Depth information correction methods, systems and equipment in PET detectors

Abstract

This application discloses a depth information correction method, system, and device in a PET detector, relating to the technical fields of PET and related fields. The depth information correction method in a PET detector includes: acquiring first energy data of the electrical signal from a first photodetector unit and second energy data of the electrical signal from a second photodetector unit, and determining an energy ratio based on the first and second energy data; performing first-weighted center location based on the position data of the first photodetector unit and the first energy data to determine first energy centroid data at a first end, and performing first-weighted center location based on the position data of the second photodetector unit and the second energy data to determine second energy centroid data at a second end; performing second-weighted center location based on the first energy data, second energy data, first energy centroid data, and second energy centroid data to determine cross-sectional position data corresponding to photon interaction points in the crystal; and determining the interaction depth of the crystal based on the cross-sectional position data and the energy ratio.

Description

Technical Field

[0001] This application relates to the technical fields of PET and other related fields, and in particular to a method, system and device for depth information correction in a PET detector. Background Technology

[0002] In nuclear medicine imaging techniques such as positron emission tomography (PET), the annihilation of positrons and electrons produces a pair of 511 keV gamma photons. These photons fly out in opposite directions and are captured by scintillation crystals on the detector ring. Traditional PET detectors can only determine which pair of crystals the gamma photons occurred in, generating a line of response (LOR) with the two crystal surfaces as endpoints, but cannot determine the depth of interaction (DOI) at which the gamma photons interact. When gamma photons are incident on the crystal at an angle, the reconstruction algorithm assumes that the photons are incident from the crystal surface, which leads to a significant decrease in the spatial resolution of the field of view (FOV), the so-called "parallax error." The dual-ended readout method uses the energy ratio of the coupling between the photodetector and the two ends of the crystal to measure the DOI. Due to the attenuation effect, the number of photons reaching the two end faces (i.e., the energy obtained by the SiPM) will be different. The closer to the interaction point, the higher the energy of the received photons. The interaction depth DOI can be estimated by the energy ratio of the two ends. However, the related technology is not very effective in estimating the interaction depth, resulting in a low DOI resolution. Summary of the Invention

[0003] The embodiments of this application aim to at least partially solve one of the technical problems in the related art. Therefore, the purpose of the embodiments of this application is to provide a method, system, device, and medium for depth information correction in a PET detector, thereby improving the resolution of depth information.

[0004] This application provides a depth information correction method for a PET detector. The crystal includes a first end and a second end. A first photodetector unit is disposed at the first end, and a second photodetector unit is disposed at the second end. The depth information correction method for the PET detector includes: acquiring first energy data of the electrical signal of the first photodetector unit and second energy data of the electrical signal of the second photodetector unit, and determining an energy ratio based on the first energy data and the second energy data; performing first energy weighting center positioning based on the position data of the first photodetector unit and the first energy data to determine the first energy centroid data of the first end, and performing first energy weighting center positioning based on the position data of the second photodetector unit and the second energy data to determine the second energy centroid data of the second end; performing second energy weighting center positioning based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data to determine the cross-sectional position data corresponding to the photon interaction point in the crystal; and determining the interaction depth of the crystal based on the cross-sectional position data and the energy ratio.

[0005] For example, the first photoelectric detection unit includes a plurality of first coupling units arranged in an array; the first energy weighted center positioning based on the position data and first energy data of the first photoelectric detection unit to determine the first energy centroid data of the first end includes: calculating the sum of the first energy data of the plurality of first coupling units as the total energy of the first end; multiplying the position data of each first coupling unit with its corresponding first energy data and then summing them to obtain the weighted energy sum of the first end; and using the ratio of the weighted energy sum of the first end to the total energy of the first end as the first energy centroid data.

[0006] For example, the second photoelectric detection unit includes a plurality of second coupling units arranged in an array; the first energy weighted center positioning is performed based on the position data and second energy data of the second photoelectric detection unit to determine the second energy centroid data of the second end, including: calculating the sum of the second energy data of the plurality of second coupling units as the total energy of the second end; multiplying the position data of each second coupling unit with its corresponding second energy data and then summing them to obtain the weighted energy sum of the second end; and using the ratio of the weighted energy sum of the second end to the total energy of the second end as the second energy centroid data.

[0007] For example, determining the cross-sectional position data corresponding to the photon interaction point in the crystal based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data includes: determining a first energy product based on the first energy data and the first energy centroid data; determining a second energy product based on the second energy data and the second energy centroid data; determining the sum of the energies based on the first energy data and the second energy data; determining the sum of the first energy product and the second energy product; and determining the cross-sectional position data based on the ratio between the sum and the sum of the energies.

[0008] For example, the direction from the first end to the second end is the crystal length direction, the cross-sectional position data is located between the first end and the second end, and the cross-sectional position data is perpendicular to the crystal length direction.

[0009] For example, the first photoelectric detection unit includes a plurality of first coupling units, and the second photoelectric detection unit includes a plurality of second coupling units, with each of the plurality of first coupling units corresponding to one of the plurality of second coupling units.

[0010] For example, the first photoelectric detection unit includes a plurality of first coupling units, the second photoelectric detection unit includes a plurality of second coupling units, the plurality of first coupling units are arranged in an array at the first end, and the plurality of second coupling units are arranged in an array at the second end.

[0011] For example, the cross-sectional position data is located in the plane formed by the x-axis and y-axis, and the cross-sectional position data includes x-axis data and y-axis data; based on the cross-sectional position data and energy ratio, the interaction depth of the crystal is determined, including: determining the index data corresponding to the x-axis data, y-axis data and energy ratio; and mapping the lookup table based on the index data to obtain the interaction depth of the crystal.

[0012] For example, the lookup table is constructed as follows: a physical simulation model of the PET detector is established, wherein the physical simulation model includes a crystal and a photodetector; the physical simulation model is subjected to N photon incident events to obtain the first simulated energy data of the electrical signal of the first photodetector unit, the second simulated energy data of the electrical signal of the second photodetector unit, the x-axis simulation data, the y-axis simulation data, the simulated energy ratio, and the simulated interaction depth; based on the x-axis simulation data and the y-axis simulation data, the maximum x-axis position data, the minimum x-axis position data, the maximum y-axis position data, and the minimum y-axis position data are determined, and based on the simulated energy ratio, the maximum energy ratio and the minimum energy ratio are determined; the x-axis simulation data, the y-axis simulation data, and the simulated energy ratio are meshed to determine the corresponding index data; and the lookup table is obtained based on the index data and the simulated interaction depth.

[0013] For example, the simulation data along the x-axis, the simulation data along the y-axis, and the simulation energy ratio are meshed to determine the corresponding index data, including: obtaining first interval data based on the maximum and minimum x-axis position data; obtaining second interval data based on the maximum and minimum y-axis position data; obtaining third interval data based on the maximum and minimum energy ratios; meshing the x-axis simulation data based on the first interval data to obtain first index data; meshing the y-axis simulation data based on the second interval data to obtain second index data; and meshing the simulation energy ratio based on the third interval data to obtain third index data; and finally, obtaining index data based on the first, second, and third index data.

[0014] Another embodiment of this application provides a depth information correction system for a PET detector. The crystal includes a first end and a second end. A first photodetector unit is disposed at the first end, and a second photodetector unit is disposed at the second end. The depth information correction system for the PET detector includes: an acquisition module, used to acquire first energy data of the electrical signal of the first photodetector unit and second energy data of the electrical signal of the second photodetector unit, and determine an energy ratio based on the first energy data and the second energy data; a first determination module, used to perform first energy weighting center positioning based on the position data of the first photodetector unit and the first energy data to determine the first energy centroid data of the first end, and to perform first energy weighting center positioning based on the position data of the second photodetector unit and the second energy data to determine the second energy centroid data of the second end; a second determination module, used to perform second energy weighting center positioning based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data to determine the cross-sectional position data corresponding to the photon interaction point in the crystal; and an acquisition module, used to determine the interaction depth of the crystal based on the cross-sectional position data and the energy ratio.

[0015] Another embodiment of this application provides an electronic device having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of any of the above embodiments.

[0016] Another embodiment of this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of any of the above embodiments.

[0017] In the above embodiments, the depth information correction method in the PET detector includes a crystal comprising a first end and a second end, wherein a first photodetector unit is disposed at the first end and a second photodetector unit is disposed at the second end; the depth information correction method in the PET detector includes: acquiring first energy data of the electrical signal of the first photodetector unit and second energy data of the electrical signal of the second photodetector unit, and determining an energy ratio based on the first energy data and the second energy data; performing first energy weighting center positioning based on the position data of the first photodetector unit and the first energy data to determine the first energy centroid data of the first end, and performing first energy weighting center positioning based on the position data of the second photodetector unit and the second energy data to determine the second energy centroid data of the second end; performing second energy weighting center positioning based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data to determine the cross-sectional position data corresponding to the photon interaction point in the crystal; and determining the interaction depth of the crystal based on the cross-sectional position data and the energy ratio. By separately collecting energy data corresponding to the photodetectors at both ends of the crystal and calculating the energy ratio, and combining the energy data and position data at both ends to solve for the energy centroid data at both ends, and then relying on multiple types of data to jointly determine the cross-sectional position data of the photon interaction point and accurately calculate the crystal interaction depth by combining the energy ratio, it is possible to effectively achieve high-precision real-time correction of the photon interaction depth of the PET detector crystal, reduce the imaging position deviation and resolution attenuation caused by crystal edge and depth differences, suppress image distortion and artifacts caused by depth effects, and improve the spatial resolution and positioning accuracy of the PET system. Attached Figure Description

[0018] Figure 1 A schematic diagram illustrating the visual errors caused by DOI in the embodiments of this application; Figure 2 A schematic diagram illustrating the principle of the energy ratio method provided for the related technologies of this application; Figure 3 A schematic diagram illustrating the principle of a time difference method provided for another related technology of this application; Figure 4 Flowchart of a depth information correction method in a PET detector provided for embodiments of this application; Figure 5 A schematic diagram of the PET detector structure provided for an embodiment of this application; Figure 6 Flowchart of another depth information correction method in a PET detector provided for embodiments of this application; Figure 7 A block diagram of a depth information correction system in a PET detector provided in another embodiment of this application; Figure 8 A block diagram of an electronic device provided for another embodiment of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0020] In nuclear medicine imaging techniques such as positron emission tomography (PET), the annihilation of positrons and electrons produces a pair of 511 keV gamma photons. These photons fly out in opposite directions and are captured by scintillation crystals on the detector ring. Traditional PET detectors can only determine which pair of crystals the gamma photons occurred in, generating a line of response (LOR) with the two crystal surfaces as endpoints, but cannot determine the depth of interaction (DOI) at which the gamma photons interact. When gamma photons are incident on the crystal at an angle, the reconstruction algorithm assumes that the photons are incident from the crystal surface, which leads to a significant decrease in the spatial resolution of the field of view (FOV), the so-called "parallax error." Figure 1 As shown.

[0021] DOI resolution is one of the key factors affecting image spatial resolution. Positron emission tomography (PET) detectors typically use long, narrow crystals to achieve a balance between spatial resolution and sensitivity. However, as the radial offset of the point of action increases, the radial spatial resolution of the PET detector ring decreases due to the depth of action (DOI) effect, which is most pronounced in small animal and brain PET scanners using small crystal elements and small apertures. Axial spatial resolution also decreases if large oblique events are received, which is most evident in long-axis whole-body clinical PET scanners. Coincidence timing resolution (CTR) is another important parameter of PET scanners. A good CTR improves the accuracy of time-of-flight (TOF) measurements, thereby reducing uncertainty in the annihilation location of response lines and improving the image signal-to-noise ratio. Therefore, scan time can be shortened or radiopharmaceutical dosage can be reduced. However, temporal dispersion caused by parallax error reduces the accuracy of both coincidence timing resolution (CTR) and time-of-flight (TOF) measurements.

[0022] These errors can be corrected by measuring the DOI, thereby improving spatial and temporal resolution. However, since scintillation photons (visible light) are isotropically distributed, scintillation photons at the crystal edges are prone to leakage from the sides. Gamma photons also escape when interacting at the crystal edges (gamma photons cannot be directly recorded by photodetectors; they must first be converted into scintillation photons in the crystal and then into electrical signals for the photodetector to detect them), leading to a reduction in the number of scintillation photons. These edge effects mean that the energy ratio and interaction depth are not a simple correspondence, requiring correction through effective methods.

[0023] The scintillation light attenuates as it propagates within the crystal, primarily due to absorption by the crystal itself and losses from interface reflection. The dual-ended readout method uses the energy ratio between the photodetector and the two ends of the crystal to measure the depth of interaction (DOI). Due to the attenuation effect, the number of photons reaching the two ends (i.e., the energy received by the SiPM (Silicon Photomultiplier)) will differ; the closer to the interaction point, the higher the energy of the received photons. The DOI can be calculated from the energy ratio at both ends.

[0024] In one embodiment, the energy ratio method of a two-ended DOI can be used (e.g. Figure 2 As shown in the figure, the energy ratio is based on the attenuation effect of the scintillation light propagating in the crystal. The scintillation light generated by the interaction at crystal depth z propagates to the two end faces. Due to the attenuation effect, the number of photons reaching the two end faces (i.e., the energy obtained by SiPM) will be different. The end face closer to the interaction point receives higher photon energy. The interaction depth can be calculated from the energy ratio collected by the two end faces, as shown in formula (1): (1) Where R is the energy ratio, E1 is the energy of the upper end face of the crystal, and E2 is the energy of the lower end face of the crystal, the interaction depth is as shown in formula (2): (2) Where L is the crystal length and DOI is the depth at which gamma photons interact within the crystal.

[0025] This energy ratio method is based on an idealized linear relationship between the energy ratio of scintillation light propagating to both sides within a crystal and the DoI (Discretionary Opportunity). However, the propagation of scintillation photons in a crystal is affected by total internal reflection, scattering, and absorption, resulting in a random path, especially pronounced in long crystals. The DoI is approximately linear in the middle of the crystal, but tends to saturate near the ends. At the crystal ends, even small signal fluctuations can cause significant shifts in the DoI estimate. Furthermore, since scintillation photons are isotropically distributed, crystal edge effects mean that the energy ratio and DoI are not a simple correspondence. Because this energy ratio method suffers from the nonlinearity of the DoI at the crystal ends and edge effects, the DoI resolution is relatively low.

[0026] In another embodiment, a time difference DOI method with two-ended DOI can be used (e.g., ...). Figure 3 As shown in the figure), the time difference method is based on the scintillation photons generated when gamma photons interact within a crystal and fly in straight lines along the length of the crystal to both ends. The closer the end is to the interaction point, the earlier the photon arrives. The time difference between the two ends of the crystal is used to estimate the crystal depth DOI where the interaction occurs. The calculation method is shown in formula (3): (3) Where T is the total flight time, T1 is the time it takes for the photon to reach the upper surface of the crystal, T2 is the time it takes for the photon to reach the lower surface of the crystal, and DOI is the depth (normalized value) where the gamma photon interacts within the crystal.

[0027] The essence of this time difference DOI method is the time-of-flight principle within the crystal, as shown in formula (4): (4) Where L is the distance between the two ends, d is half the difference in flight distance, and c is the speed of light. This represents the time difference between the two ends of the flight.

[0028] This time-difference DOI method is based on the scintillation photons generated when gamma photons interact within a crystal, traveling in straight lines along the length of the crystal to both ends. However, the propagation of scintillation photons in the crystal is affected by multiple reflections, resulting in random paths that are typically longer than straight paths. This randomness disperses the flight time. At the end closer to the interaction point, the photon flight path is shorter, resulting in a larger number of photons arriving at a more accurate time. Conversely, at the end farther from the interaction point, the photon flight path is longer, with greater reflection and attenuation, resulting in only a small number of photons arriving at a less accurate time. Therefore, this energy ratio method has a lower DOI resolution.

[0029] In response, another embodiment of this application proposes a depth information correction method for PET detectors. This method employs a dual-end readout detector structure optically coupled to a crystal and multiple small-sized SiPMs. Distributed energy values ​​at multiple locations are collected from both ends of the crystal. A double-energy weighted centering localization method is used to determine the position of the interaction point on the crystal cross-section. The interaction depth (DOI) is determined by the cross-sectional position and energy ratio. An interaction depth z closer to the actual physical model is obtained by looking up a table, avoiding the nonlinear errors in DOI at the crystal edges and ends caused by relying entirely on linear correspondence, thus effectively improving DOI resolution. Accurate DOI information further enhances both spatial and temporal resolution.

[0030] Figure 4 A flowchart of a depth information correction method for a PET detector provided in an embodiment of this application.

[0031] like Figure 4 As shown, the depth information correction method 400 in the PET detector provided in this application includes, for example, steps S410-S440. The PET detector is composed of a crystal and a photodetector. The crystal is used to receive photons and convert them into optical signals. The photodetector converts the optical signals into electrical signals for imaging. The crystal includes a first end and a second end. A first photodetector unit is provided at the first end, and a second photodetector unit is provided at the second end.

[0032] Step S410: Obtain the first energy data of the electrical signal of the first photoelectric detection unit and the second energy data of the electrical signal of the second photoelectric detection unit, and determine the energy ratio based on the first energy data and the second energy data. For example, the first photoelectric detection unit includes multiple first coupling units, and the second photoelectric detection unit includes multiple second coupling units. This application uses four first coupling units and four second coupling units as an example for explanation and illustration, which is not intended to limit the application. Each first coupling unit corresponds to a first energy data, and each second coupling unit corresponds to a second energy data. The sum of the first energy data corresponding to multiple first coupling units is used to obtain the total energy at the first end, and the sum of the second energy data corresponding to multiple second coupling units is used to obtain the total energy at the second end. The energy ratio is obtained by dividing the total energy at the first end by the total energy at the second end.

[0033] Step S420: Based on the position data and first energy data of the first photoelectric detection unit, perform first energy weighted center positioning to determine the first energy centroid data of the first end; and based on the position data and second energy data of the second photoelectric detection unit, perform first energy weighted center positioning to determine the second energy centroid data of the second end. For example, the position data of each first coupling unit is multiplied and accumulated with the corresponding first energy data to obtain the first-end weighted energy sum. The first-end weighted energy sum is then divided by the first-end total energy to obtain the first energy centroid data. The position data includes the first x-axis coordinate and the first y-axis coordinate. The first x-axis coordinate and the first y-axis coordinate are calculated separately to obtain the x-axis coordinate and y-axis coordinate of the first energy centroid data. Similarly, the position data of each second coupling unit is multiplied and accumulated with the corresponding second energy data to obtain the second-end weighted energy sum. The second-end weighted energy sum is then divided by the second-end total energy to obtain the second energy centroid data. The position data includes the second x-axis coordinate and the second y-axis coordinate. The second x-axis coordinate and the second y-axis coordinate are calculated separately to obtain the x-axis coordinate and the y-axis coordinate of the second energy centroid data.

[0034] Step S430: Based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data, determine the cross-sectional position data corresponding to the photon interaction point in the crystal.

[0035] For example, the cross-sectional position data corresponding to the photon interaction point includes x-axis data and y-axis data. A first energy product is obtained by multiplying the x-axis coordinate of the first energy centroid data with the total energy at the first end, and the y-axis coordinate of the first energy centroid data with the total energy at the first end, respectively. A second energy product is obtained by multiplying the x-axis coordinate of the second energy centroid data with the total energy at the second end, and the y-axis coordinate of the second energy centroid data with the total energy at the second end, respectively. The first energy product and the second energy product corresponding to the x-axis coordinate are added to obtain a first calculation result, which determines the sum of the energy at the first and second ends. The first calculation result is then divided by the sum of the energy to obtain the x-axis data of the cross-sectional position data. Similarly, the first energy product and the second energy product corresponding to the y-axis coordinate are added to obtain a second calculation result, which is then divided by the sum of the energy to obtain the y-axis data of the cross-sectional position data.

[0036] Step S440: Determine the interaction depth of the crystal based on the cross-sectional position data and energy ratio.

[0037] For example, the interaction depth of a crystal can be obtained by looking up a lookup table (LUT) based on the x-axis data, y-axis data, and energy ratio of the cross-sectional position data. When looking up the table, the x-axis data, y-axis data, and energy ratio must first be converted into the corresponding index data of the table. Then, the interaction depth of the crystal is determined based on the interaction depth corresponding to the index data. The lookup table is obtained by performing N photon incident simulations using a physical simulation model of a PET detector.

[0038] In the above embodiments, by collecting energy data corresponding to the photodetectors at both ends of the crystal and calculating the energy ratio, combining the energy data and position data at both ends to solve for the energy centroid data at both ends, and then relying on multiple types of data to jointly determine the cross-sectional position data of the photon interaction point and accurately calculate the crystal interaction depth by combining the energy ratio, it is possible to effectively achieve high-precision real-time correction of the photon interaction depth of the PET detector crystal, reduce the imaging position deviation and resolution attenuation caused by crystal edge and depth differences, suppress image distortion and artifacts caused by depth effects, and improve the spatial resolution and positioning accuracy of the PET system.

[0039] Figure 5 A schematic diagram of the PET detector structure provided for an embodiment of this application.

[0040] In one example, the first photodetector unit includes multiple first coupling units, and the second photodetector unit includes multiple second coupling units, with each of the multiple first coupling units corresponding to one of the multiple second coupling units. Specifically, such as Figure 5 As shown, the PET detector includes a crystal and a photodetector (each photodetector consists of multiple small-sized SiPM couplings), and the first photodetector unit includes four first coupling units ( , , The second photoelectric detection unit includes four second coupling units ( , , ), and , and , and , and One-to-one correspondence.

[0041] In one example, the first photodetector unit includes a plurality of first coupling units, the second photodetector unit includes a plurality of second coupling units, the plurality of first coupling units are arranged in an array at the first end, and the plurality of second coupling units are arranged in an array at the second end.

[0042] Specifically, such as Figure 5 As shown, there are 4 first coupling units ( , , The four second coupling units are arranged in an array at the first end (left end / A end). , , They are arranged in an array at the second end (right end / B end).

[0043] In one example, the direction from the first end to the second end is the crystal length direction, the cross-sectional position data is located between the first end and the second end, and the cross-sectional position data is perpendicular to the crystal length direction.

[0044] Specifically, such as Figure 5 As shown, the direction from the first end (left end) to the second end (right end) is the crystal length direction, the crystal length is L, and the cross-sectional position data (cross-sectional position (x, y)) is perpendicular to the crystal length direction z.

[0045] In one example, the first photoelectric detection unit includes multiple first coupling units arranged in an array; the first energy weighted center localization is performed based on the position data and first energy data of the first photoelectric detection unit to determine the first energy centroid data of the first end, including: calculating the sum of the first energy data of the multiple first coupling units as the total energy of the first end; multiplying the position data of each first coupling unit with its corresponding first energy data and then summing them to obtain the weighted energy sum of the first end; and using the ratio of the weighted energy sum of the first end to the total energy of the first end as the first energy centroid data. Specifically, such as Figure 5 As shown, the SiPM position data at end A ( flat): =( , ), =1,2,3,4; Energy distribution at end A (first energy data): , , SiPM position data at end B (z=L plane): =( , ), =1,2,3,4; Energy distribution at end B (second energy data): , , ; Calculate the sum of the first energy data of multiple first coupling units as the total energy at the first end. As shown in formula (5): (5) Multiply the position data of each first coupling unit by its corresponding first energy data. and After summing, we obtain the first-end weighted energy sum. and ).

[0046] Sum the weighted energy at the first end with the total energy at the first end. The ratio of the first energy center of gravity data is used as the first energy center of gravity data. As shown in formula (6): (6) In one example, the second photoelectric detection unit includes multiple second coupling units arranged in an array; based on the position data and second energy data of the second photoelectric detection unit, a first weighted energy center is located to determine the second energy centroid data of the second end, including: calculating the sum of the second energy data of the multiple second coupling units as the total energy of the second end; multiplying the position data of each second coupling unit with its corresponding second energy data and then summing them to obtain the weighted energy sum of the second end; and using the ratio of the weighted energy sum of the second end to the total energy of the second end as the second energy centroid data. Specifically, such as Figure 5 As shown, the SiPM position data at end A ( flat): =( , ), =1,2,3,4; Energy distribution at end A (first energy data): , , SiPM position data at end B (z=L plane): =( , ), =1,2,3,4; Energy distribution at end B (second energy data): , , The sum of the second energy data of multiple second coupling units is calculated as the total energy at the second end. As shown in formula (7): (7) Multiply the position data of each second coupling unit by its corresponding second energy data. and After summing, we obtain the weighted energy at the second end. and ).

[0047] Sum the weighted energy at the second end with the total energy at the second end. The ratio of these values ​​is used as data for the second energy center of gravity. As shown in formula (8): (8) In one example, determining the cross-sectional position data corresponding to the photon interaction point in the crystal based on first energy data, second energy data, first energy centroid data, and second energy centroid data includes: determining a first energy product based on the first energy data and the first energy centroid data; determining a second energy product based on the second energy data and the second energy centroid data; determining the sum of energies based on the first energy data and the second energy data; determining the sum of the first energy product and the second energy product; and determining the cross-sectional position data based on the ratio between the sum and the sum of energies.

[0048] Specifically, the cross-sectional position data includes x-axis data and y-axis data. Based on the first energy data and the first energy centroid data, the first energy product is determined. and Based on the second energy data and the second energy centroid data, the second energy product is determined. and Based on the first energy data and the second energy data, determine the energy and value. The sum of the first energy product and the second energy product is and Then the cross-sectional location data ( As shown in formulas (9) and (10): (9) (10) In one example, the cross-sectional position data is located in the plane formed by the x-axis and y-axis, and the cross-sectional position data includes x-axis data and y-axis data; based on the cross-sectional position data and energy ratio, the interaction depth of the crystal is determined, including: determining the index data corresponding to the x-axis data, y-axis data and energy ratio; and mapping the lookup table based on the index data to obtain the interaction depth of the crystal.

[0049] Specifically, the lookup table is built based on the physical simulation model of the PET detector. The lookup table includes the grid range for each data point (x-axis simulation data, y-axis simulation data, and simulation energy ratio). The lookup table is then used to analyze the x-axis data, y-axis data, and energy ratio based on the grid range. Mesh division is performed to obtain x-axis data, y-axis data and index data corresponding to the energy ratio. The energy ratio R is obtained based on formula (11). The data is searched in the lookup table according to the index data to obtain the interaction depth of the crystal.

[0050] (11) In the above embodiments, by measuring the cross-sectional position By looking up the interaction depth z with the double-ended energy ratio R, a value closer to the real physical model is obtained. This avoids the nonlinear error of DOI at the crystal edge and both ends caused by relying entirely on the linear correspondence, and effectively improves the DOI resolution.

[0051] In one example, the lookup table is constructed as follows: a physical simulation model of the PET detector is established, which includes a crystal and a photodetector; the physical simulation model is subjected to N photon incident events to obtain the first simulated energy data of the electrical signal of the first photodetector unit, the second simulated energy data of the electrical signal of the second photodetector unit, the x-axis simulation data, the y-axis simulation data, the simulated energy ratio, and the simulated interaction depth; based on the x-axis and y-axis simulation data, the maximum x-axis position data, the minimum x-axis position data, the maximum y-axis position data, and the minimum y-axis position data are determined, and based on the simulated energy ratio, the maximum energy ratio and the minimum energy ratio are determined; the x-axis simulation data, the y-axis simulation data, and the simulated energy ratio are meshed to determine the corresponding index data; and the lookup table is obtained based on the index data and the simulated interaction depth.

[0052] Specifically, a physical simulation model of the gamma photon incident crystal (the physical simulation model of the PET detector) is established, which can be achieved through methods such as Monte Carlo simulation or machine learning, or through statistical experiments. The physical simulation model of the PET detector consists of a scintillator (crystal) and eight SiPM detectors on two end faces. The simulation covers the physical processes and parameters of gamma photon interaction (photoelectric effect, Compton effect, electron-electron pair effect), energy deposition emitting scintillating light, photon propagation (attenuation, absorption, reflection, escape), and SiPM photon detection (quantum efficiency, dark noise). A simulation dataset is generated from the physical simulation model of the PET detector. Each sample corresponds to a gamma photon event, and N is the total number of events. The positions of the interaction points on the crystal cross-section (x-axis simulation data, y-axis simulation data). This refers to the depth of interaction (the depth of the simulated interaction). The energy ratio of the two end faces (simulated energy ratio).

[0053] Establish a three-dimensional discrete mapping: in: , , , , For the maximum x-axis position data, For minimum x-axis position data, For the maximum y-axis position data and For minimum y-axis position data, For maximum energy ratio, For the minimum energy ratio; for each Determine the grid cell ,in The lookup table is obtained based on the index data and the depth of the simulation interaction.

[0054] In one example, the simulation data along the x-axis, y-axis, and simulation energy ratio are meshed to determine the corresponding index data. This includes: obtaining first interval data based on the maximum and minimum x-axis position data; obtaining second interval data based on the maximum and minimum y-axis position data; obtaining third interval data based on the maximum and minimum energy ratios; meshing the x-axis simulation data based on the first interval data to obtain first index data; meshing the y-axis simulation data based on the second interval data to obtain second index data; and meshing the simulation energy ratio based on the third interval data to obtain third index data; finally, index data is obtained based on the first, second, and third index data.

[0055] Specifically, for each Determine the grid cell (Index data), as shown in formula (12): (12) in, (First interval data) (Second interval data) (Third interval data) , , The total number of events for x-axis simulation data, y-axis simulation data, and simulation energy ratio, respectively, for any... Determine the corresponding grid cell: (First index data) (Second index data) (Third index data).

[0056] The LUT lookup table is obtained based on the index data and the simulation interaction depth: ,in This is the corrected interaction depth (simulated interaction depth).

[0057] The depth information correction method for PET detectors proposed in this application employs a novel dual-ended DOI method to collect distributed energy values ​​at multiple locations on both ends of the crystal. A double-energy weighted centering localization method is used to determine the position of the interaction point on the crystal cross-section, resulting in more accurate localization. The interaction depth DOI is determined by the cross-sectional position and energy ratio. By mapping a lookup table to the real physical model, the nonlinear errors of the DOI at the crystal edges and ends caused by relying entirely on linear correspondence are avoided, effectively improving DOI resolution. A dual-ended readout detector structure is employed, optically coupled between a crystal and multiple small-sized SiPMs. The small-sized SiPMs have small equivalent capacitance, resulting in a steeper SiPM signal rise edge, smaller amplitude-time wander during over-threshold triggering, less temporal dispersion, and better CRT temporal resolution. Therefore, the dual-ended DOI method of this invention can simultaneously achieve high spatial resolution and high temporal resolution.

[0058] Figure 6 Another method flow for depth information correction in a PET detector provided for embodiments of this application, such as... Figure 6 As shown, the depth information correction methods in PET detectors include S601-S607.

[0059] S601 collects energy distributed at both ends of the crystal.

[0060] For example, energy is distributed at end A (first energy data): , , Energy distribution at end B (second energy data): , , And obtain the SiPM location data at end A ( flat): =( , ), =1,2,3,4; B-end SiPM position data (z=L plane): =( , ), =1,2,3,4.

[0061] S602, calculate the sum of the energies at ends A and B respectively.

[0062] For example, the sum of the first energy data of a plurality of first coupling units is calculated as the total energy at the first end. The sum of the second energy data of multiple second coupling units is calculated as the total energy at the second end. .

[0063] S603, calculate the two-terminal energy ratio R.

[0064] For example, according to and The ratio of to is used to obtain the energy ratio R.

[0065] S604, First-stage energy weighted centroid positioning, calculate the centroid coordinates at point A: And the centroid coordinates of end B: .

[0066] For example, the position data of each first coupling unit is multiplied by its corresponding first energy data. and After summing, we obtain the first-end weighted energy sum. and The weighted energy at the first end is summed with the total energy at the first end. The ratio of the first energy center of gravity data is used as the first energy center of gravity data. (Center coordinates of end A); Similarly, multiply the position data of each second coupling unit by its corresponding second energy data ( and After summing, we obtain the weighted energy at the second end. and The weighted energy at the second end is summed with the total energy at the second end. The ratio of these values ​​is used as data for the second energy center of gravity. (Coordinates of the center of gravity at end B).

[0067] S605, second-level energy weighted center positioning, calculate cross-sectional position data: (x,y).

[0068] For example, the cross-sectional position data includes x-axis data and y-axis data, and the first energy product is determined based on the first energy data and the first energy centroid data. and Based on the second energy data and the second energy centroid data, the second energy product is determined. and Based on the first energy data and the second energy data, determine the energy and value. The sum of the first energy product and the second energy product is and Thus, the cross-sectional location data can be obtained based on the ratio of the sum to the sum of energy values. ).

[0069] S606, Physical Modeling, Creating a LUT Lookup Table.

[0070] For example, a physical simulation model of a gamma photon incident crystal (the physical simulation model of a PET detector) is established, which can be achieved through methods such as Monte Carlo simulation or machine learning, or through statistical experiments. The physical simulation model of the PET detector consists of a scintillator (crystal) and eight SiPM detectors on two end faces. The simulation covers the physical processes and parameters of gamma photon incident crystal interactions (photoelectric effect, Compton effect, electron-electron pair effect), energy deposition emitting scintillating light, photon propagation (attenuation, absorption, reflection, escape), and SiPM photon detection (quantum efficiency, dark noise). A simulation dataset is generated from the physical simulation model of the PET detector. Each sample corresponds to a gamma photon event, and N is the total number of events. The positions of the interaction points on the crystal cross-section (x-axis simulation data, y-axis simulation data). This refers to the depth of interaction (the depth of the simulated interaction). The energy ratio between the two end faces (simulated energy ratio). Establish a three-dimensional discrete mapping: in: , , , , For the maximum x-axis position data, For minimum x-axis position data, For the maximum y-axis position data and For minimum y-axis position data, For maximum energy ratio, For the minimum energy ratio; for each Determine the grid cell ,in The lookup table is obtained based on the index data and the depth of the simulation interaction.

[0071] S607, input the cross-sectional position data and the two-end energy ratio (x,y,R), and look up the table to obtain the interaction depth z.

[0072] In the above embodiments, the PET detector consists of a scintillator (crystal) and a SiPM silicon photomultiplier tube, employing a dual-end readout detector structure where a single crystal is optically coupled to multiple small-sized SiPMs. Distributed energy values ​​at multiple locations are collected from the two end faces of the crystal for first-level energy weighting centering location. The energy of each end face and its position relative to the first-level energy weighting centering location can be used for second-level energy weighting centering location, determining the position of the interaction point on the crystal cross-section. The dual-end energy ratio is obtained from the energy of each end face. A physical simulation model of gamma photons incident on the crystal is established, and a discrete mapping of a three-dimensional LUT lookup table is created based on the simulation model between the cross-sectional position, energy ratio, and DOI. By looking up the table for the cross-sectional position (x, y) and the dual-end energy ratio R, an interaction depth z closer to the real physical model is obtained, thereby eliminating DOI nonlinearity errors at the crystal edges and ends, effectively improving DOI resolution, and further enhancing spatial and temporal resolution with accurate DOI information.

[0073] The depth information correction method proposed in this application for PET detectors is a novel dual-ended DOI method. It employs a double-energy weighted centering localization method to determine the position of the interaction point on the crystal cross-section. The interaction depth DOI is determined by the cross-sectional position and energy ratio, thereby eliminating nonlinearity and edge effects at both ends of the crystal DOI and improving DOI resolution. A dual-ended readout detector structure is employed, consisting of a crystal optically coupled to multiple small-sized SiPMs. Distributed energy values ​​at multiple locations on both ends of the crystal are collected for the first-level energy weighted centering localization. The sum of the energy values ​​at each end and the first-level position can be used for the second-level energy weighted centering localization to determine the position of the interaction point on the crystal cross-section. The dual-ended energy ratio is obtained from the sum of the energy values ​​at each end. A physical simulation model of the gamma photon incident crystal is established, and a discrete mapping of a three-dimensional LUT lookup table is established based on the simulation model between the cross-sectional position, energy ratio, and DOI.

[0074] The depth information correction method and system for the PET detector proposed in this application employs: (1) a dual-end readout detector structure optically coupled to a crystal and multiple small-sized SiPMs, acquiring distributed energy values ​​at multiple locations from the two end faces of the crystal. (2) a double-energy weighted centroid positioning method to determine the position of the interaction point on the crystal cross-section, and the first-level energy weighted centroid positioning method to locate the centroid coordinates of the two end faces A and B. and (3) The interaction depth z is determined by using the interaction point at the position (x,y) of the crystal cross-section and the energy ratio R at both ends of the crystal to look up a table and map the real physical model, thereby eliminating the nonlinearity and edge effect of the DOI at both ends of the crystal and improving the DOI resolution. (4) The distributed energy values ​​at multiple positions are collected from the two end faces of the crystal and used for the first energy weighting centering location. The energy of each end face and the first position can be used for the second energy weighting centering location to determine the position of the interaction point at the crystal cross-section. (5) A physical simulation model of gamma photon incident crystal is established, and a discrete mapping of a three-dimensional LUT lookup table is established between the cross-section position, energy ratio, and DOI according to the simulation model. (6) The method of using small-size SiPM is adopted to reduce the equivalent capacitance effect, so as to achieve a steeper rising edge of the SiPM signal, a smaller amplitude time wander of over-threshold triggering, and a smaller time dispersion, thereby improving the CRT time resolution.

[0075] Figure 7 A block diagram of a depth information correction system in a PET detector provided for another embodiment of this application.

[0076] This specification provides a depth information correction system 700 for a PET detector. Please refer to [link / reference]. Figure 7 The PET detector consists of a crystal and a photodetector. The crystal is used to receive photons and convert them into light signals, and the photodetector converts the light signals into electrical signals for imaging. The crystal includes a first end and a second end. The first end is provided with a first photodetector unit, and the second end is provided with a second photodetector unit. The depth information correction system 700 in the PET detector includes: an acquisition module 710, a first determination module 720, a second determination module 730, and an acquisition module 740.

[0077] The acquisition module 710 is used to acquire first energy data of the electrical signal of the first photoelectric detection unit and second energy data of the electrical signal of the second photoelectric detection unit, and determine the energy ratio based on the first energy data and the second energy data; The first determining module 720 is used to perform first energy weighted center positioning based on the position data and first energy data of the first photoelectric detection unit, and to determine the first energy centroid data of the first end; and to perform first energy weighted center positioning based on the position data and second energy data of the second photoelectric detection unit, and to determine the second energy centroid data of the second end. The second determining module 730 is used to perform second energy weighted center positioning based on the first energy data, the second energy data, the first energy centroid data and the second energy centroid data, and to determine the cross-sectional position data corresponding to the photon interaction point in the crystal. Module 740 is used to determine the interaction depth of a crystal based on cross-sectional position data and energy ratio.

[0078] For example, the first photoelectric detection unit includes a plurality of first coupling units arranged in an array; the first determination module 720 is further configured to calculate the sum of the first energy data of the plurality of first coupling units as the total energy of the first end; multiply the position data of each first coupling unit by its corresponding first energy data and then sum them to obtain the weighted energy sum of the first end; and use the ratio of the weighted energy sum of the first end to the total energy of the first end as the first energy centroid data.

[0079] For example, the second photoelectric detection unit includes a plurality of second coupling units arranged in an array; the first determining module 720 is further configured to calculate the sum of the second energy data of the plurality of second coupling units as the total energy of the second end; multiply the position data of each second coupling unit by its corresponding second energy data and then sum them to obtain the weighted energy sum of the second end; and use the ratio of the weighted energy sum of the second end to the total energy of the second end as the second energy centroid data.

[0080] For example, the second determining module 730 is further configured to determine a first energy product based on the first energy data and the first energy center of gravity data; determine a second energy product based on the second energy data and the second energy center of gravity data; determine an energy sum based on the first energy data and the second energy data; determine the sum of the first energy product and the second energy product; and determine cross-sectional position data based on the ratio between the sum and the energy sum.

[0081] For example, the direction from the first end to the second end is the crystal length direction, the cross-sectional position data is located between the first end and the second end, and the cross-sectional position data is perpendicular to the crystal length direction.

[0082] For example, the first photoelectric detection unit includes a plurality of first coupling units, and the second photoelectric detection unit includes a plurality of second coupling units, with each of the plurality of first coupling units corresponding to one of the plurality of second coupling units.

[0083] For example, the first photoelectric detection unit includes a plurality of first coupling units, the second photoelectric detection unit includes a plurality of second coupling units, the plurality of first coupling units are arranged in an array at the first end, and the plurality of second coupling units are arranged in an array at the second end.

[0084] For example, the cross-sectional position data is located in the plane formed by the x-axis and y-axis, and the cross-sectional position data includes x-axis data and y-axis data; the obtaining module 740 is also used to determine the index data corresponding to the x-axis data, y-axis data and energy ratio; and to perform mapping processing on the lookup table based on the index data to obtain the interaction depth of the crystal.

[0085] For example, the lookup table is constructed as follows: a physical simulation model of the PET detector is established, wherein the physical simulation model includes a crystal and a photodetector; the physical simulation model is subjected to N photon incident events to obtain the first simulated energy data of the electrical signal of the first photodetector unit, the second simulated energy data of the electrical signal of the second photodetector unit, the x-axis simulation data, the y-axis simulation data, the simulated energy ratio, and the simulated interaction depth; based on the x-axis simulation data and the y-axis simulation data, the maximum x-axis position data, the minimum x-axis position data, the maximum y-axis position data, and the minimum y-axis position data are determined, and based on the simulated energy ratio, the maximum energy ratio and the minimum energy ratio are determined; the x-axis simulation data, the y-axis simulation data, and the simulated energy ratio are meshed to determine the corresponding index data; and the lookup table is obtained based on the index data and the simulated interaction depth.

[0086] Exemplarily, the simulation data along the x-axis, the simulation data along the y-axis, and the simulation energy ratio are meshed to determine the corresponding index data, including: obtaining first interval data based on the maximum and minimum x-axis position data; obtaining second interval data based on the maximum and minimum y-axis position data; obtaining third interval data based on the maximum and minimum energy ratios; meshing the x-axis simulation data based on the first interval data to obtain first index data; meshing the y-axis simulation data based on the second interval data to obtain second index data; and meshing the simulation energy ratio based on the third interval data to obtain third index data; and finally, obtaining index data based on the first, second, and third index data.

[0087] Figure 8 A block diagram of an electronic device provided for another embodiment of this application.

[0088] Another embodiment of this application provides an electronic device having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of any of the above embodiments.

[0089] like Figure 8 As shown, for ease of understanding, embodiments of this application illustrate a specific electronic device 800.

[0090] Electronic device 800 is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic device may also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present disclosure described and / or claimed herein.

[0091] like Figure 8 As shown, the electronic device 800 includes a computing unit 801, which can perform various appropriate actions and processes based on a computer program stored in a read-only memory (ROM) 802 or a computer program loaded from a storage unit 808 into a random access memory (RAM) 803. The RAM 803 may also store various programs and data required for the operation of the electronic device 800. The computing unit 801, ROM 802, and RAM 803 are interconnected via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0092] Multiple components in electronic device 800 are connected to input / output (I / O) interface 805. These components include: input unit 806, such as a keyboard or mouse; output unit 807, such as various types of displays or speakers; storage unit 808, such as a disk or optical disk; and communication unit 809, such as a network interface card (NIC), modem, or wireless transceiver. Communication unit 809 allows electronic device 800 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0093] The computing unit 801 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 801 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 801 performs the various methods described above. For example, in some embodiments, any one or more of the various methods described above can be implemented as a computer software program tangibly contained in a machine-readable medium, such as storage unit 808. In some embodiments, part or all of the computer program can be loaded and / or installed on the electronic device 800 via ROM 802 and / or communication unit 809. When the computer program is loaded into RAM 803 and executed by the computing unit 801, one or more steps of any one or more of the various methods described above can be performed. Alternatively, in other embodiments, the computing unit 801 can be configured to perform any one or more of the various methods described above by any other suitable means (e.g., by means of firmware).

[0094] This application provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method in any of the above embodiments.

[0095] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this application, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0096] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0097] In the description of this application, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this application, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0098] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0099] Furthermore, the terms "first," "second," etc., used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this application can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this application, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly and specifically defined in the embodiments.

[0100] In this application, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication between two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific implementation.

[0101] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0102] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for depth information correction in a PET detector, characterized in that, The crystal includes a first end and a second end, wherein a first photodetector unit is disposed at the first end and a second photodetector unit is disposed at the second end; the method includes: Acquire first energy data of the electrical signal of the first photoelectric detection unit and second energy data of the electrical signal of the second photoelectric detection unit, and determine the energy ratio based on the first energy data and the second energy data; Based on the position data of the first photoelectric detection unit and the first energy data, a first energy weighted center is located to determine the first energy centroid data of the first end; and based on the position data of the second photoelectric detection unit and the second energy data, a first energy weighted center is located to determine the second energy centroid data of the second end. Based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data, a second energy weighted center is located to determine the cross-sectional position data corresponding to the photon interaction point in the crystal. The interaction depth of the crystal is determined based on the cross-sectional position data and the energy ratio.

2. The method according to claim 1, characterized in that, The first photoelectric detection unit includes multiple first coupling units arranged in an array; the step of performing first energy weighted center positioning based on the position data of the first photoelectric detection unit and the first energy data to determine the first energy centroid data of the first end includes: The sum of the first energy data of multiple first coupling units is calculated as the total energy at the first end; The position data of each first coupling unit is multiplied by its corresponding first energy data and then summed to obtain the first-end weighted energy sum; The ratio of the weighted energy at the first end to the total energy at the first end is used as the first energy centroid data.

3. The method according to claim 1, characterized in that, The second photoelectric detection unit includes multiple second coupling units arranged in an array; the step of performing first energy weighted center positioning based on the position data of the second photoelectric detection unit and the second energy data to determine the second energy centroid data of the second end includes: The sum of the second energy data of multiple second coupling units is calculated as the total energy at the second end; The position data of each second coupling unit is multiplied by its corresponding second energy data and then summed to obtain the second-end weighted energy sum; The ratio of the weighted energy at the second end to the total energy at the second end is used as the second energy centroid data.

4. The method according to claim 1, characterized in that, The step of determining the cross-sectional position data corresponding to the photon interaction point in the crystal by performing second-weighted center localization based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data includes: Based on the first energy data and the first energy centroid data, determine the first energy product; Based on the second energy data and the second energy centroid data, the second energy product is determined; Based on the first energy data and the second energy data, determine the energy and value; The sum of the first energy product and the second energy product is determined, and the cross-sectional position data is determined based on the ratio between the sum and the energy sum value.

5. The method according to claim 1, characterized in that, The direction from the first end to the second end is the crystal length direction, the cross-sectional position data is located between the first end and the second end, and the cross-sectional position data is perpendicular to the crystal length direction.

6. The method according to claim 1, characterized in that, The first photoelectric detection unit includes a plurality of first coupling units, and the second photoelectric detection unit includes a plurality of second coupling units, wherein the plurality of first coupling units correspond one-to-one with the plurality of second coupling units.

7. The method according to claim 1 or 6, characterized in that, The first photoelectric detection unit includes multiple first coupling units, and the second photoelectric detection unit includes multiple second coupling units. The multiple first coupling units are arranged in an array at the first end, and the multiple second coupling units are arranged in an array at the second end.

8. The method according to claim 1, characterized in that, The cross-sectional position data lies in the plane formed by the x-axis and y-axis, and the cross-sectional position data includes x-axis data and y-axis data; determining the interaction depth of the crystal based on the cross-sectional position data and the energy ratio includes: Determine the index data corresponding to the x-axis data, the y-axis data, and the energy ratio; The interaction depth of the crystal is obtained by mapping the lookup table based on the index data.

9. The method according to claim 8, characterized in that, The lookup table is constructed based on the following method: A physical simulation model of the PET detector is established, wherein the physical simulation model includes the crystal and the photodetector; The physical simulation model is subjected to N photon incidents to obtain the first simulated energy data of the electrical signal of the first photoelectric detection unit, the second simulated energy data of the electrical signal of the second photoelectric detection unit, the x-axis simulation data, the y-axis simulation data, the simulated energy ratio, and the simulated interaction depth. Based on the x-axis simulation data and the y-axis simulation data, determine the maximum x-axis position data, the minimum x-axis position data, the maximum y-axis position data, and the minimum y-axis position data; and based on the simulation energy ratio, determine the maximum energy ratio and the minimum energy ratio. The x-axis simulation data, the y-axis simulation data, and the simulation energy ratio are meshed to determine the corresponding index data; The lookup table is obtained based on the index data and the simulation interaction depth.

10. The method according to claim 9, characterized in that, The process of meshing the x-axis simulation data, the y-axis simulation data, and the simulation energy ratio to determine the corresponding index data includes: Based on the maximum x-axis position data and the minimum x-axis position data, the first interval data is obtained; Based on the maximum y-axis position data and the minimum y-axis position data, the second interval data is obtained; Based on the maximum energy ratio and the minimum energy ratio, the third interval data is obtained; The simulation data of the x-axis is divided into a grid based on the first interval data to obtain the first index data; the simulation data of the y-axis is divided into a grid based on the second interval data to obtain the second index data; and the simulation energy ratio is divided into a grid based on the third interval data to obtain the third index data. Based on the first index data, the second index data, and the third index data, index data is obtained.

11. A depth information correction system for a PET detector, characterized in that, The crystal includes a first end and a second end, wherein a first photodetector unit is disposed at the first end and a second photodetector unit is disposed at the second end; the system includes: The acquisition module is used to acquire first energy data of the electrical signal of the first photoelectric detection unit and second energy data of the electrical signal of the second photoelectric detection unit, and determine the energy ratio based on the first energy data and the second energy data; The first determining module is used to perform a first energy weighted center positioning based on the position data of the first photoelectric detection unit and the first energy data to determine the first energy centroid data of the first end, and to perform a first energy weighted center positioning based on the position data of the second photoelectric detection unit and the second energy data to determine the second energy centroid data of the second end. The second determining module is used to perform second energy weighted center positioning based on the first energy data, the second energy data, the first energy centroid data, and the second energy centroid data, and to determine the cross-sectional position data corresponding to the photon interaction point in the crystal. The module is used to determine the interaction depth of the crystal based on the cross-sectional position data and the energy ratio.

12. An electronic device having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-10.

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