Time calibration method, device, apparatus and computer-readable storage medium

Abstract

The present disclosure provides a time calibration method, device, apparatus, and computer-readable storage medium. The time calibration method includes the steps of: determining response lines passing through the object and coincidence events on each response line based on sampling data of the object; acquiring a radioactivity image, determining pixel points where each response line passing through the object intersects with the radioactivity image, and determining a pixel value-time difference statistical distribution corresponding to each response line based on the pixel points; determining a coincidence event-time difference statistical distribution corresponding to each response line based on the coincidence events on each response line; calculating the maximum value of the dot product of the pixel value-time difference statistical distribution and the coincidence event-time difference statistical distribution, and determining a time offset difference value Yi corresponding to the maximum value Yi of each response line; and determining a time calibration value based on the offset difference value. The present disclosure is widely applicable and does not require long-term sampling, thereby saving time and improving the efficiency of time calibration.

Description

[Technical Field]

[0001] This application claims priority from Chinese Patent Application No. 202211736267.8, filed on December 30, 2022, the entire contents of which are incorporated by reference.

[0002] The present disclosure relates to the field of data processing, and in particular to a time calibration method, device, apparatus, and computer-readable storage medium. [Background technology]

[0003] Positron Emission Tomography (PET) technology is currently one of the most advanced molecular imaging technologies worldwide. By imaging radionuclide-labeled compounds in vivo, PET can noninvasively, quantitatively, and dynamically evaluate the metabolic levels, biochemical reactions, and functional activities of various functional organs in the body, with high sensitivity and accuracy.

[0004] To obtain the distribution of positron-emitting nuclides in the human body, the detection principle of the PET system is that a positron is generated by the decay of a positron-emitting nuclide, and the positron annihilates with a surrounding electron to generate a pair of gamma photons with an energy of 511 keV in opposite directions. The two gamma photons are detected by two scintillation crystal rods in the PET detector. The line connecting the center planes of the two scintillator rods is called the line of response (LOR). When two scintillators located on the LOR in the detector detect two gamma photons within a specified coincidence time window (e.g., 0-15 nanoseconds), i.e., when the difference in the time information of the two gamma photons falls within the coincidence time window and the energy of both gamma photons falls within the coincidence energy window, the event of detecting the two gamma photons is called a coincidence event, and the event of detecting either gamma photon is called a single event.

[0005] As shown in Figure 1, if two gamma photons generated by an annihilation event are detected at point A (scintillator rod A) and point B (scintillator rod B) of the PET detector, respectively, the connecting line between A and B is called the line of response (LOR).

[0006] Theoretically, if the times tA and tB at which the detector's scintillation crystals A and B detect gamma photons are sufficiently accurate, the position D at which the annihilation occurs can be accurately determined. If the length of AB is L, the distance from point D to point A is d, and the speed of light is C, then d = L / 2 + C / 2*(tA - tB). In other words, through the arrival times of precisely collected gamma photons, the position of the nuclide annihilation can be directly calculated without the need for complex image reconstruction methods to obtain PET images.

[0007] However, in an actual system, due to differences in the materials of the scintillator rods in the detector, differences in optical path length, and differences in electronic timing, there is a background delay, or time difference, between the scintillator rods, and the actual detection times at points A and B are tA' and tB', where tA' = tA + δA and tB' = tB + δB, where δA and δB are the time offsets of scintillator rod A and scintillator rod B, respectively. Considering the existence of the time offsets, the distance from A to the radionuclide annihilation position calculated based on tA' and tB' is d' = L / 2 + C / 2 * (tA' - tB') = d + C / 2 * (δA - δB), d = d'-C / 2 * (δA - δB) = L / 2 + C / 2 * (tA' - tB') - C / 2 * (δA - δB), i.e. the obtained nuclide annihilation position is offset from the actual annihilation position D.

[0008] To obtain the accurate annihilation position, a time calibration needs to be performed on the time data detected by the scintillator.

[0009] Typically, the time offsets δ1 to δn between the actual measured time values ​​and the theoretical arrival times of gamma photons for all n scintillation crystal bars in the detector are obtained, and these offset values ​​are used to calibrate the actually obtained time information; this process is called time offset calibration, i.e., scintillator time calibration. Therefore, the crucial task in the time calibration process is to obtain the time offsets δ1 to δn between the actual measured time values ​​and the theoretical arrival times of gamma photons for all scintillator bars.

[0010] In prior art time calibration methods, it is necessary to characterize the time offsets of the scintillation crystals at both ends of the LOR to obtain the time offsets δ1 to δn between the actual measured time values ​​for the scintillator bars and the theoretical arrival times of gamma photons. Today, the time offsets of the scintillation crystals at both ends of an LOR are typically characterized based on the time difference between coincidence events corresponding to that LOR. However, theoretically, when characterizing the difference in the time offsets of the scintillation crystals at both ends of an LOR for gamma rays emitted by different objects, different methods for obtaining the average time difference between coincidence events corresponding to the LOR are used, and various methods cannot be universally used for different objects. For example, when a target object with a uniform shape (such as a small cylinder or a linear radiation source) is used, the average sum of the time differences of all coincidence counting events on the LOR may be used as the average time difference of the coincidence counting events corresponding to the LOR. Currently, in the case of a target object with a circular ring shape (such as a shell radiation source target object formed by rotating a linear radiation source once or an object similar to a shell radiation source), when both the radioactivity and the shape of the target object are uniform, the average sum of the time differences of all coincidence counting events on the LOR may be used as the average time difference of the coincidence counting events corresponding to the LOR. When the radioactivity and the shape of the target object are not uniform, the average sum of the time differences of all coincidence counting events on the LOR may be used as the average time difference of the coincidence counting events corresponding to the LOR. The average sum of the time differences of all coincidence counting events on an OR cannot be used as the average time difference of the coincidence counting events corresponding to that LOR. Usually, the average sum of the time differences corresponding to each annihilation position can be obtained as the average time difference of the coincidence counting events corresponding to that LOR through Gaussian fitting. The Gaussian fitting method requires a very long acquisition time of at least one hour to collect enough counts from the target object, which is too long to collect, or requires a very high drug radioactivity. However, high drug radioactivity will cause more accidental events and increase measurement errors.

[0011] In summary, current time calibration methods have the following deficiencies when characterizing the difference in time offsets between the scintillation crystal rods at both ends of the LOR to obtain the time offsets δ1 to δn between the actual measured time values ​​and the theoretical gamma photon arrival times for the scintillator rods: For gamma rays originating from different target objects, the methods for characterizing the difference in time offsets between the scintillator rods at both ends of the LOR are different, and various methods cannot be used universally. There is no standardized method for characterizing the difference in time offsets between the scintillator rods at both ends of the LOR. Some methods are time-consuming and produce results with large errors.

[0012] The discussion of the background art is provided merely to aid in understanding the context of the present disclosure and is not admitted to be prior art. Summary of the Invention [Problem to be solved by the invention]

[0013] The present disclosure aims to provide a time calibration method, device, apparatus, and computer-readable storage medium that can solve at least one problem existing in the prior art. [Means for solving the problem]

[0014] According to a first aspect of the present disclosure, there is provided a time calibration method, the time calibration method including the steps of: determining lines of response (LORi) passing through the object and coincidence events K on each LORi based on sampling data of the object, where i represents a number and i≧1; and generating a radioactivity image (a radioactivity image) based on all the coincidence events of all lines of response LORi passing through the object. the step of acquiring a line of response (LORi) of interest (image), determining pixel points Pi at which each line of response (LORi) passing through the object intersects with the radioactivity image, and determining a pixel value-time difference statistical distribution Ti corresponding to each line of response (LORi) based on the pixel points Pi; determining a coincidence event-time difference statistical distribution Mi corresponding to each line of response (LORi) based on coincidence events Ki on each line of response (LORi); calculating a maximum value Yi of the dot product of the pixel value-time difference statistical distribution Ti and the coincidence event-time difference statistical distribution Mi based on the pixel value-time difference statistical distribution Ti and the coincidence event-time difference statistical distribution Mi, and determining a time offset difference value δΔi corresponding to the maximum value Yi of each line of response (LORi); and determining a time calibration value based on the offset difference value δΔi.

[0015] According to one embodiment of the present disclosure, the response lines LORi passing through the target object include response lines LORi that have at least one intersection with the target object, or response lines LORi that circumscribe the target object or intersect the target object.

[0016] According to one embodiment of the present disclosure, the step of determining lines of response (LORi) passing through the object and coincidence events Ki on each LORi based on sampling data of the object includes the steps of determining all coincidence events and lines of response LOR corresponding to each coincidence event based on the sampling data, and sorting all lines of response LORi passing through the object and coincidence events Ki on each LORi.

[0017] According to one embodiment of the present disclosure, the step of selecting all response lines LORi passing through the target object and coincidence events Ki on each LORi includes a step of determining, based on prior information, whether the straight line on which the response line LOR exists has an intersection with the target object.

[0018] According to one embodiment of the present disclosure, the prior information includes the number of scintillators IP between the spaced apart scintillators at the two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects with the straight line on which the line of response LOR exists.

[0019] According to one embodiment of the present disclosure, the step of acquiring a radioactivity image based on all coincidence count events of all LORi passing through the target object includes the step of reconstructing a radioactivity image based on all coincidence count events on all response lines LORi passing through the target object using a filtered back projection or iterative method.

[0020] According to one embodiment of the present disclosure, the step of determining pixel points Pi at which each LORi passing through the target object intersects with the radioactivity image includes the step of determining pixel points Pi at which each selected response line LORi intersects with the radioactivity image based on a ray tracing method.

[0021] According to one embodiment of the present disclosure, the step of determining the pixel value-time difference statistical distribution Ti corresponding to each LORi based on each pixel point Pi includes the steps of: calculating, for each pixel point Pi, the time difference from each pixel point Pi to the end point of the corresponding response line LORi and recording the pixel value of each pixel point Pi; determining a plurality of equally spaced time difference intervals and accumulating the pixel values ​​of pixel points Pi whose time differences fall within each time difference interval based on the time difference of each pixel point Pi; and determining the pixel value-time difference statistical distribution Ti corresponding to each response line LORi by using the time difference interval as the horizontal axis step size and the accumulated pixel values ​​of pixel points falling within each step size as the vertical axis.

[0022] According to one embodiment of the present disclosure, the step of determining the coincidence count event-time difference statistical distribution Mi corresponding to each LORi based on the coincidence count events Ki on each response line LORi includes the step of determining the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Ti as the step size, and determining the coincidence count event-time difference statistical distribution Mi corresponding to each response line LORi by setting the vertical axis as the cumulative value of the coincidence count events whose time differences fall within each step size.

[0023] According to one embodiment of the present disclosure, the step of calculating the maximum value Yi of the dot product of the pixel value-time difference statistical distribution Ti and the coincidence counting event-time difference statistical distribution Mi, and determining the time offset difference value δΔi corresponding to the maximum value Yi of each response line LORi, includes the steps of using the pixel value-time difference statistical distribution Ti as a reference to shift the coincidence counting event-time difference statistical distribution Mi, calculating the dot product of the pixel value-time difference statistical distribution Ti and the coincidence counting event-time difference statistical distribution Mi, and statistically obtaining the shift amount of the coincidence counting event-time difference statistical distribution Mi when the maximum value Yi of the dot product is reached, where the shift amount is the offset difference value δΔi.

[0024] According to one embodiment of the present disclosure, the step of determining a time calibration value based on the offset difference value δΔi includes the steps of determining a relationship between the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi based on the time offset difference value δΔi, where δci - δdi = δΔi, and determining the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi by solving a system of equations using a fitting method, where the time offsets δci and δdi are the time calibration values ​​of the scintillators ci and di.

[0025] According to one embodiment of the present disclosure, the time calibration method further includes a step of performing time calibration on the sampling data based on the determined time calibration value, i.e., a step of performing calibration on the time data corresponding to scintillators c i and di in the sampling data based on the time offsets δ c i and δ di of the scintillators c i and di.

[0026] According to one embodiment of the present disclosure, the step of performing time calibration on the sampling data based on the determined time calibration values ​​includes a step of subtracting the time calibration values ​​δci and δdi from the time data tci and tdi corresponding to the scintillators ci and di in the sampling data, respectively.

[0027] According to a second aspect of the present disclosure, there is provided a time calibration method, which includes the steps of: determining response lines LORi passing through the object and coincidence count events Ki on each LORi based on sampling data of the object, where i represents a number and i≧1; acquiring a radioactivity image based on all the coincidence count events of all response lines LORi passing through the object; selecting response lines LORj whose number of coincidence count events satisfies a preset condition based on all response lines LORi passing through the object, where j represents a number and j≧1; and determining whether each selected response line LORj intersects with the radioactivity image. determining a pixel point Pj corresponding to each selected response line LORj based on the pixel point Pj, and determining a pixel value-time difference statistical distribution Tj corresponding to each selected response line LORj based on the pixel point Pj; determining a coincidence event-time difference statistical distribution Mj corresponding to each selected response line LORj; calculating a maximum value Yj of the dot product of the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj based on the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each selected response line LORj, and determining a time offset difference value δΔj corresponding to the maximum value Yj of each response line LORj; and determining a time calibration value based on the offset difference value δΔj.

[0028] According to one embodiment of the present disclosure, the response lines LORi passing through the target object include response lines LORi that have at least one intersection with the target object, or response lines LORi that circumscribe the target object or intersect the target object.

[0029] According to one embodiment of the present disclosure, the step of determining LORi passing through the target object and coincidence count events Ki on each LORi based on the sampling data includes the steps of determining all coincidence count events and response lines LOR corresponding to each coincidence count event based on the sampling data, and sorting all response lines LORi passing through the target object and coincidence count events Ki on each LORi.

[0030] According to one embodiment of the present disclosure, the step of selecting all response lines LORi passing through the target object and coincidence events Ki on each LORi includes a step of determining, based on prior information, whether the straight line on which the response line LOR exists has an intersection with the target object.

[0031] According to one embodiment of the present disclosure, the prior information includes the number of scintillators IP between the spaced apart scintillators at the two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects with the straight line on which the line of response LOR exists.

[0032] According to one embodiment of the present disclosure, the step of acquiring a radioactivity image based on all coincidence count events of all LORi passing through the target object includes the step of reconstructing a radioactivity image based on all coincidence count events on all response lines LORi passing through the target object using a filtered back projection or iterative method.

[0033] According to one embodiment of the present disclosure, the step of selecting, based on all response lines LORi passing through the target object, response lines LORj whose number of coincidence counting events satisfies a preset condition includes the steps of setting a reference value for comparing the number of coincidence counting events, determining whether the number of coincidence counting events is greater than the reference value, and storing response lines LORj whose number of coincidence counting events is greater than the reference value.

[0034] According to one embodiment of the present disclosure, the step of determining pixel points Pj where each selected response line LORj intersects with the radioactivity image includes the step of determining pixel points Pj where each response line LORj intersects with the radioactivity image based on a ray tracing method.

[0035] According to one embodiment of the present disclosure, the step of determining the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on each pixel point Pj includes the steps of: calculating, for each pixel point Pj, the time difference from each pixel point Pj to the end point of the corresponding response line LORj and recording the pixel value of each pixel point Pj; determining a plurality of equally spaced time difference intervals and accumulating the pixel values ​​of the pixel points Pj whose time differences fall within each time difference interval based on the time difference of each pixel point Pj; and determining the pixel value-time difference statistical distribution Tj corresponding to each response line LORj by using the time difference interval as the horizontal axis step size and the accumulated pixel values ​​of the pixel points that fall within each step size as the vertical axis.

[0036] According to one embodiment of the present disclosure, the step of determining the coincidence counting event-time difference statistical distribution Mj corresponding to each selected response line LORj includes determining the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and determining the coincidence counting event-time difference statistical distribution Mj corresponding to each response line LORj by setting the vertical axis as the cumulative value of the coincidence counting events whose time difference falls within each step size.

[0037] According to one embodiment of the present disclosure, the step of calculating the maximum value Yj of the dot product between the pixel value-time difference statistical distribution Tj and the coincidence counting event-time difference statistical distribution Mj and determining the time offset difference value δΔj corresponding to the maximum value of each response line LORj includes the steps of using the pixel value-time difference statistical distribution Tj as a reference to shift the coincidence counting event-time difference statistical distribution Mj, calculating the dot product of the pixel value-time difference statistical distribution Tj and the coincidence counting event-time difference statistical distribution Mj, and statistically obtaining the shift amount of the coincidence counting event-time difference statistical distribution Mj when the maximum value Yj of the dot product is reached, where the shift amount is the offset difference value δΔj.

[0038] According to one embodiment of the present disclosure, the step of determining the time calibration value based on the offset difference value δΔj includes the steps of determining a relationship between the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each response line LORj based on the time offset difference value δΔj, where δcj - δdj = δΔj, and determining the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each response line LORj by solving a system of equations using a fitting method, where the time offsets δcj and δdj are the time calibration values ​​of the scintillators cj and dj.

[0039] According to one embodiment of the present disclosure, the time calibration method further includes a step of performing time calibration on the sampling data based on the determined time calibration value, i.e., a step of performing calibration on the time data corresponding to scintillators cj and dj in the sampling data based on the time offsets δcj and δdj of scintillators cj and dj.

[0040] According to one embodiment of the present disclosure, the step of performing time calibration on the sampling data based on the determined time calibration values ​​includes a step of subtracting the time calibration values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillators cj and dj in the sampling data, respectively.

[0041] According to a third aspect of the present disclosure, there is provided a time calibration device, the time calibration device including: a coincidence event sorting module configured to determine, based on sampling data of the target object, lines of response LORi passing through the target object and coincidence events Ki on each LORi, where i represents a number and i≧1; a radioactivity image reconstruction module configured to acquire a radioactivity image based on all the coincidence events of all lines of response LORi passing through the target object; and a radioactivity image reconstruction module configured to determine pixel points Pi at which each line of response LORi passing through the target object intersects with the radioactivity image, and The system includes a pixel value-time difference statistical distribution acquisition module configured to determine a pixel value-time difference statistical distribution Ti corresponding to each LORi, a coincidence counting event-time difference statistical distribution acquisition module configured to determine a coincidence counting event-time difference statistical distribution Mi corresponding to each response line LORi, a calculation module configured to calculate the maximum value Yi of the dot product of the pixel value-time difference statistical distribution Ti and the coincidence counting event-time difference statistical distribution Mi and determine a time offset difference value δΔi corresponding to the maximum value Yi of each response line LORi, and a time calibration value acquisition module configured to determine a time calibration value based on the offset difference value δΔi.

[0042] According to one embodiment of the present disclosure, the sampling data includes scintillator IP information and time information of the pulse signal, and the coincidence event selection module is further configured to determine energy information of the pulse signal based on the sampling data, determine coincidence events based on the time information and energy information of the pulse signal, and determine response lines LOR corresponding to the coincidence events based on the scintillator IP information.

[0043] According to an embodiment of the present disclosure, the time calibration device further comprises a recording module configured to record the time difference of the coincidence counting events and the scintillator IP information of the scintillators at the two ends of the corresponding response line LOR.

[0044] According to one embodiment of the present disclosure, the coincidence counting event sorting module is further configured to determine, based on prior information, whether the straight line on which the response line LOR exists has an intersection with the target object, and to determine, based on the number of intersections, whether the response line LOR passes through the target object.

[0045] According to one embodiment of the present disclosure, the prior information includes the number of scintillators IP between the spaced apart scintillators at the two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects with the straight line on which the line of response LOR exists.

[0046] According to an embodiment of the present disclosure, the radiological image reconstruction module is configured to reconstruct the radiological image using filtered backprojection or an iterative method.

[0047] According to an embodiment of the present disclosure, the pixel value-time difference statistical distribution acquisition module is configured to determine the pixel points Pi where the selected response lines LORi intersect with the radioactivity image based on a ray tracing method.

[0048] According to one embodiment of the present disclosure, the pixel value-time difference statistical distribution acquisition module includes: a pixel point time difference acquisition module configured to calculate the time difference from each pixel point Pi to the end point of the corresponding response line LORi and record the pixel value of each pixel point Pi; and a pixel value accumulation module configured to determine a plurality of equally spaced time difference intervals and accumulate pixel values ​​of pixel points Pi whose time differences fall within each time difference interval based on the time difference of each pixel point Pi, and the pixel value-time difference statistical distribution acquisition module is configured to determine a pixel value-time difference statistical distribution Ti corresponding to each response line LORi by taking the time difference interval as the horizontal axis step size and the accumulated pixel values ​​of pixel points that fall within each step size as the vertical axis.

[0049] According to one embodiment of the present disclosure, the coincidence counting event-time difference statistical distribution acquisition module is configured to determine the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Ti as the step size, and to determine the coincidence counting event-time difference statistical distribution Mi corresponding to each response line LORi by setting the vertical axis as the cumulative value of the coincidence counting events whose time differences fall within each step size.

[0050] According to an embodiment of the present disclosure, the time calibration value acquisition module is further configured to determine a relationship between the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi based on the time offset difference value δΔi, where δci - δdi = δΔi, and to determine the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi by solving a simultaneous equation using a fitting method, where the time offsets δci and δdi are the time calibration values ​​of the scintillators ci and di.

[0051] According to one embodiment of the present disclosure, the time calibration device further comprises a calibration module configured to perform time calibration on time information of the pulse signal in the sampling data based on the determined time calibration value, and performing the time calibration includes subtracting the time calibration values ​​δci and δdi from time data tci and tdi corresponding to scintillators ci and di, respectively, in the sampling data.

[0052] According to a fourth aspect of the present disclosure, there is provided a time calibration device, the time calibration device including: a first coincidence event sorting module configured to determine response lines LORi passing through the object and coincidence events K on each LORi based on sampling data of the object, where i represents a number and i≧1; a radioactivity image reconstruction module configured to acquire a radioactivity image based on all the coincidence events of all the response lines LORi passing through the object; and a second coincidence event sorting module configured to sort response lines LORj whose number of coincidence events meets a preset reference value based on all the response lines LORi passing through the object, where j represents a number and j≧1. a pixel value-time difference statistical distribution acquisition module configured to determine pixel points Pj where each selected response line LORj intersects with the radioactivity image and to determine a pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel points Pj; a coincidence counting event-time difference statistical distribution acquisition module configured to determine a coincidence counting event-time difference statistical distribution Mj corresponding to each selected response line LORj; a calculation module configured to calculate a maximum value Yj of an inner product between the pixel value-time difference statistical distribution Tj and the coincidence counting event-time difference statistical distribution Mj and to determine a time offset difference value δΔj corresponding to the maximum value Yj of each response line LORj; and a time calibration value acquisition module configured to determine a time calibration value based on the offset difference value δΔj.

[0053] According to one embodiment of the present disclosure, the sampling data includes scintillator IP information and time information of the pulse signal, and the coincidence event selection module is further configured to determine energy information of the pulse signal based on the sampling data, determine coincidence events based on the time information and energy information of the pulse signal, and determine response lines LOR corresponding to the coincidence events based on the scintillator IP information.

[0054] According to an embodiment of the present disclosure, the time calibration device further comprises a recording module configured to record the time difference of the coincidence counting events and the scintillator IP information of the scintillators at the two ends of the corresponding response line LOR.

[0055] According to one embodiment of the present disclosure, the first coincidence counting event sorting module is configured to determine, based on prior information, whether the straight line on which the response line LOR exists has an intersection with the target object, and to determine, based on the number of intersections, whether the response line LOR passes through the target object.

[0056] According to one embodiment of the present disclosure, the prior information includes the number of scintillators IP between the spaced apart scintillators at the two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects with the straight line on which the line of response LOR exists.

[0057] According to an embodiment of the present disclosure, the radiological image reconstruction module is configured to reconstruct the radiological image using filtered backprojection or an iterative method.

[0058] According to one embodiment of the present disclosure, the second coincidence counting event sorting module includes a reference value setting module configured to set a reference value for comparing the number of coincidence counting events, a determination module configured to determine whether the number of coincidence counting events is greater than the reference value, and a storage module configured to store a response line LOR where the number of coincidence counting events is greater than the reference value.

[0059] According to an embodiment of the present disclosure, the pixel value-time difference statistical distribution acquisition module is configured to determine the pixel points Pj where the selected response lines LORj intersect with the radioactivity image based on a ray tracing method.

[0060] According to one embodiment of the present disclosure, the pixel value-time difference statistical distribution acquisition module includes a pixel time difference acquisition module configured to calculate the time difference from each pixel point Pj to the end point of the corresponding response line LORj and record the pixel value of each pixel point Pj; and a pixel value accumulation module configured to determine a plurality of equally spaced time difference intervals and accumulate pixel values ​​of pixel points Pj whose time differences fall within each time difference interval based on the time difference of each pixel point Pj, and the pixel value-time difference statistical distribution acquisition module is configured to determine a pixel value-time difference statistical distribution Tj corresponding to each response line LORj by using the time difference interval as the horizontal axis step size and the accumulated pixel values ​​of pixel points falling within each step size as the vertical axis.

[0061] According to one embodiment of the present disclosure, the coincidence counting event-time difference statistical distribution acquisition module is configured to determine the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and to determine the coincidence counting event-time difference statistical distribution Mj corresponding to each response line LORj by setting the vertical axis as the cumulative value of the coincidence counting events whose time difference falls within each step size.

[0062] According to an embodiment of the present disclosure, the time calibration value acquisition module is further configured to determine a relationship between the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each response line LORj based on the time offset difference value δ△j, where δcj - δdj = δ△j, and to determine the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each response line LORj by solving the simultaneous equations using a fitting method, where the time offsets δcj and δdj are the time calibration values ​​of the scintillators cj and dj.

[0063] According to one embodiment of the present disclosure, the time calibration device further comprises a calibration module configured to perform time calibration on time information of the pulse signal in the sampling data based on the determined time calibration value, and performing the time calibration includes subtracting the time calibration values ​​δci and δdi from time data tci and tdi corresponding to scintillators ci and di, respectively, in the sampling data.

[0064] According to a fifth aspect of the present disclosure, there is provided a digitization apparatus comprising the above-mentioned time calibration device, wherein the digitization apparatus detects an object to be detected using a detector, obtains sampling data using a sampling module, calibrates the sampling data using the time calibration device, obtains calibrated time data, and thereby forms a digital image based on the calibrated time data.

[0065] According to a sixth aspect of the present disclosure, there is provided a computer device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor to perform the steps of the time calibration method described above.

[0066] According to a seventh aspect of the present disclosure, there is provided a computer-readable storage medium, which stores a computer program executable by a processor to perform the steps of the time calibration method set forth above.

[0067] The solution disclosed herein 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 selected genuine coincidence events passing through the target object, calculates the maximum value Yi of the dot product of each Ti and Mi, obtains the time offset difference δΔi corresponding to the maximum value of each response line LORi, and then obtains a time calibration value based on δΔi, thereby being applicable to any shell source, having a wide range of applications, and not requiring Gaussian fitting, thereby saving time, improving the efficiency of time calibration, and eliminating the need for high-activity pharmaceuticals.

[0068] In addition, in the embodiment of the present disclosure, 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 based on selected genuine coincidence events that pass through the target object and correspond to the response line LORj where the number of coincidence events on it meets a preset condition, which further eliminates random events and scattered events and accordingly further improves the accuracy of the obtained difference δΔj of the time offset corresponding to each response line LORj, thereby further improving the accuracy of the time calibration.

[0069] Optional features and further advantages of the embodiments are described in part below, and others can be understood by reading this specification. [Brief explanation of the drawings]

[0070] Embodiments of the present application will now be described in more detail with reference to the accompanying drawings, in which elements shown are not necessarily drawn to scale, and in which like or identical reference numerals represent like or identical elements. [Figure 1] FIG. 1 is a schematic diagram of the annihilation position shift according to the prior art. [Figure 2] 1 is a flowchart of a time calibration method according to one embodiment of the present disclosure. [Figure 3] 10 is a flowchart of a time calibration method according to another embodiment of the present disclosure. [Figure 4] FIG. 1 is an exemplary module diagram of a time calibration device according to one embodiment of the present disclosure. [Figure 5] FIG. 10 is an exemplary module diagram of a time calibration device according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0071] In order to clarify the objectives, technical solutions and advantages of the present invention, the following detailed description is provided in conjunction with specific embodiments and accompanying drawings. It should be noted that the following exemplary embodiments and descriptions of the present invention are provided for the purpose of explaining the present invention, and are not intended to limit the scope of the present invention.

[0072] In this disclosure, the word "comprise" and variations thereof are intended to be inclusive, i.e., mean "include," but are not limited to. Unless otherwise specified, the word "or" means "and / or." The word "based on" means "based at least in part on." The words "exemplary embodiment" and "one embodiment" mean "at least one exemplary embodiment." The word "another embodiment" means "at least one additional embodiment." The words "first," "second," etc. may refer to different or the same object. Other explicit and implicit definitions may be referenced below.

[0073] Hereinafter, specific embodiments of the present application will be described in detail with reference to the accompanying drawings. Please note that the following description is for illustrative purposes only and is not intended to limit the scope of protection of the present disclosure.

[0074] 2 is an exemplary flowchart of a time calibration method according to some embodiments of the present disclosure. Specifically, as shown in FIG. 2, the time calibration method may include the following steps S120, S130, S140, S150, and S160.

[0075] When the method starts to be executed, step S110 may be executed first, that is, sampling the pulse signal acquired based on the target object to obtain sampling data.

[0076] In embodiments of the present disclosure, the target object may include a phantom and / or a living body, and a simulated radiation source. Specifically, the phantom and / or living body may include, but is not limited to, an animal body, and the simulated radiation source may include, but is not limited to, a small cylinder (which may have a diameter of less than 20 mm), a linear source, a shell source, or a radiation source similar to a shell source, and may also be a simulated radiation source of a regular or irregular shape.

[0077] In embodiments of the present disclosure, sampled data is broadly interpreted to include detected data obtained from a physical object and / or generated simulated data.

[0078] In an embodiment of the present disclosure, the detection data may be obtained by detecting a physical object, and the detection data is obtained by a detection module. The detection module may be a detection module of various medical imaging devices such as PET, CT, and MR. The detection module includes a detector having a scintillator and a photoelectric conversion element.

[0079] In one example of the present disclosure, the detection module can be a PET detection module, and the detector of the module includes a scintillator and a photoelectric conversion element, the scintillator including, but not limited to, a lutetium yttrium silicate scintillator used to convert gamma rays into visible light, and the photoelectric conversion element including, but not limited to, a silicon photomultiplier (SiPM) used to convert the visible light into a pulse signal.

[0080] In the embodiments of the present disclosure, a pulse signal should be understood to mean any pulse signal that can be sampled. It is essentially a physical quantity that suddenly changes within a short period of time and then rapidly returns to its initial value, and this physical quantity has specific characteristics. In the present disclosure, the pulse signal specifically includes a scintillation pulse, and in many embodiments, a scintillation pulse is used as an example, where the terms "pulse signal" and "scintillation pulse" may be used interchangeably. For example, in some embodiments, a scintillation pulse typically has a rising edge and a falling edge, which may be represented by a functional model. In some embodiments, the pulse signal is a scintillation pulse signal. For example, a scintillation pulse corresponding to a gamma photon typically exhibits a relatively fast rising edge and a relatively slow falling edge. The rising edge may be characterized by a linear function, and the falling edge may be characterized by an exponential function.

[0081] In other embodiments, the waveform of the pulse signal may be represented as a triangle wave, a square wave, a sine wave, a cosine wave, or some other shape of wave, which will not be repeated here.

[0082] In an embodiment of the present disclosure, the form of the pulse signal may be an electrical pulse signal, and the corresponding characteristics may be the voltage and current of the electrical pulse signal.

[0083] In an embodiment of the present disclosure, sampling of a pulse signal acquired based on a radiation source is realized by a sampling module. In one example of the present disclosure, 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 converter module, and an information storage module. The threshold setting module is used to set a sampling threshold, the comparison module is used to compare the pulse signal with a threshold and output a transition signal, the time-to-digital converter module is used to perform time sampling on the transition signal to obtain time information of the pulse signal, and the information storage module stores scintillator identification position information of the detection module and time information of the pulse signal. The sampling of the pulse signal by the MVT sampling module is implemented based on an FPGA chip incorporating a DAC, an LVDS, and a 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 presets thresholds for the LVDS, such as voltage thresholds V1, V2, V3, and V4. The input pulse signal is compared with thresholds V1 to V4 in the LVDS, and sampling is performed at moments t1 to t4 corresponding to the rising edges of the transition signals and moments t5 to t8 corresponding to the falling edges of the transition signals to obtain sampling data including voltage-time pairs (V1, t1), (V2, t2), (V3, t3), (V4, t4), (V4, t5), (V3, t6), (V2, t7), (V1, t8), where t1 to t8 are time data.

[0084] In an embodiment of the present disclosure, the sampling data includes scintillator identification position information of the detection module and time information of the pulse signal, among which the time data t1 may characterize the time information of the pulse signal, and the scintillator identification position information of the detection module may be determined based on the time data t1 to t4 of the pulse signal.

[0085] In an embodiment of the present disclosure, the voltage-time pairs (V1, t1), (V2, t2), (V3, t3), (V4, t4), (V4, t5), (V3, t6), (V2, t7), and (V1, t8) in the sampling data are later used for fitting and reconstructing a pulse waveform, and the energy information of the pulse signal is obtained by integration based on the reconstructed pulse waveform. Then, based on the time information and energy information of the pulse signal, coincidence counting events are selected. Based on the LOR of the selected coincidence counting events and the time information of the pulse signal, the position information of a gamma photon single event can be determined. It can be seen that the accuracy of the time data affects the accuracy of the coincidence counting event selection and the position information of the single event, i.e., the accuracy of the annihilation position.

[0086] In embodiments of the present disclosure, the simulation data may be, for example, generated simulation data, which may be obtained, for example, from simulation software or a simulation module. The simulation software or module may be, for example, simulation software or a simulation module for simulating medical imaging equipment and its detection instruments. The simulation software or module may include a simulation detection module, such as a simulation PET detection module. In a particular example, the sampling data may be obtained from simulation software for simulating a PET scan. In some embodiments, the target object may comprise a simulated target object.

[0087] In one example of the present disclosure, a target object (such as a shell source, a line source, or a cylindrical radiation source) is placed at the center of the FOV (field of view), and sampling is performed using the MVT method, with an acquisition time of 10 minutes or more to acquire the sampling data.

[0088] Step S120: Based on the sampling data of the target object, response lines LORi (i≧1) passing through the target object and coincidence events Ki (i≧1) on each LORi are determined.

[0089] In one embodiment, step S120 may specifically include:

[0090] S121: Based on the sampling data, all coincidence counting events and the LOR corresponding to each coincidence counting event are determined.

[0091] In the embodiment of the present disclosure, a coincidence event refers to two single events corresponding to two pulse signals, the time difference (i.e., the difference between the time information of the two pulse signals) being within the coincidence time window and the energy information being within the coincidence energy window. Specifically, taking the detection of gamma rays using a PET detector as an example, when two gamma photons generated by an annihilation reaction are detected by the scintillators of the two detectors, and the time difference between the time information of the two gamma photons is within a preset coincidence time window and the energy information of the two gamma photons is both within a preset coincidence energy window, the event of detecting these two gamma photons can be referred to as a coincidence event. The coincidence time window and the coincidence energy window in the embodiment of the present disclosure may be determined based on prior information.

[0092] In some embodiments, after acquiring the sampling data, it may acquire all coincidence counting events and LORs corresponding to each coincidence counting event based on the sampling data. Specifically, the sampling data may be sent to a host computer, and the host computer may fit and reconstruct a pulse waveform based on the sampling data. By integrating the reconstructed pulse waveform, the host computer obtains energy information of the pulse signal corresponding to each single event. Meanwhile, the host computer may determine scintillator identification position information of the detection module, i.e., scintillator IP number (e.g., scintillators are numbered 1 to n), and time information of the pulse signal based on the time data of the pulse signal.

[0093] In an embodiment of the present disclosure, a coincidence time window and a coincidence energy window are preset in a coincidence module of a host computer. Based on the time information and energy information of the pulse signal acquired from the sampling data, coincidence is performed on a single event corresponding to the pulse signal to determine the coincidence event. A recording module is also set in the host computer, and this recording module records the time difference of the coincidence event and the scintillator IP information of the two scintillators. The line connecting the centers of the surfaces of the two scintillators is the LOR corresponding to the coincidence event.

[0094] In one example, in the coincidence module of the host computer, the coincidence time window is set to 4 ns and the coincidence energy window is set to 420 keV to 1000 keV. An annihilation reaction generates two gamma photons, γ1 and γ2. Based on the sampling data, the host computer determines that the time information of the pulse signal corresponding to the single event γ1 detected by scintillator G with IP number 6 (for example, a PET detector with 48 scintillators) is t1, and the time information of the pulse signal corresponding to the single event γ2 detected by scintillator H with IP number 30 is t1'. The time difference is Δt = t1 - t1'. If Δt ≦ 4 ns, the time difference between the two single events is within the coincidence time window. The host computer fits and reconstructs the pulse waveforms of the two single events, and obtains the energy information e1 of the single event γ1 and the energy information e2 of the single event γ2 by integration, respectively. If both e1 and e2 are within the range of 420 keV to 1000 keV, the energy information of the two single events falls within the coincidence time window. In this case, the single events γ1 and γ2 are a pair of coincidence events, and the line connecting the centers of the surfaces of scintillators G and H is the LORGH corresponding to this coincidence event. The recording module of the host computer records the time difference of the coincidence events, which is Δt = t1 - t1', the scintillator IP information 6 and 30 of scintillators G and H, and the corresponding LOR, i.e., the line connecting the centers of the surfaces of G and H.

[0095] Similarly, in an embodiment of the present disclosure, it may determine all coincidence events and corresponding LORs based on the sampling data received by the host computer.

[0096] In one embodiment of the present disclosure, when multiple pairs of coincidence events correspond to the same LOR, the number of coincidence events on that LOR and the time difference between each of the coincidence events on the LOR are counted. Continuing with the above example, if there are 20 pairs of coincidence events that all correspond to the LORGH, the time difference information Δt1 to Δt20 of the 20 pairs of coincidence events on the LORGH are counted, and the number of coincidence events (20), the time differences Δt1 to Δt20 between each of the coincidence events, scintillator IP information 6 and 30 of scintillators G and H, and the corresponding LOR, i.e., the line connecting the centers of the surfaces of G and H, are recorded in the recording module.

[0097] In one example of the present disclosure, the host computer acquires time information and energy information of all pulse signals based on the sampling data, and based on a preset coincidence time window and a coincidence energy window, sorts all coincidence events, and records the time differences of all coincidence events, scintillator IP information, and LORs corresponding to all coincidence events, thereby facilitating subsequent sorting of all LORs passing through the target object (such as a simulated radiation source) and all coincidence events corresponding to each LOR.

[0098] S122: All response lines LORi passing through the target object and coincidence events K i on each LORi are selected.

[0099] In an embodiment of the present disclosure, the coincidence events determined in step S121 may include true events, random events, and scattered events. Random events and scattered events affect the accuracy of the time calibration value obtained later and need to be discarded. Those skilled in the art will understand that the LORs corresponding to true coincidence events all pass through the target object, i.e., have an intersection with the target object, while random events and scattered events do not pass through the target object, i.e., do not have an intersection with the target object. Therefore, in one example of the present disclosure, coincidence events corresponding to true events may be sorted based on whether the LOR corresponding to the coincidence event passes through the target object.

[0100] In an embodiment of the present disclosure, the selection of all response lines LORi passing through the target object and the coincidence events K on each LORi may be realized by determining whether the line on which the LOR exists has an intersection with the target object. Specifically, it may include the following steps:

[0101] Based on the prior information, an intersection determination module is used to determine whether the line on which the LOR exists has an intersection with the target object.

[0102] In one embodiment of the present disclosure, the prior information may include the number of scintillators IP between the spaced apart scintillators of the detection modules at two ends of the LOR, where the number of scintillators IP between the spaced apart scintillators is determined based on whether the target object has an intersection with the line on which each LOR is located.

[0103] In one example of the present disclosure, the acquisition of prior information can be based on different target objects in advance. For target objects with regular or irregular shapes, it can be done by counting in advance the number of scintillators IP between the scintillators IP at two ends of each corresponding LOR when each LOR has an intersection with the target object, and using this as prior information to create a prior information lookup table to facilitate investigation.

[0104] In one example, regarding the acquisition of prior information for a target object having a regular shape, taking a cylindrical simulated radiation source with a diameter of less than 20 mm as an example of the target object, the distance f between the line on which the LORGH exists and the center point of the cylindrical radiation source is determined by the prior information. If the distance f is equal to or less than the radius d of the cylindrical radiation source, the line on which the LORGH exists has at least one intersection with the cylindrical radiation source and passes through the cylindrical radiation source. When the distance f = d, the line on which the LORGH exists circumscribes the cross section of the cylindrical radiation source. If the scintillator IP number of scintillator G is 6 and the scintillator IP number of scintillator H is 20, and f = d, it is statistically determined that the number of scintillators spaced apart between scintillators G and H is 14. Then, when this cylindrical simulated radiation source is used as the target object, if the number of scintillators IP between the scintillators at the two ends of a certain LOR is 14 or more, the LOR will pass through the target object. On the other hand, the prior information obtained based on this cylindrical simulated radiation source is that if the number of scintillators IP between the scintillators corresponding to the two ends of the LOR is 14 or more, the LOR will pass through the target object.

[0105] In one example, let's take a shell source with a regular shape as an example of the target object. Let's assume that the diameter of the shell source used is 500 mm. Let's assume that the PET detector used has 48 scintillators. If the number of scintillator IPs spaced apart between two scintillator IPs corresponding to the two ends of the LOR is 12, the LOR between the two scintillators passes through the center of the shell source, and the distance from the center of the shell source is 0. If there are nine scintillator IPs between the two scintillators, the distance between the line connecting the midpoints of the surfaces of the two crystals and the center of the shell source is 180 mm, and the LOR between the two scintillators passes through the shell source. If there are six scintillator IPs between the two scintillators, the distance between the line connecting the midpoints of the surfaces of the two scintillators and the center of the shell source is 250 mm, and the LOR between the two scintillators circumscribes the shell source. If the number of scintillator IPs between two scintillators corresponding to the two ends of a certain LOR is less than 6, the LOR does not pass through the shell source. On the other hand, the prior information obtained based on this shell source is that if the number of scintillator IPs between the scintillators corresponding to the two ends of the LOR is 6 or more, the LOR passes through the target object, i.e., the shell source.

[0106] In one embodiment of the present disclosure, when obtaining prior information on an irregularly shaped object, it is necessary to count bit by bit to determine whether the object and the line on which each LOR exists have an intersection. Continuing with the example of a PET detector with 48 scintillators, if the number of scintillator IPs between the scintillator IP numbers of scintillators M and N corresponding to the two ends of LORMN is 5 or more, LORMN has an intersection with the object; in contrast, if the number of spaced scintillators IPs is less than 5, LORMN does not have an intersection with the object; if the number of scintillator IPs between the scintillator IP numbers of scintillators S and R corresponding to the two ends of LORSR is 8 or more, LORSR has an intersection with the object; in contrast, if the number of spaced scintillators IPs is less than 8, LORSR does not have an intersection with the object; Similarly, for each LOR formed between any two of the 48 scintillators and having an intersection with the target object, the critical value of the number of scintillator IPs spaced apart between the scintillator IP numbers at both ends of the LOR is counted and recorded, thereby forming a look-up table of prior information to subsequently determine whether the LOR corresponding to a coincidence event intersects with the target object based on the LOR and the prior information, thereby facilitating the determination of whether the LOR of that coincidence event passes through the target object.

[0107] In an embodiment of the present disclosure, after obtaining the prior information, an intersection determination module is used to determine whether the line on which the LOR exists has an intersection with the target object based on the prior information. In one example, taking the shell source in the above example as an example of the target object, by using the obtained prior information (if the number of scintillator IPs between the scintillators corresponding to the two ends of the LOR is six or more, the LOR passes through the target object, i.e., the shell source), if there are five scintillator IPs between the scintillator IPs of two scintillators corresponding to the two ends of a certain LOR, the line on which the LOR exists does not pass through the target object, and all coincidence events on the LOR are scattering events or random events and are discarded. In contrast, if there are seven scintillator IPs between the scintillator IPs of two scintillators corresponding to the two ends of a certain LOR, the line on which the LOR exists passes through the target object, and all coincidence events on the LOR are true events.

[0108] In an embodiment of the present disclosure, a coincidence event Ki (i≧1) on an LORi (i≧1) passing through a target object, acquired based on sampling data, is a genuine coincidence event. The coincidence event Ki includes coincidence event information, specifically, but not limited to, the number of coincidence events on each LOR, the time difference Δt between each coincidence event, identification position information of scintillators corresponding to the two ends of the LOR, the corresponding LOR, i.e., a line connecting the centers of the surfaces of the two scintillators, and the number of scintillators IP between the two scintillators.

[0109] In some embodiments, after acquiring LORi (i≧1) passing through the target object and coincidence events K (i≧1) on each LORi based on the sampling data, the method further includes the steps of:

[0110] The selected LORs and their corresponding coincidence event information are recorded in the recording module.

[0111] In one example, the selected LORs and their corresponding coincidence event information recorded in the recording module include, but are not limited to, the number of coincidence events on each LOR, the time difference Δt between each coincidence event, identification position information of the scintillators corresponding to the two ends of the LOR, the corresponding LOR, i.e., the line connecting the centers of the surfaces of the two scintillators, and the number of scintillators IP between the two scintillators. Recording in the recording module facilitates confirmation and subsequent reconstruction of the radioactivity image.

[0112] Step S130: Based on all coincidence counting events of all response lines LORi passing through the target object, a radioactivity image is acquired, pixel points Pi where each response line LORi passing through the target object intersects with the radioactivity image are determined, and a pixel value-time difference statistical distribution Ti corresponding to each LORi is determined based on the pixel points Pi.

[0113] In one embodiment, step S130 may specifically include:

[0114] Step S131: A radioactivity image is acquired based on all coincidence count events of all response lines LORi passing through the target object.

[0115] In some embodiments, after determining the coincidence events that pass through the target object in step S120, it may acquire a radioactivity image based on all the coincidence events of all LORi that pass through the target object. In one example, step S131 includes reconstructing a radioactivity image using filtered back projection or an iterative method based on all the coincidence events of all response lines LORi that pass through the target object. The specific implementation of filtered back projection (FBP) or the iterative method may refer to the prior art and will not be described in detail here.

[0116] The pixel value of each pixel point in the radioactivity image acquired in the embodiment of the present disclosure is a radioactivity value, which has a linear proportional relationship with the number of coincidence events (assuming the linear coefficient is k, the value of k is determined by the specific type of PET detector used. The proportional relationship between the pixel value of the radioactivity image and the number of coincidence events is determined by the type of PET detector), and can be used to characterize the number of coincidence events.

[0117] S132: Determine pixel points Pi where each line of response LORi passing through the target object intersects with the radioactivity image.

[0118] In an embodiment of the present disclosure, after acquiring the radiation image, it may determine pixel points Pi where each response line LORi passing through the target object intersects with the radiation image. In one example, determining pixel points Pi where each response line LORi passing through the target object intersects with the radiation image specifically includes determining pixel points Pi where the selected LORi intersects with the radiation image acquired in step S131 based on the ray tracing method of the prior art. That is, based on the ray tracing method, it may determine each intersection point, i.e., intersected pixel points, between the LORi selected in step S120 and the radiation image acquired in step S131. Specific operations may refer to the prior art and will not be described in detail here.

[0119] S133: Based on the pixel points Pi, a pixel value-time difference statistical distribution Ti corresponding to each LORi is determined.

[0120] In an embodiment of the present disclosure, after determining the pixel points Pi, it may obtain a pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel points Pi. Optionally, determining the pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel points Pi may specifically include the following steps:

[0121] Step S1331: Calculate the time difference from each pixel point Pi to the end point of the corresponding response line LORi, and record the pixel value of each pixel point Pi.

[0122] Step S1332: A plurality of equally spaced time difference intervals are determined, and pixel values ​​of pixel points Pi whose time differences fall within each time difference interval are accumulated based on the time difference of each pixel point Pi.

[0123] Step S1333: The pixel value-time difference statistical distribution Ti corresponding to each response line LORi is determined by setting the time difference interval as the horizontal axis step size and the cumulative pixel value of the pixel points within each step size as the vertical axis.

[0124] S140: Based on the coincidence events Ki on each response line LORi, a coincidence event-time difference statistical distribution Mi corresponding to each response line LORi is determined.

[0125] In an embodiment of the present disclosure, after determining the response lines LORi (i≧1) passing through the target object and the coincidence events K (i≧1) on each LORi based on the sampling data in step S120, it may determine the coincidence event-time difference statistical distribution M corresponding to each LORi based on the coincidence events K on each LORi. In one example, this specifically includes:

[0126] The horizontal axis is determined by setting the horizontal step size of the pixel value-time difference statistical distribution Ti as the step size, and the coincidence count event-time difference statistical distribution Mi corresponding to each response line LORi is determined by setting the cumulative value of coincidence count events whose time difference falls within each step size as the vertical axis.

[0127] In an embodiment of the present disclosure, the coincidence counting event-time difference statistical distribution Mi corresponding to each LORi and the corresponding pixel value-time difference statistical distribution Ti have the same horizontal axis step size and the same range set for the horizontal axis, i.e., the horizontal axis settings of Ti and Mi are completely the same, thereby facilitating the subsequent calculation of the maximum value Yi of the dot product of each Ti and the corresponding Mi.

[0128] Step S150: Based on the pixel value-time difference statistical distribution Ti and the coincidence event-time difference statistical distribution Mi corresponding to each LORi, the maximum value Yi of the dot product of each Ti and Mi is calculated, and the time offset difference value δΔi corresponding to the maximum value for each LORi is determined.

[0129] In the embodiment of the present disclosure, calculating the maximum value Yi of the dot product of each Ti and Mi based on Ti and Mi, and determining the time offset difference value δΔi corresponding to the maximum value of each LORi is realized by a calculation module.

[0130] In some embodiments, calculating the maximum value Yi of the dot product of each Ti and Mi and determining the time offset difference value δΔi corresponding to the maximum value for each LORi includes:

[0131] Using Ti as a reference, shift Mi, calculate the dot product of Ti and Mi, and record the shift amount of Mi when the dot product of Ti and Mi reaches the maximum value Yi, where the shift amount is δ△i.

[0132] In the embodiment of the present disclosure, the dot product of Ti and Mi is specifically a value obtained by multiplying the values ​​of the vertical coordinates of Ti and Mi corresponding to the same horizontal coordinate, and then adding them together. As can be seen from steps S130 to S140, the horizontal coordinate settings of Ti and Mi are exactly the same, the value of the vertical coordinate corresponding to the horizontal coordinate of Ti is the cumulative value of the pixel values ​​corresponding to the time difference interval range indicated by that horizontal coordinate, and the value of the vertical coordinate corresponding to the horizontal coordinate of Mi is the cumulative value of the coincidence counting events corresponding to the time difference interval range indicated by that horizontal coordinate. In other words, the dot product of Ti and Mi is specifically a value obtained by multiplying the cumulative pixel values ​​and cumulative coincidence counting events corresponding to each horizontal coordinate, and then adding them together.

[0133] Those skilled in the art will understand that, assuming that the scintillators corresponding to the two ends of LORi are c i and di, the time offset of scintillators c i and di is represented by δc i and δd i , respectively, and the difference between δc i and δd i is represented by δΔi , i.e., δc i - δd i = δΔi , the time difference E i of coincidence events on LORi is

[0134] tci + δci - (tdi + δdi) = Ei is expressed by

[0135] where tci and tdi are the time data in the sampling data corresponding to scintillators ci and di received by the host computer. Rearranging the above equation, we obtain:

[0136] tci - tdi + (δci - δdi) = Ei

[0137] When δci = δdi, we obtain:

[0138] tci - tdi = Ei

[0139] From the above equation, we can see that when δci = δdi, i.e., δci - δdi = δ△i = 0, the time difference between coincidence events on LORi is unrelated to δci and δdi, and is related only to the location where the annihilation events occur. The time difference between two single events corresponding to two gamma photons occurring at different annihilation locations on LORi is different, but the time difference between two single events corresponding to two gamma photons occurring at the same annihilation location at different times is identical. When LORi supports multiple coincidence events, the number of coincidence events corresponding to the same time difference is determined. Therefore, the fluctuation trends of the vertical coordinates corresponding to the same horizontal coordinates of Mi and Ti will be consistent, the peaks of Mi and Ti will correspond to each other, and the value Yi obtained by multiplying and adding them will be maximized.

[0140] That is, when the dot product value of Mi and Ti corresponding to a certain LORi is maximum, the peaks of Mi and Ti correspond to each other, and the time offsets δci and δdi of the two scintillators ci and di corresponding to the two ends of LORi satisfy δci - δdi = δ△i = 0.

[0141] In contrast, when the dot product value of Mi and Ti corresponding to a certain LORi does not reach the maximum value Yi, the peaks of Mi and Ti do not correspond to each other, and δci - δdi = δ△i, where δ△i is not zero.

[0142] When the dot product value of Mi and Ti corresponding to a certain LORi does not reach the maximum value Yi (i.e., the peaks of Mi and Ti do not correspond to each other), it is caused by δci - δdi = δ△i, where δ△i is not 0. When the dot product value of Mi and Ti corresponding to a certain LORi reaches the maximum value Yi (at this time, the peaks of Mi and Ti correspond to each other), it is caused by the time offsets δci and δdi of the two scintillators ci and di corresponding to the two ends of LORi satisfying δci - δdi = δ△i = 0. Therefore, it is possible to move Mi and Ti relative to each other so that the dot product value of Mi and Ti reaches the maximum value from a non-maximum value. Meanwhile, the amount of relative movement of Mi and Ti is the difference value δ△i between δci and δdi. Meanwhile, the time offsets δci and δdi of the two scintillators ci and di corresponding to the two ends of LORi satisfy δci - δdi = δ△i.

[0143] In the embodiment of the present disclosure, assuming that Mi and Ti correspond to the LORs i of two scintillators ci and di corresponding to two ends, Mi may be moved using Ti as a comparison reference. Specifically, the relative movement may be realized by the following operations.

[0144] First, the range of δΔ is determined through prior information. For example, by fitting through long-term sampling, we obtain δci - δdi = δΔi for LORi, and obtain the range of δΔi. For example, the range of δΔi is [-5, 5] ns.

[0145] Second, t represents the horizontal coordinate of Ti (the horizontal coordinate step size is the time difference interval range), cT represents the value of the vertical coordinate of Ti (the cumulative pixel value), thus obtaining Ti(t,cT). t represents the horizontal coordinate of Mi (the horizontal coordinate step size is the time difference interval range), cM represents the value of the vertical coordinate of Mi (the cumulative coincidence counting events), thus obtaining Mi(t,cM). The ranges of the horizontal coordinate t of Mi(t,cM) and Ti(t,cT) are set to be the same, and both are set to be larger than the range of δΔ obtained based on the prior information. By setting the shift step size of Mi(t,cM), Mi(t,cM) is shifted by the step size δM each time. After n shifts, Mi(t+nδM,cM) is obtained. The vertical coordinates of the shifted Mi(t+nδM,cM) and Ti(t,cT) corresponding to the same horizontal coordinate are multiplied and then added to obtain the dot product.<Mi(t+nδM,cM),Ti(t,cT)> reaches its maximum value Yi. At this time, the peaks of M(t+nδM,cM) and T(t,cT) correspond to their maximum values, and Mi and Ti change from peaks that do not correspond to each other to peaks that correspond to each other. The shift nδM is the difference value δ△i between the time offsets δci and δdi of the scintillators ci and di at the two ends of LORi corresponding to Mi and Ti, i.e., δci - δdi = δ△i = n * δM.

[0146] Step S160: Determine a time calibration value based on δΔi.

[0147] In an embodiment of the present disclosure, after determining δΔi, it may determine a time calibration value based on δΔi. In one example, determining a time calibration value based on δΔi specifically includes:

[0148] Step S161: determining the relationship δci - δdi = δ△i between the time offsets δci and δdi of the scintillators ci and di of the detection modules at the two ends of each LORi based on δ△i; and

[0149] Step S162: Determine the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi by solving the simultaneous equations using a fitting method, where the time offsets δci and δdi are the time calibration values ​​of the scintillators ci and di.

[0150] In an embodiment of the present disclosure, after determining the time offsets δci and δdi of the scintillators ci and ddi of the detection modules at the two ends of each LORi, i.e., the time calibration values, the method may include the following steps:

[0151] Step S170: Based on the determined time calibration value, perform time calibration on the sampling data.

[0152] In a particular example of the present disclosure, performing calibration on the time data corresponding to the scintillators ci and di of the detection module in the sampling data includes:

[0153] Time calibration values ​​δci and δdi are subtracted from the time data tci and tdi corresponding to the scintillators ci and di of the detection module in the sampling data, respectively.

[0154] In an embodiment of the present disclosure, a pixel value-time difference statistical distribution Ti and a coincidence counting event-time difference statistical distribution Mi corresponding to each LORi are obtained based on selected true coincidence counting events that pass through the target object, the maximum value Yi of the dot product of each Ti and Mi is calculated, a time offset difference value δΔi corresponding to the maximum value for each LORi is obtained, and a time calibration value is then obtained based on δΔi. This method is applicable to any target object, has wide applications, does not require Gaussian fitting, thereby saving time, improving the efficiency of time calibration, and does not require the use of highly radioactive drugs, thereby improving operational safety. In addition, in an embodiment of the present disclosure, a pixel value-time difference statistical distribution Ti and a coincidence counting event-time difference statistical distribution Mi corresponding to each LORi are obtained based on selected true coincidence counting events that pass through the target object, and random events and scattered events are discarded, thereby improving the accuracy of the obtained time offset difference value δΔi corresponding to each LORi, thereby improving the accuracy of time calibration.

[0155] In some embodiments, as an alternative or addition to the embodiment of Fig. 2, it may select a response line LORj (j≧1) whose number of coincidence counting events satisfies a preset condition based on all response lines LORi passing through the target object. Specifically, the time calibration method shown in the embodiment of Fig. 3 may include the following steps S220, S230, S240, S250, S260, S270, and S280.

[0156] Starting from the implementation of this method, step S210 may be performed first, that is, sampling the pulse signal acquired based on the target object to obtain sampling data.

[0157] In the embodiment of the present disclosure, the target object, pulse signal, sampling data, and their acquisition may refer to the features of step S110 shown in FIG. 2, and will not be described in detail here.

[0158] Step S220: Based on the sampling data of the target object, response lines LORi (i≧1) passing through the target object and coincidence events Ki (i≧1) on each LORi are determined.

[0159] In an embodiment of the present disclosure, the determination of response lines LORi (i≧1) passing through the target object and coincidence events Ki (i≧1) on each LORi may refer to the features of step S120 of the time calibration method shown in FIG. 2 and will not be described in detail here.

[0160] Step S230: A radioactivity image is acquired based on all coincidence count events of all response lines LORi passing through the target object.

[0161] In an embodiment of the present disclosure, the acquisition of the radiological image may refer to the features of step S131 of the time calibration method shown in FIG. 2, and will not be described in detail here.

[0162] Step S240: Based on all response lines LORi passing through the target object, response lines LORj (j≧1) whose number of coincidence count events satisfies a preset condition are selected.

[0163] Those skilled in the art can understand that if the number of coincidence events corresponding to a certain LOR is too small, the coincidence events on this LOR may generally be considered as scattering events or random events. For example, if there is only one pair of coincidence events on an LOR, the coincidence events on this LOR may be considered as scattering events or random events. To further improve the accuracy of the calibration, it is necessary to further select true events. A certain standard may be set to select true events from coincidence events and discard scattering events or random events.

[0164] In an embodiment of the present disclosure, after acquiring all response lines LORi passing through the target object, it may select a response line LORj (j≧1) whose number of coincidence counting events meets a preset condition. In a specific example, step S240 specifically includes:

[0165] Step S241: A reference value for comparing the number of coincidence count events is set.

[0166] In an embodiment of the present disclosure, the reference value for comparing the number of coincidence counting events may be set based on prior information or according to specific needs. For example, the reference value for the number of coincidence counting events used for comparison may be set to 20. If the number of coincidence counting events corresponding to each LOR is relatively large, the reference value may be set to a relatively large number; conversely, the reference value may be set to a smaller number.

[0167] Step S242: Determine whether the number of coincidence events is greater than a reference value.

[0168] In the embodiment of the present disclosure, the number of coincidence events corresponding to each LOR is compared with a reference value. If the number of coincidence events corresponding to a certain LOR is greater than the reference value, it meets the requirement, and the LOR is retained and recorded. Otherwise, the LOR is discarded.

[0169] Step S243: The LOR in which the number of coincidence events is greater than the reference value is stored using a storage module.

[0170] In an embodiment of the present disclosure, the LORs that meet the requirements determined in step S242 are stored in a storage module.

[0171] Step S250: Determine pixel points Pj where each selected response line LORj intersects with the radiation image, and determine pixel value-time difference statistical distributions Tj corresponding to each response line LORj based on the pixel points Pj.

[0172] In one example, step S250 specifically includes:

[0173] Step S251: Determine the pixel points Pj where each selected response line LORj intersects with the radioactivity image.

[0174] In an embodiment of the present disclosure, after obtaining the radiation image, it may determine pixel points Pj where each selected response line LORj passing through the target object intersects with the radiation image. In one example, step S251 specifically includes determining pixel points Pj where each selected response line LORj intersects with the radiation image based on a ray tracing method. The specific operation of the ray tracing method can be referred to the prior art and will not be described in detail here.

[0175] Step S252: Based on the pixel points Pj, the pixel value-time difference statistical distributions Tj corresponding to each LORj are determined.

[0176] In an embodiment of the present disclosure, step S252 specifically includes:

[0177] Calculate the time difference from each pixel point Pj to the end point of the corresponding LORj, and record the pixel value of each pixel point Pj;

[0178] Determining a plurality of equally spaced time difference intervals, and counting the cumulative pixel values ​​of the pixel points Pj whose time differences fall within each time difference interval based on the time difference of each pixel point Pj; and

[0179] The pixel value-time difference statistical distribution Tj corresponding to each LORj is determined by setting the time difference interval as the horizontal axis step size and the cumulative pixel value of the pixel points within each step size as the vertical axis.

[0180] Step S260: Determine the coincidence event-time difference statistical distribution Mj corresponding to each selected LORj.

[0181] In one example, step S260 specifically includes the following: determining the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and determining the coincidence count event-time difference statistical distribution Mj corresponding to each response line LORj by setting the cumulative value of the coincidence count events whose time differences fall within each step size as the vertical axis.

[0182] In an embodiment of the present disclosure, the coincidence event-time difference statistical distribution Mj corresponding to each LORj has the same horizontal axis step size as its corresponding pixel value-time difference statistical distribution Tj, and their horizontal coordinate range settings are also the same, i.e., Tj and Mj have exactly the same horizontal coordinate settings, which facilitates the later calculation of the maximum value Yj of the dot product between each Tj and its corresponding Mj.

[0183] Step S270: Based on the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each selected LORj, calculate the maximum value Yj of the dot product of each Tj and Mj, and determine the time offset difference δΔj corresponding to the maximum value for each LORj.

[0184] In some embodiments, calculating the maximum value Yj of the dot product of each Tj and Mj and determining the time offset difference value δΔj corresponding to the maximum value for each LORj includes:

[0185] Using Tj as a reference, shift Mj, calculate the dot product of Tj and Mj, and record the shift amount of Mj when the maximum value Yj of the dot product of Tj and Mj is reached, and the shift amount is δΔj.

[0186] In an embodiment of the present disclosure, a calculation module calculates the maximum value Yj of the dot product of each Tj and Mj based on the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each selected LORj, and determines the time offset difference value δΔj corresponding to the maximum value of each LORj.

[0187] In the embodiment of the present disclosure, the calculation of the maximum value Yj of the dot product of each Tj and Mj and the determination of the time offset difference value δΔj corresponding to the maximum value of each LORj may refer to the features in step S150 of the time calibration method shown in FIG. 2, and will not be described in detail here.

[0188] Step S280: Determine a time calibration value based on the difference value δΔj.

[0189] In one example, determining the time calibration value based on δΔj specifically includes:

[0190] Step S281: Based on δΔj, determine the relationship between the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each response line LORj, where δcj - δdj = δΔj.

[0191] Step S282: Determine the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each response line LORj by solving the simultaneous equations using a fitting method, where δcj and δdj are the time calibration values ​​of the scintillators cj and dj.

[0192] In an embodiment of the present disclosure, after determining the time offsets δcj and δdj of the scintillators cj and dj of the detection modules at the two ends of each LORj, i.e., the time calibration values, the following steps may be included:

[0193] Based on the time offsets δcj and δdj of the scintillators cj and dj of the detection module, calibration is performed on the time data corresponding to the scintillators cj and dj of the detection module in the sampling data, for example, by subtracting the time calibration values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillators cj and dj of the detection module in the sampling data, respectively.

[0194] The difference between the embodiment shown in Figure 3 and the embodiment shown in Figure 2 is that by selecting, based on all LORi passing through the target object, response lines LORj (j≧1) whose number of coincidence counting events meets a preset condition, random events and scattered events among the coincidence counting events are further discarded, and as many true events as possible are selected for obtaining time calibration values ​​that are performed later, thereby improving the accuracy of the obtained time calibration values, i.e., improving the effect of time calibration.

[0195] In some embodiments, the meaning or description of the same or similar words or features in the time calibration method of this embodiment may refer to the time calibration method of the embodiment shown in FIG. 2, and the steps and features of the embodiment shown in FIG. 2 may be combined in the time calibration method of this embodiment in a consistent manner.

[0196] In an embodiment of the present disclosure, a pixel value-time difference statistical distribution Tj and a coincidence event-time difference statistical distribution Mj corresponding to each LORj are obtained based on the selected true coincidence counting events that pass through the target object, the maximum value Yj of the dot product of each Tj and Mj is calculated, and the time offset difference value δΔj corresponding to the maximum value of each LORj is obtained. Then, a time calibration value is obtained based on δΔj. This method is applicable to any target object, has a wide range of applications, does not require Gaussian fitting, thereby saving time and improving the efficiency of time calibration, and does not require the use of highly radioactive drugs, thereby improving operational safety. In addition, in the embodiment of the present disclosure, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each LORj are obtained based on true coincidence events corresponding to LORs that pass through the target object and whose number of coincidence events satisfies a preset condition, so that random events and scattered events are further discarded, and accordingly, the accuracy of the obtained difference value δΔj of the time offset corresponding to each LORj is further improved, thereby further improving the accuracy of the time calibration.

[0197] FIG. 4 is an exemplary modular diagram of a time calibration device according to some embodiments of the present disclosure.

[0198] FIG. 4 shows a time calibration device, which may include:

[0199] a coincidence event sorting module 430, a radioactivity image reconstruction module 440, a pixel value-time difference statistical distribution acquisition module 450, a coincidence event-time difference statistical distribution acquisition module 460, a calculation module 470, and a time calibration value acquisition module 480.

[0200] In some embodiments, the coincidence event selection module 430 is configured to determine response lines LORi (i≧1) passing through the target object and coincidence events K i (i≧1) on each LORi based on sampling data of the target object.

[0201] In one example, the coincidence event sorting module 430 includes an intersection determination module, which determines whether the line on which the LOR exists has an intersection with the target object, and determines whether the LOR passes through the target object based on the number of intersections. Specifically, the intersection determination module may determine whether the line on which the LOR exists has an intersection with the target object based on prior information. In a specific example, the prior information includes the number of scintillators IP between the spaced scintillators of the detection modules at two ends of the LOR, and the number of spaced scintillators IP is determined based on whether the inner diameter of the target object in various directions and the line on which the LOR exists have an intersection.

[0202] In some embodiments, the radioactivity image reconstruction module 440 is configured to acquire a radioactivity image based on all coincidence events of all response lines LORi passing through the object. In one example, the radioactivity image reconstruction module 440 acquires a radioactivity image based on all coincidence events of all response lines LORi passing through the object, which includes reconstructing the radioactivity image using filtered back projection or an iterative method.

[0203] In some embodiments, the pixel value-time difference statistical distribution acquisition module 450 is configured to determine pixel points Pi where each response line LORi passing through the target object intersects with the radioactivity image, and to determine pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel points Pi.

[0204] 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 determine pixel points Pi where the selected LORi intersect with the radiological image based on a ray tracing method. The time difference statistical distribution acquisition module is used to determine pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel points Pi.

[0205] 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 each pixel point Pi to the end point of the corresponding LORi and record the pixel value of each pixel point Pi. The pixel value accumulation module is used to determine a plurality of equally spaced time difference intervals and count the accumulated pixel values ​​of pixel points Pi whose time differences fall within each time difference interval based on the time differences of each pixel point Pi. The pixel value-time difference statistical distribution Ti acquisition module is used to determine the pixel value-time difference statistical distribution Ti corresponding to each LORi by taking the time difference interval as the horizontal axis step size and the accumulated pixel values ​​of pixel points falling within each step size as the vertical axis.

[0206] In some embodiments, the coincidence event-time difference statistical distribution acquisition module 460 is configured to determine a coincidence event-time difference statistical distribution Mi corresponding to each LORi.

[0207] In a specific example, to determine the coincidence counting event-time difference statistical distribution Mi corresponding to each LORi, the coincidence counting event-time difference statistical distribution acquisition module 460 is configured to determine the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Ti as the step size, and to determine the coincidence counting event-time difference statistical distribution Mi corresponding to each LORi by setting the vertical axis as the cumulative value of the coincidence counting events whose time differences fall within each step size.

[0208] In some embodiments, the calculation module 470 is configured to calculate the maximum value Yi of the dot product of each Ti and Mi, and determine the difference δΔi in time offsets corresponding to the maximum value of each LORi.

[0209] In some embodiments, the time calibration value acquisition module 480 is configured to determine the time calibration value based on δΔi. In one example, the time calibration value is the time offsets δci and δdi of the scintillation crystals c and di of the detection module.

[0210] In a particular example, the time calibration value acquisition module 480 includes a fitting module that is configured to determine, based on δi, the relationship δci - δdi = δi between the time offsets δci and δdi of the scintillation crystals ci and di of the detection modules at the two ends of each LORi, and to determine the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi by solving the simultaneous equations using a fitting method.

[0211] In some embodiments, the calculation module and the time calibration value acquisition module may be implemented by the same device.

[0212] In some embodiments, the time calibration device may further include a coincidence module for determining all coincidence events and LORs corresponding to each coincidence event based on the sampling data. In one example, the sampling data may include scintillator IP information and pulse signal time information of the detection module. The coincidence module includes a pulse signal energy information acquisition module for determining pulse signal energy information based on the sampling data, determining coincidence events based on the pulse signal time information and energy information, and determining response line LORs corresponding to the coincidence events based on the scintillator IP information.

[0213] In some embodiments, the time calibration device may also include a recording module for recording the time difference between the coincidence events and the scintillator number information of the scintillators of the detection modules at the two ends of the corresponding LOR.

[0214] In some embodiments, the time calibration device also includes a calibration module, and the sampling data includes scintillator number information of the detection module and time information of the pulse signal. The calibration module is used to perform time calibration on the time information of the pulse signal in the sampling data based on a time calibration value.

[0215] In one example, the calibration module performs time calibration on the time information of the pulse signal in the sampling data based on the time calibration value, i.e., performs calibration on the time data corresponding to the scintillators ci and di of the detection module in the sampling data, which includes subtracting the time calibration values ​​δci and δdi from the time data tci and tdi corresponding to the scintillation crystals ci and di of the detection module, respectively.

[0216] In the embodiment of the present disclosure, a pixel value-time difference statistical distribution Ti and a coincidence event-time difference statistical distribution Mi corresponding to each LORi are obtained based on selected true coincidence events that pass through the target object, the maximum value Yi of the dot product of each Ti and Mi is calculated, a time offset difference value δΔi corresponding to the maximum value for each LORi is obtained, and then a time calibration value is obtained based on δΔi, which is applicable to any target object, has a wide range of applications, and does not require Gaussian fitting, thereby saving time and improving the efficiency of time calibration. In addition, in the embodiment of the present disclosure, a pixel value-time difference statistical distribution Ti and a coincidence event-time difference statistical distribution Mi corresponding to each LORi are obtained based on selected true coincidence events that pass through the target object, and random events and scattered events are discarded, thereby improving the accuracy of the obtained time offset difference value δΔi corresponding to each LORi, and thereby improving the accuracy of time calibration.

[0217] In some embodiments, as an alternative or in addition to the embodiment of Figure 4, two coincidence event sorting modules may be provided, where a first coincidence event sorting module corresponds to the coincidence event sorting module of the embodiment shown in Figure 4, and a second coincidence event sorting module is configured to sort, 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. Specifically, as shown in the embodiment of the time calibration device of Figure 5, the time calibration device may include:

[0218] a first coincidence event sorting module 530 configured to determine lines of response LORi (i≧1) passing through the object and coincidence events K i (i≧1) on each LORi based on the sampling data of the object;

[0219] a radioactivity image reconstruction module 540 configured to acquire a radioactivity image based on all coincidence events of all response lines LORi passing through the target object:

[0220] a second coincidence event sorting module 550 configured to sort out a response line LORj whose number of coincidence events meets a preset reference value based on all response lines LORi passing through the target object;

[0221] a pixel value-time difference statistical distribution acquisition module 560 configured to determine pixel points Pj where each selected response line LORj intersects with the radioactivity image, and determine a pixel value-time difference statistical distribution Tj corresponding to each LORj based on the pixel points Pj;

[0222] a coincidence event-time difference statistical distribution acquisition module 570 configured to determine a coincidence event-time difference statistical distribution Mj corresponding to each sorted LORj;

[0223] a calculation module 580 configured to calculate the maximum Yj of the dot product of each Tj and Mj and determine the difference δΔj in time offsets corresponding to the maximum Yj of each LORj; and

[0224] A time calibration value acquisition module 590 configured to determine a time calibration value based on δΔj.

[0225] The difference between this embodiment and the embodiment shown in FIG. 4 is that there are two coincidence event sorting modules in this embodiment. The first coincidence event sorting module 530 corresponds to the coincidence event sorting module in the embodiment shown in FIG. 4, and both are configured to determine response lines LORi (i≧1) passing through the target object and coincidence events K (i≧1) on each LORi, specifically referring to the embodiment shown in FIG. 4. In addition, in this embodiment, it may also include a second coincidence event sorting module 550, which is configured to sort response lines LORj whose number of coincidence events meets a preset reference value based on all response lines LORi passing through the target object. In one example, the second coincidence event sorting module includes a reference value setting module for setting a reference value for comparing the number of coincidence events, a determination module for determining whether the number of coincidence events is greater than the reference value, and a storage module for storing LORs whose number of coincidence events is greater than the reference value.

[0226] In this embodiment, by providing a second coincidence counting event selection module 550, response lines LORj (j≧1) whose number of coincidence counting events meets a preset condition are selected based on all response lines LORi passing through the target object, and accidental events and scattered events among the coincidence counting events are further discarded, and as many true events as possible are selected for later obtaining time calibration values, thereby improving the accuracy of the obtained time calibration values, i.e., improving the effect of time calibration.

[0227] In the time calibration device of the embodiments of the present disclosure, components or features of the embodiment of the time calibration method shown in Figure 4 may be included in a consistent manner, or the embodiment shown in this figure may be combined with the embodiment shown in Figure 4 to obtain a new embodiment, and vice versa.

[0228] In an embodiment of the present disclosure, based on the selected true coincidence counting events passing through the target object, a pixel value-time difference statistical distribution Tj and a coincidence counting event-time difference statistical distribution Mj corresponding to each LORj are obtained, the maximum value Yj of the dot product between each Tj and Mj is calculated, and the time offset difference value δΔj corresponding to the maximum value of each LORj is obtained, and then a time calibration value is determined based on δΔj, which is applicable to any target object, has a wide range of applications, does not require Gaussian fitting, thereby saving time and improving the efficiency of time calibration, and does not require the use of highly radioactive drugs, thereby improving operational safety. In addition, in the embodiment of the present disclosure, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each LORj are obtained based on true coincidence events corresponding to LORs that pass through the target object and whose number of coincidence events satisfies a preset condition, so that random events and scattered events are further discarded, thereby further improving the accuracy of the obtained difference value δΔj of the time offset corresponding to each LORj, and thereby further improving the accuracy of the time calibration.

[0229] Some embodiments of the present disclosure also provide a digitizing device including the time calibration device, the detection module, and the sampling module described in the above embodiments. The digitizing device may be used to calibrate time data of a pulse signal obtained based on a target object to improve calibration efficiency, calibration effectiveness, and calibration safety. The digitizing device detects the target object using the time calibration device, acquires sampling data, calibrates the sampling data based on the time calibration value to acquire calibrated time data, and forms a digital image based on the acquired coincidence events and the calibrated time data. In a specific example, the digitizing device is a positron emission tomography (PET) scanner.

[0230] In some embodiments, the detection module is configured to obtain a pulse signal based on the target object. The detection module 410 includes a detector including a scintillator and a photoelectric conversion element, where the scintillator is used to convert gamma rays into visible light, and the photoelectric conversion element is used to convert the visible light into a pulse signal.

[0231] In some embodiments, the sampling module is configured to sample the pulse signal to obtain sampling data, which may be referred to in the method embodiments and will not be described in detail herein.

[0232] In one example, the sampling module is a multi-voltage threshold sampling module including 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 a sampling threshold, the comparison module is used to compare the pulse signal with a threshold and output a transition signal, the time-to-digital conversion module is used to perform time sampling on the transition signal to obtain time information of the pulse signal, and the information storage module stores the scintillator number information of the detection module and the time information of the pulse signal.

[0233] In an embodiment of the present disclosure, the digitizing device may directly obtain the annihilation position based on the calibrated time data and coincidence events, thereby directly forming a digital image (such as a PET image) without the need for complex image reconstruction methods, simplifying image reconstruction.

[0234] Features of the methods described in the embodiments of the present disclosure may be combined in the apparatus described in the embodiments of the present disclosure, and vice versa.

[0235] In some embodiments of the present disclosure, a computing device is also provided, which includes a memory, a processor, and a computer program stored in the memory and executable by the processor, which, when executed by the processor, performs the steps of any of the methods described in the embodiments of the present disclosure.

[0236] Although not shown, in some embodiments, a computer-readable storage medium storing a computer program configured to perform the steps of any of the methods described in the embodiments of the present disclosure when executed is also provided. The computer program includes program modules / units that constitute an apparatus according to the embodiments of the present disclosure, and when executed, the computer program configured by the program modules / units can perform functions corresponding to each step described in the method of the above embodiments. The computer program may be executed on an electronic device described in the embodiments of the present disclosure.

[0237] This description explains the basic concepts, and it is obvious to those skilled in the art that the above detailed disclosure serves only as an example and does not mean any limitation to the present disclosure. Although not explicitly stated, those skilled in the art can make various changes, improvements, and modifications to the present disclosure. The changes, improvements, and modifications proposed in the present disclosure still fall within the spirit and scope of the exemplary embodiments of the present disclosure.

[0238] However, in this disclosure, specific terms are used to describe embodiments of the present disclosure. "One embodiment," "one embodiment," and / or "some embodiments" refer to specific features, structures, or characteristics related to at least one embodiment of the present disclosure. Therefore, it should be emphasized and pointed out that when "one embodiment," "one embodiment," or "alternative embodiments" are mentioned more than once in different places in this disclosure, they do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments of the present disclosure may be combined as appropriate.

[0239] Moreover, those skilled in the art will appreciate that various aspects of the present disclosure can be illustrated and described through several types or contexts of patentability, including any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof. Accordingly, various aspects of the present disclosure may be implemented entirely in hardware, entirely in software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. Such hardware or software may be referred to as "data blocks," "modules," "engines," "units," "components," or "systems." Furthermore, aspects of the present disclosure may take the form of a computer product located on one or more computer-readable medium(s) containing computer-readable program coding.

[0240] A computer storage medium may include a propagated data signal containing computer program coding, for example in baseband or as part of a carrier wave. This propagated signal may take various forms, including electromagnetic, optical, or a suitable combination thereof. A computer storage medium may be any computer-readable medium other than a computer-readable storage medium that can communicate, propagate, or transmit a program for use over a connection with an instruction execution system, apparatus, or device. The program coding located on the computer storage medium may be transmitted over any suitable medium, including wireless, cable, fiber optic cable, RF, or similar media, or any combination of the above media.

[0241] The computer program coding required for the various operations of the present disclosure may 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.; traditional procedural programming languages ​​such as C, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, etc.; dynamic programming languages ​​such as Python, Ruby, and Groovy, or other programming languages. The program coding can run entirely on the user's computer, as a standalone software package on the user's computer, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer through any form of network, such as a local area network (LAN) or wide area network (WAN), or connected to an external computer (e.g., through the Internet), or may be in a cloud computing environment or used as a service, such as software as a service (SaaS).

[0242] Furthermore, unless expressly specified in the claims, the use of processing elements and order, numerals, or other designations described in this disclosure are not intended to limit the order of the processes and methods of the present disclosure. While the above disclosure has described, through various examples, some presently contemplated embodiments of the present invention, it should be understood that such details are for illustrative purposes only, and that the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to encompass all modifications and equivalent combinations falling within the content and scope of the disclosed embodiments. For example, while the system components described above can be implemented through hardware devices, they can also be implemented through a purely software solution, such as by installing the described system on an existing server or mobile device.

[0243] Similarly, it should be noted that in the above description of the embodiments of the present disclosure, various features may be grouped together in a single embodiment, drawing, or description thereof to simplify presentation of the disclosure and thereby facilitate understanding of one or more embodiments of the present disclosure. However, this disclosed method does not mean that the disclosure requires more features than are recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single embodiment described above.

[0244] In some embodiments where numbers are used to describe properties of components and quantities, it should be understood that such numbers used to describe the embodiments are, in some instances, modified by terms such as "about," "approximately," or "substantially." Unless otherwise specified, "about," "approximately," or "substantially" means that the stated number allows for a variation of ±20%. Thus, in some embodiments, the numerical parameters used in the specification and claims are approximate values ​​that may vary depending on the properties required by particular embodiments. In some embodiments, the numerical parameters should be determined to the specified significant digits and ordinary rounding techniques should be used. While some embodiments of the present disclosure use numerical ranges and parameters to determine that these ranges are approximate, in certain embodiments, such numbers are set to the precise extent possible within the range feasible.

[0245] The entire contents of each patent, patent application, published patent application, and other material (such as articles, books, instructions, publications, documents, etc.) cited in this application are incorporated herein by reference, and the incorporation by reference excludes any filing history files that are inconsistent or conflict with the contents of this application, and any documents (now or later added to this application) that limit the scope of the broadest claims of this application. It should be noted that in the event of an inconsistency or conflict between the descriptions, definitions, and / or terminology set forth in the appendix to this application and the specification, the descriptions, definitions, and / or terminology provided in this application shall control.

[0246] Finally, it should be understood that the embodiments described herein are merely provided to illustrate the principles of embodiments of the present invention. Other modifications may fall within the scope of the present application. Thus, by way of example, and not of limitation, alternative configurations of the embodiments may be considered consistent with the teachings of the present application. Accordingly, the present application is not limited to only those embodiments expressly introduced and described herein.

Claims

1. determining lines of response (LORi) passing through the object and coincidence events K on each LORi based on sampling data of the object, where i represents a number and i≧1; acquiring a radioactivity image based on all coincidence events of all response lines LORi passing through the target object, determining pixel points Pi at which each of the LORi passing through the target object intersects with the radioactivity image, and determining pixel value-time difference statistical distributions Ti corresponding to each LORi based on the pixel points Pi; determining a coincidence event-time difference statistical distribution Mi corresponding to each LORi based on the coincidence events Ki on each LORi; calculating a maximum value Yi of an inner product of the pixel value-time difference statistical distribution Ti and the coincidence counting event-time difference statistical distribution Mi based on the pixel value-time difference statistical distribution Ti and the coincidence counting event-time difference statistical distribution Mi, and determining a time offset difference value δΔi corresponding to the maximum value Yi of each response line LORi; determining a time calibration value based on the offset difference value δΔi; A time calibration method comprising:

2. 2. The time calibration method of claim 1, wherein the response lines LORi passing through the target object include response lines LORi having at least one intersection with the target object, or response lines LORi that circumscribe the target object or intersect the target object.

3. determining lines of response (LORi) passing through the object and coincidence events K on each LORi based on the sampling data of the object, determining a line of response LOR corresponding to all coincidence counting events and each coincidence counting event based on the sampling data; selecting all response lines LORi passing through the object and coincidence events K on each LORi; 2. The time calibration method of claim 1, comprising:

4. selecting all response lines LORi passing through the object and coincidence events K on each LORi, 4. The time calibration method according to claim 3, further comprising the step of determining, based on prior information, whether a straight line on which the line of response LOR exists has an intersection with the target object.

5. 5. The time calibration method of claim 4, wherein the prior information includes the number of scintillators IP between spaced apart scintillators at two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects the straight line on which the line of response LOR exists.

6. acquiring the radioactivity image based on all coincidence events of all LORi passing through the target object, 2. The time calibration method of claim 1, further comprising the step of reconstructing the radioactivity image based on all coincidence events on all response lines LORi passing through the object using a filtered backprojection or iterative method.

7. determining pixel points Pi at which each of the LORi passing through the object of interest intersects with the radioactivity image, 2. The time calibration method according to claim 1, further comprising the step of determining pixel points Pi at which each of the selected lines of response LORi intersects with the radioactivity image based on a ray tracing method.

8. determining the pixel value-time difference statistical distribution Ti corresponding to each LORi based on the pixel points Pi, calculating, for each pixel point Pi, the time difference from each pixel Pi to the end point of the corresponding line of response LORi, and recording the pixel value of each pixel point Pi; determining a plurality of equally spaced time difference intervals, and accumulating pixel values ​​of pixel points Pi whose time differences fall within each of the time difference intervals based on the time differences of the pixel points Pi; determining the pixel value-time difference statistical distribution Ti corresponding to each response line LORi by setting the time difference interval as a horizontal step size and the cumulative pixel values ​​of pixel points within each step size as a vertical step size; 2. The time calibration method of claim 1, comprising:

9. determining a coincidence event-time difference statistical distribution Mi corresponding to each LORi based on the coincidence events Ki on each LORi, 9. The time calibration method according to claim 8, further comprising a step of determining the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Ti as a step size, and determining the coincidence count event-time difference statistical distribution Mi corresponding to each response line LORi by setting the cumulative value of coincidence count events whose time difference falls within each of the step sizes as a vertical axis.

10. a step of calculating a maximum value Yi of an inner product of the pixel value-time difference statistical distribution Ti and the coincidence count event-time difference statistical distribution Mi, and determining the time offset difference value δΔi corresponding to the maximum value Yi of each response line LORi, 2. The time calibration method according to claim 1, further comprising the steps of: shifting the coincidence counting event-time difference statistical distribution Mi using the pixel value-time difference statistical distribution Ti as a reference; calculating the inner product of the pixel value-time difference statistical distribution Ti and the coincidence counting event-time difference statistical distribution Mi; and statistically obtaining the amount of shift of the coincidence counting event-time difference statistical distribution Mi when the inner product reaches the maximum value Yi, wherein the amount of shift is the offset difference value δΔi.

11. determining a time calibration value based on the offset difference value δΔi, determining a relationship between time offsets δci and δdi of scintillators ci and di at two ends of each line of response LORi based on the time offset difference values ​​δΔi, where δci - δdi = δΔi; determining time offsets δci and δdi of the scintillators ci and di at the two ends of each line of response LORi by solving simultaneous equations using a fitting method, wherein the time offsets δci and δdi are time calibration values ​​of the scintillators ci and di; 2. The time calibration method of claim 1, comprising:

12. 12. The time calibration method of claim 11, further comprising the step of performing time calibration on the sampling data based on the determined time calibration value, i.e., performing calibration on time data corresponding to the scintillators c and di in the sampling data based on the time offsets δc and δd of the scintillators c and di.

13. 13. The time calibration method of claim 12, wherein the step of performing time calibration on the sampling data based on the determined time calibration value includes the step of subtracting the time calibration values ​​δc and δd from the time data tc and td corresponding to the scintillators c and di in the sampling data, respectively.

14. determining response lines LORi passing through the object and coincidence events K on each LORi based on sampling data of the object, where i represents a number and i≧1; acquiring a radioactivity image based on all coincidence events of all response lines LORi passing through the target object; A step of selecting a response line LORj whose number of coincidence counting events satisfies a preset condition based on all response lines LORi passing through the target object, where j represents a number and j≧1. A step of selecting a response line LORj whose number of coincidence counting events satisfies a preset condition; determining pixel points Pj where each of the selected response lines LORj intersects with the radiation image, and determining pixel value-time difference statistical distributions Tj corresponding to each response line LORj based on the pixel points Pj; determining a coincidence event-time difference statistical distribution Mj corresponding to each selected line of response LORj; calculating a maximum value Yj of an inner product of the pixel value-time difference statistical distribution Tj and the coincidence counting event-time difference statistical distribution Mj based on the pixel value-time difference statistical distribution Tj and the coincidence counting event-time difference statistical distribution Mj corresponding to each selected response line LORj, and determining a time offset difference value δΔj corresponding to the maximum value Yj of each response line LORj; determining a time calibration value based on the offset difference value δΔj; A time calibration method, including:

15. 15. The time calibration method of claim 14, wherein the response lines LORi passing through the target object include response lines LORi having at least one intersection with the target object, or response lines LORi that circumscribe the target object or intersect the target object.

16. determining LORi passing through the object and coincidence events K on each LORi based on the sampling data, determining a line of response LOR corresponding to all coincidence counting events and each coincidence counting event based on the sampling data; selecting all response lines LORi passing through the object and coincidence events K on each LORi; 15. The time calibration method of claim 14, comprising:

17. selecting all response lines LORi passing through the object and coincidence events K on each LORi, 17. The time calibration method according to claim 16, further comprising the step of determining, based on prior information, whether a straight line on which the line of response LOR exists has an intersection with the object of interest.

18. 18. The time calibration method of claim 17, wherein the prior information includes the number of scintillators IP between spaced apart scintillators at two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects the straight line on which the line of response LOR exists.

19. acquiring the radioactivity image based on all coincidence events of all LORi passing through the target object, 15. The time calibration method of claim 14, further comprising the step of reconstructing the radioactivity image based on all coincidence events on all response lines LORi passing through the object using filtered back projection or iterative methods.

20. A step of selecting a response line LORj whose number of coincidence counting events satisfies a preset condition based on all response lines LORi passing through the target object, establishing a reference value for comparing the number of coincidence events; determining whether the number of coincidence events is greater than the reference value; storing the response line LORj in which the number of coincidence events is greater than the reference value; 15. The time calibration method of claim 14, comprising:

21. determining pixel points Pj where each of the selected lines of response LORj intersects the radiation image, 15. A time calibration method according to claim 14, characterized in that it comprises the step of determining, based on a ray tracing method, pixel points Pj at which each of said lines of response LORj intersects with said radioactivity image.

22. determining a pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on each of the pixel points Pj, calculating, for each pixel point Pj, the time difference from each pixel point Pj to the end point of the corresponding line of response LORj and recording the pixel value of each pixel point Pj; determining a plurality of equally spaced time difference intervals, and accumulating pixel values ​​of pixel points Pj whose time differences fall within each of the time difference intervals based on the time differences of the pixel points Pj; determining the pixel value-time difference statistical distribution Tj corresponding to each response line LORj by setting the time difference interval as a horizontal step size and the cumulative pixel values ​​of pixel points falling within each step size as a vertical step size; 15. The time calibration method of claim 14, comprising:

23. determining the coincidence event-time difference statistical distribution Mj corresponding to each selected line of response LORj, 23. The time calibration method according to claim 22, further comprising a step of determining the coincidence counting event-time difference statistical distribution Mj corresponding to each response line LORj by setting the horizontal axis step size of the pixel value-time difference statistical distribution Tj as a step size, and setting the vertical axis as the cumulative value of coincidence counting events whose time differences fall within each of the step sizes.

24. calculating a maximum value Yj of an inner product between the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj, and determining a time offset difference value δΔj corresponding to the maximum value for each response line LORj; the method includes a step of shifting the coincidence counting event-time difference statistical distribution Mj using the pixel value-time difference statistical distribution Tj as a reference, calculating the inner product of the pixel value-time difference statistical distribution Tj and the coincidence counting event-time difference statistical distribution Mj, and statistically obtaining the amount of shift of the coincidence counting event-time difference statistical distribution Mj when the inner product reaches the maximum value Yj; 15. The time calibration method of claim 14, wherein the shift amount is the offset difference value δΔj.

25. determining a time calibration value based on the offset difference value δΔj, determining a relationship between time offsets δcj and δdj of scintillators cj and dj at the two ends of each line of response LORj based on the offset difference values ​​δΔj, where δcj - δdj = δΔj; determining the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each line of response LORj by solving simultaneous equations using a fitting method, wherein the time offsets δcj and δdj are time calibration values ​​of the scintillators cj and dj; 15. The time calibration method of claim 14, comprising:

26. 15. The time calibration method of claim 14, further comprising the step of performing time calibration on the sampling data based on the determined time calibration value, i.e., performing calibration on time data corresponding to scintillators cj and dj in the sampling data based on the time offsets δcj and δdj of scintillators cj and dj.

27. 27. The time calibration method of claim 26, wherein the step of performing time calibration on the sampling data based on the determined time calibration value includes the step of subtracting the time calibration values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillators cj and dj in the sampling data, respectively.

28. a coincidence event sorting module configured to determine response lines LORi passing through the object and coincidence events K on each LORi based on sampling data of the object, where i represents a number and i≧1; a radioactivity image reconstruction module configured to acquire a radioactivity 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 determine pixel points Pi at which each of the response lines LORi passing through the target object intersects with the radiation image, and to determine pixel value-time difference statistical distribution Ti corresponding to each of the LORi based on the pixel points Pi; a coincidence event-time difference statistical distribution acquisition module configured to determine a coincidence event-time difference statistical distribution Mi corresponding to each response line LORi; a calculation module configured to calculate a maximum value Yi of an inner product of the pixel value-time difference statistical distribution Ti and the coincidence event-time difference statistical distribution Mi, and to determine a time offset difference value δΔi corresponding to the maximum value Yi of each response line LORi; a time calibration value acquisition module configured to determine a time calibration value based on the offset difference value δΔi; A time calibration device comprising:

29. the sampling data includes scintillator IP information and time information of a pulse signal; 29. The time calibration device of claim 28, wherein the coincidence event selection module is further configured to determine energy information of the pulse signal based on the sampling data, determine a coincidence event based on the time information and the energy information of the pulse signal, and determine a line of response LOR corresponding to the coincidence event based on the scintillator IP information.

30. 30. The time calibration device of claim 29, further comprising a recording module configured to record the time difference between the coincidence counting events and scintillator IP information of the scintillators at the two ends of the corresponding response lines LOR.

31. 29. The time calibration device of claim 28, wherein the coincidence event sorting module is further configured to determine, based on prior information, whether a straight line on which the response line LOR exists has an intersection with the target object, and to determine, based on the number of intersections, whether the response line LOR passes through the target object.

32. 32. The time calibration device of claim 31, wherein the prior information includes the number of scintillators IP between spaced apart scintillators at two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects the straight line on which the line of response LOR exists.

33. 29. The time calibration device of claim 28, wherein the radiological image reconstruction module is configured to reconstruct the radiological image using filtered backprojection or an iterative method.

34. The time calibration device of claim 28, wherein the pixel value-time difference statistical distribution acquisition module is configured to determine pixel points Pi where the selected response lines LORi intersect with the radioactivity image based on a ray tracing method.

35. The pixel value-time difference statistical distribution acquisition module: a pixel time difference acquisition module configured to calculate a time difference from each pixel point Pi to an end point of a corresponding line of response LORi and record a pixel value of each pixel point Pi; a pixel value accumulation module configured to determine a plurality of equally spaced time difference intervals and accumulate pixel values ​​of pixel points Pi whose time differences fall within each of the time difference intervals based on the time differences of each pixel point Pi; Equipped with The time calibration device of claim 34, wherein the pixel value-time difference statistical distribution acquisition module is configured to determine the pixel value-time difference statistical distribution Ti corresponding to each response line LORi by taking the time difference interval as a horizontal axis step size and the accumulated pixel value of pixel points falling within each step size as a vertical axis.

36. The coincidence counting event-time difference statistical distribution acquisition module, The time calibration device of claim 35, wherein the coincidence counting event-time difference statistical distribution Mi corresponding to each response line LORi is determined by setting the horizontal axis step size of the pixel value-time difference statistical distribution Ti as a step size, and setting the vertical axis as the cumulative value of coincidence counting events whose time differences fall within each of the step sizes.

37. 29. The time calibration device of claim 28, wherein the time calibration value acquisition module is further configured to determine a relationship between time offsets δci and δdi of scintillators ci and di at two ends of each response line LORi based on the time offset difference value δΔi, where δci - δdi = δΔi, and to determine the time offsets δci and δdi of the scintillators ci and di at the two ends of each response line LORi by solving a system of equations using a fitting method, wherein the time offsets δci and δdi are time calibration values ​​of the scintillators ci and di.

38. 29. The time calibration device of claim 28, further comprising a calibration module configured to perform time calibration on time information of pulse signals in the sampling data based on the determined time calibration value, wherein performing the time calibration includes subtracting the time calibration values ​​δci and δdi from the time data tci and tdi corresponding to the scintillators ci and di, respectively, in the sampling data.

39. a first coincidence event sorting module configured to determine, based on sampling data of the target object, response lines LORi passing through the target object and coincidence events K on each LORi, where i represents a number and i≧1; a radioactivity image reconstruction module configured to acquire a radioactivity image based on all coincidence events of all response lines LORi passing through the target object; a second coincidence event sorting module configured to sort out a response line LORj whose number of coincidence events meets a preset reference value based on all response lines LORi passing through the target object, where j represents a number and j≧1; a pixel value-time difference statistical distribution acquisition module configured to determine pixel points Pj where each of the selected response lines LORj intersects with the radiation image, and to determine pixel value-time difference statistical distributions Tj corresponding to each response line LORj based on the pixel points Pj; a coincidence event-time difference statistical distribution acquisition module configured to determine a coincidence event-time difference statistical distribution Mj corresponding to each selected line of response LORj; a calculation module configured to calculate a maximum value Yj of an inner product between the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj, and to determine a time offset difference value δΔj corresponding to the maximum value Yj of each line of response LORj; a time calibration value acquisition module configured to determine a time calibration value based on the offset difference value δΔj; A time calibration device comprising:

40. the sampling data includes scintillator IP information and time information of a pulse signal; 40. The time calibration device of claim 39, wherein the coincidence event selection module is further configured to determine energy information of the pulse signal based on the sampling data, determine coincidence events based on time information and the energy information of the pulse signal, and determine a line of response LOR corresponding to the coincidence event based on the scintillator IP information.

41. 41. The time calibration device of claim 40, further comprising a recording module configured to record the time difference between the coincidence counting events and scintillator IP information of the scintillators at the two ends of the corresponding response lines LOR.

42. 40. The time calibration device of claim 39, wherein the first coincidence event selection module is configured to determine, based on prior information, whether a straight line on which the response line LOR exists has an intersection with the target object, and to determine, based on the number of intersections, whether the response line LOR passes through the target object.

43. 43. The time calibration device of claim 42, wherein the prior information includes the number of scintillators IP between spaced apart scintillators at two ends of the line of response LOR, and the number of scintillators IP between the spaced apart scintillators is determined based on whether the inner diameter of the target object in various directions intersects the straight line on which the line of response LOR exists.

44. 40. The time calibration device of claim 39, wherein the radiological image reconstruction module is configured to reconstruct the radiological image using filtered backprojection or an iterative method.

45. the second coincidence event sorting module comprising: a reference value setting module configured to set a reference value for comparing the number of coincidence events; a determination module configured to determine whether the number of coincidence events is greater than the reference value; a storage module configured to store lines of response LOR where the number of coincidence events is greater than the reference value; 40. A time calibration device according to claim 39, comprising:

46. The time calibration device of claim 39, wherein the pixel value-time difference statistical distribution acquisition module is configured to determine pixel points Pj where the selected response lines LORj intersect with the radioactivity image based on a ray tracing method.

47. The pixel value-time difference statistical distribution acquisition module: a pixel time difference acquisition module configured to calculate the time difference from each pixel point Pj to the end point of the corresponding line of response LORj and record the pixel value of each pixel point Pj; a pixel value accumulation module configured to determine a plurality of equally spaced time difference intervals and accumulate pixel values ​​of pixel points Pj whose time differences fall within each of the time difference intervals based on the time differences of each pixel point Pj; Equipped with The time calibration device of claim 46, wherein the pixel value-time difference statistical distribution acquisition module is configured to determine the pixel value-time difference statistical distribution Tj corresponding to each response line LORj by taking the time difference interval as a horizontal axis step size and the accumulated pixel values ​​of pixel points falling within each step size as a vertical axis.

48. The coincidence counting event-time difference statistical distribution acquisition module, The time calibration device of claim 39, characterized in that it is configured to determine the coincidence counting event-time difference statistical distribution Mj corresponding to each response line LORj by determining the horizontal axis by setting the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and by setting the vertical axis to the cumulative value of coincidence counting events whose time differences fall within each of the step sizes.

49. 40. The time calibration device of claim 39, wherein the time calibration value acquisition module is further configured to determine a relationship between the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each line of response LORj based on the time offset difference value δ△j, where δcj - δdj = δ△j, and to determine the time offsets δcj and δdj of the scintillators cj and dj at the two ends of each line of response LORj by solving a system of equations using a fitting method, wherein the time offsets δcj and δdj are time calibration values ​​of the scintillators cj and dj.

50. 40. The time calibration device of claim 39, further comprising a calibration module configured to perform time calibration on time information of pulse signals in the sampling data based on the determined time calibration value, wherein performing the time calibration includes subtracting the time calibration values ​​δci and δdi from the time data tci and tdi corresponding to the scintillators ci and di, respectively, in the sampling data.

51. A digitizing apparatus comprising a time calibration device according to any one of claims 28 to 50, the digitizing apparatus detecting an object to be detected using a detector, acquiring sampling data using a sampling module, calibrating the sampling data using the time calibration device, acquiring calibrated time data, and thereby forming a digital image based on the calibrated time data.

52. A computer device comprising: a memory; a processor; and a computer program stored in the memory and executable by the processor for carrying out the steps of the time calibration method according to any one of claims 1 to 27.

53. A computer-readable storage medium storing a computer program executable by a processor to carry out the steps of the time calibration method according to any one of claims 1 to 27.

Images