CN109998582B - Coincidence judging and selecting method, device, equipment and medium - Google Patents

Coincidence judging and selecting method, device, equipment and medium Download PDF

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CN109998582B
CN109998582B CN201910299086.5A CN201910299086A CN109998582B CN 109998582 B CN109998582 B CN 109998582B CN 201910299086 A CN201910299086 A CN 201910299086A CN 109998582 B CN109998582 B CN 109998582B
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coincidence
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CN109998582A (en
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李俊
郑威
杨隆梓
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Shanghai United Imaging Healthcare Co Ltd
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Priority to PCT/CN2020/084861 priority patent/WO2020211764A1/en
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    • A61B6/4266—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a plurality of detector units
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Abstract

The embodiment of the invention discloses a coincidence judging and selecting method, device, equipment and medium, and relates to the technical field of medical images. The method comprises the following steps: determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector; determining the occurrence time difference of the first event and the second event according to the period difference, the TDC value of the first event and the TDC value of the second event; and if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation. The coincidence judgment method, the coincidence judgment device, the coincidence judgment equipment and the coincidence judgment medium provided by the embodiment of the invention realize coincidence judgment of any two detectors in different detector units or in the same detector unit.

Description

Coincidence judging and selecting method, device, equipment and medium
Technical Field
The embodiment of the invention relates to the technical field of medical images, in particular to a coincidence judging and selecting method, device, equipment and medium.
Background
Positron Emission Tomography (PET) is a non-invasive imaging method. The imaging principle is that positron radioactive nuclide is marked on a molecular probe, and when positron generated by radioactive nuclide decay collides with negative electron in a living body and is annihilated, a pair of gamma photons with the energy of 511KeV and the movement directions approximately opposite to each other is emitted. PET uses a ring of detectors around the organism to convert incident gamma photons into electrical signals, thereby obtaining their energy, position, and time information. The position of a response line where an annihilation event is located is obtained through an annihilation coincidence technology, and the distribution of the positive electron nuclide in the organism is obtained through a two-dimensional or three-dimensional tomographic reconstruction algorithm, so that the physiological and biochemical processes in the organism are observed in vitro. As shown in fig. 1, two gamma photons 180 degrees apart are generated after a positron annihilation and are received by the detector pairs M0 and M10, the straight line of the photon flight between M0 and M10 is called a response line, and the photon arrival time difference is the path difference of the two photon flights.
Conventional PET systems usually have only one PET detector unit, which has a detector ring of more than twenty detectors inside the unit. Therefore, the conventional coincidence device can only process the coincidence judgment of the small window width among the data of each detector in one unit.
However, conventional PET devices with only one PET detector element have a small geometric solid angle coverage, and a large number of gamma photons escape from the gap at the two ends of the ring-shaped detector and are not collected by the detector, so that the detection efficiency of coincidence events is low. In order to improve the detection sensitivity, a plurality of PET detector units are symmetrically added at two ends of the annular detector.
For a detector arrangement consisting of a plurality of PET detector units, a coincidence processing device is required which can perform coincidence processing of any two detectors between different detector units. Because the response line formed by the detectors on the two units is longer than the response line between the two detectors in the same unit, the conventional small-window-width coincidence judging and selecting device cannot realize coincidence processing of any two detectors between different detector units.
Disclosure of Invention
The embodiment of the invention provides a coincidence judgment method, a coincidence judgment device, coincidence judgment equipment and coincidence judgment media, so that coincidence judgment of any two detectors in different detector units or in the same detector unit is realized.
In a first aspect, an embodiment of the present invention provides a coincidence judging and selecting method, where the method includes:
determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector;
determining the occurrence time difference of the first event and the second event according to the period difference, the TDC (time-to-digital converter) value of the first event and the TDC value of the second event;
and if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation.
In a second aspect, an embodiment of the present invention further provides a coincidence judging device, where the coincidence judging device includes:
the period difference determining module is used for determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector;
the time difference determining module is used for determining the occurrence time difference of the first event and the second event according to the period difference, the TDC time digital conversion value of the first event and the TDC value of the second event;
and the coincidence determination module is used for determining that the first event and the second event have coincidence relation if the time difference is smaller than a set time threshold.
In a third aspect, an embodiment of the present invention further provides an apparatus, where the apparatus includes:
one or more processors;
a storage device for storing one or more programs,
when executed by the one or more processors, cause the one or more processors to implement a coincidence determination method as in any one of the embodiments of the present invention.
In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements a coincidence determination method according to any one of the embodiments of the present invention.
According to the embodiment of the invention, the occurrence time difference of the first event and the second event is determined according to the cycle difference between the cycle of the occurrence time of the first event and the cycle of the occurrence time of the second event, the TDC value of the first event and the TDC value of the second event; and determining whether the two events have a coincidence relation according to the occurrence time difference. Therefore, coincidence judgment of any two detectors in the same detector unit can be realized, and coincidence judgment of any two detectors between different detector units can also be realized.
Drawings
FIG. 1 is a schematic diagram of the internal response lines of a single detector unit in a PET apparatus;
FIG. 2 is a schematic diagram of a cross-unit response line between two detector units in a PET apparatus;
FIG. 3 is a diagram of coincidence events occurring in the same clock cycle with an A event occurring first;
FIG. 4 is a diagram of coincidence events occurring in the same clock cycle with the B event occurring first;
FIG. 5 is a diagram of coincidence events occurring at different clock cycles and B events occurring one clock cycle before A events;
FIG. 6 is a diagram of coincidence events occurring at different clock cycles and an A event occurring one clock cycle before a B event;
FIG. 7 is a diagram of coincidence events occurring at different clock cycles and B events occurring two clock cycles before A events;
FIG. 8 is a diagram of coincidence events occurring at different clock cycles and an A event occurring two clock cycles before a B event;
fig. 9 is a flowchart of a coincidence determination method according to an embodiment of the present invention;
fig. 10 is a flowchart of a coincidence determination method according to a second embodiment of the present invention;
fig. 11 is a flowchart of a coincidence determination method according to a third embodiment of the present invention;
fig. 12 is a schematic structural diagram of a coincidence determination device according to a third embodiment of the present invention;
fig. 13 is a schematic structural diagram of a coincidence determination device according to a fourth embodiment of the present invention;
fig. 14 is a schematic structural diagram of an apparatus according to a fifth embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Referring to fig. 2, the inventors discovered in practicing the present invention that when multiple detector units are present in a PET apparatus, there is a line of response between the two detectors across the detector units, i.e., between detector M0 in detector unit U0 and detector M10 in detector unit U3. The possible time-of-flight difference of two photons is larger, since the line of response will be longer than between two detectors within the same detector unit. In order to discriminate such coincidence events, the coincidence processing device needs to have the capability of processing coincidence judgment with a large window width.
For this inventor to traverse all possible cases, the relationship between TDC _ A, TDC _ B and twinow was analyzed for each case as follows. The TDC _ a is a TDC quantization value of a time from a rising edge of the next clock cycle when a detector a event (hereinafter referred to as an a event) occurs, that is, a TDC value of the a event. TDC _ B is a TDC quantization value of a time from a rising edge of the next clock cycle when a detector B event (hereinafter referred to as a B event) occurs, that is, a TDC value of the B event. Twinow is the window width that is sized to set the time threshold, which is more than one clock cycle.
Fig. 3 shows that coincidence events occur on the same clock cycle, with event a occurring first by event B, the time of occurrence of both events and the TDC value. As can be seen from fig. 3, if the a event and the B event are coincidence events, Tab ═ TDC _ a-TDC _ B < twinow needs to be satisfied. Where Tab is the time-of-flight difference of the two events received by detector A and detector B.
Fig. 4 shows that coincidence events occur on the same clock cycle, with event B occurring first, event a, time of occurrence of both events and TDC values. As can be seen from fig. 4, if the a event and the B event are coincidence events, Tab is required to satisfy TDC _ B-TDC _ a < twinnow.
Referring to fig. 3 and 4, if two coincident events occur in the same clock cycle, the equation, | TDC _ a-TDC _ B | < twinnow, is also modified as follows: -Twinow < TDC _ A-TDC _ B < Twinow.
Fig. 5 shows that coincidence events occur at different clock cycles, and B occurs one clock cycle before a, the time of occurrence of the two events and the TDC value. If two events are coincident events, Tab is equal to TDC _ B + T-TDC _ A < Twindow, and the formula is transformed into TDC _ A-TDC _ B > -Twindow + T. Where T is the system synchronization clock period, taking 10ns as an example.
Fig. 6 shows that coincidence events occur at different clock cycles, with a event occurring one clock cycle before B event, the time of occurrence of the two events and the TDC value. If two events are coincident events, Tab is equal to TDC _ A + T-TDC _ B < Twindow, and the formula is transformed into TDC _ A-TDC _ B < -T + Twindow.
FIG. 7 shows that coincidence events occur at different clock cycles, and B occurs two clock cycles before A, the time of occurrence of the two events and the TDC value. If the two events are coincident events, Tab is equal to TDC _ B +2T-TDC _ A < Twinow, and the formula is transformed to TDC _ A-TDC _ B > 2T-Twinow.
FIG. 8 shows that coincidence events occur at different clock cycles, with the A event occurring two clock cycles before the B event, the time of occurrence of the two events and the TDC value. If the two events are coincidence events, Tab is equal to TDC _ A +2T-TDC _ B < Twinow, and the formula is transformed to TDC _ A-TDC _ B < Twinow-2T.
In summary, the following steps:
1. if the event a occurs in the next N clock cycles compared to the event B, where N is an integer, then if the two events are coincident events, it is required to satisfy Tab ═ TDC _ B + nxt-TDC _ a < twinnow, i.e. TDC _ a-TDC _ B > nxt-twinnow;
2. if the event B occurs in the next N clock cycles compared to the event a, where N is an integer, then if the two events are coincidence events, it is required to satisfy that Tab is TDC _ a + nxt-TDC _ B < twinnow, i.e., TDC _ a-TDC _ B < -nxt + twinnow;
and when N is 0, the A event and the B event are shown to occur in the same clock cycle.
The value of twinow is not limited, and can be arbitrarily large as required.
Example one
Fig. 9 is a flowchart of a coincidence determination method according to an embodiment of the present invention. The present embodiment is applicable to the case of coincidence judgment of any two detectors in different detector units or in the same detector unit. The method may be performed by a coincidence determination device, which may be implemented in software and/or hardware. Referring to fig. 9, the coincidence judging and selecting method provided by the embodiment includes:
s110, determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector.
Wherein the first event and the second event are events of receiving photons by two detectors to be coincidentally judged. And the detector to which the first event belongs and the detector to which the second event belongs may be located in the same detector unit or may be located in different detector units.
Specifically, the event occurrence period of the detector receiving the photon may be determined by the period to which the clock pulse of the system belongs at the time of the event occurrence.
And S120, determining the occurrence time difference of the first event and the second event according to the period difference, the TDC value of the first event and the TDC value of the second event.
Specifically, if the period difference is 0, which indicates that the first event and the second event are in the same period, the occurrence time difference between the first event and the second event is equal to the absolute value of the TDC value of the first event and the TDC value of the second event.
If the period difference is non-zero, it indicates that the first event and the second event are cross-period events, and the first event occurs before the second event, then the difference between the occurrence times of the first event and the second event is equal to the TDC value of the first event + the period difference x the clock period-the TDC value of the second event.
And S130, if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation.
The set time threshold is the maximum value of the difference between the occurrence times of two events having a coincidence relationship. If the set time threshold is regarded as a time window, the embodiment can be adapted to the coincidence judgment and selection of any large window width, and can be specifically set according to actual needs.
According to the technical scheme of the embodiment of the invention, the occurrence time difference of the first event and the second event is determined according to the cycle difference between the cycle of the occurrence time of the first event and the cycle of the occurrence time of the second event, the TDC value of the first event and the TDC value of the second event; and determining whether the two events have a coincidence relation according to the occurrence time difference. Therefore, coincidence judgment of any two detectors in the same detector unit can be realized, and coincidence judgment of any two detectors between different detector units can also be realized. For future PET equipment, no matter how many detector units are, the data coincidence judgment between any two units is applicable.
In order to implement processing of subsequent coincidence events, after determining that the first event and the second event have a coincidence relation if the time difference is smaller than a set time threshold, the method further includes:
and combining the time, energy and position information of the first event and the second event into one coincidence data and outputting the coincidence data.
It is emphasized that this embodiment is applicable to back-end processing, interfacing with the detector, and being implemented by hardware circuitry printed on a compliant circuit board. Compared with the method that the first event and the second event are output to the front end and the coincidence judgment is carried out by using the sliding window, the method saves the output of the first event and the second event, and therefore the real-time performance and the processing speed of the coincidence judgment are improved.
Example two
Fig. 10 is a flowchart of a coincidence determination method according to a second embodiment of the present invention. The present embodiment is an alternative proposed on the basis of the above-described embodiments. Referring to fig. 10, the coincidence judging and selecting method provided by the embodiment includes:
s210, determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector.
S220, determining the sequence of the occurrence time of the first event and the second event according to the period difference or the event occurrence period of the photon received by the detector.
Specifically, the sequence of the occurrence time of the first event and the occurrence time of the second event may be determined according to the positive and negative of the period difference, or may be determined according to the occurrence period of the first event and the occurrence period of the second event.
For example, if the first event occurs on a first clock cycle and the second event occurs on a second clock cycle, then it may be determined that the first event occurred before the second event.
And S230, determining a target time difference formula according to the determined sequence.
Specifically, the determining a target time difference formula according to the determined sequence includes:
if the first event occurs before the second event, determining that the target time period difference formula is: the TDC value of the first event + the absolute value of the period difference x the system synchronous clock period-the TDC value of the second event;
if the second event occurs before the first event, determining that the target time period difference formula is: TDC value of second event + absolute value of period difference x system synchronous clock period-TDC value of first event.
S240, substituting the cycle difference, the TDC value of the first event and the TDC value of the second event into the target time difference formula to obtain the occurrence time difference of the first event and the second event.
And S250, if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation.
According to the technical scheme of the embodiment of the invention, a target time difference formula is determined according to the sequence of the occurrence time of the first event and the second event, and the cycle difference, the TDC value of the first event and the TDC value of the second event are substituted into the target time difference formula to obtain the occurrence time difference of the first event and the second event. And if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation. Thereby realizing the coincidence judgment of the two events.
EXAMPLE III
Fig. 11 is a flowchart of a coincidence determination method according to a third embodiment of the present invention. The present embodiment is an alternative solution provided by taking, as an example, two events to be conformed to the judgment as an event a and an event B collected by the detector a and the detector B, respectively, on the basis of the above embodiments. Referring to fig. 11, the coincidence judging and selecting method provided by the embodiment includes:
and S310, determining the cycle difference of the occurrence time of the event A and the event B.
And S320, determining the occurrence sequence of the event A and the event B.
S330, calculating the difference value between the TDC value of the event A and the TDC value of the event B, and assigning to a signed register.
S340, if the event A occurs before the event B, selecting an inequality TDC _ A-TDC _ B < -NxT + Twindow, if the event B occurs before the event A, selecting an inequality TDC _ A-TDC _ B > NxT-Twindow, and performing coincidence judgment, wherein the TDC _ A is the TDC value of the event A, the TDC _ B is the TDC value of the event B, N is the period difference between the occurrence moments of the event A and the event B, T is the system clock period, and Twindow is a set time threshold.
S350, acquiring a difference value between the TDC value of the event A and the TDC value of the event B from the signed register, and determining whether the event A and the event B have a coincidence relation according to the difference value between the TDC value of the event A and the TDC value of the event B and the determined inequality; and combining the two single events with the coincidence relation into one data, and outputting the time, energy and position information of the two events with the coincidence relation.
The execution sequence of each step is not limited in the embodiment of the present invention. Alternatively, S340 may be performed prior to S330.
Referring to fig. 12, based on the coincidence judging and selecting method described in this embodiment, the coincidence device may include a sequence determining module, a difference making module, a coincidence inequality determining module, and a coincidence judging and coincidence outputting module.
The sequence module is used for determining the occurrence sequence of the events A and the events B; the difference making module is used for calculating the difference value between the TDC value of the event A and the TDC value of the event B and assigning the difference value to a signed register; the coincidence inequality determining module is used for selecting inequality TDC _ A-TDC _ B < -NxT + Twindow if the A event occurs before the B event, and selecting inequality TDC _ A-TDC _ B > NxT-Twindow if the B event occurs before the A event to perform coincidence judgment; the coincidence judging and coincidence outputting module is used for acquiring a difference value between the TDC value of the event A and the TDC value of the event B from the signed register, and determining whether the event A and the event B have a coincidence relation according to the difference value between the TDC value of the event A and the TDC value of the event B and the determined inequality; and combining the two single events with the coincidence relation into one data, and outputting the time, energy and position information of the two events with the coincidence relation.
The technical scheme of the embodiment can realize the following effects that the embodiment can adapt to the coincidence judgment and selection of any large window width, all window width situations are covered, and the difference of the window width values is a change example.
In addition, the embodiment can process coincidence judgment spanning any unit number, and is applicable to future PET equipment for judging data coincidence between any two units no matter how many detector units are.
It should be noted that, based on the technical teaching of the above embodiments, a person skilled in the art may have an incentive to combine the above embodiments to achieve coincidence determination between any two detectors in different detector units or in the same detector unit.
Example four
Fig. 13 is a schematic structural diagram of a coincidence determination device according to a fourth embodiment of the present invention. Referring to fig. 13, the coincidence judging and selecting device provided in this embodiment includes: a cycle difference determination module 10, a time difference determination module 20, a coincidence determination module 30.
The period difference determining module 10 is configured to determine a period difference between a period in which a first event occurs and a period in which a second event occurs according to an event occurrence period in which the detector receives photons;
a time difference determining module 20, configured to determine a time difference between a first event and a second event according to the period difference, a TDC time-to-digital conversion value of the first event, and a TDC value of the second event;
and a coincidence determination module 30, configured to determine that the first event and the second event have a coincidence relation if the time difference is smaller than a set time threshold.
According to the embodiment of the invention, the occurrence time difference of the first event and the second event is determined according to the cycle difference between the cycle of the occurrence time of the first event and the cycle of the occurrence time of the second event, the TDC value of the first event and the TDC value of the second event; and determining whether the two events have a coincidence relation according to the occurrence time difference. Therefore, coincidence judgment of any two detectors in the same detector unit can be realized, and coincidence judgment of any two detectors between different detector units can also be realized.
Further, the time difference determination module includes: the device comprises an occurrence order determining unit, a target formula determining unit and a time difference determining unit.
The occurrence sequence determining unit is used for determining the sequence of the occurrence time of the first event and the occurrence time of the second event according to the period difference or the event occurrence period of the photons received by the detector;
the target formula determining unit is used for determining a target time difference formula according to the determined sequence;
and the time difference determining unit is used for substituting the cycle difference, the TDC value of the first event and the TDC value of the second event into the target time difference formula to obtain the occurrence time difference of the first event and the second event.
Further, the target formula determining unit is specifically configured to:
if the first event occurs before the second event, determining that the target time period difference formula is: the TDC value of the first event + the absolute value of the period difference x the system synchronous clock period-the TDC value of the second event;
if the second event occurs before the first event, determining that the target time period difference formula is: TDC value of second event + absolute value of period difference x system synchronous clock period-TDC value of first event.
Further, the device further comprises: the device comprises a data merging module and a coincidence data output module.
The data merging module is used for merging the time, energy and position information of the first event and the second event into a coincidence data after the first event and the second event are determined to have a coincidence relation if the time difference is smaller than a set time threshold;
and the coincidence data output module is used for outputting the coincidence data.
The coincidence judging and selecting device provided by the embodiment of the invention can execute the coincidence judging and selecting method provided by any embodiment of the invention, and has corresponding functional modules and beneficial effects of the execution method.
EXAMPLE five
Fig. 14 is a schematic structural diagram of an apparatus according to a fifth embodiment of the present invention. As shown in fig. 14, the apparatus includes a processor 70, a memory 71, an input device 72, and an output device 73; the number of processors 70 in the device may be one or more, and one processor 70 is taken as an example in fig. 14; the processor 70, the memory 71, the input device 72 and the output device 73 in the apparatus may be connected by a bus or other means, and the connection by a bus is exemplified in fig. 14.
The memory 71 is a computer-readable storage medium, and can be used for storing software programs, computer-executable programs, and modules, such as program instructions/modules corresponding to the coincidence determination method in the embodiment of the present invention (for example, the cycle difference determination module 10, the time difference determination module 20, and the coincidence determination module 30 in the coincidence determination device). The processor 70 executes various functional applications of the device and data processing by executing software programs, instructions and modules stored in the memory 71, that is, implements the above-described coincidence determination method.
The memory 71 may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created according to the use of the terminal, and the like. Further, the memory 71 may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some examples, the memory 71 may further include memory located remotely from the processor 70, which may be connected to the device over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The input device 72 may be used to receive entered numeric or character information and to generate key signal inputs relating to user settings and function controls of the apparatus. The output device 73 may include a display device such as a display screen.
EXAMPLE six
An embodiment of the present invention further provides a storage medium containing computer-executable instructions, which when executed by a computer processor, are configured to perform a coincidence decision method, including:
determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector;
determining the occurrence time difference of the first event and the second event according to the period difference, the TDC time-to-digital conversion value of the first event and the TDC value of the second event;
if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation
Of course, the storage medium provided by the embodiment of the present invention contains computer-executable instructions, and the computer-executable instructions are not limited to the operations of the method described above, and may also perform related operations in the coincidence determination method provided by any embodiment of the present invention.
From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software and necessary general hardware, and certainly, can also be implemented by hardware, but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention or portions thereof contributing to the prior art may be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a floppy disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a FLASH Memory (FLASH), a hard disk or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods according to the embodiments of the present invention.
It should be noted that, in the embodiment of the coincidence judging and selecting apparatus, the included units and modules are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be realized; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (10)

1. A coincidence judgment and selection method is characterized by comprising the following steps:
determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector; the detector of the first event and the detector of the second event are different detector units;
determining the occurrence time difference of the first event and the second event according to the period difference, the TDC time-to-digital conversion value of the first event and the TDC value of the second event;
if the time difference is smaller than a set time threshold, determining that the first event and the second event have a coincidence relation; the set time threshold is the maximum value of the difference between the occurrence times of two events having a coincidence relationship.
2. The method of claim 1, wherein determining the difference between the occurrence times of the first event and the second event according to the period difference, the TDC value of the first event and the TDC value of the second event comprises:
determining the sequence of the occurrence time of the first event and the second event according to the period difference or the event occurrence period of the photon received by the detector;
determining a target time difference formula according to the determined sequence;
and substituting the period difference, the TDC value of the first event and the TDC value of the second event into the target time difference formula to obtain the occurrence time difference of the first event and the second event.
3. The method of claim 2, wherein determining a target time difference formula according to the determined precedence order comprises:
if the first event occurs before the second event, determining that the target time period difference formula is: the TDC value of the first event + the absolute value of the period difference x the system synchronous clock period-the TDC value of the second event;
if the second event occurs before the first event, determining that the target time period difference formula is: TDC value of second event + absolute value of period difference x system synchronous clock period-TDC value of first event.
4. The method according to any one of claims 1-3, wherein after determining that the first event and the second event have a coincidence relationship if the time difference is smaller than a set time threshold, further comprising:
and combining the time, energy and position information of the first event and the second event into one coincidence data and outputting the coincidence data.
5. A coincidence decision device, comprising:
the period difference determining module is used for determining the period difference between the period of the first event and the period of the second event according to the event occurrence period of the photon received by the detector; the detector of the first event and the detector of the second event are different detector units;
the time difference determining module is used for determining the occurrence time difference of the first event and the second event according to the period difference, the TDC time digital conversion value of the first event and the TDC value of the second event;
the coincidence determination module is used for determining that the first event and the second event have coincidence relation if the time difference is smaller than a set time threshold; the set time threshold is the maximum value of the difference between the occurrence times of two events having a coincidence relationship.
6. The apparatus of claim 5, wherein the time difference determining module comprises:
the occurrence sequence determining unit is used for determining the sequence of the occurrence time of the first event and the second event according to the period difference or the event occurrence period of the photon received by the detector;
the target formula determining unit is used for determining a target time difference formula according to the determined sequence;
and the time difference determining unit is used for substituting the cycle difference, the TDC value of the first event and the TDC value of the second event into the target time difference formula to obtain the occurrence time difference of the first event and the second event.
7. The apparatus according to claim 6, wherein the target formula determination unit is specifically configured to:
if the first event occurs before the second event, determining that the target time period difference formula is: the TDC value of the first event + the absolute value of the period difference x the system synchronous clock period-the TDC value of the second event;
if the second event occurs before the first event, determining that the target time period difference formula is: TDC value of second event + absolute value of period difference x system synchronous clock period-TDC value of first event.
8. The apparatus of any of claims 5-7, further comprising:
the data merging module is used for merging the time, energy and position information of the first event and the second event into a coincidence data after the first event and the second event are determined to have a coincidence relation if the time difference is smaller than a set time threshold;
and the coincidence data output module is used for outputting the coincidence data.
9. An apparatus, characterized in that the apparatus comprises:
one or more processors;
a storage device to store one or more programs,
when executed by the one or more processors, cause the one or more processors to implement a method of compliance determination as claimed in any one of claims 1-4.
10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out a coincidence decision method according to any one of claims 1-4.
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PCT/CN2020/084861 WO2020211764A1 (en) 2019-04-15 2020-04-15 Systems and methods for determining true coincidence events
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