Signal sampling method, device, equipment and storage medium for digital PET

Abstract

The present application discloses a signal sampling method, device, equipment and storage medium for digital PET. The signal sampling method includes: presetting at least two thresholds that can be switched and selected; using the same comparison module to compare the flicker pulse to be processed with at least two thresholds in turn, and determining at least two state signals corresponding to at least two thresholds when the flicker pulse to be processed crosses the threshold; using the same sampling module to perform time sampling on at least two state signals in turn, and obtaining corresponding flicker pulse threshold-time pairs. The present application can reduce the number of pins and realize the reuse of sampling modules while ensuring sampling accuracy, greatly saving logic resources.

Description

Technical Field

[0001] The present application relates to the field of positron emission tomography, and in particular to a digital PET signal sampling method, device, equipment and storage medium. Background Art

[0002] Positron emission tomography (PET) is a high-end nuclear medicine imaging equipment, widely used in cancer diagnosis and treatment, brain science research, cardiology research, heavy ion radiotherapy monitoring and other fields, in which gamma-ray detectors are used extensively for signal sampling. The multi-voltage threshold sampling (MVT) method proposed by Xie Qingguo's team completes the digitization of scintillation pulses by sampling the time point when the scintillation pulses cross the threshold voltage. The MVT method can directly digitize the scintillation pulse signal when the detector is sampled, thereby making the detector modular and bringing PET into the digital PET era.

[0003] The key to the MVT method is to obtain the time information when the input waveform crosses the set threshold through TDC (time-to-digital conversion) technology, thereby inverting the waveform information. It usually requires threshold comparisons of multiple channels and subsequent time measurements, which consumes a certain amount of logic resources inside the FPGA to achieve. The processing circuit of the waveform output by a single SIPM detector is usually as follows: Figure 1 As shown in the figure, the waveform of a single channel corresponds to a 4-channel comparator (LVDS Comparator), which requires 8 input pins of the FPGA chip and an 8-channel TDC measurement module. An FPGA usually needs to process signals from dozens or hundreds of channels. The FPGA chip usually used in PET can provide 115K logic resources and about 500 available LVDS pins. Neither its pins nor its logic resources can process the data of many channels. The logic resources are limited, and the measurement accuracy of the TDC module is also restricted.

[0004] In summary, the excessive FPGA resource consumption and the number of input pins have become a bottleneck in system design. It is urgent to provide a signal sampling method, device, equipment and storage medium for digital PET to solve at least one of the above technical problems.

[0005] The content of this background technology description is only for facilitating understanding of the relevant technology in this field and is not regarded as an admission of the prior art. Summary of the invention

[0006] The purpose of the embodiments of the present application is to provide a signal sampling method, device, equipment and storage medium for digital PET to solve at least one technical problem existing in the prior art.

[0007] According to the first aspect of the present application, a signal sampling method for digital PET is provided, and the signal sampling method includes: presetting at least two switchable thresholds; using the same comparison module to compare the flicker pulse to be processed with the at least two thresholds in turn, and determining at least two state signals corresponding to the at least two thresholds when the flicker pulse to be processed crosses the threshold; using the same sampling module to perform time sampling on the at least two state signals in turn to obtain corresponding flicker pulse threshold-time pairs.

[0008] According to the second aspect of the present application, a signal sampling method for digital PET is provided, the signal sampling method comprising: presetting at least two groups of thresholds, each group of thresholds comprising at least two switchable thresholds; setting in parallel at least two comparison modules corresponding to the at least two groups of thresholds one by one; using the comparison module to compare the flicker pulse to be processed with the at least two thresholds of each corresponding group in each channel, and determining at least two status signals corresponding to the at least two thresholds of each group respectively when the flicker pulse to be processed crosses the threshold; using the same sampling module to perform time sampling on the status signals in sequence to obtain corresponding flicker pulse threshold-time pairs.

[0009] According to the third aspect of the present application, a signal sampling device for a digital PET is provided, the signal sampling device comprising: an acquisition module for acquiring a flicker pulse to be processed; a threshold providing module for switching and selecting at least two preset thresholds; a comparison module for sequentially comparing the flicker pulse to be processed with at least two thresholds to determine at least two state signals corresponding to the at least two thresholds respectively when the flicker pulse to be processed crosses the threshold; and a sampling module for sequentially performing time sampling on at least two state signals to obtain corresponding flicker pulse threshold-time pairs.

[0010] According to the fourth aspect of the present application, a signal sampling device for digital PET is provided, the signal sampling device comprising: an acquisition module for acquiring a flicker pulse to be processed; at least two threshold providing modules, wherein each threshold providing module is used to switch and select at least two preset thresholds; at least two comparison modules arranged in parallel, which correspond one to one to the at least two threshold providing modules, wherein each comparison module is used to sequentially compare the flicker pulse to be processed with at least two thresholds provided by the corresponding threshold providing module, and determine at least two state signals corresponding to the at least two thresholds respectively when the flicker pulse to be processed crosses the threshold; and a sampling module for sequentially performing time sampling on the state signals to obtain corresponding flicker pulse threshold-time pairs.

[0011] According to a fifth aspect of the present application, a detector device is provided, comprising: a detector and a signal sampling device of a digital PET as described in any one of the above items, wherein the detector is configured to detect gamma rays and output a scintillation pulse signal to be processed to the signal sampling device for digital sampling processing.

[0012] According to the sixth aspect of the present application, a digital PET device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the steps of the signal sampling method as described in any one of the above items are implemented.

[0013] According to a seventh aspect of the present application, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the signal sampling method described in any one of the above items are implemented.

[0014] It can be seen from the technical solution described in the above embodiments of the present application that by providing at least one group of switchable thresholds and controlling the switching selection between the set different thresholds, the switching of dynamic thresholds is realized, and only one comparison module can be used to compare the size of the flicker pulse to be processed with different thresholds in turn. Compared with the prior art that uses multiple LVDS comparators, the present application can effectively increase the number of sampling points while reducing the number of LVDS comparators, thereby reducing the number of pins, reducing the resource utilization rate of the FPGA chip, and reducing the operating temperature of the FPGA chip, which helps to improve the measurement accuracy of the sampling module; at the same time, based on the multi-threshold flicker pulse waveform sampling achieved through threshold switching, only one sampling module can be used to achieve time sampling of the flicker pulse, thereby realizing the reuse of the sampling module, greatly saving computing resources, and effectively reducing energy consumption, thereby improving system performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present application will be further described in the form of exemplary embodiments, which will be described in detail by way of the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0016] Figure 1 is an exemplary processing circuit diagram of multi-voltage threshold sampling according to the prior art;

[0017] Figure 2 is an exemplary flow chart of a signal sampling method for digital PET according to some embodiments of the present application;

[0018] Figure 3 A schematic diagram of an exemplary relationship between a threshold voltage and a flicker pulse to be processed according to some embodiments of the present application;

[0019] Figure 4 is an exemplary flow chart of sequentially sampling at least two state signals according to some embodiments of the present application;

[0020] Figure 5 is an exemplary flow chart of scintillation pulse signal sampling according to other embodiments of the present application;

[0021] Figure 6 is an exemplary flow chart of sequentially sampling state signals in time according to some embodiments of the present application;

[0022] Figure 7 is an exemplary module diagram of a signal sampling device for digital PET according to some embodiments of this specification;

[0023] Figure 8 is an exemplary module diagram of a signal sampling device for digital PET according to some embodiments of the present specification. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0025] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly fixed to the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "and / or" or "and / or" used herein include any and all combinations of one or more related listed items.

[0027] Some preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be noted that the following description is for illustrative purposes and is not intended to limit the scope of protection of the present application.

[0028] Figure 2 FIG. 1 is an exemplary flow chart of signal sampling of digital PET according to some embodiments of the present application. Figure 2 As shown, the signal sampling method S200 of digital PET may include the following steps.

[0029] Step S210: presetting at least two switchable thresholds.

[0030] In some embodiments, at least two thresholds can be used for comparison with the amplitude of the scintillation pulse to be processed. The comparison result can be used for time sampling to determine the time point when the amplitude of the scintillation pulse to be processed crosses the threshold. These time points can be used for waveform recovery in subsequent processing (e.g., image reconstruction) after matching with the corresponding thresholds, such as recovering the area of ​​the waveform, and then obtaining the waveform energy value. The size of the threshold is set not to exceed the maximum amplitude of the scintillation pulse to be processed, that is, the size of the threshold is within the amplitude of the scintillation pulse to be processed.

[0031] refer to Figure 3 , Figure 3 The figure is a schematic diagram of the exemplary relationship between the threshold voltage and the flicker pulse according to some embodiments of the present application, wherein 310 represents a flicker pulse, which may be the flicker pulse to be processed mentioned in the present application. The waveform of the flicker pulse in the figure shows its characteristics, that is, the rising period is very short, usually only a few nanoseconds, it can rise to the highest point. The falling period is relatively long, usually more than 100ns, generally about 200 nanoseconds. Figure 3 In the illustrated embodiment, 8 threshold voltages are set, and 310-1 to 310-8 represent 8 different threshold voltages. It can be seen that the magnitudes of the 8 threshold voltages are all within the amplitude of the scintillation pulse. For example, assuming that the amplitude of the scintillation pulse to be processed ranges from 5mV to 200mV, the 8 threshold voltages may be 10mV, 50mV, 70mV, 90mV, 110mV, 120mV, 140mV, and 160mV, respectively.

[0032] In some embodiments, the scintillation pulse to be processed is generally acquired by a PET detector, which generally includes mutually coupled scintillation crystals and photoelectric conversion devices, wherein the scintillation crystals are used to convert the detected high-energy rays (such as gamma rays, neutron rays, etc.) into visible light signals, and the photoelectric conversion devices (for example, photomultiplier tubes PMT, silicon photomultiplier tubes SiPM, etc.) are used to convert the visible light signals into electrical signals, which are output in the form of scintillation pulse signals through electronic devices connected to the photoelectric conversion devices. For example, the acquisition module can communicate with the detector to acquire the scintillation pulse to be processed.

[0033] In some embodiments, the scintillation pulse generally has a rising edge and a falling edge, and the rising edge and the falling edge can be represented by a function model. For example, the scintillation pulse corresponding to a gamma photon generally exhibits a relatively fast rising edge and a relatively slow falling edge. The rising edge can be represented by a linear function, and the falling edge can be represented by an exponential function.

[0034] In some embodiments, at least two thresholds that can be switched and selected are preset through a threshold providing module, and the threshold providing module is implemented by a circuit including a threshold control module and a threshold selection module. The threshold control module controls the threshold selection module to switch and select the preset threshold. In some embodiments, the threshold control module controls the threshold selection module through a control line. In one embodiment, the threshold control module includes a threshold controller, and the threshold selection module includes a data selector MUX (multiplexer). In one embodiment of the present application, an 8-to-1 data selector MUX8 can be specifically used to preset 8 thresholds that can be switched and selected. After at least two thresholds that can be switched and selected are preset, the threshold controller controls MUX8 to switch and select at least two thresholds, and the switched and selected thresholds are transmitted to the LVDS comparator for amplitude comparison. The threshold controller controls the switching and selection operation of the threshold according to the comparison result between the amplitude of the flicker pulse to be processed and the threshold currently selected by the data selector MUX8, and the threshold controller controls MUX8 through a control line.

[0035] Step S220: using the same comparison module to sequentially compare the scintillation pulse to be processed with at least two thresholds, and determining at least two state signals corresponding to the at least two thresholds respectively when the scintillation pulse to be processed crosses the threshold.

[0036] In some embodiments, the same comparison module is used to compare at least two preset thresholds with the amplitude of the flicker pulse to be processed in sequence. The comparison module is implemented by a circuit including a comparator, which can compare the received threshold value with the amplitude of the flicker pulse, and the comparator compares the flicker pulse to be processed with the magnitude of each threshold value switched and selected from the at least two thresholds in sequence.

[0037] In some embodiments, the comparison module 820 can be implemented by a circuit including a low-voltage differential signal (LVDS) comparator. As an example, the scintillation pulse generated by the detector can be input to the p-end (also referred to as the positive end) of the LVDS comparator pin, and the currently switched selected threshold can be input to the n-end (also referred to as the negative end) of the LVDS comparator pin, thereby completing the comparison between the pulse waveform and the threshold.

[0038] It can be known that for the setting of the threshold, under normal circumstances, the flicker pulse can cross the same threshold twice. One is in the rising stage of the flicker pulse, the amplitude of the flicker pulse can cross the threshold from low to high and be higher than the threshold. The other is in the falling stage of the flicker pulse, the amplitude of the flicker pulse can cross the threshold from high to low and be lower than the threshold. Regardless of which one crosses, the comparison module can generate a jump and record the time when the amplitude crosses the threshold. For example Figure 3 The schematic diagram of the principle of multi-voltage threshold sampling is shown. In the rising stage, the flicker pulse 310 will first cross and be higher than the threshold voltage 310-1, then continue to go up, cross and be higher than the threshold voltage 310-2, and then cross and be higher than the threshold voltages 310-3 to 310-8 in sequence. In the falling stage, the flicker pulse 310 will first cross and be lower than the threshold voltage 310-8. Then continue to go down, cross and be lower than the threshold voltage 310-7, and then cross and be lower than the threshold voltages 310-6 to 310-1 in sequence. In the whole process, the pulse voltage 310 can undergo 16 state changes relative to the above 8 threshold voltages.

[0039] It should be understood by those skilled in the art that when the threshold is set to be large, such as higher than the maximum amplitude of the signal, the amplitude of the scintillation pulse can never exceed the preset threshold, so the comparison module will not change state; when the threshold is set to be exactly equal to the maximum amplitude of the signal, the comparison module will only change state once. Therefore, generally, those skilled in the art can reasonably set the size and number of the thresholds based on limited experiments, so that the size interval of the thresholds is more reasonable. Generally, 2-8 evenly spaced thresholds are selected, and the collected information is closer to the real state, which can reduce the number of channels while accurately restoring the pulse shape, and improve data processing efficiency. I will not go into details here.

[0040] In some embodiments, the comparison module can compare the flicker pulse to be processed with the current threshold selected by the switch, and output a state signal. The state signal can indicate the state change of the pulse to be processed relative to the threshold (for example, from below the threshold to crossing and above the threshold or from above the threshold to crossing and below the threshold). The time sampling involved in the subsequent part of this application can refer to the time measurement of the moment corresponding to the state signal. Each state signal includes a rising edge and a falling edge. For example, the rising edge corresponds to the moment when the flicker pulse to be processed crosses the threshold voltage 310-1 to 310-8 in sequence at the rising edge of the pulse, and the falling edge corresponds to the moment when the flicker pulse to be processed crosses the threshold voltage 310-8 to 310-1 in sequence at the falling edge of the pulse. The rising edge indicates that the flicker pulse to be processed crosses and is higher than the threshold voltage from bottom to top, and the falling edge indicates that the flicker pulse to be processed crosses and is lower than the threshold voltage from top to bottom. The moment corresponding to the position of the rising edge and the falling edge can be the moment when the flicker pulse crosses the threshold voltage. Those skilled in the art should understand that, in the above embodiments, only the voltage threshold and the voltage state signal are used as examples, and other thresholds and state changes are generally applicable in principle and will not be described in detail herein.

[0041] Continue to return to reference Figure 3 ,from Figure 3 It can be seen that due to the characteristics of the scintillation pulse, the rising edges of the state signal corresponding to each threshold voltage are very close, so that the time corresponding to the position of each rising edge is also very close. This is not conducive to the subsequent data processing process, for example, the process of image reconstruction based on the time sampling result of the scintillation pulse waveform. Therefore, in one embodiment of the present application, the state signal includes a rising edge indicating that the scintillation pulse to be processed crosses at least part of the thresholds including the lowest threshold among at least two thresholds and a falling edge that crosses all thresholds among at least two thresholds. In one example of the present application, the state signal includes the rising edge of the scintillation pulse to be processed corresponding to the moment when the rising edge of the pulse crosses the lowest threshold voltage 310-1, and the falling edges of the scintillation pulse to be processed corresponding to the moments when the falling edges of the pulse cross the threshold voltages 310-8 to 310-1 respectively.

[0042] In some embodiments of the present application, the same comparison module is used to sequentially compare the flicker pulse to be processed with at least two thresholds, including sequentially switching between at least two thresholds according to a state signal, so that the same comparison module sequentially compares the size of the pulse to be processed with different thresholds of the at least two thresholds. Wherein, sequentially switching between at least two thresholds according to a state signal is implemented by a threshold providing module, specifically, the threshold providing module selects and controls the threshold of the negative end of the input LVDS comparator according to the state signal output by the LVDS comparator. In one embodiment, the flicker pulse to be processed is input to the positive end of the LVDS comparator, and the threshold voltage switched and selected by the threshold providing module is input to the negative end of the LVDS comparator. When the level of the flicker pulse to be processed is higher than the threshold level currently switched and selected, the state signal of the output of the LVDS comparator is 1, and when the level of the flicker pulse to be processed is lower than the threshold level currently switched and selected, the state signal of the output of the LVDS comparator is 0. The result of the LVDS comparator output is connected to the threshold control module of the threshold providing module as a feedback input. The threshold controller of the threshold control block controls the MUX8 of the threshold selection module to switch the selection threshold in accordance with the rising edge order (i.e., ascending order) or the falling edge order (i.e., descending order) through the control line according to the feedback input signal. In one example, during the rising edge sampling process, when the result of the LVDS comparator output is 0, the threshold controller controls MUX8 to continue to select the current threshold, and when the result of the LVDS comparator output is 1, the threshold controller controls MUX8 to switch to the next threshold according to the rising edge order; when the rising edge sampling is completed, that is, switching to the maximum threshold and completing the rising edge sampling, the threshold continues to be sampled at the falling edge, and the threshold is the threshold of the first place in the sorting of the falling edge sampling, that is, the maximum threshold of the falling edge sampling. During the falling edge sampling process, when the result of the LVDS comparator output is 1, the threshold controller controls MUX8 to continue to select the current threshold, and when the result of the LVDS comparator output is 0, the threshold controller controls MUX8 to switch to the next threshold according to the falling edge order.

[0043] Step S230: Use the same sampling module to perform time sampling on at least two state signals in sequence to obtain corresponding flicker pulse threshold-time pairs.

[0044] In some embodiments, time sampling may be time digital sampling of the moment corresponding to the position of the rising edge and the falling edge of the state signal and / or the delayed state signal. In the present application, the terms "time sampling", "time digital sampling" and "time measurement" may be used interchangeably to indicate the operation of determining the moment corresponding to the position of the rising edge and the falling edge of each state signal and / or each delayed state signal after delay processing.

[0045] In some embodiments, the sampling module can sample the rising edge and the falling edge of the above delayed state signal in a certain sampling order. In some embodiments, the sampling module can be implemented by a circuit including a time-to-digital converter (TDC), the time-to-digital converter TDC is communicatively connected to the comparison module, and the time-to-digital converter implements time sampling. The sampling module can use the TDC to sample the moment corresponding to the position of the rising edge or the falling edge of the input delayed state signal.

[0046] In some embodiments, the flicker pulse threshold-time pair may include the state change time obtained by time sampling the state signal and the amplitude of the threshold corresponding to the state signal. For example, for a certain threshold V1, the comparison with the flicker pulse to be processed can obtain the state signal, and the TDC can obtain two moments by time measurement of the state signal, including the moment T1 corresponding to the position of the rising edge and the moment T2 corresponding to the position of the falling edge. T1 and T2 can be called state change time, and the flicker pulse threshold-time pair may include (V1, T1) and (V1, T2).

[0047] In some embodiments, the scintillation pulse threshold-time pair can be transmitted to other components for further processing. For example, the sampling result can be transmitted to an image processing component related to the PET device through a wired or wireless communication method for subsequent PET image reconstruction.

[0048] It should be noted that the above Figure 2 The description of each step in the embodiment is only for example and explanation, and does not limit the scope of application of this specification. For those skilled in the art, under the guidance of this specification, Figure 2 Various modifications and changes may be made to the various steps in the present invention. However, these modifications and changes are still within the scope of this specification.

[0049] The signal sampling method of the digital PET in the embodiment of the present application is based on realizing multi-threshold scintillation pulse waveform sampling through threshold switching. It can realize the time sampling of the scintillation pulse by using only one TDC of one sampling module, thereby realizing the multiplexing of the sampling module TDC, greatly saving computing resources, and effectively reducing energy consumption. At the same time, the saved resources can improve the accuracy of time sampling, thereby improving system performance.

[0050] Figure 4 FIG. 1 is an exemplary flow chart of sequentially sampling at least two state signals according to some embodiments of the present application. Figure 4As shown, the process S400 of sequentially sampling at least two status signals may include the following operations:

[0051] Step S410 , performing first time sampling based on the time corresponding to the rising edge of the state signal corresponding to the lowest threshold.

[0052] In one embodiment of the present application, the sampling module may perform first time sampling at the moment corresponding to the rising edge of the state signal corresponding to the lowest threshold value in the first order. Figure 3 Among the 8 threshold voltages, the lowest threshold value ranked first after being arranged from small to large is threshold voltage 310-1. After the state signal corresponding to the lowest threshold is output from the comparison module, it will be input to TDC for time sampling. In step S410, the LVDS comparator of the comparison module will first output the state signal corresponding to threshold voltage 310-1 to TDC, and TDC can perform time sampling at the moment corresponding to the rising edge of the state signal to complete the first time sampling.

[0053] Step S420, determining whether the first time sampling is successful.

[0054] In some embodiments, the TDC of the sampling module can output a feedback at the same time when performing time sampling on the state signal. The feedback can include one or more combinations of numbers, letters, symbols, etc. For example, the feedback can be 1 or 0. 1 indicates that the flicker pulse crosses and is higher than the threshold, and 0 indicates that the flicker pulse crosses and is lower than the threshold voltage. In this way, when sampling the time corresponding to the rising edge of the state signal, if the output feedback is 1, it means that the sampling is successful. On the contrary, if the output feedback is 0, it means that the sampling failed. In the present application Figure 3 In the real-time example, when the state signal corresponding to the lowest threshold voltage 310 - 1 is sampled for the first time, when the feedback output by the TDC is 1, it indicates that the sampling is successful.

[0055] After performing a first time sampling on a moment corresponding to a rising edge of the state signal based on the lowest threshold, the signal sampling method further includes:

[0056] Determine whether the flicker pulse to be processed is a valid signal;

[0057] If so, synchronously output the feedback signal and start switching to perform the second time sampling at the moment corresponding to the falling edge of the state signal in descending order;

[0058] If not, return to the initial state and re-execute the first time sampling.

[0059] In an embodiment of the present application, the lowest threshold among the at least two preset thresholds is more critical, and the time corresponding to the corresponding status signal is usually used to judge the arrival time of the input ray particles received by the front-end detector. It is usually set relatively low, at the order of several mV, and is prone to false triggering. It is necessary to further confirm whether the scintillation pulse to be processed is a valid signal through subsequent thresholds.

[0060] In one embodiment of the present application, determining whether a scintillation pulse to be processed is a valid signal includes the following steps:

[0061] Setting a verification threshold, taking a threshold value close to a lowest threshold value among at least two threshold values ​​as the verification threshold value;

[0062] A comparison module is used to compare the flicker pulse to be processed with the verification threshold. If the verification status signal that the flicker pulse to be processed crosses the verification threshold is not obtained, it is a false trigger signal; if the verification status signal that the flicker pulse to be processed crosses the verification threshold is obtained, it is a valid signal.

[0063] In one embodiment of the present application, it is usually possible to determine whether the rising edge position is a valid trigger by whether the scintillation pulse waveform crosses a higher second threshold. The rising edge sampling of the scintillation pulse waveform first determines whether the signal passes the lowest threshold, completes the first time sampling, and then eliminates the false trigger signal by whether it passes the second threshold, and obtains a valid rising edge starting point as the key data for the subsequent particle arrival time.

[0064] In some embodiments, the rising edge period of the flicker pulse is very short, usually reaching its peak in just a few nanoseconds. The falling edge period is longer, usually exceeding 100ns, and generally around 200 nanoseconds. Therefore, after completing the first time sampling, during the switching process from the lowest threshold to the second threshold by the threshold providing module, the input flicker pulse waveform amplitude has exceeded the level of the second threshold. Therefore, after the threshold providing module completes the threshold switching from the lowest threshold to the second threshold, it can directly determine whether it is a valid signal. If it is a false trigger, it returns to the starting state. If it is a valid signal, the threshold is directly set to the highest threshold to perform waveform acquisition on the falling edge. In the case where the flicker pulse signal is a valid signal, given that during the switching process from the lowest threshold to the second threshold by the threshold providing module, the input flicker pulse waveform amplitude has exceeded the level of the second threshold, therefore, regarding the first time sampling of the flicker pulse rising edge, the first time sampling can be performed based on the moment corresponding to the rising edge of the state signal corresponding to the lowest threshold. For example, Figure 3In the example shown, during the switching process from the lowest threshold 310-1 to the second threshold 310-2 by the threshold providing module, the input flicker pulse waveform amplitude has crossed the level of the second threshold 310-2, so the flicker pulse signal is a valid signal. When the flicker pulse signal is a valid signal, the first time sampling only performs the first time sampling on the state signal corresponding to the lowest threshold voltage 510-1.

[0065] If the first time sampling is successful, step S430 is executed. Otherwise, process S400 returns to the initial state, and step S410 is executed to re-execute the first time sampling based on the time corresponding to the rising edge of the state signal corresponding to the lowest threshold.

[0066] Step S430 , performing second time sampling on the moments corresponding to the falling edges of the status signal in descending order.

[0067] In some embodiments, when the first time sampling is successful, the sampling module can sequentially perform the second time sampling on the time corresponding to the falling edge of one or more delay state signals. In some embodiments, the second order can be an order determined from large to small according to the amplitude of one or more thresholds. For example, continue to refer to Figure 3 , among the 8 threshold voltages, the largest threshold voltage after being arranged from small to large is 410-8. After the sampling module completes the first time sampling, the TDC can start the second time sampling according to the state signal corresponding to the threshold voltage 410-8, that is, the TDC collects the time corresponding to the falling edge of the state signal corresponding to the threshold voltage 410-8. When the sampling of the state signal corresponding to the threshold voltage 410-8 is successful, then the threshold providing module selects different thresholds in the second order from large to small, that is, in descending order. Based on this, the comparison module obtains the state signal corresponding to the corresponding threshold voltages 410-7 to 410-1, and the TDC performs time sampling on the time corresponding to the falling edge of the state signal corresponding to the threshold voltages 410-7 to 410-1, thereby completing the second time sampling, and the process S400 can end.

[0068] In an embodiment of the present application, the sampling module is implemented by a circuit including a time-to-digital converter, and the time-to-digital converter implements time sampling.

[0069] It should be noted that the above Figure 4 The description of each step in the embodiment is only for example and explanation, and does not limit the scope of application of this specification. For those skilled in the art, under the guidance of this specification, Figure 4 Various modifications and changes may be made to the various steps in the present invention. However, these modifications and changes are still within the scope of this specification.

[0070] In the embodiment of the present application, the switching of dynamic thresholds is realized by using a threshold providing module to switch between different set thresholds, and only one LVDS comparator of a comparison module can be used to compare the size of the flicker pulse to be processed with the set different thresholds in turn. Compared with the prior art using multiple LVDS comparators, the present application effectively increases the number of sampling points while reducing the number of LVDS comparators, thereby reducing the number of pins, reducing the resource utilization rate of the FPGA chip, and reducing the operating temperature of the FPGA chip, thereby helping to improve the measurement accuracy of the sampling module TDC; at the same time, based on the multi-threshold flicker pulse waveform sampling realized by threshold switching, only one TDC of a sampling module can be used to realize the time sampling of the flicker pulse, realizing the reuse of the sampling module TDC, greatly saving computing resources, effectively reducing energy consumption, and at the same time, the saved resources can improve the accuracy of time sampling, thereby improving system performance. In addition, by realizing multi-threshold flicker pulse waveform sampling by threshold switching, the number of sampling points can be easily increased to improve the subsequent data processing effect.

[0071] Figure 5 is an exemplary flow chart of the signal sampling of digital PET according to other embodiments of the present application. The acquisition of the scintillation pulse to be processed, the characteristics and manifestation of the scintillation pulse, the manifestation of the threshold, and the structure of the comparison module and the sampling module can all be referred to. Figure 2 The embodiment shown in FIG. 1 is not described in detail in this embodiment. Figure 5 As shown, the process S500 of the signal sampling method of digital PET may include the following steps.

[0072] Step S510: presetting at least two groups of thresholds, each group of thresholds including at least two switchable thresholds.

[0073] In one embodiment, each group of thresholds includes at least two switchable thresholds implemented by a threshold providing module, one group of thresholds corresponds to one threshold through the module, the threshold providing module is implemented by a circuit including a threshold control module and a threshold selection module, and the threshold control module controls the threshold selection module in sequence according to the status signal to realize the switching selection of at least two thresholds of each preset group of thresholds.

[0074] In some embodiments, at least two sets of thresholds can be used to compare with the amplitude of the scintillation pulse to be processed. The comparison results can be used for time sampling to determine the time points when the amplitude of the scintillation pulse to be processed crosses the threshold. These time points can be used for waveform recovery in subsequent processing (e.g., image reconstruction) after matching with the corresponding thresholds, such as recovering the area of ​​the waveform, and then obtaining the waveform energy value.

[0075] It should be understood by those skilled in the art that when the threshold is set to be large, such as higher than the maximum amplitude of the signal, the amplitude of the scintillation pulse can never exceed the preset threshold, so the comparison module will not change state; when the threshold is set to be exactly equal to the maximum amplitude of the signal, the comparison module will only change state once. Therefore, generally, those skilled in the art can reasonably set the size and number of the thresholds based on limited experiments, so that the size interval of the thresholds is more reasonable. Generally, 2-8 evenly spaced thresholds are selected, and the collected information is closer to the real state, which can reduce the number of channels while accurately restoring the pulse shape, and improve data processing efficiency. I will not go into details here.

[0076] In some embodiments, the number of thresholds in each group is set to 2-4, and the size of the threshold is set not to exceed the maximum amplitude of the scintillation pulse to be processed, that is, the size of the threshold is within the amplitude of the scintillation pulse to be processed.

[0077] In one embodiment, reference Figure 3 , Figure 3 310 is a schematic diagram of an exemplary relationship between a threshold voltage and a flicker pulse according to some embodiments of the present application, wherein 310 represents a flicker pulse, which may be a flicker pulse to be processed as mentioned in the present application. The waveform of the flicker pulse in the figure shows its characteristics, namely, the rising period is very short, usually only a few nanoseconds, to rise to the highest point. The falling period is relatively long, usually more than 100ns, generally about 200 nanoseconds. Figure 3 In the illustrated embodiment, 8 threshold voltages are set, and 310-1 to 310-8 represent 8 different threshold voltages. It can be seen that the magnitudes of the 8 threshold voltages are all within the amplitude of the flicker pulse. For example, assuming that the amplitude range of the flicker pulse to be processed is 3mV-200mV, the 8 threshold voltages can be 10mV, 50mV, 70mV, 90mV, 110mV, 130mV, 150mV, 170mV, respectively, and the 8 threshold voltages are divided into two groups, the 4 threshold voltages of the first group are 20mV, 40mV, 60mV, 80mV, and the 4 threshold voltages of the second group are 100mV, 120mV, 140mV, 160mV.

[0078] In some embodiments, at least two groups of preset switchable thresholds are implemented by corresponding at least two threshold providing modules, and one threshold providing module corresponds to one group of thresholds. The threshold providing module is implemented by a circuit including a threshold control module and a threshold selection module. The threshold control module controls the threshold selection module to switch and select the preset threshold. In some embodiments, the threshold control module controls the threshold selection module through a control line. In one embodiment, the threshold control module includes a threshold controller, and the threshold selection module includes a data selector MUX (multiplexer). In the present application, Figure 3 In one embodiment, two threshold providing modules are specifically used to correspond to two groups of thresholds respectively. Specifically, two data selectors MUX4 can be used, and each MUX4 presets four switchable thresholds. Through the two data selectors MUX4, eight switchable thresholds can be preset. After the switchable thresholds are preset, the threshold controller controls MUX4 to switch and select at least four thresholds, and the switched and selected thresholds are transmitted to the LVDS comparator for amplitude comparison. The threshold controller controls the switching and selection operation of the threshold according to the comparison result of the amplitude of the flicker pulse to be processed and the threshold currently selected by each data selector MUX4, and the threshold controller controls MUX4 through the control line.

[0079] In the embodiment of the present application, by using a threshold providing module to switch between different set thresholds to achieve dynamic threshold switching, the number of sampling points can be easily increased to improve the subsequent image reconstruction effect. Moreover, through threshold switching, it is possible to subsequently use only one comparison module LVDS comparator to sequentially compare the size of the flicker pulse to be processed with the set different thresholds, and only use one sampling module TDC for time sampling, thereby improving system performance. In addition, by using at least two threshold modules to preset at least two groups of thresholds, each group of thresholds includes at least two switchable thresholds, and each group of thresholds includes a minimum threshold, and the minimum threshold of each group can be used as a rising edge sampling point, thereby increasing the number of sampling points.

[0080] Step S520: at least two comparison modules corresponding to at least two groups of thresholds are set in parallel.

[0081] At least two comparison modules correspond to at least two groups of thresholds one by one, and each comparison module is arranged in parallel and works independently of each other. Each comparison module is connected to the corresponding threshold control module for communication. The pulse to be processed is connected to the positive end of at least two comparison modules respectively, and the threshold switched and selected in each group of thresholds is connected to the negative end of the comparison module, and at least two comparison modules are connected to the same sampling module.

[0082] Step S530, at the same time, each comparison module sequentially compares the flicker pulse to be processed with at least two thresholds of each corresponding group, and determines at least two state signals corresponding to the at least two thresholds of each group when the flicker pulse to be processed crosses the threshold.

[0083] In some embodiments, each comparison module is used to sequentially compare the corresponding groups of at least two preset thresholds with the amplitude of the scintillation pulse to be processed.

[0084] It can be known that for the setting of the threshold, under normal circumstances, the flicker pulse can cross the same threshold twice. One is in the rising stage of the flicker pulse, the amplitude of the flicker pulse can cross the threshold from low to high and be higher than the threshold. The other is in the falling stage of the flicker pulse, the amplitude of the flicker pulse can cross the threshold from high to low and be lower than the threshold. Regardless of which one crosses, the comparison module can generate a jump and record the time when the amplitude crosses the threshold. For example Figure 3 The schematic diagram of the principle of multi-voltage threshold sampling is shown. In this example, two groups of thresholds are provided, each with 4 thresholds. For the first group of thresholds, the lowest threshold is 310-1 and the highest threshold is 310-4. In the rising stage, the flicker pulse 310 will first cross and be higher than the threshold voltage 310-1, and then continue to go up, cross and be higher than the threshold voltage 310-2, and then successively cross and be higher than the threshold voltages 310-3 to 310-4. In the falling stage, the flicker pulse 310 will first cross and be lower than the threshold voltage 310-4. Then continue to go down, cross and be lower than the threshold voltage 310-3, and then successively cross and be lower than the threshold voltages 310-2 to 310-1. In the whole process, the pulse voltage 310 can undergo 16 state changes relative to the above 8 threshold voltages. For the second set of thresholds, the lowest threshold is 310-5 and the highest threshold is 310-8. In the rising stage, the flicker pulse 310 will first cross and be higher than the threshold voltage 310-5, then continue to go up, cross and be higher than the threshold voltage 310-6, and then cross and be higher than the threshold voltages 310-7 to 310-8 in sequence. In the falling stage, the flicker pulse 310 will first cross and be lower than the threshold voltage 310-8. Then continue to go down, cross and be lower than the threshold voltage 310-7, and then cross and be lower than the threshold voltages 310-6 to 310-5 in sequence. In the whole process, the pulse voltage 310 can undergo 16 state changes relative to the above 8 threshold voltages.

[0085] In some embodiments, the comparison module can compare the flicker pulse to be processed with the current threshold selected by the switch, and output a state signal. The state signal can indicate the state change of the pulse to be processed relative to the threshold (for example, from below the threshold to crossing and above the threshold or from above the threshold to crossing and below the threshold). The time sampling involved in the subsequent part of this application can refer to the time measurement of the moment corresponding to the state signal. Multiple state signals correspond to threshold voltages 310-1 to 310-8 respectively. Each state signal includes a rising edge and a falling edge. For example, the rising edges of the two sets of thresholds correspond to the moments when the flicker pulse to be processed crosses the threshold voltages 310-1 to 310-4 and 310-1 to 310-8 respectively at the rising edge of the pulse, and the falling edges correspond to the moments when the flicker pulse to be processed crosses the threshold voltages 310-8 to 310-5 and 310-4 to 310-1 respectively at the falling edge of the pulse. The rising edge indicates that the flicker pulse to be processed crosses and is higher than the threshold voltage from bottom to top, and the falling edge indicates that the flicker pulse to be processed crosses and is lower than the threshold voltage from top to bottom. The moment corresponding to the position of the rising edge and the falling edge can be the moment when the scintillation pulse crosses the threshold voltage. It should be understood by those skilled in the art that the above embodiments only use voltage thresholds and voltage state signals as examples, and other thresholds and state changes are generally applicable in principle and will not be described in detail here.

[0086] Continue to return to reference Figure 3 ,from Figure 3 It can be seen that due to the characteristics of the scintillation pulse, the rising edges of the state signal corresponding to each threshold voltage are very close, so that the time corresponding to the position of each rising edge is also very close. This is not conducive to the subsequent data processing process, for example, the process of image reconstruction based on the time sampling result of the scintillation pulse waveform. Therefore, in an example of the present application, in order to be able to accurately collect as much rising edge information as possible, the present application sets the threshold to at least two groups, each group has a minimum threshold, and the information of the minimum threshold can be accurately collected. In this embodiment, the state signal includes a rising edge indicating that the scintillation pulse to be processed crosses at least part of the thresholds including the minimum threshold in each group of at least two thresholds and a falling edge that crosses all thresholds in each group of at least two thresholds.

[0087] In some embodiments of the present application, a comparison module is used to compare the flicker pulse to be processed with at least two thresholds of each corresponding group in each channel, including: switching between at least two thresholds of each group in turn according to a status signal, so that the comparison module corresponding to the threshold of this group compares the size of the pulse to be processed with different thresholds of the at least two thresholds in turn.

[0088] Among them, switching between at least two thresholds in each group is performed in sequence according to the state signal, which is realized by the threshold providing module. Specifically, each threshold providing module selects and controls the threshold of the negative end of the LVDS comparator corresponding to the threshold providing module according to the state signal output by the LVDS comparator.

[0089] In one embodiment, taking setting two groups of thresholds as an example, a flicker pulse to be processed is input to the positive terminal of an LVDS comparator, and the threshold voltage switched and selected by a corresponding threshold providing module is input to the corresponding negative terminal of the LVDS comparator. When the level of the flicker pulse to be processed is higher than the threshold level currently switched and selected, the state signal output by the LVDS comparator is 1, and when the level of the flicker pulse to be processed is lower than the threshold level currently switched and selected, the state signal output by the LVDS comparator is 0. The result output by the LVDS comparator is connected to the threshold control module of the corresponding threshold providing module as a feedback input, and the threshold controller of the threshold control block controls the MUX of the threshold selection module through the control line according to the feedback input signal to switch the selected threshold in sequence according to the rising edge order (i.e. ascending order) or the falling edge order (i.e. descending order). At the same time, another flicker pulse to be processed is input to the positive terminal of another LVDS comparator, and the threshold voltage switched and selected by the corresponding another threshold providing module is input to the corresponding negative terminal of another LVDS comparator. When the level of the flicker pulse to be processed is higher than the threshold level currently switched and selected, the state signal of the output of the other LVDS comparator is 1, and when the level of the flicker pulse to be processed is lower than the threshold level currently switched and selected, the state signal of the output of the other LVDS comparator is 0. The result output by the other LVDS comparator is connected to the threshold control module of the corresponding threshold providing module as a feedback input. The threshold controller of the threshold control block controls the MUX of the threshold selection module through the control line according to the feedback input signal to switch the selected threshold in sequence according to the rising edge order (i.e. ascending order) or the falling edge order (i.e. descending order).

[0090] In one example, during the rising edge sampling process of each group of thresholds, when the result of the LVDS comparator output is 0, the threshold controller controls the MUX to continue selecting the current threshold; when the result of the LVDS comparator output is 1, the rising edge sampling is completed, and the maximum threshold is immediately switched to perform falling edge sampling. This threshold is the threshold at the top of the sorting of falling edge sampling, that is, the maximum threshold for falling edge sampling. During the falling edge sampling process, when the result of the LVDS comparator output is 1, the threshold controller controls the MUX to continue selecting the current threshold; when the result of the LVDS comparator output is 0, the threshold controller controls the MUX to switch to the next threshold according to the falling edge sequence.

[0091] Each comparison module is implemented by a circuit including a comparator, which sequentially compares the pulse to be processed with the magnitudes of each threshold value switched and selected from a corresponding set of threshold values.

[0092] Step S540: Use the same sampling module to perform time sampling on the state signal in sequence to obtain corresponding flicker pulse threshold-time pairs.

[0093] In some embodiments, time sampling may be time digital sampling of the time corresponding to the position of the rising edge and the falling edge of the state signal. In the present application, the terms "time sampling", "time digital sampling" and "time measurement" may be used interchangeably to refer to the operation of determining the time corresponding to the position of the rising edge and the falling edge of each state signal after delay processing.

[0094] In some embodiments, the sampling module can sample the rising edge and the falling edge of the above delayed state signal in a certain sampling order. In some embodiments, the sampling module can be implemented by a circuit including a time-to-digital converter (TDC), which is communicatively connected to at least two comparison modules, and the time-to-digital converter implements time sampling. The sampling module can use the TDC to sample the moment corresponding to the position of the rising edge or the falling edge of the input state signal.

[0095] In some embodiments, the flicker pulse threshold-time pair may include the state change time obtained by time sampling the state signal and the amplitude of the threshold corresponding to the state signal. For example, for a certain threshold V1, the comparison with the flicker pulse to be processed can obtain the state signal, and the TDC can obtain two moments by time measurement of the state signal, including the moment T1 corresponding to the position of the rising edge and the moment T2 corresponding to the position of the falling edge. T1 and T2 can be called state change time, and the flicker pulse threshold-time pair may include (V1, T1) and (V1, T2).

[0096] In some embodiments, the scintillation pulse threshold-time pair can be transmitted to other components for further processing. For example, the sampling result can be transmitted to an image processing component related to the PET device through a wired or wireless communication method for subsequent PET image reconstruction.

[0097] It should be noted that the above Figure 5 The description of each step in the embodiment is only for example and explanation, and does not limit the scope of application of this specification. For those skilled in the art, under the guidance of this specification, Figure 5Various modifications and changes may be made to the various steps in the present invention. However, these modifications and changes are still within the scope of this specification.

[0098] Based on the multi-threshold scintillation pulse waveform sampling realized by threshold switching, the time sampling of the scintillation pulse can be realized by only one TDC of one sampling module, which realizes the reuse of the sampling module TDC, greatly saves computing resources, effectively reduces energy consumption, and at the same time, the saved resources can improve the accuracy of time sampling, thereby improving system performance. In addition, by realizing multi-threshold scintillation pulse waveform sampling by threshold switching, the number of sampling points can be easily increased, and the subsequent data processing effect can be improved.

[0099] Figure 6 FIG. 1 is an exemplary flow chart of sequentially sampling state signals according to some embodiments of the present application. Figure 6 As shown, the process S600 of sequentially sampling the state signal may include the following operations:

[0100] Step S610 , performing first time sampling on the moments corresponding to rising edges of a plurality of state signals in sequence based on a first order.

[0101] In some embodiments, the first order may be an order determined from small to large according to the lowest threshold values ​​of each group of threshold values ​​of at least two groups of threshold values. The sampling module may first perform the first time sampling on the moment corresponding to the rising edge of the delay state signal corresponding to the lowest threshold value in the first order. For example, referring to Figure 3 In the two groups of threshold voltages, the lowest threshold of the first group of thresholds is 310-1, and the lowest threshold of the second group of thresholds is 310-5. The lowest threshold voltage 310-1 is ranked first in ascending order; the lowest threshold voltage 310-5 is ranked second. After each state signal 310-1 and 310-5 is output from the comparison module, it will be input to the TDC of the sampling module for time sampling.

[0102] In step S610, the state signal 310-5 is generated after 310-1, and the state signal 310-1 is first transmitted to the TDC, and the TDC first performs time sampling on the moment corresponding to the rising edge of the state signal corresponding to the first lowest threshold 310-1. Then, the TDC performs time sampling on the moment corresponding to the rising edge of the state signal corresponding to the second lowest threshold 310-5 in accordance with the first order, thereby completing the first time sampling.

[0103] Step S620, determining whether the first time sampling is successful.

[0104] In some embodiments, the TDC of the sampling module 840 can simultaneously output a feedback when time sampling the delay status signal. The feedback can include one or more combinations of numbers, letters, symbols, etc. For example, the feedback can be 1 or 0. 1 indicates that the flicker pulse crosses and is higher than the threshold, and 0 indicates that the flicker pulse crosses and is lower than the threshold voltage. In this way, when sampling the time corresponding to the rising edge of the delay status signal, if the output feedback is 1, it means that the sampling is successful. Conversely, if the output feedback is 0, it means that the sampling failed. In one embodiment of the present application, when the delay status signal corresponding to the lowest threshold of each group of thresholds is successfully sampled, the first time sampling is successful. In the present application Figure 3 In the real-time example, when the TDC completes the first time sampling of the delay status signal corresponding to the lowest threshold voltage 310-1 of the first group of thresholds, the feedback output by the TDC is 1, and the first time sampling of the delay status signal corresponding to the lowest threshold voltage 310-5 of the second group of thresholds is completed, the feedback output by the TDC is 1, indicating that the first time sampling is successful.

[0105] In one embodiment, performing first time sampling on the moments corresponding to rising edges of a plurality of state signals in sequence based on a first order includes:

[0106] After performing a first time sampling on the moment corresponding to the rising edge of the delayed state signal corresponding to the lowest threshold value at the first position in the sorting, determining whether the flicker pulse to be processed is a valid signal;

[0107] If so, synchronously output the feedback signal and perform first time sampling at the moment corresponding to the rising edge of the state signal corresponding to the other lowest threshold value in the at least two groups of threshold values ​​based on the first order;

[0108] If not, return to the initial state and re-execute the first time sampling.

[0109] In an embodiment of the present application, the smallest lowest threshold among the at least two preset thresholds is more critical, and the time corresponding to the corresponding status signal is usually used to judge the arrival time of the input ray particles received by the front-end detector. It is usually set relatively low, at the order of several mV, and is prone to false triggering. It is necessary to further confirm whether the scintillation pulse to be processed is a valid signal through subsequent thresholds.

[0110] In one embodiment of the present application, determining whether a scintillation pulse to be processed is a valid signal includes the following steps:

[0111] In one embodiment, determining whether the scintillation pulse to be processed is a valid signal comprises the following steps:

[0112] Set a verification group, and take the group with the lowest threshold value that ranks first among at least two groups of threshold values ​​as the verification group;

[0113] Setting a verification threshold, taking the threshold close to the lowest threshold among at least two thresholds of the verification group as the verification threshold;

[0114] A comparison module corresponding to the verification group is used to compare the flicker pulse to be processed with the verification threshold. If the verification status signal that the flicker pulse to be processed crosses the verification threshold is not obtained, it is a false trigger signal; if the verification status signal that the flicker pulse to be processed crosses the verification threshold is obtained, it is a valid signal.

[0115] In one embodiment of the present application, it is usually possible to determine whether the rising edge position is a valid trigger by whether the scintillation pulse waveform crosses a higher second threshold. The rising edge sampling of the scintillation pulse waveform first determines whether the signal passes through the minimum threshold, completes the first time sampling of the minimum threshold, and then eliminates the false trigger signal by whether it passes the second threshold, and obtains a valid rising edge starting point as the key data of the subsequent particle arrival time.

[0116] In some embodiments, the rising edge period of the flicker pulse is very short, usually reaching its peak in just a few nanoseconds. The falling edge period is longer, usually exceeding 100ns, and generally around 200 nanoseconds. Therefore, after completing the first time sampling of the lowest threshold of the group with the smallest lowest threshold in at least two groups of thresholds, during the process of the threshold providing module switching the lowest threshold of the group to the second threshold, the input flicker pulse waveform amplitude has exceeded the level of the second threshold. Therefore, after the threshold providing module completes the threshold switching from the lowest threshold to the second threshold, it can directly determine whether it is a valid signal. If it is a false trigger, it returns to the starting state. If it is a valid signal, the first time sampling is performed based on the first order at the moment corresponding to the rising edge of the delay state signal corresponding to the other lowest thresholds in at least two groups of thresholds. For example, Figure 3 In the example shown, compared with the first group of thresholds 310-1 to 310-4 and the second group of thresholds 310-5 to 310-8, the lowest threshold 310-1 of the first group of thresholds is smaller than the lowest threshold 310-5 of the second group of thresholds. Therefore, the first group of thresholds is taken as the verification group. After the first time sampling of the lowest threshold 310-1 of the first group of thresholds, the threshold providing module switches the lowest threshold 310-1 of the group to the verification threshold, i.e., the second threshold 310-2. If the verification status signal that the flicker pulse to be processed crosses the verification threshold second threshold 310-2 is not obtained, it is a false trigger signal; if the verification status signal that the flicker pulse to be processed crosses the verification threshold second threshold 310-2 is obtained, it is a valid signal. Then, the first time sampling is performed at the moment corresponding to the rising edge of the delay status signal corresponding to the lowest threshold 310-5 of the second group of thresholds. After completion, the first time sampling is completed.

[0117] When the time sampling of the state signal corresponding to the lowest threshold of each group of thresholds is successful, that is, when the first time sampling is successful, the process S600 can proceed to step S630. Otherwise, the process S600 will return to step S610 and re-perform the first time sampling at the moments corresponding to the rising edges of the multiple state signals in sequence based on the first order.

[0118] Step S630 , performing second time sampling on the moments corresponding to the falling edges of the status signal in sequence based on the second order.

[0119] In some embodiments, when the first time sampling is successful, the sampling module can sequentially perform the second time sampling at the time corresponding to the falling edge of the state signal. In some embodiments, the second order can be an order determined from large to small according to the threshold values ​​of at least two groups of thresholds. For example, continue to refer to Figure 3 , the eight threshold voltages are divided into two groups, the first group is 310-1 to 310-4, arranged from large to small as 310-4, 310-3, 310-2, 310-1; the second group is 310-5 to 310-8, arranged from large to small as 310-8, 310-7, 310-6, 310-5. The highest threshold of the first group of thresholds is 310-4, and the highest threshold of the second group of thresholds is 310-8, and threshold 310-8 is greater than 310-4. After the sampling module completes the first time sampling, the TDC can start the second time sampling according to the state signal corresponding to the maximum value of the highest thresholds in each group, for example, the second time sampling is started according to the state signal corresponding to the highest threshold 310-8 of the second group of thresholds, and the TDC collects the time corresponding to the falling edge ⑤' of the state signal 310-8. When the state signal corresponding to the highest threshold 310-8 is sampled successfully, the TDC then performs time sampling on the moments corresponding to the falling edges of the state signals corresponding to the thresholds 310-7 to 310-1 in the second order of the thresholds in each group from large to small, thereby completing the second time sampling and the process S600 can end.

[0120] In the embodiment of the present application, at least two groups of thresholds are preset by using at least two threshold modules, each group of thresholds includes at least two thresholds that can be switched and selected, and each group of thresholds includes a minimum threshold, and the minimum threshold of each group can be used as a rising edge sampling point, thereby increasing the number of sampling points; given that each group of thresholds can realize dynamic threshold switching, only at least two comparison modules corresponding to the number of threshold groups (i.e., the number of threshold providing modules) can be used to sequentially compare the size of the flicker pulse to be processed with the set different thresholds. Compared with the prior art that uses multiple LVDS comparators corresponding to the number of preset thresholds, the present application effectively increases the number of sampling points while reducing the number of LVDS comparators, thereby reducing the number of pins, reducing the resource utilization rate of the FPGA chip, and reducing the operating temperature of the FPGA chip, thereby helping to improve the measurement accuracy of the sampling module TDC; based on the multi-threshold flicker pulse waveform sampling realized by threshold switching, only one TDC of one sampling module can be used to realize the time sampling of the flicker pulse, realizing the reuse of the sampling module TDC, greatly saving computing resources, and effectively reducing energy consumption. At the same time, the saved resources can improve the accuracy of time sampling, thereby improving system performance. In addition, by implementing multi-threshold flicker pulse waveform sampling through threshold switching, the number of sampling points can be easily increased, thereby improving the subsequent data processing effect.

[0121] It should be noted that the above Figure 6 The description of each step in the embodiment is only for example and explanation, and does not limit the scope of application of this specification. For those skilled in the art, under the guidance of this specification, Figure 6 Various modifications and changes may be made to the various steps in the present invention. However, these modifications and changes are still within the scope of this specification.

[0122] As an example, the time difference / time interval corresponding to each state signal can be obtained through the delay module, and then the time difference / time interval can be superimposed on the state signal to postpone the positions of its rising edge and falling edge at the same time, thereby achieving the purpose of staggering the state signals.

[0123] In some embodiments, performing delay processing on multiple state signals refers to performing delay processing on a portion of the state signals, for example, performing delay processing on at least one group of state signals other than a group of state signals with the smallest minimum threshold in each group of thresholds, so that the state signals corresponding to the lowest thresholds of each group, i.e., the rising edges, are staggered. Staggering means that the rising edge or falling edge jump time points of the state signals are spaced apart so that they can be recognized by the minimum recognition unit of the time-to-digital converter. Preferably, after the delay processing, the time interval between the rising edges of the state signals corresponding to the lowest thresholds of each group and / or the time interval between the corresponding falling edges is greater than the minimum recognition unit of the time-to-digital converter. The minimum recognition unit can have various sizes according to different technical means. For example, according to the current technical level, a time interval greater than 10ns can usually meet the minimum recognition unit requirements of the time-to-digital converter in the prior art.

[0124] Figure 7 1 is an exemplary block diagram of a digital PET signal sampling device according to some embodiments of this specification. The digital PET signal sampling device can achieve high-performance pulse sampling. Figure 7 As shown, the signal sampling device 700 may include an acquisition module 710 for acquiring a flicker pulse to be processed; a threshold providing module 720 for switching and selecting at least two preset thresholds; a comparison module 730 for sequentially comparing the flicker pulse to be processed with at least two thresholds to determine at least two state signals corresponding to the at least two thresholds when the flicker pulse to be processed crosses the threshold; and a sampling module 740 for sequentially performing time sampling on at least two state signals to obtain corresponding flicker pulse threshold-time pairs.

[0125] The acquisition module 710 can be used to acquire the pulse to be processed. The acquisition module 1010 can acquire the scintillation pulse to be processed by communicating with the detector.

[0126] The threshold providing module 720 can be used to provide at least two thresholds that can be switched and selected. The threshold providing module includes a threshold control module and a threshold selection module. The threshold control module sequentially controls the threshold selection module according to the state signal to realize the switching selection of at least two preset thresholds. In some embodiments, the threshold control module controls the threshold selection module through a control line. In one embodiment, the threshold control module includes a threshold controller, and the threshold selection module includes a data selector MUX (multiplexer). In the embodiment of the present application, a data selector MUX8 or two data selectors MUX4 arranged in parallel can be used to preset 8 thresholds that can be switched and selected. After presetting at least two thresholds that can be switched and selected, the threshold controller controls the data selector MUX to switch and select at least two thresholds, and the switched and selected thresholds are transmitted to the LVDS comparator for amplitude comparison. The threshold controller controls the switching and selection operation of the threshold according to the comparison result between the amplitude of the flicker pulse to be processed and the threshold currently selected by the data selector MUX, and the threshold controller controls MUX through the control line.

[0127] The comparison module 730 can be used to compare the flicker pulse to be processed with at least two thresholds in sequence, and determine at least two state signals corresponding to at least two thresholds respectively when the flicker pulse to be processed crosses the threshold. The comparison module includes a comparator, which compares the flicker pulse to be processed with the size of each threshold selected by the threshold providing module from at least two thresholds in sequence. In one example, the comparison module 730 can be implemented by a circuit including a low-voltage differential signal (LVDS) comparator. In one embodiment of the present application, the comparison module 730 can be implemented by a circuit including a low-voltage differential signal (LVDS) comparator. As an example, the flicker pulse generated by the photodetector can be input to the p-end of the LVDS pin (also referred to as the positive end), and the threshold voltage can be input to the n-end of the LVDS pin (also referred to as the negative end), thereby completing the comparison of the pulse waveform and the threshold voltage. Using an LVDS comparator, the flicker pulse to be processed can be compared with at least two preset switchable thresholds in sequence. In this way, the number of input pins is effectively reduced and the system performance is improved.

[0128] After comparing the flicker pulse to be processed with the switched selected threshold, the comparison module 730 outputs a state signal. The state signal may indicate a state change of the flicker pulse to be processed relative to the threshold (e.g., from below the threshold voltage to crossing and above the threshold voltage or from above the threshold voltage to crossing and below the threshold voltage). In one embodiment, the state signal includes a rising edge indicating that the flicker pulse to be processed crosses at least part of the thresholds including the lowest threshold among at least two thresholds and a falling edge that crosses all of the at least two thresholds.

[0129] The sampling module 740 can perform time sampling on the state signal in a certain sampling order to obtain one or more corresponding flicker pulse threshold-time pairs. The sampling module 740 includes a time-to-digital converter (TDC), which is connected to the comparison module 1030 in communication, and the time-to-digital converter implements time sampling. The sampling module 740 can use the TDC to sample the moment corresponding to the position of the rising edge or falling edge of the input state signal.

[0130] In some embodiments, the sampling module 740 can be used to perform a first time sampling on the moment corresponding to the rising edge of the status signal based on the lowest threshold; determine whether the first time sampling is successful; and perform a second time sampling on the moment corresponding to the falling edge of the status signal in descending order.

[0131] The lowest threshold is the threshold ranked first in the order determined by sorting at least two thresholds from small to large. If the first time sampling is successful, the sampling module 740 can perform the second time sampling on the corresponding moment of the falling edge of the state signal corresponding to the threshold voltage ranked first in the order of thresholds from large to small. That is, starting from the highest threshold, the second time sampling is performed on the delayed state signal corresponding to each threshold in the order of thresholds from large to small, that is, in descending order, until the state signal corresponding to the threshold at the last position in the second order completes the second time sampling. If unsuccessful, the second time sampling is re-executed. In some embodiments, the sampling module 740 can first obtain sampling feedback based on the lowest threshold for the moment corresponding to the rising edge of the state signal to perform the first time sampling. If it is determined that the sampling feedback indicates that the first time sampling is successful, the second time sampling is continued to be performed on the moment corresponding to the falling edge of the state signal in descending order.

[0132] The sampling module is also used to determine whether the signal to be processed is valid after performing the first time sampling at the moment corresponding to the rising edge of the state signal based on the minimum threshold, and control the time sampling process accordingly, including: determining whether the flicker pulse to be processed is a valid signal; if so, synchronously outputting a feedback signal and starting to switch to performing the second time sampling at the moment corresponding to the falling edge of the state signal in descending order; if not, returning to the initial state and re-executing the first time sampling.

[0133] The flicker pulse threshold-time pair includes the state change time obtained by time sampling of the state signal and the threshold corresponding to the state change time. Figure 2 , Figure 5 The embodiment of the signal sampling method of the digital PET shown is not described in detail here.

[0134] In the embodiment of the present application, the switching of dynamic thresholds is realized by using a threshold providing module to switch between different set thresholds, and only one LVDS comparator of a comparison module can be used to compare the size of the flicker pulse to be processed with the set different thresholds in turn. Compared with the prior art using multiple LVDS comparators, the present application effectively increases the number of sampling points while reducing the number of LVDS comparators, thereby reducing the number of pins, reducing the resource utilization rate of the FPGA chip, and reducing the operating temperature of the FPGA chip, thereby helping to improve the measurement accuracy of the sampling module TDC; at the same time, based on the multi-threshold flicker pulse waveform sampling realized by threshold switching, only one TDC of a sampling module can be used to realize the time sampling of the flicker pulse, realizing the reuse of the sampling module TDC, greatly saving computing resources, effectively reducing energy consumption, and at the same time, the saved resources can improve the accuracy of time sampling, thereby improving system performance. In addition, by realizing multi-threshold flicker pulse waveform sampling by threshold switching, the number of sampling points can be easily increased to improve the subsequent data processing effect.

[0135] Figure 8 FIG. 1 is an exemplary module diagram of a signal sampling device for digital PET according to some embodiments of this specification. Figure 8As shown, the signal sampling device 800 may include: an acquisition module 810, which is used to acquire a flicker pulse to be processed; at least two threshold providing modules 820, wherein each threshold providing module is used to switch and select at least two preset thresholds; at least two comparison modules 830 arranged in parallel, which correspond to the at least two threshold providing modules one by one, wherein each comparison module is used to sequentially compare the flicker pulse to be processed with at least two thresholds provided by the corresponding threshold providing module, and determine at least two state signals corresponding to the at least two thresholds respectively when the flicker pulse to be processed crosses the threshold; a sampling module 840, which is used to sequentially sample the state signal in time and acquire the corresponding flicker pulse threshold-time pair. At least two comparison modules 830 are connected to one sampling module 840. Multiple thresholds can be compared sequentially through each comparison module 830, and only one sampling module is provided, which reduces the number of pins and improves system performance.

[0136] In some embodiments of the present application, the comparison module 830 includes a comparator, which sequentially compares the magnitudes of the flicker pulse to be processed with the magnitudes of each threshold value switched and selected from at least two threshold values ​​provided by the corresponding threshold providing module.

[0137] In some embodiments of the present application, the sampling module 840 can perform time sampling on the state signal in a certain sampling order to obtain one or more corresponding flicker pulse threshold-time pairs. The sampling module 840 includes a time-to-digital converter (TDC), and the time-to-digital converter TDC is communicatively connected to at least two comparison modules 830, and the time-to-digital converter implements time sampling. The sampling module 840 can use the TDC to sample the moment corresponding to the position of the rising edge or falling edge of the input state signal.

[0138] In some embodiments, the sampling module 840 is used to: perform first time sampling on the moments corresponding to the rising edges of multiple state signals in sequence based on a first order; determine whether the first time sampling is successful; and perform second time sampling on the moments corresponding to the falling edges of the state signals in sequence based on a second order.

[0139] The first order may be an order determined from small to large according to the lowest threshold values ​​of each group of threshold values ​​of at least two groups of threshold values. The sampling module may first perform the first time sampling at the moment corresponding to the rising edge of the delay state signal corresponding to the lowest threshold value in the first order. For example, referring to Figure 3, among the two groups of threshold voltages, the lowest threshold of the first group of thresholds is 310-1, and the lowest threshold of the second group of thresholds is 310-5. The lowest threshold voltage 310-1 is ranked first in ascending order; the lowest threshold voltage 310-5 is ranked second. After the state signals 310-1 and 310-5 are output from the comparison module, they will be input to the TDC of the sampling module for time sampling. The TDC first performs time sampling on the moment corresponding to the rising edge of the state signal corresponding to the first lowest threshold 310-1. Then, the TDC performs time sampling on the moment corresponding to the rising edge of the state signal corresponding to the second lowest threshold 310-5 in the first order, thereby completing the first time sampling.

[0140] In one embodiment, when the sampling module performs the first time sampling on the moments corresponding to the rising edges of multiple state signals in sequence based on the first order, it is also used to determine whether the signal to be processed is valid, and control the time sampling process accordingly, including: after performing the first time sampling on the moment corresponding to the rising edge of the delayed state signal corresponding to the lowest threshold in the first order, determine whether the flicker pulse to be processed is a valid signal; if so, synchronously output a feedback signal and perform the first time sampling on the moment corresponding to the rising edge of the state signal corresponding to other lowest thresholds in at least two groups of thresholds based on the first order; if not, return to the initial state and re-execute the first time sampling.

[0141] The flicker pulse threshold-time pair includes the state change time obtained by time sampling of the state signal and the threshold corresponding to the state change time. Figure 2 , Figure 5 The embodiment of the signal sampling method of the digital PET shown is not described in detail here.

[0142] In the embodiment of the present application, at least two groups of thresholds are preset by using at least two threshold modules, each group of thresholds includes at least two thresholds that can be switched and selected, and each group of thresholds includes a minimum threshold, and the minimum threshold of each group can be used as a rising edge sampling point, thereby increasing the number of sampling points; given that each group of thresholds can realize dynamic threshold switching, only at least two comparison modules corresponding to the number of threshold groups (i.e., the number of threshold providing modules) can be used to sequentially compare the size of the flicker pulse to be processed with the set different thresholds. Compared with the prior art that uses multiple LVDS comparators corresponding to the number of preset thresholds, the present application effectively increases the number of sampling points while reducing the number of LVDS comparators, thereby reducing the number of pins, reducing the resource utilization rate of the FPGA chip, and reducing the operating temperature of the FPGA chip, thereby helping to improve the measurement accuracy of the sampling module TDC; based on the multi-threshold flicker pulse waveform sampling realized by threshold switching, only one TDC of one sampling module can be used to realize the time sampling of the flicker pulse, realizing the reuse of the sampling module TDC, greatly saving computing resources, and effectively reducing energy consumption. At the same time, the saved resources can improve the accuracy of time sampling, thereby improving system performance. In addition, by implementing multi-threshold flicker pulse waveform sampling through threshold switching, the number of sampling points can be easily increased, thereby improving the subsequent data processing effect.

[0143] The apparatus in the embodiments of the present application may be combined with the method features in the embodiments of the present application, and vice versa.

[0144] In one embodiment, a detector device is also provided. The detector device includes: a detector and a signal sampling device provided in any of the above embodiments, wherein the detector is configured to detect rays and output a scintillation pulse signal to be processed to the signal sampling device for digital sampling processing. The types of detectors are specifically described in the method and device embodiments, and are not described in detail here.

[0145] In one embodiment, a digitizing device is further provided, which includes the signal sampling device provided in any of the above embodiments.

[0146] In one embodiment, a digitization device is also provided, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the computer program is executed by the processor, the steps of the signal sampling method provided in any of the above embodiments are implemented.

[0147] In one embodiment, a computer-readable storage medium is further provided, characterized in that a computer program is stored on the storage medium, and when the computer program is executed by a processor, the steps of the signal sampling method provided in any of the above embodiments are implemented.

[0148] The basic concepts have been described herein. It is obvious to those skilled in the art that the above detailed disclosure is merely an example and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to this specification. Such modifications, improvements and amendments are suggested in this specification, so such modifications, improvements and amendments still fall within the spirit and scope of the exemplary embodiments of this specification.

[0149] At the same time, this specification uses specific words to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this specification can be appropriately combined.

[0150] In addition, it will be understood by those skilled in the art that various aspects of this specification may be illustrated and described by a number of patentable categories or situations, including any new and useful process, machine, product or combination of substances, or any new and useful improvements thereto. Accordingly, various aspects of this specification may be performed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". In addition, various aspects of this specification may be represented as a computer product located in one or more computer-readable media, which includes computer-readable program code.

[0151] A computer storage medium may include a propagated data signal containing computer program code, for example, in baseband or as part of a carrier wave. The propagated signal may be in a variety of forms, including electromagnetic, optical, etc., or a suitable combination. A computer storage medium may be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction execution system, device or equipment to communicate, propagate or transmit the program for use. The program code on the computer storage medium may be transmitted via any suitable medium, including radio, cable, fiber optic cable, RF, or similar media, or any combination of the above media.

[0152] The computer program codes required for the operation of the various parts of this specification 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 language, Visual Basic, Fortran 3003, Perl, COBOL 3002, PHP, ABAP, dynamic programming languages ​​such as Python, Ruby and Groovy, or other programming languages. The program code can be run entirely on the user's computer, or run on the user's computer as an independent software package, or run partially on the user's computer and partially on a remote computer, or run 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 form, such as a local area network (LAN) or a 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).

[0153] In addition, unless expressly stated in the claims, the order of the sequences described in this specification, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some invention embodiments that are currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this specification. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only by software solutions, such as installing the described system on an existing server or mobile device.

[0154] Similarly, it should be noted that in order to simplify the description disclosed in this specification and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this specification, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the subject matter of this specification are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0155] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate 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 change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of this specification are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0156] Each patent, patent application, patent application disclosure, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this specification are hereby incorporated by reference in their entirety. Except for application history documents that are inconsistent with or conflicting with the contents of this specification, documents that limit the broadest scope of the claims of this specification (currently or later attached to this specification) are also excluded. It should be noted that if the descriptions, definitions, and / or use of terms in the materials attached to this specification are inconsistent or conflicting with the contents described in this specification, the descriptions, definitions, and / or use of terms in this specification shall prevail.

[0157] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A digital PET signal sampling method, characterized in that: The signal sampling method comprises: At least two threshold values ​​for switchable selection are preset; Using a same circuit including a comparator to sequentially compare the flicker pulse to be processed with the at least two thresholds, and determining at least two state signals corresponding to the at least two thresholds respectively when the flicker pulse to be processed crosses the threshold; The same sampling module is used to perform time sampling on the at least two state signals in sequence to obtain corresponding flicker pulse threshold-time pairs.

2. The signal sampling method of digital PET according to claim 1, characterized in that: The at least two preset switchable thresholds are implemented by a threshold providing module, and the threshold providing module is implemented by a circuit including a threshold control module and a threshold selection module. The threshold control module controls the threshold selection module in sequence according to the state signal to realize the switching selection of the at least two preset thresholds.

3. The signal sampling method of digital PET according to claim 1, characterized in that: The threshold is set to a value not exceeding the maximum amplitude of the scintillation pulse to be processed.

4. The signal sampling method of digital PET according to claim 1, characterized in that: The number of the thresholds is set to 2-8.

5. The signal sampling method of digital PET according to claim 1, characterized in that: Using the same circuit including a comparator to sequentially compare the flicker pulse to be processed with the at least two thresholds, comprising: The at least two thresholds are switched sequentially according to the state signal, so that the same circuit including a comparator sequentially compares the pulse to be processed with the magnitude of different thresholds among the at least two thresholds.

6. The signal sampling method of digital PET according to claim 1, characterized in that: The status signal includes a rising edge indicating that the pending scintillation pulse crosses at least some of the at least two thresholds including a lowest threshold and a falling edge indicating that the pending scintillation pulse crosses all of the at least two thresholds.

7. The signal sampling method of digital PET according to claim 1, characterized in that: The sequentially time sampling the at least two status signals comprises: Performing a first time sampling at a time corresponding to a rising edge of the state signal based on a minimum threshold; Determining whether the first time sampling is successful; The second time sampling is performed on the time instants corresponding to the falling edges of the state signal in descending order.

8. The signal sampling method of digital PET according to claim 7, characterized in that: After performing a first time sampling on a moment corresponding to a rising edge of the state signal based on a minimum threshold, the signal sampling method further includes: Determining whether the scintillation pulse to be processed is a valid signal; If yes, synchronously output the feedback signal and start switching to perform second time sampling on the moments corresponding to the falling edges of the state signal in descending order; If not, return to the initial state and re-execute the first time sampling.

9. The signal sampling method of digital PET according to claim 8, characterized in that: The step of determining whether the scintillation pulse to be processed is a valid signal comprises the following steps: Setting a verification threshold, taking a threshold value close to the lowest threshold value among the at least two threshold values ​​as the verification threshold value; The circuit including a comparator is used to compare the flicker pulse to be processed with the verification threshold. If the verification status signal that the flicker pulse to be processed crosses the verification threshold is not obtained, it is a false trigger signal; if the verification status signal that the flicker pulse to be processed crosses the verification threshold is obtained, it is a valid signal.

10. The signal sampling method of digital PET according to claim 1, characterized in that: The sampling module is implemented by a circuit including a time-to-digital converter, and the time-to-digital converter implements the time sampling.

11. The signal sampling method of digital PET according to claim 1, characterized in that: The scintillation pulse threshold-time pair includes a state change time acquired by time sampling of the state signal and a threshold corresponding to the state change time.

12. A digital PET signal sampling method, characterized in that: The signal sampling method comprises: At least two groups of thresholds are preset, each group of thresholds includes at least two switchable thresholds; At least two circuits including a comparator are arranged in parallel and correspond one-to-one to the at least two groups of threshold values; Using the circuit including a comparator to compare the scintillation pulse to be processed with at least two thresholds of each corresponding group in each channel, and determining at least two state signals corresponding to the at least two thresholds of each group respectively when the scintillation pulse to be processed crosses the threshold; The same sampling module is used to perform time sampling on the state signal in sequence to obtain corresponding flicker pulse threshold-time pairs.

13. The signal sampling method of digital PET according to claim 12, characterized in that: Each group of thresholds includes at least two switchable thresholds implemented by a threshold providing module, and the threshold providing module is implemented by a circuit including a threshold control module and a threshold selection module. The threshold control module controls the threshold selection module in sequence according to the state signal to achieve switching selection of the at least two thresholds of each preset group of thresholds.

14. The signal sampling method of digital PET according to claim 12, characterized in that: The threshold is set to a value not exceeding the maximum amplitude of the scintillation pulse to be processed.

15. The signal sampling method of digital PET according to claim 12, characterized in that: The number of each group of thresholds is set to 2-4.

16. The signal sampling method of digital PET according to claim 12, characterized in that: A circuit including a comparator is used to compare the scintillation pulse to be processed with at least two thresholds corresponding to each group in each channel, including: Switching is performed sequentially between the at least two thresholds in each group according to the state signal, so that the circuit including a comparator corresponding to the group of thresholds sequentially compares the pulse to be processed with the size of different thresholds in the at least two thresholds.

17. The signal sampling method of digital PET according to claim 12, characterized in that: The status signal includes rising edges indicating that the scintillation pulse to be processed crosses at least some of the thresholds including the lowest threshold in each set of the at least two thresholds and falling edges indicating that the scintillation pulse to be processed crosses all of the thresholds in each set of the at least two thresholds.

18. The signal sampling method of digital PET according to claim 12, characterized in that: The sequentially time sampling the state signals comprises: Performing first time sampling on the moments corresponding to the rising edges of the plurality of state signals in sequence based on a first order; Determining whether the first time sampling is successful; Second time sampling is performed sequentially at the moments corresponding to the falling edges of the state signal based on a second order.

19. The signal sampling method of digital PET according to claim 18, characterized in that: The first order is an order of arrangement determined from small to large according to the lowest threshold value of each group of threshold values ​​of the at least two groups of threshold values, and the second order is an order of arrangement determined from large to small according to the threshold values ​​of each group of threshold values ​​of the at least two groups of threshold values.

20. The signal sampling method of digital PET according to claim 18, characterized in that: The method sequentially performs first time sampling on the moments corresponding to the rising edges of the plurality of state signals based on the first order, including: After performing a first time sampling at a time corresponding to a rising edge of a state signal corresponding to a lowest threshold value ranked first in the sorting, determining whether the flicker pulse to be processed is a valid signal; If so, synchronously output the feedback signal and perform first time sampling on the moment corresponding to the rising edge of the state signal corresponding to the other lowest threshold value in the at least two groups of threshold values ​​based on the first order; If not, return to the initial state and re-execute the first time sampling.

21. The signal sampling method of digital PET according to claim 20, characterized in that: The step of determining whether the scintillation pulse to be processed is a valid signal comprises the following steps: Setting a verification group, taking the group including the lowest threshold value ranked first among the at least two groups of threshold values ​​as the verification group; Setting a verification threshold, taking the threshold value close to the lowest threshold value among the at least two threshold values ​​of the verification group as the verification threshold value; A circuit including a comparator corresponding to the verification group is used to compare the flicker pulse to be processed with the verification threshold. If the verification status signal that the flicker pulse to be processed crosses the verification threshold is not obtained, it is a false trigger signal; if the verification status signal that the flicker pulse to be processed crosses the verification threshold is obtained, it is a valid signal.

22. The signal sampling method of digital PET according to claim 12, characterized in that: The sampling module is implemented by a circuit including a time-to-digital converter, and the time-to-digital converter implements the time sampling.

23. The signal sampling method of digital PET according to claim 12, characterized in that: The scintillation pulse threshold-time pair includes a state change time acquired by time sampling of the state signal and a threshold corresponding to the state change time.

24. A digital PET signal sampling device, characterized in that: The signal sampling device comprises: An acquisition module, used for acquiring scintillation pulses to be processed; A threshold providing module, used for switching and selecting at least two preset thresholds; a comparator, for sequentially comparing the scintillation pulse to be processed with the at least two thresholds, and determining at least two state signals corresponding to the at least two thresholds respectively when the scintillation pulse to be processed crosses the thresholds; The sampling module is used to perform time sampling on the at least two state signals in sequence to obtain corresponding flicker pulse threshold-time pairs.

25. The signal sampling device for digital PET according to claim 24, characterized in that: The threshold providing module includes a threshold control module and a threshold selection module. The threshold control module sequentially controls the threshold selection module according to the state signal to implement switching selection of the at least two preset thresholds.

26. The signal sampling device for digital PET according to claim 24, characterized in that: The sampling module includes a time-to-digital converter, which is communicatively connected with the comparator and implements the time sampling.

27. The signal sampling device for digital PET according to claim 24, characterized in that: The scintillation pulse threshold-time pair includes a state change time acquired by time sampling of the state signal and a threshold corresponding to the state change time.

28. A digital PET signal sampling device, characterized in that: The signal sampling device comprises: An acquisition module, used for acquiring scintillation pulses to be processed; At least two threshold providing modules, wherein each threshold providing module is used to switch and select at least two preset thresholds; At least two comparators are arranged in parallel, and correspond to the at least two threshold providing modules one by one, wherein each of the comparators is used to sequentially compare the flicker pulse to be processed with the at least two thresholds provided by the corresponding threshold providing module, and determine at least two state signals corresponding to the at least two thresholds respectively when the flicker pulse to be processed crosses the threshold; A sampling module is used to perform time sampling on the state signal in sequence to obtain corresponding flicker pulse threshold-time pairs.

29. The signal sampling device for digital PET according to claim 28, characterized in that: The threshold providing module includes a threshold control module and a threshold selection module. The threshold control module sequentially controls the threshold selection module according to the state signal to implement switching selection of the at least two preset thresholds.

30. The signal sampling device for digital PET according to claim 28, characterized in that: The sampling module includes a time-to-digital converter, which is communicatively connected with the at least two comparators, and the time-to-digital converter implements the time sampling.

31. The signal sampling device for digital PET according to claim 28, characterized in that: The scintillation pulse threshold-time pair includes a state change time acquired by time sampling of the state signal and a threshold corresponding to the state change time.

32. A detector device, characterized in that: The detector device comprises: A detector and a signal sampling device for digital PET as claimed in any one of claims 24 to 31, wherein the detector is configured to detect gamma rays and output a scintillation pulse signal to be processed to the signal sampling device for digital sampling processing.

33. A digital PET device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the signal sampling method according to any one of claims 1 to 23.

34. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by the processor, the steps of the signal sampling method according to any one of claims 1 to 23 are implemented.

Images