Time correction method and device, computer storage medium and digital PET system

Abstract

The invention discloses a time correction method and device, a computer storage medium and a digital PET system. The time correction method comprises the following steps: step S100, carrying out in-ring time correction on crystal strips of a plurality of detection rings in sequence to obtain in-ring time correction values of all the crystal strips; s200, all coincidence events between every two adjacent detection rings are obtained in sequence, and the event arrival time of each coincidence event on the crystal strip is obtained; and S300, carrying out inter-ring time correction on the plurality of detection rings according to the position of the current to-be-calibrated ring, the in-ring time correction value and the average value or weighted value of the difference value of the arrival time of the two single events of each coincidence event. According to the invention, the overall time correction quality of the digital PET system can be improved, the image quality can be improved, the radiation dose can be reduced, and the inter-ring time correction of the long-axis PET can be realized at the cost as low as possible.

Description

Technical Field

[0001] This invention relates to the field of data processing, and in particular to a time correction method, apparatus, computer storage medium, computer program product, and digital PET system for long-axis PET. Background Technology

[0002] Positron emission tomography (PET) is one of the most advanced molecular imaging technologies available today. It reconstructs images by detecting coincidence events corresponding to the annihilation of positive and negative electrons within the object being measured.

[0003] As detection demands continue to expand, higher requirements are being placed on the axial length of PET sensors. To extend the axial detection length of PET detection systems, multiple detection rings are typically arranged axially. Each detection ring includes multiple detectors, and each detector comprises multiple crystal strips. Differences in detector hardware, such as optical propagation deviations, circuit propagation deviations, and reference clock skew, result in a time difference between the time a gamma photon hits the detector and the actual time the pulse signal is received. To obtain as many coincidence events as possible, the time difference caused by hardware differences needs to be corrected to the same level, achieving intra-ring time correction. Furthermore, the clock line synchronization accuracy of the clock boards of detectors in different detection rings is inconsistent. On top of the existing hardware differences, there is an additional time difference between the data from different detection rings, requiring inter-ring time correction.

[0004] Generally, on a single-ring PET, a line source can be used as the basis for data acquisition during time correction. However, the length of the line source is shorter than the axial length of the PET, making it difficult to match with the axial length of the PET. Custom-length line sources are also expensive. Therefore, considering cost, it is difficult to perform inter-ring time correction. Without inter-ring time correction, there will be a significant loss of coincidence events between different rings, which will affect the system sensitivity and imaging effect. Summary of the Invention

[0005] Therefore, it is necessary to provide a time correction method, apparatus, computer storage medium, computer program product, and digital PET system to address at least one technical problem existing in traditional solutions.

[0006] According to a first aspect of this application, a time correction method is provided, comprising: step S100: sequentially performing intra-ring time correction on the crystal strips of a plurality of probe rings to obtain intra-ring time correction values ​​for all crystal strips; step S200: sequentially acquiring all coincidence events between pairs of adjacent probe rings, and acquiring the single-event arrival time of each coincidence event on the crystal strip; step S300: performing inter-ring time correction on the plurality of probe rings based on the current position of the ring to be calibrated, the intra-ring time correction value, and the average or weighted value of the difference between the two single-event arrival times of each coincidence event.

[0007] According to one embodiment of this application, step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the average of the differences between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0008] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, step S300 includes: obtaining the average value of the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, and adding the average value to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0009] According to one embodiment of this application, if there are one or more other probe rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining the average value of the difference between the first arrival time and the second arrival time at both ends of all response lines of the one or more other probe rings, and obtaining the average value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and summing all the average values ​​to the intra-ring time correction value of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0010] According to one embodiment of this application, step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0011] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, step S300 includes: obtaining the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, assigning weights to all differences to obtain a weighted value, and adding the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain an inter-ring time correction value.

[0012] According to one embodiment of this application, if there are one or more other probe rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining a weighted value of the difference between the first arrival time and the second arrival time of all coincidence events of the one or more other probe rings, and obtaining a weighted value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and summing all weighted values ​​to the intra-ring time correction value of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0013] According to one embodiment of this application, step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the average of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0014] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, step S300 includes: obtaining the average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, and adding the average value to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0015] According to one embodiment of this application, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining the average of the difference between the first arrival time and the second arrival time and the photon flight time at both ends of all response lines of the one or more other detection rings, and obtaining the average of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and summing all the average values ​​to the intra-ring time correction values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction values ​​of each crystal strip.

[0016] According to one embodiment of this application, step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated.

[0017] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, step S300 includes: obtaining the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, assigning weights to all differences to obtain a weighted value, and adding the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

[0018] According to one embodiment of this application, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events of the one or more other detection rings, and obtaining a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence events deposited by the crystal strip to be calibrated; and summing all weighted values ​​to the intra-ring time correction values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction values ​​of each crystal strip.

[0019] According to one embodiment of this application, inter-ring time correction is performed using the first probe ring as a reference ring and the second probe ring as the ring to be corrected. Then, inter-ring time correction is performed sequentially using the previous probe ring as the reference ring and the next probe ring as the ring to be corrected.

[0020] According to one embodiment of this application, inter-ring time correction is performed using any probe ring as a reference ring and the probe rings adjacent to it on one or both sides as the rings to be corrected. When there are uncorrected probe rings on one or both sides of the corrected probe ring, inter-ring time correction is performed using the corrected probe ring as the reference ring and the uncorrected probe rings as the rings to be corrected.

[0021] According to one embodiment of this application, step S200 includes: filtering coincident events, removing response lines whose two ends are in the same detection loop and response lines that have not passed through the source, and obtaining the single-event arrival time of the remaining coincident events on the crystal strip.

[0022] According to one embodiment of this application, both steps S100 and S200 involve acquiring data from the line source detection to calculate the in-loop time correction value and obtain the single event arrival time.

[0023] According to one embodiment of this application, in step S100, the wire source is placed sequentially within the detection field of each detection ring; in step S200, the wire source is placed sequentially between two adjacent detection rings, and the two ends of the wire source are respectively located within a portion of the detection field of the two detection rings.

[0024] According to one embodiment of this application, the arrangement direction of the line source is parallel to the axis of the detection ring.

[0025] According to one embodiment of this application, the arrangement direction of the line source coincides with the axis of the detection ring.

[0026] According to a second aspect of this application, a time correction device is provided, comprising: an intra-loop correction module configured to sequentially perform intra-loop time correction on the crystal strips of a plurality of detector rings to obtain intra-loop time correction values ​​for all crystal strips; a data acquisition module configured to sequentially acquire all coincidence events between pairs of adjacent detector rings and acquire the single-event arrival time of each coincidence event on the crystal strip; and an inter-loop correction module configured to perform inter-loop time correction on the plurality of detector rings based on the position of the current detector ring to be calibrated, the intra-loop time correction values, and the average or weighted value of the difference between the two single-event arrival times of each coincidence event.

[0027] According to one embodiment of this application, the data acquisition module is configured to: sequentially acquire all coincidence events between pairs of adjacent detector rings, select one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the average of the differences between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0028] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module is configured to: obtain the average value of the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, and add the average value to the intra-ring time calibration value of each crystal strip of the ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0029] According to one embodiment of this application, if there are one or more other probe rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured to: obtain the average value of the difference between the first arrival time and the second arrival time at both ends of all response lines of the one or more other probe rings, and obtain the average value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and accumulate all the average values ​​to the intra-ring time calibration values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0030] According to one embodiment of this application, the data acquisition module is configured to: sequentially acquire all coincidence events between pairs of adjacent detector rings, select one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0031] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module is configured to: obtain the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time calibration value of all crystal strips of the ring to be calibrated to obtain the inter-ring time calibration value.

[0032] According to one embodiment of this application, if there are one or more other probe rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured to: obtain a weighted value of the difference between the first arrival time and the second arrival time of all coincidence events of the one or more other probe rings, and obtain a weighted value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and accumulate all weighted values ​​to the intra-ring time calibration values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0033] According to one embodiment of this application, the data acquisition module is configured to: sequentially acquire all coincidence events between pairs of adjacent detector rings, select one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the average of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0034] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module is configured to: obtain the average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, and add the average value to the intra-ring time calibration value of each crystal strip of the ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0035] According to one embodiment of this application, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured to: obtain the average value of the difference between the first arrival time and the second arrival time and the photon flight time at both ends of all response lines of the one or more other detection rings, and obtain the average value of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and sum all the average values ​​to the intra-ring time calibration value of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0036] According to one embodiment of this application, the data acquisition module is configured to: sequentially acquire all coincidence events between pairs of adjacent detector rings, select one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0037] According to one embodiment of this application, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module is configured to: obtain the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time calibration value of all crystal strips of the ring to be calibrated to obtain the inter-ring time calibration value.

[0038] According to one embodiment of this application, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured to: obtain a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events of the one or more other detection rings, and obtain a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence events deposited by the crystal strip to be calibrated; and sum all the weighted values ​​to the intra-ring time calibration values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0039] According to one embodiment of this application, the data acquisition module is configured to: filter coincident events, remove response lines whose two ends are in the same detection loop and response lines that have not passed through the source, and obtain the single-event arrival time of the remaining coincident events on the crystal strip.

[0040] According to a third aspect of this application, a computer storage medium is provided that stores a computer program thereon, which, when executed by a processor, implements the steps of the time correction method described above.

[0041] According to a fourth aspect of this application, a computer program product is provided, comprising a computer program or instructions that, when executed by a processor, implement the steps of the time correction method.

[0042] According to a fifth aspect of this application, a digital PET system is provided, which uses the aforementioned time correction device for time correction.

[0043] The time correction method, apparatus, computer storage medium, computer program product, and digital PET system provided in this application first perform intra-loop time correction, and then perform inter-loop time correction on each detector ring by acquiring the single-event arrival time of inter-loop coincidence events and combining the single-event arrival time and intra-loop time correction value. Since the length of existing line sources can basically cover a single detector ring, it provides a basis for acquiring inter-loop coincidence events. By combining inter-loop coincidence event information, inter-loop time correction can be made not limited by the length of the line source, thereby improving the overall time correction quality of the digital PET system, which is beneficial to improving image quality, reducing radiation dose, and achieving inter-loop time correction of long-axis PET at the lowest possible cost. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0045] Figure 1 This is a flowchart illustrating the time correction method in one embodiment of this application; Figure 2 This is a side view of the long-axis PET structure in one embodiment of this application; Figure 3 This is an axial cross-sectional schematic diagram of in-ring time correction of the long-axis PET in one embodiment of this application; Figure 4 This is an axial cross-sectional schematic diagram of inter-ring time correction of the long-axis PET in one embodiment of this application; Figure 5 This is a schematic diagram showing the line source located at the axial center of the long axis PET in one embodiment of this application; Figure 6 This is a schematic diagram of the time correction device in one embodiment of this application; Figure 7 This is a schematic diagram of the time correction system in one embodiment of this application; Figure 8 This is an internal structural diagram of a computer device in one embodiment of this application. Detailed Implementation

[0046] To make the above-mentioned objectives, features, and advantages of this application more readily understood, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0047] It should be noted that when an element is said to be "fixed to" another element, it can be directly fixed to the other element or there may be an intervening element. When an element is said to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "substantially equal" or "substantially equal to" as used herein mean that the difference between the two lies within a range of errors considered equivalent in the art. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The terms “and / or” or “and / or” as used herein include any and all combinations of one or more of the associated listed items.

[0049] To address the technical problems existing in the prior art, this application proposes a method, apparatus, and supporting applications for at least intra-ring and inter-ring time correction of long-axis PET.

[0050] In some embodiments, the time correction method can be executed by a time correction device. For example, the time correction method can be partially or wholly stored in a storage device (such as the built-in storage module of the detection device or an external storage device) in the form of a program or instructions, which can implement the time correction method when executed. The time correction device disclosed in this application for implementing the above-described time correction method can be a device with a large amount of computing resources (e.g., a computer, server, cloud computing, etc.) or a device with limited computing resources (e.g., FPGA (Field Programmable Gate Array) chip board, ASIC (Application-Specific Integrated Circuit) chip board, and other hardware circuits).

[0051] The following description, with reference to the accompanying drawings, illustrates some preferred embodiments of the present application. It should be noted that the following description is for illustrative purposes only and is not intended to limit the scope of protection of this application.

[0052] Figure 1 This is a flowchart illustrating a time correction method in one embodiment of the present application. In one embodiment, the time correction method may include the following steps S100~S300.

[0053] Step S100: Perform in-loop time correction on the crystal strips of the multiple detection rings in sequence to obtain the in-loop time correction values ​​of all crystal strips.

[0054] For example, Table 1 below shows the in-ring time correction values ​​for a portion of the crystal strips of a long-axis PET.

[0055] Table 1 Detector IP Position numbering of crystal bars In-loop time correction value 1 0 0 1 1 1.3677 1 2 -0.1811 1 3 -0.3117 1 4 0.6687 1 5 0.7282 1 6 0.4889 Understandably, in actual calibration, a long-axis PET will have several in-loop time correction values. Taking the crystal strip with detector IP of 1 and crystal strip position number of 0 as the reference, its in-loop time correction value is 0. The in-loop correction values ​​of other crystal strips are the values ​​in the table with 0 as the reference. When performing in-loop time correction, the time correction is performed directly using the in-loop time correction value.

[0056] In this application, the long-axis PET includes multiple detection rings arranged coaxially. For example, one long-axis PET includes two detection rings, and another long-axis PET includes four detection rings 100 (see...). Figure 2 Each detection ring includes 12, 24, or 48 detectors, each detector comprising an 8×8 or 12×12 crystal bar array, and each detector also includes optoelectronic devices and circuitry. Of course, those skilled in the art will understand that the number of detection rings, detectors, and crystal bars can all be expanded.

[0057] Specifically, in one example of this application, see [link to example]. Figure 3 Data is collected by placing the line source 200 sequentially within the field of view of each detection ring 100. The time of each crystal strip is corrected based on the collected data to obtain the time correction value within the ring for each crystal strip. It should be noted that, due to hardware limitations, the time correction values ​​within the ring for each crystal strip are generally not exactly the same.

[0058] Preferably, the wire source is arranged parallel to the axis of the detection ring, and more preferably, the wire source is arranged to coincide with the axis of the detection ring.

[0059] Preferably, the length of the line source is substantially the same as, or slightly greater than, the axial length of a single probe ring, for example, substantially the same as the sum of the lengths of a single probe ring and the gaps on both sides thereof.

[0060] Optionally, the intra-loop time correction of each detection ring can be performed using existing time correction methods, such as the method described in CN202211731787.X. Of course, those skilled in the art will understand that other existing methods capable of achieving intra-loop time correction can also be used.

[0061] Step S200: Sequentially acquire all coincidence events between two adjacent detector rings, and acquire the single-event arrival time of each coincidence event on the crystal strip.

[0062] Taking the aforementioned line source as the basis for data acquisition as an example, when acquiring all coincidence events between two adjacent probe rings, the line source 200 is placed between two adjacent probe rings 100 (see...). Figure 4 Furthermore, it is required that both ends of the line source 200 enter the detection field of view of the two detection rings 100 respectively to ensure that enough data is collected. Preferably, the length of the line source within the field of view of the two detection rings is the same.

[0063] The step of sequentially acquiring all coincidence events between pairs of adjacent probe rings can be done according to the arrangement order of the probe rings, according to user preference, or by sequentially acquiring events around a selected first reference ring. Generally, the selected first reference ring offers the best performance. For example, when acquiring events sequentially according to the arrangement order of the probe rings, acquiring all coincidence events between pairs of adjacent probe rings means sequentially acquiring all first coincidence events between the first and second probe rings, all second coincidence events between the second and third probe rings, and all (N-1)th coincidence events between the (N-1)th and Nth probe rings. All first coincidence events form one data packet, all second coincidence events also form one data packet, and so on for other coincidence events. Each data packet is processed individually.

[0064] Preferably, in order to reduce the amount of data and optimize the data processing speed, in one example of this application, step S200 includes: The coincidence events are filtered out, and response lines whose two ends are in the same detection loop and response lines that have not passed through the source are removed. The single-event arrival time of the remaining coincidence events on the crystal strip is obtained.

[0065] Since the purpose of step S200 is to collect data for inter-ring event coincidence, only coincidence events occurring between rings are needed. This is reflected in the response line by the two ends of the response line being on two different detection rings. In addition, events that have not passed through the source are generally considered invalid events and should also be discarded.

[0066] Step S300: Perform inter-ring time correction on the multiple detection rings based on the intra-ring time correction value and the single event arrival time.

[0067] Specifically, in this application, there are multiple ways to perform inter-ring time correction. Different methods are used for correction depending on whether the axis of the line source coincides with the axis of the long-axis PET. Different methods are used for correction depending on the correction standard. For example, after correction, all detectors in each detection ring share a correction value, or after correction, all crystal strips in each detector share a correction value, or a single crystal strip uses a single correction value. Different methods are also used for correction depending on the positional relationship between the ring to be corrected and the first reference ring.

[0068] For example, in one example of this application, the axis of the line source coincides with the axis of the long axis PET, and the same calibration data is used for the same probe ring. Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent probe rings, selecting one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated.

[0069] Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the average of the differences between the first arrival time and the second arrival time of all coincident events on the current ring to be calibrated.

[0070] Specifically, if the ring to be corrected is adjacent to the first reference ring, then step S300 includes: The average of the differences between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated is obtained, and the average value is added to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0071] Specifically, if there are one or more other probe rings between the current ring to be calibrated and the first reference ring, then step S300 includes: The average of the differences between the first arrival time and the second arrival time at both ends of all response lines of the one or more other probe rings is obtained, and the average of the differences between the first arrival time and the second arrival time corresponding to the coincidence event of the current crystal strip deposition to be corrected is obtained. The inter-ring time correction value of each crystal strip is obtained by summing all the average values ​​and adding them to the intra-ring time correction values ​​of all crystal strips in the current ring to be corrected.

[0072] As a specific example of the above example, taking the first probe ring as the first reference ring and the second probe ring as the ring to be calibrated, the line source is placed between the first and second probe rings. Response lines are obtained with their two ends on the first and second probe rings respectively. For each response line, its first arrival time and second arrival time are obtained. The first arrival time is subtracted from the second arrival time to obtain the first difference. The first differences corresponding to all response lines are obtained. The first average value is taken from all the first differences. This first average value is the calibration data of the current ring to be calibrated. The first average value is added to the intra-ring time correction value of the corresponding crystal strip on the second probe ring to obtain the inter-ring time correction value. The second calibration is based on the first... The second probe ring serves as the reference ring, and the third probe ring is the ring to be calibrated. The line source is placed between the second and third probe rings, and response lines with their two ends on the second and third probe rings are acquired. For each response line, its first arrival time and second arrival time are acquired. The second arrival time is subtracted from the first arrival time to obtain the second difference. The second difference corresponding to all response lines is acquired, and the second average value is taken for all the second differences. The first average value and the second average value are added to the intra-ring time correction value of all crystal strips in the third probe ring to obtain the inter-ring time correction value of each crystal strip. The same operation is performed on all crystal strips of all rings to be calibrated to perform inter-ring time correction on all crystal strips.

[0073] For example, in one example of this application, the axis of the line source coincides with the axis of the long-axis PET, and the same calibration data is used for the same probe ring. Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent probe rings, selecting one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0074] Specifically, if the ring to be corrected is adjacent to the first reference ring, then step S300 includes: Obtain the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

[0075] Specifically, if there are one or more other probe rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining a weighted value of the difference between the first arrival time and the second arrival time of all coincidence events of the one or more other probe rings, and obtaining a weighted value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and summing all the weighted values ​​to the intra-ring time correction value of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0076] As a specific example of the above example, taking the first probe ring as the first reference ring and the second probe ring as the ring to be calibrated, a line source is placed between the first and second probe rings. Response lines are obtained with their two ends on the first and second probe rings respectively. For each response line, its first arrival time and second arrival time are obtained. The first arrival time is subtracted from the second arrival time to obtain a first difference. The first differences corresponding to all response lines are obtained. Weights are assigned to all first differences to obtain a first weighted value. This first weighted value is the calibration data of the current ring to be calibrated. The first weighted value is added to the intra-ring time correction value of the corresponding crystal strip on the second probe ring to obtain the inter-ring time correction value. The second calibration is based on the first... The second probe ring serves as the reference ring, and the third probe ring is the ring to be calibrated. A line source is placed between the second and third probe rings, acquiring response lines at both ends on the second and third probe rings respectively. For each response line, its first and second arrival times are obtained. The second difference is obtained by subtracting the second arrival time from the first arrival time. The second differences for all response lines are then calculated, and weights are assigned to all second differences to obtain a second weighted value. This first and second weighted values ​​are added to the intra-ring time correction value of all crystal strips in the third probe ring to obtain the inter-ring time correction value for each crystal strip. The same operation is performed on all crystal strips in all rings to be calibrated to perform inter-ring time correction. Note that the weights assigned to different differences can be the same or different for different probe rings.

[0077] It is important to note that because the axis of the line source does not coincide with the long axis of the PET, photon time of flight must be considered during calibration for greater accuracy. In actual calibration, due to the randomness of operator actions, it is difficult to position the line source so that its axis is perfectly aligned with the long axis of the PET. Therefore, it is generally preferable to consider photon time of flight during calibration.

[0078] For example, in one example of this application, the axis of the line source does not coincide with the long axis PET axis, and the same calibration data is used for the same probe ring. Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent probe rings, selecting one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated, and acquiring the photon flight time corresponding to the coincidence event. Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the average of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0079] Specifically, if the current ring to be calibrated is adjacent to the first reference ring, step S300 includes: obtaining the average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, and adding the average value to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0080] Specifically, if there are one or more other detector rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining the average of the difference between the first arrival time and the second arrival time and the photon flight time at both ends of all response lines of the one or more other detector rings, and obtaining the average of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and summing all the average values ​​to the intra-ring time correction value of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

[0081] As a specific example of the above example, taking the first detector ring as the first reference ring and the second detector ring as the ring to be calibrated, the line source is placed between the first and second detector rings. Response lines are obtained with their two ends on the first and second detector rings respectively. For each response line, its first arrival time, second arrival time, and photon flight time are obtained. The first difference is obtained by subtracting the second arrival time and photon flight time from the first arrival time. The first difference is obtained for all response lines. The first average value is taken for all first differences, and this first average value is the calibration data for the current ring to be calibrated. The first average value is added to the intra-ring time correction value of the corresponding crystal strip on the second detector ring to obtain the inter-ring time correction value. The second calibration is based on the first... The second detector ring serves as the reference ring, and the third detector ring is the ring to be calibrated. The line source is placed between the second and third detector rings, and response lines are acquired at both ends on the second and third detector rings, respectively. For each response line, its first arrival time, second arrival time, and photon flight time are acquired. The second arrival time is subtracted from the first arrival time to obtain the second difference. The second difference corresponding to all response lines is acquired, and the second average value is taken for all the second differences. The first average value and the second average value are added to the intra-ring time correction value of all crystal strips in the third detector ring to obtain the inter-ring time correction value of each crystal strip. The same operation is performed on all crystal strips of all rings to be calibrated to perform inter-ring time correction on all crystal strips.

[0082] For example, in one example of this application, the axis of the line source does not coincide with the long axis PET axis, and the same calibration data is used for the same probe ring. Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent probe rings, selecting one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated, and acquiring the photon flight time corresponding to the coincidence event. Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0083] Specifically, if the current ring to be calibrated is adjacent to the first reference ring, then step S300 includes: obtaining the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, assigning weights to all differences to obtain a weighted value, and adding the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

[0084] Specifically, if there are one or more other detector rings between the current ring to be calibrated and the first reference ring, step S300 includes: obtaining a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events of the one or more other detector rings, and obtaining a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence events deposited by the current crystal strip to be calibrated. All weighted values ​​are then added to the intra-ring time correction values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time correction values ​​of each crystal strip.

[0085] As a specific example of the above example, taking the first detector ring as the first reference ring and the second detector ring as the ring to be calibrated, a line source is placed between the first and second detector rings. Response lines are obtained with their two ends on the first and second detector rings respectively. For each response line, its first arrival time, second arrival time, and photon flight time are obtained. The first difference is obtained by subtracting the second arrival time and photon flight time from the first arrival time. The first difference is obtained for all response lines. A weight is assigned to all first differences to obtain a first weighted value. This first weighted value is the calibration data for the current ring to be calibrated. The first weighted value is added to the intra-ring time correction value of the corresponding crystal strip on the second detector ring to obtain the inter-ring time correction value. The second calibration is performed with the first... The second detector ring serves as the reference ring, and the third detector ring is the ring to be calibrated. A line source is placed between the second and third detector rings, and response lines are acquired at both ends on the second and third detector rings, respectively. For each response line, its first arrival time, second arrival time, and photon flight time are obtained. The second arrival time is subtracted from the first arrival time to obtain the second difference. The second differences for all response lines are obtained, and weights are assigned to all second differences to obtain a second weighted value. The first and second weighted values ​​are added to the intra-ring time correction values ​​of all crystal strips in the third detector ring to obtain the inter-ring time correction values ​​for each crystal strip. The same operation is performed on all crystal strips in all rings to be calibrated to perform inter-ring time correction on all crystal strips. Note that the weights assigned to different differences can be the same or different for different detector rings.

[0086] Furthermore, unlike all the examples above, this application can also use a non-end probe ring as the first reference ring. For example, if the second probe ring is used as the reference ring, then the inter-ring time correction can be performed on the other probe rings sequentially to both sides according to the steps in the examples above.

[0087] The time correction method provided in this application first performs intra-loop time correction, and then performs inter-loop time correction by acquiring the single-event arrival time of inter-loop coincidence events and combining the single-event arrival time and intra-loop time correction value. Since the length of the existing line source can basically cover a single detector ring, it provides a basis for acquiring inter-loop coincidence events. By combining the inter-loop coincidence event information, the inter-loop time correction can be made not limited by the length of the line source, thereby improving the overall time correction quality of the digital PET system, which is beneficial to improving image quality, reducing radiation dose, and achieving inter-loop time correction of long-axis PET at the lowest possible cost.

[0088] Furthermore, by collecting photon flight time, the accuracy of inter-loop time correction can be further improved, and the precision requirements of the detection process can be reduced.

[0089] Based on the description of the above time correction method embodiments, this application also provides a time correction apparatus. The apparatus may include devices (including distributed systems), software (applications), modules, components, servers, clients, etc., that use the methods described in the embodiments of this specification, combined with necessary hardware implementations. Based on the same innovative concept, the apparatuses in one or more embodiments provided in this application are as described in the following embodiments. Since the implementation schemes and methods for solving the problem are similar, the implementation of specific apparatuses in the embodiments of this specification can refer to the implementation of the foregoing methods, and repeated details will not be repeated. As used below, the terms "module" or "module group" can refer to a combination of software and / or hardware that implements a predetermined function. Although the apparatuses described in the following embodiments are preferably implemented in software, hardware implementations, or a combination of software and hardware, are also possible.

[0090] Figure 6 This is a schematic diagram of the time correction device in one embodiment of the present application. In one embodiment, the time correction device 700 may include an intra-loop correction module 710, a data acquisition module 720, and an inter-loop correction module 730. The intra-loop correction module 710 is configured to sequentially perform intra-loop time correction on the crystal strips of multiple detector rings to obtain intra-loop time correction values ​​for all crystal strips. The data acquisition module 720 is configured to sequentially acquire all coincidence events between any two adjacent detector rings and acquire the single-event arrival time of each coincidence event on the crystal strip. The inter-loop correction module 730 is configured to perform inter-loop time correction on the multiple detector rings based on the current position of the ring to be calibrated, the intra-loop time correction value, and the average or weighted value of the difference between the two single-event arrival times of each coincidence event.

[0091] The long-axis PET includes multiple detection rings arranged coaxially. For example, one long-axis PET includes two detection rings, and another includes four. Each detection ring includes 12, 24, or 48 detectors, and each detector includes an 8×8 or 12×12 crystal bar array. Each detector also includes optoelectronic devices and circuitry. Of course, those skilled in the art will understand that the number of detection rings, detectors, and crystal bars can be expanded.

[0092] Specifically, in one example of this application, see [link to example]. Figure 3 Data is acquired by sequentially placing the line source within the field of view of each detector ring. The time of each crystal strip is corrected based on the acquired data to obtain the in-ring time correction value for each crystal strip. It should be noted that, due to hardware limitations, the in-ring time correction values ​​for each crystal strip are generally not identical. When acquiring all coincidence events between two adjacent detector rings, the line source is placed between the two adjacent detector rings, requiring both ends of the line source to enter the field of view of each detector ring to ensure sufficient data acquisition. Preferably, the length of the line source within the field of view of both detector rings is the same.

[0093] Preferably, the wire source is arranged parallel to the axis of the detection ring, and more preferably, the wire source is arranged to coincide with the axis of the detection ring.

[0094] Preferably, the length of the line source is substantially the same as, or slightly greater than, the axial length of a single probe ring, for example, substantially the same as the sum of the lengths of a single probe ring and the gaps on both sides thereof.

[0095] Optionally, the intra-loop time correction of each detection ring can be performed using existing time correction methods, such as the method described in CN202211731787.X. Of course, those skilled in the art will understand that other existing methods capable of achieving intra-loop time correction can also be used.

[0096] The step of sequentially acquiring all coincidence events between pairs of adjacent probe rings can be done according to the arrangement order of the probe rings, according to user preference, or by sequentially acquiring events around a selected first reference ring. Generally, the selected first reference ring offers the best performance. For example, when acquiring events sequentially according to the arrangement order of the probe rings, acquiring all coincidence events between pairs of adjacent probe rings means sequentially acquiring all first coincidence events between the first and second probe rings, all second coincidence events between the second and third probe rings, and all (N-1)th coincidence events between the (N-1)th and Nth probe rings. All first coincidence events form one data packet, all second coincidence events also form one data packet, and so on for other coincidence events. Each data packet is processed individually.

[0097] Preferably, to reduce data volume and optimize data processing speed, in one example of this application, the data acquisition module 720 is configured to: filter coincident events, remove response lines whose ends are within the same probe ring and response lines that have not passed through the source, and obtain the single-event arrival time of the remaining coincident events on the crystal strip. The purpose of this example is to collect data for inter-ring event coincidence; therefore, only coincident events occurring between rings are needed, which is reflected in the response lines as having their ends on two different probe rings. Furthermore, events that have not passed through the source are generally considered invalid events and must also be removed.

[0098] Specifically, in this application, there are multiple ways to perform inter-ring time correction. Different methods are used for correction depending on whether the axis of the line source coincides with the axis of the long-axis PET. Different methods are used for correction depending on the correction standard. For example, after correction, all detectors in each detection ring share a correction value, or after correction, all crystal strips in each detector share a correction value, or a single crystal strip uses a single correction value. Different methods are also used for correction depending on the positional relationship between the ring to be corrected and the first reference ring.

[0099] For example, in one example of this application, the axial direction of the line source coincides with the long axis PET axis, and the same calibration data is used for the same probe ring. The data acquisition module 720 is configured to: sequentially acquire all coincidence events between pairs of adjacent probe rings, select one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module 730 is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the average of the differences between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0100] Specifically, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module 730 is configured to: obtain the average value of the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, and add the average value to the intra-ring time calibration value of each crystal strip of the ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0101] Specifically, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module 730 is configured to: obtain the average value of the difference between the first arrival time and the second arrival time at both ends of all response lines of the one or more other detection rings, and obtain the average value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and accumulate all the average values ​​to the intra-ring time calibration values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0102] As a specific example of the above example, taking the first probe ring as the first reference ring and the second probe ring as the ring to be calibrated, the line source is placed between the first and second probe rings. Response lines are obtained with their two ends on the first and second probe rings respectively. For each response line, its first arrival time and second arrival time are obtained. The first arrival time is subtracted from the second arrival time to obtain the first difference. The first differences corresponding to all response lines are obtained. The first average value is taken from all the first differences. This first average value is the calibration data of the current ring to be calibrated. The first average value is added to the intra-ring time correction value of the corresponding crystal strip on the second probe ring to obtain the inter-ring time correction value. The second calibration is based on the first... The second probe ring serves as the reference ring, and the third probe ring is the ring to be calibrated. The line source is placed between the second and third probe rings, and response lines with their two ends on the second and third probe rings are acquired. For each response line, its first arrival time and second arrival time are acquired. The second arrival time is subtracted from the first arrival time to obtain the second difference. The second difference corresponding to all response lines is acquired, and the second average value is taken for all the second differences. The first average value and the second average value are added to the intra-ring time correction value of all crystal strips in the third probe ring to obtain the inter-ring time correction value of each crystal strip. The same operation is performed on all crystal strips of all rings to be calibrated to perform inter-ring time correction on all crystal strips.

[0103] For example, in one example of this application, the axial direction of the line source coincides with the long axis PET axis, and the same calibration data is used for the same probe ring. The data acquisition module 720 is configured to: sequentially acquire all coincidence events between pairs of adjacent probe rings, select one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module 730 is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time of all coincidence events on the current ring to be calibrated.

[0104] Specifically, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module 730 is configured to: obtain the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time calibration value of all crystal strips of the ring to be calibrated to obtain the inter-ring time calibration value.

[0105] Specifically, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module 730 is configured to: obtain a weighted value of the difference between the first arrival time and the second arrival time of all coincidence events of the one or more other detection rings, and obtain a weighted value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and accumulate all weighted values ​​to the intra-ring time calibration value of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0106] As a specific example of the above example, taking the first probe ring as the first reference ring and the second probe ring as the ring to be calibrated, a line source is placed between the first and second probe rings. Response lines are obtained with their two ends on the first and second probe rings respectively. For each response line, its first arrival time and second arrival time are obtained. The first arrival time is subtracted from the second arrival time to obtain a first difference. The first differences corresponding to all response lines are obtained. Weights are assigned to all first differences to obtain a first weighted value. This first weighted value is the calibration data of the current ring to be calibrated. The first weighted value is added to the intra-ring time correction value of the corresponding crystal strip on the second probe ring to obtain the inter-ring time correction value. The second calibration is based on the first... The second probe ring serves as the reference ring, and the third probe ring is the ring to be calibrated. A line source is placed between the second and third probe rings, acquiring response lines at both ends on the second and third probe rings respectively. For each response line, its first and second arrival times are obtained. The second difference is obtained by subtracting the second arrival time from the first arrival time. The second differences for all response lines are then calculated, and weights are assigned to all second differences to obtain a second weighted value. This first and second weighted values ​​are added to the intra-ring time correction value of all crystal strips in the third probe ring to obtain the inter-ring time correction value for each crystal strip. The same operation is performed on all crystal strips in all rings to be calibrated to perform inter-ring time correction. Note that the weights assigned to different differences can be the same or different for different probe rings.

[0107] For example, in one example of this application, the axial direction of the line source does not coincide with the long axis PET axis, and the same calibration data is used for the same probe ring. The data acquisition module 720 is configured to: sequentially acquire all coincidence events between pairs of adjacent probe rings, select one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module 730 is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the average of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0108] Specifically, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module 730 is configured to: obtain the average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, and add the average value to the intra-ring time calibration value of each crystal strip of the ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0109] Specifically, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module 730 is configured to: obtain the average of the difference between the first arrival time and the second arrival time and the photon flight time at both ends of all response lines of the one or more other detection rings, and obtain the average of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and accumulate all the average values ​​to the intra-ring time calibration values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0110] As a specific example of the above example, taking the first detector ring as the first reference ring and the second detector ring as the ring to be calibrated, the line source is placed between the first and second detector rings. Response lines are obtained with their two ends on the first and second detector rings respectively. For each response line, its first arrival time, second arrival time, and photon flight time are obtained. The first difference is obtained by subtracting the second arrival time and photon flight time from the first arrival time. The first difference is obtained for all response lines. The first average value is taken for all first differences, and this first average value is the calibration data for the current ring to be calibrated. The first average value is added to the intra-ring time correction value of the corresponding crystal strip on the second detector ring to obtain the inter-ring time correction value. The second calibration is based on the first... The second detector ring serves as the reference ring, and the third detector ring is the ring to be calibrated. The line source is placed between the second and third detector rings, and response lines are acquired at both ends on the second and third detector rings, respectively. For each response line, its first arrival time, second arrival time, and photon flight time are acquired. The second arrival time is subtracted from the first arrival time to obtain the second difference. The second difference corresponding to all response lines is acquired, and the second average value is taken for all the second differences. The first average value and the second average value are added to the intra-ring time correction value of all crystal strips in the third detector ring to obtain the inter-ring time correction value of each crystal strip. The same operation is performed on all crystal strips of all rings to be calibrated to perform inter-ring time correction on all crystal strips.

[0111] For example, in one example of this application, the axial direction of the line source does not coincide with the long axis PET axis, and the same calibration data is used for the same probe ring. The data acquisition module 720 is configured to: sequentially acquire all coincidence events between pairs of adjacent probe rings, select one of the pairs of adjacent probe rings as a reference ring and the other as the ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; the inter-ring calibration module 730 is configured to: obtain the inter-ring time calibration value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time calibration value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events on the current ring to be calibrated.

[0112] Specifically, if the current ring to be calibrated is adjacent to the first reference ring, the inter-ring calibration module 730 is configured to: obtain the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time calibration value of all crystal strips of the ring to be calibrated to obtain the inter-ring time calibration value.

[0113] Specifically, if there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module 730 is configured to: obtain a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincidence events of the one or more other detection rings, and obtain a weighted value of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event deposited by the crystal strip to be calibrated; and accumulate all weighted values ​​to the intra-ring time calibration values ​​of all crystal strips of the current ring to be calibrated to obtain the inter-ring time calibration value of each crystal strip.

[0114] As a specific example of the above example, taking the first detector ring as the first reference ring and the second detector ring as the ring to be calibrated, a line source is placed between the first and second detector rings. Response lines are obtained with their two ends on the first and second detector rings respectively. For each response line, its first arrival time, second arrival time, and photon flight time are obtained. The first difference is obtained by subtracting the second arrival time and photon flight time from the first arrival time. The first difference is obtained for all response lines. A weight is assigned to all first differences to obtain a first weighted value. This first weighted value is the calibration data for the current ring to be calibrated. The first weighted value is added to the intra-ring time correction value of the corresponding crystal strip on the second detector ring to obtain the inter-ring time correction value. The second calibration is performed with the first... The second detector ring serves as the reference ring, and the third detector ring is the ring to be calibrated. A line source is placed between the second and third detector rings, and response lines are acquired at both ends on the second and third detector rings, respectively. For each response line, its first arrival time, second arrival time, and photon flight time are obtained. The second arrival time is subtracted from the first arrival time to obtain the second difference. The second differences for all response lines are obtained, and weights are assigned to all second differences to obtain a second weighted value. The first and second weighted values ​​are added to the intra-ring time correction values ​​of all crystal strips in the third detector ring to obtain the inter-ring time correction values ​​for each crystal strip. The same operation is performed on all crystal strips in all rings to be calibrated to perform inter-ring time correction on all crystal strips. Note that the weights assigned to different differences can be the same or different for different detector rings.

[0115] Furthermore, unlike all the examples above, this application can also use a non-end probe ring as the first reference ring. For example, if the second probe ring is used as the reference ring, then the inter-ring time correction can be performed on the other probe rings sequentially to both sides according to the steps in the examples above.

[0116] The time correction device provided in this application first performs intra-loop time correction, and then performs inter-loop time correction by acquiring the single-event arrival time of inter-loop coincidence events and combining the single-event arrival time and intra-loop time correction value. Since the length of the existing line source can basically cover a single detector ring, it provides a basis for acquiring inter-loop coincidence events. By combining the inter-loop coincidence event information, the inter-loop time correction can be made not limited by the length of the line source, thereby improving the overall time correction quality of the digital PET system, which is beneficial to improving image quality, reducing radiation dose, and achieving inter-loop time correction of long-axis PET at the lowest possible cost.

[0117] It should be understood that Figure 6The apparatus and modules shown can be implemented in various ways. For example, in some embodiments, the apparatus and modules can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution device, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the methods and apparatus described above can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The apparatus and modules described in this application can be implemented not only with hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., but also with software, for example, executed by various types of processors, or with a combination of the aforementioned hardware circuits and software (e.g., firmware).

[0118] It should be noted that the above description of the modules is for convenience only and should not be construed as limiting this specification to the embodiments described. It is understood that those skilled in the art, after understanding the principle of the device, may arbitrarily combine the modules or construct subsystems connected to other modules without departing from this principle. For example, the modules may share a single storage module, or each module may have its own separate storage module. Such modifications are all within the scope of this specification.

[0119] Figure 7 This is a schematic diagram of a time correction system used to implement the time correction method in one embodiment of this application. (Refer to...) Figure 7 The time correction system S00 may include a processing component S20, which further includes one or more processors, and memory resources represented by a memory S22 for storing instructions, such as application programs, that can be executed by the processors of the processing component S20. The application programs stored in the memory S22 may include one or more instructions, with each module corresponding to a set of instructions. Furthermore, the processing component S20 is configured to execute instructions to perform the aforementioned time correction method.

[0120] The operations and / or methods described in the embodiments of this specification, implemented by a single processor, may also be implemented jointly or independently by multiple processors. For example, if, in this application specification, the processor of the processing device executes steps 100 to 300, it should be understood that steps 100 to 300 may also be executed jointly or independently by two different processors of the processing device (e.g., the first processor executes steps 100 to 200, the second processor executes step 300, or the first and second processors jointly execute steps 100 to 300).

[0121] The time correction system S00 may further include: a power supply component S24 configured to perform power management of the time correction system S00; a wired or wireless network interface S26 configured to connect the time correction system S00 to a network; and an input / output (I / O) interface S28. The time correction system S00 can operate on an operating system stored in memory S22, such as Windows Server, Mac OS X, Unix, Linux, FreeBSD, or similar.

[0122] In an exemplary embodiment, a computer-readable storage medium including instructions is also provided, such as a memory S22 including instructions, which can be executed by the processor of the xx system S00 to perform the above method. The storage medium can be a computer-readable storage medium, for example, it can be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc.

[0123] In an exemplary embodiment, a computer program product is also provided, the computer program product including instructions that can be executed by the processor of the time correction system S00 to perform the above method.

[0124] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 8 As shown, Figure 8This is an internal structural diagram of a computer device according to one embodiment of this application. The computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores user- and task-related data used in the aforementioned time correction method. The network interface communicates with external terminals via a network connection. When the computer program is executed by the processor, it implements a time correction method.

[0125] Those skilled in the art will understand that Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0126] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0127] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, hardware + program embodiments are basically similar to method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0128] It should be noted that the devices, electronic devices, servers, etc., described above according to the method embodiments may also include other implementation methods, and specific implementation methods can be referred to the description of the relevant method embodiments. Furthermore, new embodiments formed by the combination of features between various methods, devices, and server embodiments still fall within the scope of this application, and will not be elaborated upon here.

[0129] In the description of this specification, the references to "one embodiment," "an embodiment," and / or "some embodiments," "some embodiments," "other embodiments," "ideal embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiment or example, and certain features, structures, or characteristics in one or more embodiments of this specification may be appropriately combined.

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

[0132] The basic concepts have been described herein. It is obvious that the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, various modifications, improvements, and corrections may be made to this specification by those skilled in the art. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0133] Furthermore, those skilled in the art will understand that various aspects of this specification can be described and illustrated in several patentable ways or situations, including any new and useful combination of processes, machines, products, or substances, or any new and useful improvements thereof. Accordingly, various aspects of this specification can be implemented entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. All of the above hardware or software may be referred to as a “data block,” “module,” “engine,” “module,” “component,” or “system.” Furthermore, various aspects of this specification may be represented as a computer product located on one or more computer-readable media, including computer-readable program code.

[0134] Computer storage media may contain a propagated data signal containing computer program code, for example, on baseband or as part of a carrier wave. This propagated signal may take various forms, including electromagnetic, optical, and suitable combinations thereof. Computer storage media can be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction execution system, apparatus, or device to enable communication, propagation, or transmission of a program for use. The program code located on the computer storage medium can be propagated through any suitable medium, including radio, cable, fiber optic cable, RF, or similar media, or any combination of the above media.

[0135] The computer program code required for the operation of each part of this manual can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python, etc.; conventional procedural programming languages ​​such as C, Visual Basic, Fortran 3003, Perl, COBOL 3002, PHP, ABAP; dynamic programming languages ​​such as Python, Ruby, and Groovy; or other programming languages. This program code can run entirely on the user's computer, or as a standalone software package on the user's computer, or partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any network, such as a local area network (LAN) or wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as Software as a Service (SaaS).

[0136] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although various examples have been discussed in the foregoing disclosure of some embodiments of the invention that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments described herein. For example, while the system components described above can be implemented using hardware devices, they can also be implemented solely using software solutions, such as installing the described system on existing servers or mobile devices.

[0137] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0138] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0139] For each patent, patent application, patent application publication, and other material such as articles, books, specifications, publications, and documents referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials to this specification and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0140] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A time correction method, characterized in that, The time correction method includes: Step S100: Perform in-loop time correction on the crystal strips of multiple detector rings in sequence to obtain the in-loop time correction values ​​for all crystal strips; Step S200: Sequentially acquire all coincidence events between two adjacent detector rings, and acquire the single-event arrival time of each coincidence event on the crystal strip; Step S300: Perform inter-ring time correction on the multiple detection rings based on the current position of the ring to be calibrated, the intra-ring time correction value, and the average or weighted value of the difference between the arrival times of the two single events for each coincident event.

2. The time correction method according to claim 1, characterized in that, Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the average of the differences between the first arrival time and the second arrival time of all coincident events on the current ring to be calibrated.

3. The time correction method according to claim 2, characterized in that, If the current ring to be corrected is adjacent to the first reference ring, then step S300 includes: The average of the differences between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated is obtained, and the average value is added to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

4. The time correction method according to claim 2, characterized in that, If there are one or more other probe rings between the current ring to be calibrated and the first reference ring, then step S300 includes: The average of the differences between the first arrival time and the second arrival time at both ends of all response lines of the one or more other probe rings is obtained, and the average of the differences between the first arrival time and the second arrival time corresponding to the coincidence event of the current crystal strip deposition to be corrected is obtained. The inter-ring time correction value of each crystal strip is obtained by summing all the average values ​​and adding them to the intra-ring time correction values ​​of all crystal strips in the current ring to be corrected.

5. The time correction method according to claim 1, characterized in that, Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated.

6. The time correction method according to claim 5, characterized in that, If the current ring to be corrected is adjacent to the first reference ring, then step S300 includes: Obtain the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

7. The time correction method according to claim 5, characterized in that, If there are one or more other probe rings between the current ring to be calibrated and the first reference ring, then step S300 includes: Obtain the weighted value of the difference between the first arrival time and the second arrival time of all coincidence events of the one or more other detection rings, and obtain the weighted value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event of the current crystal strip deposition to be corrected; The inter-ring time correction value of each crystal strip is obtained by summing all weighted values ​​to the intra-ring time correction value of all crystal strips in the current ring to be corrected.

8. The time correction method according to claim 1, characterized in that, Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated, and acquiring the photon flight time corresponding to the coincidence event; Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the average value of the difference between the first arrival time and the second arrival time and the photon flight time of all coincident events on the current ring to be calibrated.

9. The time correction method according to claim 8, characterized in that, If the current ring to be corrected is adjacent to the first reference ring, then step S300 includes: The average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated is obtained, and the average value is added to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

10. The time correction method according to claim 8, characterized in that, If there are one or more other probe rings between the current ring to be calibrated and the first reference ring, then step S300 includes: The average of the difference between the first arrival time and the second arrival time and the photon flight time at both ends of all response lines of the one or more other detector loops is obtained, and the average of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event of the current crystal strip deposition to be corrected is obtained. The inter-ring time correction value of each crystal strip is obtained by summing all the average values ​​and adding them to the intra-ring time correction values ​​of all crystal strips in the current ring to be corrected.

11. The time correction method according to claim 1, characterized in that, Step S200 includes: sequentially acquiring all coincidence events between pairs of adjacent detector rings, selecting one of the pairs of adjacent detector rings as a reference ring and the other as a ring to be calibrated, for each coincidence event, acquiring its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated, and acquiring the photon flight time corresponding to the coincidence event; Step S300 includes: obtaining the inter-ring time correction value of each crystal strip of the ring to be calibrated based on the positional relationship between the current ring to be calibrated and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be calibrated, and the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated.

12. The time correction method according to claim 11, characterized in that, If the current ring to be corrected is adjacent to the first reference ring, then step S300 includes: Obtain the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated. Assign weights to all differences to obtain a weighted value. Add the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

13. The time correction method according to claim 11, characterized in that, If there are one or more other probe rings between the current ring to be calibrated and the first reference ring, then step S300 includes: Obtain the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time for all coincidence events of the one or more other detection rings, and obtain the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time for the coincidence event corresponding to the current crystal strip deposition to be corrected; The inter-ring time correction value of each crystal strip is obtained by summing all weighted values ​​to the intra-ring time correction value of all crystal strips in the current ring to be corrected.

14. The time correction method according to any one of claims 2 to 13, characterized in that, Inter-ring time correction is performed using the first detector ring as the reference ring and the second detector ring as the ring to be corrected. Then, inter-ring time correction is performed sequentially using the previous detector ring as the reference ring and the next detector ring as the ring to be corrected.

15. The time correction method according to any one of claims 2 to 13, characterized in that, Inter-ring time correction is performed using any one of the detector rings as the reference ring and the detector rings adjacent to it on one or both sides as the rings to be corrected. When there are uncorrected detector rings on one or both sides of the corrected detector ring, inter-ring time correction is performed using the corrected detector ring as the reference ring and the uncorrected detector rings as the rings to be corrected.

16. The time correction method according to claim 1, characterized in that, Step S200 includes: The coincident events are filtered out, and response lines whose two ends are in the same detection loop and response lines that have not passed through the source are removed. The arrival times of the remaining coincident events on the crystal strip are then obtained.

17. The time correction method according to claim 1, characterized in that, Both steps S100 and S200 involve collecting data from the line source detection to calculate the loop time correction value and obtain the event arrival time.

18. The time correction method according to claim 15, characterized in that, In step S100, the line source is placed sequentially within the detection field of view of each detection ring; In step S200, the line source is placed sequentially between two adjacent detection rings, and both ends of the line source are located within a portion of the detection field of view of the two detection rings respectively.

19. The time correction method according to claim 18, characterized in that, The arrangement direction of the line source is parallel to the axis of the detection ring.

20. The time correction method according to claim 18, characterized in that, The arrangement direction of the line source coincides with the axis of the detection ring.

21. A time correction device, characterized in that, The time correction device includes: The in-loop correction module is configured to sequentially perform in-loop time correction on the crystal strips of multiple detection rings to obtain the in-loop time correction values ​​for all crystal strips. The data acquisition module is configured to sequentially acquire all coincidence events between two adjacent detector rings, and acquire the single-event arrival time of each coincidence event on the crystal strip; The inter-loop correction module is configured to perform inter-loop time correction on multiple detection loops based on the current position of the loop to be calibrated, the intra-loop time correction value, and the average or weighted value of the difference between the arrival times of the two single events for each coincident event.

22. The time correction device according to claim 21, characterized in that, The data acquisition module is configured to: sequentially acquire all coincidence events between pairs of adjacent detection rings, select one of the pairs of adjacent detection rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; The inter-ring correction module is configured to obtain the inter-ring time correction value of each crystal strip of the ring to be corrected based on the positional relationship between the current ring to be corrected and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be corrected, and the average value of the difference between the first arrival time and the second arrival time of all matching events on the current ring to be corrected.

23. The time correction device according to claim 22, characterized in that, If the current ring to be calibrated is adjacent to the first reference ring, then the inter-ring calibration module is configured as follows: The average of the differences between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated is obtained, and the average value is added to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

24. The time correction device according to claim 22, characterized in that, If there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured as follows: The average of the differences between the first arrival time and the second arrival time at both ends of all response lines of the one or more other probe rings is obtained, and the average of the differences between the first arrival time and the second arrival time corresponding to the coincidence event of the current crystal strip deposition to be corrected is obtained. The inter-ring time correction value of each crystal strip is obtained by summing all the average values ​​and adding them to the intra-ring time correction values ​​of all crystal strips in the current ring to be corrected.

25. The time correction device according to claim 21, characterized in that, The data acquisition module is configured to: sequentially acquire all coincidence events between pairs of adjacent detection rings, select one of the pairs of adjacent detection rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated; The inter-ring correction module is configured to obtain the inter-ring time correction value of each crystal strip of the ring to be corrected based on the positional relationship between the current ring to be corrected and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be corrected, and the weighted value of the difference between the first arrival time and the second arrival time of all matching events on the current ring to be corrected.

26. The time correction device according to claim 25, characterized in that, If the current ring to be calibrated is adjacent to the first reference ring, then the inter-ring calibration module is configured as follows: Obtain the difference between the first arrival time and the second arrival time of all matching events on the current ring to be calibrated, assign weights to all differences to obtain a weighted value, and add the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

27. The time correction device according to claim 25, characterized in that, If there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured as follows: Obtain the weighted value of the difference between the first arrival time and the second arrival time of all coincidence events of the one or more other detection rings, and obtain the weighted value of the difference between the first arrival time and the second arrival time corresponding to the coincidence event of the current crystal strip deposition to be corrected; The inter-ring time correction value of each crystal strip is obtained by summing all weighted values ​​to the intra-ring time correction value of all crystal strips in the current ring to be corrected.

28. The time correction device according to claim 21, characterized in that, The data acquisition module is configured to: sequentially acquire all coincidence events between two adjacent detector rings, select one of the two adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated, and acquire the photon flight time corresponding to the coincidence event. The inter-ring correction module is configured to obtain the inter-ring time correction value of each crystal strip of the ring to be corrected based on the positional relationship between the current ring to be corrected and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be corrected, and the average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be corrected.

29. The time correction device according to claim 28, characterized in that, If the current ring to be calibrated is adjacent to the first reference ring, then the inter-ring calibration module is configured as follows: The average value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated is obtained, and the average value is added to the intra-ring time correction value of each crystal strip of the ring to be calibrated to obtain the inter-ring time correction value of each crystal strip.

30. The time correction device according to claim 28, characterized in that, If there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured as follows: The average of the difference between the first arrival time and the second arrival time and the photon flight time at both ends of all response lines of the one or more other detector loops is obtained, and the average of the difference between the first arrival time and the second arrival time and the photon flight time corresponding to the coincidence event of the current crystal strip deposition to be corrected is obtained. The inter-ring time correction value of each crystal strip is obtained by summing all the average values ​​and adding them to the intra-ring time correction values ​​of all crystal strips in the current ring to be corrected.

31. The time correction device according to claim 21, characterized in that, The data acquisition module is configured to: sequentially acquire all coincidence events between two adjacent detector rings, select one of the two adjacent detector rings as a reference ring and the other as a ring to be calibrated, and for each coincidence event, acquire its first arrival time on the crystal strip of the reference ring and its second arrival time on the crystal strip of the ring to be calibrated, and acquire the photon flight time corresponding to the coincidence event. The inter-ring correction module is configured to obtain the inter-ring time correction value of each crystal strip of the ring to be corrected based on the positional relationship between the current ring to be corrected and the first reference ring, the intra-ring time correction value of each crystal strip on the current ring to be corrected, and the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be corrected.

32. The time correction device according to claim 31, characterized in that, If the current ring to be calibrated is adjacent to the first reference ring, then the inter-ring calibration module is configured as follows: Obtain the difference between the first arrival time and the second arrival time and the photon flight time of all matching events on the current ring to be calibrated. Assign weights to all differences to obtain a weighted value. Add the weighted value to the intra-ring time correction value of all crystal strips of the ring to be calibrated to obtain the inter-ring time correction value.

33. The time correction device according to claim 31, characterized in that, If there are one or more other detection rings between the current ring to be calibrated and the first reference ring, the inter-ring calibration module is configured as follows: Obtain the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time for all coincidence events of the one or more other detection rings, and obtain the weighted value of the difference between the first arrival time and the second arrival time and the photon flight time for the coincidence event corresponding to the current crystal strip deposition to be corrected; The inter-ring time correction value of each crystal strip is obtained by summing all weighted values ​​to the intra-ring time correction value of all crystal strips in the current ring to be corrected.

34. The time correction device according to claim 21, characterized in that, The data acquisition module is configured to: filter coincident events, remove response lines whose two ends are in the same detection loop and response lines that have not passed through the source, and obtain the event arrival time of the remaining coincident events on the crystal strip.

35. A computer storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the time correction method according to any one of claims 1 to 20.

36. A computer program product, characterized in that, It includes a computer program or instructions, characterized in that, when the computer program or instructions are executed by a processor, they implement the steps of the time correction method according to any one of claims 1 to 20.

37. A digital PET system, characterized in that, Time correction is performed using the time correction device described in any one of claims 21 to 34.

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