Method, system, device and storage medium for correcting scanned images

Abstract

An embodiment of the present specification provides a method and system for correcting a scanned image, the method including obtaining a first baseline background energy response and a first baseline normalized correction factor in a first baseline system state; collecting first background radiation data at a preset time point, generating a first energy response variation based on the first background radiation data and the first baseline background energy response; in response to the first energy response variation being no greater than a preset variation threshold, correcting the scanned image based on the first baseline normalized correction factor; in response to the first energy response variation being greater than the preset variation threshold, generating a first normalized correction factor variation based on the first energy response variation and a preset relationship, generating a first normalized correction factor based on the first normalized correction factor variation, and correcting the scanned image based on the first normalized correction factor.

Description

Technical Field

[0001] The present invention relates to the field of medical technology, and in particular to a method, system, device and storage medium for correcting scanned images. Background Art

[0002] Positron emission tomography (PET) is a rapidly developing imaging technology in the field of nuclear medicine today and is widely used in clinical testing. Among them, the PET-CT system that combines PET and X-ray computed tomography (CT) is often used. The PET-CT system with a long axial field of view has received rapid attention and development due to its extremely high sensitivity. In the PET-CT system, it is necessary to normalize the PET data using a normalization correction factor to obtain quantitatively accurate and artifact-free PET reconstructed images. However, due to changes in the system state, the normalization correction factor needs to be updated regularly. If the update cycle is too long, the mismatch between the normalization correction factor and the system state will gradually increase, making it difficult to ensure the effect of the normalization correction, resulting in a decrease in the quality of clinical scan images.

[0003] Therefore, it is desired to provide a method for correcting a scanned image to ensure the effect of normalization correction. Summary of the Invention

[0004] One embodiment of the present specification provides a method for correcting a scanned image. The method includes: obtaining a first baseline background energy response in a first baseline system state and obtaining a first baseline normalized correction factor based on a phantom; collecting first background radiation data from a detector at a preset time point, generating a first energy response variation based on the first background radiation data and the first baseline background energy response; in response to the first energy response variation being no greater than a preset variation threshold, correcting the scanned image based on the first baseline normalized correction factor; in response to the first energy response variation being greater than the preset variation threshold, generating a first normalized correction factor variation based on the first energy response variation and a preset relationship, generating a first normalized correction factor for the current state based on the first normalized correction factor variation, and correcting the scanned image based on the first normalized correction factor.

[0005] In some embodiments, the preset relationship may include a functional relationship between the change in background energy response and the change in normalized correction factor under different states of the scanning system, and the functional relationship can be obtained in the following manner: collecting second background radiation data and second phantom coincidence event data under a second reference system state; obtaining a second reference background energy response based on the second background radiation data; obtaining a second reference normalized correction factor based on the second phantom coincidence event data; obtaining multiple third background radiation data and multiple third phantom coincidence event data collected under multiple third system states, each system state in the multiple third system states is different from the second reference system state; obtaining multiple second background energy response changes based on the second reference background energy response and the multiple third background radiation data; obtaining multiple second normalized correction factor changes based on the second reference normalized correction factor and the multiple third phantom coincidence event data; and obtaining the functional relationship based on the multiple second background energy response changes and the multiple second normalized correction factor changes.

[0006] In some embodiments, for each of the plurality of third phantom conformance event data, a second normalized correction factor may be obtained based on the third phantom conformance event data; and a second normalized correction factor variation may be obtained based on the second baseline normalized correction factor and the second normalized correction factor.

[0007] In some embodiments, the normalization correction factor may include at least one of an axial profile correction factor, a detector ring pair detection efficiency correction factor, a circumferential profile correction factor, a crystal detection efficiency correction factor, and a time-of-flight calibration factor.

[0008] In some embodiments, the method for correcting a scanned image may include: at the preset time point, after adjusting the lower threshold of the energy window, collecting the first background radiation data and determining whether the first normalized correction factor is obtained.

[0009] In some embodiments, obtaining the background energy response may include: obtaining a first background coincidence event and a second background coincidence event from background radiation data, the first background coincidence event corresponding to a first energy and a first crystal, and the second background coincidence event corresponding to a second energy and a second crystal; determining whether the time of the second background coincidence event is earlier than the time of the first background coincidence event; in response to yes, in the energy response of the first crystal, incrementing the energy box corresponding to the first energy; in response to no, in the energy response of the second crystal, incrementing the energy box corresponding to the second energy.

[0010] One of the embodiments of the present specification provides a system for correcting a scanned image, comprising a correction factor acquisition module, a variation generation module, and an image correction module; the correction factor acquisition module is used to obtain a first baseline background energy response in a first baseline system state, and obtain a first baseline normalized correction factor based on a phantom; the variation generation module is used to collect first background radiation data of a detector at a preset time point, and generate a first energy response variation based on the first background radiation data and the first baseline background energy response; the image correction module is used to: in response to the first energy response variation being no greater than a preset variation threshold, correct the scanned image based on the first baseline normalized correction factor; in response to the first energy response variation being greater than the preset variation threshold, generate a first normalized correction factor variation based on the first energy response variation and a preset relationship, generate a first normalized correction factor of the current state based on the first normalized correction factor variation, and correct the scanned image based on the first normalized correction factor.

[0011] In some embodiments, the preset relationship may include a functional relationship between the change in background energy response and the change in normalized correction factor in different states of the scanning system. The system may further include a functional relationship acquisition module, which may be used to: collect second background radiation data and second model compliance event data in a second reference system state; obtain a second reference background energy response based on the second background radiation data; obtain a second reference normalized correction factor based on the second model compliance event data; obtain multiple third background radiation data and multiple third model compliance event data collected in multiple third system states, each system state in the multiple third system states is different from the second reference system state; obtain multiple second background energy response changes based on the reference background energy response and the multiple third background radiation data; obtain multiple second normalized correction factor changes based on the second reference normalized correction factor and the multiple third model compliance event data; and obtain the functional relationship based on the multiple second background energy response changes and the multiple second normalized correction factor changes.

[0012] One embodiment of the present specification provides a device for correcting a scanned image, comprising a processor, wherein the processor is configured to execute the method for correcting a scanned image.

[0013] One embodiment of the present specification provides a computer-readable storage medium, wherein the storage medium stores computer instructions. When a computer reads the computer instructions in the storage medium, the computer executes the method for correcting a scanned image. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] This specification will be further described in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, like numbers represent like structures, wherein:

[0015] Figure 1 is a schematic diagram of an application scenario of a system for correcting scanned images according to some embodiments of this specification;

[0016] Figure 2 is a schematic diagram of a system for correcting a scanned image according to some embodiments of the present specification;

[0017] Figure 3 is an exemplary flow chart of a method for correcting a scanned image according to some embodiments of the present specification;

[0018] Figure 4 is an exemplary flow chart of a method for correcting a scanned image according to some embodiments of the present specification;

[0019] Figure 5 is an exemplary flow chart of a method for correcting a scanned image according to some embodiments of the present specification;

[0020] Figure 6 is a schematic diagram illustrating changes in system status over time according to some embodiments of this specification;

[0021] Figure 7 is a schematic diagram of the decay energy levels of Lu-176 according to some embodiments of this specification;

[0022] Figure 8 is a schematic diagram of energy response according to some embodiments of this specification;

[0023] Figure 9 is a schematic diagram illustrating changes in energy response due to changes in system state according to some embodiments of this specification;

[0024] Figure 10 is a schematic diagram of a method for obtaining energy responses and normalized correction factors under different system states according to some embodiments of this specification;

[0025] Figure 11 is a schematic diagram of a method for normalizing and correcting clinical scan data according to some embodiments of this specification;

[0026] Figure 12 is a schematic diagram of a method for obtaining background energy response according to some embodiments of this specification;

[0027] Figure 13is a schematic diagram of a cone beam with a crystal as the top according to some embodiments of this specification;

[0028] Figure 14a is a schematic diagram of the distribution of crystal detection efficiency correction factors under a reference system state according to some embodiments of this specification;

[0029] Figure 14b is a schematic diagram of the position distribution of the 307keV energy peak in the reference system state according to some embodiments of this specification;

[0030] Figure 15a is a schematic diagram of the distribution of crystal detection efficiency correction factors after the system state changes according to some embodiments of this specification;

[0031] Figure 15b is a schematic diagram of the position distribution of the 307keV energy peak after the system state changes according to some embodiments of this specification;

[0032] Figure 16a is a schematic diagram of the distribution of changes in the crystal detection efficiency correction factor according to some embodiments of this specification;

[0033] Figure 16b is a schematic diagram of the distribution of the change in the position of the 307keV energy peak according to some embodiments of this specification;

[0034] Figure 17 This is a schematic diagram of the relationship between the change in the crystal detection efficiency correction factor and the change in the 307keV energy peak position according to some embodiments of this specification. DETAILED DESCRIPTION

[0035] To more clearly illustrate the technical solutions of the embodiments of this specification, the following briefly describes the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this specification. Those skilled in the art can apply this specification to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0036] It should be understood that the terms "system," "device," "unit," and / or "module" used herein are a method for distinguishing different components, elements, parts, portions, or assemblies at different levels. However, if other terms can achieve the same purpose, the terms may be replaced by other expressions.

[0037] As used in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not refer to the singular but also include the plural. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements.

[0038] Flowcharts are used throughout this specification to illustrate the operations performed by systems according to embodiments of this specification. It should be understood that preceding or following operations do not necessarily need to be performed in exact order. Instead, the steps may be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0039] During the normalization and correction process for PET data, certain normalization correction factors require regular updating due to changes in system status, such as environmental variations, crystal aging, silicon photomultiplier (SiPM) gain variations, and variations in light collection performance from the crystal to the SiPM. A commonly used approach involves creating a water phantom or scanning with a solid source. The scanned data is then processed to generate normalization correction factors, including axial profile correction factors, detector ring pair detection efficiency correction factors, circumferential profile correction factors, crystal detection efficiency correction factors, and time-of-flight calibration factors. However, this method requires a radioactive source and experienced service engineers or technicians, is time-consuming, consumes clinical scan time, and poses radiation hazards to operators. Regularly updating normalization correction factors can lead to a gradual mismatch between the normalization correction factors and system status if the update interval is too long, making it difficult to maintain the quality of the normalization correction and potentially resulting in a decrease in clinical scan image quality. However, if the update interval is too short, costs and radiation dose to personnel involved (patients and operators) increase.

[0040] Figure 6 This is a schematic diagram showing how the system status changes over time according to some embodiments of this specification. Figure 6 In the coordinate system, the horizontal axis represents time, the vertical axis represents system state, and the diagonal lines in the coordinate system represent changes in system state over time. Point 610 represents the nth regular normalization correction, which occurs at time Tn. Point 620 represents the n+1th regular normalization correction, which occurs at time Tn+1. From time Tn to time Tn+1, the mismatch between the normalization correction factor and the system state gradually increases until the next regular normalization correction occurs.

[0041] Currently, most PET systems use LSO or LYSO crystals, which generate spontaneous background radiation. Long axial field of view (LOF) PET systems, because they use a much larger number of crystals than standard axial field of view (LOF) PET systems, also generate significantly stronger background radiation signals. Generally, changes in system status affect not only clinical scan data but also background scan data. Therefore, by monitoring background data, the correlation between the responses of clinical and background scan data to system status changes can be exploited to predict changes in normalized correction factors. For example, background scan data can be used to determine whether the system status has changed. If so, the background scan data is used to obtain a normalized correction factor at the background energy and then converted to a normalized correction factor at the clinical scan annihilation radiation energy (511 keV) using a pre-stored energy factor conversion coefficient. However, because the response line and the detection efficiency of the detector crystals vary nonlinearly under gamma photon irradiation of different energies, using the energy factor conversion coefficient to convert correction factors at different energies can result in significant errors.

[0042] In some embodiments of the present specification, a method for correcting scanned images is provided. By utilizing the spontaneous background radiation signal of the PET system (based on LSO or LYSO crystals), the changes in the energy response of each response line and each crystal to the background signal are monitored, and the mapping relationship between the response signal and the change in the normalized correction factor is used to predict the change in the normalized correction factor, and a new normalized correction factor is generated. This solves the problem of the gradual increase in the mismatch between the normalized correction factor and the system state between two normalized corrections. There is no need for a radioactive source, the production of a water model, or the use of a solid source, the radiation is low, and the operation is simple. It can be performed automatically outside of clinical scanning time (for example, during non-working hours such as the middle of the night), ensuring that normal clinical use is not interfered with.

[0043] Figure 1 This is a schematic diagram of an application scenario of a system for correcting scanned images according to some embodiments of this specification.

[0044] Hereinafter, the system 100 for correcting a scanned image will be referred to as the system 100. Figure 1 As shown, in some embodiments, the system 100 may include a scanning device 110 , a processing device 120 , a storage device 130 , a terminal 140 , and a network 150 .

[0045] Scanning device 110 refers to a medical device that uses various media to reconstruct internal structures of the human body as images. In some embodiments, scanning device 110 can be any medical device that uses radionuclides to image or treat a specific part of a patient's body, such as PET-CT, PET, single-photon emission computed tomography (SPECT), SPECT-CT, PET-MR, etc. The scanning device 110 described above is for illustrative purposes only and is not intended to limit its scope. Detectors in scanning device 110 can receive radiation from a radiation source and measure the received radiation. In some embodiments, scanning device 110 can transmit detector-related data and information, such as the energy values ​​of radiation photons received by the detectors and the detector output values, to processing device 120. In some embodiments, scanning device 110 can collect background coincidence event data (i.e., background radiation data) and target coincidence event data of a scanned object (e.g., a human body, a phantom, etc.), and transmit these data to processing device 120. In some embodiments, the scanning device 110 can perform normalization calibration on the device based on the normalization correction factor determined by the processing device 120. The scanning device 110 can receive instructions sent by the doctor through the terminal 140, and perform related operations according to the instructions, such as irradiation imaging. In some embodiments, the scanning device 110 can exchange data and / or information with other components in the system 100 (e.g., the processing device 120, the storage device 130, the terminal 140) through the network 150. In some embodiments, the scanning device 110 can be directly connected to other components in the system 100. In some embodiments, one or more components in the system 100 (e.g., the processing device 120, the storage device 130) can be included in the scanning device 110.

[0046] The processing device 120 can process data and / or information obtained from other devices or system components, and based on these data, information and / or processing results, perform the method for correcting the scanned image shown in some embodiments of this specification to complete one or more functions described in some embodiments of this specification. For example, the processing device 120 can obtain the normalization correction factor of the device based on the background coincidence event data of the scanning device 110 and the target coincidence event data of the scan target object (e.g., a phantom such as a water phantom) to perform normalization correction on the scanning device 110. For another example, the processing device 120 can establish a functional relationship between the change in the background energy response of the scanning system under different system states and the change in the normalization correction factor based on the background energy response of the scanning device 110 under different system states. In some embodiments, the processing device 120 can correct the obtained normalization correction factor based on this functional relationship to obtain a new normalization correction factor. In some embodiments, the processing device 120 can obtain pre-stored data and / or information from the storage device 130, such as background compliance event data, target compliance event data, various calculation formulas, etc., for executing the method of correcting the scanned image shown in some embodiments of this specification, such as correcting the normalized correction factor of the scanning device, etc.

[0047] In some embodiments, the processing device 120 may include one or more sub-processing devices (e.g., a single-core processing device or a multi-core multi-core processing device). By way of example only, the processing device 120 may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), a graphics processing unit (GPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), a microcontroller unit (MCU), a reduced instruction set computer (RISC), a microprocessor, or any combination thereof.

[0048] The storage device 130 can store data or information generated by other devices. In some embodiments, the storage device 130 can store data and / or information collected by the scanning device 110, for example, background compliance event data, target compliance event data, etc. In some embodiments, the storage device 130 can store data and / or information processed by the processing device 120, for example, normalization correction factors of the device, etc. The storage device 130 may include one or more storage components, each of which may be an independent device or part of another device. The storage device may be local or implemented through the cloud. In some embodiments, one or more components of the system 100 (for example, the scanning device 110, the processing device 120, the terminal 140) may include their own storage components.

[0049] The terminal 140 can control the operation of the scanning device 110. The doctor can issue operating instructions to the scanning device 110 through the terminal 140 to enable the scanning device 110 to complete the specified operation, for example, irradiate and image the patient's specified body part. In some embodiments, the terminal 140 can instruct the processing device 120 to execute the method of correcting the scanned image as shown in some embodiments of this specification. In some embodiments, the terminal 140 can receive the corrected scanned image, etc. from the processing device 120, so that the doctor can accurately judge the patient's condition and perform effective and targeted examination and / or treatment on the patient. In some embodiments, the terminal 140 can be one of the mobile devices 140-1, tablet computers 140-2, laptop computers 140-3, desktop computers, and other devices with input and / or output functions, or any combination thereof.

[0050] Network 150 can connect the various components of the system and / or connect the system to external resources. Network 150 enables communication between the various components and with other components outside the system, facilitating the exchange of data and / or information. In some embodiments, one or more components in system 100 (e.g., scanning device 110, processing device 120, storage device 130, terminal 140) can send data and / or information to other components via network 150. In some embodiments, network 150 can be any one or more of a wired network and a wireless network.

[0051] It should be noted that the above description is provided for illustrative purposes only and is not intended to limit the scope of this specification. For those skilled in the art, various changes and modifications can be made under the guidance of the contents of this specification. The features, structures, methods and other features of the exemplary embodiments described in this specification can be combined in various ways to obtain additional and / or alternative exemplary embodiments. For example, the processing device 120 can be based on a cloud computing platform, such as a public cloud, a private cloud, a community and a hybrid cloud. However, these changes and modifications do not deviate from the scope of this specification.

[0052] Figure 2 is a schematic diagram of a system for correcting a scanned image according to some embodiments of the present specification.

[0053] like Figure 2 As shown, in some embodiments, the system 200 for correcting scanned images may include a correction factor acquisition module 210 , a variation generation module 220 , and an image correction module 230 . In some embodiments, each module in the system 200 for correcting scanned images may be implemented by the processing device 120 .

[0054] In some embodiments, the correction factor acquisition module 210 may be configured to acquire a first reference background energy response in a first reference system state, and acquire a first reference normalized correction factor based on a phantom.

[0055] In some embodiments, the normalization correction factor may include at least one of an axial profile correction factor, a detector ring pair detection efficiency correction factor, a circumferential profile correction factor, a crystal detection efficiency correction factor, a time-of-flight calibration factor, and the like.

[0056] In some embodiments, the variation generation module 220 may be configured to collect first background radiation data of the detector at a preset time point, and generate a first energy response variation based on the first background radiation data and a first reference background energy response.

[0057] In some embodiments, the image correction module 230 can be used to correct the scanned image based on a first baseline normalized correction factor in response to the first energy response change being no greater than a preset change threshold; generate a first normalized correction factor change based on the first energy response change and a preset relationship in response to the first energy response change being greater than a preset change threshold, generate a first normalized correction factor of the current state based on the first normalized correction factor change, and correct the scanned image based on the first normalized correction factor.

[0058] In some embodiments, at a preset time point, the variation generation module 220 may adjust the lower threshold of the energy window and then collect the first background radiation data, and the image correction module 230 may determine whether a first normalized correction factor is obtained.

[0059] In some embodiments, the preset relationship may include a functional relationship between the change in background energy response and the change in normalized correction factor under different states of the scanning system. The system 200 for correcting the scanned image may also include a functional relationship acquisition module 240, which may be used to obtain the functional relationship.

[0060] In some embodiments, the functional relationship acquisition module 240 can collect second background radiation data and second model compliance event data under a second reference system state; obtain a second reference background energy response based on the second background radiation data; obtain a second reference normalized correction factor based on the second model compliance event data; obtain multiple third background radiation data and multiple third model compliance event data collected under multiple third system states, wherein each system state in these third system states is different from the second reference system state; obtain multiple second background energy response changes based on the second reference background energy response and multiple third background radiation data; obtain multiple second normalized correction factor changes based on the second reference normalized correction factor and multiple third model compliance event data; and obtain the aforementioned functional relationship based on multiple second background energy response changes and multiple second normalized correction factor changes.

[0061] In some embodiments, for each of the plurality of third motif conforming event data, the functional relationship acquisition module 240 may obtain a second normalized correction factor based on the third motif conforming event data; and obtain a second normalized correction factor variation based on the second baseline normalized correction factor and the second normalized correction factor.

[0062] In some embodiments, the correction factor acquisition module 210, the change amount generation module 220 and the functional relationship acquisition module 240 can obtain the background energy response in the following manner: obtain a first background coincidence event and a second background coincidence event from the background radiation data, wherein the first background coincidence event corresponds to the first energy and the first crystal, and the second background coincidence event corresponds to the second energy and the second crystal; determine whether the time of the second background coincidence event is earlier than the time of the first background coincidence event; in response to yes, in the energy response of the first crystal, increment the energy box corresponding to the first energy; in response to no, in the energy response of the second crystal, increment the energy box corresponding to the second energy.

[0063] Figure 3 is an exemplary flow chart of a method for correcting a scanned image according to some embodiments of the present specification.

[0064] like Figure 3 As shown, the process 300 includes the following steps: In some embodiments, the process 300 may be executed by the processing device 120 .

[0065] Step 310 , obtaining a functional relationship between the change in background energy response and the change in normalized correction factor under different states of the scanning system. In some embodiments, step 310 may be performed by the functional relationship obtaining module 240 .

[0066] Background coincidence events, also known as background radiation events, are generated by spontaneous background radiation from the crystals in the scanning device. This means that the radiation signal received by this coincidence event is generated by background radiation. In this manual, background coincidence events are referred to as background events. Common PET systems use LSO or LYSO crystals as scintillation crystals, which contain the isotope Lu-176, which generates spontaneous background radiation. Figure 7 The diagram below shows the decay energy levels of Lu-176. Figure 7 As shown, the decay of Lu-176 includes simultaneous beta (β) decay and cascade gamma (γ) decay. The maximum energy of beta decay is 589keV, and the energy of gamma decay is 307keV, 202keV and 88keV. The simultaneity and determined energy of beta decay and gamma decay can be used to identify background events. In some embodiments, the background radiation signal of the scanning device can be collected to obtain background radiation data (i.e., background coincidence event data). In some embodiments, the background radiation energy (i.e., background gamma decay energy) can be 307keV, 202keV or 88keV, etc., and the background radiation energy is referred to as background energy in this specification. The background energy response is the energy response to the background radiation. In some embodiments, the energy response can be represented by a function, called an energy response function, for example, Figure 8 830 of them, Figure 9 The energy response functions corresponding to 930 and 940 in FIG.

[0067] In correspondence with background coincidence events, a target object can also be scanned to obtain target coincidence events for the target object. The target object, also referred to as a target scanning object, refers to the scanning object of the scanning device, such as an organism, a phantom, etc., wherein the organism can be a human body, a small animal, etc., and the phantom can be a phantom of various materials and shapes, such as a water phantom, a gel material phantom, a wooden phantom, a cylinder, a cuboid, etc. In some embodiments, the target object can be a human body and / or a water phantom. Target coincidence event data refers to coincidence events corresponding to emission energy at a specific energy level, such as coincidence events corresponding to 511keV, coincidence events corresponding to 662keV, etc. In some embodiments, the target object can be scanned by a scanning device to obtain target coincidence event data for the target object. For example, a water phantom can be scanned, and coincidence events corresponding to 511keV can be identified from all coincidence events in the water phantom to obtain phantom coincidence event data. In some embodiments, background radiation data and / or target coincidence event data can be obtained from a storage device or by other means.

[0068] By irradiating a response line or crystal with a radioactive source (e.g., one capable of producing a positron annihilation event or a pair of β-γ background events) and recording the energy distribution of all incident single events (i.e., coincident events), the energy response of the response line or crystal to the radioactive source can be obtained. For background signals, single γ- or β-decay events can be isolated using time-of-flight information. Figure 8 is a schematic diagram of energy response according to some embodiments of this specification. Figure 8 In the figure, the horizontal axis represents energy, the vertical axis represents the probability of a single event of a certain energy (for example, 307keV, 511keV), the dotted line 810 represents the lower threshold (LLD) of the energy window, the dotted line 820 represents the upper threshold (ULD) of the energy window, and the solid line 830 represents the energy response function P(E).

[0069] A scanning system refers to a system capable of acquiring medical images by scanning, and may include at least a scanning device (e.g., scanning device 110). When the system state of the scanning system changes, the energy response of the same response line or crystal to the same source may change. In some embodiments, the change in system state may include any one or more of a change in the external environment, crystal aging, SiPM gain change, and a change in the light collection performance from the crystal to the SiPM. The normalization correction factor is information used to perform normalization correction on the scanning system, and may be a fixed value or a value that changes with changes in the system state. Performing normalization correction on the scanning system is essentially performing normalization correction on the scanning data of the scanning system (e.g., background coincidence data, target object coincidence event data) using the normalization correction factor.

[0070] In some embodiments, the normalization correction factor may include at least one of an axial profile correction factor, a detector ring pair detection efficiency correction factor, a circumferential profile correction factor, a crystal detection efficiency correction factor, a time-of-flight calibration factor, and the like.

[0071] Figure 9 This is a schematic diagram illustrating changes in energy response due to changes in system state according to some embodiments of this specification. Figure 9 Can be expressed Figure 8 The energy response changes after the system state changes as shown in . Figure 9As shown, the solid line 930 represents the energy response function P(E) before the system state changes, and the dashed line 940 represents the energy response function P'(E) of the same response line or crystal to the same radiation source after the system state changes. It can be seen that after the system state changes, the area under the energy response function between the lower threshold 910 of the energy window and the upper threshold 920 of the energy window will change, that is, the number of coincidence events of the response line or crystal under the irradiation of the same intensity source will change, that is, the normalized correction factor of the response line or crystal will change. Generally, if the system state changes, the positron annihilation energy response and the background energy response will change similarly, that is, the change in the background energy response is related to the change in the normalized correction factor. In some embodiments, the processing device 120 can obtain the functional relationship between the change in the background energy response and the change in the normalized correction factor under different states of the scanning system.

[0072] In some embodiments, the system state can be changed through various methods such as passive waiting or active control. For example, as time goes by, the crystals will age and the system state will change accordingly. Some crystals can be selected to change the gain of their corresponding silicon photomultiplier (SiPM). For another example, as the external environment (e.g., temperature, humidity, etc.) changes, the system state will change. The system state can be changed by actively or passively changing environmental parameters such as temperature and humidity. For another example, the system state can be changed by actively changing parameters such as the system excitation voltage.

[0073] In some embodiments, the processing device 120 can obtain the background energy response and the normalized correction factor under different system states when the system state changes; compare the background energy response under different system states to obtain the background energy response change, and compare the normalized correction factors under different energies to obtain the normalized correction factor change. After obtaining the background energy response change and the normalized correction factor change under different system states, the processing device 120 can obtain the correlation between the two through various methods (for example, curve fitting, etc.), that is, the functional relationship between the background energy response change and the normalized correction factor change, which can be recorded as F. In some embodiments, the processing device 120 can obtain the functional relationship F through experiments and other methods. For example, based on the data of uniform water model and background radiation under different system states, the functional relationship between the change in crystal detection efficiency correction factor and the change in 307keV energy peak position can be obtained. For more information on how to obtain this functional relationship, please refer to Figure 4 The relevant description will not be repeated here.

[0074] In this specification, the normalized correction factor is described below by taking the crystal detection efficiency correction factor as an example, which is only an example and not a limitation.

[0075] In some embodiments, the processing device 120 may obtain the functional relationship F between the change in background energy response and the change in normalized correction factor through various methods (e.g., actual tests such as experiments, statistics based on historical data, etc.). F may be expressed as follows:

[0076] Δε=F[P(E),P′(E)] (1)

[0077] Where Δε is the change in the crystal detection efficiency factor; P(E) is the baseline background energy response; and P′(E) is the background energy response after the system state changes.

[0078] In some embodiments, if it is assumed that the energy responses P(E) and P′(E) conform to a Gaussian distribution, a Gaussian fitting can be performed on them, as shown in the following formula:

[0079]

[0080]

[0081] Where E is the background energy (e.g., 589 keV, 307 keV, etc.); A, μ, σ and A′, μ′, σ′ are Gaussian fitting parameters.

[0082] In some embodiments, based on formulas (1)-(3), the relationship between Δε and P(E) and P′(E) can be simplified as follows:

[0083] Δε=F[A,u,o,A′,μ′,σ′] (4)

[0084] In some embodiments, assuming that Δε=F[μ,μ′], formula (4) can be further simplified to:

[0085] Δε=F[Δu] (5)

[0086] Δu=μ′-μ (6)

[0087] In some embodiments, after obtaining the functional relationship between the change in background energy response and the change in normalized correction factor, the processing device may apply the functional relationship to the normalized correction of the clinical scan data by executing steps 320-340, thereby correcting the scanned image. In some embodiments, step 310 may be performed after step 330 and before step 350.

[0088] Step 320 , obtaining a first baseline background energy response in a first baseline system state, and obtaining a first baseline normalized correction factor based on the phantom. In some embodiments, step 320 may be performed by the correction factor acquisition module 210 .

[0089] The baseline system state refers to a system state that is used as a comparison benchmark and is compared with other system states after the system state changes. It can be the state when the system is operating normally for a long time. In some embodiments, the baseline system state may include multiple (for example, a first baseline system state, a second baseline system state, etc.), and these baseline system states may be the same or different. The first baseline state is a system state set as a benchmark for normalizing and correcting clinical scan data. In some embodiments, the first baseline state can be any selected system state. In some embodiments, the first baseline system state may include the system state after a routine normalization correction is performed.

[0090] In some embodiments, processing device 120 may obtain a background energy response under a first baseline system state, as a first baseline background energy response, denoted as P(E); and obtain a normalized correction factor by scanning a phantom, as a first baseline normalized correction factor, denoted as N0. This specification does not limit the method for obtaining the normalized correction factor based on the phantom coincidence event data.

[0091] Figure 11 FIG is a schematic diagram of a method for normalizing and correcting clinical scan data according to some embodiments of this specification. Figure 11 As shown, in some embodiments, after performing conventional normalization calibration on the scanning system, the scanning system is in a first reference system state, and the processing device 120 can collect reference background data (i.e., a first reference background energy response) and generate a reference energy response function representing the first reference background energy response (e.g., Figure 9 Collect water model data and generate a reference normalization correction factor (ie, a first reference normalization correction factor).

[0092] In some embodiments, the processing device 120 can obtain an energy response (eg, a background energy response) by counting a single coincidence event (referred to as a single event). For more information on how to obtain the background energy response, see Figure 5 The relevant description will not be repeated here.

[0093] Step 330 : Collect first background radiation data from the detector at a preset time point, and generate a first energy response variation based on the first background radiation data and the first reference background energy response. In some embodiments, step 330 may be performed by the variation generation module 220 .

[0094] In some embodiments, the processing device 120 may collect background radiation data from a detector of a scanning device at a preset time point as first background radiation data. In some embodiments, the preset time point may be periodic. For example, the period may be any one of 24 hours, 48 ​​hours, 72 hours, etc. In some embodiments, the preset time point may be determined based on the number of times the device has worked and / or the working time. For example, the device has worked 5 times, 10 times, 15 times, etc. For another example, the device has worked for 4 hours, 8 hours, 12 hours, etc. Since the system state changes over time, in some embodiments, the first background radiation data from the detector collected at the preset time point may include background radiation data after the system state has changed, wherein the system state change is relative to the first baseline system state.

[0095] In some embodiments, the processing device 120 may obtain a first background energy response after the system state changes based on the first background radiation data, which is recorded as P′(E); and generate a first energy response change ΔP(E) based on the background energy response P′(E) and the reference background energy response P(E), which can be expressed by the following formula:

[0096] AP(E)=P′(E)-P(E) (7).

[0097] like Figure 11 As shown, in some embodiments, after generating the baseline energy response function, the processing device 120 may periodically collect background data (i.e., first background radiation data). After each collection, the processing device 120 may generate an energy response function variation (i.e., first energy response variation ΔP(E)) based on the background radiation data collected this time.

[0098] In some embodiments, after generating the first energy response variation, the processing device 120 may determine whether the first energy response variation exceeds (is greater than or equal to) a preset threshold. If it does not exceed the threshold, step 340 is executed; if it exceeds the threshold, step 350 is executed. In some embodiments, the preset threshold may be an empirical value or may be obtained based on historical data, etc., which is not limited in this specification.

[0099] Step 340 : In response to the first energy response variation not being greater than a preset variation threshold, correct the scanned image based on a first reference normalization correction factor. In some embodiments, step 340 may be performed by the image correction module 230 .

[0100] In some embodiments, after each acquisition of background data, if the generated first energy response variation does not exceed a threshold, the processing device 120 may correct the scanned image based on the first baseline normalization correction factor obtained this time. Specifically, after performing a clinical scan of a target object (e.g., a patient), the processing device 120 may correct the clinical scan data collected this time (i.e., the target coincidence event data of the target object) using the first baseline normalization correction factor, and reconstruct an image based on the corrected clinical scan data to obtain a scanned image.

[0101] In step 350, in response to the first energy response change being greater than a preset change threshold, a first normalized correction factor change is generated based on the first energy response change and the functional relationship, a first normalized correction factor for the current state is generated based on the first normalized correction factor change, and the scanned image is corrected based on the first normalized correction factor. In some embodiments, step 350 may be performed by image correction module 230.

[0102] In some embodiments, after each collection of background data, if the generated first energy response change exceeds a threshold, the processing device 120 may generate a first normalized correction factor change, denoted as ΔN, based on the first energy response change ΔP(E) and a preset relationship. In some embodiments, the preset relationship may include a functional relationship F between the background energy response change and the normalized correction factor change. The first normalized correction factor change ΔN may be represented by the following formula:

[0103] ΔN=F[P(E),P′(E)] (8)

[0104] In some embodiments, after obtaining the first normalized correction factor change ΔN, the processing device 120 may correct the first baseline normalized correction factor N0 based on the first normalized correction factor change ΔN to generate a new normalized correction factor for the current state, i.e., the first normalized correction factor, denoted as N1. In some embodiments, N1 may be expressed as follows:

[0105] N=ΔN×N0 (9).

[0106] In some embodiments, the processing device 120 may adjust the energy window lower threshold (e.g., Figure 8 810 in Figure 9910 in the example); then, automatically or manually, first background radiation data is collected, the aforementioned method is executed, and a determination is made as to whether a first normalized correction factor is obtained. If the first normalized correction factor is not obtained, step 340 is executed; if the first normalized correction factor is obtained, the remaining operations of step 350 are continued. In some embodiments, by adjusting the lower threshold value of the energy window, processing device 120 can obtain more background energy responses.

[0107] In some embodiments, the processing device 120 may correct the scanned image based on the first normalized correction factor N1 obtained this time. Specifically, after performing a clinical scan on a target object (e.g., a patient), the processing device 120 may correct the clinical scan data collected this time (i.e., the target coincidence event data of the target object) using the first normalized correction factor N1, and reconstruct an image based on the corrected clinical scan data to obtain a scanned image.

[0108] like Figure 11 As shown, in some embodiments, after generating the energy response function variation, the processing device 120 may determine whether the variation exceeds a threshold. If it does not exceed the threshold, the processing device 120 may correct the clinical scan data using the baseline normalization correction factor. If it exceeds the threshold, the processing device 120 may correct the baseline normalization correction factor based on the variation to generate a normalization correction factor variation; generate a first normalization correction factor based on the normalization correction factor variation; and correct the clinical data based on the first normalization correction factor.

[0109] In some embodiments of the present specification, by obtaining the functional relationship between the change in background energy response and the change in normalized correction factor, and using it to correct the normalized correction factor under the reference state, a new normalized correction factor is generated. There is no need to recalculate the normalized correction factor under the background energy, no need to remake the water model or use a solid source, there is no radiation source, no radiation damage, easy operation, and can be performed outside of clinical scanning time (for example, non-working hours such as the middle of the night), does not occupy normal scanning working time, and greatly improves time flexibility; the generated new normalized correction factor is used to correct the clinical scanning data, thereby ensuring the accuracy of the scanning data and improving and ensuring the quality of the scanned reconstructed image.

[0110] Figure 4 is an exemplary flow chart of a method for correcting a scanned image according to some embodiments of the present specification.

[0111] like Figure 4As shown, process 400 includes the following steps. In some embodiments, process 400 can be executed by processing device 120 or functional relationship acquisition module 240. In some embodiments, processing device 120 can implement the method shown in step 310 by executing process 400 to obtain the functional relationship between the change in background energy response and the change in normalized correction factor under different states of the scanning system.

[0112] Step 410 : Collect second background radiation data and second phantom coincidence event data under a second reference system state.

[0113] In some embodiments, the processing device 120 can collect background radiation data as second background radiation data in a second reference system state, and collect phantom coincidence event data of a phantom (e.g., a water phantom) as second phantom coincidence event data. The second reference state is a system state set as a reference in order to obtain a functional relationship between the change in background energy response and the change in normalized correction factor under different states of the scanning system. In some embodiments, the second reference state can be any selected system state. In some embodiments, the second reference state can include the system state after performing a conventional normalization correction. In some embodiments, the second reference state can be the same as or different from the first reference state.

[0114] Figure 10 FIG. 1 is a schematic diagram of a method for obtaining energy responses and normalized correction factors under different system states according to some embodiments of this specification. Figure 10 As shown, in some embodiments, the processing device 120 can collect background data and water model data under a baseline system state.

[0115] Step 420: Obtain a second reference background energy response based on the second background radiation data.

[0116] In some embodiments, the processing device 120 may obtain a background energy response according to the second background radiation data as a second reference background energy response, which is recorded as P1(E).

[0117] The following description uses the normalized correction factor as the crystal detection efficiency correction factor (denoted as ε) as an example. In some embodiments, the processing device 120 can obtain the 307keV energy peak position of each crystal based on the background coincidence data (i.e., the second background radiation data) using a peak search algorithm (e.g., Gaussian fitting, etc.) in the reference system state, denoted as μ 307 , which can be used as the second reference background energy response. 307keV energy peak position μ 307 The distribution of Figure 14b In some embodiments, other energy peak positions may be used as the reference energy peak position, for example, any one of 202keV and 88keV.

[0118] For more information on how to obtain background energy response based on background radiation data, please refer to Figure 5 The relevant description will not be repeated here.

[0119] Step 430 : Obtain a second baseline normalization correction factor based on the second phantom coincidence event data.

[0120] In some embodiments, the processing device 120 may obtain a normalized correction factor based on the second phantom match event data as a second reference normalized correction factor, denoted as N2. This specification does not limit the method for obtaining the normalized correction factor based on the phantom match event data.

[0121] like Figure 10 As shown, in some embodiments, the processing device 120 can generate a baseline energy response function (i.e., a second baseline background energy response) based on the collected background data, and generate a baseline normalization correction factor (i.e., a second baseline normalization correction factor) based on the collected water model data.

[0122] Still taking the normalized correction factor as the crystal detection efficiency correction factor (denoted as ε) as an example for explanation. In some embodiments, the processing device 120 can perform normalized correction on the uniform water model under the system state as the reference to obtain the crystal detection efficiency correction factor ε, which can be used as the second reference normalized correction factor. The distribution of the crystal detection efficiency correction factor ε can be as follows Figure 14a shown.

[0123] Step 440: Acquire a plurality of third background radiation data and a plurality of third phantom coincidence event data collected in a plurality of third system states, wherein each of the third system states is different from the second reference system state.

[0124] In some embodiments, the processing device 120 may collect background radiation data and phantom coincidence event data in a third system state different from the second baseline system state after the system state changes. In some embodiments, the processing device 120 may obtain multiple third background radiation data and multiple third phantom coincidence event data collected in multiple third system states. In some embodiments, the processing device 120 may collect the third background radiation data and third phantom coincidence event data in each third system state, i.e., each time the system state changes.

[0125] In some embodiments, the third system state may be different from the system state at the preset time point in step 330 .

[0126] In some embodiments, system state changes can be implemented through various means, such as passive waiting or active control. In some embodiments, processing device 120 can change system state by actively changing crystal parameters, for example, by changing the SiPM gain corresponding to some crystals. In some embodiments, processing device 120 can change system state by changing the detector's environment, for example, by changing the set temperature of the refrigeration system to change the ambient temperature.

[0127] Step 450: Obtain a plurality of second background energy response variations based on the second reference background energy response and a plurality of third background radiation data.

[0128] In some embodiments, in each third system state, the processing device 120 can obtain the corresponding second background energy response based on the third background radiation data in the system state, denoted as P′1(E); and obtain the corresponding second background energy response change based on the second background energy response P′1(E) and the second reference background energy response P1(E), denoted as ΔP1(E). In some embodiments, the relationship between P1(E), P1′(E), and ΔP1(E) can be similar to formula (7), as shown in the following formula:

[0129] ΔP1(E)=P′1(E)-P1(E) (10)

[0130] Here, P1(E), P′1(E), and ΔP1(E) correspond to P(E), P′(E), and ΔP(E) in formula (7), respectively.

[0131] Step 460 : Obtain a plurality of second normalized correction factor variations based on the second baseline normalized correction factor and a plurality of third phantom coincidence event data.

[0132] In some embodiments, in each third system state, the processing device 120 can perform normalization correction based on the third phantom conformance event data in the system state to obtain a corresponding second normalization correction factor, denoted as N3; and obtain a corresponding second normalization correction factor change based on the second normalization correction factor N3 and the second reference normalization correction factor N2, denoted as ΔN1. In some embodiments, the relationship between N2, N3, and ΔN1 can be similar to formula (9), as shown in the following formula:

[0133] N3=ΔN1×N2 (11)

[0134] Among them, N2, N3, and ΔN1 are equivalent to N0, N1, and ΔN in formula (9), respectively.

[0135] According to formula (11), the second normalized correction factor change ΔN1 can be expressed as follows:

[0136] ΔN1=N3 / N2 (12).

[0137] like Figure 10 As shown, in some embodiments, after generating a baseline energy response function (i.e., a second baseline background energy response) and a baseline normalized correction factor (i.e., a second baseline normalized correction factor), the processing device 120 may change the system state multiple times. After each system state change, the processing device 120 may collect background data and generate an energy response function change (i.e., a second background energy response change) based on the background data; collect water model data and generate a normalized correction factor change (i.e., a second normalized correction factor change) based on the water model data; and then, the processing device 120 may determine whether a stop condition has been met. If the stop condition is met, the system state change is stopped, i.e., acquisition of the energy response function change or the normalized correction factor change is stopped. If the stop condition is not met, the next system state change is performed, and acquisition of the energy response function change or the normalized correction factor change continues. In some embodiments, the stop condition may include various forms. For example, the number of system state changes has reached a preset threshold. For another example, after obtaining the difference in the change of the energy response function or the change of the normalized correction factor in the system after sequentially adjacent changes, the stopping condition may be that the difference is less than a threshold value for multiple consecutive times (for example, ≥3 times), indicating that the scanning system has stabilized and its parameters (for example, the normalized correction factor) have changed very little.

[0138] The normalized correction factor is still taken as the crystal detection efficiency correction factor (denoted as ε) as an example for explanation.

[0139] In some embodiments, the crystal detection efficiency correction factor ε and the 307keV energy peak position μ under the reference system state are obtained. 307 Afterwards, the processing device 120 may change the system state. The processing device 120 may perform normalization correction on the uniform water model again under the new system state to obtain the crystal detection efficiency correction factor ε′, which may be used as the second normalization correction factor. The distribution of the crystal detection efficiency correction factor ε′ may be as follows: Figure 15a The processing device 120 can collect background coincidence data (i.e., the third background radiation data) again in the new system state, and use a peak search algorithm (e.g., Gaussian fitting, etc.) to obtain the 307keV energy peak position of each crystal, which is recorded as μ′. 307 , which can be used as the second background energy response. 307keV energy peak position μ′ 307 The distribution of Figure 15b shown.

[0140] In some embodiments, after obtaining the crystal detection efficiency correction factor ε′ and the 307keV energy peak position μ′ 307Afterwards, the processing device 120 can obtain the crystal detection efficiency correction factor change Δε based on the crystal detection efficiency correction factors ε and ε′ obtained above according to formula (12), where Δε=ε′ / ε. The distribution of the crystal detection efficiency correction factor change Δε can be as follows: Figure 16a The processing device 120 can calculate the energy peak position μ of 307keV based on the above-mentioned energy peak position μ. 307 and μ′ 307 According to formula (10), the change in the 307keV energy peak position Δμ is obtained 307 , where Δμ 307 =μ′ 307 -μ 307 307keV energy peak position change Δμ 307 The distribution can be entered Figure 16b shown.

[0141] Step 470: Obtain a functional relationship based on the multiple background energy response changes and the multiple normalized correction factor changes.

[0142] In some embodiments, the processing device 120 may obtain a functional relationship F between the background energy response variation and the normalized correction factor variation by curve fitting or other methods, based on the obtained multiple second background energy response variation ΔP1(E) and the multiple second normalized correction factor variation ΔN1. In some embodiments, similar to formula (1), based on formula (10), the functional relationship F may be as follows:

[0143] ΔN1=F[P1(E),P′1(E)] (13)

[0144] Here, ΔN1, P1(E), and P′1(E) correspond to Δε, P(E), and P′(E) in formula (1), respectively.

[0145] Still taking the normalized correction factor as the crystal detection efficiency correction factor (denoted as ε) as an example for explanation. In some embodiments, after obtaining multiple crystal detection efficiency correction factor changes Δε and multiple 307keV energy peak position changes Δμ 307 Afterwards, the processing device 120 can use these crystal detection efficiency correction factor changes Δε and 307keV energy peak position changes Δμ to calculate the value of the correction factor. 307 , and curve fitting is performed to obtain the functional relationship F shown in formula (1). The curve fitting results of the change in the crystal detection efficiency correction factor and the change in the 307keV energy peak position can be shown as Figure 17 shown.

[0146] In some embodiments, for other normalized correction factors other than the crystal detection efficiency correction factor (for example, any one or more of the axial profile correction factor, the detector ring pair detection efficiency correction factor, the circumferential profile correction factor, and the time of flight calibration factor), the functional relationship F between the change in the normalized correction factor and the change in the energy response can be obtained using a method similar to that of the crystal detection efficiency correction factor.

[0147] In some embodiments, the processing device 120 may obtain the functional relationship F between the normalized correction factor change and the energy response change by other means, such as a machine learning model. In some embodiments, the processing device 120 may input background radiation data and normalized correction factors (or multiple background energy response changes and multiple normalized correction factor changes) acquired under different system states into the machine learning model to obtain the output functional relationship F, for example, Figure 17 The diagram shows the relationship between the change in the crystal detection efficiency correction factor and the change in the 307keV energy peak position.

[0148] In some embodiments of this specification, by statistically analyzing the change in background energy response and the change in normalized correction factor under different system states and applying curve fitting and other methods, a functional relationship between the change in normalized correction factor and the change in energy response is obtained. This functional relationship can then be used to accurately determine the normalized correction factor for the current system state based on the change in energy response. This improves the accuracy of the normalized correction factor, overcomes the problem of the mismatch between the normalized correction factor and the system state increasing over time, and thereby improves the quality of clinical scan images.

[0149] Figure 5 is an exemplary flow chart of a method for correcting a scanned image according to some embodiments of the present specification.

[0150] like Figure 5 As shown, process 500 includes the following steps. In some embodiments, process 500 can be executed by processing device 120 or a module in system 200 for correcting scanned images (e.g., any one or more of correction factor acquisition module 210, variation generation module 220, and functional relationship acquisition module 240). In some embodiments, processing device 120 can obtain a background energy response based on background radiation data (i.e., background coincidence data) by executing process 500.

[0151] Background radiation is usually weak and difficult to detect. Since gamma decay has a specific energy, in some embodiments, gamma decay can be used for background coincidence events, that is, the reception of gamma decay is regarded as a single event. In some embodiments, in order to improve the statistical quality of background coincidence events, a cone beam with a certain crystal as the top can be used to count the background coincidence events within the cone beam range, and the energy information of all coincidence events with the crystal as one end can be accumulated to obtain the energy response of the crystal. Figure 13 As shown, 1310 and 1320 are different crystals, 1330 is the location where Lu-176 decays, the upward arrow 1340 represents beta decay, the downward arrow 1350 represents gamma decay, and the two dotted lines 1360 and 1370 represent the boundaries of the cone beam. As can be seen from the figure, compared with beta decay, the flight path of gamma decay is longer, which makes its flight time longer, so its single event arrives later. In some embodiments, the processing device 120 can judge the energy of a single event based on the order of arrival time, that is, determine the single event with a later arrival time as gamma decay. Figure 13 As shown, the processing device 120 can accumulate energy information of all events corresponding to the crystal 1310 to obtain the energy response of the crystal 1310.

[0152] Step 510: Acquire a first background coincidence event and a second background coincidence event from background radiation data, wherein the first background coincidence event corresponds to a first energy and a first crystal, and the second background coincidence event corresponds to a second energy and a second crystal.

[0153] In some embodiments, the processing device 120 can obtain a first background coincidence event and a second background coincidence event from the acquired background radiation data (e.g., first background radiation data, second background radiation data, and third background radiation data). The first background coincidence event corresponds to a first energy and a first crystal, and the second background coincidence event corresponds to a second energy and a second crystal. In some embodiments, the first energy and the second energy correspond to different energy decays. For example, the first energy may be gamma decay, and the second energy may be beta decay. For another example, the first energy may be beta decay, and the second energy may be gamma decay.

[0154] Figure 12 Schematic diagram of a method for obtaining background energy response according to some embodiments of this specification. Figure 12 As shown, the processing device 120 can obtain single event A (i.e., the first background coincident event) and single event B (i.e., the second background coincident event) from background coincident event AB. Single event A has energy EA, time TA, and crystal number i; single event B has energy EB, time TB, and crystal number j.

[0155] Step 520: Determine whether the time of the second background coincidence event is earlier than the time of the first background coincidence event.

[0156] In some embodiments, the processing device 120 may determine whether the time of the second background coincidence event is earlier than the time of the first background coincidence event. If the time of the second background coincidence event is earlier than the time of the first background coincidence event, step 530 is executed, otherwise step 540 is executed. For example, if Figure 12 As shown, the processing device 120 can determine whether TA is greater than TB and perform different operations according to the determination result.

[0157] Step 530 , in response to the energy response of the first crystal, increment the energy bin corresponding to the first energy.

[0158] An energy bin is an energy range used to determine an energy response and can be determined based on the energy level of decay (e.g., beta decay, gamma decay, etc.). For example, the energy bin can be a range centered around any one of 589 keV, 307 keV, 202 keV, and 88 keV. In some embodiments, the energy range of the energy bin can be smaller than the energy range of the energy window.

[0159] In some embodiments, if the time of the second background coincidence event precedes the time of the first background coincidence event, the processing device 120 may increment the energy bin corresponding to the first energy in the energy response of the first crystal. In some embodiments, if the time of the second background coincidence event precedes the time of the first background coincidence event, it may be determined that the first energy is a gamma decay event, i.e., the first crystal received a gamma decay event, and the processing device 120 may increment the energy bin corresponding to the first energy of the first crystal by 1.

[0160] Just as an example, Figure 12 As shown, if TA>TB, that is, the time of the second background coincidence event is earlier than the time of the first background coincidence event, the processing device 120 can determine that EA is a gamma decay and add 1 to the EAth energy bin of the energy response of crystal i.

[0161] Step 540 , in response to no, increment the energy bin corresponding to the second energy in the energy response of the second crystal.

[0162] In some embodiments, if the time of the second background coincidence event does not precede the time of the first background coincidence event, the processing device 120 may increment the energy bin corresponding to the second energy in the energy response of the second crystal. In some embodiments, if the time of the second background coincidence event does not precede the time of the first background coincidence event, it can be determined that the second energy is a gamma decay event, i.e., the second crystal received a gamma decay event, and the processing device 120 may increment the energy bin corresponding to the second energy of the second crystal by 1.

[0163] Just as an example, Figure 12 As shown, if TA≤TB, that is, the time of the second background coincidence event does not precede the time of the first background coincidence event, the processing device 120 can determine that EB is a gamma decay and add 1 to the EBth energy bin of the energy response of crystal j.

[0164] In some embodiments of the present specification, background coincidence events are determined by counting gamma decays based on the time sequence of a single event, thereby improving the statistical accuracy of background coincidence events; and the statistical quality of background coincidence events is improved by taking radiation data within a cone beam with a crystal as the top.

[0165] It should be noted that the above descriptions of processes 300, 400, and 500 are intended for illustration and purpose only and do not limit the scope of this specification. Those skilled in the art will be able to make various modifications and alterations to processes 300, 400, and 500 under the guidance of this specification. However, such modifications and alterations remain within the scope of this specification. For example, steps 420 and 430 may be performed simultaneously or sequentially.

[0166] The beneficial effects that may be brought about by the embodiments of this specification include but are not limited to: (1) by obtaining the functional relationship between the background energy response change and the normalized correction factor change, and using it to correct the normalized correction factor under the reference state, a new normalized correction factor is generated. There is no need to recalculate the normalized correction factor under the background energy, no need to remake the water model or use a solid source, no radioactive source, no radiation damage, and simple operation; it can be performed outside the clinical scanning time (for example, non-working hours such as midnight), does not occupy the normal scanning working time, and greatly improves time flexibility. By using the generated new normalized correction factor to correct the clinical scanning data, the accuracy of the scanning data is guaranteed, and the quality of the scanned reconstructed image is improved and guaranteed; (2) by statistically calculating the background energy response change and the normalized correction factor change under different system states, and using curve fitting and other means, the functional relationship between the normalized correction factor change and the energy response change is obtained. Therefore, this functional relationship can be used to accurately determine the normalized correction factor under the current system state according to the change in energy response. The accuracy of the normalized correction factor is improved, overcoming the problem of the mismatch between the normalized correction factor and the system status gradually increasing over time, thereby improving the quality of clinical scan images. It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects that may be produced may be any one or a combination of the above, or any other possible beneficial effects.

[0167] While the basic concepts have been described above, it will be apparent to those skilled in the art that the detailed disclosure is merely illustrative and does not limit this specification. Although not explicitly stated herein, various modifications, improvements, and revisions to this specification may be made by those skilled in the art. Such modifications, improvements, and revisions are suggested in this specification and remain within the spirit and scope of the exemplary embodiments of this specification.

[0168] This specification also uses specific terms to describe the embodiments of this specification. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "one embodiment," "an embodiment," or "an alternative embodiment" two or more times in different locations in this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of this specification may be appropriately combined.

[0169] In addition, unless expressly stated in the claims, the order of the processing elements and sequences, the use of alphanumeric characters, or the use of other names described in this specification are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some of the invention embodiments currently considered useful through various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the spirit and scope of the embodiments of this specification. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only by software solutions, such as installing the described system on an existing server or mobile device.

[0170] Similarly, it should be noted that, in order to simplify the presentation of this specification and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this specification sometimes combine multiple features into a single embodiment, figure, or description thereof. However, this disclosure method does not imply that the subject matter of this specification requires more features than those recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single disclosed embodiment.

[0171] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required characteristics of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of this specification are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0172] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, and documents, cited in this specification is hereby incorporated by reference in its entirety. This includes application history documents that are inconsistent with or conflict with the content of this specification, as well as documents (currently or subsequently attached to this specification) that limit the broadest scope of the claims of this specification. It should be noted that if the descriptions, definitions, and / or terminology used in the accompanying materials are inconsistent or conflicting with the content of this specification, the descriptions, definitions, and / or terminology used in this specification will control.

[0173] Finally, it should be understood that the embodiments described in this specification are intended only to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly described and illustrated in this specification.

Claims

1. A method for correcting a scanned image, comprising: Acquire a first reference background energy response in a first reference system state, and acquire a first reference normalization correction factor based on the phantom; Collecting first background radiation data of the detector at a preset time point, and generating a first energy response variation based on the first background radiation data and the first reference background energy response; In response to the first energy response variation being no greater than a preset variation threshold, correcting the scanned image based on the first reference normalization correction factor; In response to the first energy response change being greater than the preset change threshold, a first normalized correction factor change is generated based on the first energy response change and a preset relationship, a first normalized correction factor of the current state is generated based on the first normalized correction factor change, and the scanned image is corrected based on the first normalized correction factor.

2. The method of claim 1 , wherein the preset relationship comprises a functional relationship between a change in background energy response and a change in a normalized correction factor under different states of the scanning system, wherein the functional relationship is obtained by: collecting second background radiation data and second phantom coincidence event data in a second reference system state; obtaining a second reference background energy response based on the second background radiation data; obtaining a second baseline normalization correction factor based on the second phantom coincidence event data; Acquiring a plurality of third background radiation data and a plurality of third phantom coincidence event data collected under a plurality of third system states, each of the plurality of third system states being different from the second reference system state; Obtaining a plurality of second background energy response variations based on the second reference background energy response and the plurality of third background radiation data; Obtaining a plurality of second normalized correction factor variations based on the second reference normalized correction factor and the plurality of third phantom coincidence event data; The functional relationship is obtained based on the multiple second background energy response changes and the multiple second normalized correction factor changes.

3. The method of claim 2, wherein obtaining a plurality of second normalized correction factor variations based on the second baseline normalized correction factor and the plurality of third phantom coincidence event data comprises: For each of the plurality of third motif-matching event data, obtaining a second normalization correction factor based on the third motif coincident event data; The second normalized correction factor variation is obtained based on the second reference normalized correction factor and the second normalized correction factor.

4. The method of claim 1, wherein the normalized correction factor comprises at least one of an axial profile correction factor, a detector ring pair detection efficiency correction factor, a circumferential profile correction factor, a crystal detection efficiency correction factor, and a time-of-flight calibration factor.

5. The method of claim 1, comprising: At the preset time point, after adjusting the lower threshold of the energy window, the first background radiation data is collected and it is determined whether the first normalized correction factor is obtained.

6. The method according to claim 1, wherein obtaining the background energy response comprises: Acquire a first background coincidence event and a second background coincidence event from the background radiation data, wherein the first background coincidence event corresponds to a first energy and a first crystal, and the second background coincidence event corresponds to a second energy and a second crystal; Determining whether the time of the second background coincidence event is earlier than the time of the first background coincidence event; In response to this, in the energy response of the first crystal, the energy bin corresponding to the first energy is incremented; In response to no, the energy bin corresponding to the second energy is incremented in the energy response of the second crystal.

7. A system for correcting a scanned image, comprising a correction factor acquisition module, a variation generation module, and an image correction module; The correction factor acquisition module is used to obtain a first reference background energy response in a first reference system state and obtain a first reference normalized correction factor based on the phantom; The variation generating module is configured to collect first background radiation data of the detector at a preset time point, and generate a first energy response variation based on the first background radiation data and the first reference background energy response; The image correction module is used to: In response to the first energy response variation being no greater than a preset variation threshold, correcting the scanned image based on the first reference normalization correction factor; In response to the first energy response change being greater than the preset change threshold, a first normalized correction factor change is generated based on the first energy response change and a preset relationship, a first normalized correction factor of the current state is generated based on the first normalized correction factor change, and the scanned image is corrected based on the first normalized correction factor.

8. The system of claim 7 , wherein the preset relationship comprises a functional relationship between a change in background energy response and a change in a normalized correction factor under different states of the scanning system, and the system further comprises a functional relationship acquisition module, wherein the functional relationship acquisition module is configured to: collecting second background radiation data and second phantom coincidence event data in a second reference system state; obtaining a second reference background energy response based on the second background radiation data; obtaining a second baseline normalization correction factor based on the second phantom coincidence event data; Acquiring a plurality of third background radiation data and a plurality of third phantom coincidence event data collected under a plurality of third system states, each of the plurality of third system states being different from the second reference system state; Obtaining a plurality of second background energy response variations based on the second reference background energy response and the plurality of third background radiation data; Obtaining a plurality of second normalized correction factor variations based on the second reference normalized correction factor and the plurality of third phantom coincidence event data; The functional relationship is obtained based on the multiple second background energy response changes and the multiple second normalized correction factor changes.

9. A device for correcting a scanned image, comprising a processor, wherein the processor is configured to execute the method according to any one of claims 1 to 6.

10. A computer-readable storage medium, wherein the storage medium stores computer instructions, and when a computer reads the computer instructions in the storage medium, the computer executes the method according to any one of claims 1 to 6.

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