresponding to each pixel and the energy deposited in the scintillation medium.

[0047] Exemplarily, single photon emission tomography (SPECT) is used as a low-photon energy imaging processing method.

[0048] If multiple interactions occur, and the order of the interactions is at least one Compton scattering followed by 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.

[0049] In some embodiments, the high photon energy imaging processing method is:

[0050] Record the number of interactions, the energy deposited in the scintillation medium, and the location where the interaction occurred;

[0051] After pixelating the imaging space, a cone surface corresponding to the Compton scattering event is obtained based on 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;

[0052] At each detector spatial pixel located on the conical surface, all valid Compton events are traversed to obtain the initial reconstructed image and system matrix;

[0053] A single photon tomographic image is obtained by a reconstruction algorithm based on the initial reconstructed image and the system matrix.

[0054] Exemplarily, Compton imaging is used as the high photon energy imaging processing method.

[0055] Exemplarily, the reconstruction algorithm of the low / high photon energy imaging processing method during reconstruction 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.

[0056] 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.

[0057] Figure 5 : is a flow chart of selecting an imaging processing method for the non-collimated single photon tomography imaging method provided by an embodiment of the present invention, Figure 5 It can be seen that the main steps of the present application to achieve wide energy range X-ray imaging 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 selected to process the detection data and image it; if the energy of the incident photons is within the preset high-energy photon energy range, the Compton imaging mode is selected to process the detection data and image it.

[0058] If the incident photon generates only one photoelectric effect in the detector, the first response position and energy deposition of the photon in the detector are recorded. A determination is made as to whether the deposition energy is within a preset energy range threshold. If so, the corresponding position and energy data are stored in an uncollimated SPECT imaging dataset. The imaging dataset is statistically analyzed to obtain photon counts at different locations in the detector, and a reconstruction algorithm is used to reconstruct a three-dimensional image. The preset energy range threshold can be set based on the processing capabilities of the SPECT system.

[0059] For example, an iterative algorithm can be used to achieve image reconstruction. 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, back-projecting the correction factor into the imaging space to calculate the cumulative correction amount of each pixel, and then updating the pixel value in 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. The output result is the reconstructed image after the iteration is completed. The main difference between the iterative reconstruction of uncollimated 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, traditional SPECT can only use the data collected by the part of the detector not blocked by the collimator. The detection data used in the present invention is the full data set of all detection units, which is not limited by the physical blockage of the mechanical collimator, thereby significantly improving data utilization and reconstruction accuracy.

[0060] Exemplarily, the low photon energy imaging processing method process is as follows Figure 7 As shown in the figure, the detector space and the imaging space are first 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.

[0061] If an incident photon undergoes one or more Compton scattering events in the detector followed by a photoelectric effect, the locations and energy deposited by the Compton scattering and photoelectric effect events are recorded, and the sum of the energy deposits is determined to be above a preset energy range threshold. If so, the locations and energies of these multiple responses are stored in a Compton imaging dataset. This dataset is then screened to identify valid Compton events, and a reconstruction algorithm is used to reconstruct a three-dimensional image. Combining these two image reconstruction methods yields uncollimated single-photon tomography results that encompass both low- and high-energy ray distributions.

[0062] The imaging data set is screened based on the position and deposited energy of the Compton scattering and the position and deposited energy of the photoelectric effect recorded during a Compton event (that is, a photon undergoes one or more Compton effects in a scintillation medium, followed by a photoelectric effect). The cosine value of the Compton scattering angle is calculated to be between -1 and 1. If so, the Compton event is considered valid; otherwise, the event is discarded.

[0063] Exemplary high photon energy imaging processing methods include Figure 8 As shown in the figure, the imaging space is first pixelated, and then the cone surface corresponding to a Compton event in the data set is obtained. 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.

[0064] On the other hand, the present invention also provides a non-collimated single-photon tomography system for realizing the non-collimated single-photon tomography method described above. 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), as shown in FIG. Figure 1 As shown; illustratively, the signal conversion unit (2) may be a photomultiplier tube array.

[0065] 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 collimation of photons is achieved; and all detection data detected by the grid structure can also be used in subsequent imaging processes.

[0066] Figure 3 Schematic diagram of the non-collimated structure of the non-collimated single photon tomography system provided by the embodiment of the present invention, which consists of 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.

[0067] The scintillation medium array (1) is used to generate a photoelectric effect with the photons to be measured, thereby generating 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 the image reconstruction unit (6) performs data processing to obtain the distribution of the photons to be measured in the imaging space.

[0068] For example, 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 the 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, based on the acquired data, combined with relevant reconstruction algorithms (such as direct back projection, iteration, artificial intelligence, etc.), image reconstruction is achieved.

[0069] The scintillation medium array (1) is composed of at least two layers of scintillation medium in the grid-like structure;

[0070] For example, Figure 2 As shown, the scintillating medium array portion of the above-mentioned detection module includes: staggered long strips of scintillating medium. The staggered arrangement is a grid structure with a certain displacement in the left and right directions. The above-mentioned grid structure is composed of two layers of long strips of scintillating medium arranged orthogonally, and each layer is arranged with scintillating medium and air spaced apart. The layers of the grid structure can be separated by air, or scintillating medium with greatly different densities can be arranged to form a grid structure. That is, N scintillating media are arranged without gaps as a group, and M groups of scintillating media are arranged side by side. The two layers of scintillating media arranged side by side are arranged orthogonally in the vertical and horizontal directions to form a grid structure, as shown in FIG. Figure 2As 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 offset displacement x relative to the previous layer of grid structure, as shown Figure 3 As shown, this misalignment achieves photon collimation, overcoming the limitations of the mechanical collimator on the photon measurement range. The number of grid layers, the spacing d between the grid structures, and the misalignment displacement x are primarily determined by the required position resolution and imaging energy range of the device. If only low-energy rays are to be detected, a grid structure with fewer layers is required. If high-energy rays need to be detected or the energy range spans a wide range, from low to high energy, a grid structure with more layers is required. This is because low-energy rays have relatively low energy and poor penetration, so using a grid structure with many layers is unnecessary. For high-energy rays, due to their relatively high energy and greater penetration, a grid structure with many layers is required for good detection efficiency.

[0071] The smaller the offset x, the better the position resolution, but also requires more layers of scintillator. The number of scintillators in each layer of the mesh structure is determined by the desired detection efficiency; a greater number results in higher detection efficiency. In one embodiment, five scintillators measuring 1 mm x 1 mm x 100 mm are closely arranged as groups, with 10 groups arranged in each layer. The scintillators in the next layer are closely connected to those in the previous layer, arranged orthogonally to form a grid structure. The spacing between the upper and lower layers of the grid structure is 10 mm, and the offset is 1 mm.

[0072] In some embodiments, the scintillating medium is a scintillating optical fiber or a long strip of scintillator. The surface of the scintillating medium is coated with an enhanced mirror reflective film. This reflective film improves light collection efficiency, reduces light loss within the scintillating medium, enhances light output intensity, and improves energy resolution and spatial resolution. Furthermore, it can also prevent optical crosstalk between adjacent scintillating media. The enhanced mirror reflective film is a high-performance reflective material, typically composed of multiple layers of material, that has higher reflectivity and better reflective performance than ordinary reflective films. The enhanced mirror reflective film is just one of the materials coated on the surface of the scintillating medium; it can also be Teflon, a metal reflective film such as aluminum, or polyester film.

[0073] In some embodiments, the light yield of the scintillation medium is 30,000 ph / MeV to 40,000 ph / MeV. If the light yield is too low, the brightness of the scintillation light after the reaction will be different, affecting the monitoring of the reaction position and the determination of energy.

[0074] In some embodiments, the decay time of the scintillation medium is 20 μs to 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.

[0075] In some embodiments, the scintillating medium is a cerium-doped yttrium-lutetium silicate crystal, a cerium-doped gadolinium-gallium-aluminum crystal, or a cerium-doped lutetium aluminum garnet crystal. Structures include, but are not limited to, scintillating fibers (round or square), elongated scintillators with reflectors, and materials include, but are not limited to, cerium-doped yttrium-lutetium silicate crystals (LYSO:Ce), cerium-doped gadolinium-gallium-aluminum crystals (GAGG:Ce), or cerium-doped lutetium aluminum garnet crystals (LuAG:Ce). Dimensions include, but are not limited to, 1 mm × 1 mm × 100 mm, 0.8 mm × 0.8 mm × 100 mm, and 0.5 mm × 0.5 mm × 100 mm. The grid-structured scintillation medium plays a dual role in 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 it is too high, it will block and obstruct 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 low, the blocking effect is poor, which is not conducive to the detection of high-energy photons.

[0076] The photons to be measured can be radioactive nuclides or prompt gamma rays produced by the interaction between protons / neutrons and other rays and matter.

[0077] Exemplarily, the photomultiplier tubes in the detection module are coupled to photodetectors at both ends of each scintillation medium. The optical signals at both ends are read to obtain the position and energy information of the incident photon response in the scintillation medium. For the same scintillation medium, varying energies result in varying light intensities within the scintillation medium, and thus varying electrical signal intensities converted from the optical signals. Energy information is represented by the resulting electrical signal intensities.

[0078] 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, thereby obtaining the specific location information of the photon reaction (including the three coordinates x, y, and z). Double-ended readout refers to connecting photodetectors at both ends of a long strip or columnar scintillating fiber array. When the incident photon enters the scintillating fiber, an interaction occurs, generating scintillation photons, which are then 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 within the crystal. Photon interactions at different depths will cause the propagation mode of the scintillation light to change. 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.

[0079] 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 ( Figure 9A 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 array ( Figure 9 B and C) indicates that the z coordinate ( Figure 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.

[0080] Furthermore, to determine the depth at which radiation interacts within a scintillation fiber, the present invention sums 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 inferring the specific depth of the photon interaction. Specifically, signal intensity is typically expressed as an energy value in recorded data. Therefore, the sum of the signals at both ends of a 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 signal at the left or right end to the sum of the energies at both ends, the depth of the ray interaction can be effectively obtained. Because the signals received at different ends differ when the interaction occurs, the ratio of the signal at one end to the sum of the signals at both ends also changes. This allows the relationship between the position and the ratio to be determined, and depth information can be derived from this relationship. Therefore, this ratio provides depth information about the location of the photon interaction within the scintillation fiber, facilitating accurate depth position discrimination (DOI).

[0081] In some embodiments, the relative angle between the imaging system and the object to which the photons to be measured belong is rotated.

[0082] For example, by rotating the relative angle between the imaging system and the object to which the photons to be detected belong, 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.

[0083] The present invention uses a detector as a collimator, which not only realizes photon collimation but also realizes photon detection. 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, the scintillation medium is used as the 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 in 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 the use of 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.

[0084] 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with 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 method for non-collimated single photon tomography, characterized in that: This is achieved 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 the grid structure are arranged with a preset displacement in the left-right direction, and a preset spacing is provided between each layer of scintillating media in the grid structure; each layer of scintillating media in the 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. 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 based on the number of interactions and the energy deposited in the scintillation medium to obtain a single photon tomography 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 followed by one photoelectric effect, and the energy deposited by the photon in the scintillation medium after all interactions is greater than a preset energy range threshold, a high-photon energy imaging processing method is used to obtain a single-photon tomographic image; The high photon energy imaging processing method is: Record the number of interactions, the energy deposited in the scintillation medium, and the location where the interaction occurred; After pixelating the imaging space, a cone surface corresponding to the Compton scattering event is obtained based on 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 on the conical surface, all eligible Compton scattering events are traversed to obtain the initial reconstructed image and system matrix; A single photon tomographic image is obtained by a reconstruction algorithm based on the initial reconstructed image and the system matrix.

2. The method for non-collimated single photon tomography according to claim 1, characterized in that: The low photon energy imaging processing method is: Record the number of interactions, the energy deposited in the scintillation medium, and the location where the interaction occurred; After pixelating the detector space, the count of the interacting photons 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 using a reconstruction algorithm according to the count of interacting photons corresponding to each pixel and the energy deposited in the scintillation medium.

3. A non-collimated single photon tomography system, implementing the non-collimated single photon tomography method according to any one of claims 1 to 2, characterized in that: The imaging system specifically includes a detection module and a data processing module; the detection module includes a scintillation medium array (1), a signal conversion unit (2) and a signal amplification unit (3); the data processing module includes 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 the signal conversion unit (2), amplified by the signal amplification unit (3), and then transmitted by the signal transmission unit (4) and collected by the data collection unit (5). The image reconstruction unit (6) performs data processing to obtain the distribution of the photons to be measured in the imaging space.

4. The non-collimated single photon tomography system according to claim 3, characterized in that: The scintillation medium is a scintillation optical fiber or a long strip scintillator.

5. The non-collimated single photon tomography system according to claim 3, characterized in that: The light yield of the scintillating medium is greater than 30,000 ph / MeV.

6. The non-collimated single photon tomography system according to claim 3, characterized in that: The decay time of the scintillation medium is less than 40 μs.

7. The non-collimated single photon tomography system according to claim 3, 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.

8. The non-collimated single photon tomography system according to claim 3, characterized in that: The relative angle between the imaging system and the object to which the photons to be measured belong is rotated.

9. The non-collimated single photon tomography system according to claim 3, characterized in that: The surface of the scintillation medium is coated with a reflective material.

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