Coincidence event screening device for all-digital PET

Abstract

The present invention provides a device for filtering coincident events for fully digital PET, comprising internal memory and video memory. The internal memory includes at least two first raw data buffers and at least two first event buffers, and the video memory includes a second raw data buffer and a second event buffer. The first raw data buffer is used to write raw data packets emitted by a detector; the second raw data buffer is used to copy raw data in the first raw data buffer and parse the raw data to generate various events; the second event buffer is used to write various generated events, perform coincidence filtering on each event, and mark the coincidence information of the event based on the coincidence filtering results; the first event buffer is used to copy the filtered coincidence events and save the coincidence events based on the coincidence information. The present invention can more accurately and directly filter coincident events for fully digital PET, more rationally, fully and efficiently utilize computing power, and significantly reduce copying time.

Description

Technical Field

[0001] The present invention belongs to the field of medical technology, and in particular relates to a coincidence event screening device for full-digital PET. Background Art

[0002] Positron emission tomography (PET) systems are advanced molecular imaging diagnostic devices in today's medical field. Because they use radionuclides as tracers, they are also known as nuclear medicine devices. PET systems are currently widely used for early-stage tumor lesion detection, assessment of chemotherapy and radiotherapy recovery, and examination of cardiovascular, cerebral, and neurological diseases, offering irreplaceable advantages in several diagnostic areas.

[0003] In principle, PET involves injecting a positron-emitting radionuclide (FDG)-labeled tracer into the patient. The tracer diffuses through the bloodstream into various tissues and participates in the body's metabolic processes. The positron-emitting radionuclide then releases a positron, which annihilates with negative electrons in the surrounding environment, generating a pair of gamma photons with equal energy but traveling in opposite directions. Gamma photons detected by the detector as originating from the same positron annihilation event are called coincident events. To improve the efficiency of PET scans, it is necessary to simultaneously collect all event data from the detector, filter these events, and save the coincident events.

[0004] In the prior art, the screening or determination of coincidence events in PET is based on traditional PET, such as the technical solutions disclosed in the Chinese invention patents entitled "A Hardware-Based Coincidence Event Determination Method" (Authorization Announcement No.: CN103336683B), "Method and Apparatus for Determining Random Coincidence Events and True Coincidence Events" (Authorization Announcement No.: CN103559391B), and "A Method and Apparatus for Determining Coincidence Events" (Authorization Announcement No.: 103413051B). These solutions use analog or analog-digital hybrid methods to process high-speed scintillation pulses, and cannot directly obtain the time information or position information of the detected photons. For example, in the technical solution disclosed in the patent entitled "A Method and Apparatus for Determining Coincidence Events", the spatial positions of the gamma photon pairs generated by the annihilation event that arrive at the detection device respectively form a coincidence line, and the length of the coincidence line is used to determine whether the position of the gamma photon pair is coincident. This makes the coincidence event determination process complex and inaccurate.

[0005] Furthermore, when the event is completed by software, if the event information that needs to be uploaded to the processing software is large, it will cause a lot of pressure on the communication link between the detection device and the computer software, and the cost of implementing the communication link will also be high. In addition, the above-mentioned event determination method needs to complete a large number of spatial conformance judgment and other processing processes in a serial manner in a short period of time. The pressure on the processing software is very high, the processing time is long, and the efficiency of conformance event determination is low. Therefore, the existing technology uses hardware-based conformance event determination. The cost of using hardware for determination is high and the hardware maintenance process is complicated, and the determination rules cannot be adjusted in real time as needed. Summary of the Invention

[0006] The object of the present invention is to provide a coincidence event screening device for full-digital PET, which can at least overcome some of the defects of the prior art.

[0007] The present invention provides a coincidence event screening device for all-digital PET, the coincidence event screening device comprising a memory and a video memory, the memory comprising at least two first raw data caches and at least two first event caches, the video memory comprising a second raw data cache and a second event cache, the first raw data cache being used to write the original data packet sent by the detector; the second raw data cache being used to copy the original data in the first raw data cache and parse the original data to generate various events; the second event cache being used to write the generated various events, and performing coincidence screening on each event, marking the coincidence information of the event according to the coincidence screening result; the first event cache being used to copy the events that have completed the coincidence screening and save the coincidence events according to the coincidence information.

[0008] According to some embodiments of the present invention, the first raw data cache adopts an event loop mechanism and a single thread to collect data packets sent by the detector.

[0009] According to some embodiments of the present invention, after one of the first raw data caches is full, the received data packet is written into the next first raw data cache, and the data in the full first raw data cache is copied to the video memory.

[0010] According to some embodiments of the present invention, the first original data cache determines a writing order of the original data according to preset numbers.

[0011] According to some embodiments of the present invention, the first original data cache determines the writing order of the original data according to a flag bit.

[0012] According to some embodiments of the present invention, the second event cache places the events into preset time periods according to the time of each event to perform time compliance screening.

[0013] According to some embodiments of the present invention, the range of each time period is no larger than the range of the time window that meets the filtering requirements.

[0014] According to some embodiments of the present invention, after performing time compliance screening, the second event cache performs location compliance judgment based on events within a time period, and marks compliance information of events with location compliance.

[0015] According to some embodiments of the present invention, the second event cache performs location conformance determination on the event based on an IP address of the event, wherein the IP address corresponds one-to-one to a crystal bar of the detector.

[0016] According to some embodiments of the present invention, the second event cache calculates the energy information of each event after performing position compliance judgment, performs energy screening on the events in turn according to the energy information of the events, and discards events that do not comply with the energy screening and events paired with events that do not comply with the energy screening.

[0017] According to some embodiments of the present invention, the first event buffer determines a writing order of data in the second event buffer according to preset numbers.

[0018] According to some embodiments of the present invention, the first event buffer determines a writing order of data in the second event buffer according to a flag bit.

[0019] The present invention provides a coincidence event screening device for all-digital PET. The device sets a raw data cache and an event cache space in the memory and the video memory respectively to store raw data and events. After the memory acquires the raw data, it copies it to the video memory, performs coincidence screening on the events in the video memory, and then stores the screened events in the memory. This fully and reasonably utilizes the storage space of the CPU and the computing power of the GPU, meeting the requirements of the high time data rate (generally around 1 to 3 Gbps) emitted by the detector during the PET engineering implementation process and the high performance requirements for software screening of coincidence events. During the entire screening process, the cache space is applied in advance, and only a data copy process occurs between the video memory and the memory. Only the initial data writing and the final data acquisition processes involve memory allocation and release processes. The entire system operates with high efficiency and speed.

[0020] The present invention provides a coincidence event screening device for all-digital PET, which applies for multiple raw data caches and multiple event caches in the memory, and applies for a single raw data cache and a single event cache in the video memory. The raw data cache of the video memory performs coincidence screening on the raw data in one raw data cache of the memory at a time, and the size of the raw data cache of the memory can be set according to the computing power of the video memory, thereby more reasonably, fully and efficiently utilizing the computing power of the video memory; and the data copying process between each raw data cache and event cache can be carried out simultaneously, which greatly reduces the time consumed by each copying process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a flow chart of a coincidence event screening device for full digital PET provided by an embodiment of the present invention;

[0023] Figure 2 This is a schematic structural diagram of a CUDA-based system for a coincidence event screening device for full-digital PET provided by an embodiment of the present invention;

[0024] Figure 3 This is an overall flow chart based on CUDA of a coincidence event screening device for full digital PET provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] 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 with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] In order to illustrate the technical solution of the present invention, specific embodiments are provided below.

[0027] like Figure 1 FIG2 is a flow chart of a method for screening a matching event for a fully digital PET according to an embodiment of the present invention. The overall process of the matching event screening device for a fully digital PET according to the present invention is performed in a CUDA-based system. Figure 2 FIG. 1 is a schematic diagram of a CUDA-based system structure of a screening device for matching events of full digital PET according to an embodiment of the present invention. Figure 3The figure shows the overall flow chart of the CUDA-based device for screening events for full digital PET provided by an embodiment of the present invention. Figure 2 It can be seen that the system includes a memory and a video memory, the memory includes at least two first original data buffers and at least two first event buffers, and the video memory includes a second original data buffer and a second event buffer.

[0028] Define event objects, including time information, energy information, and location information.

[0029] Step S1 : collecting data packets sent by the detector and writing them into the raw data cache of the memory, and copying the raw data in the raw data cache of the memory to the raw data cache of the video memory.

[0030] Specifically, an event loop mechanism is used to collect network data packets sent by a detector in a single thread, including: writing the collected data packets into a raw data cache in the memory; when a raw data cache in the memory is full, writing the next received data packet into the next raw data cache in the memory; and copying the raw data in the full raw data cache in the memory to the video memory.

[0031] In one method, the writing order of data in each original data buffer of the memory can be determined by setting numbers for the original data buffers of the memory.

[0032] The collected data packets are written into the raw data buffers of each memory in sequence according to the numbering order of the raw data buffers in the memory. That is, when the raw data buffer numbered n in the memory is full, the next received data packet is written into the raw data buffer numbered n+1 in the memory.

[0033] In another method, the writing order of data in each original data cache of the memory can be determined by the original data cache flag in the memory.

[0034] The flag of the raw data cache of the memory indicates whether the last state of the data transmission direction in the raw data cache of the memory is write or read. When there is data written in the raw data cache of the memory, its flag is modified to write; when there is data read from the raw data cache of the memory, its flag is changed to read.

[0035] The collected data packets are randomly written sequentially into any raw data buffer in the memory with the flag set to read. When the flag of the raw data buffer in the memory is read, it means that the last data transmission process of the raw data buffer in the memory was to copy the raw data to the raw data buffer of the video memory. At this time, the data packets sent by the acquisition detector can be written into any raw data buffer with the flag set to read.

[0036] Step S2: parse the raw data in the raw data buffer of the video memory to generate various events, write the generated events into the event buffer of the video memory, perform compliance screening on the various events in the event buffer of the video memory, and mark the compliance information of the events according to the compliance screening results.

[0037] Specifically, the raw data is parsed and the energy is calculated simultaneously in a single raw data buffer of the video memory, and the events generated by the parsing are written into a single event buffer of the video memory.

[0038] In the single event buffer within the display memory, events are screened for match based on their time, energy, and location information, and the results are recorded in each event's match information. Match information includes whether the event is a paired event and the index number of the paired event. Whether the event is a paired event indicates whether it is paired with another event to form a match event, meaning a match event represents two paired events. The index number of the paired event indicates the index number of the event that forms the match event with the event.

[0039] After all events in the single event buffer of the display memory are processed, the events in the single event buffer of the display memory are copied to an event buffer of the internal memory.

[0040] Specifically, the process of filtering each event in the event buffer of the video memory includes:

[0041] Step S201 , setting time periods, and placing events into respective time periods according to the time of each event, wherein the range of each time period is not larger than the range of the time window that meets the screening.

[0042] The present invention provides a method for screening matching events for fully digital PET. The fully digital PET includes a global clock system based on a high-precision clock reference source. The clock signal is generated based on a pulse signal. The time information contained in the event object includes a coarse time and eight fine times. The coarse time is determined by the pulse signal with a longer period, while the fine time is the time of eight sampling points based on the MVT sampling method, which is determined by the pulse signal with a shorter period.

[0043] Therefore, the time information of an event includes coarse time (4 bytes) and eight fine times (2 bytes), which greatly reduces the storage size of the time information.

[0044] Step S202: performing location matching judgment on events within a time period, and marking matching information of events with matching locations.

[0045] The present invention provides a method for screening events that meet the requirements of fully digital PET, which performs location matching judgment on events based on their IP addresses. The detector of the fully digital PET includes one-to-one coupled crystal bars and silicon photomultiplier tubes. The number of each crystal bar corresponds to its location information. The IP address of the detector corresponding to each crystal bar can represent the detector in obtaining the location information of the event object. The entire system can obtain the location information of the signal received by the detector more accurately and quickly.

[0046] Because the detector IP represents the position of the corresponding crystal bar, the effective detection area is smaller than the detector ring. For a detector with a given IP, a matching event must originate from a detector separated by a certain distance. In the embodiment presented herein, the PET includes two rings of 176 detectors. Based on the effective area and the detector ring size, it can be calculated that the positions of two events with an IP separation greater than 20 are matching.

[0047] Step S20201, determine whether the positions of the i-th event and the i+1-th event are consistent with the judgment, if not, execute step S20202; if yes, execute step S20203; i is a positive integer, preferably, the initial value of i is 1.

[0048] In step S20202, after i=i+1, execute step S20204.

[0049] When it is determined that the positions of the i-th and i+1-th events do not match, the i-th event with a smaller sequence number is abandoned, and the i+1-th event with a larger sequence number is used as the starting point to determine whether the i+1-th event and its next event match.

[0050] Step S20203: Mark the i-th and i+1-th events as paired events, and mark the paired event index numbers; after i=i+2, execute step S20204.

[0051] The index number of the paired event can be marked for either the i-th or i+1-th event, or for both events. After the i-th and i+1-th events are determined to be matching, the matching is then determined for the i+2-th event and the event immediately following it, starting with the i+2-th event.

[0052] Step S20204, determine whether all the events have completed the position compliance judgment, if yes, execute the step S203, if not, execute the step S20201.

[0053] When any event fails to complete the position conformity judgment, step S20201 is executed again and the position conformity judgment is restarted with the newly obtained i.

[0054] Step S203 , calculating the energy information of each event, performing energy screening on the events in sequence according to the energy information of the events, and discarding the events that do not meet the energy screening requirements and the paired events with them.

[0055] Determine whether the event meets the energy screening requirements, that is, determine whether the energy information of the event is within the range of the energy window. When it is determined that any event does not meet the energy screening requirements, the event corresponding to the index number of its paired event is also discarded. That is, when it is determined that the energy screening does not meet the requirements, the two paired events are discarded in pairs, and finally the meeting events are obtained.

[0056] The present invention provides a coincidence event screening device for fully digital PET. The fully digital PET adopts one-to-one coupled crystal bars and silicon photomultiplier tubes. The IP address of the detector corresponding to each crystal bar can represent the detector to obtain the location information of the event, so the location information corresponding to the event can be obtained more accurately and directly. The fully digital PET also adopts a global clock system based on a high-precision clock reference source. According to the clock signal generated by the pulse signal, the time information contained in the event object includes a coarse time and eight fine times, the time accuracy is greatly improved, and the storage space of the time information is greatly reduced. Software is used to screen PET coincidence events. The data based on it is intuitive and available, the calculation process is simple, the calculation rate and accuracy are high, and the hardware maintenance cost is low. In addition, the threshold data for the coincidence screening calculation can be adjusted according to needs or different test conditions, and feedback optimization can be performed based on the results of the specific test process.

[0057] Step S3, copying the events that meet the screening requirements in the event buffer of the display memory to an event buffer of the internal memory, and then browsing the event buffer of the internal memory to save the events that meet the requirements according to the matching information.

[0058] In one method, the writing order of data in each event buffer of the memory may be determined by setting numbers for the event buffers of the memory.

[0059] The events that have completed the filtering are copied to each event cache in the memory in the order of the event cache number in the memory. That is, when the event cache numbered n in the memory is full, the next event that has completed the filtering is copied to the event cache numbered n+1 in the memory.

[0060] In another method, the writing order of data of each event cache in the memory can be determined by the event cache flag in the memory.

[0061] The flag of the event cache of the memory indicates whether the event cache of the memory has completed the process of browsing and saving the events that match. When the event cache of the memory completes the process of browsing and saving the events that match, its flag is modified to completed. When data is copied into the event cache of the memory, its flag is modified to incomplete.

[0062] The events that have completed the screening are randomly copied to any event buffer in the memory with the flag set to "completed". When the flag of the event buffer in the memory is "completed", it means that the events stored in it have completed the process of browsing and saving the events that meet the requirements. At this time, the events that have completed the screening in the event buffer in the video memory can be copied to any event buffer in the memory with the flag set to "completed".

[0063] An embodiment of the present invention further provides an apparatus for screening coincident events for a fully digital PET, comprising a processor and a memory. The memory is configured to store a plurality of instructions, which are adapted for the processor to load and execute all steps of a method for screening coincident events for a fully digital PET. For details, see the description of the method embodiment above.

[0064] In one embodiment, when the processor is running, the following steps may be performed:

[0065] Step S201 , setting time periods, and placing events into respective time periods according to the time of each event, wherein the range of each time period is not larger than the range of the time window that meets the screening.

[0066] Step S202: performing location matching judgment on events within a time period, and marking matching information of events with matching locations.

[0067] Furthermore, the compliance information includes whether it is a pairing event and the index number of the pairing object event. Whether it is a pairing event indicates whether the event is paired with another event to form a compliance event, that is, a compliance event represents two paired events that are paired with each other; the index number of the pairing object event represents the index number of the event that forms a compliance event with the event.

[0068] Step S203 , calculating the energy information of each event, performing energy screening on the events in sequence according to the energy information of the events, and discarding the events that do not meet the energy screening requirements and the paired events with them.

[0069] In this embodiment of the present invention, time periods are set and events are sorted into these time periods according to their time. The range of each time period is no larger than the range of the time window for time filtering, ensuring that any two events in each time period meet the time filtering criteria. Subsequent time filtering and sorting are no longer necessary.

[0070] It is determined whether the positions and times of the two events constitute a paired event, and then whether the energy screening of the two events in the paired event is determined to be consistent. If it is determined that any event in the paired event does not meet the energy screening, the two events included in the paired event are abandoned, reducing the steps required for the entire event pairing process and speeding up the processing time.

[0071] An embodiment of the present invention provides a coincidence event screening device for full-digital PET, which calculates the information of each energy after the position and time coincidence screening, fully utilizes the computing power of each time period in the memory, reduces the time consumed by subsequent coincidence screening, and speeds up the entire coincidence screening process.

[0072] Those skilled in the art can also understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium includes ROM / RAM, disk, CD-ROM, etc.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A coincidence event screening device for all-digital PET, the coincidence event screening device comprising a memory and a video memory, the memory comprising at least two first raw data buffers and at least two first event buffers, the video memory comprising a second raw data buffer and a second event buffer, characterized in that: The first raw data cache is used to write the raw data packets sent by the detector; The second raw data cache is used to copy the raw data in the first raw data cache and parse the raw data to generate various events; The second event buffer is used to write each generated event, perform compliance screening on each event, and mark the compliance information of the event according to the compliance screening result; The first event cache is used to copy the events that meet the screening requirements and save the events according to the matching information; The second event cache places the events into preset time periods according to the time of each event to perform time compliance screening, and the range size of each time period is not larger than the range size of the time window for time compliance screening.

2. The matching event screening device according to claim 1, wherein: The first raw data cache adopts an event loop mechanism and a single thread to collect data packets sent by the detector.

3. The matching event screening device according to claim 2, characterized in that: When one of the first original data buffers is full, the received data packet is written into the next first original data buffer, and the data in the full first original data buffer is copied to the video memory.

4. The matching event screening device according to claim 1, wherein: The first original data cache determines a writing order of the original data according to a preset number.

5. The matching event screening device according to claim 1, wherein: The first original data cache determines a writing order of the original data according to a flag bit.

6. The matching event screening device according to claim 1, characterized in that: After performing time matching screening, the second event cache performs location matching judgment based on events within a time period, and marks matching information of events with matching locations.

7. The matching event screening device according to claim 6, characterized in that: The second event cache performs location matching judgment on the event according to the IP address of the event, and the IP address corresponds to the crystal bar of the detector one by one.

8. The matching event screening device according to claim 6, characterized in that: After performing position compliance judgment, the second event cache calculates the energy information of each event, performs energy screening on the events in turn according to the energy information of the events, and discards events that do not comply with the energy screening and events paired with events that do not comply with the energy screening.

9. The matching event screening device according to claim 1, wherein: The first event buffer determines a writing order of data in the second event buffer according to a preset number.

10. The matching event screening device according to claim 1, wherein: The first event buffer determines a writing order of data in the second event buffer according to the flag bit.

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