Time correction method, device, equipment and computer-readable storage medium

Abstract

The present application discloses a time correction method, apparatus, device, and computer-readable storage medium. The time correction method includes: based on the sampling data of the target object, obtaining the response line passing through the target object and the coincident events on each response line; based on all the coincident events of all the response lines passing through the target object, obtaining an activity image, and obtaining the pixel points where each response line passing through the target object intersects with the activity image, and obtaining the pixel value-time difference statistical distribution corresponding to each response line based on the pixel points; based on the coincident events on each response line, obtaining the coincident event-time difference statistical distribution corresponding to each response line; calculating the maximum value of the inner product of each pixel value-time difference statistical distribution and the coincident event-time difference statistical distribution, obtaining the difference between the time deviation corresponding to each response line and the maximum value; and obtaining a time correction value based on the difference. The present application has wide applicability and does not require long-term sampling, saving time and improving time correction efficiency.

Description

Technical Field

[0001] The present application relates to the field of data processing, and in particular to a time correction method, apparatus, device, and computer-readable storage medium. Background Art

[0002] Positron Emission Tomography (PET) technology is one of the most advanced molecular imaging technologies in the world. It can non-invasively, quantitatively and dynamically evaluate the metabolic levels, biochemical reactions and functional activities of various functional organs in the body by imaging compounds labeled with radionuclides in the body with high sensitivity and accuracy.

[0003] To monitor the distribution of positron-emitting radionuclides in the human body, the PET system uses the following detection principle: A positron decays to produce a positron, which annihilates with surrounding negative electrons, generating a pair of gamma photons traveling in opposite directions, each with an energy of 511 keV. If two gamma photons are detected by two scintillator bars in the PET detector, the line connecting the centers of the two bars is called a Line of Response (LOR). If two scintillator bars in the detector, located on the LOR, each detect two gamma photons within a specified coincidence time window (e.g., 0 to 15 nanoseconds), meaning the difference in the timing of the two gamma photons falls within the coincidence time window and the energies of both gamma photons fall within the coincidence energy window, then the detection of both gamma photons is called a coincidence event, while the detection of either gamma photon is called a single event.

[0004] like Figure 1 Assuming that the two gamma photons produced by the annihilation event are detected by point A (scintillation crystal bar A) and point B (scintillation crystal bar B) of the PET detector respectively, the line connecting AB is called a response line (LOR).

[0005] Theoretically, if the times tA and tB when the two scintillating crystal bars A and B of the detector detect the gamma photon are accurate enough, the location D where the annihilation occurred can be precisely located. Let the length of AB be L, the distance between point D and point A be d, and the speed of light be C, then d = L / 2 + C / 2 * (tA - tB). In other words, the location of the nuclide annihilation can be directly calculated by collecting the precise arrival time of the gamma photon, eliminating the need for complex image reconstruction methods to obtain PET images.

[0006] However, in actual systems, due to differences in the material, optical path length, and electronic delays of the detector's individual scintillator bars, the bars experience background delay, or time offset. This results in the actual detection times of points A and B being tA' and tB'. Assuming tA' = tA + δA and tB' = tB + δB, δA and δB are the time offsets between scintillator bars A and B, respectively. Due to this time offset, the distance from point A to the radionuclide annihilation location calculated based on tA' and tB' is d' = L / 2 + C / 2*(tA' - tB') = d+C / 2*(δA - δB), and d = d' - C / 2*(δA - δB) = L / 2 + C / 2*(tA' - tB') - C / 2*(δA - δB). This means that the obtained radionuclide annihilation location deviates from the actual annihilation location, D.

[0007] In order to obtain the accurate annihilation position, the time data detected by the scintillation crystal needs to be time corrected.

[0008] Typically, the deviations δ1 to δn between the actual measured time values ​​of all n scintillation crystal bars in the detector and the theoretical arrival time of γ photons are obtained, and the obtained deviations are corrected to the actual collected time information. This process is called time deviation correction, that is, time correction of scintillation crystals. Therefore, the most important task in the time correction process is to obtain the deviations δ1 to δn between the actual measured time values ​​of all scintillation crystal bars and the theoretical arrival time of γ photons.

[0009] In the time correction method in the prior art, in order to obtain the deviation δ1~δn between the actual measured time value of the scintillation crystal bar and the theoretical arrival time of the gamma photon, it is necessary to characterize the time deviation of the scintillation crystal bars at both ends of the LOR. At present, the time deviation of the scintillation crystal bars at both ends of the LOR is usually characterized based on the time difference of the coincident event corresponding to a certain LOR. However, in theory, for gamma rays emitted by different target objects, when characterizing the difference in the time deviation of the scintillation crystal bars at both ends of the LOR, the method of obtaining the mean time difference of the coincident event corresponding to the LOR is different, and various methods are not universal for different target objects. For example: when using a uniform target object of a specific shape (such as a small cylinder or a line source), the sum mean of the time differences of all the coincident events on the LOR can be used as the mean time difference of the coincident event corresponding to the LOR; for the currently used annular target object In the case of a target object (such as a shell source or a line source rotated once to form a target object similar to a shell source), when the activity and shape of the target object are uniform, the summed mean of the time differences of all the coincident events on the LOR can be used as the time difference mean of the coincident events corresponding to the LOR; when the activity and shape of the target object are uneven, the summed mean of the time differences of all the coincident events on the LOR cannot be used as the time difference mean of the coincident events corresponding to the LOR. Usually, the summed mean of the time differences of the coincident events corresponding to each annihilation position is obtained by high-speed fitting as the time difference mean of the coincident events corresponding to the LOR; the Gaussian fitting method requires collecting enough counts of the target object, which requires a long time to collect, at least 1 hour, and is time-consuming; or it requires a very high drug activity, but high drug activity will lead to more random events and increase measurement errors.

[0010] In summary, the current time correction method has the following defects when characterizing the time deviation difference between the scintillator crystal bars at both ends of the LOR in order to obtain the deviation δ1~δn between the actual measured time value of the scintillator crystal bar and the theoretical arrival time of the gamma photons: the method for characterizing the time deviation difference between the scintillator crystal bars at both ends of the LOR is different for the gamma rays emitted by different target objects, and the various methods are not universal. There is no unified method for characterizing the time deviation difference between the scintillator crystal bars at both ends of the LOR, and some methods are too time-consuming and the results are prone to large errors.

[0011] The content of this background technology description is only for facilitating understanding of the relevant technology in this field and is not regarded as an admission of the prior art. Summary of the Invention

[0012] Therefore, the present application intends to provide a time correction method, apparatus, device and computer-readable storage medium, which can solve at least one problem existing in the prior art.

[0013] According to a first aspect of the present application, a time correction method is provided, comprising: based on sampling data of a target object, obtaining a response line LORi passing through the target object and a coincident event Ki on each response line LORi, wherein i represents the number, i≥1; based on all coincident events of all LORi passing through the target object, obtaining an activity image, and obtaining pixel points Pi where each LORi passing through the target object intersects with the activity image, and obtaining a pixel value-time difference statistical distribution Ti corresponding to each response line LORi based on the pixel points Pi; based on the coincident event Ki on each response line LORi, obtaining a coincident event-time difference statistical distribution Mi corresponding to each response line LORi; based on the pixel value-time difference statistical distribution Ti and the coincident event-time difference statistical distribution Mi, calculating the maximum value Yi of the inner product of each pixel value-time difference statistical distribution Ti and the coincident event-time difference statistical distribution Mi, and obtaining a difference δ of the time deviation corresponding to each response line LORi and the maximum value Yi. △ i; based on the difference δ △ iGet the time correction value.

[0014] According to one embodiment of the present application, the response line LORi passing through the target object includes: the response line LORi and the target object have at least one intersection point, or the response line LORi is tangent to or intersects with the target object.

[0015] According to one embodiment of the present application, based on the sampling data, the response lines LORi (i≥1) passing through the target object and the matching events Ki on each response line LORi are obtained, including: obtaining all matching events and the response lines LOR corresponding to each matching event based on the sampling data; screening all response lines LORi passing through the target object and the matching events Ki on each response line LORi.

[0016] According to one embodiment of the present application, screening all response lines LORi passing through the target object and the matching events Ki on each response line LORi includes: determining whether the straight line where the response line LOR is located intersects the target object based on prior information.

[0017] According to one embodiment of the present application, the prior information includes the IP number of the scintillation crystals spaced between the scintillation crystals at both ends of the response line LOR. The IP number of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the straight line where the response line LOR is located.

[0018] According to one embodiment of the present application, an activity image is acquired based on all coincident events of all response lines LORi passing through the target object, including: reconstructing the activity image using filtered back projection or an iterative method based on all coincident events of all response lines LORi passing through the target object.

[0019] According to one embodiment of the present application, obtaining each pixel point Pi where each response line LORi passing through the target object intersects with the activity image includes: obtaining the pixel point Pi where each selected response line LORi intersects with the activity image based on a ray tracing method.

[0020] According to one of the embodiments of the present application, the pixel value-time difference statistical distribution Ti corresponding to each response line LORi is obtained based on the pixel point Pi, including: calculating the time difference from the pixel point Pi to the two end points of the corresponding response line LORi one by one, and recording the pixel value of each pixel point Pi; determining a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pi, calculating the cumulative value of the pixel value of the pixel point Pi whose time difference falls into each time difference interval; using the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis, obtaining the pixel value-time difference statistical distribution Ti corresponding to each response line LORi.

[0021] According to one of the embodiments of the present application, based on the conforming events Ki on each response line LORi, the conforming event-time difference statistical distribution Mi corresponding to each response line LORi is obtained, including: determining the horizontal axis with the horizontal axis step size of the pixel value-time difference statistical distribution Ti as the step size, and using the cumulative value of the conforming events whose time difference falls into each step size as the vertical axis to obtain the conforming event-time difference statistical distribution Mi corresponding to each response line LORi.

[0022] According to one embodiment of the present application, the maximum value Yi of the inner product of each pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi is calculated, and the difference δ of the time deviation corresponding to each response line LORi and the maximum value is obtained. △ i, including: taking the pixel value-time difference statistical distribution Ti as the benchmark, translating the event-time difference statistical distribution Mi, calculating the inner product of the pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi, and obtaining the maximum value Yi of the inner product, which is the translation amount of the event-time difference statistical distribution Mi. The translation amount is the difference δ △ i.

[0023] According to one embodiment of the present application, based on the time deviation difference δ △ i Obtain the time correction value, including: the difference δ based on the time deviation △ i. Obtain the relationship between the time deviations δci and δdi of the scintillator crystals ci and di at both ends of each response line LORi, δci-δdi=δ △ i; a set of simultaneous equations, and the time deviations δci and δdi of the scintillation crystals ci and di at both ends of each response line LORi are obtained by fitting method. The time deviations δci and δdi are the time correction values ​​of the scintillation crystals ci and di.

[0024] According to one embodiment of the present application, the time correction method further includes: performing time correction on the sampled data based on the acquired time correction value, that is: correcting the time data corresponding to the scintillation crystals ci and di in the sampled data based on the time deviations δci and δdi of the scintillation crystals ci and di.

[0025] According to one embodiment of the present application, the time data corresponding to the scintillation crystals ci and di in the sampled data is corrected, including: correcting the time data t corresponding to the scintillation crystals ci and di in the sampled data ci , t di Subtract the time correction values ​​δci and δdi respectively.

[0026] According to a second aspect of the present application, a time correction method is provided, comprising: based on sampling data of a target object, obtaining a response line LORi passing through the target object and a coincident event Ki on each response line LORi, wherein i represents the number, i≥1; obtaining an activity image based on all the coincident events of all response lines LORi passing through the target object; based on all the response lines LORi passing through the target object, screening response lines LORj whose number of coincident events meets a preset condition, wherein j represents the number, j≥1; obtaining pixel points Pj where each screened response line LORj intersects with the activity image, and obtaining a pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel points Pj; obtaining a coincident event-time difference statistical distribution Mj corresponding to each screened response line LORj; and calculating a maximum value Yj of an inner product of each pixel value-time difference statistical distribution Tj and a coincident event-time difference statistical distribution Mj based on the pixel value time difference statistical distribution Tj corresponding to each screened response line LORj and the coincident event-time difference statistical distribution Mj, and obtaining a difference δ of a time deviation corresponding to each response line LORj and the maximum value. △ j; based on the difference δ △ jGet the time correction value.

[0027] According to one embodiment of the present application, the response line LORi passing through the target object includes: the response line LORi and the target object have at least one intersection point, or the response line LORi is tangent to or intersects with the target object.

[0028] According to one embodiment of the present application, based on the sampling data, the response lines LORi passing through the target object and the matching events Ki on each response line LORi are obtained, including: obtaining all matching events and the response lines LOR corresponding to each matching event based on the sampling data; screening all response lines LORi passing through the target object and the matching events Ki on each response line LORi.

[0029] According to one embodiment of the present application, screening all response lines LORi passing through the target object and the matching events Ki on each response line LORi includes: determining whether the straight line where the response line LOR is located intersects the target object based on prior information.

[0030] According to one embodiment of the present application, the prior information includes the IP number of the scintillation crystals spaced between the scintillation crystals at both ends of the LOR. The IP number of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the line of response LOR.

[0031] According to one embodiment of the present application, an activity image is acquired based on all coincident events of all response lines LORi passing through the target object, including: reconstructing the activity image using filtered back projection or an iterative method based on all coincident events of all response lines LORi passing through the target object.

[0032] According to one embodiment of the present application, based on all response lines LORi passing through the target object, the response line LORj whose number of matching events meets the preset conditions is screened, including: setting a benchmark value for comparing the number of matching events; determining whether the number of matching events is greater than the benchmark value; and storing the LOR whose number of matching events is greater than the benchmark value.

[0033] According to one embodiment of the present application, obtaining the pixel points Pj where each screened response line LORj intersects with the activity image includes: obtaining the pixel points Pj where each screened response line LORj intersects with the activity image based on a ray tracing method.

[0034] According to one of the embodiments of the present application, the pixel value-time difference statistical distribution Tj corresponding to each response line LORj is obtained based on the pixel point Pj, including: calculating the time difference from the pixel point Pj to the two end points of the corresponding response line LORj one by one, and recording the pixel value of each pixel point Pj; determining a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculating the cumulative value of the pixel value of the pixel point Pj whose time difference falls into each time difference interval; using the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis, obtaining the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

[0035] According to one of the embodiments of the present application, the statistical distribution Mj of the matching events-time differences corresponding to each screened response line LORj is obtained, including: determining the horizontal axis with the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and using the cumulative value of the matching events whose time differences fall into each step size as the vertical axis, to obtain the statistical distribution Mj of the matching events-time differences corresponding to each response line LORj.

[0036] According to one embodiment of the present application, the maximum value Yj of the inner product of each pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj is calculated, and the difference δ between each LORj and the time deviation corresponding to the maximum value is obtained. △ j, including: taking the pixel value-time difference statistical distribution Tj as the benchmark, translating the event-time difference statistical distribution Mj, calculating the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and statistically obtaining the maximum value Yj when the event-time difference statistical distribution Mj is in compliance with the translation amount, which is the difference δ △ j.

[0037] According to one embodiment of the present application, based on the difference δ △ j obtains the time correction value, including: based on the difference δ △ j, and obtain the relationship between the time deviations δcj and δdj of the scintillator crystals cj and dj at both ends of each response line LORj. δcj-δdj=δ △ j; a set of simultaneous equations, and the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each LORj are obtained by fitting method. The time deviations δcj and δdj are the time correction values ​​of the scintillation crystals cj and dj.

[0038] According to one embodiment of the present application, the time correction method further includes: performing time correction on the sampled data based on the acquired time correction value, that is, correcting the time data corresponding to the scintillation crystals cj and dj in the sampled data based on the time deviations δcj and δdj of the scintillation crystals cj and dj.

[0039] According to one embodiment of the present application, the time data corresponding to the scintillation crystals cj and dj in the sampled data is corrected, including: correcting the time data t corresponding to the scintillation crystals cj and dj in the sampled data cj , t dj Subtract the time correction values ​​δcj and δdj respectively.

[0040] According to a third aspect of the present application, a time correction device is provided, comprising: a coincidence event screening module configured to obtain, based on sampling data of the target object, response lines LORi passing through the target object and coincidence events Ki on each response line LORi, wherein i represents the number, i≥1; an activity image reconstruction module configured to obtain an activity image based on all coincidence events of all response lines LORi passing through the target object; a pixel value-time difference statistical distribution acquisition module configured to obtain each pixel point Pi where each response line LORi passing through the target object intersects with the activity image, and obtain, based on the pixel point Pi, a pixel value-time difference statistical distribution Ti corresponding to each response line LORi; a coincidence event-time difference statistical distribution acquisition module configured to obtain a coincidence event-time difference statistical distribution Mi corresponding to each response line LORi; and a calculation module configured to calculate the maximum value Yi of the inner product of each pixel value-time difference statistical distribution Ti and the coincidence event-time difference statistical distribution Mi, and obtain a difference δ of the time deviation corresponding to each response line LORi and the maximum value. △ i; time correction value acquisition module, configured based on the difference δ △ iGet the time correction value.

[0041] According to one embodiment of the present application, the sampling data includes scintillation crystal number information and time information of the pulse signal; the coincidence event screening module is further configured to obtain energy information of the pulse signal based on the sampling data, and obtain coincidence events based on the time information and energy information of the pulse signal, and obtain the response line LOR corresponding to the coincidence event based on the scintillation crystal number information.

[0042] According to one embodiment of the present application, the time correction device further includes: a recording module configured to record the time difference corresponding to the event and the corresponding scintillation crystal number information at both ends of the response line LOR.

[0043] According to one embodiment of the present application, the coincidence event screening module is further configured to determine whether the line where the response line LOR is located has an intersection with the target object based on prior information, and determine whether the response line LOR passes through the target object based on the number of intersections.

[0044] According to one embodiment of the present application, the prior information includes the IP number of the scintillation crystals spaced between the scintillation crystals at both ends of the response line LOR. The IP number of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the straight line where the response line LOR is located.

[0045] According to one embodiment of the present application, the activity image reconstruction module is configured to reconstruct the activity image using filtered back projection or an iterative method.

[0046] According to one embodiment of the present application, the pixel value-time difference statistical distribution acquisition module is configured to acquire the pixel points Pi where the selected response lines LORi intersect with the activity image based on a ray tracing method.

[0047] According to one of the embodiments of the present application, the pixel value-time difference statistical distribution acquisition module includes: a pixel point time difference acquisition module, which is used to calculate the time difference from the pixel point Pi to the two end points of the corresponding response line LORi one by one, and record the pixel value of each pixel point Pi; a pixel value accumulation module, which is used to determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pi, calculate the cumulative value of the pixel value of the pixel point Pi whose time difference falls into each time difference interval; the pixel value-time difference statistical distribution acquisition module is configured to use the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis to obtain the pixel value-time difference statistical distribution Ti corresponding to each response line LORi.

[0048] According to one of the embodiments of the present application, the module for obtaining the statistical distribution of coincident events and time differences is configured as follows: the horizontal axis is determined by taking the horizontal axis step size of the pixel value-time difference statistical distribution Ti as the step size, and the vertical axis is determined by taking the cumulative value of coincident events whose time differences fall into each step size as the vertical axis, and obtaining the statistical distribution Mi of coincident events and time differences corresponding to each response line LORi.

[0049] According to one embodiment of the present application, the time correction value acquisition module is further configured to calculate the time correction value based on the time deviation difference δ △ i Obtain the relationship between the time deviations δci and δdi of the scintillator crystals ci and di at both ends of each response line LORi, δci-δdi=δ △ i; simultaneous equations and obtain the time deviations δci and δdi of the scintillation crystals ci and di at both ends of each response line LORi by fitting method. The time deviations δci and δdi are the time correction values ​​of the scintillation crystals ci and di.

[0050] According to one embodiment of the present application, the time correction device further includes a correction module, which is configured to correct the pulse signal time information in the sampled data based on the time correction value: the time data t corresponding to the scintillation crystals ci and di in the sampled data ci , t di Subtract the time correction values ​​δci and δdi respectively.

[0051] According to a fourth aspect of the present application, a time correction device is provided, comprising: a first coincidence event screening module configured to obtain, based on sampling data of the target object, a response line LORi passing through the target object and a coincidence event Ki on each response line LORi, where i represents the number, i ≥ 1; an activity image reconstruction module configured to obtain an activity image based on all coincidence events of all response lines LORi passing through the target object; and a second coincidence event screening module configured to screen, based on all response lines LORi passing through the target object, a response line LORj whose number of coincidence events meets a preset reference value, where j represents the number, j ≥ 1. 1; a pixel value-time difference statistical distribution acquisition module, configured to acquire each pixel point Pj where each selected response line LORj intersects with the activity image, and based on the pixel point Pj, respectively acquire the pixel value-time difference statistical distribution Tj corresponding to each response line LORj; a consistent event-time difference statistical distribution acquisition module, configured to acquire the consistent event-time difference statistical distribution Mj corresponding to each selected response line LORj; a calculation module, configured to calculate the maximum value Yj of the inner product of each pixel value-time difference statistical distribution Tj and the consistent event-time difference statistical distribution Mj, and acquire the difference δ of the time deviation corresponding to each response line LORj and the maximum value △ j; time correction value acquisition module, configured based on the difference δ △ jGet the time correction value.

[0052] According to one embodiment of the present application, the sampling data includes scintillation crystal number information and time information of the pulse signal; the coincidence event screening module is further configured to obtain energy information of the pulse signal based on the sampling data, and obtain coincidence events based on the time information and energy information of the pulse signal, and obtain the LOR corresponding to the coincidence event based on the scintillation crystal number information.

[0053] According to one embodiment of the present application, the time correction device further includes: a recording module configured to record the time difference corresponding to the event and the corresponding scintillation crystal number information at both ends of the response line LOR.

[0054] According to one embodiment of the present application, the first coincidence event screening module is configured to determine whether the line where the response line LOR is located has an intersection with the target object based on prior information, and determine whether the response line LOR passes through the target object based on the number of intersections.

[0055] According to one embodiment of the present application, the prior information includes the IP number of the scintillation crystals spaced between the scintillation crystals at both ends of the response line LOR. The IP number of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the straight line where the response line LOR is located.

[0056] According to one embodiment of the present application, the activity image reconstruction module is configured to reconstruct the activity image using filtered back projection or an iterative method.

[0057] According to one embodiment of the present application, the second conforming event screening module includes: a reference value setting module, used to set a reference value for comparing the number of conforming events; a determination module, used to determine whether the number of conforming events is greater than the reference value; and a storage module, used to store a response line LOR when the number of conforming events is greater than the reference value.

[0058] According to one embodiment of the present application, the pixel value-time difference statistical distribution acquisition module is configured to acquire the pixel point Pj where the selected response line LORj intersects the activity image based on a ray tracing method.

[0059] According to one of the embodiments of the present application, the pixel value-time difference statistical distribution acquisition module includes: a pixel point time difference acquisition module, which is used to calculate the time difference from the pixel point Pj to the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj; a pixel value accumulation module, which is used to determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculate the accumulated value of the pixel value of the pixel point Pj whose time difference falls into each time difference interval; the pixel value-time difference statistical distribution acquisition module is configured to use the time difference interval as the horizontal axis step size and the accumulated value of the pixel value of the pixel points falling into each step size as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

[0060] According to one of the embodiments of the present application, the module for obtaining the statistical distribution of coincident events-time differences is configured to determine the horizontal axis with the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and to determine the vertical axis with the cumulative value of coincident events whose time differences fall into each step size, so as to obtain the statistical distribution Mj of coincident events-time differences corresponding to each response line LORj.

[0061] According to one embodiment of the present application, the time correction value acquisition module is further configured to calculate the time correction value based on the time deviation difference δ △ The relationship between the time deviations δcj and δdj of the scintillator crystals cj and dj at both ends of each response line LORj is obtained by the formula δcj-δdj=δ △ j; the simultaneous equations and the fitting method are used to obtain the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj. The time deviations δcj and δdj are the time correction values ​​of the scintillation crystals cj and dj.

[0062] According to one embodiment of the present application, the time correction device further includes a correction module, which is configured to correct the time information of the pulse signal in the sampled data based on the time correction value: the time data t corresponding to the scintillation crystals cj and dj in the sampled data cj, t dj Subtract the time correction values ​​δcj and δdj respectively.

[0063] According to the fifth aspect of the present application, a digitization device is provided, comprising the time correction device as described above, wherein the digitization device uses a detector to detect an object to be detected, uses a sampling module to obtain sampling data, uses a time correction device to correct the sampling data and obtains corrected time data, thereby forming a digitized image based on the corrected time data.

[0064] According to the sixth aspect of the present application, a computer device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the steps of the time correction method described above are implemented.

[0065] According to a seventh aspect of the present application, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the time correction method described above are implemented.

[0066] The solution of the embodiment of the present application obtains the pixel value-time difference statistical distribution Ti and the coincidence event-time difference statistical distribution Mi corresponding to each response line LORi based on the true coincidence events passing through the target object, and calculates the maximum value Yi of the inner product of each Ti and Mi, and obtains the difference δ of the time deviation corresponding to each response line LORi and the maximum value △ i, then based on δ △ i obtains time correction values, which is applicable to any shell source, has wide applicability, and does not require Gaussian fitting, so it does not require long-term sampling, saving time and improving time correction efficiency.

[0067] In addition, since the embodiment of the present application is based on the true coincidence events corresponding to the response lines LORj that pass through the target object and whose number of coincidence events meets the preset conditions, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj are obtained, random events and scattered events are further discarded, and the difference δ of the time deviation corresponding to each response line LORj is further improved accordingly. △ j, thereby further improving the accuracy of time correction.

[0068] The optional features and other effects of the embodiments of the present application are partially described below, and partially can be understood by reading this document. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The embodiments of the present application are described in detail with reference to the accompanying drawings. The elements shown are not limited to the scale shown in the drawings. The same or similar reference numerals in the drawings represent the same or similar elements, wherein:

[0070] Figure 1 shows a schematic diagram of annihilation position deviation according to the prior art;

[0071] Figure 2 A flow chart of a time correction method according to an embodiment of the present application is shown;

[0072] Figure 3 shows a flow chart of a time correction method according to another embodiment of the present application;

[0073] Figure 4 An exemplary module diagram of a time correction device according to an embodiment of the present application is shown;

[0074] Figure 5 An exemplary module diagram of a time correction device according to another embodiment of the present application is shown. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0076] As used herein, the term "including" and its variations represent open inclusion, i.e., "including but not limited to." Unless otherwise stated, the term "or" means "and / or." The term "based on" means "based at least in part on." The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment." The term "another embodiment" means "at least one additional embodiment." The terms "first," "second," etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0077] Some preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be noted that the following description is for illustrative purposes only and is not intended to limit the scope of protection of the present application.

[0078] Figure 2 is an exemplary flow chart of a time correction method according to some embodiments of the present application. Specifically, Figure 2 As shown, the time correction method may include the following steps S120, S130, S140, S150, and S160.

[0079] Before implementing the method, step S110 may be performed first: sampling the pulse signal obtained based on the target object to obtain sampling data.

[0080] In an embodiment of the present application, the target object may include a prosthesis and / or a biological body, a simulated radiation source. Specifically, the prosthesis and / or biological body includes but is not limited to an animal body; the simulated radiation source includes but is not limited to a small cylinder (the diameter may be less than 20 mm), a line source, a shell source or a radiation source similar to a shell source, etc., and may also be a simulated radiation source with a regular or irregular shape.

[0081] In the embodiments of the present application, the sampled data is interpreted broadly, including detection data obtained from a physical target object and / or generated simulation data.

[0082] In the embodiments of the present application, the detection data may be detection data obtained by detecting a physical object, and the detection data is acquired by a detection module. The detection module may be a detection module in various medical imaging devices such as PET, CT, and MR, and includes a detector, which includes a scintillation crystal and a photoelectric conversion element.

[0083] In one example of the present application, the detection module can be a PET detection module, whose detector includes a scintillation crystal and a photoelectric conversion element. The scintillation crystal includes but is not limited to yttrium lutetium silicate scintillation crystal, which is used to convert gamma rays into visible light, and the photoelectric conversion element includes but is not limited to a silicon photomultiplier (SiPM), which is used to convert visible light into a pulse signal.

[0084] In the embodiments of the present application, the pulse signal should be understood as any pulse signal that can be sampled, and its essence is a physical quantity that undergoes a sudden change in a short period of time and then quickly returns to its initial value, and this physical quantity has certain characteristics. In the present application, the pulse signal especially includes a scintillation pulse, and multiple embodiments will be described herein using a scintillation pulse as an example, in which the pulse signal and the scintillation pulse can be interchangeable. For example, in some embodiments, the scintillation pulse typically has a rising edge and a falling edge, and the rising edge and the falling edge can be represented by a function model. In some embodiments, the pulse signal is a scintillation pulse signal. For example, the scintillation pulse corresponding to a gamma photon typically exhibits a relatively fast rising edge and a relatively slow falling edge, the rising edge can be represented by a linear function, and the falling edge can be represented by an exponential function.

[0085] In other embodiments, the waveform of the pulse signal may be a triangular wave, a rectangular wave, a sine wave, a cosine wave or other shapes of waves, which will not be described in detail here.

[0086] In the embodiment of the present application, the pulse signal is expressed as an electrical pulse signal, and its corresponding characteristics may be the voltage and current of the electrical pulse signal (the Ruishi case is limited to the PET field and electrical pulses).

[0087] In an embodiment of the present application, sampling of a pulse signal obtained based on a radioactive source is implemented through a sampling module. In an example of the present application, the sampling module is a multi-voltage threshold (MVT) sampling module, which performs multi-voltage threshold sampling on the pulse signal. Specifically, the multi-voltage threshold sampling module includes a threshold setting module, a comparison module, a time-to-digital conversion module, and an information storage module. The threshold setting module is used to set the sampling threshold; the comparison module is used to compare the pulse signal with the threshold and output a transition signal; the time-to-digital conversion module is used to perform time sampling on the transition signal to obtain the time information of the pulse signal, and the information storage module stores the scintillation crystal number information of the detection module and the time information of the pulse signal. The sampling of the pulse signal by the MVT sampling module is implemented based on an FPGA chip. The FPGA chip integrates DAC, LVDS, and TDC. The DAC integrated in the FPGA chip is used as a threshold setting module, the LVDS is used as a comparison module, and the TDC is used as a time conversion module. The DAC is used to preset thresholds for LVDS, such as voltage thresholds V1, V2, V3, and V4. The input pulse signal is compared with the LVDS thresholds V1-V4, and sampling is performed at times t1-t4 corresponding to the rising edge of the jump signal, and sampling is performed at times t5-t8 corresponding to the falling edge of the jump signal to obtain sampling data including voltage-time pairs (V1, t1), (V2, t2), (V3, t3), (V4, t4), (V4, t5), (V3, t6), (V2, t7), and (V1, t8), where t1-t8 are time data.

[0088] In the embodiment of the present application, the sampled data includes the scintillation crystal number information of the detection module and the time information of the pulse signal. The time data t1 can represent the time information of the pulse signal, and the scintillation crystal number information of the detection module can be determined based on the time data t1-t4 of the pulse signal.

[0089] In the embodiment of the present application, the voltage-time pairs (V1, t1), (V2, t2), (V3, t3), (V4, t4), (V4, t5), (V3, t6), (V2, t7), and (V1, t8) in the sampled data are subsequently used to fit and restore the pulse waveform. The energy information of the pulse signal is obtained based on the integral of the restored pulse waveform. Subsequently, the matching events are screened based on the time information and energy information of the pulse signal. Based on the LOR of the screened matching events and the time information of the pulse signal, the position information of a single gamma photon event can be determined. It can be seen that the accuracy of the time data affects the screening of matching events and the accuracy of the position information of the single event, that is, the accuracy of the annihilation position.

[0090] In embodiments of the present application, the simulation data may be, for example, data generated by simulation, which may be obtained from simulation software or a simulation module. The simulation software or simulation module may be, for example, simulation software or a simulation module for simulating medical imaging equipment and its detection instruments. The simulation software or simulation module includes a simulation detection module, such as a simulation PET detection module. In a specific example, the sampled data may be obtained from simulation software that uses a simulated PET scan. In some embodiments, the target object may also include a simulated target object.

[0091] In the example of this application, the target object (such as a shell source, a line source, or a cylindrical radioactive source) is placed at the center of the FOV, and sampling is performed using the MVT method. The acquisition time is more than 10 minutes to obtain sampling data.

[0092] Step S120 : Based on the sampling data of the target object, obtain LORi (i≥1) passing through the target object and the matching events Ki (i≥1) on each LORi.

[0093] In one embodiment, step S120 may specifically include:

[0094] S121: Acquire all matching events and the LOR corresponding to each matching event based on the sampled data.

[0095] In the embodiment of the present application, a coincidence event is two single events corresponding to two pulse signals whose time difference (i.e., the difference in the time information of the two pulse signals) is within the coincidence time window and whose energy information is within the coincidence energy window. Specifically, taking the detection of gamma rays using a PET detector as an example, two gamma photons produced by an annihilation reaction are detected by the scintillation crystals of the two detectors. The time information difference of the two gamma photons is within a preset coincidence time window, and the energy information of the two gamma photons is both within the preset coincidence energy window. In this case, the event of detecting these two gamma photons can be called a coincidence event. The coincidence time window and coincidence energy window in the embodiment of the present application can be determined based on prior information.

[0096] In some embodiments, after acquiring sampled data, all matching events and the LOR corresponding to each matching event can be obtained based on the sampled data. Specifically, the sampled data can be transmitted to a host computer, where the pulse waveform can be restored by fitting the sampled data. The restored pulse waveform can then be integrated to obtain the energy information of the pulse signal corresponding to a single event. Simultaneously, the host computer can also determine the scintillation crystal numbering information of the detection module, i.e., the IP number of the scintillation crystal (e.g., the scintillation crystals are numbered 1-n), and the time information of the pulse signal based on the time data of the pulse signal.

[0097] In this embodiment, a coincidence time window and a coincidence energy window are preset in a coincidence module of a host computer. Based on the time and energy information of the pulse signal acquired from the sampled data, a coincidence event is detected for a single event corresponding to the pulse signal. A recording module is also provided in the host computer to record the time difference between the coincidence events and the IP numbers of the two scintillation crystals. The line connecting the centers of the two scintillation crystal surfaces is the LOR corresponding to the coincidence event.

[0098] In one example, the coincidence time window is set to 4 ns and the coincidence energy window is set to 420 keV-1000 keV in the coincidence module of the host computer. If the annihilation reaction produces two gamma photons γ1 and γ2, the host computer knows based on the sampled data that the time information of the pulse signal corresponding to the single event γ1 detected by the scintillation crystal G with IP number 6 (taking the PET detector with 48 scintillation crystals as an example) is t1, and the time information of the pulse signal corresponding to the single event γ2 detected by the scintillation crystal H with IP number 30 is t1', then the time difference is Δt= t1-t1', if △t≤4ns, the time difference between the two single events is within the coincidence time window; the pulse waveforms of the two single events are fitted and restored on the host computer, and the energy information e1 of the γ1 single event and the energy information e2 of the γ2 single event are obtained by integration respectively. If e1 and e2 are both within the range of 420keV-1000keV, the energy information of the two single events is within the coincidence time window. At this time, the γ1 single event and the γ2 single event are a pair of coincidence events, and the line connecting the centers of the G and H surfaces of the scintillation crystal is the LOR corresponding to the coincidence event. GH The recording module of the host computer records the time difference of the coincidence event as Δt=t1-t1', the IP number information of the scintillation crystals G and H as 6 and 30, and the corresponding LOR, i.e., the line connecting the centers of the GH surfaces.

[0099] Similarly, in the embodiment of the present application, all matching events, i.e., corresponding LORs, can be obtained based on the sampled data received by the host computer.

[0100] In one embodiment of the present application, if there are multiple pairs of matching events corresponding to the same LOR, the number of matching events on the LOR and the time difference between the matching events on the LOR are counted. For example, continuing with the above example, if there are 20 pairs of matching events corresponding to the LOR GH , then the LOR is counted GH The event difference information △t1-△t20 of the above 20 pairs of matching events is recorded in the recording module, and the number of matching events 20, the time difference △t1-△t20 of each matching event, the IP number information 6, 30 of the scintillation crystals G and H, and the corresponding LOR, that is, the GH surface center connection line are recorded.

[0101] In the example of this application, the host computer obtains the time information and energy information of all pulse signals based on the sampling data, and filters out all matching events based on the preset matching time window and matching energy window, and records the time difference of all matching events, the scintillation crystal IP number information and the LORs corresponding to all matching events, so as to facilitate the subsequent screening of all LORs passing through the target object (such as a simulated radiation source, etc.) and all matching events corresponding to each LOR.

[0102] S122: Filter all LORi passing through the target object and the matching events Ki on each LORi.

[0103] In an embodiment of the present application, the coincident events obtained in step S121 may include true events, random events, and scattered events. Random events and scattered events will affect the accuracy of the time correction value obtained subsequently and need to be discarded. It will be understood by those skilled in the art that the LORs corresponding to the true events in the coincident events all pass through the target object, that is, they have an intersection with the target object, while the random events and scattered events do not pass through the target object, that is, they have no intersection with the target object. Therefore, in an example of the present application, the coincident events corresponding to the true events can be screened by whether the LORs corresponding to the coincident events pass through the target object.

[0104] In the embodiment of the present application, screening all LORi passing through the target object and the matching events Ki on each LORi can be achieved by determining whether the straight line where the LOR is located intersects the target object. Specifically, the following steps can be included:

[0105] Based on the prior information, the intersection judgment module is used to determine whether the line where the LOR is located intersects with the target object.

[0106] In one embodiment of the present application, the prior information may include the number of IPs of the scintillation crystals spaced between the scintillation crystals of the detection modules at both ends of the LOR. The number of IPs of the spaced scintillation crystals is determined based on whether the target object intersects the straight lines where the LORs are located.

[0107] In one example of the present application, prior information can be obtained based on different target objects. For both regular and irregularly shaped targets, the number of scintillation crystal IPs between the IP numbers of the scintillation crystals at the ends of each LOR where it intersects the target object can be pre-counted. This information can then be used as the prior information, and a lookup table of the prior information can be created for easy reference.

[0108] In one example, regarding the acquisition of prior information of a target object with a regular shape, taking the target object as a simulated radiation source with a cylindrical shape and a diameter less than 20 mm as an example, the LOR is determined by the prior information. GHThe distance f between the straight line and the center point of the cylindrical radiation source. If the distance f is less than or equal to the radius d of the cylindrical radiation source, then the LOR GH The straight line has at least one intersection with the cylindrical radioactive source and passes through the cylindrical radioactive source. If the distance f = d, LOR GH The line circumscribes the cross section of the cylindrical radioactive source. If the IP number of scintillation crystal G is 6, and the IP number of scintillation crystal H is 20, and when f = d, the number of scintillation crystals between scintillation crystals G and H is 14. If this cylindrical simulated radioactive source is used as the target object, if the IP number of the scintillation crystals between the two ends of a LOR is greater than or equal to 14, then the LOR passes through the target object. In this case, the prior information obtained based on this cylindrical simulated radioactive source is: if the IP number of the scintillation crystals between the two ends of the LOR is greater than or equal to 14, then the LOR passes through the target object.

[0109] In one example, assuming a target object uses a regularly shaped shell source with a diameter of 500 mm, and assuming a PET detector with 48 scintillator crystals, if the IPs of the two scintillator crystals corresponding to the ends of an LOR are separated by 12 scintillator crystal IPs, the LOR between the two crystals passes through the center of the shell source and is 0 mm from the center of the shell source. If the two crystals are separated by 9 crystal IPs, then the distance from the center of the shell source to the line connecting the midpoints of the two crystal surfaces is 180 mm, and the LOR between the two crystals passes through the shell source. If the two crystals are separated by 6 crystal IPs, then the distance from the center of the shell source to the line connecting the midpoints of the two crystal surfaces is 250 mm, and the LOR between the two crystals circumscribes the shell source. If the number of scintillator crystal IPs between the two scintillator crystals corresponding to the ends of an LOR is less than 6, then the LOR does not pass through the shell source. In this case, the prior information obtained based on the shell source is: if the number of scintillator crystal IPs between the two scintillator crystals corresponding to the ends of the LOR is greater than or equal to 6, then the LOR passes through the target object, i.e., the shell source.

[0110] In one embodiment of the present application, for obtaining the prior information of irregularly shaped target objects, it is necessary to gradually count whether there are intersections between the target object and the lines where the LORs are located. MN When the number of scintillation crystal IPs between the IP numbers of the scintillation crystals M and N at both ends is greater than or equal to 5, the LOR MN There is an intersection with the target object. On the contrary, when the number of scintillation crystal IPs between them is less than 5, the LOR MN No intersection with the target object; LOR SR When the number of scintillation crystal IPs between the IP numbers of the scintillation crystals S and R at both ends is greater than or equal to 8, the LORSR There is an intersection with the target object. On the contrary, when the number of scintillation crystal IPs between the two intervals is less than 8, the LOR SR There is no intersection with the target object; ..., similarly, when the LORs formed between two of the 48 scintillation crystals intersect with the target object, the critical values ​​of the IP numbers of the scintillation crystals corresponding to the two ends of each LOR are counted one by one, and recorded and saved to form a priori information lookup table, so as to facilitate the subsequent judgment of whether the LOR intersects with the target object based on the LOR corresponding to the event and the priori information, thereby judging whether the LOR that meets the event passes through the target object.

[0111] In an embodiment of the present application, after obtaining prior information, an intersection determination module determines whether the line containing the LOR intersects the target object based on the prior information. In one example, using the shell source as the target object, the prior information obtained (if the number of scintillation crystal IPs between the scintillation crystals corresponding to the two ends of the LOR is greater than or equal to 6, then the LOR passes through the target object, i.e., the shell source) is consulted. If the two scintillation crystal IPs corresponding to the two ends of the LOR are separated by 5 scintillation crystal IPs, then the line containing the LOR does not pass through the target object, and all the matching events on the LOR are scattered events or random events and are discarded. Conversely, if the two scintillation crystal IPs corresponding to the two ends of the LOR are separated by 7 scintillation crystal IPs, then the line containing the LOR passes through the target object, and all the matching events on the LOR are true events.

[0112] In the embodiment of the present application, based on the sampling data, the coincident event Ki (i ≥ 1) on the LORi (i ≥ 1) passing through the target object is obtained as a true coincident event, and the coincident event Ki includes coincident event information. The coincident event information specifically includes but is not limited to the number of coincident events on each LOR, the time difference Δt between each coincident event, the numbering information of the scintillation crystals corresponding to the two ends of the LOR, the corresponding LOR, that is, the connecting line of the center surfaces of the two scintillation crystals, and the IP number of the scintillation crystals between the two scintillation crystals.

[0113] In some embodiments, after obtaining the LORi (i≥1) passing through the target object and the matching events Ki (i≥1) on each LORi based on the sampled data, the following steps are further included:

[0114] The filtered LORs and their corresponding matching event information are recorded in the recording module.

[0115] In one example, the recording module records the filtered LORs and their corresponding matching event information, including but not limited to the number of matching events on each LOR, the time difference Δt between each matching event, the serial numbers of the scintillation crystals corresponding to both ends of the LOR, the line connecting the centers of the surfaces of the two scintillation crystals corresponding to the LORs, and the IP serial numbers of the scintillation crystals between the two scintillation crystals. Recording in the recording module facilitates easy access and subsequent reconstruction of activity images.

[0116] Step S130: Based on all matching events of all LORi passing through the target object, an activity image is obtained, and pixel points Pi where each LORi passing through the target object intersects with the activity image are obtained, and based on the pixel points Pi, pixel value-time difference statistical distribution Ti corresponding to each LORi is obtained respectively.

[0117] In one embodiment, the step S130 may specifically include:

[0118] Step S131: Acquire an activity image based on all coincident events of all LORi passing through the target object.

[0119] In some embodiments, after obtaining coincident events passing through the target object in step S120, an activity image can be obtained based on all coincident events of all LORi passing through the target object. In one example, step S131 includes reconstructing the activity image using filtered back projection or an iterative method based on all coincident events of all LORi passing through the target object. The details of filtered back projection (FBP) or iterative methods can be found in the prior art and are not described in detail here.

[0120] The pixel value of each pixel point in the activity image obtained in the embodiment of the present application is the activity value. The pixel value is linearly proportional to the number of coincident events (assuming that the linear coefficient is k, the k value is determined by the specific type of PET detector used, and the proportional relationship between the pixel value of the activity image and the number of coincident events is determined by the type of PET detector used), which can be used to characterize the number of coincident events.

[0121] S132: Obtain pixel points Pi where each LORi passing through the target object intersects with the activity image.

[0122] In an embodiment of the present application, after obtaining the activity image, the pixel points Pi where each LORi passing through the target object intersects with the activity image can be obtained. In one example, obtaining the pixel points Pi where each LORi passing through the target object intersects with the activity image specifically includes: obtaining the pixel points Pi where each selected LORi intersects with the activity image based on a ray tracing method in the prior art. That is, based on the ray tracing method, each intersection point, i.e., the intersecting pixel points, of the LORs selected in step S120 and the activity image obtained in step S131 can be obtained. The specific operation can be referred to the prior art and will not be described in detail here.

[0123] S133: Obtain pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel point Pi.

[0124] In the embodiment of the present application, after obtaining the pixel point Pi, the pixel value-time difference statistical distribution Ti corresponding to each LORi can be obtained based on the pixel point Pi. Optionally, obtaining the pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel point Pi specifically includes the following steps:

[0125] Step S1331: Calculate the time difference between the pixel point Pi and the corresponding two end points of LORi one by one, and record the pixel value of each pixel point Pi;

[0126] Step S1332: determining a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pi, calculating the accumulated pixel values ​​of the pixel points Pi whose time differences fall within each time difference interval;

[0127] Step S1333: With the time difference interval as the horizontal axis step and the pixel value accumulation value of the pixel points falling within each step as the vertical axis, obtain the pixel value-time difference statistical distribution Ti corresponding to each LORi.

[0128] S140: Based on the coincident events Ki on each LORi, obtain the coincident event-time difference statistical distribution Mi corresponding to each LORi.

[0129] In an embodiment of the present application, after obtaining the LORi (i≥1) passing through the target object and the matching events Ki (i≥1) on each LORi based on the sampled data in step S120, a matching event-time difference statistical distribution Mi corresponding to each LORi can be obtained based on the matching events Ki on each LORi. In one example, this specifically includes:

[0130] The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Ti, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, so as to obtain the coincident event-time difference statistical distribution Mi corresponding to each LORi.

[0131] In the embodiment of the present application, the horizontal axis step size of the event-time difference statistical distribution Mi corresponding to each LORi and its corresponding pixel value-time difference statistical distribution Ti is the same, and the horizontal axis setting range is also the same, that is, the horizontal axis settings of Ti and Mi are exactly the same, so as to facilitate the subsequent calculation of the maximum value Yi of the inner product of each Ti and the corresponding Mi.

[0132] Step S150: Based on the pixel value-time difference statistical distribution Ti corresponding to each LORi and the event-time difference statistical distribution Mi, calculate the maximum value Yi of the inner product of each Ti and Mi, and obtain the difference δ between the time deviation corresponding to each LORi and the maximum value △ i.

[0133] In the embodiment of the present application, based on Ti and Mi, the maximum value Yi of the inner product of each Ti and Mi is calculated, and the difference δ between each LORi and the time deviation corresponding to the maximum value is obtained. △ i is implemented through the calculation module.

[0134] In some embodiments, the maximum value Yi of the inner product of each Ti and Mi is calculated, and the difference δ between LORi and the time deviation corresponding to the maximum value is obtained. △ i, including:

[0135] Taking Ti as the reference, translate Mi, calculate the inner product of Ti and Mi, and obtain the maximum value Yi of the inner product of Ti and Mi by the translation amount of Mi, which is δ △ i.

[0136] In the embodiment of the present application, the inner product of Ti and Mi is specifically the value obtained by multiplying and adding the values ​​of the ordinates corresponding to the same abscissas of Ti and Mi. From steps S130 to S140, it can be seen that the abscissas of Ti and Mi are set to be exactly the same, and the value of the ordinate corresponding to the abscissa of Ti is the cumulative value of the pixel values ​​corresponding to the time difference interval represented by the abscissa, and the value of the ordinate corresponding to the abscissa of Mi is the cumulative value of the matching events corresponding to the time difference interval represented by the abscissa, that is, the inner product of Ti and Mi is specifically the value obtained by multiplying and adding the cumulative value of the pixel values ​​corresponding to each abscissa and the cumulative value of the matching events.

[0137] It should be understood by those skilled in the art that, assuming that the scintillation crystals corresponding to the two ends of LORi are ci and di, the time offsets of the scintillation crystals ci and di are represented by δci and δdi respectively, and the difference between δci and δdi is represented by δ △ i, that is, δci-δdi=δ △ i, the time difference Ei of the coincident event on the LORi is represented by:

[0138] t ci +δci-(tdi +δdi)=Ei,

[0139] Among them, t ci , t di is the time data in the sampling data corresponding to the scintillation crystal ci and di received by the host computer, which can be sorted out as follows:

[0140] t ci -t di +(δci-δdi)=Ei,

[0141] When δci=δdi, we can get:

[0142] t ci -t di =Ei,

[0143] From the above formula, we can see that δci=δdi, that is, δci-δdi=δ △ When i = 0, the time difference between the coincident events on LORi is independent of δci and δdi, and depends solely on the location of the annihilation event. Two gamma photons generated at different annihilation locations on LORi correspond to two single events with different time differences, while two gamma photons generated at different times but at the same annihilation location correspond to two single events with the same time difference. If LORi corresponds to multiple coincident events, the number of coincident events corresponding to the same time difference is fixed. Accordingly, the fluctuations in the ordinates corresponding to the same abscissas in Mi and Ti are consistent, and the peaks of Mi and Ti must correspond, resulting in the maximum value Yi obtained by multiplying and adding the two.

[0144] That is, when the inner product value of Mi and Ti corresponding to a certain LORi is the largest, the peak values ​​of Mi and Ti correspond, and the time deviations δci and δdi of the two scintillation crystals ci and di corresponding to the two ends of the LORi satisfy δci-δdi=δ △ i=0.

[0145] On the contrary, if the inner product value of Mi and Ti corresponding to a certain LORi does not reach the maximum value Yi, then the peak values ​​of Mi and Ti do not correspond, δci-δdi=δ △ i, and δ △ i is not 0.

[0146] If the inner product value of Mi and Ti corresponding to a certain LORi does not reach the maximum value Yi (the peak values ​​of Mi and Ti do not correspond at this time), it is determined by δci-δdi=δ △ i, and δ △If the inner product value of Mi and Ti corresponding to the LORi reaches the maximum Yi (at this time, the peak values ​​of Mi and Ti correspond), the time deviation δci and δdi of the two scintillation crystals ci and di corresponding to the two ends of the LORi satisfy δci-δdi=δ △ Therefore, Mi and Ti can be moved relative to each other so that the inner product value of Mi and Ti reaches the maximum value from the non-maximum value. At this time, the relative movement amplitude of Mi and Ti is the difference δci and δdi. △ i, at this time, the time deviations δci and δdi of the two scintillation crystals ci and di corresponding to the two ends of LORi satisfy δci-δdi=δ △ i.

[0147] In the embodiment of the present application, assuming that the LORi of the two scintillation crystals ci and di at the two ends correspond to Mi and Ti, Mi can be moved with Ti as the comparison reference. Specifically, the relative movement can be achieved by the following operations:

[0148] First, determine δ by prior information △ For example, by long-term sampling and fitting, we can obtain LORi’s δci-δdi=δ △ i, obtain δ △ The range of i, for example, δ △ The range of i is [-5,5]ns.

[0149] Secondly, t represents the Ti horizontal axis (the horizontal axis step is the time difference interval range), and c represents the Ti horizontal axis (the horizontal axis step is the time difference interval range). T Characterize the vertical coordinate value of Ti (accumulated pixel value), that is, Ti(t,c T ), t represents the horizontal coordinate of Mi (the horizontal coordinate step is the time difference interval range), c M Characterize the vertical coordinate value of Mi (according to the event accumulation value), that is, get Mi(t,c M ), Mi(t,c M ) and Ti(t,c T ) are set to the same range of the horizontal axis t, and are all set to be larger than the δ obtained based on the prior information △ Set Mi(t,c M ) translation step, each time Mi(t,c M )Translate by a step size δ M , after moving n times, it corresponds to Mi(t+n*δ M ,c M ), the same horizontal coordinate corresponding to the moved Mi(t+n*δ M ,c M ) and Ti(t,c T) and add the vertical coordinates to get <Mi(t+n*δ M ,c M ),Ti(t,c T )>n*δ when the inner product reaches its maximum value Yi M value, then M(t+n*δ M ,c M ) and T(t,c T )>The peak value corresponds to the maximum, Mi and Ti change from peak non-correspondence to peak correspondence, and the n*δ of this translation M That is, the difference δ between the time deviations δci and δdi of the scintillation crystals ci and di at both ends of LORi corresponding to Mi and Ti △ i, that is, δci-δdi=δ △ i=n*δ M .

[0150] Step S160: Based on the δ △ iGet the time correction value.

[0151] In the embodiment of the present application, δ is obtained △ After i, we can △ i obtains the time correction value. In one example, based on the δ △ i Obtain the time correction value, including:

[0152] Step S161: Based on the δ △ i. Obtain the relationship between the time deviations δci and δdi of the scintillation crystals ci and di of the detection modules at both ends of each LORi: δci-δdi=δ △ i;

[0153] Step S162: A set of simultaneous equations is used to obtain the time deviations δci and δdi of the scintillation crystals ci and di of the detection modules at both ends of each LORi by a fitting method. δci and δdi are the time correction values ​​of the scintillation crystals ci and di.

[0154] In the embodiment of the present application, after obtaining the time deviations δci and δdi of the scintillation crystals ci and di of the detection modules at both ends of each LORi, i.e., the time correction values, the following steps may also be included:

[0155] Step S170: performing time correction on the sampled data based on the acquired time correction value.

[0156] In a specific example of the present application, the time data corresponding to the scintillation crystals ci and di of the detection module in the sampled data is corrected, including:

[0157] The time data t corresponding to the scintillation crystals ci and di of the detection module in the sampling data ci , tdi Subtract the time correction values ​​δci and δdi respectively.

[0158] The embodiment of the present application obtains the pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi corresponding to each LORi based on the true coincident events passing through the target object, and calculates the maximum value Yi of the inner product of each Ti and Mi, and obtains the difference δ of the time deviation corresponding to each LORi and the maximum value. △ i, then based on the δ △ i obtains time correction values, which are applicable to any target object and have wide applicability. It does not require Gaussian fitting, thus eliminating the need for long sampling times, saving time and improving time correction efficiency. It also eliminates the need for high-activity drugs, improving operational safety. Furthermore, because the present embodiment uses the filtered true coincidence events passing through the target object to obtain the pixel value-time difference statistical distribution Ti and coincidence event-time difference statistical distribution Mi corresponding to each LORi, random events and scattered events are discarded, thereby improving the difference δ of the time deviations corresponding to each LORi. △ The accuracy of i is improved, thereby improving the accuracy of time correction.

[0159] In some embodiments, as Figure 2 As an alternative or supplement to the embodiment, based on all LORi passing through the target object, LORj (j≥1) whose number of events meets the preset condition can be screened. Specifically, Figure 3 The time correction method shown in the embodiment may include the following steps S220, S230, S240, S250, S260, S270 and S280.

[0160] Before implementing the method, the pulse signal obtained based on the target object may be sampled in step S210 to obtain sampled data.

[0161] The target object, pulse signal, sampling data and their acquisition in the embodiments of this application can be referred to Figure 2 The features in step S110 are not described in detail here.

[0162] Step S220 : Based on the sampling data of the target object, obtain LORi (i≥1) passing through the target object and the matching events Ki (i≥1) on each LORi.

[0163] In the embodiment of the present application, the LORi (i≥1) passing through the target object and the matching event Ki (i≥1) on each LORi can be obtained by referring to Figure 2 The features of step S120 in the time correction method are not described in detail here.

[0164] Step S230: Acquire an activity image based on all coincident events of all LORi passing through the target object.

[0165] The activity image obtained in the embodiment of this application can be referred to Figure 2 The features of step S131 in the time correction method shown are not described in detail here.

[0166] Step S240: Based on all LORi that pass through the target object, LORj (j≥1) whose number of events meets a preset condition is screened.

[0167] Those skilled in the art will appreciate that if the number of coincident events corresponding to a LOR is too small, the coincident events on that LOR can generally be considered scattered events or random events. For example, if there is only one pair of coincident events on a particular LOR, the coincident events on that LOR can be considered scattered events or random events. To further improve the accuracy of the correction, further screening of true events is necessary. Certain criteria can be set to screen true events from the coincident events to discard scattered events or random events.

[0168] In the embodiment of the present application, after obtaining all LORi based on the target object, LORj (j≥1) whose number of events meets the preset condition can be screened. In a specific example, step S240 specifically includes:

[0169] Step S241: Setting a benchmark value for event quantity comparison.

[0170] In the embodiments of the present application, the reference value for the comparison of the number of matching events can be set based on prior information or according to specific needs. For example, the reference value for the number of matching events used for comparison can be set to 20. If the number of matching events corresponding to each LOR is large, the reference value can be set larger; otherwise, the reference value can be set smaller.

[0171] Step S242: Determine whether the number of matching events is greater than a reference value.

[0172] In the embodiment of the present application, the number of matching events corresponding to each LOR is compared with the benchmark value. If the number of matching events corresponding to a certain LOR is greater than the benchmark value, it meets the requirements, and the LOR is retained and recorded; otherwise, the LOR is discarded.

[0173] Step S243: using a storage module to store the LORs that meet the event number greater than the reference value.

[0174] In the embodiment of the present application, the LOR that meets the requirements determined in step S242 is stored in the storage module.

[0175] Step S250: Obtain pixel points Pj where each screened LORj intersects with the activity image, and obtain pixel value-time difference statistical distribution Tj corresponding to each LORj based on the pixel points Pj.

[0176] In one example, step S250 specifically includes:

[0177] Step S251: Obtain the pixel points Pj where each filtered LORj intersects with the activity image.

[0178] In an embodiment of the present application, after acquiring the activity image, pixel points Pj where each LORj passing through the target object intersects with the activity image can be obtained. In one example, step S251 specifically includes: obtaining pixel points Pj where each selected LORj intersects with the activity image based on a ray tracing method. The specific operation of the ray tracing method can be referenced in the prior art and will not be described in detail here.

[0179] Step S252: Based on the pixel point Pj, respectively obtain the pixel value-time difference statistical distribution Tj corresponding to each LORj.

[0180] In the embodiment of the present application, step S252 specifically includes:

[0181] Calculate the time difference between the pixel point Pj and the corresponding two end points of LORj one by one, and record the pixel value of each pixel point Pj;

[0182] Determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculate the cumulative value of the pixel values ​​of the pixel point Pj whose time difference falls within each time difference interval;

[0183] The time difference interval is used as the horizontal axis step length, and the cumulative pixel value of the pixel points falling into each step length is used as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each LORj.

[0184] Step S260: Obtain the statistical distribution Mj of the event-time difference corresponding to each screened LORj.

[0185] In one example, step S260 specifically includes: determining the horizontal axis with the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and using the cumulative value of the matching events whose time difference falls into each step size as the vertical axis, to obtain the matching event-time difference statistical distribution Mj corresponding to each LORj.

[0186] In the embodiment of the present application, the horizontal axis step size of the event-time difference statistical distribution Mj corresponding to each LORj and its corresponding pixel value-time difference statistical distribution Tj are the same, and the horizontal axis setting range is also the same, that is, the horizontal axis settings of Tj and Mj are exactly the same, so as to facilitate the subsequent calculation of the maximum value Yj of the inner product of each Tj and the corresponding Mj.

[0187] Step S270: Based on the pixel value time difference statistical distribution Tj corresponding to each screened LORj and the event-time difference statistical distribution Mj, calculate the maximum value Yj of the inner product of each Tj and Mj, and obtain the time deviation difference δ corresponding to each LORj and the maximum value △ j.

[0188] In some embodiments, the maximum value Yj of the inner product of each Tj and Mj is calculated, and the difference δ between LORj and the time deviation corresponding to the maximum value is obtained. △ j, including:

[0189] Taking Tj as the reference, translate Mj, calculate the inner product of Tj and Mj, and obtain the maximum value Yj of the inner product of Tj and Mj by counting the translation amount of Mj, which is δ △ j.

[0190] In the embodiment of the present application, based on the statistical distribution Tj of the pixel value time difference corresponding to each screened LORj and the statistical distribution Mj of the event-time difference, the maximum value Yj of the inner product of each Tj and Mj is calculated, and the difference δ of the time deviation corresponding to each LORj and the maximum value is obtained. △ j is implemented through the calculation module.

[0191] In the embodiment of the present application, the maximum value Yj of the inner product of each Tj and Mj is calculated, and the difference δ between each LORj and the time deviation corresponding to the maximum value is obtained. △ j, you can refer to Figure 2 The features of step S150 in the time correction method shown are not described in detail here.

[0192] Step S280: Based on the maximum value δ △ jGet the time correction value.

[0193] In one example, based on the δ △ j Obtain the time correction value, including:

[0194] Step S281: Based on the δ △ j, and obtain the relationship between the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each LORj. δcj-δdj=δ △ j;

[0195] Step S282: simultaneous equations, obtaining the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each LORj by a fitting method, where δcj and δdj are the time correction values ​​of the scintillation crystals cj and dj.

[0196] In the embodiment of the present application, after obtaining the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each LORj, i.e., the time correction values, the following steps may also be included:

[0197] Based on the time deviation δcj, δdj of the scintillation crystals cj, dj of the detection module, the time data corresponding to the scintillation crystals cj, dj of the detection module in the sampled data is corrected, for example: the time data t corresponding to the scintillation crystals cj, dj of the detection module in the sampled data is corrected. cj , t dj Subtract the time correction values ​​δcj and δdj respectively.

[0198] This application Figure 3 The embodiment shown is Figure 2 The difference between the embodiments shown is that by screening LORj (j≥1) whose number of events meets the preset conditions based on all LORi passing through the target object, random events and scattered events in the matching events are further discarded, and as many true events as possible are screened out for subsequent acquisition of time correction values, thereby improving the accuracy of the acquired time correction values, that is, improving the effect of time correction.

[0199] In some embodiments, the meanings or descriptions of the same or similar terms or features of the time correction method of this embodiment can refer to Figure 2 The time correction method of the embodiment shown, Figure 2 The steps and features of the illustrated embodiment can be combined with the time correction method of this embodiment in a non-contradictory manner.

[0200] The embodiment of the present application obtains the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj corresponding to each LORj based on the true coincident events that pass through the target object, and calculates the maximum value Yj of the inner product of each Tj and Mj, and obtains the difference δ between the time deviation corresponding to each LORj and the maximum value △ j, then based on the δ △ j obtains the time correction value, which is applicable to any target object, has wide applicability, and does not require Gaussian fitting, so long sampling is not required, which saves time, improves time correction efficiency, and does not require the use of highly active drugs, thereby improving operational safety. In addition, since the embodiment of the present application is based on the true coincidence events corresponding to the LORs that have passed through the target object and the number of coincidence events that meet the preset conditions, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each LORj are obtained, random events and scattered events are further discarded, and the difference value δ of the time deviation corresponding to each LORj obtained is further improved accordingly. △ j, thereby further improving the accuracy of time correction.

[0201] Figure 4 This is an exemplary module diagram of a time correction device according to some embodiments of the present application.

[0202] Figure 4 A time correction device is shown, which may include:

[0203] Coincidence event screening module 430 , activity image reconstruction module 440 , pixel value-time difference statistical distribution acquisition module 450 , coincidence event-time difference statistical distribution acquisition module 460 , calculation module 470 , time correction value acquisition module 480 .

[0204] In some embodiments, the coincident event screening module 430 is configured to obtain LORi (i≥1) passing through the target object and coincident events Ki (i≥1) on each LORi based on the sampled data of the target object.

[0205] In one example, the coincidence event screening module 430 includes an intersection determination module, which is configured to determine whether the line containing the LOR intersects the target object and, based on the number of intersections, determine whether the LOR passes through the target object. Specifically, the intersection determination module can determine whether the line containing the LOR intersects the target object based on prior information. In one specific example, the prior information includes the number of scintillation crystal IPs separating the scintillation crystals of the detection modules at both ends of the LOR. The number of scintillation crystal IPs separating the scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the line containing the LOR.

[0206] In some embodiments, the activity image reconstruction module 440 is configured to acquire an activity image based on all coincident events of all LORi passing through the target object. In one example, the activity image reconstruction module 440 acquires the activity image based on all coincident events of all LORi passing through the target object by reconstructing the activity image using filtered back projection or an iterative method.

[0207] In some embodiments, the pixel value-time difference statistical distribution acquisition module 450 is configured to obtain each pixel point Pi where each LORi passing through the target object intersects with the activity image, and obtain the pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel point Pi.

[0208] In one example, the pixel value-time difference statistical distribution acquisition module 450 includes a pixel point acquisition module and a time difference statistical distribution acquisition module. The pixel point acquisition module is used to obtain the pixel points Pi where the filtered LORi intersects with the activity image based on a ray tracing method; the time difference statistical distribution acquisition module is used to obtain the pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel point Pi.

[0209] In a specific example, the time difference statistical distribution acquisition module includes a pixel point time difference acquisition module, a pixel value accumulation module and a pixel value-time difference statistical distribution Ti acquisition module. The pixel point time difference acquisition module is used to calculate the time difference from the pixel point Pi to the corresponding LORi two end points one by one, and record the pixel value of each pixel point Pi; the pixel value accumulation module is used to determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pi, calculate the cumulative value of the pixel value of the pixel point Pi whose time difference falls into each time difference interval; the pixel value-time difference statistical distribution Ti acquisition module is used to use the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis to obtain the pixel value-time difference statistical distribution Ti corresponding to each LORi.

[0210] In some embodiments, the coincidence event-time difference statistical distribution acquisition module 460 is configured to acquire the coincidence event-time difference statistical distribution Mi corresponding to each LORi.

[0211] In a specific example, in order to obtain the event-time difference statistical distribution Mi corresponding to each LORi, the event-time difference statistical distribution acquisition module 460 is configured as follows: the horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Ti as the step size, and the vertical axis is determined by the cumulative value of the event whose time difference falls into each step size, so as to obtain the event-time difference statistical distribution Mi corresponding to each LORi.

[0212] In some embodiments, the calculation module 470 is configured to calculate the maximum value Yi of the inner product of each Ti and Mi, and obtain the difference δ between each LORi and the time deviation corresponding to the maximum value. △ i.

[0213] In some embodiments, the time correction value acquisition module 480 is configured based on δ △ i Obtain a time correction value. In one example, the time correction value is the time deviation δci, δdi of the scintillation crystals ci, di of the detection modules at both ends of each LORi.

[0214] In a specific example, the time correction value acquisition module 480 includes a fitting module configured to obtain the relationship between the time deviations δci and δdi of the scintillation crystals ci and di of the detection modules at both ends of each LORi based on the said δi, and the relationship δci-δdi=δi; a group of simultaneous equations, and obtain the time correction values ​​of the scintillation crystals ci and di of the detection modules at both ends of each LORi through a fitting method.

[0215] In some embodiments, the calculation module and the time correction value acquisition module can be implemented by the same device.

[0216] In some embodiments, the time correction device may further include a coincidence module for acquiring all coincidence events and the LOR corresponding to each coincidence event based on the sampled data. In one example, the sampled data may include the scintillation crystal number information of the detection module and the time information of the pulse signal; the coincidence module includes a pulse signal energy information acquisition module for acquiring the energy information of the pulse signal based on the sampled data, acquiring coincidence events based on the time information and energy information of the pulse signal, and acquiring the LOR corresponding to the coincidence event based on the scintillation crystal number information.

[0217] In some embodiments, the time correction device may further include a recording module for recording the time difference of the corresponding event and the corresponding scintillation crystal number information of the detection modules at both ends of the LOR.

[0218] In some embodiments, the time correction device further includes a correction module, the sampling data includes the scintillation crystal number information of the detection module and the time information of the pulse signal, and the correction module is used to correct the pulse signal time information in the sampling data based on the time correction value.

[0219] In one example, the correction module corrects the pulse signal time information in the sampled data based on the time correction value, and corrects the time data corresponding to the scintillation crystals ci and di of the detection module in the sampled data, including: correcting the time data t corresponding to the scintillation crystals ci and di of the detection module in the sampled data ci , t di Subtract the time correction values ​​δci and δdi respectively.

[0220] The embodiment of the present application obtains the pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi corresponding to each LORi based on the true coincident events passing through the target object, and calculates the maximum value Yi of the inner product of each Ti and Mi, and obtains the difference δ of the time deviation corresponding to each LORi and the maximum value. △ i, then based on the δ △ i obtains time correction values, which are applicable to any target object and have wide applicability. It does not require Gaussian fitting, thus eliminating the need for long-term sampling, saving time and improving time correction efficiency. Furthermore, since the present embodiment is based on the true coincidence events that have passed through the target object, the pixel value-time difference statistical distribution Ti and coincidence event-time difference statistical distribution Mi corresponding to each LORi are obtained, random events and scattered events are discarded, thereby improving the difference δ of the time deviation corresponding to each LORi. △ The accuracy of i is improved, thereby improving the accuracy of time correction.

[0221] In some embodiments, as Figure 4Alternatively or in addition to the embodiment, two matching event screening modules may be provided, wherein the first matching event screening module corresponds to Figure 4 The matching event screening module of the embodiment shown is a second matching event screening module, which is configured to screen LORj whose matching event quantity meets a preset reference value based on all LORi passing through the target object. Specifically, Figure 5 The time correction device shown in the embodiment may include:

[0222] The first matching event screening module 530 is configured to obtain LORi (i≥1) passing through the target object and matching events Ki (i≥1) on each LORi based on the sampled data of the target object;

[0223] an activity image reconstruction module 540 configured to acquire an activity image based on all coincident events of all LORi passing through the target object;

[0224] The second matching event screening module 550 is configured to screen LORj whose number of matching events meets a preset reference value based on all LORi passing through the target object;

[0225] The pixel value-time difference statistical distribution acquisition module 560 is configured to acquire each pixel point Pj where each selected LORj intersects with the activity image, and acquire the pixel value-time difference statistical distribution Tj corresponding to each LORj based on the pixel point Pj;

[0226] The matching event-time difference statistical distribution acquisition module 570 is configured to obtain the matching event-time difference statistical distribution Mj corresponding to each screened LORj;

[0227] The calculation module 580 is configured to calculate the maximum value Yj of the inner product of each Tj and Mj, and obtain the difference δ between each LORj and the time deviation corresponding to the maximum value △ j;

[0228] The time correction value acquisition module 590 is configured to obtain the time correction value based on the δ △ jGet the time correction value.

[0229] This embodiment and Figure 4 The difference of the embodiment shown is that the embodiment has two matching event screening modules, wherein the first matching event screening module 530 corresponds to Figure 4 The matching event screening modules of the illustrated embodiments are configured to obtain LORi (i≥1) passing through the target object and matching events Ki (i≥1) on each LORi based on the sampled data. Figure 4In addition, this embodiment also includes a second matching event screening module 550, which is configured to screen LORj whose number of matching events meets a preset reference value based on all LORi passing through the target object. In one example, the second matching event screening module includes: a reference value setting module for setting a reference value for comparing the number of matching events; a determination module for determining whether the number of matching events exceeds the reference value; and a storage module for storing LORs indicating whether the number of matching events exceeds the reference value.

[0230] This embodiment sets a second matching event screening module 550 to screen LORj (j≥1) whose number of matching events meets a preset condition based on all LORi passing through the target object, further discards random events and scattered events among the matching events, and screens out as many true events as possible for subsequent acquisition of time correction values, thereby improving the accuracy of the acquired time correction values, that is, improving the effect of time correction.

[0231] In the embodiment of the present application, the time correction device may include, in a non-contradictory manner, Figure 4 The components or features of the time correction method embodiment shown in the figure, or the embodiment shown in the figure can be used with Figure 4 Exemplary embodiments may be combined to create new embodiments, and vice versa.

[0232] The embodiment of the present application obtains the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj corresponding to each LORj based on the true coincident events that pass through the target object, and calculates the maximum value Yj of the inner product of each Tj and Mj, and obtains the difference δ between the time deviation corresponding to each LORj and the maximum value △ j, then based on the δ △ j obtains the time correction value, which is applicable to any target object, has wide applicability, and does not require Gaussian fitting, so long sampling is not required, saving time, improving time correction efficiency, and not using highly active drugs, improving operational safety. In addition, since the embodiment of the present application is based on the true coincidence events corresponding to the LORs that have passed through the target object and the number of coincidence events that meet the preset conditions, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each LORj are obtained, random events and scattered events are further discarded, and the difference δ of the time deviation corresponding to each LORi obtained is further improved accordingly. △ j, thereby further improving the accuracy of time correction.

[0233] In some embodiments, the present application also provides a digitizing device, which may include the time correction device, detection module, and sampling module mentioned in the above embodiments. The digitizing device can be used to correct the time data of the pulse signal acquired based on the target object, thereby improving the correction efficiency, correction effect, and correction safety. The digitizing device uses the time correction device to detect the target object, acquire sampling data, and correct the sampling data based on the time correction value to acquire corrected time data. A digitized image is formed based on the acquired coincident events and the corrected time data. In a specific example, the digitizing device is a positron emission tomography (PET) device.

[0234] In some embodiments, the detection module is configured to acquire a pulse signal based on the target object. The detection module 410 includes a detector including a scintillation crystal and a photoelectric conversion element. The scintillation crystal is used to convert gamma rays into visible light, and the photoelectric conversion element is used to convert visible light into a pulse signal.

[0235] In some embodiments, the sampling module is configured to sample the pulse signal to obtain sampled data. Specific details of the sampled data can be found in the method embodiments and will not be described in detail here.

[0236] In one example, the sampling module is a multi-voltage threshold sampling module, which includes a threshold setting module, a comparison module, a time-to-digital conversion module, and an information storage module, wherein the threshold setting module is used to set the sampling threshold; the comparison module is used to compare the pulse signal with the threshold and output a jump signal; the time-to-digital conversion module is used to perform time sampling on the jump signal to obtain the time information of the pulse signal; the information storage module stores the scintillation crystal number information of the detection module and the time information of the pulse signal.

[0237] In the embodiment of the present application, the digitization device can directly obtain the annihilation position based on the corrected time data and coincident events, thereby directly forming a digitized image (such as a PET image), without the need for complex image reconstruction methods, thereby simplifying image reconstruction.

[0238] The apparatus described in the embodiments of the present application may be combined with features of the methods described in the embodiments of the present application, and vice versa.

[0239] In some embodiments, the present application also provides a computer device, comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the method described in any embodiment of the present application.

[0240] Although not shown, in some embodiments, a computer-readable storage medium is further provided, storing a computer program configured to execute the steps of any of the methods of the embodiments of the present application when executed. The computer program includes various program modules / units that constitute the apparatus according to the embodiments of the present application. When the computer program composed of the various program modules / units is executed, it can implement the functions corresponding to the various steps in the methods described in the above embodiments. The computer program can also be executed on the electronic device described in the embodiments of the present application.

[0241] While the basic concepts have been described herein, it will be apparent to those skilled in the art that the detailed disclosure is merely illustrative and does not limit the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and amendments to the present application. Such modifications, improvements, and amendments are suggested in the present application and remain within the spirit and scope of the exemplary embodiments of the present application.

[0242] At the same time, this application uses specific terms to describe the embodiments of this application. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment," "an embodiment," or "an alternative embodiment" mentioned twice or multiple times in different locations in this application does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0243] In addition, it will be understood by those skilled in the art that various aspects of the present application can be illustrated and described by a number of patentable categories or situations, including any new and useful process, machine, product or combination of substances, or any new and useful improvements thereto. Accordingly, various aspects of the present application can be performed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may all be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". In addition, various aspects of the present application may be represented as a computer product located in one or more computer-readable media, which includes computer-readable program code.

[0244] A computer storage medium may include a propagated data signal embodying the computer program code, for example, in baseband or as part of a carrier wave. The propagated signal may be in a variety of forms, including electromagnetic, optical, or any suitable combination thereof. A computer storage medium may be any computer-readable medium other than a computer-readable storage medium that can be connected to an instruction execution system, apparatus, or device to communicate, propagate, or transfer the program for use. The program code on the computer storage medium may be transmitted via any suitable medium, including radio, cable, fiber optic cable, RF, or similar media, or any combination of these.

[0245] The computer program code required for the operation of each part of the present application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python, etc., conventional procedural programming languages ​​such as C language, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, dynamic programming languages ​​such as Python, Ruby and Groovy, or other programming languages. The program code can be run entirely on the user's computer, or as a separate software package on the user's computer, or partly on the user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any network form, such as a local area network (LAN) or a wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as software as a service (SaaS).

[0246] In addition, unless expressly stated in the claims, the order of the processing elements and sequences described in this application, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this application. Although the above disclosure discusses some of the invention embodiments currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this application. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only by software solutions, such as installing the described system on an existing server or mobile device.

[0247] Similarly, it should be noted that, in order to simplify the presentation of this application and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this application sometimes combine multiple features into a single embodiment, figure, or description thereof. However, this disclosure method does not mean that the subject matter of this application requires more features than those recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single embodiment disclosed above.

[0248] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0249] Each patent, patent application, patent application disclosure, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this application is hereby incorporated by reference in its entirety. This includes application history documents that are inconsistent with or conflict with the content of this application, as well as documents (currently or subsequently attached to this application) that limit the broadest scope of the claims of this application. It should be noted that if the descriptions, definitions, and / or use of terms in the accompanying materials of this application are inconsistent or conflicting with the content of this application, the descriptions, definitions, and / or use of terms in this application shall prevail.

[0250] Finally, it should be understood that the embodiments described in this application are merely illustrative of the principles of the embodiments of this application. Other variations may also fall within the scope of this application. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this application may be considered consistent with the teachings of this application. Accordingly, the embodiments of this application are not limited to the embodiments explicitly introduced and described in this application.

Claims

1. A time correction method, characterized in that: include: Based on the sampling data of the target object, the response line LORi passing through the target object and the coincident events Ki on each response line LORi are obtained, where i represents the number, i≥1; Based on all coincident events of all response lines LORi passing through the target object, an activity image is obtained, and pixel points Pi where each response line LORi passing through the target object intersects with the activity image are obtained, and based on the pixel points Pi, a pixel value-time difference statistical distribution Ti corresponding to each response line LORi is obtained respectively; Based on the coincident events Ki on each response line LORi, obtain the coincident event-time difference statistical distribution Mi corresponding to each response line LORi; Based on the pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi, the maximum value Yi of the inner product of each pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi is calculated, and the difference δ of the time deviation corresponding to each response line LORi and the maximum value Yi is obtained. △ i; Based on the difference δ △ iGet the time correction value.

2. The time correction method according to claim 1, wherein: The response line LORi passing through the target object includes: the response line LORi and the target object have at least one intersection point, or the response line LORi is tangent to or intersects with the target object.

3. The time correction method according to claim 1, wherein: Based on the sampled data, the response lines LORi (i≥1) passing through the target object and the coincident events Ki on each response line LORi are obtained, including: Obtain all coincident events and the corresponding LORs of each coincident event based on the sampling data; All response lines LORi passing through the target object and the matching events Ki on each response line LORi are screened.

4. The time correction method according to claim 3, characterized in that: Filter all response lines LORi passing through the target object and the matching events Ki on each response line LORi, including: Based on prior information, it is determined whether the line of response LOR and the target object have an intersection.

5. The time correction method according to claim 4, characterized in that: The prior information includes the number of IPs of the scintillation crystals spaced between the scintillation crystals at both ends of the line of response (LOR). The number of IPs of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the line where the line of response (LOR) is located.

6. The time correction method according to claim 1, wherein: Acquire activity images based on all coincident events of all lines of response LORi passing through the target object, including: Based on all coincident events of all lines of response LORi passing through the target object, an activity image is reconstructed using filtered back projection or iterative methods.

7. The time correction method according to claim 1, wherein: Obtain each pixel point Pi where each response line LORi passing through the target object intersects the activity image, including: Based on the ray tracing method, the pixel points Pi where each selected response line LORi intersects with the activity image are obtained.

8. The time correction method according to claim 1, wherein: Obtaining pixel value-time difference statistical distribution Ti corresponding to each response line LORi based on the pixel point Pi, including: Calculate the time difference from the pixel point Pi to the two end points of the corresponding response line LORi one by one, and record the pixel value of each pixel point Pi; Determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pi, calculate the cumulative value of the pixel values ​​of the pixel points Pi whose time differences fall within each time difference interval; The time difference interval is used as the horizontal axis step length, and the pixel value accumulation value of the pixel points falling into each step length is used as the vertical axis to obtain the pixel value-time difference statistical distribution Ti corresponding to each response line LORi.

9. The time correction method according to claim 8, characterized in that: Based on the coincident events Ki on each response line LORi, a coincident event-time difference statistical distribution Mi corresponding to each response line LORi is obtained, including: The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Ti, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mi corresponding to each response line LORi is obtained.

10. The time correction method according to claim 1, wherein: Calculate the maximum value Yi of the inner product of each pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi, and obtain the difference δ between each response line LORi and the time deviation corresponding to the maximum value △ i, including: Taking the pixel value-time difference statistical distribution Ti as the benchmark, translate the event-time difference statistical distribution Mi, calculate the inner product of the pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi, and obtain the maximum value Yi of the inner product when the translation amount of the event-time difference statistical distribution Mi is obtained. The translation amount is the difference δ △ i.

11. The time correction method according to claim 1, wherein: Based on the difference δ of the time offset △ i Get the time correction value, including: Based on the difference δ of the time offset △ i. Obtain the relationship between the time deviations δci and δdi of the scintillator crystals ci and di at both ends of each response line LORi, δci-δdi=δ △ i; The simultaneous equations are fitted to obtain the time deviations δci and δdi of the scintillation crystals ci and di at both ends of each response line LORi. The time deviations δci and δdi are the time correction values ​​of the scintillation crystals ci and di.

12. The time correction method according to claim 11, characterized in that: The time correction method further includes: The sampling data is time-corrected based on the acquired time correction value, that is, based on the time deviations δci and δdi of the scintillation crystals ci and di, the time data corresponding to the scintillation crystals ci and di in the sampling data are corrected.

13. The time correction method according to claim 12, characterized in that: Correcting the time data corresponding to the scintillation crystals ci and di in the sampled data, including: correcting the time data t corresponding to the scintillation crystals ci and di in the sampled data ci , t di Subtract the time correction values ​​δci and δdi respectively.

14. A time correction method, characterized in that: include: Based on the sampling data of the target object, the response line LORi passing through the target object and the coincident events Ki on each response line LORi are obtained, where i represents the number, i≥1; Acquire an activity image based on all coincident events of all response lines LORi passing through the target object; Based on all response lines LORi passing through the target object, the response lines LORj whose number of events meets the preset conditions are screened, where j represents the number, j ≥ 1; Obtain the pixel points Pj where each selected response line LORj intersects with the activity image, and obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel points Pj; Obtain the statistical distribution Mj of the event-time difference corresponding to each selected response line LORj; Based on the pixel value time difference statistical distribution Tj corresponding to each screened response line LORj and the event-time difference statistical distribution Mj, the maximum value Yj of the inner product of each pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj is calculated, and the difference δ of the time deviation corresponding to each response line LORj and the maximum value is obtained. △ j; Based on the difference δ △ jGet the time correction value.

15. The time correction method according to claim 14, characterized in that: The response line LORi passing through the target object includes: the response line LORi and the target object have at least one intersection point, or the response line LORi is tangent to or intersects with the target object.

16. The time correction method according to claim 14, characterized in that: Based on the sampled data, the response lines LORi passing through the target object and the coincident events Ki on each response line LORi are obtained, including: Obtain all coincident events and the corresponding LORs of each coincident event based on the sampling data; All response lines LORi passing through the target object and the matching events Ki on each response line LORi are screened.

17. The time correction method according to claim 16, characterized in that: Filter all response lines LORi passing through the target object and the matching events Ki on each response line LORi, including: Based on prior information, it is determined whether the line of response LOR and the target object have an intersection.

18. The time correction method according to claim 17, characterized in that: The prior information includes the number of IPs of the scintillation crystals spaced between the scintillation crystals at both ends of the line of response (LOR). The number of IPs of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the line where the line of response (LOR) is located.

19. The time correction method according to claim 14, wherein: Acquire activity images based on all coincident events of all lines of response LORi passing through the target object, including: Based on all coincident events of all lines of response LORi passing through the target object, an activity image is reconstructed using filtered back projection or iterative methods.

20. The time correction method according to claim 14, wherein: Based on all response lines LORi passing through the target object, select response lines LORj whose number of events meets the preset conditions, including: Setting a benchmark value for comparison of the number of events; Determine whether the number of matching events is greater than the benchmark value; The response line LOR corresponding to the number of events greater than the reference value is stored.

21. The time correction method according to claim 14, wherein: Obtain the pixel point Pj where each selected response line LORj intersects with the activity image, including: The pixel points Pj where each selected response line LORj intersects with the activity image are obtained based on the ray tracing method.

22. The time correction method according to claim 14, characterized in that: Obtaining pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel point Pj, including: Calculate the time difference from pixel point Pj to the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj; Determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculate the cumulative value of the pixel values ​​of the pixel point Pj whose time difference falls within each time difference interval; The time difference interval is used as the horizontal axis step length, and the pixel value accumulation value of the pixel points falling into each step length is used as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

23. The time correction method according to claim 22, characterized in that: Obtain the statistical distribution Mj of the event-time difference corresponding to each selected response line LORj, including: The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Tj, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mj corresponding to each response line LORj is obtained.

24. The time correction method according to claim 14, characterized in that: Calculate the maximum value Yj of the inner product of each pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and obtain the difference δ between each response line LORj and the time deviation corresponding to the maximum value △ j, including: Taking the pixel value-time difference statistical distribution Tj as the benchmark, translate the event-time difference statistical distribution Mj, calculate the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and calculate the translation amount of the event-time difference statistical distribution Mj when obtaining the maximum value Yj. The translation amount is the difference δ △ j.

25. The time correction method according to claim 14, wherein: Based on the difference δ △ jGet the time correction value, including: Based on the difference δ △ j, and obtain the relationship between the time deviations δcj and δdj of the scintillator crystals cj and dj at both ends of each response line LORj. δcj-δdj=δ △ j; The simultaneous equations are fitted to obtain the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj. The time deviations δcj and δdj are the time correction values ​​of the scintillation crystals cj and dj.

26. The time correction method according to claim 14, wherein: The time correction method further includes: The sampled data is time-corrected based on the acquired time correction value, that is, based on the time deviations δcj and δdj of the scintillation crystals cj and dj, the time data corresponding to the scintillation crystals cj and dj in the sampled data is corrected.

27. The time correction method according to claim 26, characterized in that: Correcting the time data corresponding to the scintillation crystals cj and dj in the sampled data includes: correcting the time data t corresponding to the scintillation crystals cj and dj in the sampled data cj , t dj Subtract the time correction values ​​δcj and δdj respectively.

28. A time correction device, characterized in that: include: A coincidence event screening module is configured to obtain, based on the sampling data of the target object, a response line LORi passing through the target object and a coincidence event Ki on each response line LORi, where i represents the number, i≥1; an activity image reconstruction module configured to acquire an activity image based on all coincident events of all response lines LORi passing through the target object; a pixel value-time difference statistical distribution acquisition module configured to acquire each pixel point Pi where each response line LORi passing through the target object intersects with the activity image, and acquire the pixel value-time difference statistical distribution Ti corresponding to each response line LORi based on the pixel point Pi; A coincidence event-time difference statistical distribution acquisition module is configured to obtain a coincidence event-time difference statistical distribution Mi corresponding to each response line LORi; The calculation module is configured to calculate the maximum value Yi of the inner product of each pixel value-time difference statistical distribution Ti and the event-time difference statistical distribution Mi, and obtain the difference δ of the time deviation corresponding to each response line LORi and the maximum value △ i; A time correction value acquisition module is configured to obtain a time correction value based on the difference δ △ iGet the time correction value.

29. The time correction device according to claim 28, characterized in that The sampling data includes scintillation crystal number information and pulse signal time information; The coincidence event screening module is further configured to obtain energy information of the pulse signal based on the sampled data, obtain coincidence events based on time information and energy information of the pulse signal, and obtain the line of response (LOR) corresponding to the coincidence event based on the scintillation crystal number information.

30. The time correction device according to claim 29, characterized in that The time correction device also includes: The recording module is configured to record the time difference of the event and the corresponding scintillation crystal number information at both ends of the response line LOR.

31. The time correction device according to claim 28, characterized in that The coincidence event screening module is further configured to determine whether the line on which the response line LOR is located has an intersection with the target object based on prior information, and determine whether the response line LOR passes through the target object based on the number of intersections.

32. The time correction device according to claim 31, characterized in that The prior information includes the number of IPs of the scintillation crystals spaced between the scintillation crystals at both ends of the line of response (LOR). The number of IPs of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the line where the line of response (LOR) is located.

33. The time correction device according to claim 28, characterized in that The activity image reconstruction module is configured to reconstruct the activity image using filtered back projection or an iterative method.

34. The time correction device according to claim 28, characterized in that The pixel value-time difference statistical distribution acquisition module is configured to acquire the pixel points Pi where the selected response lines LORi intersect with the activity image based on a ray tracing method.

35. The time correction device according to claim 34, characterized in that The pixel value-time difference statistical distribution acquisition module includes: The pixel time difference acquisition module is used to calculate the time difference between the pixel point Pi and the two end points of the corresponding response line LORi one by one, and record the pixel value of each pixel point Pi; A pixel value accumulation module is used to determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pi, calculate the accumulated value of the pixel values ​​of the pixel points Pi whose time difference falls within each time difference interval; The pixel value-time difference statistical distribution acquisition module is configured to use the time difference interval as the horizontal axis step and the cumulative value of the pixel values ​​of the pixel points falling into each step as the vertical axis to obtain the pixel value-time difference statistical distribution Ti corresponding to each response line LORi.

36. The time correction device according to claim 35, characterized in that The event-time difference statistical distribution acquisition module is configured to: The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Ti, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mi corresponding to each response line LORi is obtained.

37. The time correction device according to claim 28, characterized in that The time correction value acquisition module is further configured to calculate the time correction value based on the time deviation difference δ △ i Obtain the relationship between the time deviations δci and δdi of the scintillator crystals ci and di at both ends of each response line LORi, δci-δdi=δ △ i; simultaneous equations and obtain the time deviations δci and δdi of the scintillation crystals ci and di at both ends of each response line LORi by fitting method, wherein the time deviations δci and δdi are the time correction values ​​of the scintillation crystals ci and di.

38. The time correction device according to claim 28, characterized in that The time correction device further comprises a correction module, which is configured to correct the pulse signal time information in the sampled data based on the time correction value: the time data t corresponding to the scintillation crystals ci and di in the sampled data ci , t di Subtract the time correction values ​​δci and δdi respectively.

39. A time correction device, characterized in that: include: A first coincidence event screening module is configured to obtain, based on the sampled data of the target object, a response line LORi passing through the target object and a coincidence event Ki on each response line LORi, where i represents the number, i≥1; an activity image reconstruction module configured to acquire an activity image based on all coincident events of all response lines LORi passing through the target object; The second coincidence event screening module is configured to screen the response lines LORj whose number of coincidence events meets a preset reference value based on all the response lines LORi passing through the target object, where j is the number, j≥1; A pixel value-time difference statistical distribution acquisition module is configured to acquire each pixel point Pj where each selected response line LORj intersects with the activity image, and based on the pixel point Pj, respectively acquire the pixel value-time difference statistical distribution Tj corresponding to each response line LORj; A coincidence event-time difference statistical distribution acquisition module is configured to acquire a coincidence event-time difference statistical distribution Mj corresponding to each screened response line LORj; The calculation module is configured to calculate the maximum value Yj of the inner product of each pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and obtain the difference δ between each response line LORj and the time deviation corresponding to the maximum value △ j; A time correction value acquisition module is configured to obtain a time correction value based on the difference δ △ jGet the time correction value.

40. The time correction device according to claim 39, characterized in that The sampling data includes scintillation crystal number information and pulse signal time information; The coincidence event screening module is further configured to obtain energy information of the pulse signal based on the sampled data, obtain coincidence events based on time information and energy information of the pulse signal, and obtain the line of response (LOR) corresponding to the coincidence event based on the scintillation crystal number information.

41. The time correction device according to claim 40, characterized in that The time correction device also includes: The recording module is configured to record the time difference of the event and the corresponding scintillation crystal number information at both ends of the response line LOR.

42. The time correction device according to claim 39, characterized in that The first coincidence event screening module is configured to determine whether the line where the response line LOR is located has an intersection with the target object based on prior information, and determine whether the response line LOR passes through the target object based on the number of intersections.

43. The time correction device according to claim 42, characterized in that The prior information includes the number of IPs of the scintillation crystals spaced between the scintillation crystals at both ends of the line of response (LOR). The number of IPs of the spaced scintillation crystals is determined based on whether the inner diameter of the target object in each direction intersects the line where the line of response (LOR) is located.

44. The time correction device according to claim 39, characterized in that The activity image reconstruction module is configured to reconstruct the activity image using filtered back projection or an iterative method.

45. The time correction device according to claim 39, characterized in that The second matching event screening module includes: A benchmark value setting module is used to set a benchmark value for comparing the number of events; A determination module, used to determine whether the number of matching events is greater than a reference value; The storage module is used to store the response line LOR when the number of events is greater than the reference value.

46. ​​The time correction device according to claim 39, characterized in that The pixel value-time difference statistical distribution acquisition module is configured to acquire the pixel point Pj where the selected response line LORj intersects the activity image based on a ray tracing method.

47. The time correction device according to claim 46, characterized in that The pixel value-time difference statistical distribution acquisition module includes: The pixel time difference acquisition module is used to calculate the time difference between the pixel point Pj and the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj; A pixel value accumulation module is used to determine a number of equally spaced time difference intervals and, based on the time difference of each pixel point Pj, calculate the accumulated values ​​of the pixel values ​​of the pixel points Pj whose time differences fall within each time difference interval; The pixel value-time difference statistical distribution acquisition module is configured to use the time difference interval as the horizontal axis step and the cumulative value of the pixel values ​​of the pixel points falling into each step as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

48. The time correction device according to claim 39, characterized in that The event-time difference statistical distribution acquisition module is configured to The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Tj, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mj corresponding to each response line LORj is obtained.

49. The time correction device according to claim 39, characterized in that The time correction value acquisition module is further configured to calculate the time correction value based on the time deviation difference δ △ The relationship between the time deviations δcj and δdj of the scintillator crystals cj and dj at both ends of each response line LORj is δcj-δdj=δ △ j; a group of simultaneous equations and a fitting method is used to obtain the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj, wherein the time deviations δcj and δdj are the time correction values ​​of the scintillation crystals cj and dj.

50. The time correction device according to claim 39, characterized in that The time correction device further comprises a correction module, which is configured to correct the time information of the pulse signal in the sampled data based on the time correction value: the time data t corresponding to the scintillation crystals cj and dj in the sampled data cj , t dj Subtract the time correction values ​​δcj and δdj respectively.

51. A digitizing device, characterized in that: It includes a time correction device as described in any one of claims 28 to 50, the digitization equipment uses a detector to detect the object to be detected, uses a sampling module to obtain sampling data, uses the time correction device to correct the sampling data and obtain the corrected time data, thereby forming a digitized image based on the corrected time data.

52. A computer device, characterized in that include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the steps of the time correction method according to any one of claims 1 to 27 are implemented.

53. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and when the computer program is executed by the processor, the steps of the time correction method according to any one of claims 1 to 27 are implemented.

Images