PET detector crystal energy lookup table correction method and imaging method and system

Abstract

The invention relates to a correction method of a PET detector crystal energy lookup table and an imaging method and system.The correction method of the PET detector crystal energy lookup table comprises the steps that a first analog-to-digital conversion value of each crystal under standard annihilation photon energy is obtained; determining a threshold interval corresponding to each first analog-to-digital conversion value, and obtaining an energy event count value of each crystal in the corresponding threshold interval; furthermore, when the energy event count values are not in the same magnitude, a corresponding first energy lookup table is established based on second analog-to-digital conversion values of different depth positions in each crystal under standard annihilation photon energy. According to the method and the device, the problem that an accurate energy lookup table cannot be generated is solved, and the accuracy of energy measurement and positioning in the PET image reconstruction process is improved.

Description

Technical Field

[0001] The present application relates to the technical field of PET, and particularly to a calibration method and an imaging method and system for a crystal energy lookup table of a PET detector. Background Art

[0002] Positron Emission Tomography (PET) technology is an advanced imaging technology in the field of nuclear medicine and is widely used in disease detection, such as the diagnosis of malignant tumors, nervous system and brain diseases.

[0003] The imaging principle of a PET system is to use a front-end detector to detect a pair of gamma photons generated by positron annihilation radiation, obtain the energy, time and position information of the two correlated gamma photons, and process the detected information to reconstruct an image. In a PET system, an Analog to Digital Converter (ADC) is used to convert the continuous analog signal received by the PET detector into a discrete digital signal. The ADC value represents the sampling value of the analog-to-digital converter, and the corresponding gamma photon energy can be calculated using the ADC value. Therefore, it is necessary to establish a lookup table of ADC values corresponding to the crystal energy peak, also known as the crystal energy lookup table, to ensure the accuracy of energy measurement and positioning during the PET image reconstruction process.

[0004] However, in the prior art, only the lookup table of ADC values corresponding to the crystal energy peak is disclosed, and the lookup table is not verified and corrected, so an accurate energy lookup table cannot be generated, reducing the accuracy of energy measurement and positioning during the PET image reconstruction process.

[0005] Regarding the problem that an accurate energy lookup table cannot be generated in the related art, no effective solution has been proposed yet. Summary of the Invention

[0006] In this embodiment, a calibration method and an imaging method and system for a crystal energy lookup table of a PET detector are provided to solve the problem that an accurate energy lookup table cannot be generated in the related art.

[0007] In a first aspect, in this embodiment, a calibration method for a crystal energy lookup table of a PET detector is provided, and the method includes:

[0008] Obtain the first analog-to-digital conversion value of each crystal at the standard annihilation photon energy;

[0009] Determine the threshold interval corresponding to each of the first analog-to-digital conversion values, and obtain the energy event count value of each crystal within the corresponding threshold interval;

[0010] When the energy event count values are not of the same order of magnitude, a corresponding first energy lookup table is established based on the second analog-to-digital conversion values at different depth positions in each crystal at the standard annihilation photon energy.

[0011] In some embodiments, the obtaining the first analog-to-digital conversion values of each crystal at the standard annihilation photon energy includes:

[0012] Based on the standard annihilation photon energy, peak searching is performed on the active energy spectrum of each crystal to obtain the first analog-to-digital conversion value of the crystal.

[0013] In some embodiments, the determining the threshold interval corresponding to each first analog-to-digital conversion value includes:

[0014] Performing an operation on the first analog-to-digital conversion value according to a preset ratio to obtain the upper threshold and the lower threshold of the first analog-to-digital conversion value;

[0015] Based on the upper threshold and the lower threshold, determine the threshold interval corresponding to the first analog-to-digital conversion value.

[0016] In some embodiments, after obtaining the energy event count values of each crystal within the corresponding threshold interval, it further includes:

[0017] Judging whether the energy event count values are of the same order of magnitude; wherein, the same order of magnitude means that the orders of magnitude of the energy event count values are the same.

[0018] In some embodiments, when the energy event count values are not of the same order of magnitude, the establishing a corresponding first energy lookup table based on the second analog-to-digital conversion values at different depth positions in each crystal at the standard annihilation photon energy includes:

[0019] When the energy event count values are not of the same order of magnitude, based on the standard annihilation photon energy, peak searching is performed on the active energy spectrum of different depth positions in each crystal to obtain the second analog-to-digital conversion value corresponding to each depth position;

[0020] Based on different depth positions in each crystal and the corresponding second analog-to-digital conversion values, establish the first energy lookup table.

[0021] In some embodiments, after establishing a corresponding first energy lookup table based on the second analog-to-digital conversion values at different depth positions in each crystal at the standard annihilation photon energy when the energy event count values are not of the same order of magnitude, it further includes:

[0022] Determine whether the second analog-to-digital conversion value conforms to the negative correlation characteristic with the depth value of the depth position; the depth value is the distance between different depth positions in each crystal and the photoelectric converter;

[0023] When the second analog-to-digital conversion value does not conform to the negative correlation characteristic with the depth value of the depth position, correct the first energy lookup table to obtain a second energy lookup table.

[0024] In some embodiments, the correcting the first energy lookup table to obtain a second energy lookup table includes:

[0025] Use the second analog-to-digital conversion value that does not conform to the negative correlation characteristic in the first energy lookup table as the value to be corrected;

[0026] Obtain the adjacent values on both sides of each value to be corrected;

[0027] Based on the adjacent values on both sides of the value to be corrected, update the value to be corrected in the first energy lookup table to obtain the second energy lookup table.

[0028] In some embodiments, the updating the value to be corrected in the first energy lookup table based on the adjacent values on both sides of the value to be corrected to obtain the second energy lookup table includes:

[0029] Perform an average operation on the adjacent values on both sides of the value to be corrected to obtain the average value of the adjacent values;

[0030] Replace each value to be corrected with the corresponding average value to obtain the second energy lookup table.

[0031] In a second aspect, a PET imaging method is provided in this embodiment, and the method includes:

[0032] Based on the analog-to-digital conversion values at different depth positions in each crystal under the standard annihilation photon energy, establish a corresponding first energy lookup table;

[0033] When the analog-to-digital conversion value does not conform to the negative correlation characteristic with the depth value of the depth position, correct the first energy lookup table to obtain a second energy lookup table;

[0034] According to the second energy lookup table, screen out the associated gamma photon pairs generated by positron annihilation in each crystal;

[0035] Based on the relevant information of the associated gamma photon pairs, reconstruct the target image.

[0036] In a third aspect, a PET imaging system is provided in this embodiment, including a PET scanning device, a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the correction method of the PET detector crystal energy lookup table described in the first aspect or the PET imaging method described in the second aspect is implemented.

[0037] In a fourth aspect, a storage medium is provided in this embodiment, on which a computer program is stored. When the program is executed by a processor, the correction method of the PET detector crystal energy lookup table described in the first aspect or the PET imaging method described in the second aspect is implemented.

[0038] Compared with the related art, in the correction method, imaging method, and system of the PET detector crystal energy lookup table provided in this embodiment, by obtaining the first analog-to-digital conversion value of each crystal at the standard annihilation photon energy; determining the threshold interval corresponding to each first analog-to-digital conversion value, and obtaining the energy event count value of each crystal within the corresponding threshold interval; further, when the energy event count values are not in the same order of magnitude, based on the second analog-to-digital conversion value of different depth positions in each crystal at the standard annihilation photon energy, a corresponding first energy lookup table is established, solving the problem of being unable to generate an accurate energy lookup table, and achieving the improvement of the accuracy of energy measurement and positioning in the PET image reconstruction process.

[0039] Details of one or more embodiments of the present application are set forth in the following drawings and description, so that other features, objects, and advantages of the present application will become more concise and understandable. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0041] Figure 1 is a schematic structural diagram of a PET imaging system provided by an embodiment of the present application;

[0042] Figure 2 is a flowchart of a method for correcting a PET detector crystal energy lookup table provided by an embodiment of the present application;

[0043] Figure 3 is a flowchart of a PET imaging method provided by an embodiment of the present application;

[0044] Figure 4 is a flowchart of a method for correcting a PET detector crystal energy lookup table provided by a preferred embodiment of the present application;

[0045] Figure 5 It is a structural block diagram of a correction device for a PET detector crystal energy lookup table provided by an embodiment of the present application.

[0046] In the figure: 100, PET imaging system; 110, PET scanning device; 112, detector assembly; 113, scanning area; 114, mobile platform; 120, network; 130, terminal; 131, mobile device; 132, tablet computer; 133, laptop computer; 140, processing device; 150, storage device; 10, acquisition module; 20, counting module; 30, establishment module. Detailed implementation manners

[0047] To more clearly understand the purpose, technical solution and advantages of the present application, the present application will be described and illustrated below with reference to the accompanying drawings and embodiments.

[0048] Unless otherwise defined, the technical terms or scientific terms involved in the present application shall have the general meaning understood by those with ordinary skills in the technical field to which the present application belongs. In the present application, words such as "a", "one", "a kind of", "the", "these" and the like do not indicate a limitation in quantity, and they can be singular or plural. The terms "including", "comprising", "having" and any variants thereof involved in the present application are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The terms "connected", "coupled" and the like involved in the present application do not limit to physical or mechanical connections, but may include electrical connections, whether directly or indirectly connected. The "plurality" involved in the present application refers to two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third" and the like involved in the present application are only used to distinguish similar objects and do not represent a specific sorting for the objects.

[0049] The method embodiments provided in this embodiment can be executed on a terminal, a computer or a similar computing device. Figure 1 It is a schematic structural diagram of the PET imaging system of this embodiment, as Figure 1As shown, the PET imaging system 100 includes a PET scanning device 110, a network 120, a terminal 130, a processing device 140, and a storage device 150. The components of the PET imaging system 100 can be connected in various ways. Exemplarily, the PET scanning device 110 can be connected to the processing device 140 via the network 120; the PET scanning device 110 can be directly connected to the processing device 140; the storage device 150 can be directly or via the network 120 connected to the processing device 140 (as shown by the bidirectional arrow in the dashed line connecting the PET scanning device 110 and the processing device 140).

[0050] The PET scanning device 110 can scan a target and / or generate scan data regarding the target. In some embodiments, the target can be a living being such as a patient, an animal, etc., or an artificial object such as a phantom, and the target can also be a specific part such as an organ and / or tissue of a patient. When the target needs to be scanned, it can be placed on the mobile platform 114 and move along the longitudinal direction of the PET scanning device 110 with the mobile platform 114 and enter the scanning area 113. Exemplarily, the PET scanning device 110 can be a medical imaging device, such as a PET device, a PET-CT device, a PET-MRI device, etc. The PET scanning device 110 can include a detector assembly 112. After the target enters the scanning area 113, the detector assembly 112 can detect radiation events occurring in the scanning area 113. In some embodiments, the detector assembly 112 can include one or more detectors, and the detectors can be arranged in any suitable shape, such as a combination of one or several of a ring, an arc, a rectangle, an array, etc.

[0051] The network 120 includes any suitable network that can facilitate the exchange of information and / or data of the PET imaging system 100. In some embodiments, one or more components of the PET imaging system 100 can transmit information and / or data to one or more other components of the PET imaging system 100 via the network 120. In some embodiments, examples of the network 120 include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof. In some embodiments, the network 120 can include one or more network access points. For example, the network 120 can include wired and / or wireless network access points, such as base stations and / or Internet exchange points, through which one or more components of the PET imaging system 100 can be connected to the network 120 to exchange data and / or information.

[0052] The terminal 130 includes a mobile device 131, a tablet computer 132, a laptop computer 133, etc., or any combination thereof. In some embodiments, the terminal 130 can interact with other components in the PET imaging system 100 via a network. For example, the terminal 130 can send one or more control instructions to the PET scanning device 110 to control the mobile platform 114 to carry the target into the scanning area 113 and control the detector assembly 112 to receive data. In some embodiments, the terminal 130 can receive information and / or instructions input by a user and send the received information and / or instructions to the PET scanning device 110 or the processing device 140 via the network 120. In some embodiments, the terminal 130 can be a part of the processing device 140. The terminal 130 and the processing device 140 can be integrated into one body as a control device of the PET scanning device 110, for example, an operating console. In some embodiments, the terminal 130 can be omitted.

[0053] The processing device 140 can process data and / or information obtained from the PET scanning device 110, the terminal 130, and / or the storage device 150. Exemplarily, the processing device 140 can acquire the motion information of the target object; the processing device 140 can acquire the collected scanning data from the PET scanning device; the processing device 140 can also correct the relevant parameters of the PET scanning device 110 based on the data obtained above. In some embodiments, the processing device 140 can be a single server or a server group.

[0054] The processing device 140 can be directly connected to the PET scanning device 110 (as shown by the bidirectional arrow in the dashed line connecting the processing device 140 and the PET scanning device 110 in Figure 1 ), the terminal 130 (as shown by the bidirectional arrow in the dashed line connecting the processing device 140 and the terminal 130 in Figure 1 ), and / or the storage device 150 to access the stored or acquired information and / or data.

[0055] The storage device 150 can store data and / or instructions. In some embodiments, the storage device 150 can store data obtained from the PET scanning device 110, the terminal 130, and / or the processing device 140. In some embodiments, the storage device 150 can store data and / or instructions that the processing device 140 can execute or use to execute the exemplary methods described in this application. In some embodiments, the storage device 150 can include a mass storage device, a removable storage device, a volatile read-write memory, etc., or any combination thereof.

[0056] In this embodiment, a method for correcting a PET detector crystal energy lookup table is provided. Figure 2 is a flowchart of the method for correcting the PET detector crystal energy lookup table in this embodiment, asFigure 2 As shown, the process includes the following steps:

[0057] Step S220: Obtain the first analog-to-digital conversion value of each crystal at the standard annihilation photon energy.

[0058] It should be noted that a PET detector usually includes multiple arranged scintillation crystals, and each crystal is used to detect gamma photons generated by positron emission to obtain the energy, time, and position information of two associated gamma photons.

[0059] Specifically, based on the standard annihilation photon energy of 511 keV, peak searching is performed on the active energy spectrum of each crystal to obtain the first analog-to-digital conversion value of each crystal at 511 keV energy, that is, the ADC value corresponding to each crystal. Among them, the active energy spectrum is used to depict the corresponding relationship between the ADC value and the energy event count value.

[0060] Step S240: Determine the threshold interval corresponding to each first analog-to-digital conversion value, and obtain the energy event count value of each crystal within the corresponding threshold interval.

[0061] Specifically, each first analog-to-digital conversion value is operated according to a preset ratio to obtain the upper threshold and the lower threshold of the first analog-to-digital conversion value, where the preset ratio can be reasonably set according to the actual performance of the PET system.

[0062] Furthermore, according to the upper threshold and the lower threshold, the threshold interval corresponding to the first analog-to-digital conversion value is selected, and using the active energy spectrum of the crystal, the energy event count value of each crystal within the corresponding threshold interval is obtained, that is, the number of positron annihilation events detected by the crystal.

[0063] Step S260: When the energy event count values are not in the same order of magnitude, based on the second analog-to-digital conversion value of different depth positions in each crystal at the standard annihilation photon energy, establish a corresponding first energy lookup table.

[0064] Specifically, when it is detected that the energy event count values are not in the same order of magnitude, that is, it indicates that the difference between the energy event count values is large. At this time, peak searching is performed on the active energy spectrum of different depth positions in each crystal based on 511 keV energy to obtain the second analog-to-digital conversion value corresponding to each depth position, and based on different depth positions and the corresponding second analog-to-digital conversion values in each crystal, a first energy lookup table is established.

[0065] In a PET system, an analog-to-digital converter is used to convert the continuous analog signals received by the PET detectors into discrete digital signals. The ADC value represents the sampling value of the analog-to-digital converter, and the corresponding gamma photon energy can be calculated using the ADC value. Therefore, it is necessary to establish a lookup table for the ADC values corresponding to the crystal energy peaks, also known as the crystal energy lookup table, to ensure the accuracy of energy measurement and positioning during the PET image reconstruction process. However, the existing technology only discloses obtaining the lookup table for the ADC values corresponding to the crystal energy peaks, without validating and correcting the lookup table, and cannot generate an accurate energy lookup table, which reduces the accuracy of energy measurement and positioning during the PET image reconstruction process.

[0066] Compared with the existing technology, the present application obtains the first analog-to-digital conversion values of each crystal at the standard annihilation photon energy; determines the threshold intervals corresponding to each first analog-to-digital conversion value, and obtains the energy event count values of each crystal within the corresponding threshold intervals; further, when the energy event count values are not of the same order of magnitude, based on the second analog-to-digital conversion values at the standard annihilation photon energy at different depth positions in each crystal, a corresponding first energy lookup table is established. Based on this, by determining whether there are significant differences in the energy event statistics corresponding to each crystal, it is determined whether the peak search of the current crystal is incorrect. When the peak search is incorrect, a secondary peak search is performed in combination with the depth effect, and then an energy lookup table can be established according to the analog-to-digital conversion values at different depths, solving the problem of being unable to generate an accurate energy lookup table, and achieving the improvement of the accuracy of energy measurement and positioning during the PET image reconstruction process.

[0067] In some of these embodiments, obtaining the first analog-to-digital conversion values of each crystal at the standard annihilation photon energy includes the following steps:

[0068] Step S221, based on the standard annihilation photon energy, perform peak search on the active energy spectrum of each crystal to obtain the first analog-to-digital conversion value of the crystal.

[0069] It should be noted that during the PET scan, the scintillation crystals in the PET detectors detect the two correlated gamma photons generated by the positron annihilation radiation. The energy of each photon is 511 keV, and by analyzing the energy, time, and position information of the two correlated gamma photons, the PET image reconstruction can be achieved.

[0070] Specifically, based on the 511 keV energy, perform peak search on the active energy spectrum of each crystal to obtain the first analog-to-digital conversion values of each crystal at the 511 keV energy, and establish a crystal energy lookup table according to the obtained first analog-to-digital conversion values. Among them, the active energy spectrum is used to depict the corresponding relationship between the ADC value and the energy event count value.

[0071] In this embodiment, the active energy spectrum of each crystal is peak-searched based on the standard annihilation photon energy to obtain the first analog-to-digital conversion value of the crystal, so as to initially establish a crystal energy lookup table for accurately judging whether the current crystal peak search is incorrect.

[0072] In some of these embodiments, determining the threshold interval corresponding to each first analog-to-digital conversion value includes the following steps:

[0073] Step S241, perform an operation on the first analog-to-digital conversion value according to a preset ratio to obtain the upper threshold and the lower threshold of the first analog-to-digital conversion value;

[0074] Step S242, based on the upper threshold and the lower threshold, determine the threshold interval corresponding to the first analog-to-digital conversion value.

[0075] Specifically, according to the actual performance of the PET system, reasonably set the value ratio of each first analog-to-digital conversion value for determining the upper and lower threshold values of the first analog-to-digital conversion value. In the crystal energy lookup table established based on the first analog-to-digital conversion value, multiply the preset ratio by the first analog-to-digital conversion value to obtain the upper threshold and the lower threshold of the first analog-to-digital conversion value, and select the threshold interval corresponding to the current first analog-to-digital conversion value according to the upper threshold and the lower threshold.

[0076] Exemplarily, the value ratios corresponding to the preset upper threshold and the lower threshold are 105% and 95% respectively. When the first analog-to-digital conversion value is 200, the calculated upper threshold is 210 and the lower threshold is 190. At this time, the threshold interval is (190, 210).

[0077] In this embodiment, perform an operation on the first analog-to-digital conversion value according to a preset ratio to obtain the upper threshold and the lower threshold of the first analog-to-digital conversion value, so that based on the upper threshold and the lower threshold, the threshold interval for statistically counting the number of energy events can be accurately selected.

[0078] In some of these embodiments, after obtaining the energy event count values of each crystal within the corresponding threshold interval, the following steps are further included:

[0079] Step S251, judge whether each energy event count value is within the same order of magnitude; wherein, the same order of magnitude means that the order of magnitude of the energy event count values is the same.

[0080] Specifically, count the number of detected energy events within the threshold interval corresponding to each crystal to obtain multiple energy event count values, and judge whether each energy event count value is within the same order of magnitude, that is, the order of magnitude of each energy event count value is the same.

[0081] It should be noted that if the orders of magnitude of the respective energy event count values are the same, it indicates that the difference in the energy event statistics corresponding to different crystals is small. At this time, it is determined that the crystal peak search is correct, and the currently established crystal energy lookup table does not need to be corrected. If the orders of magnitude of the respective energy event count values are different, it indicates that the difference in the energy event statistics corresponding to different crystals is large, then it is determined that the crystal peak search is incorrect, and the currently established crystal energy lookup table needs to be corrected.

[0082] Through this embodiment, it is determined whether the respective energy event count values are in the same order of magnitude, and the same order of magnitude means that the orders of magnitude of the energy event count values are the same, so as to further determine whether the crystal energy lookup table is accurate.

[0083] In some of these embodiments, when the respective energy event count values are not in the same order of magnitude, based on the second analog-to-digital conversion values at different depth positions in each crystal at the standard annihilation photon energy, a corresponding first energy lookup table is established, including the following steps:

[0084] Step S261, when the respective energy event count values are not in the same order of magnitude, based on the standard annihilation photon energy, perform peak search on the active energy spectra at different depth positions in each crystal to obtain the second analog-to-digital conversion value corresponding to each depth position;

[0085] Step S262, based on different depth positions in each crystal and the corresponding second analog-to-digital conversion values, establish a first energy lookup table.

[0086] It should be noted that when it is detected that the respective energy event count values are not in the same order of magnitude, it indicates that the difference in the energy event statistics corresponding to different crystals is large. At this time, it is determined that the crystal peak search is incorrect, and the currently established crystal energy lookup table needs to be corrected.

[0087] Based on this, the depth position information of gamma photons in the crystal is obtained, and an ADC value lookup table corresponding to 511 keV energy at different depths of each crystal is established to reduce the detection error in combination with the depth effect (Depth of Interaction, abbreviated as DOI). Among them, the depth effect refers to the relationship between the position information and energy information when an energy event occurs in the detector crystal.

[0088] Specifically, within the threshold interval for counting the number of energy events, based on the standard annihilation photon energy of 511 keV, perform peak search on the active energy spectra at different depth positions in each crystal to obtain the second analog-to-digital conversion value corresponding to each depth position, and establish a first energy lookup table according to different depth positions in each crystal and their corresponding second analog-to-digital conversion values.

[0089] In this embodiment, when it is detected that the energy event count values are not in the same order of magnitude, peak searching is performed on the active energy spectra at different depth positions in each crystal within the threshold range to obtain the second analog-to-digital conversion value corresponding to each depth position, thereby improving the accuracy of crystal peak searching. Moreover, an ADC value look-up table corresponding to the 511 keV energy at each depth position of the crystal is established to improve the accuracy of the energy calibration of the PET system.

[0090] In some of these embodiments, when the energy event count values are not in the same order of magnitude, after establishing the corresponding first energy look-up table based on the second analog-to-digital conversion values at different depth positions in each crystal under the standard annihilation photon energy, the following steps are further included:

[0091] Step S271: Determine whether the second analog-to-digital conversion value and the depth value of the depth position conform to the negative correlation characteristic; the depth value is the distance between different depth positions in each crystal and the photoelectric converter.

[0092] Step S272: When the second analog-to-digital conversion value and the depth value of the depth position do not conform to the negative correlation characteristic, correct the first energy look-up table to obtain the second energy look-up table.

[0093] Specifically, after establishing the first energy look-up table, determine whether each second analog-to-digital conversion value and the depth value of the corresponding depth position conform to the negative correlation characteristic, where the depth value is the distance between different depth positions in each crystal and the photoelectric converter. It should be noted that since the detection efficiencies of the scintillation photons generated at different depths in the crystal are different, that is, fewer scintillation photons are detected at the end far from the photoelectric converter, and the ADC value obtained after analog-to-digital conversion processing is lower, the ADC values corresponding to the 511 keV energy at each depth from the end close to the photoelectric converter to the end far from the photoelectric converter in the same crystal show a decreasing trend.

[0094] Furthermore, based on the negative correlation characteristic between the above-mentioned second analog-to-digital conversion value and the depth value, traverse the first energy look-up table. When it is detected that there is a second analog-to-digital conversion value that does not conform to the negative correlation characteristic with the depth value of the depth position, it indicates that some of the analog-to-digital conversion values in the first energy look-up table are abnormal, and the first energy look-up table needs to be corrected to obtain an accurate second energy look-up table.

[0095] In this embodiment, determine whether the second analog-to-digital conversion value and the depth value of the depth position conform to the negative correlation characteristic, where the depth value is the distance between different depth positions in each crystal and the photoelectric converter, and when the second analog-to-digital conversion value and the depth value of the depth position do not conform to the negative correlation characteristic, correct the first energy look-up table, thereby combining the depth effect to reduce the detection error and improve the accuracy of the energy look-up table.

[0096] In some of these embodiments, calibrating the first energy lookup table to obtain a second energy lookup table includes the following steps:

[0097] Taking the second analog-to-digital conversion values in the first energy lookup table that do not conform to the negative correlation characteristic as the values to be calibrated;

[0098] Obtaining the adjacent values on both sides of each value to be calibrated;

[0099] Updating the values to be calibrated in the first energy lookup table based on the adjacent values on both sides of the values to be calibrated to obtain a second energy lookup table.

[0100] Specifically, screening out the second analog-to-digital conversion values in the first energy lookup table that do not conform to the negative correlation characteristic as the values to be calibrated, calculating the reasonable value at the position where the current value to be calibrated is located based on the characteristic that the second analog-to-digital conversion value is negatively correlated with the depth value, and using the reasonable value to realize the automatic calibration of the first energy lookup table to obtain a second energy lookup table.

[0101] In the process of calculating the reasonable value above, obtaining the adjacent values on both sides of the value to be calibrated, and correcting the energy lookup table according to the numerical magnitudes of the respective adjacent values. Exemplarily, replacing the value to be calibrated with the average value of the data before and after the value to be calibrated; processing the second analog-to-digital conversion values in the energy lookup table that conform to the negative correlation characteristic through an interpolation algorithm or a fitting algorithm to predict the reasonable value at the position where each value to be calibrated is located based on the trend presented by the accurate data.

[0102] Through this embodiment, taking the second analog-to-digital conversion values in the first energy lookup table that do not conform to the negative correlation characteristic as the values to be calibrated, obtaining the adjacent values on both sides of each value to be calibrated, and updating the values to be calibrated in the first energy lookup table based on the adjacent values on both sides of the values to be calibrated to obtain a second energy lookup table, thereby combining the depth effect to reduce the detection error and accurately calibrate the energy lookup table.

[0103] In some of these embodiments, updating the values to be calibrated in the first energy lookup table based on the adjacent values on both sides of the values to be calibrated to obtain a second energy lookup table includes the following steps:

[0104] Performing an averaging operation on the adjacent values on both sides of the value to be calibrated to obtain the average numerical value of the adjacent values;

[0105] Replacing each value to be calibrated with the corresponding average numerical value to obtain a second energy lookup table.

[0106] Specifically, obtaining the adjacent values on the left and right sides of the value to be calibrated, and ensuring that both adjacent values are the second analog-to-digital conversion values in the energy lookup table that conform to the negative correlation characteristic. Calculating the average numerical value of each adjacent value, and replacing each value to be calibrated with the corresponding average numerical value to obtain a second energy lookup table.

[0107] It should be noted that when there are consecutively arranged values to be corrected in the energy lookup table, an interpolation algorithm or a fitting algorithm is selected to process the second analog-to-digital conversion values in the lookup table that conform to the negative correlation characteristic, and reasonable values at the positions of the respective values to be corrected are predicted according to the data trend.

[0108] Through this embodiment, average operations are performed on the adjacent values on both sides of the value to be corrected to obtain the average value of the adjacent values, and each value to be corrected is replaced with the corresponding average value, thereby realizing the precise correction of the energy lookup table and improving the accuracy of energy measurement and positioning in the subsequent PET image reconstruction process.

[0109] In this embodiment, a PET imaging method is also provided. Figure 3 is a flowchart of the PET imaging method of this embodiment, as Figure 3 shown, and this process includes the following steps:

[0110] Step S310, based on the analog-to-digital conversion values at different depth positions in each crystal under the standard annihilation photon energy, establish a corresponding first energy lookup table;

[0111] Step S320, when the depth values of the analog-to-digital conversion values and the depth positions do not conform to the negative correlation characteristic, correct the first energy lookup table to obtain a second energy lookup table;

[0112] Step S330, according to the second energy lookup table, screen out the associated gamma photon pairs generated by positron annihilation in each crystal;

[0113] Step S340, based on the relevant information of the associated gamma photon pairs, reconstruct the target image.

[0114] Specifically, based on the standard annihilation photon energy of 511 keV, peak searching is performed on the active energy spectra at different depth positions in each crystal to obtain the corresponding analog-to-digital conversion values at each depth position, thereby establishing a first energy lookup table corresponding to 511 keV energy at each depth position of each crystal layer, that is, an ADC value lookup table.

[0115] Since the detection efficiencies of the scintillation photons generated at different depths in the crystal are different, that is, fewer scintillation photons are detected at the end far from the photoelectric converter, and the ADC value obtained after analog-to-digital conversion processing is lower. The ADC values corresponding to 511 keV energy at each depth from the end close to the photoelectric converter to the end far from the photoelectric converter in the same crystal show a decreasing trend. Based on this, it is judged whether the analog-to-digital conversion values in the first energy lookup table and the depth values of the corresponding depth positions conform to the negative correlation characteristic, where the depth value is the distance between different depth positions in each crystal and the photoelectric converter.

[0116] Further, if it is detected that there are some analog-to-digital conversion values in the look-up table that do not conform to the negative correlation characteristic with the depth value, the adjacent values on both sides of the value to be corrected are obtained, and the energy look-up table is corrected according to the numerical magnitudes of the respective adjacent values to obtain a second energy look-up table.

[0117] Among them, the average value of the data before and after the value to be corrected can be used to replace the value to be corrected, or the second analog-to-digital conversion value that conforms to the negative correlation characteristic in the energy look-up table can be processed through an interpolation algorithm, so as to predict the reasonable value of the position where each value to be corrected is located by using the trend presented by the accurate data.

[0118] After that, according to the second energy look-up table, the associated gamma photon pairs generated by positron annihilation in each crystal are screened out, and the energy, arrival time, position information and other related information of the associated gamma photon pairs are obtained. By analyzing the above related information of the associated gamma photon pairs by a computer, the position of positron emission in the body is reconstructed, thereby generating a target image.

[0119] Through this embodiment, based on the analog-to-digital conversion values at different depth positions in each crystal under the standard annihilation photon energy, a corresponding first energy look-up table is established; when the analog-to-digital conversion value does not conform to the negative correlation characteristic with the depth value of the depth position, the first energy look-up table is corrected to obtain a second energy look-up table. On the basis of accurately establishing the crystal energy look-up table, the associated gamma photon pairs generated by positron annihilation in each crystal are screened out, and the target image is reconstructed based on the related information of the associated gamma photon pairs, realizing high-quality PET imaging.

[0120] The following describes and illustrates this embodiment through preferred embodiments.

[0121] Figure 4 is a flowchart of the correction method for the PET detector crystal energy look-up table of this preferred embodiment, as Figure 4 shown, the correction method for the PET detector crystal energy look-up table includes the following steps:

[0122] Step S410, perform peak searching on the active energy spectrum of each crystal based on the standard annihilation photon energy to obtain the first analog-to-digital conversion value of the crystal;

[0123] Step S420, determine the threshold interval corresponding to each first analog-to-digital conversion value, and obtain the energy event count value of each crystal within the corresponding threshold interval;

[0124] Step S430, when the respective energy event count values are not of the same order of magnitude, perform peak searching on the active energy spectra at different depth positions in each crystal based on the standard annihilation photon energy to obtain the second analog-to-digital conversion value corresponding to each depth position;

[0125] Step S440: Based on the different depth positions and corresponding second analog-to-digital conversion values in each crystal, establish a first energy lookup table;

[0126] Step S450: Determine whether the second analog-to-digital conversion value and the depth value of the depth position conform to the negative correlation characteristic; the depth value is the distance between different depth positions in each crystal and the photoelectric converter;

[0127] Step S460: When the second analog-to-digital conversion value and the depth value of the depth position do not conform to the negative correlation characteristic, correct the first energy lookup table to obtain a second energy lookup table.

[0128] Through this embodiment, peak search is performed on the active energy spectrum of each crystal based on the standard annihilation photon energy to obtain the first analog-to-digital conversion value of the crystal, determine the threshold interval corresponding to each first analog-to-digital conversion value, and obtain the energy event count value of each crystal within the corresponding threshold interval. Thus, it is possible to accurately determine whether the current crystal peak search is incorrect by comparing whether the energy event count values are of the same order of magnitude.

[0129] When the energy event count values are not of the same order of magnitude, peak search is performed on the active energy spectrum of different depth positions in each crystal based on the standard annihilation photon energy to obtain the second analog-to-digital conversion value corresponding to each depth position, so as to establish a first energy lookup table. Further, determine whether the second analog-to-digital conversion value and the depth value of the depth position conform to the negative correlation characteristic, where the depth value is the distance between different depth positions in each crystal and the photoelectric converter, and when the second analog-to-digital conversion value and the depth value of the depth position do not conform to the negative correlation characteristic, correct the first energy lookup table, thereby reducing the detection error using the depth effect and effectively improving the accuracy of the crystal energy lookup table.

[0130] It should be noted that the steps shown in the above process or the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0131] In this embodiment, a correction device for the crystal energy lookup table of a PET detector is also provided. This device is used to implement the above embodiment and the preferred implementation manners, and those that have been described will not be repeated. The following terms "module", "unit", "sub-unit", etc. can be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0132] Figure 5 is the structural block diagram of the correction device for the crystal energy lookup table of the PET detector in this embodiment, asFigure 5 As shown, the device includes: an acquisition module 10, a counting module 20, and a building module 30;

[0133] The acquisition module 10 is configured to acquire a first analog-to-digital conversion value of each crystal at the standard annihilation photon energy;

[0134] The counting module 20 is configured to determine a threshold interval corresponding to each first analog-to-digital conversion value, and acquire an energy event count value of each crystal within the corresponding threshold interval;

[0135] The building module 30 is configured to, when the energy event count values are not of the same order of magnitude, establish a corresponding first energy lookup table based on second analog-to-digital conversion values at different depth positions in each crystal at the standard annihilation photon energy.

[0136] With the device provided in this embodiment, a first analog-to-digital conversion value of each crystal at the standard annihilation photon energy is acquired; a threshold interval corresponding to each first analog-to-digital conversion value is determined, and an energy event count value of each crystal within the corresponding threshold interval is acquired; further, when the energy event count values are not of the same order of magnitude, a corresponding first energy lookup table is established based on second analog-to-digital conversion values at different depth positions in each crystal at the standard annihilation photon energy, solving the problem of being unable to generate an accurate energy lookup table, and achieving improvement in the accuracy of energy measurement and positioning during PET image reconstruction.

[0137] In some embodiments, on the basis of Figure 5 , the device further includes a peak searching module, configured to perform peak searching on the active energy spectrum of each crystal based on the standard annihilation photon energy to obtain the first analog-to-digital conversion value of the crystal.

[0138] In some embodiments, on the basis of Figure 5 , the device further includes a limiting module, configured to perform an operation on the first analog-to-digital conversion value according to a preset ratio to obtain an upper threshold and a lower threshold of the first analog-to-digital conversion value; and determine a threshold interval corresponding to the first analog-to-digital conversion value based on the upper threshold and the lower threshold.

[0139] In some embodiments, on the basis of Figure 5 , the device further includes a judging module, configured to judge whether the energy event count values are of the same order of magnitude; wherein, the same order of magnitude means that the orders of magnitude of the energy event count values are the same.

[0140] In some embodiments, on the basis of Figure 5Based on this, the device further includes a table building module, which is used to find peaks for the active energy spectra at different depth positions in each crystal based on the standard annihilation photon energy when the count values of each energy event are not in the same order of magnitude, so as to obtain the second analog-to-digital conversion value corresponding to each depth position; and establish a first energy lookup table based on different depth positions and the corresponding second analog-to-digital conversion values in each crystal.

[0141] In some of these embodiments, on the Figure 5 basis, the device further includes a calibration module, which is used to determine whether the second analog-to-digital conversion value and the depth value of the depth position conform to the negative correlation characteristic; the depth value is the distance between different depth positions in each crystal and the photoelectric converter; when the second analog-to-digital conversion value and the depth value of the depth position do not conform to the negative correlation characteristic, calibrate the first energy lookup table to obtain a second energy lookup table.

[0142] In some of these embodiments, on the Figure 5 basis, the device further includes an update module, which is used to use the second analog-to-digital conversion value that does not conform to the negative correlation characteristic in the first energy lookup table as the value to be calibrated; obtain the adjacent values on both sides of each value to be calibrated; and update the value to be calibrated in the first energy lookup table based on the adjacent values on both sides of the value to be calibrated to obtain a second energy lookup table.

[0143] In some of these embodiments, on the Figure 5 basis, the device further includes an operation module, which is used to perform an average operation on the adjacent values on both sides of the value to be calibrated to obtain the average value of the adjacent values; and replace each value to be calibrated with the corresponding average value to obtain a second energy lookup table.

[0144] It should be noted that the above-mentioned various modules can be functional modules or program modules, and can be implemented either by software or by hardware. For the modules implemented by hardware, the above-mentioned various modules can be located in the same processor; or the above-mentioned various modules can also be located in different processors in any combined form.

[0145] In addition, in combination with the calibration method of the PET detector crystal energy lookup table provided in the above embodiments, a storage medium can also be provided in this embodiment to implement it. A computer program is stored on the storage medium; when the computer program is executed by a processor, any one of the calibration methods of the PET detector crystal energy lookup table in the above embodiments is implemented.

[0146] It should be understood that the specific embodiments described here are only used to explain this application, rather than to limit it. According to the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0147] Obviously, the accompanying drawings are only some examples or embodiments of the present application. For those of ordinary skill in the art, the present application can also be applied to other similar situations based on these drawings without creative efforts. Additionally, it can be understood that although the work done during the development process here may be complex and time-consuming, for those of ordinary skill in the art, certain design, manufacturing, or production changes based on the technical content disclosed in the present application are only routine technical means and should not be regarded as insufficient disclosure of the present application.

[0148] The term "embodiment" in the present application means that the specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appears at various positions in the specification and does not necessarily mean the same embodiment, nor does it mean being independent or alternative to other embodiments and mutually exclusive. Those of ordinary skill in the art can clearly or implicitly understand that the embodiments described in the present application can be combined with other embodiments without conflict.

[0149] The above-described embodiments only represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of patent protection. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A calibration method for the crystal energy lookup table of a PET detector, characterized in that, the method includes: Obtaining the first analog-to-digital conversion value of each crystal at the standard annihilation photon energy; Determining the threshold interval corresponding to each of the first analog-to-digital conversion values, and obtaining the energy event count value of each crystal within the corresponding threshold interval; When the energy event count values are not in the same order of magnitude, based on the second analog-to-digital conversion value of different depth positions in each crystal at the standard annihilation photon energy, a corresponding first energy lookup table is established.

2. The calibration method for the crystal energy lookup table of a PET detector according to claim 1, characterized in that, the obtaining the first analog-to-digital conversion value of each crystal at the standard annihilation photon energy includes: Based on the standard annihilation photon energy, peak searching is performed on the active energy spectrum of each crystal to obtain the first analog-to-digital conversion value of the crystal.

3. The calibration method for the crystal energy lookup table of a PET detector according to claim 1, characterized in that, the determining the threshold interval corresponding to each of the first analog-to-digital conversion values includes: Performing an operation on the first analog-to-digital conversion value according to a preset ratio to obtain the upper threshold and the lower threshold of the first analog-to-digital conversion value; Based on the upper threshold and the lower threshold, determining the threshold interval corresponding to the first analog-to-digital conversion value.

4. The calibration method for the crystal energy lookup table of a PET detector according to claim 1, characterized in that, after the obtaining the energy event count value of each crystal within the corresponding threshold interval, it further includes: Judging whether the energy event count values are in the same order of magnitude; wherein, the same order of magnitude means that the orders of magnitude of the energy event count values are the same.

5. The calibration method for the crystal energy lookup table of a PET detector according to claim 1, characterized in that, the when the energy event count values are not in the same order of magnitude, based on the second analog-to-digital conversion value of different depth positions in each crystal at the standard annihilation photon energy, establishing a corresponding first energy lookup table includes: When the energy event count values are not in the same order of magnitude, based on the standard annihilation photon energy, peak searching is performed on the active energy spectrum of different depth positions in each crystal to obtain the second analog-to-digital conversion value corresponding to each depth position; Based on different depth positions in each crystal and the corresponding second analog-to-digital conversion values, the first energy lookup table is established.

6. The calibration method for the crystal energy lookup table of a PET detector according to claim 1, characterized in that, after when the energy event count values are not in the same order of magnitude, based on the second analog-to-digital conversion value of different depth positions in each crystal at the standard annihilation photon energy, establishing a corresponding first energy lookup table, it further includes: Judging whether the second analog-to-digital conversion value and the depth value of the depth position conform to the negative correlation characteristic; the depth value is the distance between different depth positions in each crystal and the photoelectric converter. When the second analog-to-digital conversion value does not conform to the negative correlation characteristic with the depth value of the depth position, correct the first energy lookup table to obtain a second energy lookup table.

7. The method for correcting the PET detector crystal energy lookup table according to claim 6, wherein, the correcting the first energy lookup table to obtain a second energy lookup table includes: Regarding the second analog-to-digital conversion value that does not conform to the negative correlation characteristic in the first energy lookup table as a value to be corrected; Obtain the adjacent values on both sides of each value to be corrected; Based on the adjacent values on both sides of the value to be corrected, update the value to be corrected in the first energy lookup table to obtain the second energy lookup table.

8. The method for correcting the PET detector crystal energy lookup table according to claim 7, wherein, the updating the value to be corrected in the first energy lookup table based on the adjacent values on both sides of the value to be corrected to obtain the second energy lookup table includes: Perform an averaging operation on the adjacent values on both sides of the value to be corrected to obtain the average value of the adjacent values; Replace each value to be corrected with the corresponding average value to obtain the second energy lookup table.

9. A PET imaging method, wherein, the method includes: Based on the analog-to-digital conversion values at different depth positions in each crystal under the standard annihilation photon energy, establish a corresponding first energy lookup table; When the analog-to-digital conversion value does not conform to the negative correlation characteristic with the depth value of the depth position, correct the first energy lookup table to obtain a second energy lookup table; According to the second energy lookup table, screen out the associated gamma photon pairs generated by positron annihilation in each crystal; Based on the relevant information of the associated gamma photon pairs, reconstruct the target image.

10. A PET imaging system, including a PET scanning device, a memory, and a processor, wherein, a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps of the method for correcting the PET detector crystal energy lookup table according to any one of claims 1 to 8 or the PET imaging method according to claim 9.

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