Method of identifying prompt gamma photon events, data reconstruction method, and electronic device

Abstract

The application belongs to the technical field of medical treatment and provides a prompt gamma photon event identification method, a data reconstruction method and an electronic device. The prompt gamma photon event identification method comprises the following steps: obtaining first TOF data of a double-coincidence event detected by a detector, the double-coincidence event being two simultaneous associated events; determining second TOF data of a triple-coincidence event according to the first TOF data, the triple-coincidence event being three simultaneous associated events; performing one or more verification operations to determine a prompt gamma photon position; and determining a prompt gamma photon event in the triple-coincidence event based on the prompt gamma photon position. The embodiments of the application can effectively identify the prompt gamma photon event by using the TOF data, which is helpful to separate the double-nuclide signal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of medical treatment, and particularly relates to a prompt gamma photon event identification method, a data reconstruction method and an electronic device. BACKGROUND

[0002] Positron Emission Tomography (PET) is one of the current super high sensitivity and specificity in vivo molecular imaging methods, and has become an important tool for tumor research and clinical diagnosis and treatment. The principle of PET imaging is to use the nuclide emitted in the decay process to interact with the electrons in the surrounding matter, and to emit two photons with opposite directions and equal energy through annihilation radiation. Based on the two photons, the tomographic distribution of the body positron nuclide is obtained to show the location, shape, size and metabolic function of the lesion, and to diagnose the disease.

[0003] Traditional PET single scan imaging can only perform functional imaging on one tracer, and has limited ability to depict complex life activities. PET multiple scan imaging can provide more comprehensive life activity information, but has high economic and time costs, and the registration problem between multiple scans also affects the final imaging quality. Therefore, multiple tracer single PET scan imaging has important significance in clinical application.

[0004] However, some nuclides will emit prompt gamma photon rays (prompt-γ rays) with a certain probability at the same time of decay, and three coincidence events can be generated after positron annihilation. However, in the traditional multiple tracer single PET scan imaging process, only double coincidence events can be identified and output, and prompt gamma photon events (prompt-γ events) cannot be identified in three coincidence events, which further leads to the inability to effectively separate double nuclide signals. SUMMARY

[0005] The prompt gamma photon event identification method, the data reconstruction method and the electronic device provided in the embodiments of the present application can effectively identify prompt gamma photon events by using TOF data, which is helpful to separate double nuclide signals.

[0006] In a first aspect, the embodiments provide a method for identifying prompt gamma photon events, comprising: obtaining first TOF data of a double coincidence event detected by a detector; the double coincidence event being two simultaneous associated events; determining second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event being three simultaneous associated events; performing one or more verification operations to determine a prompt gamma photon position; determining a prompt gamma photon event in the triple coincidence event based on the prompt gamma photon position; the verification operation comprising: selecting a candidate true double coincidence event and a candidate prompt gamma photon position based on the triple coincidence event; obtaining a candidate decay position based on detection positions and TOF information of the candidate true double coincidence event; obtaining estimated TOF data of the triple coincidence event based on the candidate decay position; determining the candidate prompt gamma photon position as the prompt gamma photon position in response to the estimated TOF data matching the second TOF data.

[0007] In some embodiments of the first aspect, the method further comprises: determining a time-of-flight error amount between the estimated TOF data and the second TOF data; and confirming that the estimated TOF data matches the second TOF data if the time-of-flight error amount is less than an error amount threshold.

[0008] In some embodiments of the first aspect, the determining a time-of-flight error amount between the estimated TOF data and the second TOF data comprises: determining a reference TOF vector according to the second TOF data; and calculating a distance between a TOF vector corresponding to the estimated TOF data and the reference TOF vector to obtain the time-of-flight error amount.

[0009] In some embodiments of the first aspect, the obtaining a candidate decay position based on detection positions and TOF information of the candidate true double coincidence event comprises: obtaining the detection positions and the TOF information of the candidate true double coincidence event; and performing weighted addition on the detection positions of the candidate true double coincidence event according to the weighted weights to obtain the candidate decay position.

[0010] In some embodiments of the first aspect, the determining a weighted weight based on detection positions and TOF information of the candidate true double coincidence event comprises: calculating a distance between a pair of photons corresponding to the candidate true double coincidence event according to the detection positions of the candidate true double coincidence event; dividing a time-of-flight corresponding to the TOF information by the distance between the pair of photons to determine the weighted weight based on a division result and a speed of light.

[0011] In some embodiments of the first aspect, the determining the second TOF data of the three coincidence events according to the first TOF data comprises: determining, according to the first TOF data, double coincidence events with the same detection position; and determining the second TOF data according to the double coincidence events with the same detection position.

[0012] In some embodiments of the first aspect, the events with the same detection position comprise three double coincidence events, each two of the three double coincidence events have one of the same detection position, and the same detection position between each two of the three double coincidence events is different; and the determining the second TOF data according to the double coincidence events with the same detection position comprises: detecting whether TOF information of the three double coincidence events satisfies a time condition; and generating the second TOF data according to detection positions and TOF information of the three double coincidence events if the TOF information of the three double coincidence events satisfies the time condition.

[0013] In some embodiments of the first aspect, the events with the same detection position comprise two double coincidence events; and the determining the second TOF data according to the double coincidence events with the same detection position comprises: determining TOF information of a third double coincidence event according to TOF information of the two double coincidence events; and generating the second TOF data according to detection positions and TOF information of the two double coincidence events and the TOF information of the third double coincidence event.

[0014] In embodiments of the present application, by obtaining the first TOF data of the double coincidence events detected by the detector, determining the second TOF data of the three coincidence events according to the first TOF data, and performing one or more verification operations to determine the position of the prompt gamma photon and determine the prompt gamma photon event in the three coincidence events based on the position of the prompt gamma photon, the TOF data of the three coincidence events can be obtained using the TOF information of the double coincidence events, and the position of the prompt gamma photon can be verified using the TOF information of the three coincidence events, so as to effectively identify the prompt gamma photon event in the three coincidence events, which helps to separate the double-nuclide signal.

[0015] In the second aspect, a PET data reconstruction method is provided. The method comprises: obtaining first TOF data of a double coincidence event detected by a detector; the double coincidence event is two simultaneous associated events; determining second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event is three simultaneous associated events; performing one or more verification operations to determine a true double coincidence event; reconstructing TOF data corresponding to the true double coincidence event to obtain a TOF image; the verification operation comprises: selecting a candidate true double coincidence event based on the triple coincidence event; obtaining a candidate decay position based on a detection position and TOF information of the candidate true double coincidence event; obtaining estimated TOF data of the triple coincidence event based on the candidate decay position; and determining the candidate true double coincidence event as the true double coincidence event in response to the estimated TOF data matching the second TOF data.

[0016] In the embodiments of the present application, the TOF condition of the triple coincidence event can be used to determine the true double coincidence event, facilitate the reconstruction of the TOF data corresponding to the true double coincidence event to obtain the TOF image, and help improve the reliability of the TOF image.

[0017] In the third aspect, a device for identifying prompt gamma photon events is provided. The device comprises: an obtaining unit configured to obtain first TOF data of a double coincidence event detected by a detector; the double coincidence event is two simultaneous associated events; a determining unit configured to determine second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event is three simultaneous associated events; a verification unit configured to perform one or more verification operations to determine a prompt gamma photon position; and an identifying unit configured to determine a prompt gamma photon event in the triple coincidence event based on the prompt gamma photon position. The verification unit is specifically configured to: select a candidate true double coincidence event and a candidate prompt gamma photon position based on the triple coincidence event; obtain a candidate decay position based on a detection position and TOF information of the candidate true double coincidence event; obtain estimated TOF data of the triple coincidence event based on the candidate decay position; and determine the candidate prompt gamma photon position as the prompt gamma photon position in response to the estimated TOF data matching the second TOF data.

[0018] The fourth aspect of the embodiment of the present application provides a PET data reconstruction device, comprising: an acquisition unit configured to acquire first TOF data of a double coincidence event detected by a detector; the double coincidence event is two simultaneous associated events; a determination unit configured to determine second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event is three simultaneous associated events; a verification unit configured to perform one or more verification operations to determine a true double coincidence event; and a reconstruction unit configured to reconstruct TOF data corresponding to the true double coincidence event to obtain a TOF image; the verification unit is specifically configured to: select a candidate true double coincidence event based on the triple coincidence event; acquire a candidate decay position based on a detection position and TOF information of the candidate true double coincidence event; acquire estimated TOF data of the triple coincidence event based on the candidate decay position; and determine the candidate true double coincidence event as the true double coincidence event in response to the estimated TOF data matching the second TOF data.

[0019] The fifth aspect of the embodiment of the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the following steps when executing the computer program: acquiring first TOF data of a double coincidence event detected by a detector; the double coincidence event is two simultaneous associated events; determining second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event is three simultaneous associated events; performing one or more verification operations to determine a prompt gamma photon position; determining a prompt gamma photon event based on the prompt gamma photon position, and deleting TOF data corresponding to the prompt gamma photon event from the second TOF data; the verification operation comprises: selecting a candidate true double coincidence event and a candidate prompt gamma photon position based on the triple coincidence event; acquiring a candidate decay position based on a detection position and TOF information of the candidate true double coincidence event; acquiring estimated TOF data of the triple coincidence event based on the candidate decay position; and determining the candidate prompt gamma photon position as the prompt gamma photon position in response to the estimated TOF data matching the second TOF data.

[0020] The sixth aspect of the embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the prompt gamma photon event identification method or the steps of the PET data reconstruction method.

[0021] The seventh aspect of the embodiments of the present application provides a computer program product, when the computer program product is executed on an electronic device, causes the electronic device to perform the steps of the method for identifying prompt gamma photon events or causes the electronic device to perform the steps of the method for reconstructing PET data.

[0022] It can be understood that the beneficial effects of the third aspect to the seventh aspect can be referred to the related description in the first aspect and the second aspect, and will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 is an implementation flow diagram of the method for identifying prompt gamma photon events provided by the embodiments of the present application;

[0025] Figure 2 is a schematic diagram of a detector provided by the embodiments of the present application;

[0026] Figure 3 is a specific implementation flow diagram of the verification operation provided by the embodiments of the present application;

[0027] Figure 4 is a specific implementation flow diagram of the method for determining second TOF data provided by the embodiments of the present application;

[0028] Figure 5 is an implementation flow diagram of the method for reconstructing PET data provided by the embodiments of the present application;

[0029] Figure 6 is a structure diagram of a device for identifying prompt gamma photon events provided by the embodiments of the present application;

[0030] Figure 7 is a structure diagram of a device for reconstructing PET data provided by the embodiments of the present application;

[0031] Figure 8 is a structure diagram of an electronic device provided by the embodiments of the present application. DETAILED DESCRIPTION

[0032] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application and not to limit the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work belong to the present application.

[0033] It should be understood that when used in the specification and the appended claims of the present application, the term "comprising" indicates the presence of described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0034] In the description of the specification and the appended claims of the present application, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0035] In the present application, the reference "one embodiment" or "some embodiments" and the like means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in further some embodiments" and the like appearing in different places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "include", "contain", "have" and their variants mean "include but not limited to", unless otherwise specifically emphasized.

[0036] Traditional PET single scan imaging can only perform functional imaging on one tracer, and the ability to depict complex life activities is limited. PET multi-scan imaging can more comprehensively provide life activity information, but the economic and time cost is high, and the registration problem between multiple scans will also affect the final imaging quality. Therefore, multi-tracer single PET scan imaging has important significance in clinical application.

[0037] However, some nuclides emit prompt gamma photon rays with a certain probability while decaying, and three coincidence events can be generated after positron annihilation. However, in the traditional multi-tracer single PET scan imaging process, only double coincidence events can be identified and output, and prompt gamma photon events cannot be identified in three coincidence events, which further leads to the inability to effectively separate double nuclide signals.

[0038] Therefore, the application provides a prompt gamma photon event identification method, which can obtain TOF data of triple coincidence events by using the TOF of double coincidence events, and effectively identify prompt gamma photon events in the triple coincidence events by using the TOF of the triple coincidence events, thereby helping to separate double-nucleus signals.

[0039] For the convenience of understanding, some professional terms mentioned in the application are first described.

[0040] Photon pair: a pair of photons with opposite directions generated when a particle and an electron annihilate, which can be referred to as a beta + Photon pair.

[0041] Coincidence event: a simultaneous correlation event detected by using coincidence detection technology and recorded as a coincidence count. Double coincidence events are two simultaneous correlation events. Triple coincidence events are three simultaneous correlation events. In the embodiments of the application, the triple coincidence events can be referred to as beta + Photon pairs generate double coincidence events, and prompt gamma photon events are generated due to the emission of prompt gamma photon rays during decay.

[0042] Prompt gamma photon event: prompt-γ event, which refers to an additional single gamma photon generated in addition to a pair of photons with opposite directions when annihilation occurs. Since the time difference between the gamma photon and the photon pair is only in the order of picoseconds (ps), the gamma photon is referred to as a prompt gamma photon (prompt-γ).

[0043] TOF: Time of Flight, flight time, in the application, refers to the time difference of a pair of photons reaching a PET detector, that is, the difference of detection time.

[0044] Detection position: the position of the photon received by the detector.

[0045] Decay position: the position of the decay.

[0046] In order to illustrate the technical scheme of the application, the following specific embodiments are described.

[0047] Please refer to Figure 1 , Fig. 1 shows a flowchart of the implementation of a prompt gamma photon event identification method provided by the embodiments of the application, which can be applied to an electronic device. The electronic device can be a computer, a PET device, or other intelligent devices capable of processing TOF data, and the application does not limit the electronic device.

[0048] Specifically, the prompt gamma photon event identification method described above can include the following steps S101 to S104.

[0049] Step S101: Obtain the first TOF data of the double coincidence event detected by the detector.

[0050] In embodiments of this application, the aforementioned detector may refer to a PET detector. A PET detector may be a ring structure formed by multiple detector units, used to capture photons generated during annihilation. Electronic devices can obtain the first TOF data collected by the PET detector over a period of time through wired or wireless communication.

[0051] A double coincidence event consists of two simultaneous, related events. The first Time-of-Flight (TOF) data for a double coincidence event is generated based on the detector's detection results of the double coincidence event, carrying data about the time of flight between the two events. The first TOF data can include the detection location and TOF information of the double coincidence event, and can be arranged using list-modulation. e The data is represented in the form of (p1, p2, t). Specifically, the first TOF data can be represented as (p1, p2, t). 12 (where p1 and p2 are the detection positions of the photons.) 12 This is the difference between the detection times of p1 and p2, i.e., the flight time of events p1 and p2.

[0052] In the embodiments of this application, please refer to Figure 2 Because some nuclides emit transient gamma photons with a certain probability during their decay ( Figure 2 As shown by the dashed line, the double coincidence events detected by the detector can include double coincidence events generated by photon pairs (or true double coincidence events), or double coincidence events consisting of a transient gamma photon event and an event corresponding to one photon in a photon pair (or false double coincidence events).

[0053] Step S102: Determine the second TOF data for the three coincidence events based on the first TOF data.

[0054] In the embodiments of this application, a triple coincidence event refers to three simultaneously occurring related events. These can refer to a double coincidence event generated by a photon pair and a transient gamma photon event generated by the simultaneous emission of a transient gamma photon ray during decay. The flight times of these three events are temporally correlated. The second TOF data for the triple coincidence event carries TOF information between each pair of the three coincidence events, which may include the detection positions of the three events and the flight times between each pair of the three events.

[0055] Specifically, a triplet event has three photons, so the second TOF data can be represented as:

[0056] {(p1, p2, t 12 ), (p1, p3, t 13), (p2, p3, t 23 )}.

[0057] wherein p1, p2, p3 represent the detection positions of three photons respectively, corresponding to a true coincidence event of a photon pair, and a prompt gamma photon event. t 12 is the difference between the detection time of p1 and p2, t 13 is the difference between the detection time of p1 and p3, t 23 is the difference between the detection time of p2 and p3. According to the definition of time of flight, it should be t 23 = t 13 -t 12 Based on the correlation of time of flight, the second TOF data of the three-coincidence event can be determined according to the first TOF data.

[0058] Step S103, performing one or more verification operations to determine the prompt gamma photon position.

[0059] In the embodiments of the present application, after obtaining the second TOF data, one or more verification operations can be performed to determine the prompt gamma photon position according to the detection positions of the three photons and the TOF information between each other. The prompt gamma photon position refers to the detection position of the prompt gamma photon.

[0060] In the embodiments of the present application, as shown in Figure 3 , the verification operation can include steps S301 to S304.

[0061] Step S301, selecting a candidate true coincidence event and a candidate prompt gamma photon position based on the three-coincidence event.

[0062] In the embodiments of the present application, the true coincidence event refers to a coincidence event in which the two detected photons originate from the same annihilation event, and neither of the two photons has any interaction with the medium before reaching the detector. Among the three detection positions of the three-coincidence event, one must correspond to the prompt gamma photon, and the other two correspond to the photon pair generated by the positron-electron annihilation with an included angle of π. For the second TOF data {(p1, p2, t 12 ), (p1, p3, t 13 ), (p2, p3, t 23 )}, it is known that it is the TOF data of the three-coincidence event, but which one of p1, p2, p3 corresponds to the prompt gamma photon event is unknown. Therefore, one of the three-coincidence events can be selected as the prompt gamma photon event, and the detection position corresponding thereto is the candidate prompt gamma photon position; at this time, the remaining two events are selected as the candidate true coincidence events.

[0063] For example, if p1 is selected as the candidate prompt gamma photon position, then p2 and p3 correspond to a candidate true coincidence event. If p2 is selected as the candidate prompt gamma photon position, then p1 and p3 correspond to a candidate true coincidence event. If p3 is selected as the candidate prompt gamma photon position, then p1 and p2 correspond to a candidate true coincidence event.

[0064] At step S302, a candidate decay position is obtained based on the detection position and TOF information of the candidate true coincidence event.

[0065] Based on the detection position and TOF information of the candidate true coincidence event, the decay occurrence position corresponding to the candidate true coincidence event can be determined, which is taken as the candidate decay position.

[0066] Specifically, step S302 can include: determining a weighting weight according to the detection position and TOF information of the candidate true coincidence event, and performing weighted addition on the detection position of the candidate true coincidence event according to the weighting weight to obtain the candidate decay position.

[0067] The determination of the weighting weight according to the detection position and TOF information of the candidate true coincidence event can include: calculating the distance between the photon pair corresponding to the candidate true coincidence event according to the detection position of the candidate true coincidence event, dividing the flight time corresponding to the TOF information by the distance between the photon pair, and determining the weighting weight according to the division result and the speed of light.

[0068] p1, p2 and p3 are respectively taken as the candidate prompt gamma photon position, and are classified and discussed. Let c be the speed of light, “:=” be the assignment symbol, and “||a-b||” represent the distance between a and b.

[0069] Let p1 be the candidate prompt gamma photon position. At this time, the true coincidence event generated by the photon pair is (p2, p3, t 23 ), and the candidate decay position p 23 :=λp2+(1-λ)p3 can be calculated, where the weighting weight λ:=(1-c·t 23 / ||p2-p3||) / 2.

[0070] Let p2 be the candidate prompt gamma photon position. At this time, the true coincidence event generated by the photon pair is (p1, p3, t 13 ), and the candidate decay position p 13 :=λp1+(1-λ)p3 can be calculated, where the weighting weight λ:=(1-c·t 13 / ||p1-p3||) / 2.

[0071] Let p3 be the candidate prompt gamma photon position. At this time, the true coincidence event generated by the photon pair is (p1, p2, t 12), the candidate decay position p can be calculated 12 : = λp1+ (1 - λ)p2, where the weighting weight λ: = (1 - c · t 12 / ||p1-p2||) / 2.

[0072] In step S303, based on the candidate decay position, the estimated TOF data of the three coincidence events is obtained.

[0073] Wherein, the estimated TOF data can include TOF information between each two events in the three coincidence events, which can be expressed as (t' 12 , t' 13 , t' 23 ). Specifically, for the candidate decay position, substituting the second TOF data {(p1, p2, t 12 ), (p1, p3, t 13 ), (p2, p3, t 23 )} can generate a corresponding estimated TOF data (t' 12 , t' 13 ', t' 23 ).

[0074] In step S304, in response to the estimated TOF data matching the second TOF data, the candidate prompt gamma photon position is determined as the prompt gamma photon position.

[0075] If the estimated TOF data matches the second TOF data, it means that the candidate true double coincidence event and the candidate prompt gamma photon position selected by the estimated TOF data are consistent with the actual detection result, so the candidate prompt gamma photon position can be determined as the prompt gamma photon position. If the estimated TOF data does not match the second TOF data, it means that the candidate true double coincidence event and the candidate prompt gamma photon position selected by the estimated TOF data are not consistent with the actual detection result, so the assumption of the candidate true double coincidence event and the candidate prompt gamma photon position needs to be discarded.

[0076] Specifically, in the verification process, the identification method provided by the application can further include: determining the time-of-flight error amount between the estimated TOF data and the second TOF data; if the time-of-flight error amount is less than the error amount threshold, confirming that the estimated TOF data matches the second TOF data.

[0077] In the embodiments of the application, the smaller the time-of-flight error amount, the closer the candidate decay position to the decay position corresponding to the true double coincidence event. If the time-of-flight error amount is less than the error amount threshold, it can be confirmed that the estimated TOF data matches the second TOF data. If the time-of-flight error amount is greater than or equal to the error amount threshold, it can be confirmed that the estimated TOF data does not match the second TOF data.

[0078] Specifically, according to the second TOF data, a reference TOF vector can be determined, and a distance between a TOF vector corresponding to the estimated TOF data and the reference TOF vector is calculated to obtain a time-of-flight error.

[0079] wherein the reference TOF vector represents a true value of the three coincidence event TOF vector. According to the second TOF data {(p1, p2, t 12 ), (p1, p3, t 13 ), (p2, p3, t 23 )}, the reference TOF vector (t 12 , t 13 , t 23 ) can be determined. Based on the estimated TOF data, a corresponding TOF vector (t' 12 , t' 13 , t' 23 ) can be obtained. By calculating a distance dist((t 12 , t 13 , t 23 ), (t' 12 , t' 13 , t' 23 )) between the TOF vector corresponding to the estimated TOF data and the reference TOF vector, a time-of-flight error can be obtained. Wherein dist is a distance function, which can be a Euclidean distance function, a Manhattan distance function, etc., which is not limited in the present application.

[0080] It can be understood that the distance is positively correlated with the time-of-flight error.

[0081] In the embodiments of the present application, p1, p2, and p3 are respectively taken as prompt gamma photon events, and then combinations of three candidate true coincidence events and candidate prompt gamma photon positions can be obtained. The present application can verify each combination, or verify each combination one by one until the prompt gamma photon position is obtained, and the prompt gamma photon position can be obtained through at least one verification.

[0082] For example, it is assumed that the three coincidence event data satisfies p1:=(1, 0), p2:=(0, 1), p3:=(0, 0), and the reference TOF vector (t 12 , t 13 , t 23 ):=(0, 0, 0), and then the following can be obtained according to the classification:

[0083] It is assumed that p1 corresponds to a prompt gamma photon event, and at this time, the decay position p 23 :=(0, 0.5) is selected, and the corresponding TOF vector is which is inconsistent with the reference TOF vector.

[0084] Let p2 correspond to a transient gamma photon event, where the candidate decay position p is... 13 = (0.5, 0), the corresponding TOF vector is It does not match the reference TOF vector.

[0085] Let p3 correspond to a transient gamma photon event, where the candidate decay position p is... 12 = (0.5, 0.5), the corresponding TOF vector is (t′ 12 ,t′ 13 ,t′ 23 = (0, 0, 0), which is 0 distance from the reference TOF vector (i.e., it matches).

[0086] Therefore, it can be determined that p 12 p1 represents the decay position of a true double coincidence event, and p2 represents the position of a transient gamma photon.

[0087] Step S104: Based on the position of the transient gamma photon, determine the transient gamma photon event from the three coincidence events.

[0088] In the embodiments of this application, the event in which the detection position is the position of a transient gamma photon in the three coincidence events is a transient gamma photon event.

[0089] In the embodiments of this application, by acquiring the first TOF data of a double coincidence event detected by the detector, determining the second TOF data of a triple coincidence event based on the first TOF data, performing one or more verification operations to determine the position of the transient gamma photon, and determining the transient gamma photon event in the triple coincidence event based on the position of the transient gamma photon, the TOF data of the triple coincidence event can be obtained using the TOF situation of the double coincidence event, and the position of the transient gamma photon can be verified using the TOF situation of the triple coincidence event, so as to effectively identify the transient gamma photon event in the triple coincidence event, which helps to separate the dual nuclide signal.

[0090] like Figure 4 As shown, in some embodiments of this application, determining the second TOF data of the three coincidence events based on the first TOF data may include steps S401 to S402.

[0091] Step S401: Based on the first TOF data, determine that there are double coincidence events at the same detection location.

[0092] It can be understood that if there is an event corresponding to the same photon in two different double coincidence events, the detection positions of the two events should be the same. For a triple coincidence event, there is necessarily an event corresponding to the same photon between the two double coincidence events. Based on this principle, according to the detection positions in the first TOF data, double coincidence events with the same detection position can be determined. For example, the first TOF data (p1, p2, t 12 ) and the first TOF data (p1, p3, t 13 ) represent two different double coincidence events, and the detection position p1 is the same, which indicates that the two double coincidence events are double coincidence events with the same detection position, and there is an event corresponding to the same photon (i.e., the event corresponding to p1) between the two double coincidence events.

[0093] By comparing the detection positions of the first TOF data of all double coincidence events two by two, at least one pair of double coincidence events with the same detection position can be obtained.

[0094] In step S402, the second TOF data is determined according to the double coincidence events with the same detection position.

[0095] In the embodiments of the present application, for a pair of double coincidence events with the same detection position, the same detection position can correspond to one event, and the two detection positions that are not the same can each correspond to one event, so that the second TOF data of the triple coincidence event can be determined. For example, between the first TOF data (p1, p2, t 12 ) and the first TOF data (p1, p3, t 13 ), the detection position p1 is the same, p1 can correspond to the same event, and p2 and p3 can each correspond to one event.

[0096] Specifically, the present application provides two ways to obtain the second TOF data:

[0097] Method one:

[0098] The above-mentioned events with the same detection position include three double coincidence events, and there is one same detection position between each two double coincidence events, and the same detection positions between each two double coincidence events are different.

[0099] For example, (p1, p2, t 12 ), (p1, p3, t 13 ), and (p2, p3, t 23 ) represent the above-mentioned three double coincidence events. The same detection position between (p1, p2, t 12 ) and (p1, p3, t 13 ) is p1, and the same detection position between (p1, p2, t 12), (p2, p3, t 23 ) between the same detection position p2, (p1, p3, t 13 ), (p2, p3, t 23 ) between the same detection position p3.

[0100] At this time, determining the second TOF data according to the double coincidence events with the same detection position can include: detecting whether the TOF information of the three double coincidence events satisfies a time condition, and if the TOF information of the three double coincidence events satisfies the time condition, generating the second TOF data according to the detection positions and the TOF information of the three double coincidence events.

[0101] As described above, the time condition that the TOF information of the triple coincidence event should satisfy can be expressed as: t 23 = t 13 -t 12 .

[0102] If the TOF information of the three double coincidence events satisfies the time condition, it indicates that the three double coincidence events are true double coincidence events generated by the photon pair and the prompt gamma photon event, and at this time, the second TOF data {(p1, p2, t 12 ), (p1, p3, t 13 ), (p2, p3, t 23 )} can be generated according to the detection positions p1, p2, p3 and the TOF information t 12 , t 13 , t 23 .

[0103] If the TOF information of the three double coincidence events does not satisfy the time condition, it indicates that the three double coincidence events are not true double coincidence events generated by the photon pair and the prompt gamma photon event generated by the decay, and at this time, the three double coincidence events can be skipped.

[0104] The first mode can filter out the double coincidence events with the same detection position and satisfying the time condition in the collected first TOF data, and further generate the second TOF data of the triple coincidence event, which can guarantee the accuracy of the second TOF data of the triple coincidence event.

[0105] The second mode:

[0106] The above event with the same detection position includes two double coincidence events. For example, the two double coincidence events can be {(p1, p2, t 12 ), (p1, p3, t 13 )}, {(p2, p3, t 23 ), (p1, p3, t 13), or, {(p2, p3, t 23 ), (p2, p3, t 23 )}.

[0107] At this time, determining the second TOF data according to the two coincidence events with the same detection position can include: determining TOF information of a third coincidence event according to TOF information of the two coincidence events; and generating the second TOF data according to the detection positions and the TOF information of the two coincidence events and the TOF information of the third coincidence event.

[0108] Specifically, according to the time relationship of t 23 = t 13 -t 12 , the TOF information of the third coincidence event can be determined. At this time, the detection positions of the two coincidence events can include detection positions p1, p2, p3 and TOF information between the two coincidence events, and the second TOF data {(p1, p2, t 12 ), (p1, p3, t 13 ), (p2, p3, t 23 )} can be generated by combining the TOF information of the third coincidence event.

[0109] Taking the two coincidence events {(p1, p2, t 12 ), (p1, p3, t 13 )} as an example, the third coincidence event can be calculated by (p2, p3, t 23 := t 13 -t 23 ).

[0110] In this way, the TOF information of the third coincidence event can be supplemented when the third coincidence event is missing, and the second TOF data can be generated, which can improve the universality of the algorithm.

[0111] In some embodiments of the present application, after obtaining the prompt gamma photon event, the method can further include: removing the prompt gamma photon event in the three coincidence events to obtain a true coincidence event. Alternatively, the TOF data corresponding to the prompt gamma photon event is deleted from the second TOF data. For example, when p 12 is the target decay position, p3 is the prompt gamma photon event, and the true coincidence event can be determined as (p1, p2, t 12 ), and (p1, p3, t 13 ) and (p2, p3, t 23 ) are deleted.

[0112] The true double coincidence event can be used for double-nuclide imaging, image quality determination, or detector performance determination. The application scenario of the true double coincidence event is not limited in the present application.

[0113] Please refer to Figure 5 , Figure 5 An implementation flowchart of a PET data reconstruction method provided by an embodiment of the present application is shown, which can be applied to an electronic device. The electronic device can be a computer, a PET device, or other intelligent devices capable of PET data reconstruction, which are not limited in the present application.

[0114] The PET data reconstruction method can include steps S501 to S504.

[0115] In step S501, first TOF data of a double coincidence event detected by a detector is acquired.

[0116] The double coincidence event is two simultaneous associated events.

[0117] In step S502, second TOF data of a triple coincidence event is determined according to the first TOF data.

[0118] The triple coincidence event is three simultaneous associated events.

[0119] In step S503, one or more verification operations are performed to determine a true double coincidence event.

[0120] The verification operation can include: selecting a candidate true double coincidence event based on the triple coincidence event; acquiring a candidate decay position based on the detection position and TOF information of the candidate true double coincidence event; acquiring estimated TOF data of the triple coincidence event based on the candidate decay position; and determining the candidate true double coincidence event as the true double coincidence event in response to the estimated TOF data matching the second TOF data.

[0121] The specific implementation of steps S501 to S503 can refer to the description of Figures 1 to 4 The difference is that: Figures 1-4 The candidate prompt gamma photon position is determined as the prompt gamma photon position, and Figure 5 The candidate true double coincidence event is determined as the true double coincidence event, that is, Figure 5 The true double coincidence event in the triple coincidence event is focused on, which will not be described herein.

[0122] In step S504, TOF data corresponding to the true double coincidence event is reconstructed to acquire a TOF image.

[0123] The aforementioned TOF data can be TOF-PET data, and the corresponding TOF image can be a TOF-PET image. Based on the TOF data corresponding to the true double coincidence event, existing methods can be used to reconstruct the image and obtain the TOF image.

[0124] In the embodiments of this application, the TOF case of three coincidence events can be used to determine true double coincidence events, which facilitates the reconstruction of the TOF data corresponding to the true double coincidence events to obtain TOF images and helps to improve the reliability of TOF images.

[0125] It should be noted that, for the sake of simplicity, the aforementioned method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders.

[0126] like Figure 6 The diagram shown is a schematic diagram of a transient gamma photon event identification device 600 provided in an embodiment of this application. The transient gamma photon event identification device 600 is configured on an electronic device.

[0127] Specifically, the device 600 for identifying transient gamma photon events may include:

[0128] Acquisition unit 601 is used to acquire the first TOF data of a double coincidence event detected by the detector; the double coincidence event is two related events that occur simultaneously.

[0129] The determining unit 602 is used to determine the second TOF data of the three-consistency event based on the first TOF data; the three-consistency event is three related events that occur simultaneously.

[0130] Verification unit 603 is used to perform one or more verification operations to determine the position of the transient gamma photon;

[0131] The identification unit 604 is used to determine the transient gamma photon event from the three coincidence events based on the position of the transient gamma photon.

[0132] Specifically, the verification unit 603 is used to: select candidate true double coincidence events and candidate transient gamma photon positions based on the triple coincidence events; obtain candidate decay positions based on the detection positions and TOF information of the candidate true double coincidence events; obtain estimated TOF data of the triple coincidence events based on the candidate decay positions; and determine the candidate transient gamma photon position as the transient gamma photon position in response to the matching of the estimated TOF data with the second TOF data.

[0133] In some embodiments of the application, the verifying unit 603 can be specifically configured to: determine a time-of-flight error amount between the estimated TOF data and the second TOF data; and confirm that the estimated TOF data matches the second TOF data if the time-of-flight error amount is less than an error amount threshold.

[0134] In some embodiments of the application, the verifying unit 603 can be specifically configured to: determine a reference TOF vector according to the second TOF data; and calculate a distance between a TOF vector corresponding to the estimated TOF data and the reference TOF vector to obtain the time-of-flight error amount.

[0135] In some embodiments of the application, the verifying unit 603 can be specifically configured to: determine a weighting weight according to the detection position and the TOF information of the candidate true coincidence event; and add the detection positions of the candidate true coincidence events according to the weighting weight to obtain the candidate decay position.

[0136] In some embodiments of the application, the verifying unit 603 can be specifically configured to: calculate a distance between a photon pair corresponding to the candidate true coincidence event according to the detection position of the candidate true coincidence event; divide a time-of-flight corresponding to the TOF information by the distance between the photon pair to obtain a weighting weight according to a result of the division and a speed of light.

[0137] In some embodiments of the application, the determining unit 602 can be specifically configured to: determine a double-coincidence event with the same detection position according to the first TOF data; and determine the second TOF data according to the double-coincidence event with the same detection position.

[0138] In some embodiments of the application, the event with the same detection position includes three double-coincidence events, there is one same detection position between each two double-coincidence events of the three double-coincidence events, and the same detection position between each two double-coincidence events is different; and the determining unit 602 can be specifically configured to: detect whether TOF information of the three double-coincidence events satisfies a time condition; and generate the second TOF data according to the detection positions and the TOF information of the three double-coincidence events if the TOF information of the three double-coincidence events satisfies the time condition.

[0139] In some embodiments of the application, the event with the same detection position includes two double-coincidence events; and the determining unit 602 can be specifically configured to: determine TOF information of a third double-coincidence event according to TOF information of the two double-coincidence events; and generate the second TOF data according to the detection positions and the TOF information of the two double-coincidence events and the TOF information of the third double-coincidence event.

[0140] It should be noted that, for the convenience and brevity of description, the specific working process of the above-mentioned prompt gamma photon event identification device 600 can be referred to Figures 1 to 4 The corresponding process of the method will not be repeated here.

[0141] As Figure 7 Fig. 7 shows a structural schematic diagram of a PET data reconstruction device 700 provided by an embodiment of the present application, which is configured on an electronic device.

[0142] Specifically, the PET data reconstruction device 700 can include:

[0143] The acquisition unit 701 is configured to acquire first TOF data of a double coincidence event detected by a detector; the double coincidence event is two simultaneous associated events;

[0144] The determination unit 702 is configured to determine second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event is three simultaneous associated events;

[0145] The verification unit 703 is configured to perform one or more verification operations to determine a true double coincidence event;

[0146] The reconstruction unit 704 is configured to reconstruct TOF data corresponding to the true double coincidence event to obtain a TOF image;

[0147] The verification unit 703 is specifically configured to: select a candidate true double coincidence event based on the triple coincidence event; acquire a candidate decay position based on the detection position and TOF information of the candidate true double coincidence event; acquire estimated TOF data of the triple coincidence event based on the candidate decay position; and determine the candidate true double coincidence event as the true double coincidence event in response to the estimated TOF data matching the second TOF data.

[0148] It should be noted that, for the convenience and brevity of description, the specific working process of the above-mentioned PET data reconstruction device 700 can be referred to Figure 5 The corresponding process of the method will not be repeated here.

[0149] As Figure 8As shown, a schematic diagram of an electronic device 8 provided by an embodiment of the present application is shown. Specifically, the electronic device 8 can include a processor 80, a memory 81, and a computer program 82 stored in the memory 81 and executable on the processor 80. The processor 80 implements the following steps when executing the computer program 82: obtaining first TOF data of a double coincidence event detected by a detector; the double coincidence event is two simultaneous associated events; determining second TOF data of a triple coincidence event according to the first TOF data; the triple coincidence event is three simultaneous associated events; performing one or more verification operations to determine a prompt gamma photon position; determining a prompt gamma photon event based on the prompt gamma photon position, and deleting TOF data corresponding to the prompt gamma photon event from the second TOF data; the verification operation includes: selecting a candidate true double coincidence event and a candidate prompt gamma photon position based on the triple coincidence event; obtaining a candidate decay position based on the detection position and TOF information of the candidate true double coincidence event; obtaining estimated TOF data of the triple coincidence event based on the candidate decay position; and determining the candidate prompt gamma photon position as the prompt gamma photon position in response to the estimated TOF data matching the second TOF data.

[0150] The manner of determining the prompt gamma photon event based on the prompt gamma photon position can refer to the description of Figures 1-4 The electronic device 8 can delete TOF data corresponding to the prompt gamma photon event from the second TOF data when processing the TOF data, thereby deleting non-true double coincidence data.

[0151] In this way, the data remaining in the second TOF data can represent data of true double coincidence events, facilitating data analysis and PET data reconstruction.

[0152] The computer program can be divided into one or more modules / units, which are stored in the memory 81 and executed by the processor 80 to complete the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program in the electronic device 8.

[0153] The electronic device 8 can include, but is not limited to, a processor 80, a memory 81. Those skilled in the art can understand that Figure 8 The electronic device 8 is only an example and does not constitute a limitation on the electronic device 8, and can include more or fewer components than the diagram, or combine certain components, or different components, for example, the electronic device 8 can also include an input / output device, a network access device, a bus, etc.

[0154] The processor 80 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), programmable logic devices (PLD), discrete gates or transistor logic, discrete hardware components, or the like. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0155] The memory 81 can be an internal storage unit of the electronic device 8, such as a hard disk or a memory of the electronic device 8. The memory 81 can also be an external storage device of the electronic device 8, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, or the like. Further, the memory 81 can include both the internal storage unit and the external storage device of the electronic device 8. The memory 81 is used to store the computer program and other programs and data required by the electronic device 8. The memory 81 can also be used to temporarily store data that has been output or will be output.

[0156] It should be noted that, for the convenience and brevity of description, the structure of the electronic device 8 can also refer to the specific description of the structure in the method embodiments, which will not be repeated here.

[0157] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of software functional unit. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the present application. The specific working process of the unit and module in the system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0158] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in a certain embodiment can be referred to the relevant description of other embodiments.

[0159] Those skilled in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0160] In the embodiments provided in the present application, it should be understood that the disclosed apparatuses / devices and methods can be implemented in other ways. For example, the apparatus / device embodiments described above are merely illustrative. For example, the division of the modules or units is only a logical function division, and actual implementation can have another division manner. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units or components shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0161] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, i.e. they can be located in one place or distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the present embodiment.

[0162] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0163] The integrated module / unit, if implemented in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. The computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the contents included in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0164] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method of identifying prompt gamma photon events, characterized by, The method comprises: acquiring first TOF data of double coincidence events detected by a detector; the double coincidence events are two simultaneous associated events; determining second TOF data of triple coincidence events according to the first TOF data; the triple coincidence events are three simultaneous associated events; performing one or more verification operations to determine a prompt gamma photon position; determining a prompt gamma photon event in the triple coincidence events based on the prompt gamma photon position; the verification operation comprises: selecting a candidate true double coincidence event and a candidate prompt gamma photon position based on the triple coincidence events; acquiring a candidate decay position based on the detection position and TOF information of the candidate true double coincidence event; acquiring estimated TOF data of the triple coincidence events based on the candidate decay position; determining the prompt gamma photon position as the candidate prompt gamma photon position in response to the estimated TOF data matching the second TOF data.

2. The method of prompt gamma photon event identification of claim 1, wherein, The identification method further comprises: determining a time-of-flight error amount between the estimated TOF data and the second TOF data; confirming that the estimated TOF data matches the second TOF data if the time-of-flight error amount is less than an error amount threshold.

3. The method of prompt gamma photon event identification of claim 2, wherein, The determination of the time-of-flight error amount between the estimated TOF data and the second TOF data comprises: determining a reference TOF vector according to the second TOF data; calculating a distance between a TOF vector corresponding to the estimated TOF data and the reference TOF vector to obtain the time-of-flight error amount.

4. The method of prompt gamma photon event identification of claim 1, wherein, The acquisition of the candidate decay position based on the detection position and TOF information of the candidate true double coincidence event comprises: determining a weighting weight according to the detection position and TOF information of the candidate true double coincidence event; performing weighted addition on the detection positions of the candidate true double coincidence events according to the weighting weight to obtain the candidate decay position.

5. The method of prompt gamma photon event identification of claim 4, wherein, The determination of the weighting weight according to the detection position and TOF information of the candidate true double coincidence event comprises: calculating a distance between a photon pair corresponding to the candidate true double coincidence event according to the detection position of the candidate true double coincidence event; dividing a time-of-flight corresponding to the TOF information by the distance between the photon pair to determine a weighting weight according to a division result and a speed of light.

6. A method of identifying prompt gamma photon events as claimed in any one of claims 1 to 5, characterised in that, The determination of the second TOF data of the triple coincidence events according to the first TOF data comprises: determining double coincidence events with the same detection position according to the first TOF data; determining the second TOF data according to the double coincidence events with the same detection position.

7. The method of prompt gamma photon event identification of claim 6, wherein, The events with the same detection position comprise three double coincidence events, and there is one same detection position between each two of the three double coincidence events, and the same detection position between each two of the three double coincidence events is different; The determination of the second TOF data according to the double coincidence events with the same detection position comprises: detecting whether TOF information of the three double coincidence events satisfies a time condition; If TOF information of the three double coincidence events satisfies a time condition, the second TOF data is generated according to detection positions and TOF information of the three double coincidence events.

8. The method of prompt gamma photon event identification of claim 6, wherein, The events with the same detection position include two double coincidence events; The determining the second TOF data according to the double coincidence events with the same detection position includes: determining TOF information of a third double coincidence event according to TOF information of the two double coincidence events; generating the second TOF data according to detection positions and TOF information of the two double coincidence events and the TOF information of the third double coincidence event.

9. A method of PET data reconstruction, characterized by, includes: obtaining first TOF data of double coincidence events detected by a detector; the double coincidence events are two simultaneous associated events; determining second TOF data of three coincidence events according to the first TOF data; the three coincidence events are three simultaneous associated events; performing one or more verification operations to determine true double coincidence events; reconstructing TOF data corresponding to the true double coincidence events to obtain a TOF image; the verification operation includes: selecting candidate true double coincidence events based on the three coincidence events; obtaining candidate decay positions based on detection positions and TOF information of the candidate true double coincidence events; obtaining estimated TOF data of the three coincidence events based on the candidate decay positions; determining the candidate true double coincidence events as true double coincidence events in response to the estimated TOF data matching the second TOF data.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor implements the following steps when executing the computer program: obtaining first TOF data of double coincidence events detected by a detector; the double coincidence events are two simultaneous associated events; determining second TOF data of three coincidence events according to the first TOF data; the three coincidence events are three simultaneous associated events; performing one or more verification operations to determine prompt gamma photon positions; determining prompt gamma photon events based on the prompt gamma photon positions, and deleting TOF data corresponding to the prompt gamma photon events from the second TOF data; the verification operation includes: selecting candidate true double coincidence events and candidate prompt gamma photon positions based on the three coincidence events; obtaining candidate decay positions based on detection positions and TOF information of the candidate true double coincidence events; obtaining estimated TOF data of the three coincidence events based on the candidate decay positions; determining the candidate prompt gamma photon positions as prompt gamma photon positions in response to the estimated TOF data matching the second TOF data.

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