Shell source-based time correction method, device, equipment and storage medium

Abstract

The application discloses a shell source-based time correction method and device, equipment and a storage medium. The method comprises the following steps: based on sampling data, acquiring response lines passing through a shell source and coincidence events on each response line, recording corresponding coincidence events at both ends of each response line and time differences of the coincidence events on each response line; based on all coincidence events of all response lines passing through the shell source, acquiring an activity image; based on all response lines passing through the shell source, screening response lines with a number of coincidence events satisfying a preset condition; acquiring pixel points intersected by each screened response line and the activity image, and respectively acquiring pixel value-time difference statistical distributions corresponding to each response line based on the pixel points; acquiring coincidence event-time difference statistical distributions corresponding to each screened response line; determining the number of corresponding peak values of the two distributions; and selecting a mode matched with the number of corresponding peak values to acquire a time correction value. The application can improve the time correction efficiency of the shell source and improve the operation safety.

Description

Technical Field

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

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

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

[0004] like Figure 1 Assuming the two gamma photons generated by the annihilation event are detected by points A (scintillation crystal bar A) and B (scintillation crystal bar B) of the PET detector, the line connecting AB is called a line of response (LOR). Theoretically, if the times tA and tB at which the two scintillation crystal bars A and B detect the gamma photons are accurate enough, the location D where the annihilation occurred can be precisely located. Let the length of AB be L, the distance from point D to point A be d, and the speed of light be C, then d = L / 2 + C / 2 * (tA - tB). In other words, the precise arrival time of the collected gamma photons can be used to directly calculate the location of the nuclide annihilation, eliminating the need for complex image reconstruction methods to obtain PET images.

[0005] However, in actual systems, due to differences in the material, optical path length, and electronic delays of the detector's individual scintillator bars, the bars experience background delay, or time offset. This results in the actual detection times of points A and B being tA' and tB'. Assuming tA' = tA + δA and tB' = tB + δB, δA and δB are the time offsets between scintillator bars A and B, respectively. Due to this time offset, the distance from point A to the radionuclide annihilation location calculated based on tA' and tB' is d' = L / 2 + C / 2*(tA' - tB') = d+C / 2*(δA - δB), and d = d' - C / 2*(δA - δB) = L / 2 + C / 2*(tA' - tB') - C / 2*(δA - δB). This means that the obtained radionuclide annihilation location deviates from the actual annihilation location, D.

[0006] In order to obtain the accurate annihilation position, the time data detected by the scintillation crystal needs to be time corrected.

[0007] Typically, the deviations δ1 to δn between the actual measured time values ​​of all n scintillation crystal bars in the detector and the theoretical arrival time of γ photons are obtained, and the obtained deviations are corrected to the actual collected time information. This process is called time deviation correction, that is, time correction of scintillation crystals. Therefore, the most important task in the time correction process is to obtain the deviations δ1 to δn between the actual measured time values ​​of all scintillation crystal bars and the theoretical arrival time of γ photons.

[0008] In the time correction method in the prior art, the shell source is a commonly used radiation source. When using the shell source, in order to obtain the actual measured time value of the scintillation crystal bar and the theoretical γ photon arrival time deviation δ1~δn, it is necessary to characterize the difference in time deviation of the scintillation crystal bars at both ends of the response line LOR obtained based on the shell source. Since the shell source and the response line LOR have different situations of being tangent or intersecting, when characterizing the time deviation difference of the scintillation crystal bars at both ends of the response line LOR obtained based on the shell source, different characterization methods are theoretically required for different situations, and each method is not universal. At present, it is impossible to know in advance the intersection or tangency of the shell source and the response line LOR. Therefore, when characterizing the time deviation difference of the scintillation crystal bars at both ends of the response line LOR, Gaussian fitting is usually used to obtain the mean of the time difference that meets the event, and the time deviation difference of the scintillation crystal bars at both ends of the response line LOR is characterized based on the time difference mean. Characterization using Gaussian fitting requires collecting enough counts for a long time, at least 1 hour; or requires high drug activity, but high drug activity will also lead to more random events and increase measurement errors.

[0009] The content of this background technology description is only for facilitating understanding of the relevant technology in this field and is not regarded as an admission of the prior art. Summary of the Invention

[0010] Therefore, the present application intends to provide a shell source-based time correction method, device, equipment and storage medium, which can solve at least one problem existing in the prior art.

[0011] According to the first aspect of the present application, a time correction method based on a shell source is provided, comprising: based on sampling data, obtaining response lines LORi passing through the shell source and coincident events Ki on each response line LORi, wherein i represents the number, i≥1, and recording the time difference of the coincident events corresponding to both ends of each response line LORi and the coincident events on each response line LORi; obtaining an activity image based on all coincident events of all response lines LORi passing through the shell source; screening response lines LORj whose number of coincident events meets a preset condition based on all response lines LORi passing through the shell source, wherein j represents the number, j≥1; obtaining pixel points Pj where each screened response line LORj intersects with the activity image, and obtaining pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel points Pj; obtaining coincident event-time difference statistical distribution Mj corresponding to each screened response line LORj; determining the number of corresponding peaks of the pixel value-time difference statistical distribution Tj and the coincident event-time difference statistical distribution Mj; and based on the number of corresponding peaks, selecting a method that matches the number of corresponding peaks to obtain a time correction value.

[0012] According to one embodiment of the present application, a method of matching the number of corresponding peaks is selected to obtain a time correction value, including: based on the received pixel value-time difference statistical distribution Tj and the number of corresponding peaks that conform to the event-time difference statistical distribution Mj, a time deviation difference δ corresponding to each response line LORj is calculated in a matching manner. △ j; based on the difference δ △ j, obtain the time correction value.

[0013] According to one embodiment of the present application, the number of corresponding peaks of the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj is one or two.

[0014] According to one embodiment of the present application, the time deviation difference δ corresponding to each response line LORj is calculated in a matching manner. △ j, including: if the number of the corresponding peaks is one, calculate the mean time difference Ej of all the events on the response line LORj to obtain the time deviation difference δ corresponding to the response line LORj △j; if the number of corresponding peaks is two, the maximum value Yj of the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj is calculated to obtain the time deviation difference δ corresponding to the maximum value Yj △ j.

[0015] According to one embodiment of the present application, the time difference mean Ej of all the matching events on the response line LORj is calculated, including: counting the number of matching events on the response line LORj, and calculating the sum mean of the time differences of the number of matching events to obtain the time difference mean Ej of all the matching events on the response line LORj.

[0016] According to one embodiment of the present application, the time deviation difference δ corresponding to the maximum value Yj is obtained. △ j, including: taking the pixel value-time difference statistical distribution Tj as the benchmark, translating the event-time difference statistical distribution Mj, calculating the inner product Yj of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and statistically obtaining the translation amount that conforms to the event-time difference statistical distribution Mj when the inner product is the maximum value Yj, and the translation amount is the difference δ △ j.

[0017] According to one embodiment of the present application, based on the difference δ △ j, obtaining a time correction value, including: based on the difference δ △ j, and obtain the relationship between the time deviations δcj and δdj of the scintillator crystals cj and dj at both ends of each response line LORj. δcj-δdj=δ Δ j; a set of simultaneous equations, and the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj are obtained by a fitting method, where the δcj and δdj are time correction values.

[0018] According to one embodiment of the present application, the time correction method further includes: performing time correction on the sampling data obtained based on the detection module based on the acquired time correction value, that is: based on the time deviations δcj and δdj of the scintillation crystals cj and dj, correcting the time data corresponding to the scintillation crystals cj and dj in the sampling data.

[0019] According to an embodiment of the present application, correcting the time data corresponding to the scintillation crystals cj and dj in the sampled data includes: subtracting the time correction values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillation crystals cj and dj in the sampled data, respectively.

[0020] According to an embodiment of the present application, the response line LORi passing through the shell source includes: the response line LORi and the shell source have at least one intersection point, or the response line LORi is tangent to or intersects the shell source.

[0021] According to one embodiment of the present application, based on the sampling data, the response lines LORi passing through the shell source and the coincident events Ki on each response line LORi are obtained, including: obtaining all coincident events and the response lines LOR corresponding to each coincident event based on the sampling data; screening all response lines LORi passing through the shell source and the coincident events Ki on each response line LORi.

[0022] According to an embodiment of the present application, screening all response lines LORi passing through the shell source and the matching events Ki on each response line LORi includes: determining whether the straight line where the response line LOR is located intersects the shell source based on prior information.

[0023] According to one embodiment of the present application, the prior information includes the IP number of the scintillation crystals spaced between the scintillation crystals at both ends of the response line LOR, and the IP number of the spaced scintillation crystals is determined based on whether the inner diameter of the shell source in each direction intersects the straight line where the response line LOR is located.

[0024] According to one embodiment of the present application, an activity image is acquired based on all coincident events of all response lines LORi passing through the shell source, including: reconstructing the activity image using filtered back projection or iterative method based on all coincident events of all response lines LORi passing through the shell source.

[0025] According to one embodiment of the present application, based on all response lines LORi passing through the shell source, the response lines LORj whose number of matching events meets the preset conditions are screened, including: setting a benchmark value for comparing the number of matching events; determining whether the number of matching events is greater than the benchmark value; and storing the response lines LOR whose number of matching events is greater than the benchmark value.

[0026] According to one embodiment of the present application, obtaining pixel points Pj where each screened response line LORj intersects with the activity image includes: obtaining pixel points Pj where each screened response line LORj intersects with the activity image based on a ray tracing method.

[0027] According to one embodiment of the present application, the pixel value-time difference statistical distribution Tj corresponding to each response line LORj is obtained based on the pixel point Pj, including: calculating the time difference from the pixel point Pj to the two end points of the corresponding response line LORj one by one, and recording the pixel value of each pixel point Pj; determining a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculating the cumulative value of the pixel value of the pixel point Pj whose time difference falls into each time difference interval; using the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis, obtaining the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

[0028] According to one embodiment of the present application, the statistical distribution Mj of the conforming events-time difference corresponding to each screened response line LORj is obtained, including: determining the horizontal axis with the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and using the cumulative value of the conforming events whose time difference falls into each step size as the vertical axis, to obtain the statistical distribution Mj of the conforming events-time difference corresponding to each response line LORj.

[0029] According to a second aspect of the present application, a time correction device based on a shell source is provided, comprising: a first coincidence event screening module configured to obtain, based on sampling data, response lines LORi passing through the shell source and coincidence events Ki on each response line LORi, where i represents the number, i ≥ 1; an activity image reconstruction module configured to obtain an activity image based on all coincidence events of all response lines LORi passing through the shell source; a second coincidence event screening module configured to screen, based on all response lines LORi passing through the shell source, response lines LORj whose number of coincidence events meets a preset reference value, where j represents the number, j ≥ 1; a pixel value-time difference The statistical distribution acquisition module is configured to obtain each pixel point Pj where each selected response line LORj intersects with the activity image, and obtains the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel point Pj; the event-time difference statistical distribution acquisition module is configured to obtain the event-time difference statistical distribution Mj corresponding to each selected response line LORj; the statistics module is configured to count the corresponding peak values ​​of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj; the matching module is configured to match the time deviation difference δ corresponding to each response line LORj based on the corresponding peak value number. △ j calculation method; a calculation module configured to calculate the time deviation difference δ corresponding to each response line LORj according to the matching calculation method △ j; a time correction value acquisition module configured to obtain a time correction value based on the δ △ jGet the time correction value.

[0030] According to an embodiment of the present application, the number of corresponding peaks of the pixel value-time difference statistical distribution Tj counted by the statistical module and the event-time difference statistical distribution Mj is one or two.

[0031] According to one embodiment of the present application, the time deviation difference δ corresponding to each response line LORj is selected △ j, the matching module is further configured as follows: if the number of corresponding peaks is one, the calculation module calculates the mean time difference Ej of all matching events on the response line LORj to obtain the time deviation difference δ corresponding to the response line LORj △j; If the number of corresponding peaks is two, the calculation module calculates the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj to obtain the time deviation difference δ corresponding to the maximum value Yj of the inner product △ j.

[0032] According to one embodiment of the present application, in order to calculate the time difference mean Ej of all matching events on the response line LORj, the calculation module is further configured to: count the number of matching events on the response line LORj, and calculate the sum mean of the time differences of the number of matching events to obtain the time difference mean Ej of all matching events on the response line LORj.

[0033] According to one embodiment of the present application, in order to obtain the time deviation difference δ corresponding to the maximum value Yj of the inner product, △ j, the calculation module is further configured to: take the pixel value-time difference statistical distribution Tj as the benchmark, translate the event-time difference statistical distribution Mj, calculate the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and calculate the translation amount of the event-time difference statistical distribution Mj when the inner product is the maximum value Yj. The translation amount is δ △ j.

[0034] According to one embodiment of the present application, the sampling data includes scintillation crystal number information and time information of the pulse signal; the coincidence event screening module is further configured to obtain energy information of the pulse signal based on the sampling data, and obtain coincidence events based on the time information and energy information of the pulse signal, and obtain the response line LOR corresponding to the coincidence event based on the scintillation crystal number information.

[0035] According to an embodiment of the present application, the time correction device further includes: a recording module configured to record the time difference of the event and the corresponding scintillation crystal number information of the detection modules at both ends of the response line LOR.

[0036] According to an embodiment of the present application, the first coincidence event screening module is further configured to determine whether the line on which the response line LOR is located has an intersection with the shell source based on prior information, and determine whether the response line LOR passes through the shell source based on the number of intersections.

[0037] According to one embodiment of the present application, the prior information includes the IP number of the scintillation crystals spaced between the scintillation crystals of the detection modules at both ends of the response line LOR, and the IP number of the spaced scintillation crystals is determined based on whether the inner diameter of the shell source in each direction intersects the straight line where the response line LOR is located.

[0038] According to one embodiment of the present application, the activity image reconstruction module is configured to reconstruct the activity image using filtered back projection or an iterative method.

[0039] According to one embodiment of the present application, the second conforming event screening module includes: a reference value setting module for setting a reference value for comparing the number of conforming events; a determination module for determining whether the number of conforming events is greater than the reference value; and a storage module for storing a response line LOR indicating whether the number of conforming events is greater than the reference value.

[0040] According to one embodiment of the present application, the pixel value-time difference statistical distribution acquisition module is configured to acquire the pixel point Pj where the selected response line LORj intersects the activity image based on a ray tracing method.

[0041] According to one embodiment of the present application, the pixel value-time difference statistical distribution acquisition module includes: a pixel point time difference acquisition module, which is used to calculate the time difference from the pixel point Pj to the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj; a pixel value accumulation module, which is used to determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculate the cumulative value of the pixel value of the pixel point Pj whose time difference falls into each time difference interval; the pixel value-time difference statistical distribution acquisition module is configured to use the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

[0042] According to one embodiment of the present application, in order to obtain the statistical distribution Mi of the coincident event-time difference corresponding to each response line LORi, the coincident event-time difference statistical distribution acquisition module is further configured as: the horizontal axis is determined with the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and the vertical axis is determined with the cumulative value of the coincident event whose time difference falls into each step size, to obtain the statistical distribution Mj of the coincident event-time difference corresponding to each response line LORj.

[0043] According to one embodiment of the present application, the time correction value acquisition module is further configured to: △ j obtains the relationship between the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj, δcj-δdj=δj; the simultaneous equation group is used to obtain the time correction values ​​of the scintillation crystals cj and dj at both ends of each response line LORj by fitting method.

[0044] According to one embodiment of the present application, the time correction device further includes a correction module, which is configured to correct the time information of the pulse signal in the sampled data based on the time correction value: the time data t corresponding to the scintillation crystals cj and dj in the sampled data cj, t dj Subtract the time correction values ​​δcj and δdj respectively.

[0045] According to a third aspect of the present application, a digitization device is provided, comprising: a shell source-based time correction device as described above, wherein the digitization device uses a detector to detect an object to be detected, uses a sampling module to obtain sampling data, uses the time correction device to correct the sampling data and obtains the corrected time data, thereby forming a digitized image based on the corrected time data.

[0046] According to a fourth aspect of the present application, a computer device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program implements the steps of the time correction method described above when executed by the processor.

[0047] According to a fifth aspect of the present application, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the time correction method described above are implemented.

[0048] The solution of the embodiment of the present application obtains the pixel value-time difference statistical distribution Tj corresponding to each response line LORj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj, determines the corresponding peak number of Tj and Mj, and obtains the situation of the mean corresponding peak of the time difference of the coincidence event generated by the annihilation of the intersection position, that is, the intersection or tangency of the response line LOR and the shell source is obtained, and based on the number of corresponding peaks of Tj and Mj, the matching control module selects a method that matches the corresponding peak number to obtain the time correction value of the detection module, avoiding the use of Gaussian fitting for time correction, improving the efficiency of time correction based on the shell source, and improving operational safety.

[0049] The optional features and other effects of the embodiments of the present application are partially described below, and partially can be understood by reading this document. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The embodiments of the present application are described in detail with reference to the accompanying drawings. The elements shown are not limited to the scale shown in the drawings. The same or similar reference numerals in the drawings represent the same or similar elements, wherein:

[0051] Figure 1 shows a schematic diagram of annihilation position deviation according to the prior art;

[0052] Figure 2 A flowchart of a shell source-based time correction method according to an embodiment of the present application is shown;

[0053] Figure 3A schematic diagram showing that the number of corresponding peaks of Tj and Mj is two according to an embodiment of the present application;

[0054] Figure 4 An exemplary module diagram of a shell source-based time correction device according to an embodiment of the application is shown. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0056] As used herein, the term "including" and its variations represent open inclusion, i.e., "including but not limited to." Unless otherwise stated, the term "or" means "and / or." The term "based on" means "based at least in part on." The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment." The term "another embodiment" means "at least one additional embodiment." The terms "first," "second," etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0057] Some preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be noted that the following description is for illustrative purposes only and is not intended to limit the scope of protection of the present application.

[0058] Figure 2 is an exemplary flow chart of a shell source-based time correction method according to some embodiments of the present application. Specifically, Figure 2 As shown, the time correction method may include the following steps 2, S120, S130, S140, S150, S160, and S170.

[0059] Step S110: Based on the sampling data obtained by the detection module, the response lines LORi (i≥1) passing through the shell source and the coincident events Ki (i≥1) on each response line LORi are obtained, and the time difference between the coincident events corresponding to the two ends of each response line LORi and the coincident events on each response line LORi is recorded;

[0060] In the embodiment of the present application, the detection module samples the pulse signal obtained based on the shell source to obtain sampling data.

[0061] In the embodiment of the present application, the shell source may be a ring-shaped radiation source with a regular or irregular shape, or may be a radiation source similar to a shell source formed by rotating a line source.

[0062] In an embodiment of the present application, the detection module may be a detection module in a variety of medical imaging devices such as PET, CT, MR, etc. The detection module includes a detector, and the detector includes a scintillation crystal and a photoelectric conversion element.

[0063] In one example of the present application, the detection module can be a PET detection module, whose detector includes a scintillation crystal and a photoelectric conversion element. The scintillation crystal includes but is not limited to yttrium lutetium silicate scintillation crystal, which is used to convert gamma rays into visible light, and the photoelectric conversion element includes but is not limited to a silicon photomultiplier (SiPM), which is used to convert visible light into a pulse signal.

[0064] In the embodiments of the present application, the pulse signal should be understood as any pulse signal that can be sampled, and its essence is a physical quantity that undergoes a sudden change in a short period of time and then quickly returns to its initial value, and this physical quantity has certain characteristics. In the present application, the pulse signal especially includes a scintillation pulse, and multiple embodiments will be described herein using a scintillation pulse as an example, in which the pulse signal and the scintillation pulse can be interchangeable. For example, in some embodiments, the scintillation pulse typically has a rising edge and a falling edge, and the rising edge and the falling edge can be represented by a function model. In some embodiments, the pulse signal is a scintillation pulse signal. For example, the scintillation pulse corresponding to a gamma photon typically exhibits a relatively fast rising edge and a relatively slow falling edge, the rising edge can be represented by a linear function, and the falling edge can be represented by an exponential function.

[0065] In other embodiments, the waveform of the pulse signal may be a triangular wave, a rectangular wave, a sine wave, a cosine wave or other shapes of waves, which will not be described in detail here.

[0066] In the embodiment of the present application, the pulse signal may be in the form of an electrical pulse signal, and its corresponding characteristics may be the voltage and current of the electrical pulse signal.

[0067] In an embodiment of the present application, sampling of the pulse signal obtained based on the shell source is implemented through a sampling module. In an example of the present application, the sampling module is a multi-voltage threshold (MVT) sampling module, which performs multi-voltage threshold sampling on the pulse signal. Specifically, the multi-voltage threshold sampling module includes a threshold setting module, a comparison module, a time-to-digital conversion module, and an information storage module. The threshold setting module is used to set the sampling threshold; the comparison module is used to compare the pulse signal with the threshold and output a transition signal; the time-to-digital conversion module is used to perform time sampling on the transition signal to obtain the time information of the pulse signal, and the information storage module stores the scintillation crystal number information of the detection module and the time information of the pulse signal. MVT sampling of the pulse signal by the MVT sampling module is implemented based on an FPGA chip. The FPGA chip integrates DAC, LVDS, and TDC. The DAC integrated in the FPGA chip is used as a threshold setting module, the LVDS is used as a comparison module, and the TDC is used as a time conversion module. The DAC is used to preset thresholds for LVDS, such as voltage thresholds V1, V2, V3, and V4. The input pulse signal is compared with the LVDS thresholds V1-V4, and sampling is performed at times t1-t4 corresponding to the rising edge of the jump signal, and sampling is performed at times t5-t8 corresponding to the falling edge of the jump signal to obtain sampling data including voltage-time pairs (V1, t1), (V2, t2), (V3, t3), (V4, t4), (V4, t5), (V3, t6), (V2, t7), and (V1, t8), where t1-t8 are time data.

[0068] In the embodiment of the present application, the sampled data includes the scintillation crystal number information of the detection module and the time information of the pulse signal. The time data t1 can represent the time information of the pulse signal, and the scintillation crystal number information of the detection module can be determined based on the time data t1-t4 of the pulse signal.

[0069] In the embodiment of the present application, the voltage-time pairs (V1, t1), (V2, t2), (V3, t3), (V4, t4), (V4, t5), (V3, t6), (V2, t7), and (V1, t8) in the sampled data are subsequently used to fit and restore the pulse waveform. The energy information of the pulse signal is obtained based on the integration of the restored pulse waveform. The time information and energy information of the pulse signal are then used to screen for matching events. Based on the response line LOR of the screened matching event and the time information of the pulse signal, the position information of a single gamma photon event can be determined. It can be seen that the accuracy of the time data affects the screening of matching events and the accuracy of the position information of a single event, that is, the accuracy of the annihilation position.

[0070] In this application example, the shell source is placed at the center of the FOV, and sampling is performed using the MVT method. The acquisition time is more than 10 minutes to obtain the sampling data.

[0071] In one embodiment, step S110 may specifically include:

[0072] S111: Acquire all coincident events and the line of response (LOR) corresponding to each coincident event based on the sampling data.

[0073] In the embodiment of the present application, a coincidence event is two single events corresponding to two pulse signals whose time difference (i.e., the difference in the time information of the two pulse signals) is within the coincidence time window and whose energy information is within the coincidence energy window. Specifically, taking the detection of gamma rays using a PET detector as an example, two gamma photons produced by an annihilation reaction are detected by the scintillation crystals of the two detectors. The time information difference of the two gamma photons is within a preset coincidence time window, and the energy information of the two gamma photons is both within the preset coincidence energy window. In this case, the event of detecting these two gamma photons can be called a coincidence event. The coincidence time window and coincidence energy window in the embodiment of the present application can be determined based on prior information.

[0074] In some embodiments, after acquiring sampled data, all coincident events and the corresponding lines of response (LORs) for each coincident event can be obtained based on the sampled data. Specifically, the sampled data can be transmitted to a host computer, where the pulse waveform can be restored by fitting the sampled data. The restored pulse waveform can then be integrated to obtain energy information of the pulse signal corresponding to a single event. Simultaneously, the host computer can also determine the scintillation crystal numbering information of the detection module, i.e., the IP number of the scintillation crystal (e.g., the scintillation crystals are numbered 1-n), and the time information of the pulse signal based on the time data of the pulse signal.

[0075] In this embodiment, a coincidence time window and a coincidence energy window are preset in a coincidence module of a host computer. Based on the time and energy information of the pulse signal acquired based on the sampled data, a coincidence event is detected for a single event corresponding to the pulse signal. A recording module is also provided in the host computer to record the time difference between the coincidence events and the IP numbers of the two scintillation crystals. The line connecting the centers of the two scintillation crystal surfaces is the line of response (LOR) corresponding to the coincidence event.

[0076] In one example, the coincidence time window is set to 4 ns in the coincidence module of the host computer, and the coincidence time window is 420 keV-1000 keV. If the annihilation reaction produces two gamma photons γ1 and γ2, the host computer knows based on the sampled data that the time information of the pulse signal corresponding to the single event γ1 detected by the scintillation crystal G with IP number 6 (taking the PET detection module including 48 scintillation crystals as an example) is t1, and the time information of the pulse signal corresponding to the single event γ2 detected by the scintillation crystal H with IP number 30 is t1', then the time difference is Δt= t1-t1', if △t≤4ns, the time difference between the two single events is within the coincidence time window; the pulse waveforms of the two single events are fitted and restored on the host computer, and the energy information e1 of the γ1 single event and the energy information e2 of the γ2 single event are obtained by integration respectively. If e1 and e2 are both within the range of 420-1000keV, the energy information of the two single events is within the coincidence time window. At this time, the γ1 single event and the γ2 single event are a pair of coincidence events, and the line connecting the centers of the G and H surfaces of the scintillation crystal is the response line LOR corresponding to the coincidence event. GH The recording module of the host computer records the time difference of the coincidence event as Δt=t1-t1', the IP number information of the scintillation crystals G and H as 6 and 30, and the corresponding response line LOR, which is the line connecting the centers of the GH surfaces.

[0077] Similarly, in the embodiment of the present application, all matching events, ie, corresponding response lines LORs, can be obtained based on the sampling data received by the host computer.

[0078] In one embodiment of the present application, if there are multiple pairs of matching events corresponding to the same response line LOR, the number of matching events on the response line LOR and the time difference of each matching event on the response line LOR are counted. For example, continuing with the above example, if there are 20 pairs of matching events corresponding to the response line LOR GH , then the statistical response line LOR GH The event difference information Δt1-Δt20 of the corresponding 20 pairs of matching events is recorded in the recording module, and the number of matching events 20, the time difference Δt1-Δt20 of each matching event, the IP number information 6, 30 of the scintillation crystals G and H, and the corresponding response line LOR, which is the line connecting the centers of the GH surfaces, are recorded in the recording module.

[0079] In the example of this application, the host computer obtains the time information and energy information of all pulse signals based on the sampling data, and screens out all matching events based on the preset matching time window and matching energy window, and records the time difference of all matching events, the IP number information of the scintillation crystal and the response line LOR corresponding to all matching events, so as to facilitate the subsequent screening of all response line LORs passing through the shell source (such as a simulated radiation source, etc.) and all matching events corresponding to each response line LOR.

[0080] S112: Filter all response lines LORi passing through the shell source and the matching events Ki on each response line LORi.

[0081] In an embodiment of the present application, the coincident events obtained in step S111 may include true events, random events, and scattered events. Random events and scattered events will affect the accuracy of the time correction value obtained subsequently and need to be discarded. It will be understood by those skilled in the art that the response lines LOR corresponding to the true events in the coincident events all pass through the shell source, that is, they have an intersection with the shell source, while the random events and scattered events do not pass through the shell source, that is, they have no intersection with the shell source. Therefore, in an example of the present application, the coincident events corresponding to the true events can be screened by whether the response line LOR corresponding to the coincident event passes through the shell source.

[0082] In the embodiment of the present application, screening all response lines LORi passing through the shell source and the matching events Ki on each response line LORi can be achieved by determining whether the straight line where the response line LOR is located intersects the shell source. Specifically, the following steps can be included:

[0083] Based on the prior information, the intersection judgment module is used to determine whether the line where the response line LOR is located intersects with the shell source.

[0084] In one embodiment of the present application, the prior information may include the IP number of the scintillation crystals spaced between the scintillation crystals of the detection modules at both ends of the response line LOR. The IP number of the spaced scintillation crystals is determined based on whether the shell source intersects the straight line where each response line LOR is located.

[0085] In one example of the present application, prior information can be obtained based on different shell sources. For both regular and irregular shell sources, the number of scintillation crystal IPs between the IP numbers of the scintillation crystals at each end of the corresponding LOR (line of response) at its intersection with the shell source can be pre-counted. This information can be used as prior information, and a prior information lookup table can be created for easy reference.

[0086] In one example, regarding the acquisition of prior information for a regularly shaped shell source, assuming a shell source with a diameter of 500 mm, and assuming a PET detector comprising 48 scintillator crystals, it was determined based on prior information that if the IPs of the two scintillator crystals corresponding to the ends of a line of response (LOR) are separated by 12 scintillator crystal IPs, the line of response (LOR) between the two crystals passes through the center of the shell source and is 0 mm from the center of the shell source. If the two crystals are separated by 9 crystal IPs, then the line connecting the midpoints of the two crystal surfaces is 180 mm from the center of the shell source, and the line of response (LOR) between the two crystals passes through the shell source. If the two crystals are separated by 6 crystal IPs, then the line connecting the midpoints of the two crystal surfaces is 250 mm from the center of the shell source, and the line of response (LOR) between the two crystals is tangent to the shell source. If the number of scintillator crystal IPs between the two scintillator crystals corresponding to the ends of a line of response (LOR) is less than 6, then the line of response (LOR) does not pass through the shell source. At this time, the prior information obtained based on the shell source is: if the number of IPs of the scintillation crystals between the scintillation crystals at both ends of the response line LOR is greater than or equal to 6, then the response line LOR passes through the shell source.

[0087] In one embodiment of the present application, in order to obtain the prior information of the irregular shell source, it is necessary to gradually count whether there are intersections between the shell source and the straight line where each response line LOR is located. MN When the number of scintillation crystal IPs between the two corresponding scintillation crystals M and N is greater than or equal to 5, the response line LOR MN There is an intersection with the shell source. On the contrary, when the number of IPs of the scintillation crystals is less than 5, the response line LOR MN No intersection with the shell source; response line LOR SR When the number of scintillation crystal IPs between the two corresponding scintillation crystals S and R is greater than or equal to 8, the response line LOR SR There is an intersection with the shell source. On the contrary, when the number of IPs of the scintillation crystals is less than 8, the response line LOR SR There is no intersection with the shell source; ..., similarly, when the response line LOR formed between two of the 48 scintillation crystals intersects with the shell source, the critical values ​​of the IP numbers of the scintillation crystals corresponding to the two ends of each response line LOR are counted one by one, and recorded and saved to form a priori information lookup table, so as to facilitate the subsequent judgment of whether the response line LOR intersects with the shell source based on the response line LOR corresponding to the event and the priori information, thereby judging whether the response line LOR that meets the event passes through the shell source.

[0088] In an embodiment of the present application, after obtaining prior information, an intersection determination module determines whether the line on which the response line LOR (Line of Response) intersects with the shell source based on the prior information. In one example, the obtained prior information (if the number of scintillation crystal IPs between the scintillation crystals corresponding to the two ends of the response line LOR is greater than or equal to 6, then the response line LOR passes through the shell source, i.e., the shell source) is consulted. If the IPs of the two scintillation crystals corresponding to the two ends of a response line LOR are separated by 5 scintillation crystal IPs, then the line on which the response line LOR is located does not pass through the shell source, and all consistent events on the response line LOR are scattered events or random events and are discarded. Conversely, if the IPs of the two scintillation crystals corresponding to the two ends of a response line LOR are separated by 7 scintillation crystal IPs, then the line on which the response line LOR is located passes through the shell source, and all consistent events on the response line LOR are true events.

[0089] In an embodiment of the present application, based on the sampling data, the coincident event Ki (i ≥ 1) obtained on the response line LORi (i ≥ 1) passing through the shell source is a true coincident event, and the coincident event Ki contains coincident event information. The coincident event information specifically includes but is not limited to the number of coincident events on each response line LOR, the time difference Δt between each coincident event, the numbering information of the scintillation crystals corresponding to the two ends of the response line LOR, the corresponding response line LOR, that is, the line connecting the center points of the surfaces of the two scintillation crystals, and the IP number of the scintillation crystals between the two scintillation crystals.

[0090] In some embodiments, after obtaining the response lines LORi (i≥1) passing through the shell source and the coincident events Ki (i≥1) on each response line LORi based on the sampled data, the following steps are further included:

[0091] The filtered response lines LOR and their corresponding matching event information are recorded in the recording module.

[0092] In one example, the recording module records the selected LORs and their corresponding coincident event information, including but not limited to the number of coincident events on each LOR, the time difference Δt between each coincident event, the serial numbers of the scintillation crystals corresponding to both ends of the LOR, the line connecting the centers of the surfaces of the two scintillation crystals corresponding to the LOR, and the IP serial numbers of the scintillation crystals between the two scintillation crystals. Recording in the recording module facilitates easy access and facilitates subsequent reconstruction of activity images.

[0093] Step S120: Acquire an activity image based on all coincident events of all response lines LORi passing through the shell source.

[0094] In some embodiments, after obtaining coincident events passing through the shell source in step S110, an activity image can be obtained based on all coincident events along all lines of response LORi passing through the shell source. In one example, step 120 includes reconstructing the activity image using filtered back projection or an iterative method based on all coincident events along all lines of response LORi passing through the shell source. Filtered back projection (FBP) or iterative methods can be specifically described in the prior art and are not further described here.

[0095] The pixel value of each pixel point in the activity image obtained in the embodiment of the present application is the activity value. The pixel value is linearly proportional to the number of coincident events (assuming that the linear coefficient is k, the k value is determined by the specific type of PET detector used, and the proportional relationship between the pixel value of the activity image and the number of coincident events is determined by the type of PET detector used), which can be used to characterize the number of coincident events.

[0096] Step S130: Based on all the response lines LORi passing through the shell source, the response lines LORj (j≥1) whose number of events meets a preset condition are screened.

[0097] Those skilled in the art will appreciate that if the number of coincident events corresponding to a line of response (LOR) is too small, the coincident events on that line of response (LOR) can generally be considered scattered events or random events. For example, if there is only one pair of coincident events on a line of response (LOR), the coincident events on that line of response (LOR) can be considered scattered events or random events. To further improve the accuracy of time correction, further screening of true events is required. Certain criteria can be set to screen true events among the coincident events to discard scattered events or random events.

[0098] In the embodiment of the present application, after obtaining all response lines LORi passing through the shell source, the response lines LORj (j≥1) whose number of events meets the preset conditions can be screened. In a specific example, step S130 specifically includes:

[0099] Step S131: Setting a benchmark value for event quantity comparison.

[0100] In the embodiments of the present application, the reference value for comparing the number of matching events can be set based on a priori information or specific needs. For example, the reference value for the number of matching events used for comparison can be set to 20. If the number of matching events corresponding to each response line LOR is large, the reference value can be set larger; otherwise, the reference value can be set smaller.

[0101] Step S132: Determine whether the number of matching events is greater than a reference value.

[0102] In the embodiment of the present application, the number of corresponding matching events on each response line LOR is compared with the benchmark value. If the number of corresponding matching events on a response line LOR is greater than the benchmark value, it meets the requirements, and the response line LOR is retained and recorded; otherwise, the response line LOR is discarded.

[0103] Step S133: storing the response line LOR corresponding to the number of events being greater than the reference value.

[0104] In the embodiment of the present application, the response line LOR that meets the requirements determined in step S132 is stored in the storage module.

[0105] The embodiment shown in the figure of the present application screens the response lines LORj (j≥1) whose number of events meets the preset conditions based on all the response lines LORi passing through the shell source, further discards random events and scattered events among the events that meet the conditions, and screens out as many true events as possible for subsequent acquisition of time correction values, thereby improving the accuracy of the acquired time correction values, that is, improving the effect of time correction.

[0106] Step S140: obtaining pixel points Pj where each selected response line LORj intersects with the activity image, and obtaining pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel points Pj.

[0107] In one example, step S140 specifically includes:

[0108] Step S141: obtaining pixel points Pj where each selected response line LORj intersects with the activity image.

[0109] In the embodiment of the present application, after acquiring the activity image, the pixel points Pj where each response line LORj passing through the shell source intersects with the activity image can be obtained. For example, the pixel points Pj where each selected response line LORj intersects with the activity image can be obtained using a ray tracing method. The specific operation of the ray tracing method can be referred to in the prior art and will not be described in detail here.

[0110] Step S142: obtaining pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel point Pj.

[0111] In the embodiment of the present application, step S142 specifically includes:

[0112] Step S1421: Calculate the time difference from the pixel point Pj to the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj;

[0113] Step S1422: determining a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculating the accumulated pixel values ​​of the pixel points Pj whose time differences fall within each time difference interval;

[0114] Step S1423: Using the time difference interval as the horizontal axis step and the pixel value accumulation value of the pixel points falling within each step as the vertical axis, obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

[0115] Step S150: Obtain the statistical distribution Mj of the event-time difference corresponding to each selected response line LORj.

[0116] In one example, step S150 specifically includes:

[0117] The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Tj, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mj corresponding to each response line LORj is obtained.

[0118] In the embodiment of the present application, the horizontal axis step size of the event-time difference statistical distribution Mj corresponding to each response line LORj and its corresponding pixel value-time difference statistical distribution Tj is the same, and the horizontal axis setting range is also the same, that is, the horizontal axis settings of Tj and Mj are exactly the same, so as to facilitate the subsequent calculation of the maximum value Yj of the inner product of each Tj and the corresponding Mj.

[0119] Step S160: Determine the corresponding peak numbers of Tj and Mj.

[0120] In one example, determining the number of corresponding peaks of Tj and Mj includes counting the number of corresponding peaks of Tj and Mj, and transmitting the statistical result to the matching module for matching.

[0121] In the embodiments of the present application, the peak values ​​of Tj and Mj obtained based on the shell source generally have one or two peaks, and accordingly, the number of corresponding peaks of Tj and Mj is one or two. When the response line LORj is tangential to the shell source, the number of corresponding peaks of Tj and Mj is one. When the response line LORj intersects the shell source, the number of corresponding peaks of Tj and Mj is two.

[0122] Step S170: Based on the number of corresponding peaks of Tj and Mj, a method matching the number of corresponding peaks is selected to obtain the time correction value of the detection module.

[0123] In some embodiments, step S170 may include:

[0124] Step S171: Based on the number of corresponding peaks of the received Tj and Mj, the time deviation difference δ corresponding to each response line LORi is matched and calculated. △ j.

[0125] In one example, the matching calculation in step S171 may include:

[0126] If the number of corresponding peaks of Tj and Mj is one, the time difference mean Ej of all the events on the response line LORj is calculated to obtain the time deviation difference δ corresponding to the response line LORj. △ j;

[0127] If the number of corresponding peaks of Tj and Mj is two, the inner product of Tj and Mj is calculated to obtain the time deviation difference δ corresponding to the maximum value Yj of the inner product of Tj and Mj. △ j.

[0128] In some embodiments, calculating the mean time difference Ej of all coincident events on the line of response LORj includes:

[0129] The number of coincident events on the response line LORj is counted, and the summed mean of the time differences of the coincident events is calculated to obtain the mean time difference Ej of all coincident events on the response line LORj.

[0130] In one example of this application, the number of corresponding peaks for Tj and Mj is one, indicating that the response line LORj is tangential to the shell source. Annihilation events typically occur at the intersection, and the mean time difference of the coincident events resulting from annihilation at the intersection forms a peak. The shell source is placed at the center of the PET detection ring. Data is collected for a period of time, such as more than 10 minutes, to obtain coincident event information for the response line LOR that passes through the shell source. For a given response line LORj, the surface centers of the scintillation crystals cj and dj of the corresponding PET detection rings at its ends are connected. The average time difference of all the matching events on the response line LORj is denoted as Ej, and the difference in time deviations cj and dj of the scintillation crystals cj and dj at both ends of the response line LORj is taken as the difference. Then (tcj+δcj)-(tdj+δdj)=Ej. Theoretically, since the shell source is set at the center of the PET detection ring, the time difference between the two ends of a response line LORj is 0, so tcj-tdj=0, and δcj-δdj=Ej is obtained, that is, the difference in time deviations of the scintillation crystals at both ends of the response line LORj is equal to the average time difference Ej of all the matching events on the response line LORj. For example, the scintillation crystals corresponding to the two ends of response line LOR1 are c1 and d1. Statistics show that there are 10 coincident events on response line LOR1, with time differences of t1, t2, ..., t10, respectively. The time differences of these 10 coincident events on response line LOR1 are summed and averaged to obtain E1. The difference in the time deviations δc1 and δd1 between the scintillation crystals c1 and d1 at the two ends of response line LOR1 is E1, i.e., δc1 - δd1 = E1. Similarly, E2 - Ej for response line LOR2 - response line LORj can be obtained, i.e., δc2 - δd2 = E2, ..., δcj - δdj = Ej. The above equations can be combined to form a system of equations. By solving this linear system, the time deviations δcj and δdj of each scintillation crystal can be obtained.

[0131] In some embodiments, the maximum value Yj of the inner product of Tj and Mj is calculated to obtain the time deviation difference δ corresponding to the maximum value Yj of the inner product of each Tj and Mj. △ j, including:

[0132] Taking Tj as the reference, translate Mj, calculate the inner product of Tj and Mj, and obtain the maximum value Yj of the inner product of Tj and Mj by counting the translation amount of Mj, which is δ △ j.

[0133] In one embodiment, when the number of corresponding peaks of Tj and Mj is two, as shown in FIG. Figure 3As shown in Figure 1, for a given response line LORj, there are two intersections with the crust source, and annihilation events usually occur at these intersections. The mean of the time differences of the events consistent with annihilation at one intersection forms a peak, while the mean of the time differences of the events consistent with annihilation at the other intersection forms another peak.

[0134] like Figure 3 Assuming that the distance between the two intersection points of the response line LORj and the shell source is L, and the speed of light is C, for an annihilation event at one of the points, let the theoretical detection time be tcj1 and tdj1, and the mean of the time difference of the annihilation position that matches the event be Ej1, which is the difference in the time deviation (time deviation) δcj, δdj of the scintillation crystals cj and dj at both ends of the response line LORj, then

[0135] Tcj1+δcj-(tdj1+δdj)=Ej1,

[0136] Tcj1-tdj1=-L / c.

[0137] For an annihilation event at another point, let the theoretical detection time be tcj2 and tdj2, and the mean of the time difference of the annihilation position that matches the event be Ej2, which is the difference of the time deviations cj and dj of the scintillation crystals cj and dj of the detection modules at both ends of the response line LORj. Then

[0138] tcj2+δcj-(tdj2+δdj)=Ej2,

[0139] tcj2-tdj2=L / c.

[0140] Then tcj1+δcj-(tdj1+δdj)+tcj2+δcj-(tdj2+δdj)=Ej1+Ej2,

[0141] get

[0142] δcj–δdj=(Ej1+Ej2) / 2=δ △ j.

[0143] It can be seen from the above formula that when the response line LOR intersects the shell source at at least two intersection points, and the mean of the time difference of the corresponding coincident events at the corresponding intersection points forms two peaks, the mean of the time difference of the coincident events of each peak can be obtained respectively and then added and averaged to obtain the difference of the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of the response line LORj. Then, the values ​​of δcj and δdj can be obtained by solving the system of simultaneous equations and linear equations. However, when the shell source is not uniform, the two peaks may intersect. At this time, it will be impossible to accurately distinguish the annihilation location corresponding to each coincident event on each response line LOR. Therefore, the number of coincident events corresponding to each peak cannot be directly obtained, and the mean of the time difference of the coincident events of each peak cannot be known, and it is also impossible to obtain (Ej1+Ej2) / 2, and accordingly, the difference δcj–δdj cannot be obtained. △ j, δcj and δdj cannot be obtained.

[0144] In the embodiment of the present application, when there are two corresponding peaks of Tj and Mj, the time deviation difference δ of the scintillation crystals corresponding to the two ends of the response line LORj is directly obtained by obtaining the translation amount of Mj relative to Tj when the inner product of Tj and Mj reaches the maximum value Yj. △ j, specifically, with Tj as the reference, translate Mj, calculate the inner product of Tj and Mj, and statistically obtain the maximum value Yj of the inner product of Tj and Mj when the translation amount of Mj is δ Δ j. Specifically, assuming that the response line LORj between the two scintillator crystals cj and dj of the PET detection ring corresponds to Tj and Mj, the inner product of Tj and Mj is specifically the value obtained by multiplying and adding the values ​​of the ordinates corresponding to the same abscissas of Tj and Mj. From steps S140 to S150, it can be seen that the abscissas of Tj and Mj are set to be exactly the same, and the value of the ordinate corresponding to the abscissa of Tj is the cumulative value of the pixel values ​​corresponding to the time difference interval represented by the abscissa, and the value of the ordinate corresponding to the abscissa of Mj is the cumulative value of the coincident events corresponding to the time difference interval represented by the abscissa. That is, the inner product of Tj and Mj is specifically the value obtained by multiplying and adding the cumulative value of the pixel values ​​corresponding to each abscissa of Tj and the cumulative value of the coincident events of Tj.

[0145] It should be understood by those skilled in the art that, assuming that the scintillation crystals corresponding to the two ends of the response line LORj are cj and dj, the time deviations of the scintillation crystals cj and dj are represented by δcj and δdj respectively, and the difference between δcj and δdj is represented by δ △ j, that is, δcj-δdj=δ △ j, the time difference Ej of the event on the response line LORj is characterized by:

[0146] t cj +δcj-(tdj +δdj)=Ej,

[0147] Among them, t cj , t dj The time data in the sampling data corresponding to the scintillation crystals cj and dj received by the host computer can be sorted out as follows:

[0148] t cj -t dj +(δcj-δdj)=Ej,

[0149] When δcj=δdj, we can get:

[0150] t cj -t dj =Ej.

[0151] From the above formula, we can see that δcj=δdj, that is, δcj-δdj=δ △ When j = 0, the time difference of the coincident events on the response line LORj is independent of δcj and δdj, and is only related to the location of the annihilation event. The time difference between the two single events corresponding to two gamma photons generated at different annihilation locations on the response line LORj is different, while the time difference between the two single events corresponding to two gamma photons generated at different times but at the same annihilation location is the same. When the response line LORj corresponds to multiple coincident events, the number of coincident events corresponding to the same time difference is fixed. Accordingly, the fluctuations of the ordinates corresponding to the same abscissas of Mj and Tj are consistent, the peaks of Mj and Tj must correspond, and the value Yj obtained by multiplying and adding the two is also necessarily the largest.

[0152] That is, when the inner product value of Mj and Tj corresponding to a certain response line LORj is the largest, the peak values ​​of Mj and Tj correspond, and the time deviations δcj and δdj of the two scintillation crystals cj and dj corresponding to the two ends of the response line LORj satisfy δcj-δdj=δ △ j=0.

[0153] On the contrary, if the inner product value of Mj and Tj corresponding to a certain response line LORj does not reach the maximum value Yj, then the peak values ​​of Mj and Tj do not correspond, δcj-δdj=δ △ j, and δ △ j is not 0.

[0154] If the inner product value of Mj and Tj corresponding to a certain response line LORj does not reach the maximum value Yj (the peak values ​​of Mj and Tj do not correspond at this time), it is determined by δcj-δdj=δ △ j, and δ △If the inner product value of Mj and Tj corresponding to the response line LORj reaches the maximum Yj (at this time, the peak values ​​of Mj and Tj correspond), the time deviations δcj and δdj of the two scintillation crystals cj and dj at both ends of the response line LORj satisfy δcj-δdj=δ △ Therefore, Mj and Tj can be relatively moved so that the inner product value of Mj and Tj reaches the maximum value Yj from the non-maximum value. At this time, the offset of the relative movement of Mj and Tj is the difference δcj and δdj δ △ j, at this time, the time deviations δcj and δdj of the two scintillation crystals cj and dj corresponding to the two ends of the response line LORj satisfy δcj-δdj=δ △ j.

[0155] In the embodiment of the present application, assuming that the response lines LORj of the two scintillation crystals cj and dj at the two ends correspond to Mj and Tj, Mj can be moved with Tj as the comparison reference. Specifically, the relative movement can be achieved by the following operations:

[0156] First, we determine δ by prior information. △ j range, such as obtaining the response line LORj by long-term sampling and fitting, δcj-δdj=δ △ j, to obtain δ △ The range of j, for example, δ △ The range of j is [-5,5]ns.

[0157] Secondly, t represents the horizontal axis of Tj (the horizontal axis step size is the time difference interval range), and c represents the horizontal axis of Tj. T Characterize the vertical coordinate value of Tj (accumulated pixel value), that is, Tj(t,c T ), t represents the horizontal coordinate of Mj (the horizontal coordinate step is the time difference interval range), c M Characterize the vertical coordinate value of Mj (according to the event accumulation value), that is, Mj(t,c M ), Mi(t,c M ) and Ti(t,c T ) are set to the same range of the horizontal axis t, and are all set to be larger than the δ obtained based on the prior information △ Set Mj(t,c M ) translation step, each time Mj(t,c M ) translate by a step size δ M , after moving n times, it corresponds to Mj(t+n*δ M ,c M ), the same horizontal coordinate corresponding to the moved Mj(t+n*δ M ,c M ) and Tj(t,c T) and add the vertical coordinates to get <M(t+n*δ M ,c M ),T(t,c T )>n*δ when the inner product reaches its maximum value Yj M value, at this time Mj(t+n*δ M ,c M ) and Tj(t,c T )>The peak value corresponds to the maximum, Mj and Tj change from peak non-correspondence to peak correspondence, and the translation n*δ M That is, the difference δ between the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of the response line LORj corresponding to Mj and Tj △ j, that is, δcj-δdj=δ △ j=n*δ M .

[0158] Step S172: Based on the δ △ j. Get the time correction value of the detection module.

[0159] In the embodiment of the present application, δ is obtained △ After j, we can △ j obtains the time correction value of the detection module. In one example, based on the δ △ j Obtain the time correction value of the detection module, specifically including:

[0160] Step S1721: Based on the δ △ j, and obtain the relationship between the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each response line LORj. δcj-δdj=δ △ j;

[0161] Step S1722: A set of simultaneous equations is used to obtain the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each response line LORj by a fitting method, where δcj and δdj are time correction values.

[0162] In the embodiment of the present application, after obtaining the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each response line LORj, i.e., the time correction values, the following steps may be further included:

[0163] Step S180: Based on the acquired time correction value, time correction is performed on the sampling data acquired by the detection module.

[0164] In a specific example of the present application, the time data corresponding to the scintillation crystals cj and dj of the detection module in the sampled data is corrected, including: subtracting the time correction values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillation crystals cj and dj of the detection module in the sampled data, respectively.

[0165] The solution of the embodiment of the present application obtains the pixel value-time difference statistical distribution Tj corresponding to each response line LORj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj, determines the corresponding peak number of Tj and Mj, and obtains the situation of the mean corresponding peak of the time difference of the coincidence event generated by the annihilation of the intersection position, that is, the intersection or tangency of the response line LOR and the shell source is obtained, and based on the number of corresponding peaks of Tj and Mj, the matching control module selects a method that matches the corresponding peak number to obtain the time correction value of the detection module, avoiding the use of Gaussian fitting for time correction, improving the efficiency of time correction based on the shell source, and improving operational safety.

[0166] The embodiment of the present application obtains the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj based on the true coincidence events filtered through the shell source, and calculates the maximum value Yj of the inner product of each Tj and Mj to obtain the difference δ between each response line LORji and the time deviation corresponding to the maximum value. △ j, then based on the δ △ j obtains the time correction value, which is applicable to any shell source, has wide applicability, and does not require Gaussian fitting, so long sampling is not required, which saves time and improves time correction efficiency. It also does not require the use of highly active drugs, which improves operational safety. In addition, since the embodiment of the present application is based on the true coincidence events corresponding to the response lines LORj that pass through the shell source and the number of coincidence events that meet the preset conditions, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj are obtained, random events and scattered events are further discarded, and the difference δ of the time deviation corresponding to each response line LORj obtained is further improved accordingly. Δ j, thereby further improving the accuracy of time correction.

[0167] The embodiment shown in the figure of the present application screens the response lines LORj (j≥1) whose number of events meets the preset conditions based on all the response lines LORi passing through the shell source of the target object, further discards random events and scattered events among the matching events, and screens out as many true events as possible for subsequent acquisition of time correction values, thereby improving the accuracy of the acquired time correction values, that is, improving the effect of time correction.

[0168] Figure 4This is an exemplary module diagram of a shell source-based time correction device according to some embodiments of the present application.

[0169] like Figure 4 As shown, the time correction device may include:

[0170] The first event-matching screening module 203, the activity image reconstruction module 204, the second event-matching screening module 205, the pixel value-time difference statistical distribution acquisition module 206, the event-time difference statistical distribution acquisition module 207, the statistics module 208, the matching module 209, the calculation module 210, and the time correction value acquisition module 211.

[0171] In some embodiments, the first coincident event screening module 203 is configured to obtain response lines LORi (i≥1) passing through the shell source and coincident events Ki (i≥1) on each response line LORi based on the sampled data.

[0172] In one example, the first coincident event screening module 203 includes an intersection determination module, which is configured to determine whether the line along which the line of response (LOR) intersects with the shell source and, based on the number of intersections, determine whether the line of response (LOR) passes through the shell source. Specifically, the intersection determination module can determine whether the line along which the line of response (LOR) intersects with the shell source based on prior information. In one specific example, the prior information includes the number of scintillation crystal IPs separating the scintillation crystals of the detection modules at both ends of the line of response (LOR). The number of scintillation crystal IPs separating the scintillation crystals is determined based on whether the inner diameter of the shell source in each direction intersects the line along which the line of response (LOR) intersects.

[0173] In some embodiments, the activity image reconstruction module 204 is configured to acquire an activity image based on all coincident events of all lines of response LORi passing through the shell source. In one example, the activity image reconstruction module acquires the activity image based on all coincident events of all lines of response LORi passing through the shell source by reconstructing the activity image using filtered back projection or an iterative method.

[0174] In some embodiments, the second coincident event screening module 205 is configured to screen response lines LORj (j≥1) whose number of coincident events meets a preset reference value based on all response lines LORi (i≥1) passing through the shell source.

[0175] In one example, the second matching event screening module 205 includes: a reference value setting module for setting a reference value for comparing the number of matching events; a determination module for determining whether the number of matching events is greater than the reference value; and a storage module for storing a response line LOR indicating whether the number of matching events is greater than the reference value.

[0176] In some embodiments, the pixel value-time difference statistical distribution acquisition module 206 is configured to obtain each pixel point Pj where each screened response line LORj intersects with the activity image, and obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel point Pj.

[0177] In one example, the pixel value-time difference statistical distribution acquisition module 206 includes a pixel point acquisition module and a time difference statistical distribution acquisition module. The pixel point acquisition module is used to obtain the pixel point Pj where the filtered response line LORj intersects with the activity image based on a ray tracing method; the time difference statistical distribution acquisition module is used to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel point Pj.

[0178] 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 Tj acquisition module. The pixel point time difference acquisition module is used to calculate the time difference from the pixel point Pj to the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj; the pixel value accumulation module is used to determine a number of equally spaced time difference intervals, and based on the time difference of each pixel point Pj, calculate the cumulative value of the pixel value of the pixel point Pj whose time difference falls into each time difference interval; the pixel value-time difference statistical distribution Tj acquisition module is used to use the time difference interval as the horizontal axis step size and the cumulative value of the pixel value of the pixel points falling into each step size as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

[0179] In some embodiments, the coincidence event-time difference statistical distribution acquisition module 207 is configured to acquire the coincidence event-time difference statistical distribution Mj corresponding to each response line LORi.

[0180] In a specific example, in order to obtain the event-time difference statistical distribution Mj corresponding to each response line LORj, the event-time difference statistical distribution acquisition module 207 is configured as: the horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Tj as the step size, and the vertical axis is determined by the cumulative value of the event whose time difference falls into each step size, so as to obtain the event-time difference statistical distribution Mj corresponding to each response line LORi.

[0181] In some embodiments, the statistics module 208 is configured to count the number of corresponding peaks of Tj and Mj. In one example, the number of corresponding peaks of Tj and Mj counted by the statistics module 208 is one or two. In the embodiments of the present application, the peaks of Tj and Mj obtained based on the shell source generally have one or two peaks, and accordingly, the number of corresponding peaks of Tj and Mj is one or two. When the response line LORj is tangent to the shell source, the number of corresponding peaks of Tj and Mj is one. When the response line LORj intersects the shell source, the number of corresponding peaks of Tj and Mj is two. The number of corresponding peaks of Tj and Mj is statistically recorded in the statistics module.

[0182] In some embodiments, the matching module 209 is in communication with the statistical module and is configured to control the calculation module to calculate the time deviation difference corresponding to each response line LORj in a matching manner based on the corresponding peak number of Tj and Mj. △ In one example, the matching module controls the calculation module to calculate the time deviation difference δ corresponding to each response line LORj based on the corresponding peak number of Tj and Mj. △ j, including:

[0183] If the number of corresponding peaks of Tj and Mj is one, the calculation module calculates the mean Ej of the time differences of all events on the response line LORj to obtain the difference of the time deviation corresponding to the response line LORj. △ j; if the number of corresponding peaks of Tj and Mj is two, the calculation module calculates the inner product of Tj and Mj to obtain the time deviation difference corresponding to the maximum value Yj of the inner product of each Tj and Mj △ j.

[0184] In one embodiment of the present application, the calculation module 210 calculates the mean time difference Ej of all matching events on the response line LORj, including: counting the number of matching events on the response line LORj, and calculating the summed mean of the time differences of the matching events to obtain the mean time difference Ej of all matching events on the response line LORj. For details, refer to the example shown in step S171 of the method embodiment shown in the figure.

[0185] In one embodiment of the present application, the calculation module 210 calculates the inner product of Tj and Mj to obtain the time deviation difference corresponding to the maximum value Yj of the inner product of each Tj and Mj. △ j, including:

[0186] Taking Tj as the reference, translate Mj, calculate the inner product of Tj and Mj, and obtain the maximum value Yj of the inner product of Tj and Mj by counting the translation amount of Mj. The translation amount is △ j. Refer specifically to the example shown in step S171 of the method embodiment shown in the figure.

[0187] In some embodiments, the calculation module 210 is configured to calculate the time deviation difference δ corresponding to each response line LORj. △ j.

[0188] In some embodiments, the time correction value acquisition module 211 is configured to be based on δ △ In one example, the time correction value is the time deviation δcj, δdj of the scintillation crystals cj, dj of the detection module at both ends of each response line LORi.

[0189] In a specific example, the time correction value acquisition module 211 includes a fitting module, which is configured to obtain the relationship between the time deviations δcj and δdj of the scintillation crystals cj and dj of the detection modules at both ends of each response line LORj based on the said δj, and the relationship δcj-δdj=δj; a group of simultaneous equations, and obtain the time correction values ​​of the scintillation crystals cj and dj of the detection modules at both ends of each response line LORj through a fitting method.

[0190] In some embodiments, the calculation module and the time correction value acquisition module can be implemented by the same device.

[0191] In some embodiments, the shell source-based time correction device may further include a coincidence module for acquiring all coincident events and the corresponding lines of response (LORs) for each coincident event based on sampled data. In one example, the sampled data may include the scintillation crystal number information of the detection module and the time information of the pulse signal; the coincidence module includes a pulse signal energy information acquisition module for acquiring the energy information of the pulse signal based on the sampled data, acquiring coincident events based on the time information and energy information of the pulse signal, and acquiring the corresponding lines of response (LORs) for the coincident events based on the scintillation crystal number information.

[0192] In some embodiments, the shell source-based time correction device may further include a recording module for recording the time difference of a coincidence event and the corresponding scintillation crystal number information of the detection modules at both ends of the line of response LOR.

[0193] In some embodiments, the shell source-based time correction device further includes a correction module, the sampling data includes the scintillation crystal number information of the detection module and the time information of the pulse signal, and the correction module is used to correct the pulse signal time information in the sampling data based on the time correction value.

[0194] In one example, the correction module corrects the pulse signal time information in the sampled data based on the time correction value, and corrects the time data corresponding to the scintillation crystals cj and dj of the detection module in the sampled data, including: subtracting the time correction values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillation crystals cj and dj of the detection module in the sampled data, respectively.

[0195] The shell source-based time correction device in the embodiment of the present application can be combined with the features of the shell source-based time correction method in the embodiment of the present application, and vice versa.

[0196] The solution of the embodiment of the present application obtains the pixel value-time difference statistical distribution Tj corresponding to each response line LORj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj, determines the corresponding peak number of Tj and Mj, and obtains the situation of the mean corresponding peak of the time difference of the coincidence event generated by the annihilation of the intersection position, that is, the intersection or tangency of the response line LOR and the shell source is obtained, and based on the number of corresponding peaks of Tj and Mj, the matching control module selects a method that matches the corresponding peak number to obtain the time correction value of the detection module, avoiding the use of Gaussian fitting for time correction, improving the efficiency of time correction based on the shell source, and does not require the use of high-activity drugs, thereby improving operational safety.

[0197] The embodiment of the present application obtains the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj based on the true coincidence events filtered through the shell source, and calculates the maximum value Yj of the inner product of each Tj and Mj to obtain the difference δ between each response line LORji and the time deviation corresponding to the maximum value. △ j, then based on the δ △ j obtains the time correction value, and does not require Gaussian fitting, so long sampling is not required, which saves time and improves the efficiency of time correction. In addition, since the embodiment of the present application is based on the true coincidence events corresponding to the response lines LORj that pass through the shell source and the number of coincidence events that meet the preset conditions, the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj corresponding to each response line LORj are obtained, random events and scattered events are further discarded, and the difference δ of the time deviation corresponding to each response line LORj obtained is further improved accordingly. △ j, thereby further improving the accuracy of time correction.

[0198] This embodiment sets up a second coincident event screening module, which screens the response lines LORj (j≥1) whose number of coincident events meets a preset condition based on all the response lines LORi passing through the shell source, further discards random events and scattered events among the coincident events, and screens out as many true events as possible for subsequent acquisition of time correction values, thereby improving the accuracy of the acquired time correction values, that is, improving the effect of time correction.

[0199] In some embodiments, the present application also provides a digitizing device, which may include the time correction device, detection module, and sampling module mentioned in the above embodiments. The digitizing device can be used to correct the pulse signal data acquired based on the target object to improve the correction efficiency, correction effect, and correction safety. The digitizing device uses the detection module to detect the object to be detected, uses the sampling module to acquire sampling data, and corrects the sampling data based on the time correction value to acquire corrected time data. Based on the acquired coincident events and the corrected time data, a digitized image is formed. In a specific example, the digitizing device is a positron emission tomography (PET).

[0200] In some embodiments, the detection module is configured to obtain a pulse signal based on a shell source. Specific target signals can be referred to the method embodiment and will not be described in detail here.

[0201] In one example, the detection module includes a detector, which includes a scintillation crystal and a photoelectric conversion element. The scintillation crystal is used to convert gamma rays into visible light, and the photoelectric conversion element is used to convert the visible light into a pulse signal.

[0202] In some embodiments, the sampling module is configured to sample the pulse signal to obtain sampled data. Specific details of the sampled data can be found in the method embodiments and will not be described in detail here.

[0203] In one example, the sampling module is a multi-voltage threshold sampling module, which includes a threshold setting module, a comparison module, a time-to-digital conversion module, and an information storage module, wherein the threshold setting module is used to set the sampling threshold; the comparison module is used to compare the pulse signal with the threshold and output a jump signal; the time-to-digital conversion module is used to perform time sampling on the jump signal to obtain the time information of the pulse signal; the information storage module stores the scintillation crystal number information of the detection module and the time information of the pulse signal.

[0204] In the embodiment of the present application, the digitization device can directly obtain the annihilation position based on the corrected time data and coincident events, thereby directly forming a digitized image (such as a PET image), without the need for complex image reconstruction methods, thereby simplifying image reconstruction.

[0205] In some embodiments, the present application also provides a computer device, comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the method described in any embodiment of the present application.

[0206] Although not shown, in some embodiments, a computer-readable storage medium is further provided, storing a computer program configured to execute the steps of any of the methods of the embodiments of the present application when executed. The computer program includes various program modules / units that constitute the apparatus according to the embodiments of the present application. When the computer program composed of the various program modules / units is executed, it can implement the functions corresponding to the various steps in the methods described in the above embodiments. The computer program can also be executed on the electronic device described in the embodiments of the present application.

[0207] While the basic concepts have been described herein, it will be apparent to those skilled in the art that the detailed disclosure is merely illustrative and does not limit the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and amendments to the present application. Such modifications, improvements, and amendments are suggested in the present application and remain within the spirit and scope of the exemplary embodiments of the present application.

[0208] At the same time, this application uses specific terms to describe the embodiments of this application. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment," "an embodiment," or "an alternative embodiment" mentioned twice or multiple times in different locations in this application does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0209] In addition, it will be understood by those skilled in the art that various aspects of the present application can be illustrated and described by a number of patentable categories or situations, including any new and useful process, machine, product or combination of substances, or any new and useful improvements thereto. Accordingly, various aspects of the present application can be performed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may all be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". In addition, various aspects of the present application may be manifested as a computer product located in one or more computer-readable media, which includes computer-readable program code.

[0210] A computer storage medium may include a propagated data signal embodying the computer program code, for example, in baseband or as part of a carrier wave. The propagated signal may be in a variety of forms, including electromagnetic, optical, or any suitable combination thereof. A computer storage medium may be any computer-readable medium other than a computer-readable storage medium that can be connected to an instruction execution system, apparatus, or device to communicate, propagate, or transfer the program for use. The program code on the computer storage medium may be transmitted via any suitable medium, including radio, cable, fiber optic cable, RF, or similar media, or any combination of these.

[0211] The computer program code required for the operation of each part of the present application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python, etc., conventional procedural programming languages ​​such as C language, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, dynamic programming languages ​​such as Python, Ruby and Groovy, or other programming languages. The program code can be run entirely on the user's computer, or as a separate software package on the user's computer, or partly on the user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any network form, such as a local area network (LAN) or a wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as software as a service (SaaS).

[0212] In addition, unless expressly stated in the claims, the order of the processing elements and sequences described in this application, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this application. Although the above disclosure discusses some of the invention embodiments currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this application. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only by software solutions, such as installing the described system on an existing server or mobile device.

[0213] Similarly, it should be noted that, in order to simplify the presentation of this application and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this application sometimes combine multiple features into a single embodiment, figure, or description thereof. However, this disclosure method does not mean that the subject matter of this application requires more features than those recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single embodiment disclosed above.

[0214] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0215] Each patent, patent application, patent application disclosure, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this application is hereby incorporated by reference in its entirety. This includes application history documents that are inconsistent with or conflict with the content of this application, as well as documents (currently or subsequently attached to this application) that limit the broadest scope of the claims of this application. It should be noted that if the descriptions, definitions, and / or use of terms in the accompanying materials of this application are inconsistent or conflicting with the content of this application, the descriptions, definitions, and / or use of terms in this application shall prevail.

[0216] Finally, it should be understood that the embodiments described in this application are merely illustrative of the principles of the embodiments of this application. Other variations may also fall within the scope of this application. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this application may be considered consistent with the teachings of this application. Accordingly, the embodiments of this application are not limited to the embodiments explicitly introduced and described in this application.

Claims

1. A time correction method based on shell source, characterized in that: include: Based on the sampling data, the response lines LORi passing through the shell source and the coincident events Ki on each response line LORi are obtained, where i represents the number, i ≥ 1, and the time difference between the corresponding coincident events at both ends of each response line LORi and the coincident events on each response line LORi is recorded; Acquire activity images based on all coincident events of all response lines LORi passing through the shell source; Based on all response lines LORi passing through the shell source, the response lines LORj whose number of events meets the preset conditions are screened, where j represents the number, j ≥ 1; Obtain the pixel points Pj where each selected response line LORj intersects with the activity image, and obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel points Pj; Obtain the statistical distribution Mj of the event-time difference corresponding to each selected response line LORj; Determine the number of corresponding peaks of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj; Based on the number of corresponding peaks, a method matching the number of corresponding peaks is selected to obtain the time correction value.

2. The time correction method according to claim 1, wherein: Select the method that matches the number of corresponding peaks to obtain the time correction value, including: Based on the received pixel value-time difference statistical distribution Tj and the number of corresponding peaks that match the event-time difference statistical distribution Mj, the time deviation difference δ corresponding to each response line LORj is calculated by matching △ j; Based on the difference δ △ j, obtain the time correction value.

3. The time correction method according to claim 2, characterized in that: The number of corresponding peaks of the pixel value-time difference statistical distribution Tj and the coincidence event-time difference statistical distribution Mj is one or two.

4. The time correction method according to claim 3, characterized in that: The time deviation difference δ corresponding to each response line LORj is calculated by matching △ j, including: If the number of corresponding peaks is one, the time difference mean Ej of all matching events on the response line LORj is calculated to obtain the time deviation difference δ corresponding to the response line LORj. △ j; If the number of corresponding peaks is two, the maximum value Yj of the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj is calculated to obtain the time deviation difference δ corresponding to the maximum value Yj △ j.

5. The time correction method according to claim 4, characterized in that: Calculate the mean time difference Ej of all events on the response line LORj, including: The number of coincident events on the response line LORj is counted, and the summed mean of the time differences of the coincident events is calculated to obtain the mean time difference Ej of all coincident events on the response line LORj.

6. The time correction method according to claim 4, characterized in that: Get the time deviation difference δ corresponding to the maximum value Yj △ j, including: Taking the pixel value-time difference statistical distribution Tj as the benchmark, translate the event-time difference statistical distribution Mj, calculate the inner product Yj of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj, and obtain the translation amount that meets the event-time difference statistical distribution Mj when the inner product is the maximum value Yj. The translation amount is the difference δ △ j.

7. The time correction method according to claim 2, characterized in that: Based on the difference δ △ j. Get the time correction value, including: Based on the difference δ △ j, and the relationship between the time deviations δcj and δdj of the scintillator crystals cj and dj at both ends of each response line LORj is obtained. δcj-δdj=δ △ j; The simultaneous equations are fitted to obtain the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj, where δcj and δdj are time correction values.

8. The time correction method according to claim 7, characterized in that: The time correction method further includes: performing time correction on the sampled data acquired by the detection module based on the acquired time correction value, that is, correcting the time data corresponding to the scintillation crystals cj and dj in the sampled data based on the time deviations δcj and δdj of the scintillation crystals cj and dj.

9. The time correction method according to claim 8, characterized in that: Correcting the time data corresponding to the scintillation crystals cj and dj in the sampled data includes: subtracting the time correction values ​​δcj and δdj from the time data tcj and tdj corresponding to the scintillation crystals cj and dj in the sampled data, respectively.

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

11. The time correction method according to claim 1, wherein: Based on the sampling data, the response lines LORi passing through the shell source and the coincident events Ki on each response line LORi are obtained, including: Obtain all coincident events and the corresponding LORs of each coincident event based on the sampling data; Filter all response lines LORi passing through the shell source and the matching events Ki on each response line LORi.

12. The time correction method according to claim 11, characterized in that: Filter all response lines LORi passing through the shell source and the matching events Ki on each response line LORi, including: Based on prior information, it is determined whether the line where the response line LOR lies intersects with the shell source.

13. The time correction method according to claim 12, characterized in that: The prior information includes the number of IPs of the scintillation crystals spaced between the scintillation crystals at both ends of the line of response (LOR). The number of IPs of the spaced scintillation crystals is determined based on whether the inner diameter of the shell source in each direction intersects the line where the line of response (LOR) is located.

14. The time correction method according to claim 1, wherein: Based on all coincident events of all response lines LORi passing through the shell source, activity images are obtained, including: Based on all coincident events of all response lines LORi passing through the shell source, the activity image is reconstructed using filtered back projection or iterative methods.

15. The time correction method according to claim 1, wherein: Based on all the response lines LORi passing through the shell source, the response lines LORj whose event numbers meet the preset conditions are screened, including: Setting a benchmark value for comparison of the number of events; Determine whether the number of matching events is greater than the benchmark value; The response line LOR corresponding to the number of events greater than the reference value is stored.

16. The time correction method according to claim 1, wherein: Obtain the pixel point Pj where each selected response line LORj intersects with the activity image, including: The pixel points Pj where each selected response line LORj intersects with the activity image are obtained based on the ray tracing method.

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

18. The time correction method according to claim 1, wherein: Obtain the statistical distribution Mj of the event-time difference corresponding to each selected response line LORj, including: The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Tj, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mj corresponding to each response line LORj is obtained.

19. A time correction device based on a shell source, characterized in that: include: A first coincidence event screening module is configured to obtain, based on the sampling data, response lines LORi passing through the shell source and coincidence events Ki on each response line LORi, where i represents the number, i≥1; an activity image reconstruction module configured to acquire an activity image based on all coincident events of all response lines LORi passing through the shell source; The second coincidence event screening module is configured to screen the response lines LORj whose number of coincidence events meets a preset reference value based on all the response lines LORi passing through the shell source, wherein j represents the number, j≥1; A pixel value-time difference statistical distribution acquisition module is configured to acquire each pixel point Pj where each selected response line LORj intersects with the activity image, and acquire the pixel value-time difference statistical distribution Tj corresponding to each response line LORj based on the pixel point Pj; A coincidence event-time difference statistical distribution acquisition module is configured to acquire a coincidence event-time difference statistical distribution Mj corresponding to each screened response line LORj; A statistics module configured to count the number of corresponding peaks of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj; A matching module is configured to match the time deviation difference δ corresponding to each response line LORj based on the corresponding peak number. △ How j is calculated; The calculation module is configured to calculate the time deviation difference δ corresponding to each response line LORj according to the matching calculation method. △ j; The time correction value acquisition module is configured to obtain the time correction value based on the δ △ jGet the time correction value.

20. The time correction device according to claim 19, characterized in that The number of corresponding peaks of the pixel value-time difference statistical distribution Tj counted by the statistical module and the event-time difference statistical distribution Mj is one or two.

21. The time correction device according to claim 20, characterized in that The time difference δ corresponding to each response line LORj is selected △ j matching calculation method, the matching module is further configured as follows: If the number of corresponding peaks is one, the calculation module calculates the mean time difference Ej of all events on the response line LORj to obtain the time deviation difference δ corresponding to the response line LORj. △ j; If the number of corresponding peaks is two, the calculation module calculates the inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj to obtain the time deviation difference δ corresponding to the maximum value Yj of the inner product △ j.

22. The time correction device according to claim 21, characterized in that To calculate the mean time difference Ej of all coincident events on the line of response LORj, the calculation module is further configured as follows: The number of coincident events on the response line LORj is counted, and the summed mean of the time differences of the coincident events is calculated to obtain the mean time difference Ej of all coincident events on the response line LORj.

23. The time correction device according to claim 21, characterized in that To obtain the time deviation difference δ corresponding to the maximum value Yj of the inner product △ j, the calculation module is further configured to: Taking the pixel value-time difference statistical distribution Tj as the benchmark, the event-time difference statistical distribution Mj is translated. The inner product of the pixel value-time difference statistical distribution Tj and the event-time difference statistical distribution Mj is calculated. When the inner product reaches the maximum value Yj, the translation amount of the event-time difference statistical distribution Mj is calculated. The translation amount is δ △ j.

24. The time correction device according to claim 19, characterized in that The sampling data includes scintillation crystal number information and pulse signal time information; The coincidence event screening module is further configured to obtain energy information of the pulse signal based on the sampled data, obtain coincidence events based on time information and energy information of the pulse signal, and obtain the line of response (LOR) corresponding to the coincidence event based on the scintillation crystal number information.

25. The time correction device according to claim 19, characterized in that The time correction device also includes: The recording module is configured to record the time difference of the event and the corresponding scintillation crystal number information of the detection modules at both ends of the response line LOR.

26. The time correction device according to claim 19, characterized in that The first coincidence event screening module is further configured to determine whether the line on which the response line LOR is located has an intersection with the shell source based on prior information, and determine whether the response line LOR passes through the shell source based on the number of intersections.

27. The time correction device according to claim 26, characterized in that The prior information includes the number of IPs of the scintillation crystals spaced between the scintillation crystals of the detection modules at both ends of the line of response (LOR). The number of IPs of the spaced scintillation crystals is determined based on whether the inner diameter of the shell source in each direction intersects the line where the line of response (LOR) is located.

28. The time correction device according to claim 19, characterized in that The activity image reconstruction module is configured to reconstruct the activity image using filtered back projection or an iterative method.

29. The time correction device according to claim 19, characterized in that The second matching event screening module includes: A benchmark value setting module is used to set a benchmark value for comparing the number of events; A determination module, used to determine whether the number of matching events is greater than a reference value; The storage module is used to store the response line LOR indicating whether the number of coincidence events is greater than a reference value.

30. The time correction device according to claim 19, characterized in that The pixel value-time difference statistical distribution acquisition module is configured to acquire the pixel point Pj where the selected response line LORj intersects the activity image based on a ray tracing method.

31. The time correction device according to claim 30, characterized in that The pixel value-time difference statistical distribution acquisition module includes: The pixel time difference acquisition module is used to calculate the time difference between the pixel point Pj and the two end points of the corresponding response line LORj one by one, and record the pixel value of each pixel point Pj; A pixel value accumulation module is used to determine a number of equally spaced time difference intervals and, based on the time difference of each pixel point Pj, calculate the accumulated values ​​of the pixel values ​​of the pixel points Pj whose time differences fall within each time difference interval; The pixel value-time difference statistical distribution acquisition module is configured to use the time difference interval as the horizontal axis step and the cumulative value of the pixel values ​​of the pixel points falling within each step as the vertical axis to obtain the pixel value-time difference statistical distribution Tj corresponding to each response line LORj.

32. The time correction device according to claim 19, characterized in that In order to obtain the statistical distribution Mi of the coincident event-time difference corresponding to each response line LORi, the statistical distribution acquisition module of the coincident event-time difference is further configured as follows: The horizontal axis is determined by the horizontal axis step size of the pixel value-time difference statistical distribution Tj, and the vertical axis is determined by the cumulative value of the coincident events whose time difference falls into each step size, and the coincident event-time difference statistical distribution Mj corresponding to each response line LORj is obtained.

33. The time correction device according to claim 32, characterized in that The time correction value acquisition module is further configured to: △ j obtains the relationship between the time deviations δcj and δdj of the scintillation crystals cj and dj at both ends of each response line LORj, δcj-δdj=δj; the simultaneous equations are used to obtain the time correction values ​​of the scintillation crystals cj and dj at both ends of each response line LORj by fitting method.

34. The time correction device according to claim 19, characterized in that The time correction device further comprises a correction module, which is configured to correct the time information of the pulse signal in the sampled data based on the time correction value: the time data t corresponding to the scintillation crystals cj and dj in the sampled data cj , t dj Subtract the time correction values ​​δcj and δdj respectively.

35. A digitizing device, characterized in that: include: According to the shell source-based time correction device as described in any one of claims 19 to 34, the digitizing device uses a detector to detect the object to be detected, uses a sampling module to obtain sampling data, uses the time correction device to correct the sampling data and obtain the corrected time data, thereby forming a digitized image based on the corrected time data.

36. A computer device, characterized in that include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the steps of the time correction method according to any one of claims 1 to 18 are implemented.

37. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the time correction method according to any one of claims 1 to 18 are implemented.

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