Time correction method and system for inter-crystal scattering events of siPM-based pet detectors

Abstract

The application provides a time correction method and system for inter-crystal scattering events of a PET detector based on SiPM, and the application instantiates multiple time-to-digital converters in a field programmable logic gate array device, performs pulse width measurement on the electrical signals output by each SiPM detector, since the pulse width is positively correlated with the energy of the signal, the non-inter-crystal scattering events and the inter-crystal scattering events can be determined by the pulse width, and the position of the inter-crystal scattering events is determined to reduce the position selection error. During the correction, firstly, the non-inter-crystal scattering events are generally corrected, then further, the time difference between the inter-crystal scattering events occurring in each crystal and the non-inter-crystal scattering events on the response line is counted offline, the additional time difference of each inter-crystal scattering event caused by the time walk effect is obtained, and then the inter-crystal scattering events are secondarily corrected in time online, so that the time resolution of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of medical imaging equipment technology, and in particular to a time correction method and system for intercrystalline scattering events in a SiPM-based PET detector. Background Technology

[0002] Positron emission tomography (PET) is a nuclear medicine imaging system primarily composed of a detector system, electronics system, data acquisition system, and reconstruction system. The detector system consists of a scintillation crystal, a photoelectric conversion device, and front-end electronics. Currently, silicon photomultiplier tube (SiPM)-based detectors are increasingly used in PET systems due to their excellent energy and temporal resolution and magnetic compatibility. Its main working principle involves using the SiPM to convert high-energy gamma photons captured by the scintillation crystal into low-energy visible light, which is then converted into an analog electrical signal via the photoelectric effect. This analog signal is amplified and shaped using analog conditioning circuitry before being sent to energy, time, and position measurement devices to obtain the energy, time, and position information. Finally, coincidence selection and other methods are used at the back end to filter out the valid signals.

[0003] Currently, time-of-flight (TOF) PET (positron emission tomography) detectors based on yttrium lutetium silicate scintillation (LYSO) crystals and SiPM (Silicon photomultiplier) are among the most important devices for early cancer detection.

[0004] The principle is to use SiPM to convert the high-energy Gamma photons captured by the crystal module into visible light signals, which are then converted into analog electrical signals through the photoelectric effect. The analog electrical signals are then amplified and shaped using an analog conditioning circuit. The energy and arrival time of the analog electrical signals are obtained using an energy measurement device and a time measurement device. Finally, valid data is obtained through methods such as coincidence selection.

[0005] The data contains energy information of gamma photons, positional information of the reacting crystal, and temporal information. This information allows for the reconstruction of the location and shape of the gamma radiation source. A backend reconstruction system then obtains the location of the radionuclide reaction, thereby reconstructing a cancer image.

[0006] Because the reaction sites of Gamma photons in different crystals, the propagation paths of visible light in crystals, the responses of electrical signals generated by different SiPMs, and the electronic delays of different channels all exhibit discreteness, back-end correction is generally required to align the time delays of events hitting different crystals. A typical time correction scheme involves statistically analyzing the time delays of events hitting different crystals to obtain a set of correction coefficients, which are then used in a back-end digital processor for correction.

[0007] However, in many cases, gamma photons undergo inter-crystal scattering (ICS) in crystals, meaning that some gamma photons are scattered by electrons in one crystal into adjacent crystals, where visible light is generated again. This results in two crystals generating signals simultaneously.

[0008] In this situation, the first problem is that crystal position determination is prone to error. Secondly, because the two scattered signals are relatively small, there will be an additional time delay compared to the non-scattered signal (non-ICS) due to the time walk effect. If the usual time correction scheme is still used, the time correction error for ICS events will be large, thus affecting the system's coincidence time resolution (CTR).

[0009] Existing techniques randomly select the location of ICS events, leading to significant judgment errors. By statistically analyzing the time delays of events hitting different crystals, a set of correction coefficients is obtained, which are then used for online correction in a digital processor. However, this method does not perform special processing on ICS events. Because the two ICS signals are relatively small, compared to non-scattering signals, an additional time delay occurs due to the time walk effect, resulting in inaccurate time correction of ICS events. Summary of the Invention

[0010] To overcome the above-mentioned technical defects, the purpose of this invention is to provide a time correction method and system for intercrystalline scattering events of a SiPM-based PET detector that further corrects the time of intercrystalline scattering events based on a general time correction scheme.

[0011] This invention discloses a time correction method for intercrystalline scattering events in a SiPM-based PET detector, comprising: in differential signal mode, comparing all row and column signals of the SiPM detector array with a fixed voltage threshold to obtain a time overthreshold pulse; measuring the leading and trailing edges of the time overthreshold pulse using a clock-phase-based time-to-digital converter to obtain the time overthreshold pulse width; determining whether the event in the crystal of the SiPM detector is an amorphous intercrystalline scattering event or an intercrystalline scattering event based on the time overthreshold pulse width; calculating the time difference between the amorphous intercrystalline scattering event in each crystal and the amorphous intercrystalline scattering event on the response line, and obtaining a first time correction lookup table through multiple iterations; calculating the time difference between the intercrystalline scattering event in each crystal and the amorphous intercrystalline scattering event on the response line, and obtaining a second time correction lookup table through multiple iterations; the addresses of the first and second time correction lookup tables are the crystal encoding positions, and the contents are time difference information; saving the first and second time correction lookup tables, and using the first and second time correction lookup tables to perform real-time online correction of the time of the intercrystalline scattering events.

[0012] Preferably, determining whether an event in the crystal of the SiPM detector is an intercrystalline scattering event or an intercrystalline scattering event based on the time overthreshold pulse width includes: for an intercrystalline scattering event, determining the unique encoding information of the crystal hitting position; for an intercrystalline scattering event, using the crystal encoding corresponding to the time overthreshold pulse width greater than a preset threshold from the time overthreshold pulse width information of all signals as the crystal hitting position encoding information.

[0013] Preferably, the real-time online correction of the time of the intercrystalline scattering event using the first time correction lookup table and the second time correction lookup table includes: for an intercrystalline scattering event, based on the determined position encoding information of the struck crystal and the intercrystalline scattering flag, firstly, the content corresponding to the address in the first time correction lookup table is searched to obtain the time difference information corresponding to the position encoding information, and the time measurement result is corrected based on the time difference information; then, the content corresponding to the address in the second time correction lookup table is searched to obtain the time difference information corresponding to the position encoding information, and the time measurement result is corrected a second time based on the time difference information.

[0014] Preferably, the real-time online correction of the time of the intercrystalline scattering event using the first time correction lookup table and the second time correction lookup table includes: for non-intercrystalline scattering events, based on the determined position encoding information of the struck crystal, searching for the content corresponding to the address in the first time correction lookup table, thereby obtaining the time difference information corresponding to the position encoding information, and correcting the time measurement result based on the time difference information.

[0015] Preferably, the method further includes: summing the signals of the SiPM detector array, measuring the summed signals using a high-speed comparator and a carry-chain-based time-to-digital converter to obtain the arrival time of the signals received by the SiPM detector array; and performing time correction on the arrival time based on the time difference information.

[0016] Preferably, it further includes: summing the rows and columns of the SiPM detector array through a resistor network, increasing the number of position readout circuit channels from n 2 The number of SiPM detector units is reduced to 2n, and the position of the excited SiPM detector unit is determined by judging the trigger position of the row and column summation signal.

[0017] Preferably, the SiPM detector array is coupled to the LYSO crystal in a 1:1 ratio.

[0018] Preferably, the method further includes: summing the signals of the SiPM detector array, converting the analog signals into digital signals through an analog-to-digital converter, and then integrating the digital signals to obtain the number of ADC channels characterizing the energy of the analog signals.

[0019] The present invention also discloses a time correction system for intercrystalline scattering events of a SiPM-based PET detector, including a time measurement module, a position pulse width measurement and calculation module disposed in a field-programmable gate array, an offline time correction table generation module, and an online time correction module;

[0020] The position pulse width measurement and calculation module includes a comparator unit, a position pulse width measurement unit, and a position calculation unit. In differential signal mode, the comparator unit compares all row and column signals of the SiPM detector array with a fixed voltage threshold to obtain a time-over-threshold pulse. The position pulse width measurement unit measures the leading and trailing edges of the time-over-threshold pulse using a clock-phase-based time-to-digital converter to obtain the time-over-threshold pulse width. The position calculation unit uses the time-over-threshold pulse width to determine whether the event in the SiPM detector's crystal is an inter-crystal scattering event or an inter-crystal scattering event. For inter-crystal scattering events, it determines a unique encoding information for the crystal-hitting location. For inter-crystal scattering events, it uses the crystal encoding corresponding to the time-over-threshold pulse width greater than a preset threshold from all the signals' time-over-threshold pulse width information as the crystal-hitting location encoding information.

[0021] The offline time correction table generation module calculates the time difference between the intercrystalline scattering events in each crystal and the intercrystalline scattering events on the response line, and obtains a first time correction lookup table through multiple iterations; it also calculates the time difference between the intercrystalline scattering events in each crystal and the intercrystalline scattering events on the response line, and obtains a second time correction lookup table through multiple iterations; the addresses of the first time correction lookup table and the second time correction lookup table are the crystal encoding positions, and the contents are time difference information;

[0022] The time measurement module sums the signals from the SiPM detector array and measures the summed signals using a high-speed comparator and a carry-chain-based time-to-digital converter to obtain the arrival time of the signals received by the SiPM detector array.

[0023] The online time correction module stores the first time correction lookup table and the second time correction lookup table in random access memory; and performs real-time online correction on the arrival time obtained by the time measurement module using the first time correction lookup table and the second time correction lookup table.

[0024] Preferably, it also includes a front-end position encoding circuit and an energy measurement module; the front-end position encoding circuit adds the SiPM detector array row by row and column by column through a resistor network, increasing the number of position readout circuit channels from n 2 The number of SiPM detector units is reduced to 2n, and the position of the excited SiPM detector unit is determined by judging the trigger position of the row and column summation signal; the energy measurement module sums the signals of the SiPM detector array, converts the analog signal into a digital signal through an analog-to-digital converter, and then integrates the digital signal to obtain the number of ADC channels that characterizes the energy of the analog signal.

[0025] Compared with existing technologies, the above technical solution has the following advantages:

[0026] 1. This invention instantiates multiple time-to-digital converters in a field-programmable gate array (FPGA) device and measures the pulse width of the electrical signal output by each SiPM detector. Since the pulse width is positively correlated with the energy of the signal, the pulse width can be used to determine the intercrystalline scattering events and the location of the intercrystalline scattering events, thereby reducing location selection errors.

[0027] 2. In the correction section, a general correction is first performed on the intercrystalline scattering events. Then, the time difference between the intercrystalline scattering events occurring in each crystal and the intercrystalline scattering events on the response line is statistically analyzed offline to obtain the additional time difference caused by the time travel effect for each intercrystalline scattering event. Then, a second time correction is performed online on the intercrystalline scattering events to improve the time resolution of the system. Attached Figure Description

[0028] Figure 1 A schematic diagram of a preferred embodiment of the time correction system for intercrystalline scattering events of a SiPM-based PET detector provided by the present invention;

[0029] Figure 2 A schematic diagram illustrating the time delay difference between intercrystalline scattering events and amorphous scattering events;

[0030] Figure 3 The test results before and after time spectrum correction of intercrystalline scattering events are provided by the present invention;

[0031] Figure 4 The test results of the time spectrum of intercrystalline scattering events and amorphous scattering events provided by this invention are before time spectrum correction.

[0032] Figure 5 The time spectrum correction test results for intercrystalline scattering events and amorphous scattering events provided by this invention. Detailed Implementation

[0033] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0035] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0036] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0037] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0039] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0040] This invention discloses a time correction method for intercrystalline scattering events in a SiPM-based PET detector. The method involves instantiating multiple time-to-digital converters in a field-programmable gate array (FPGA) and measuring the pulse width of the electrical signal output from each SiPM detector. Since pulse width is positively correlated with signal energy, non-intercrystalline scattering events and intercrystalline scattering events can be distinguished by the pulse width, and the location of intercrystalline scattering events can be determined to reduce location selection errors. In the correction section, a general correction is first performed on non-intercrystalline scattering events. Then, offline, the time difference between intercrystalline scattering events occurring in each crystal and non-intercrystalline scattering events on the response line is statistically analyzed to obtain the additional time difference caused by the time travel effect for each intercrystalline scattering event. Finally, a secondary time correction is performed online on the intercrystalline scattering events to improve the system's time resolution.

[0041] Specifically, the process first distinguishes between amorphous intercrystalline scattering events and intercrystalline scattering events. In differential signal mode, all row and column signals of the SiPM detector array are compared with a fixed voltage threshold to obtain the time-over-threshold (TOT) pulse. Then, the leading and trailing edges of the TOT pulse are measured using a clock-phased time-to-digital converter (multi-phase TDC) to obtain the TOT pulse width. Since the pulse width is positively correlated with the signal energy, the TOT pulse width is then used to determine whether the event in the SiPM detector's crystal is an amorphous or intercrystalline scattering event.

[0042] Next, time correction is performed, specifically through a time correction lookup table. The time correction lookup table is obtained as follows: The time difference between the intercrystalline scattering events in each crystal and the intercrystalline scattering events on the response line is calculated, and a first time correction lookup table is obtained through multiple iterations; the time difference between the intercrystalline scattering events in each crystal and the intercrystalline scattering events on the response line is calculated, and a second time correction lookup table is obtained through multiple iterations. The addresses of the first and second time correction lookup tables are the crystal encoding positions, and the content is the time difference information. The addresses and content are in a one-to-one correspondence; each address corresponds to a specific time difference. The first and second time correction lookup tables are saved. In subsequent correction stages, based on the first and second time correction lookup tables, the time difference information corresponding to the crystal encoding position can be determined by knowing the crystal encoding position, and correction is performed accordingly.

[0043] The time correction is based on time measurement. Specifically, the signals of the SiPM detector array are summed, and the summed signals are measured by a high-speed comparator and a carry-chain FPGA-TDC to obtain the arrival time of the signal received by the SiPM detector array. Combined with the time difference information obtained above, the arrival time can be corrected.

[0044] Ideally, the position of the detector array should be known beforehand. Specifically, the SiPM detector array is summed row by row and column by column using a resistor network, and the number of channels for the position readout circuit is increased from n. 2 The number of detectors is reduced to 2n, and the position of the excited SiPM detector element is determined by judging the trigger position of the row and column summation signal. This SiPM detector array is coupled to the LYSO crystal in a 1:1 ratio.

[0045] Next, the signals from the SiPM detector array are summed, and the analog signals are converted into digital signals by an analog-to-digital converter. Then, the digital signals are integrated to obtain the number of ADC channels that characterize the energy of the analog signals.

[0046] See appendix Figure 1-2 The present invention also discloses a time correction system for intercrystalline scattering events of a SiPM-based PET detector, including a front-end position encoding circuit, an energy measurement module, a time measurement module, a position pulse width measurement and calculation module located in a field programmable gate array (FPGA), an offline time correction table generation module, and an online time correction module.

[0047] 1) The front-end position encoding circuit first sums the rows and columns of the SiPM detector array through a resistor network, increasing the number of channels in the position readout circuit from n. 2 The number of SiPM detector units is reduced to 2n, and the position of the excited SiPM detector unit is determined by judging the trigger position of the row and column summation signal.

[0048] 2) The energy measurement module is used to sum the signals of the SiPM detector array, convert the analog signals into digital signals through a medium-to-high-speed analog-to-digital converter (ADC), and then integrate the digital signals to obtain the number of ADC channels used to characterize the energy of the analog signals.

[0049] 3) The time measurement module is used to measure the signal arrival time, and subsequent time corrections are based on the time obtained by this module. Specifically, the signals from the SiPM detector array are summed, and the summed signals are measured using a high-speed comparator and a carry-chain-based time-to-digital converter to obtain the arrival time of the signal received by the SiPM detector array.

[0050] 4) Next, the position pulse width measurement and calculation module determines whether the event in the crystal of the SiPM detector is an amorphous intercrystalline scattering event or an intercrystalline scattering event. The position pulse width measurement and calculation module includes a comparator unit, a position pulse width measurement unit, and a position calculation unit.

[0051] 4.1) First, the comparator unit utilizes the IBUF resources within the FPGA to configure a differential signal LVDS mode, comparing all (2n) rows and columns of the SiPM detector array with a fixed voltage threshold to obtain the time-over-threshold (TOT) pulse. The width of the TOT pulse can be used to characterize the energy of the input signal.

[0052] 4.2) Next, the position pulse width measurement unit uses a clock-phased time-to-digital converter (multi-phase TDC) inside the FPGA to measure the timing of the leading and trailing edges of the time-over-threshold TOT pulse, thereby obtaining the time-over-threshold TOT pulse width.

[0053] 4.3) Finally, since pulse width is positively correlated with signal energy, the position calculation unit uses the information from (2n) time-cross-threshold pulse widths to determine whether the event in the SiPM detector's crystal is an amorphous intercrystalline scattering event or an intercrystalline scattering event. Furthermore: for amorphous intercrystalline scattering events, a unique crystal-hitting location encoding is determined; for intercrystalline scattering events, the crystal encoding corresponding to time-cross-threshold pulse widths greater than a preset threshold (i.e., relatively large) from all signal time-cross-threshold pulse width information is used as the crystal-hitting location encoding information. This preset threshold can be selected according to requirements and is not limited to a maximum or controlled within a specific range.

[0054] 5) Next, two time correction lookup tables are obtained through the offline time correction table generation module. The offline time correction table generation module can include two offline time correction table generation units: a first offline time correction table generation unit for correcting amorphous intercrystalline scattering events, and a second offline time correction table generation unit for correcting intercrystalline scattering events. The principle is as follows... Figure 2 As shown, for a non-intercrystalline scattering event (gamma event), its energy (approximately 511 keV) is deposited entirely within a single crystal. However, for intercrystalline scattering events, the energy is deposited in both crystals. Since the time measurement section measures the time of the signal that first crosses the threshold, due to the time-walking effect, the threshold crossing time of intercrystalline scattering events will have a time delay difference compared to non-intercrystalline scattering events. The intercrystalline scattering event time correction table generated by the second offline time correction table generation unit is used to store this time delay difference for further correction.

[0055] 5.1) The first offline time correction table (intercrystalline scattering event time correction table) is generated by the unit that calculates the time difference between the intercrystalline scattering event in each crystal and the intercrystalline scattering event on the response line, and obtains the first time correction lookup table LUT1 through multiple iterations.

[0056] 5.2) The second offline time correction table (intercrystalline scattering event time correction table) is generated by the unit that calculates the time difference between intercrystalline scattering events and non-intercrystalline scattering events on the response line for each crystal, and obtains the second time correction lookup table LUT2 through multiple iterations.

[0057] The addresses of the first and second time correction lookup tables are crystal encoding positions, and the contents are time difference information. The addresses and contents correspond one-to-one. It can be understood that each address corresponds to a time difference information.

[0058] 6) The online time correction module stores a first time correction lookup table and a second time correction lookup table in random access memory (RAM). Specifically, the first time correction lookup table is stored in RAM1, and the second time correction lookup table is stored in RAM2. Based on these two tables, the module performs real-time online correction of the arrival time obtained by the time measurement module.

[0059] 6.1) For amorphous intercrystalline scattering events, based on the determined position encoding information of the struck crystal, the content corresponding to the address is searched through the address in the first time correction lookup table to obtain the time difference information corresponding to the position encoding information, and the time measurement results are corrected based on the time difference information.

[0060] 6.2) For intercrystalline scattering events, based on the determined location encoding information of the struck crystal and the intercrystalline scattering flag, the content corresponding to the address is first searched in the first time correction lookup table to obtain the time difference information corresponding to the location encoding information. The time measurement result is then corrected based on the time difference information. Next, the content corresponding to the address is searched in the second time correction lookup table to obtain the time difference information corresponding to the location encoding information. The time measurement result is then corrected a second time based on the time difference information. See the formula for details: Where t is the original time measurement result (i.e., the arrival time output by the time measurement module), and t' is the corrected time measurement result. Pos is the crystal position code, LUT1 is the first time correction lookup table (time correction table for non-crystal scattering events), and LUT2 is the second time correction lookup table (time correction table for intercrystal scattering events).

[0061] The solution of this invention was verified and tested on a certain type of PET scanner, and the test results are attached. Figure 3-5 As shown, for intercrystalline scattering events, the CTR can be improved by 134 ps using this scheme, while for all events in the entire system, the CTR can be improved by 46 ps, achieving good results.

[0062] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for time correction of inter-crystal scattering events of a SiPM-based PET detector, characterized in that, The method comprises the following steps: In the differential signal mode, all row and column signals of the SiPM detector array are compared with a fixed voltage threshold to obtain time threshold crossing pulses of the signals; The front and back edges of the time threshold crossing pulses are measured by a clock phase-based time-to-digital converter to obtain time threshold crossing pulse widths, and the time threshold crossing pulse widths are used to determine whether an event in a crystal of the SiPM detector is an inter-crystal scattering event or an intra-crystal scattering event; The time difference between the intra-crystal scattering events in each crystal and the intra-crystal scattering events on a response line is counted, and a first time correction lookup table is obtained through multiple iterations; The time difference between the inter-crystal scattering events in each crystal and the intra-crystal scattering events on a response line is counted, and a second time correction lookup table is obtained through multiple iterations; The addresses of the first time correction lookup table and the second time correction lookup table are crystal encoding positions, and the contents are time difference information; The first time correction lookup table and the second time correction lookup table are saved, and the time of the inter-crystal scattering events is corrected in real time and online through the first time correction lookup table and the second time correction lookup table; The determination of whether an event in a crystal of the SiPM detector is an inter-crystal scattering event or an intra-crystal scattering event through the time threshold crossing pulse widths comprises the following steps: For an intra-crystal scattering event, the encoding information of a unique hit crystal position is determined; For an inter-crystal scattering event, the crystal encoding corresponding to the time threshold crossing pulse width greater than a preset threshold in the information of the time threshold crossing pulse widths of all signals is taken as the encoding information of the hit crystal position; The real-time online correction of the time of the inter-crystal scattering events through the first time correction lookup table and the second time correction lookup table comprises the following steps: For an inter-crystal scattering event, the address of the first time correction lookup table is used to look up the content corresponding to the address to obtain the time difference information corresponding to the position encoding information, and the time measurement result is corrected based on the time difference information; then the address of the second time correction lookup table is used to look up the content corresponding to the address to obtain the time difference information corresponding to the position encoding information, and the time measurement result is corrected again based on the time difference information.

2. The method of claim 1, wherein, The real-time online correction of the time of the inter-crystal scattering events through the first time correction lookup table and the second time correction lookup table comprises the following steps: For an intra-crystal scattering event, the address of the first time correction lookup table is used to look up the content corresponding to the address to obtain the time difference information corresponding to the position encoding information of the hit crystal, and the time measurement result is corrected based on the time difference information.

3. The method of claim 1, wherein, The method further comprises the following steps: The signals of the SiPM detector array are added, and the added signals are measured by a high-speed comparator and a time-to-digital converter based on a carry chain to obtain the arrival time of the signals received by the SiPM detector array. Time correct the arrival time based on the time difference information.

4. The method of claim 1, wherein, The SiPM detector array is coupled with LYSO crystal in a 1:1 manner.

5. The method of claim 1, wherein, Further comprising: The signals of the SiPM detector array are added, the analog signals are converted into digitized signals through an analog-digital converter, then the digitized signals are integrated to obtain the ADC channel number representing the energy of the analog signals.

6. A system for time correction of inter-crystal scattering events of a SiPM-based PET detector, characterized in that, The time measurement module, the position pulse width measurement and calculation module in the field programmable logic gate array, the offline time correction table generation module and the online time correction module are included. The position pulse width measurement and calculation module includes a comparator unit, a position pulse width measurement unit and a position calculation unit; the comparator unit compares all row and column signals of the SiPM detector array with a fixed voltage threshold in a differential signal mode to obtain time threshold crossing pulses of the signals; the position pulse width measurement unit measures the time of the leading and trailing edges of the time threshold crossing pulses through a time-to-digital converter based on clock phase splitting to obtain time threshold crossing pulse widths; The position calculation unit determines whether the event in the crystal of the SiPM detector is a non-crystal-to-crystal scattering event or a crystal-to-crystal scattering event through the time threshold crossing pulse widths, and: for the non-crystal-to-crystal scattering event, determines the encoding information of the unique hit crystal position; For the crystal-to-crystal scattering event, the crystal encoding corresponding to the time threshold crossing pulse width greater than a preset threshold in the information of the time threshold crossing pulse widths of all signals is taken as the hit crystal position encoding information; The offline time correction table generation module statistics the time difference between the non-crystal-to-crystal scattering events in each crystal and the non-crystal-to-crystal scattering events on the response line, and obtains a first time correction lookup table through multiple iterations; The offline time correction table generation module statistics the time difference between the non-crystal-to-crystal scattering events in each crystal and the non-crystal-to-crystal scattering events on the response line, and obtains a first time correction lookup table through multiple iterations; The time measurement module adds the signals of the SiPM detector array, measures the added signals through a high-speed comparator and a time-to-digital converter based on a carry chain, thereby obtaining the arrival time of the signals received by the SiPM detector array; The online time correction module saves the first time correction lookup table and the second time correction lookup table through a random access memory; And corrects the arrival time obtained by the time measurement module in real time online through the first time correction lookup table and the second time correction lookup table.

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