Energy correction method, system, device and medium in signal accumulation events

Abstract

The present application belongs to the field of radiation detection technology, and specifically relates to a method, system, device and medium for energy correction in a signal accumulation event. The method includes: obtaining a target pulse signal output by a scintillator detector, and dividing it into a front-end signal and a back-end signal; based on the waveform information of the target pulse signal, obtaining the front-end energy and the total pulse energy of the target pulse signal; judging whether the target pulse signal needs energy correction based on the front-end energy, the total pulse energy and the predetermined normal ratio range of the front-end energy to the total pulse energy; for the target pulse signal that needs energy correction, determining the pulse signal of the unaccumulated part in the target pulse signal based on the front-end energy and the total pulse energy; based on the standard pulse signal waveform distribution law obtained in advance and the pulse signal of the unaccumulated part, reversely inferring the corrected total pulse energy. This method reduces the amount of calculation and the occupancy rate of computing resources, and has high economic efficiency.

Description

Technical Field

[0001] The present application belongs to the field of radiation detection technology, and specifically relates to an energy correction method in a signal accumulation event. Background Art

[0002] Positron emission tomography (PET) is a clinical diagnostic imaging technology in the field of nuclear medicine. Its basic principle is to inject a tracer containing positron-emitting radionuclides into a living organism, and then detect the energy, time, and position information of the 511 kiloelectron volt (keV) gamma rays emitted in the opposite direction when the positrons annihilate in vitro. Ultimately, the distribution location and concentration information of the tracer in the organism are determined by statistically reconstructing the location of the annihilation event, providing a molecular-level diagnostic basis for clinical practice.

[0003] In PET radiation detection systems, energy information is a key indicator. In this system, scintillator detectors convert gamma rays into electrical signals. The amplitude or area of ​​the detector output signal is then used to characterize the energy of the gamma rays. When two gamma rays are converted into electrical signals on the same detector but are too close in the time domain, the output signal is distorted, affecting the amplitude and area of ​​the signal. This is a signal pile-up event. This can distort energy information, causing true 511keV events to be counted as invalid events outside the effective energy window, while also causing low-energy events to be counted within the effective energy window, thereby affecting the imaging quality of the PET system. For PET systems where position information is calculated using energy information, signal pile-up can also lead to misalignment of the detected event position information.

[0004] To mitigate the impact of signal pile-up events on radiation detection energy results, existing methods reduce the probability of signal pile-up by narrowing the detector signal width in the time domain. When the detector signal width is fixed, methods are used to correct the energy information of pulse pile-up events to address signal pile-up events. These methods include iteratively analyzing the true shape of the pile-up signal using a signal distribution function and shortening the integration time of the pile-up event in a digital trapezoidal shaping algorithm. However, correcting for pile-up event energy information requires a front-end analog-to-digital converter with a high sampling rate for the pulse signal, which consumes significant computing resources. Furthermore, PET systems often have hundreds of scintillator detectors, necessitating large-scale processing circuitry, making them less cost-effective. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present application provides a method, system, device and medium for energy correction in a signal accumulation event.

[0007] (2) Technical solution

[0008] To achieve the above objectives, this application adopts the following technical solutions:

[0009] In a first aspect, an embodiment of the present application provides an energy correction method in a signal pile-up event, which is applied to a radiation detection system. The method includes:

[0010] Acquire a target pulse signal output by a scintillator detector, and divide the target pulse signal into a front-end signal and a back-end signal;

[0011] Based on the waveform information of the target pulse signal, obtaining the front-end energy and the total pulse energy of the target pulse signal;

[0012] determining whether the target pulse signal needs energy correction according to the front-end energy, the total pulse energy, and a predetermined normal ratio range of the front-end energy to the total pulse energy;

[0013] For a target pulse signal requiring energy correction, determining a pulse signal of an unaccumulated portion of the target pulse signal based on the preceding energy and the total pulse energy of the target pulse signal;

[0014] Based on the standard pulse signal waveform distribution law obtained in advance and the pulse signal of the unaccumulated part, the total pulse energy of the target pulse signal after correction is obtained by reverse deduction.

[0015] Optionally, dividing the target pulse signal into a front-end signal and a back-end signal includes:

[0016] Obtaining the pulse peak time or the pulse area midpoint time of the target pulse signal;

[0017] The pulse peak time or the pulse area midpoint time is used as the time division point, the pulse signal before the time division point is used as the front-end signal, and the pulse signal after the time division point is used as the back-end signal.

[0018] Optionally, determining whether the target pulse signal needs energy correction based on a predetermined normal ratio range of the front-end energy to the total pulse energy includes:

[0019] Calculating the ratio of the front-end energy to the total pulse energy to obtain the energy ratio of the target pulse signal;

[0020] When the energy ratio is within the normal ratio range, the target pulse signal does not need to be energy corrected;

[0021] When the energy ratio exceeds the normal ratio range, the target pulse signal needs to be energy corrected.

[0022] Optionally, before obtaining the target pulse signal output by the scintillator detector, the method further includes: determining a normal ratio range of the front-end energy to the total pulse energy, specifically including:

[0023] Collecting a preset number of standard pulse signals output by the scintillator detector, and dividing each standard pulse signal into a front-end standard signal and a rear-end standard signal;

[0024] Based on the waveform information of the standard pulse signal, obtaining the front-end standard signal energy and the total energy of the standard pulse signal;

[0025] Calculating the ratio of the energy of the preceding standard signal to the total energy of the standard pulse signal to obtain an energy ratio of the standard pulse signal;

[0026] Performing distribution statistics on the energy ratios of a preset number of standard pulse signals, and taking the peak value or the center of gravity of the distribution curve as the ideal value η of the front-segment pulse ratio;

[0027] The normal ratio range of the front-end energy to the total pulse energy is (η-σ, η+σ), wherein the value of σ is 1-3 times the half-height width of the distribution curve.

[0028] Optionally, for a target pulse signal requiring energy correction, determining an unaccumulated portion of the target pulse signal based on a preceding energy and a total pulse energy of the target pulse signal includes:

[0029] Calculating the ratio of the front-end energy of the target pulse signal to the total pulse energy;

[0030] If the ratio of the front-end energy to the total pulse energy is less than η-σ, the front-end of the target pulse signal is determined to be an unaccumulated part;

[0031] If the ratio of the front-end energy to the total pulse energy is greater than η+σ, the rear-end of the target pulse signal is determined to be the unaccumulated part;

[0032] If the ratio of the front-end energy to the total pulse energy is within the range of η±σ, it is determined that the target pulse signal has not accumulated.

[0033] Optionally, the standard pulse signal waveform distribution law includes a normalized coefficient of variation of the standard pulse signal amplitude over time. Based on the pre-statistically obtained standard pulse signal waveform distribution law and the unstacking portion of the pulse signal, the corrected total pulse energy of the target pulse signal is obtained by reverse deduction using the following formula:

[0034]

[0035] Among them, Esumcorr is the total pulse energy after correction, T is the total number of pulse sampling points, A0 is the pulse highest point data of the standard pulse signal, I t is the normalized variation coefficient of the standard pulse signal amplitude over time, P t is the amplitude data of the target pulse signal sampling point, t eff is the time range of the pulse signal of the unaccumulated part in the target pulse signal.

[0036] Optionally, the standard pulse signal waveform distribution law includes a normalized coefficient of variation of the standard pulse signal amplitude over time. Based on the standard pulse signal waveform distribution law obtained in advance and the pulse signal of the unstacked portion, the corrected total pulse energy of the target pulse signal is obtained by reverse deduction using the following formula, including:

[0037]

[0038] Among them, E sumcorr is the total pulse energy after correction, T is the total number of pulse sampling points, I t is the normalized variation coefficient of the standard pulse signal amplitude over time, P t is the amplitude data of the target pulse signal sampling point, t eff is the time range of the pulse signal of the unaccumulated part in the target pulse signal.

[0039] In a second aspect, an embodiment of the present application provides a radiation detection system, which includes a detector and a control device, wherein the control device is used to execute the energy correction method in the signal pile-up event as described in any one of the first aspects above to correct the energy of the pile-up event.

[0040] In a third aspect, an embodiment of the present application provides an electronic device comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the computer program is executed by the processor, the steps of the energy correction method in the signal accumulation event as described in any one of the first aspects above are implemented.

[0041] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the energy correction method in a signal pile-up event as described in any one of the first aspects above are implemented.

[0042] (3) Beneficial effects

[0043] The beneficial effects of the present application are as follows: the present application proposes a method, system, device and medium for energy correction in a signal accumulation event, wherein the method includes: obtaining a target pulse signal output by a scintillator detector and dividing it into a front-end signal and a back-end signal; obtaining the front-end energy and the total pulse energy of the target pulse signal based on the waveform information of the target pulse signal; determining whether the target pulse signal needs energy correction based on the front-end energy, the total pulse energy and the predetermined normal ratio range of the front-end energy to the total pulse energy; for the target pulse signal that needs energy correction, determining the pulse signal of the unaccumulated part in the target pulse signal based on the front-end energy and the total pulse energy; and reversely deducing the corrected total pulse energy based on the standard pulse signal waveform distribution law obtained in advance and the pulse signal of the unaccumulated part. The method of the present application reduces the amount of calculation and the occupancy rate of computing resources, and has high economic efficiency.

[0044] Furthermore, the calculation speed is further improved by simplifying the energy correction method.

[0045] In addition, the corrected energy information obtained by this method is applied to the calculation of event positions, which can also correct the influence of pile-up events on event positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present application is described with the aid of the following drawings:

[0047] Figure 1 A schematic diagram of the application scenario of the energy correction method in signal pile-up events;

[0048] Figure 2 Schematic diagram of the pulse shape when signal accumulation occurs;

[0049] Figure 3 This is a flow chart of a method for energy correction in a signal accumulation event according to one embodiment of the present application;

[0050] Figure 4 This is a flow chart of an energy correction method in a signal accumulation event in another embodiment of the present application;

[0051] Figure 5 This is a distribution diagram of the front-end pulse area ratio in an example of this application;

[0052] Figure 6 This is a comparison diagram of energy spectra before and after pile-up correction in an example of this application;

[0053] Figure 7 This is a schematic diagram of the structure of an electronic device in another embodiment of the present application. DETAILED DESCRIPTION

[0054] To better explain the present invention and facilitate understanding, the present invention is described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described below are merely for explaining the relevant invention and are not intended to limit the invention. It should also be noted that the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict; for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0055] The energy correction method for signal pile-up events can be applied to a radiation detection system, which can be a PET system or a single photon emission computed tomography (SPECT) system. The radiation detection system is described below using a PET system as an example.

[0056] Figure 1 Schematic diagram of the application scenario of the energy correction method in signal accumulation events, such as Figure 1 As shown in FIG, the PET system may include a PET device 10 and a console device 20. The PET device 10 may include a detector 11 (PET detector) and a scanning bed 12. The console device 20 receives acquisition and image processing instructions, controls the movement of the detector 11 and the scanning bed 12, processes the acquired signals, and reconstructs a three-dimensional image. Figure 1 The annular detector 11 may include a plurality of scintillator detectors, each of which may include a scintillator, a photodetector, and a processing circuit connected in sequence. The scanning bed 12 may carry the subject to the annular detector 11 for scanning.

[0057] Figure 1 In the PET system shown, before scanning, the subject can be injected with a tracer containing a radioactive nuclide. During the scanning process, the radioactive nuclide decays to produce positrons, which annihilate with the surrounding negative electrons in the subject to produce a pair of back-to-back gamma photons. The gamma photons, as a kind of high-energy photons, can be detected by the scintillators of a pair of scintillator detectors in the detector 11. The scintillators convert the detected high-energy photons into light signals and transmit them to the photodetector. The photodetector converts the light signals into electrical signals and transmits them to the processing circuit. The processing circuit converts the electrical signals into pulse signals and can output information of the pulse signals, such as energy information, time information, etc.

[0058] When the electrical signals converted by two gamma rays on the same scintillator detector are too close in time domain, a pulse signal pile-up event will occur. Figure 2 This is a schematic diagram of the pulse shape when the signal piles up, as shown in Figure 2As shown in the figure, the horizontal axis is time and the vertical axis is voltage. Pulse A and pulse B experience signal accumulation, with t1 representing the first half of pulse A and t2 representing the first half of pulse B. During signal accumulation, the ratio of the pulse area in the first half, time t1, to the total area is smaller than in the absence of signal accumulation because pulse A has signal accumulation behind it. Similarly, the ratio of the pulse area in the first half, time t2, to the total area is larger than in the absence of signal accumulation because pulse B accumulates on the previous pulse.

[0059] In order to correct the energy information of pulse pile-up events, the difference between the measured pulse shape and the standard pulse shape is used to determine whether a pulse pile-up event has occurred and corresponding correction processing is performed to effectively extract the energy and position information of the gamma rays, thereby improving the quality of PET reconstructed images.

[0060] The following combination Figure 1 The PET system shown is used to illustrate the method of the present invention through specific examples.

[0061] Example 1

[0062] Figure 3 FIG. 1 is a flow chart of an energy correction method in a signal accumulation event in one embodiment of the present application. Figure 1 As shown, the energy correction method in the signal pile-up event of this embodiment is applied to a PET system, including:

[0063] S10, obtaining a target pulse signal output by a scintillator detector, and dividing the target pulse signal into a front-end signal and a back-end signal;

[0064] S20, obtaining the front-end energy and total pulse energy of the target pulse signal based on the waveform information of the target pulse signal;

[0065] S30, determining whether the target pulse signal needs energy correction based on the front-end energy, the total pulse energy, and a predetermined normal ratio range of the front-end energy to the total pulse energy;

[0066] S40, for a target pulse signal requiring energy correction, determining a pulse signal of an unaccumulated portion of the target pulse signal based on a preceding energy and a total pulse energy of the target pulse signal;

[0067] S50 , based on the standard pulse signal waveform distribution law obtained in advance and the pulse signal of the unaccumulated part, reversely infer the corrected total pulse energy of the target pulse signal.

[0068] The energy correction method in the signal accumulation event of this embodiment has low requirements on the sampling rate and computational complexity of the analog-to-digital converter, greatly reduces the computational complexity and the occupation of computing resources, improves the accuracy of energy information calculation, and thus improves the imaging effect of PET.

[0069] In order to better understand the present invention, each step in this embodiment is described below.

[0070] In S10 of this embodiment, the method of dividing the target pulse signal into the front-end signal and the back-end signal may be:

[0071] Obtain the pulse peak time or the area midpoint time of the target pulse signal;

[0072] The pulse peak time or the pulse area midpoint time is taken as the time division point, the pulse signal before the time division point is taken as the front-end signal, and the pulse signal after the time division point is taken as the back-end signal.

[0073] In a PET system, the energy information of the gamma ray is usually represented by the amplitude or area of ​​the detector output signal. In this embodiment, the energy information of the gamma ray is represented by the area of ​​the detector output signal.

[0074] Therefore, the front-end energy and the total pulse energy of the target pulse signal in S20 of this embodiment are the front-end signal area and the total pulse signal area, respectively.

[0075] In this embodiment S30, the normal ratio range of the front-end energy to the total pulse energy can be obtained by statistically analyzing standard pulse signals without pile-up events. The standard pulse signals are pulse signals collected under conditions of a relatively low activity radioactive source.

[0076] In S40 of this embodiment, the pulse signal of the non-accumulated portion in the determined target pulse signal is the front-end signal or the back-end signal.

[0077] In this embodiment S50, the standard pulse signal waveform distribution pattern is the normalized coefficient of variation of the standard pulse signal amplitude over time. The normalized coefficient of variation can be calculated by combining the theoretical luminous intensity variation function of the scintillator used in the detector with the response function of the subsequent photodetector and the transfer function of the electronic circuit; it can also be obtained by sampling a certain number of pulse waveforms at a low count rate (a count rate that ensures that pile-up effects are almost non-existent), performing amplitude normalization processing on each sampled waveform, and then performing time-aligned averaging processing on the normalized waveforms.

[0078] Example 2

[0079] This embodiment describes in detail the complete implementation process and principle of the energy correction method in the signal accumulation event.

[0080] S1. Use the pulse signal area to represent the ray energy, and calculate the front area and total area of ​​the target pulse signal respectively.

[0081] For the same scintillator detector, the decay time variation pattern of the light pulse excited in the scintillator when gamma rays are incident is consistent, and the conversion and amplification of the light signal by the photomultiplier tube and the processing circuit is a fixed transfer function. Therefore, the output signals of gamma rays of different energies after entering the scintillator detector have different amplitudes, but the change trends in the time domain are consistent.

[0082] In view of the above rules, the typical waveform of the standard non-pile-up pulse signal is expressed as:

[0083] S(t)=A0·I(t) (1)

[0084] Where S(t) is the amplitude distribution of the standard non-pile-up pulse signal at different times, A0 is the peak amplitude of the signal, and I(t) is the normalized coefficient of variation of the signal amplitude over time.

[0085] For the same scintillator detector, the signal variation pattern I(t) obtained by detecting gamma rays of different energies is basically the same, while the amplitude A0 varies with the size of the deposited energy. Because the pulse data collected by the analog-to-digital converter (ADC) in the actual system is discrete, the typical non-pile-up waveform can be expressed as S = [S1, S2, ..., S T ]. Discretize formula (1) over time and transform it into the following formula:

[0086] S i =A0·I i , i=1,…,T (2)

[0087] Among them, S i is the amplitude data of each point of a typical non-pile-up waveform, A0 is the highest point data of the pulse, I i is the normalization coefficient of the scintillator detector signal change, i represents a discrete time point, and T represents the total number of sampling points for each pulse, which is determined by the pulse time length and is a fixed value.

[0088] The decay of a radioactive source is a random event with statistical regularity. Therefore, at relatively low activity levels, most events are normal, non-pile-up events. Therefore, by collecting a certain statistical amount of signal data under low-activity radioactive source conditions, we can obtain the waveform variation pattern of a standard, non-pile-up pulse signal.

[0089] The actual waveform collected is expressed as P = [P1, P2, ..., P T ], defined as:

[0090] P i =A1·d i , i=1,…,T (3)

[0091] Among them, P i The amplitude data of each sampling point of the actual waveform obtained by collecting a pulse using ADC, A1 is the highest point data of the pulse collected by ADC, and d i is the normalization coefficient of the scintillator detector signal change, i represents a discrete time point, and the sampling time point range T is the same as that of the standard non-pile-up pulse signal.

[0092] The total area of ​​the signal pulse is used to characterize the energy of the detected gamma rays. For each pulse signal, the area of ​​the preceding pulse and the total area of ​​the pulse are collected.

[0093] Based on the pulse sampling points obtained by actual sampling according to formula (3), the total area of ​​the pulse signal is defined as:

[0094]

[0095] Among them, E sum is the total area of ​​the pulse signal, T is the total number of pulse sampling points, P i It is the pulse amplitude of each point collected by ADC.

[0096] Define the signal area of ​​the first m points of the pulse signal as the front pulse area, then the front pulse area is:

[0097]

[0098] Among them, E p is the area of ​​the front pulse, m is the number of sampling points of the front pulse, P i It is the pulse amplitude of each point collected by ADC.

[0099] It should be noted that the actual pulse amplitude captured by the ADC itself has electronic fluctuations and random fluctuations in the amplitude signal itself. Therefore, a longer initial pulse integration time results in a more accurate area result, but also reduces the ability to resolve pileup events. In applications, it is necessary to adjust the m value to find a balance between area accuracy and pileup event resolution. In this embodiment, the m value can be selected from, but is not limited to, the pulse peak time or the pulse area midpoint time.

[0100] S2. Determine whether the target pulse signal needs energy correction based on a predetermined normal ratio range of the front section area to the total area and a ratio range that needs correction.

[0101] Methods for determining whether a target pulse signal requires energy correction include:

[0102] For the target pulse signal, the ratio of the front pulse area to the total area η is calculated by the following formula: p ;

[0103]

[0104] For η p For waveforms with values ​​within the normal proportional range, the target pulse signal does not require energy correction;

[0105] For η p For waveforms whose values ​​exceed the normal proportional range, the target pulse signal needs to be energy corrected.

[0106] The following describes in detail the process of determining the normal ratio range of the front section area to the total area and the ratio range that needs to be corrected.

[0107] When pile-up occurs, the standard pulse shape S can be used to correct the pile-up signal P. Before performing energy pile-up correction, it is necessary to determine whether the pile-up occurs at the front or back end of the waveform.

[0108] For a standard pulse signal, the following formula is used to calculate the theoretical ratio of the preceding pulse area to the total area:

[0109]

[0110] For a standard non-pile-up pulse signal, the shape of the pulse signal does not change with the signal size, so the area ratio of the front section is η s is a value independent of the pulse amplitude. s By performing distribution statistics, a quasi-Gaussian distribution can be obtained. The peak value or the center of gravity of the distribution curve is taken as the ideal value η of the front-end pulse ratio.

[0111] Considering the inherent shape fluctuations of actual waveforms, no correction is performed for events whose preceding pulse ratio falls within the range η ± σ, while a pile-up correction is performed for events outside this range. σ is determined to ensure that under low activity conditions, the majority of events (70% or more) fall within the range η ± σ. For example, the standard deviation σ can be set to 1-3 times the half-width of the η distribution curve.

[0112] S3. For a target pulse signal requiring energy correction, determine the non-accumulated portion of the target pulse signal based on the ratio of the area of ​​the preceding pulse of the target pulse signal to the total area.

[0113] In this embodiment, for the target pulse signal that needs energy correction, the ratio η of the area of ​​the first pulse segment of the target pulse signal to the total area is used. p , a method for determining the unaccumulated portion of the target pulse signal, comprising:

[0114] For η p For pulse events smaller than η-σ, it is determined that the pulse tail has accumulated. In this case, the non-accumulation time range is defined as t eff =[1,2,……,m];

[0115] For η p For pulse events larger than η+σ, it is determined that they have accumulated to the tail of other pulses. In this case, the unaccumulated time range is defined as t eff =[m+1,……,T];

[0116] For η p For events within the range of η±σ, it is determined that no accumulation has occurred, and the non-accumulation time range is defined as t eff =[1,……,T].

[0117] S4. Using the standard waveform distribution law obtained in advance, reversely infer the corrected pulse area based on the unaccumulated part.

[0118] In this embodiment, the method of using the standard waveform distribution law obtained in advance and inferring the corrected pulse area based on the unaccumulated part can be:

[0119] Using the waveform within the unstacked time range, the stacking energy is corrected by comparing the similarity between the typical signal and the measured signal. The square of the Euclidean distance D can be selected but is not limited to:

[0120]

[0121] Where P is the actual acquisition pulse amplitude, I is the normalized change coefficient of the signal amplitude over time, and is a known quantity. eff The time range for the unstacked portion.

[0122] The goal is to achieve the closest similarity between the acquired waveform and the typical waveform by optimizing the amplitude variable A0. Taking A0 as the variable, the derivative of formula (8) is 0:

[0123]

[0124] The most similar pulse amplitude obtained is:

[0125]

[0126] In this way, using the amplitude A0 and the typical waveform, the waveform after pile-up correction can be obtained, so the total energy is:

[0127]

[0128] The energy correction function of the pile-up signal can be achieved through the above method.

[0129] Example 3

[0130] This embodiment proposes a simplified energy correction method to improve the calculation speed in response to the situation where the ADC sampling points are insufficient or the computing resources are insufficient.

[0131] According to formula (12), formula (11) is simplified to obtain

[0132]

[0133]

[0134] Among them, η c It is the ratio of the pulse area within the unstacked time range of the standard pulse signal to the total area.

[0135] Because t eff The range of η varies with the location of the accumulation, so when the accumulation occurs in the second half of the pulse, η c =η, when the accumulation occurs in the first half of the pulse, η c =1-η, when no accumulation occurs, η c = 1. This simplification is an approximation based on the fact that typical waveform changes are not drastic. This directly uses the calculated area of ​​the unresolved portion to obtain the corrected pulse signal area, simplifying the calculation process and speeding up the computation time. In practical applications, this approximation can achieve a good balance between speed and accuracy.

[0136] In formula (12), it is also necessary to select t eff The pulse area within the non-accumulated time range of the target pulse signal is calculated by the method of:

[0137] For η p For pulse events smaller than η-σ, it is determined that the pulse tail has accumulated. Based on the front pulse area E of the target pulse signal p Corrected pulse total area E sum ,

[0138] E sumcorr =E p / η (13)

[0139] Among them, E sumcorr is the total pulse area after correction.

[0140] For η p For pulse events larger than η+σ, it is determined that they are accumulated at the tail of other pulses. Therefore, the total pulse area is directly corrected by the area of ​​the latter pulse, that is, the following formula:

[0141] E sumcorr =(Esum-Ep ) / (1-η) (14)

[0142] For η p For events within the range of η±σ, it is determined that no pile-up has occurred and no pile-up correction is required.

[0143] In this way, the accumulation judgment of the measured pulses and the corresponding energy correction can be completed simply and quickly.

[0144] Performing energy correction not only improves the accuracy of energy information, but in some other embodiments, the corrected energy signal after a pile-up event can also be used to improve position information in a PET system.

[0145] In some PET systems, event location is achieved by the relative size ratio of several energy information channels. For example, in a PET probe with four energy output channels, the position information of an event is located using formulas (15) and (16):

[0146]

[0147]

[0148] Where X is the horizontal coordinate of the signal positioning, Y is the vertical coordinate of the positioning, and A, B, C, and D are the four energy outputs of the PET probe.

[0149] After stacking correction of the four energy signals, the newly corrected coordinates are:

[0150]

[0151]

[0152] After the stacking correction process, the accuracy of the position information of the PET system is also greatly improved.

[0153] The following uses the pile-up correction operation on a single-probe detector as a specific implementation case to illustrate the implementation steps of this embodiment.

[0154] The steps of energy calibration include:

[0155] A1. The detector signal width is approximately 140ns, and the ADC sampling rate is 50MHz. This means one point is sampled every 20ns, and seven points are required for the entire pulse. The area of ​​the front pulse segment is the first 80ns, or the integrated area of ​​the first four points.

[0156] A2. Use a 200μCi deoxyglucose source at a distance of 1m from the detector to obtain the ratio of the area of ​​the front pulse of 1000 pulses to the total area of ​​the detector η s The distribution results of Figure 5 This is a distribution diagram of the front-end pulse area ratio in an example of this application. Figure 5 The horizontal axis is the ratio of the measured front section area to the total area, and the vertical axis is a certain ratio counting statistic. The distribution of the ratio of the front section pulse area to the total area is as follows: Figure 5 shown.

[0157] A3. Yes Figure 5 Analyze the distribution in to get η s The center of gravity of the distribution is 0.57, η s The number of events in the range of 0.56-0.58 accounts for 74% of the total counts. Events within this range are considered to be non-pile-up events, and events outside this range need to be energy corrected according to formulas (13) and (14).

[0158] A4. Increase the activity of the deoxy-grape source to 5 mCi. Statistically analyze the energy spectrum distribution of 2600 events at this time. Figure 6 . Figure 6 This is a comparison diagram of energy spectra before and after pile-up correction in an example of this application. Figure 6 (a) shows the spectrum before pile-up correction, and (b) shows the spectrum after pile-up correction. It can be seen that after pile-up correction, the counts on the right side of the full-energy peak of the spectrum have decreased, the full-energy peak counts are more concentrated, and the peak-to-valley ratio has improved.

[0159] Based on the basic characteristics of radiation detectors, the present invention provides a simple and flexible method that has low requirements on the sampling rate and computational complexity of analog-to-digital converters and can be used to determine whether a radiation signal pile-up event has occurred and perform pile-up energy correction. This method greatly reduces the computational complexity and the occupation of computing resources, improves the accuracy of energy information calculation, and thus improves the imaging effect of PET.

[0160] The corrected energy information obtained by this method is used to calculate the event position, further correcting the impact of pile-up events on event positioning.

[0161] Example 3

[0162] In a second aspect, the present application provides a radiation detection system through Example 3, which includes a detector and a control device, and the control device is used to execute the energy correction method in the signal pile-up event as described in any of the above embodiments to correct the energy of the pile-up event.

[0163] The radiation detection system provided in this embodiment can be used to execute the steps of the energy correction method in the signal accumulation event in the above method embodiment. Its implementation principle and technical effects are similar and will not be repeated here in this embodiment.

[0164] Example 4

[0165] In the third aspect of the present application, an electronic device is provided through Example 4, including: a memory, a processor, and a computer program stored in the memory and runnable on the processor. When the computer program is executed by the processor, the steps of the energy correction method in the signal accumulation event as described in any one of the above embodiments are implemented.

[0166] Figure 7 This is a schematic diagram of the structure of an electronic device in another embodiment of the present application.

[0167] Figure 7 The electronic device shown may include: at least one processor 101, at least one memory 102, at least one network interface 104 and other user interfaces 103. The various components in the electronic device are coupled together via a bus system 105. It is understood that the bus system 105 is used to achieve connection and communication between these components. In addition to including a data bus, the bus system 105 also includes a power bus, a control bus and a status signal bus. However, for the sake of clarity, the bus system 105 is not described in detail. Figure 7 Various buses are labeled as bus system 105 .

[0168] The user interface 103 may include a display, a keyboard, or a pointing device (eg, a mouse, a trackball, or a touchpad).

[0169] It is understood that the memory 102 in this embodiment can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct RAM bus random access memory (DRRAM). The memory 62 described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0170] In some embodiments, the memory 102 stores the following elements, executable units, or data structures, or a subset thereof, or an extended set thereof: an operating system 1021 and application programs 1022 .

[0171] The operating system 1021 includes various system programs, such as a framework layer, a core library layer, and a driver layer, for implementing various basic services and handling hardware-based tasks. Application programs 1022 include various application programs for implementing various application services. Programs implementing the methods of the embodiments of the present invention may be included in application programs 1022.

[0172] In an embodiment of the present invention, the processor 101 calls a program or instruction stored in the memory 102, specifically, a program or instruction stored in the application 1022, and the processor 101 is used to execute the method steps provided in the first aspect.

[0173] The methods disclosed in the above embodiments of the present invention can be applied to or implemented by processor 101. Processor 101 may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method can be performed by hardware integrated logic circuits in processor 101 or by software instructions. Processor 101 may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, an off-the-shelf programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The methods, steps, and logic block diagrams disclosed in the embodiments of the present invention can be implemented or executed. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in conjunction with the embodiments of the present invention can be directly implemented and executed by a hardware decoding processor or by a combination of hardware and software units in the decoding processor. The software units can be located in a storage medium well-known in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. This storage medium is located in memory 102. Processor 101 reads information from memory 102 and, in conjunction with its hardware, completes the steps of the above method.

[0174] In addition, in combination with the energy correction method in the signal accumulation event in the above-mentioned embodiment, an embodiment of the present invention may provide a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the energy correction method in the signal accumulation event in any one of the above method embodiments.

[0175] It should be noted that in the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claim. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The present invention can be implemented by means of hardware comprising several distinct components and by means of a suitably programmed computer. The use of the words first, second, third, etc. is merely for convenience and does not imply any order. These words should be understood as part of the component name.

[0176] In addition, it should be noted that, in the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0177] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments after learning the basic creative concept. Therefore, the claims should be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0178] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims and their equivalents, the present invention shall also include such modifications and variations.

Claims

1. A method for energy correction in a signal accumulation event, characterized in that: Applied to a radiation detection system, the method comprises: Acquire a target pulse signal output by a scintillator detector, and divide the target pulse signal into a front-end signal and a back-end signal; Based on the waveform information of the target pulse signal, obtaining the front-end energy and the total pulse energy of the target pulse signal; determining whether the target pulse signal needs energy correction according to the front-end energy, the total pulse energy, and a predetermined normal ratio range of the front-end energy to the total pulse energy; Performing distribution statistics on the energy ratios of a preset number of standard pulse signals, and taking the peak value or the center of gravity of the distribution curve as the ideal value η of the front-segment pulse ratio; The normal ratio range of the front-end energy to the total pulse energy is (η-σ, η+σ), where the value of σ is 1-3 times the half-height width of the distribution curve; For a target pulse signal requiring energy correction, determining a pulse signal of an unaccumulated portion of the target pulse signal based on the preceding energy and the total pulse energy of the target pulse signal; Specifically include: Calculating the ratio of the front-end energy of the target pulse signal to the total pulse energy; If the ratio of the front-end energy to the total pulse energy is less than η-σ, the front-end of the target pulse signal is determined to be an unaccumulated part; If the ratio of the front-end energy to the total pulse energy is greater than η+σ, the rear-end of the target pulse signal is determined to be the unaccumulated part; If the ratio of the front-end energy to the total pulse energy is within the range of η±σ, it is determined that the target pulse signal has not accumulated; Based on the pre-statistically obtained standard pulse signal waveform distribution law and the unstacking portion of the pulse signal, the corrected total pulse energy of the target pulse signal is obtained by reverse calculation; The standard pulse signal waveform distribution law includes the normalized variation coefficient of the standard pulse signal amplitude over time. Based on the pre-statistically obtained standard pulse signal waveform distribution law and the unstacked pulse signal, the corrected total pulse energy of the target pulse signal is obtained by reverse deduction using the following formula: ； Among them, E sumcorr is the total pulse energy after correction, T is the total number of pulse sampling points, A0 is the pulse highest point data of the standard pulse signal, I t is the normalized variation coefficient of the standard pulse signal amplitude over time, P t is the amplitude data of the target pulse signal sampling point, t eff is the time range of the pulse signal of the unaccumulated part in the target pulse signal.

2. The energy correction method in a signal accumulation event according to claim 1, characterized in that: Dividing the target pulse signal into a front-end signal and a back-end signal, comprising: Obtaining the pulse peak time or the pulse area midpoint time of the target pulse signal; The pulse peak time or the pulse area midpoint time is used as the time division point, the pulse signal before the time division point is used as the front-end signal, and the pulse signal after the time division point is used as the back-end signal.

3. The energy correction method in a signal accumulation event according to claim 1, characterized in that: Determining whether the target pulse signal needs energy correction based on a predetermined normal ratio range of the front-end energy to the total pulse energy includes: Calculating the ratio of the front-end energy to the total pulse energy to obtain the energy ratio of the target pulse signal; When the energy ratio is within the normal ratio range, the target pulse signal does not need to be energy corrected; When the energy ratio exceeds the normal ratio range, the target pulse signal needs to be energy corrected.

4. The energy correction method in a signal accumulation event according to claim 1, characterized in that: Before obtaining the target pulse signal output by the scintillator detector, the method further includes: determining a normal ratio range of the front-end energy to the total pulse energy, specifically including: Collecting a preset number of standard pulse signals output by the scintillator detector, and dividing each standard pulse signal into a front-end standard signal and a rear-end standard signal; Based on the waveform information of the standard pulse signal, obtaining the front-end standard signal energy and the total energy of the standard pulse signal; The ratio of the energy of the front-end standard signal to the total energy of the standard pulse signal is calculated to obtain the energy ratio of the standard pulse signal.

5. The energy correction method in a signal accumulation event according to claim 1, characterized in that: The standard pulse signal waveform distribution law includes the normalized variation coefficient of the standard pulse signal amplitude over time. Based on the pre-statistically obtained standard pulse signal waveform distribution law and the unstacked pulse signal, the corrected total pulse energy of the target pulse signal is obtained by reverse deduction using the following simplified energy correction formula, including: ； Among them, η c is the ratio of the pulse area to the total area within the unstacked time range of the standard pulse signal, E sumcorr is the total pulse energy after correction, T is the total number of pulse sampling points, I t is the normalized variation coefficient of the standard pulse signal amplitude over time, P t is the amplitude data of the target pulse signal sampling point, t eff is the time range of the pulse signal of the unaccumulated part in the target pulse signal.

6. A radiation detection system, characterized in that: The system comprises a detector and a control device, wherein the control device is used to execute the energy correction method in a signal pile-up event as described in any one of claims 1 to 5 to correct the energy of the pile-up event.

7. An electronic device, characterized in that: include: 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 energy correction method in a signal accumulation event as described in any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the energy correction method in a signal pile-up event according to any one of claims 1 to 5 are implemented.

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