Time correction method and device for multiplexed readout PET detector

Abstract

The application discloses a time correction method and device for a multiplexed readout PET detector, aiming at a coincidence event of a PET detector, extracting the amplitude of a signal, calculating the hit position and DOI by using a double-end four-corner readout 8-channel output signal; extracting the time information of the 8-channel output signal, using the amplitude for weighting, obtaining the original time of a coincidence event particle reaching two detectors; establishing a three-dimensional index, so that the original time of the two detectors is equal after subtracting the respective corresponding delay time; establishing an overdetermined equation group about the corresponding delay time of the two detectors, obtaining the delay time corresponding to each three-dimensional index of the two detectors; establishing a three-dimensional index-delay time lookup table, and subtracting the delay time from the original time of each event to obtain the corrected time. The method and device correct the detector signal delay by processing the different channel digital waveforms after multiplexing in the coincidence event, and improve the time precision and imaging quality of the PET.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear medical imaging, and particularly relates to a time correction method and device for a multiplexed readout PET detector. BACKGROUND

[0002] Positron Emission Tomography (PET) is an advanced nuclear medical imaging technique that can display metabolic function information in a living body. Its imaging principle is based on the decay of a radioactive isotope injected into the body to release a positron, and the annihilation of the positron with a negative electron in the tissue to produce a pair of annihilation photons (γ photons) with opposite directions (about 180°) and equal energy of 511 keV. A PET detector system located around the measured object measures the charge and time of arrival of the pair of annihilation photons at two opposite detectors, and calculates the position line (coincidence line) of the annihilation event. Time window screening (coincidence time window) is performed on all detected events to obtain coincidence events, and the time resolution of the system is usually represented by the Gaussian fitting half width (Full Width at Half Maxima, FWHM) of the coincidence event time difference distribution, which directly affects the Signal-to-Noise Ratio (SNR) of the PET image. Higher time resolution can significantly reduce the coincidence time window and effectively reduce the number of random coincidence events, thereby greatly improving the image quality. In a conventional PET system, in order to reduce the complexity of electronics (especially for high-density detector arrays), a light-sharing technology (light-sharing is a structure that uses fewer channels of photodetectors to couple a crystal array) combined with a multiplexing scheme is usually used. Specifically, a typical multiplexing scheme is as follows: after coupling an L×L crystal array with photodetectors, the signals are combined and output as W channels (W is much smaller than L×L). Among them, a resistive charge distribution network is a common implementation, which multiplexes the L×L original signals into 4 channels, i.e., a "four-corner readout" scheme, and then calculates the hit position by combining the charge barycenter method. For a double-ended readout detector, the two ends each adopt a four-corner readout structure, and finally form 8 output signals.

[0003] The traditional analog summation timing method is to directly perform analog summation on the 8-way output signals to form a total pulse signal, then generate a timing pulse through a discriminator, and finally record time information through a time-to-digital convertor (TDC). However, this scheme has the following disadvantages: different physical channels of the detector crystal array have inherent delay time due to differences in manufacturing process; in addition, the depth of interaction (DOI) of gamma photons and crystals will significantly affect the time of the signal reaching the readout circuit at both ends of the detector; therefore, the electrical signal after multiplexing is disturbed by the above-mentioned delay, and the time resolution of the system is seriously deteriorated. SUMMARY

[0004] The purpose of the present application is to provide a time correction method and device for a multiplexed readout PET detector, which corrects the signal delay of the detector by processing the digital waveforms of different channels after multiplexing in a coincidence event, and reduces the influence of the inherent delay time of the crystal and electronic circuit on the final time information measurement.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A time correction method for a multiplexed readout PET detector, the method comprising:

[0007] Step 1: for a coincidence event of a multiplexed readout positron emission tomography (PET) detector, a double-ended four-corner readout 8-channel output signal is obtained, the amplitude of the output signal is extracted, and the hit position and depth of interaction (DOI) index are calculated;

[0008] Step 2: the time information of the 8-channel output signal is extracted, the amplitude obtained in step 1 is used for weighting, and the original time of the particle reaching the two detectors of the coincidence event is calculated;

[0009] Step 3: a three-dimensional index is established for the hit position and DOI obtained in step 1, each three-dimensional index corresponds to a delay time, and the original time of the two detectors is equal after subtracting the corresponding delay time;

[0010] Step 4: for each coincidence event of the PET detector, the operations of steps 1-3 are repeated, a system of over-determined equations about the delay time corresponding to all three-dimensional indexes of the two detectors is established, and the delay time corresponding to each three-dimensional index of the two detectors is calculated;

[0011] Step 5, according to the delay time obtained in step 4, a three-dimensional index-delay time lookup table is established, the original time of each event is subtracted by the delay time corresponding to the three-dimensional index to obtain the corrected time, and the time correction of the PET detector is realized.

[0012] A time correction device of a multiplexed readout type PET detector, the device comprising:

[0013] An output signal extraction module is configured to extract the amplitude of the output signal from the dual-end four-corner readout 8-channel output signal for a coincidence event of a multiplexed readout type positron emission tomography (PET) detector, and calculate the hit position and depth of interaction (DOI);

[0014] An original time acquisition module is configured to extract the time information of the 8-channel output signal, and calculate the original time of the coincidence event of the particles reaching the two detectors by weighting the amplitude obtained by the output signal extraction module;

[0015] An index establishment module is configured to establish a three-dimensional index for the hit position and DOI obtained by the output signal extraction module, each three-dimensional index corresponds to a delay time, and the original time of the two detectors is equal after being subtracted by the respective delay time;

[0016] A delay time acquisition module is configured to repeat the operation of the output signal extraction module, the original time calculation module and the index establishment module for each coincidence event of the PET detector, establish an overdetermined equation system about the delay time corresponding to all three-dimensional indexes of the two detectors, and calculate the delay time corresponding to each three-dimensional index of the two detectors;

[0017] A corrected time acquisition module is configured to establish a three-dimensional index-delay time lookup table according to the delay time obtained by the delay time acquisition module, and subtract the delay time corresponding to the three-dimensional index from the original time of each event to obtain the corrected time.

[0018] As can be seen from the technical solutions provided by the above-mentioned application, the above-mentioned method and device are for a multiplexed readout type PET detector, the digital waveforms of different channels after multiplexing in the coincidence event are processed, the signal delay of the detector is corrected, the influence of the inherent delay time of the crystal and the electronic circuit on the final time information measurement is reduced, and thus the time precision of the PET is improved, which is conducive to improving the imaging quality of the PET. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 A flow chart of a time correction method of a multiplexed readout PET detector provided by an embodiment of the present application is shown in the figure;

[0021] Figure 2 A structural schematic diagram of the device according to the embodiment of the present application is shown in the figure;

[0022] Figure 3 A principle schematic diagram of a PET system according to the embodiment of the present application is shown in the figure;

[0023] Figure 4 A time difference distribution schematic diagram of two detectors only with amplitude weighting according to the embodiment of the present application is shown in the figure;

[0024] Figure 5 A time difference distribution schematic diagram of two detectors with corrected time according to the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application, which does not constitute a limitation of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0026] As Figure 1 A flow chart of a time correction method of a multiplexed readout PET detector provided by an embodiment of the present application is shown in the figure, the method comprising:

[0027] Step 1, for a coincidence event of a multiplexed readout positron emission tomography (PET) detector, double-end four-corner readout 8-channel output signals are obtained, the amplitudes of the output signals are extracted, and the hit position and depth of interaction (DOI) are calculated;

[0028] In this step, two face-to-face arranged detectors are used to ensure that the detection surfaces are aligned and the central axes are coincident; a point source or a line source radiation body is placed at the midpoint of the axis for emitting γ rays; after the emitted γ rays hit the crystal, the two detectors simultaneously generate response signals, coincidence events are screened through a time window, and then double-end four-corner readout 8-channel output signals are obtained;

[0029] The digital waveforms of the 8-channel output signals are synchronously collected by using a multi-channel analog-to-digital converter (ADC), the amplitudes of the digital waveforms are extracted, the hit position is calculated, and the depth of interaction (DOI) at the position where the annihilation photons are generated is calculated;

[0030] Where, for one detector, the amplitude information of the digital waveform of the 8-channel output signal is extracted, denoted as , represents the amplitude value of the i-th channel of the detector q; i = 1, 2, …, 8; q represents the hit detector, q = A or B, that is, detector A or detector B;

[0031] The hit position is calculated by the barycenter method, denoted as:

[0032] (1)

[0033] (2)

[0034] Where, , is the position of the event hitting the detector q;

[0035] The action depth index of each event is calculated at the same time , denoted as:

[0036] (3)

[0037] Where, , represents the sum of the amplitudes of each channel of the electronics close to the radiation source side; , represents the sum of the amplitudes of each channel of the electronics away from the radiation source side.

[0038] Step 2, extract the time information of the 8-channel output signal, and use the amplitude obtained in step 1 to weight, calculate the original time of the coincidence event of the particles reaching the two detectors;

[0039] In this step, the original time of the particle reaching the detector q The formula is:

[0040] (4)

[0041] Where, represents the time information of the i-th channel of the detector q.

[0042] Step 3, establish a three-dimensional index for the hit position and DOI obtained in step 1, and each three-dimensional index corresponds to a delay time, so that the original time of the two detectors is equal after subtracting the respective delay time;

[0043] In this step, the hit position obtained in step 1 is classified into discrete crystal positions, specifically, the hit position , is classified into the nearest neighbor crystal position , ; Where, , represents the crystal corresponding to the event hit position, row, and the column of the crystal, =1,2,…,L, =1,2,…,L; L represents that the detector uses a crystal array of ;

[0044] The action depth index DOI is discretely represented, and is specifically represented as a DOI discrete interval ( ), represents the interval corresponding to the event occurrence position, =1,2,…,H; H represents the number of partitions of the DOI discrete interval;

[0045] A three-dimensional index is established for each crystal position and DOI discrete interval, and each three-dimensional index corresponds to a delay time. The original time of the s-th event detector q is recorded as , the crystal position and DOI discrete interval of the s-th event hit are ( , , ), and the corresponding crystal and electronic circuit inherent delay time is ;

[0046] The original times of two detectors, i.e., detector A and detector B, are equal after subtracting the respective corresponding delay times. The following equation is established:

[0047] (5)

[0048] represents the original time of the s-th event detector A; represents the delay time corresponding to the s-th event detector A; represents the original time of the s-th event detector B; represents the delay time corresponding to the s-th event detector B.

[0049] Step 4, for each coincidence event of the PET detector, repeat the operations of steps 1-3 to establish an overdetermined equation group about the delay times corresponding to all three-dimensional indexes of the two detectors, and calculate the delay times corresponding to the three-dimensional indexes of the two detectors;

[0050] In this step, the operations of steps 1-3 are repeated Num times for Num coincidence events. An overdetermined equation group is established. To meet the condition for establishing the overdetermined equation group, it is required that ; L represents that the detector uses a crystal array of ; H represents the number of partitions of the DOI discrete interval; ​

[0051] The established overdetermined equations are expressed in matrix form as follows:

[0052] (6)

[0053] That is,

[0054] (7)

[0055] wherein, represents a column vector composed of the delay time corresponding to all three-dimensional indexes of the detector q; to represents the delay time corresponding to the three-dimensional coordinate point of the detector q being 1 to the three-dimensional coordinate point of the detector q being . represents a column vector composed of the original time of the detector q; to represents the original time of the first to the Numth coincidence event of the detector q, and Num is the number of coincidence events; is a coefficient matrix of the detector q, and the corresponding element of the coefficient matrix is 1 only if the event s hits the three-dimensional coordinate point r of the detector q, and is 0 otherwise; to represents the corresponding coefficient of the first coincidence event of the detector q and the three-dimensional coordinate point being 1 to the Numth coincidence event of the detector q and the three-dimensional coordinate point being .

[0056] The coordinate r is determined by three-dimensional indexes , , , ; represents the crystal position corresponding to the th row hit by the event s; represents the crystal position corresponding to the th row hit by the event s; represents the th interval corresponding to the position where the event s occurs; q represents the hit detector, q=A or B.

[0057] In a specific implementation, the overdetermined equations are solved by using the least square method to obtain the delay time corresponding to all three-dimensional indexes of the two detectors; wherein, represents the delay time at the coordinate r corresponding to the three-dimensional index of the detector q, and the formula for restoring the original three-dimensional index from r is:

[0058] (8)

[0059] (9)

[0060] (10)

[0061] MOD represents a remainder function.

[0062] Step 5, according to the delay time obtained in step 4, a three-dimensional index-delay time lookup table is established, the original time of each event is subtracted by the delay time corresponding to the three-dimensional index to obtain the corrected time, and time correction of the PET detector is realized.

[0063] In this step, specifically, a three-dimensional index-delay time lookup table is established according to the delay time obtained in step 4, and is stored in the PET detector;

[0064] For each single event, first, the original time of the event hitting each detector is obtained, and then the three-dimensional index is determined according to the amplitude;

[0065] Then, the corresponding delay time is searched according to the established three-dimensional index-delay time lookup table;

[0066] Finally, the corrected time is obtained by subtracting the corresponding delay time from the original time, and the expression of the corrected time is as follows:

[0067] (11)

[0068] wherein, is the original time of the s-th event detector q; represents the delay time corresponding to the s-th event detector q; q represents a hit detector, q=A or B.

[0069] Based on the above method embodiment, the embodiment of the application further provides a time correction device for a multiplexed readout type PET detector, as shown in Figure 2 The device includes:

[0070] An output signal extraction module is configured to extract the amplitude of the output signal, calculate the hit position and the depth of interaction (DOI) index, and output the 8-channel output signal of the dual-end four-corner readout for a coincidence event of the multiplexed readout type positron emission tomography (PET) detector.

[0071] An original time acquisition module is configured to extract the time information of the 8-channel output signal, perform weighting using the amplitude obtained by the output signal extraction module, and calculate the original time of the coincidence event of the particles reaching the two detectors.

[0072] An index establishing module is configured to establish a three-dimensional index for the hit position and DOI obtained by the output signal extraction module, each three-dimensional index corresponding to a delay time, so that the original time of the two detectors is equal after subtracting the respective delay time;

[0073] A delay time obtaining module is configured to repeatedly perform the operations of the output signal extraction module, the original time calculation module and the index establishing module for each coincidence event of the PET detector, to establish an over-determined equation group about the delay time corresponding to all three-dimensional indexes of the two detectors, and to calculate the delay time corresponding to each three-dimensional index of the two detectors.

[0074] A correction time obtaining module is configured to establish a three-dimensional index-delay time lookup table according to the delay time obtained by the delay time obtaining module, and to obtain the correction time by subtracting the delay time corresponding to the three-dimensional index from the original time of each event.

[0075] The specific implementation process of each module in the above device embodiment is described in the method embodiment.

[0076] The embodiment of the application also provides an electronic device, including a memory and a processor, the memory stores a computer program, and the processor is configured to run the computer program to execute the method.

[0077] The embodiment of the application also provides a computer storage medium, which stores a plurality of instructions, the instructions are suitable for being loaded and executed by a processor to execute the method.

[0078] The method of the application will be described in detail below with a specific example, which is completed by a double-ended four-corner readout type PET system, as shown in the following figure: Figure 3 The figure shows the principle schematic diagram of the PET system of the example of the application, the system is composed of two double-ended four-corner readout type PET detector faces, the number of crystals of the detector is 20*20, the central axes coincide, and the midpoint of the axis is placed 22 A Na point source emits gamma rays.

[0079] The time correction method of the multiplex readout type PET detector provided by the application includes the following steps:

[0080] Step 1, for a pair of double-ended four-corner readout type PET detectors, the field programmable gate array FPGA ADC (sampling rate 250 MHz) is used to synchronously collect the 8-channel output signal digital waveform of each detector, and the coincidence event is obtained by time window screening (window width 20 ns). The peak value of the digital waveform is used as its amplitude, and the hit position and DOI are calculated according to the amplitude.

[0081] In this example, the hit position is calculated by the center of gravity method, and the formula is:

[0082]

[0083]

[0084] In this example, the DOI is calculated based on the 8-channel amplitude:

[0085]

[0086] Step 2: Extract the time information of the 8-channel digital waveform using the constant ratio timing method, and perform amplitude weighting by combining it with the amplitude information obtained in Step 1 to calculate the original time when the particle arrives at the detector q.

[0087] In this example, the formula for the original time of particle arrival at detector q is:

[0088]

[0089] Step 3: Classify the hit locations obtained in Step 1 into discrete crystal locations, and discretize the DOI. Establish a three-dimensional index for each crystal location and DOI discrete interval. Each index corresponds to a unique delay time. The original times of the two detectors are equal after subtracting the delay time of the corresponding three-dimensional index.

[0090] In this example, the hit location will be obtained ( , ) Classified to the nearest neighbor crystal position ( , ),in,( , ) indicates the location of the event hit, corresponding to the first Okay, number Array of crystals, =1,2,…,20, =1,2,…,20; the detector uses a 20×20 crystal array; the DOI discretization is represented as , Indicates the location of the event corresponding to the first Each interval =1,2,…,100; The DOI discrete interval is divided into 100 parts.

[0091] In this example, the original time of the s-th event detector q is denoted as... The location of the crystal hit in this event and the DOI range are ( , , The corresponding inherent delay time of the crystal and electronic circuitry is... If the original times of the two detectors are equal after subtracting their respective delay times, the following equation holds:

[0092]

[0093] Step 4: For each coincidence event, repeat the operations from Step 1 to Step 3 to establish an overdetermined system of equations about the delay times of the two detectors, solve the overdetermined system of equations, and obtain the delay times corresponding to each three-dimensional index of the two detectors.

[0094] In this example, a total of 1,146,555 sets of coincident events are obtained. An overdetermined system of equations with 1,146,555 time delay differences can be constructed, which can be expressed as:

[0095]

[0096] in, This represents a column vector consisting of the delay times corresponding to all three-dimensional indices of detector q; This represents the column vector of the raw times of detector q; It is the coefficient matrix of detector q, and its elements = 1 if and only if event s hits the coordinate r corresponding to the three-dimensional index of detector q, otherwise 0;

[0097] The coordinate r is determined by the three-dimensional index in step 3 ( , , )Decide, Parameter values: Num=1,146,555; L=20; H=100;

[0098] Find the least-squares solution to the overdetermined system of equations to obtain the relative delay values ​​for all three-dimensional indices.

[0099] Step 5: Build a three-dimensional index-delay time lookup table using the delay time obtained in Step 4 and store it in the PET system equipment;

[0100] For each single event, first obtain the raw time of its impact on each detector, then determine its three-dimensional index based on the amplitude, then retrieve the corresponding delay time from the three-dimensional index-delay time lookup table, and finally subtract the corresponding delay time from the raw time to obtain the final corrected time. The formula is:

[0101]

[0102] In this example, as Figure 4 The diagram shown is a schematic representation of the time difference distribution between two detectors in an example of this invention, where only amplitude weighting is performed. Figure 5The diagram shows the time difference distribution of the two detectors in the example of the present invention for correcting the time. Since two identical detectors are used to measure the time accuracy, the time accuracy should be equal to the FWHM of the time distribution divided by 0. The final timing accuracy was improved from 1.39 ns to 1.08 ns.

[0103] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0104] In summary, compared with methods such as directly averaging the time of all channels or summing the waveforms of all channels before timing, the method and apparatus described in the embodiments of the present invention eliminate the influence of the inherent delay time of different crystals and electronic circuits, and the corrected time accuracy is more accurate, which is beneficial to improving the imaging quality of PET systems; it systematically solves the multi-level delay time problem from detector to electronics, and effectively improves the time resolution of PET systems.

[0105] Furthermore, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware, and the corresponding program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0106] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A time correction method for a multiplexed readout PET detector, characterized in that, The method includes: Step 1: For a single coincidence event of a multiplexed readout positron emission tomography (PET) detector, read out the 8-channel output signal through the four corners of the two ends, extract the amplitude of the output signal, and calculate the DOI (Dot of Impact) index. Step 2: Extract the time information of the 8-channel output signal, use the amplitude obtained in Step 1 to weight it, and calculate the original time when the particles that match the event arrive at the two detectors. Step 3: Establish a three-dimensional index for the hit position and DOI obtained in Step 1. Each three-dimensional index corresponds to a delay time, so that the original times of the two detectors are equal after subtracting their respective delay times. Step 4: For each coincidence event of the PET detector, repeat the operations of steps 1-3 to establish an overdetermined system of equations for the delay times corresponding to all three-dimensional indices of the two detectors, and calculate the delay times corresponding to each three-dimensional index of the two detectors. Step 5: Based on the delay time obtained in Step 4, establish a three-dimensional index-delay time lookup table. Subtract the delay time corresponding to the three-dimensional index from the original time of each event to obtain the corrected time, thereby realizing the time correction of the PET detector.

2. The time correction method for a multiplexed readout PET detector according to claim 1, characterized in that, In step 1, two detectors are arranged face to face to ensure that the detector faces are aligned and the central axes coincide. A point source or line source radiator is placed at the midpoint of the axis to emit gamma rays. After the emitted gamma rays hit the crystal, the two detectors generate response signals simultaneously. The coincidence events are filtered through a time window and then the 8-channel output signals are read out through the four corners of the two ends. The digital waveforms of the 8-channel output signals are synchronously acquired using a multi-channel analog-to-digital converter (ADC). The amplitude of the digital waveforms is extracted, the impact position is calculated, and the depth of action (DOI) at the point where the annihilation photon is generated is calculated. For a single detector, the amplitude information of the digital waveform of the 8-channel output signal is extracted and denoted as... , The amplitude value of the i-th channel of detector q is represented; i = 1, 2, ..., 8; q represents the detector that is hit, q = A or B, that is, detector A or detector B; The point of impact is calculated using the center of gravity method and is represented as follows: （1） （2） in, , The location where the event hits detector q; Simultaneously calculate the impact depth index for each event. , is represented as: （3） in, , representing the sum of the amplitudes of all electronic channels on the side closest to the radiation source; , which represents the sum of the amplitudes of all electronic channels on the side furthest from the radiation source.

3. The time correction method for a multiplexed readout PET detector according to claim 2, characterized in that, In step 2, the initial time of the particle arriving at detector q The formula is: （4） in, This represents the time information of the i-th channel of detector q.

4. The time correction method for a multiplexed readout PET detector according to claim 2, characterized in that, In step 3, the impact locations obtained in step 1 are categorized into discrete crystal locations, specifically, the impact locations ( , ) Classified to the nearest neighbor crystal position ( , );in,( , ) indicates the location of the event hit, corresponding to the first Okay, number Array of crystals, =1,2,…,L, =1,2,…,L; L indicates that the detector used is... Crystal array; The depth of action index (DOI) is discretized, specifically represented as a discrete interval of DOI (…). ), Indicates the location of the event corresponding to the first Each interval =1,2,…,H; H represents the number of discrete intervals to be divided in the DOI; A three-dimensional index is established for each crystal location and DOI discrete interval. Each three-dimensional index corresponds to a delay time. The original time of the detector q for the s-th event is denoted as... The location of the crystal hit by the s-th event and the discrete interval of the DOI are ( , , The corresponding inherent delay time of the crystal and electronic circuitry is... ; To make the original times of the two detectors, namely detector A and detector B, equal after subtracting their respective delay times, the following equation holds: （5） This represents the initial time of detector A during the s-th event; This represents the delay time corresponding to detector A for the s-th event; This represents the original time of detector B during the s-th event; This represents the delay time corresponding to detector B for the s-th event.

5. The time correction method for a multiplexed readout PET detector according to claim 4, characterized in that, In step 4, for Num coincidence events, the operations of steps 1-3 are repeated Num times to establish an overdetermined system of equations. To satisfy the conditions for establishing an overdetermined system of equations, it is necessary to... L indicates that the detector uses The crystal array, where H represents the number of segments into which the DOI discrete interval is divided; The established overdetermined system of equations is represented in matrix form: （6） Right now: （7） in, This represents a column vector consisting of the delay times corresponding to all three-dimensional indices of detector q; to This indicates that the detector q's three-dimensional coordinates are from 1 to 3-dimensional coordinates. The corresponding delay time; This represents the column vector of the raw times of detector q; to This represents the original time from the 1st to the Numth coincidence event of detector q, where Num is the number of coincidence events; This is the coefficient matrix of detector q, where each element is the coefficient of detector q if and only if event s hits the three-dimensional coordinate point r of detector q. The value is 1 if it is 1, otherwise it is 0. to This indicates the first coincidence event of detector q with 3D coordinates 1 to the Numth coincidence event with 3D coordinates 1. The corresponding coefficients; The coordinate r is determined by the three-dimensional index ( , , )Decide, ; This indicates that the position where event s hits corresponds to the first The crystal position of the row; This indicates that the position where event s hits corresponds to the first The crystal position of the row; Indicates the location where event s occurs, corresponding to the first... An interval; q represents the detector that was hit, q=A or B.

6. The time correction method for a multiplexed readout PET detector according to claim 5, characterized in that, In step 4, the overdetermined equations are solved using the least squares method to obtain the delay times corresponding to all three-dimensional indices of the two detectors. ;in, The formula for restoring the original 3D index from the coordinate r corresponding to the 3D index of detector q is: （8） （9） （10） MOD stands for Modulo function.

7. The time correction method for a multiplexed readout PET detector according to claim 5, characterized in that, In step 5, a three-dimensional index-delay time lookup table is specifically built based on the delay time obtained in step 4 and stored in the PET detector; For each single event, the raw time when the event hits each detector is first obtained, and then the three-dimensional index is determined based on the amplitude; Then, the corresponding delay time is retrieved based on the established three-dimensional index-delay time lookup table; Finally, the corrected time is obtained by subtracting the corresponding delay time from the original time. The expression is: （11） in, Let q be the original time of the s-th event detector; Let represent the delay time corresponding to detector q for the s-th event; q represents the detector that was hit, q = A or B.

8. A time correction device for a multiplexed readout type PET detector, characterized in that, The device includes: The output signal extraction module is used to read out the 8-channel output signal from the double-ended four corners of a single coincidence event of a multiplexed readout positron emission tomography (PET) detector, extract the amplitude of the output signal, and calculate the DOI (Dot of Impact) index. The raw time acquisition module is used to extract the time information of the 8-channel output signal. The amplitude obtained by the output signal extraction module is weighted to calculate the raw time of the particles that meet the event arrival at the two detectors. The index building module is used to build a three-dimensional index for the hit position and DOI obtained by the output signal extraction module. Each three-dimensional index corresponds to a delay time, so that the original time of the two detectors is equal after subtracting their respective delay times. The delay time acquisition module is used to repeat the operations of the signal extraction module, the raw time calculation module, and the index building module for each coincidence event of the PET detector, to establish an overdetermined set of equations about the delay time corresponding to all three-dimensional indices of the two detectors, and to calculate the delay time corresponding to each three-dimensional index of the two detectors. The time correction module is used to build a three-dimensional index-delay time lookup table based on the delay time obtained by the delay time acquisition module. The corrected time is obtained by subtracting the delay time corresponding to the three-dimensional index from the original time of each event.

9. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method according to any one of claims 1 to 7.

10. A computer storage medium, characterized in that, The computer storage medium stores a plurality of instructions adapted for loading by a processor and executing the method of any one of claims 1 to 7.

Images