PET (positron emission tomography) system and correction method, system, equipment and medium thereof

Abstract

The invention provides a PET (positron emission tomography) system and a correction method, system and device thereof, and a medium. The correction method comprises the following steps: acquiring an initial normalization correction factor of an initial response line corresponding to a target detector crystal group in the PET system; determining a target response line corresponding to the target detector crystal group based on the interaction depth interlayer information; obtaining a normalization factor correction coefficient of the target response line relative to the initial response line; and based on the initial normalization correction factor and the normalization factor correction coefficient, obtaining a target normalization correction factor corresponding to the target response line so as to correct the PET system. The target normalization correction factor corresponding to the target LOR related to the DOI is obtained on the basis of the initial LOR irrelevant to the DOI, normalization correction of the PET system is achieved, and under the condition that correction complexity and statistics are not increased, the accuracy of image reconstruction of the PET system with DOI interlayer information and the maintainability of the PET system are improved.

Description

Technical Field

[0001] The present disclosure relates to the field of PET (Positron Emission Tomography) technology, and in particular to a PET system and a correction method, system, device and medium thereof. Background Art

[0002] PET is a high-end nuclear medicine imaging diagnostic equipment. In actual operation, radioactive nuclides are used to label metabolites. This labeled metabolic drug will emit positrons through decay emission, which annihilates with surrounding electrons to produce a pair of photons with opposite emission directions. If two photons are detected by the detector crystal of the PET detection system at the same time, the nuclide is considered to be on the line connecting the pair of detectors (a group of detectors) that capture the photons accordingly, which is called the line of response (LOR). The collection of all response lines for each inspection constitutes the raw data of PET, which is called list-mode data. When using PET for large-scale imaging, a mobile scanning mode is usually used. The moving position of the bed is usually transmitted to the PET detection system in real time and stored in the list-mode data. Through a series of physical corrections to the list-mode data, a three-dimensional image is finally generated by the reconstruction algorithm to perform functional metabolic imaging and reflect the situation of life metabolic activities.

[0003] Since the depth at which annihilation photons interact with the detector crystals is arbitrary and even intercrystalline penetration may occur, there is a serious radial depth of interaction (DOI) effect or radial parallax in a certain lateral field of view of the PET system, which causes the resolution of the reconstructed image to be uneven at different radial positions. In particular, when the object is close to the edge of the field of view, the resolution will be significantly reduced, resulting in a serious "tailing" effect.

[0004] The commonly used normalization correction schemes for PET systems are direct normalization or component normalization. Direct normalization is generally used in 2D (two-dimensional) PET systems with fewer LORs. For the current mainstream 3D (three-dimensional) PET systems, it is generally not implemented because the required statistics are too large.

[0005] Component normalization is a method that decomposes LOR-level normalization into multiple components of smaller dimensions, thereby reducing the complexity of correction and the required statistics. For example, the correction method using a moving phantom is used for long-axis systems. However, these methods currently do not involve PET systems with DOI information.

[0006] DOI information specifically refers to the depth information of gamma rays deposited in the PET detector, which helps to improve the spatial resolution of the PET system. However, since the detector with DOI information is divided from the original single crystal structure into multiple crystal layers of different depths, the LOR of the PET system is greatly increased. Assuming that the PET system has 8 layers of DOI, the number of LORs is 8 times that of the PET system without DOI. 2 The large increase in LOR also greatly increases the difficulty of normalization correction.

[0007] Assuming that the number of DOI division layers is not large, we can consider continuing to use the traditional component normalization method and only regard the detector as having doubled the number of crystals. However, for DOI detectors with many layers, this method cannot be continued or is extremely difficult to use because the required statistics are too large. Summary of the invention

[0008] The technical problem to be solved by the present disclosure is to overcome the defect in the prior art that a detector with DOI information is not normalized and corrected, and to provide a PET system and a correction method, system, device and medium thereof.

[0009] The present invention solves the above technical problems through the following technical solutions:

[0010] The positive and progressive effects of this disclosure are:

[0011] In a first aspect, a correction method for a PET system is provided, which is applied to a PET system including interaction depth interlayer information, and the correction method comprises:

[0012] Obtaining an initial normalized correction factor for an initial response line corresponding to a target detector crystal group in the PET system;

[0013] Wherein, the initial response line is independent of the interaction depth interlayer information;

[0014] Determining a target response line corresponding to the target detector crystal group based on the interaction depth interlayer information;

[0015] Obtaining a normalization factor correction coefficient of the target response line relative to the initial response line;

[0016] Based on the initial normalization correction factor and the normalization factor correction coefficient, a target normalization correction factor corresponding to the target response line is obtained to calibrate the PET system.

[0017] Preferably, the step of obtaining the initial normalized correction factor of the initial response line corresponding to the target detector crystal group in the PET system includes:

[0018] Based on a preset normalization correction method, obtaining the initial normalization correction factor of the initial response line corresponding to the target detector crystal group in the PET system;

[0019] Wherein, the preset normalization correction method includes a direct normalization correction method and / or a component normalization correction method.

[0020] Preferably, the step of obtaining the target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient to calibrate the PET system includes:

[0021] The product value of the initial normalization correction factor and the normalization factor correction coefficient is calculated, and the product value is used as the target normalization correction factor to calibrate the PET system.

[0022] Preferably, the step of obtaining a normalization factor correction coefficient of the target response line relative to the initial response line comprises:

[0023] Obtaining a total count of initial response lines corresponding to the target detector crystal group that are independent of the interaction depth interlayer information;

[0024] Obtaining a total count of target response lines corresponding to the target detector crystal group and related to the interaction depth interlayer information;

[0025] The normalization factor correction coefficient of the target response line relative to the initial response line is obtained based on the total count of the initial response line and the total count of the target response line.

[0026] Preferably, the step of obtaining the normalization factor correction coefficient of the target response line relative to the initial response line based on the total count of the initial response line and the total count of the target response line comprises:

[0027] The ratio of the total count of the initial response line to the total count of the target response line is calculated, and the ratio is used as the normalization factor correction coefficient.

[0028] Preferably, the correction method further comprises:

[0029] Obtaining the spatial position corresponding to each of the target response lines;

[0030] Merging a plurality of target response lines within the same preset spatial position range into a same virtual reconstruction response line;

[0031] Based on the target normalized correction factors respectively corresponding to the plurality of target response lines, obtaining a reconstruction normalized correction factor corresponding to the virtual reconstruction response line;

[0032] calibrating the PET system based on the reconstruction normalization correction factor;

[0033] And / or, the step of obtaining the target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient to calibrate the PET system includes:

[0034] Based on the initial normalization correction factor and the normalization factor correction coefficient, acquiring the target normalization correction factor corresponding to the target response line;

[0035] A PET image is reconstructed based on the target normalized correction factor to calibrate the PET system.

[0036] In a second aspect, a correction system for a PET system is also provided, which is applied to a PET system including interaction depth interlayer information, and the correction system comprises:

[0037] A first data acquisition module is used to acquire an initial normalized correction factor of an initial response line corresponding to a target detector crystal group in the PET system;

[0038] Wherein, the initial response line is independent of the interaction depth interlayer information;

[0039] A second data acquisition module, configured to determine a target response line corresponding to the target detector crystal group based on the interaction depth interlayer information;

[0040] A third data acquisition module, used to acquire a normalization factor correction coefficient of the target response line relative to the initial response line;

[0041] A data processing module is used to obtain a target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient, so as to calibrate the PET system.

[0042] Preferably, the first data acquisition module is further used to acquire the initial normalization correction factor of the initial response line corresponding to the target detector crystal group in the PET system based on a preset normalization correction method;

[0043] Wherein, the preset normalization correction method includes a direct normalization correction method and / or a component normalization correction method.

[0044] Preferably, the data processing module is further used to calculate the product value of the initial normalization correction factor and the normalization factor correction coefficient, and use the product value as the target normalization correction factor to calibrate the PET system.

[0045] Preferably, the third data acquisition module includes:

[0046] An initial total count acquisition unit, used to acquire the total count of initial response lines corresponding to the target detector crystal group and independent of the interaction depth interlayer information;

[0047] A target total count acquisition unit, used to acquire a total count of target response lines corresponding to the target detector crystal group and related to the interaction depth interlayer information;

[0048] A correction coefficient acquisition unit is used to acquire the normalization factor correction coefficient of the target response line relative to the initial response line based on the total count of the initial response line and the total count of the target response line.

[0049] Preferably, the correction coefficient acquisition unit is further used to calculate the ratio of the total count of the initial response line to the total count of the target response line, and use the ratio as the normalization factor correction coefficient.

[0050] Preferably, the correction system comprises:

[0051] A position acquisition module, used to acquire the spatial position corresponding to each of the target response lines;

[0052] A merging module, used to merge a plurality of target response lines within the same preset spatial position range into a same virtual reconstruction response line;

[0053] A reconstruction factor acquisition module, used for acquiring a reconstruction normalization correction factor corresponding to the virtual reconstruction response line based on the target normalization correction factors respectively corresponding to a plurality of the target response lines;

[0054] a correction module, configured to calibrate the PET system based on the reconstructed normalized correction factor;

[0055] And / or, the data processing module includes:

[0056] A target factor acquisition unit, configured to acquire the target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient;

[0057] An image reconstruction unit performs PET image reconstruction based on the target normalized correction factor to calibrate the PET system.

[0058] In a third aspect, a PET system is also provided, comprising the correction system of the above-mentioned PET system.

[0059] In a fourth aspect, an electronic device is also provided, comprising a memory, a processor, and a computer program stored in the memory and used to run on the processor, wherein the processor implements the above-mentioned PET system correction method when executing the computer program.

[0060] In a fifth aspect, a computer-readable storage medium is also provided, on which a computer program is stored, and when the computer program is executed by a processor, the correction method of the PET system described above is implemented.

[0061] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0062] The PET system and its correction method, system, device and medium disclosed in the present invention are based on the traditional initial normalized correction factor of the initial response line (LOR) that is independent of the interaction depth (DOI) interlayer information, and introduces a normalization factor correction coefficient of the target response line related to the interaction depth interlayer information relative to the initial response line. The target normalized correction factor corresponding to the target response line is obtained through the initial normalized correction factor and the normalization factor correction coefficient, thereby realizing normalized correction of the PET system. Without increasing the complexity and statistics of the correction, the accuracy of the detector reconstructed image of the PET system including the DOI interlayer information is improved, and the maintainability of the PET system is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A first flow chart of the calibration method for the PET system provided in Example 1 of the present disclosure;

[0064] Figure 2 A second flow chart of the calibration method for the PET system provided in Embodiment 1 of the present disclosure;

[0065] Figure 3 A third flow chart of the calibration method for the PET system provided in Embodiment 1 of the present disclosure;

[0066] Figure 4 A schematic diagram of the target LOR in the calibration method of the PET system provided in Example 1 of the present disclosure;

[0067] Figure 5 A fourth flow chart of the calibration method for the PET system provided in Embodiment 1 of the present disclosure;

[0068] Figure 6 A fifth flow chart of the calibration method for the PET system provided in Embodiment 1 of the present disclosure;

[0069] Figure 7 A sixth flow chart of the calibration method for the PET system provided in Embodiment 1 of the present disclosure;

[0070] Figure 8 A seventh flow chart of the calibration method for the PET system provided in Embodiment 1 of the present disclosure;

[0071] Fig. 9 A schematic diagram of a reconstructed image of the correction method for the PET system provided in Example 1 of the present disclosure;

[0072] Fig.10 A schematic diagram of the structure of a correction system for a PET system provided in Example 2 of the present disclosure;

[0073] Fig.11 A schematic diagram of the structure of an electronic device provided in Embodiment 4 of the present disclosure. DETAILED DESCRIPTION

[0074] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.

[0075] Example 1

[0076] This embodiment provides a correction method for a PET system, which is applied to a PET system including interaction depth inter-layer information, such as Figure 1 As shown, the correction method includes:

[0077] S101, obtaining an initial normalized correction factor of an initial response line corresponding to a target detector crystal group in a PET system.

[0078] Among them, the initial response line has nothing to do with the interaction depth interlayer information.

[0079] S102. Determine a target response line corresponding to the target detector crystal group based on the interaction depth interlayer information.

[0080] S103, obtaining a normalization factor correction coefficient of the target response line relative to the initial response line.

[0081] S104. Based on the initial normalization correction factor and the normalization factor correction coefficient, a target normalization correction factor corresponding to the target response line is obtained to calibrate the PET system.

[0082] For a PET system with a certain number of rings, each ring has a certain number of detector crystals, and a coincidence event corresponds to two detector crystals. The two detector crystals corresponding to a coincidence event are the target detector crystal group in the present disclosure, and may also be referred to as a target detector crystal pair.

[0083] The initial response lines corresponding to the target detector crystal group in the PET system are response lines without DOI interlayer information, and the target response lines corresponding to the target detector crystal group are response lines with DOI interlayer information.

[0084] For a PET system that includes DOI interlayer information, its detector crystal has certain DOI interlayer information, that is, the crystal has a certain number of layers. Based on the DOI interlayer information, it is not only known in which target detector crystal group the coincidence event occurred, but also in which layer of the crystal the coincidence event occurred, that is, the depth information. For example, assuming that the detector crystal has 8 layers, a coincidence event occurs in the 5th layer of one crystal and the 6th layer of another crystal, corresponding to a depth of 1 cm and 1.5 cm from the crystal surface, respectively. Based on the DOI interlayer information, the direction from which the gamma ray was emitted can be known more accurately, and the response line of the coincidence event will be more accurate, thereby improving the resolution of the reconstructed image.

[0085] The correction method of the PET system in this embodiment is based on the traditional initial normalization correction factor of the initial LOR that is independent of the DOI interlayer information, and introduces a normalization factor correction coefficient of the target LOR related to the DOI interlayer information relative to the initial LOR. The target normalization correction factor corresponding to the target LOR is obtained through the initial normalization correction factor and the normalization factor correction coefficient, thereby realizing normalization correction of the PET system. Without increasing the complexity and statistics of the correction, the accuracy of the detector reconstructed image of the PET system with DOI interlayer information is improved, and the maintainability of the PET system is greatly improved.

[0086] In an optional embodiment, if Figure 2 As shown, the above step S101 includes:

[0087] S1011. Based on a preset normalization correction method, an initial normalization correction factor of an initial response line corresponding to a target detector crystal group in a PET system is obtained.

[0088] Among them, the preset normalization correction method includes a direct normalization correction method and / or a component normalization correction method.

[0089] The initial response line corresponding to the target detector crystal group in the PET system, that is, the response line without DOI interlayer information, and the initial normalized correction factor corresponding to the initial response line are independent of the DOI interlayer information. How to obtain the initial normalized correction factor of the initial response line is a prior art and will not be repeated here.

[0090] In an optional embodiment, if Figure 3 As shown, the above step S104 includes:

[0091] S1041. Calculate the product value of the initial normalization correction factor and the normalization factor correction coefficient, and use the product value as the target normalization correction factor to calibrate the PET system.

[0092] For example, the initial normalization correction factor is represented by Nc, the normalization factor correction coefficient is represented by D, and the target normalization correction factor is represented by Nm. The target normalization correction factor is the product of the initial normalization correction factor and the normalization factor correction coefficient, that is, Nm=Nc*D.

[0093] A specific example is given below to further illustrate this implementation.

[0094] Specifically, for a traditional cylindrical PET system with a specific number of rings, the initial normalized correction factor of the initial LOR for the coincident event of the i-th crystal a in the u-th ring and the j-th crystal b in the v-th ring is Nc=N(ui,vj), wherein u, i, v and j are all integers, the value range of u and v is the number of crystal rings, and the value range of i and j is the number of crystals in a single ring, that is, ui corresponds to crystal a, vj corresponds to crystal b, crystal a and crystal b constitute a target detector crystal group, and the photon incident point of crystal a and the photon incident point of crystal a connected together are equivalent to an initial LOR, and the initial normalized correction factor of the initial LOR is Nc=N(ui,vj).

[0095] If the interaction depth interlayer information corresponds to the mth layer in crystal a and the nth layer in crystal b, it can be known that the target response line occurs in the mth layer in crystal a and the nth layer in crystal b. The target normalization correction factor corresponding to the target response line is Nm=N(uim,vjn), where m and n are positive numbers, and the value range is the number of DOI layers in the PET system, that is, uim corresponds to the mth layer of crystal a, vjn corresponds to the nth layer of crystal b, and the photon incident point of the mth layer of crystal a and the photon incident point of the nth layer of crystal b are connected to form a target LOR. The target LOR is a more accurate LOR relative to the initial LOR. The target normalization correction factor of the target LOR is Nm=N(uim,vjn).

[0096] The normalization factor correction coefficient of the target response line relative to the initial response line is D=D(m,n,rdif,r,k).

[0097] Then N(uim,vjn)=N(ui,vj)*D(m,n,rdif,r,k);

[0098] Among them, the parameters that determine D in D(m,n,rdif,r,k) include the crystal ring difference rdif=|uv|, the target LOR ring direction number r(irad), and the target LOR ring direction angle number k(iphi) in addition to the DOI layer number m and n. Among them, each parameter in the normalization factor correction coefficient D(m,n,rdif,r,k) can be obtained from the sinusoidal data corresponding to the target LOR, and can be obtained by looking up the table.

[0099] In the same PET system, the total number of crystal layers (i.e., the number of DOI layers) corresponding to the detector crystals of different rings is the same. For example, the total number of crystal layers can be expressed as n DOI Definition of .

[0100] After the gamma ray enters the crystal, the probability of deposition between crystals with different DOIs is determined by the incident direction of the gamma ray, the thickness of the DOI layer, and the stopping power of other crystals before the ray enters the DOI layer. Therefore, the determination of D(m,n,rdif,r,k) is related to the relative direction of the target LOR and the crystal. (m,n,rdif,r,k) is the parameter that determines the relative crystal direction of the target LOR that matches the event.

[0101] In this embodiment, the complexity of the correction coefficient D can be simplified by considering the rotational and translational symmetries of the PET system.

[0102] For example, for different target LORs with circumferential rotational symmetry, the same coefficient can be shared, i.e., k = where i phi It refers to the target LOR circumferential angle number without considering rotational symmetry. is the number of symmetric angles of the target LOR. Assuming that a ring of a PET detector has 1000 detector crystals, 500 angles are generally defined in the range of 0-180 degrees when defining the angle, that is, there are 500 different angles in the range of 0-180 degrees. For different target LORs with annular rotational symmetry, the same coefficient can be used. Therefore, the input parameter selects the angle coefficient k. Assuming that the detector crystal ring is a 50-hedron with 20 detectors on each face, the 0th angle and the 20th angle are rotationally symmetric. In this case, you only need to generate coefficients k of 0-19, and the others can be directly searched through rotational symmetry. When symmetry is not considered, i phi is 0-499, taking into account the symmetry, i phi It is 0-19, and the optional dimension of k is changed from 0-499 to 00-19, which simplifies the amount of data in the lookup table.

[0103] For LORs that are symmetric in axial translation, the same coefficient rdif can be shared. That is, the target LORs of the coincident events of the 0th and 1st axial rings are symmetric with the target LORs of the coincident events of the 1st and 2nd axial rings, and they can share the same coefficient. Therefore, the input parameter selects the ring difference rdif.

[0104] In the present disclosure, the parameter dimension of the normalization factor correction coefficient D(m,n,rdif,r,k) of the target response line relative to the initial response line is only exemplary and should not limit the protection scope of the present disclosure. The parameter dimension of D(m,n,rdif,r,k) is determined by simplification using symmetry. If the symmetry is not used, the parameter dimension can be increased, or a certain error can be accepted to further simplify the parameter dimension, which should all be within the protection scope of the present disclosure.

[0105] In this embodiment, an initial LOR of a coincidence event between target detector crystal groups is defined, and n DOI In the layer DOI structure, it is divided into n DOI ×n DOI The root target LOR. The sum of the efficiency expectations of these target LORs is equal to the initial LOR, and the normalization factor correction coefficient can be considered as the inverse of the target LOR efficiency expectation, so it is defined as:

[0106]

[0107] Methods for determining the parameters D(m,n,rdif,r,k) include analytical calculations based on crystal geometry, attenuation coefficients, and ray incidence directions.

[0108] For analytical calculation, take two-dimensional analytical calculation as an example:

[0109] Assume that the target LOR for the event is Figure 4 As shown in the figure, the DOI interlayer information is divided along the crystal depth direction. The DOI interlayer information at one end of the event is m layers, that is, the deposition depth at one end of the event is the mth layer, and the other end is n layers (counting from 0), that is, the deposition depth at the other end of the event is the nth layer. If the angles of the target LOR relative to the detector surface are θ 1 and θ 2 , there are n DOI For a single-layer DOI crystal with a single-layer thickness of d, the detection efficiency of the target LOR in the crystal is related to the linear attenuation coefficient μ of the crystal. The normalization factor correction coefficient of the target LOR corresponding to the m-layer and n-layer can be approximated as:

[0110]

[0111] The normalization factor correction coefficient of the target response line relative to the initial response line can be calculated by the above formula.

[0112] For DOI inter-layer information, n DOI The number of LORs of a layer DOI crystal is n without DOI layer information. DOI 2 For example, a DOI crystal with 8 layers has 64 times the number of LORs as a crystal without DOI interlayer information. The more layers there are, the greater the amount of calculation, which greatly increases the complexity and statistics of the correction.

[0113] The correction method of the PET system in this embodiment is based on the traditional initial normalization correction factor of the initial LOR that is independent of the DOI interlayer information, and introduces a normalization factor correction coefficient of the target LOR related to the DOI interlayer information relative to the initial LOR. The target normalization correction factor corresponding to the target LOR is obtained by multiplying the initial normalization correction factor and the normalization factor correction coefficient, thereby realizing normalization correction of the PET system. Without increasing the complexity and statistics of the correction, the accuracy of the detector reconstructed image of the PET system with DOI interlayer information is improved, and the maintainability of the PET system is greatly improved.

[0114] In an optional embodiment, if Figure 5 As shown, the above step S103 includes:

[0115] S1031. Obtain the total count of initial response lines corresponding to the target detector crystal group that are independent of the interaction depth interlayer information.

[0116] S1032. Obtain the total count of target response lines related to the interaction depth interlayer information corresponding to the target detector crystal group.

[0117] S1033. Based on the total count of the initial response line and the total count of the target response line, obtain a normalization factor correction coefficient of the target response line relative to the initial response line.

[0118] The method for determining the parameter D(m,n,rdif,r,k) also includes Monte Carlo simulation and experimental measurement. Through Monte Carlo simulation or standard phantom experiment, the count amount (total count) of the target LOR of the event corresponding to the target detector crystal group with different DOI interlayer information conforming to the event, and the total count of the initial response line corresponding to the target detector crystal group that is independent of the interaction depth interlayer information are obtained, and based on the total count of the initial response line and the total count of the target response line, the normalization factor correction coefficient of the target response line relative to the initial response line is determined.

[0119] In an optional embodiment, if Figure 6 As shown, the above step S1033 includes:

[0120] S10331. Calculate the ratio of the total count of the initial response line to the total count of the target response line, and use the ratio as a normalization factor correction coefficient.

[0121] Specifically, the ratio of the count amount of the initial LOR to the count amount of the target LOR of the event matching the information between different DOI layers is obtained through Monte Carlo simulation or through standard model experiments.

[0122] The formula for determining the normalization factor correction coefficient based on the ratio of the number of counts of the initial LOR to the number of counts of the target LOR is as follows:

[0123]

[0124] Among them, C(rdif,r,k) is the total initial LOR count corresponding to the target detector crystal group and is independent of the interaction depth interlayer information, and C(m,n,rdif,r,k) is the total target LOR count related to the interaction depth interlayer information corresponding to the target detector crystal group. Specifically, C(rdif,r,k) is the total initial LOR count with ring difference rdif, ring direction ordinal r, and angle ordinal k, which is independent of DOI interlayer information, and C(m,n,rdif,r,k) is the target LOR count with crystal ring difference rdif, ring direction ordinal r, ring direction angle ordinal k, DOI layer number m at one end, and DOI layer number n at the other end.

[0125] Since the normalization correction is aimed at True coincidence events that have not been scattered or deflected before entering the detector, in Monte Carlo simulation, the simulation model is generally required to be a non-attenuated model that covers the full-space effective LOR. The available solutions include full-space non-attenuated barrel source, rotating surface source, rotating rod source, etc. In experimental measurement, since scattering events should be reduced as much as possible, rotating rod source or rotating surface source is generally used for measurement.

[0126] Generally, for convenience, D(m,n,rdif,r,k) is pre-stored list data, but D(m,n,rdif,r,k) calculated in real time also falls within the protection scope of the present disclosure.

[0127] The correction method of the PET system in this embodiment can quickly and accurately calculate the normalization factor correction coefficient of the target LOR related to the DOI interlayer information relative to the initial LOR. It is based on the traditional initial normalization correction factor of the initial LOR that is independent of the DOI interlayer information, and obtains the target normalization correction factor corresponding to the target LOR through the product value of the initial normalization correction factor and the normalization factor correction coefficient, thereby realizing normalization correction of the PET system. Without increasing the complexity and statistics of the correction, the accuracy of the detector reconstructed image of the PET system with DOI interlayer information is improved, and the maintainability of the PET system is greatly improved.

[0128] In an optional embodiment, if Figure 7 As shown, the correction method also includes:

[0129] S105: Obtain the spatial position corresponding to each target response line.

[0130] S106: Merge a plurality of target response lines within the same preset spatial position range into a same virtual reconstruction response line.

[0131] S107 . Based on the target normalization correction factors corresponding to the plurality of target response lines, respectively, a reconstruction normalization correction factor corresponding to the virtual reconstruction response line is obtained.

[0132] S108. Calibrate the PET system based on the reconstructed normalized correction factor.

[0133] Several target response lines within the same preset spatial position range, that is, several target response lines with close positions in space.

[0134] In PET reconstruction, due to the large number of target LORs that match events between DOI layers, reconstruction is often required on the LOR dimension after rebin (data rearrangement). That is, it is assumed that some target LORs that are close in space (i.e., in the same preset spatial position range) are merged into the same LOR (i.e., virtual reconstruction LOR) for calculation. At this time, the target normalization correction factor of the virtual reconstruction LOR is expressed as N rebin If N rebin The calculation formula is as follows:

[0135]

[0136] where n rebin is the total count (number of roots) of all target LORs in the rebin LOR process, N k is the target normalization correction factor for each target LOR, which is the aforementioned N(uim,vjn).

[0137] LORs that are close in spatial position are regarded as one LOR. For example, hundreds of close target LORs are approximately regarded as one virtual reconstruction LOR, thereby improving the reconstruction speed.

[0138] In an optional embodiment, if Figure 8 As shown, the above step S104 includes:

[0139] S1042: Based on the initial normalization correction factor and the normalization factor correction coefficient, obtain a target normalization correction factor corresponding to the target response line.

[0140] S1043. Reconstruct the PET image based on the target normalized correction factor to calibrate the PET system.

[0141] After obtaining the target normalized correction factor corresponding to the target response line, the PET image is reconstructed based on the target normalized correction factor to achieve correction of the PET system and improve the resolution of the reconstructed image.

[0142] Fig. 9 Comparison diagrams of uniform water models are shown when not using DOI interlayer information for reconstruction (i.e., Non-DOI recon), when using an incorrect DOI normalization correction factor for reconstruction (DOI recon with incorrect DOI NC), and when using the correct target normalization correction factor provided by the present invention (DOI recon with correct DOI NC). From the comparison, it can be seen that the water film image reconstructed using the target normalization correction factor of the present invention is very uniform, thereby verifying the superiority of the technical solution of the present invention.

[0143] Example 2

[0144] This embodiment provides a correction system for a PET system, which is applied to a PET system including interaction depth inter-layer information, such as Fig.10 As shown, the correction system includes:

[0145] A first data acquisition module 1 is used to acquire an initial normalized correction factor of an initial response line corresponding to a target detector crystal group in a PET system;

[0146] Among them, the initial response line has nothing to do with the interaction depth interlayer information;

[0147] A second data acquisition module 2 is used to determine the target response line corresponding to the target detector crystal group based on the interaction depth interlayer information;

[0148] A third data acquisition module 3 is used to obtain a normalization factor correction coefficient of the target response line relative to the initial response line;

[0149] The data processing module 4 is used to obtain a target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient, so as to calibrate the PET system.

[0150] In an optional embodiment, the first data acquisition module 1 is further used to acquire an initial normalized correction factor of an initial response line corresponding to the target detector crystal group in the PET system based on a preset normalized correction method;

[0151] Among them, the preset normalization correction method includes but is not limited to a direct normalization correction method and a component normalization correction method.

[0152] In an optional embodiment, the data processing module 4 is further used to calculate the product value of the initial normalization correction factor and the normalization factor correction coefficient, and use the product value as the target normalization correction factor to calibrate the PET system.

[0153] In an optional implementation, the third data acquisition module 3 includes:

[0154] An initial total count acquisition unit 31 is used to acquire the total count of initial response lines corresponding to the target detector crystal group and independent of the interaction depth interlayer information;

[0155] A target total count acquisition unit 32 is used to acquire a total count of target response lines related to interaction depth interlayer information corresponding to the target detector crystal group;

[0156] The correction coefficient acquisition unit 33 is used to acquire a normalization factor correction coefficient of the target response line relative to the initial response line based on the total count of the initial response line and the total count of the target response line.

[0157] In an optional implementation, the correction coefficient acquisition unit 33 is further configured to calculate a ratio between the total count of the initial response line and the total count of the target response line, and use the ratio as a normalization factor correction coefficient.

[0158] In an optional embodiment, the correction system further includes:

[0159] A position acquisition module 5 is used to acquire the spatial position corresponding to each target response line;

[0160] A merging module 6, used to merge a plurality of target response lines within the same preset spatial position range into a same virtual reconstruction response line;

[0161] A reconstruction factor acquisition module 7, used for acquiring a reconstruction normalization correction factor corresponding to a virtual reconstruction response line based on target normalization correction factors corresponding to a plurality of target response lines;

[0162] The correction module 8 is used to calibrate the PET system based on the reconstructed normalized correction factor.

[0163] In an optional implementation, the data processing module 4 includes:

[0164] A target factor acquisition unit 41 is used to acquire a target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient;

[0165] The image reconstruction unit 42 performs PET image reconstruction based on the target normalized correction factor to calibrate the PET system.

[0166] The correction system of the PET system of this embodiment corresponds to the correction method of the PET system in Example 1. The working principle of the correction system of the PET system of this embodiment is the same as the working principle of the correction method of the PET system in Example 1, which will not be repeated here.

[0167] The correction system of the PET system in this embodiment is based on the traditional initial normalization correction factor of the initial LOR that is independent of the DOI interlayer information, and introduces a normalization factor correction coefficient of the target LOR related to the DOI interlayer information relative to the initial LOR. The target normalization correction factor corresponding to the target LOR is obtained through the initial normalization correction factor and the normalization factor correction coefficient, thereby realizing normalization correction of the PET system. Without increasing the complexity and statistics of the correction, the accuracy of the detector reconstructed image of the PET system with DOI interlayer information is improved, and the maintainability of the PET system is greatly improved.

[0168] Example 3

[0169] This embodiment provides a PET system, which includes the correction system of the PET system in Embodiment 2.

[0170] The PET system may also include other components, such as a bed, a housing, and detector crystals.

[0171] The PET system of this embodiment is based on the correction system of the PET system in Example 2. It takes the traditional initial normalization correction factor of the initial LOR that is independent of the DOI interlayer information as a basis, introduces a normalization factor correction coefficient of the target LOR related to the DOI interlayer information relative to the initial LOR, and obtains the target normalization correction factor corresponding to the target LOR through the initial normalization correction factor and the normalization factor correction coefficient, thereby realizing normalization correction of the PET system. Without increasing the complexity and statistics of the correction, the accuracy of the detector reconstructed image of the PET system with DOI interlayer information is improved, and the maintainability of the PET system is greatly improved.

[0172] Example 4

[0173] This embodiment provides an electronic device, Fig.11 This is a schematic diagram of the structure of an electronic device provided in this embodiment. The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the correction method of the PET system in the above-mentioned embodiment 1 is implemented. Fig.11 The electronic device 70 shown is only an example and should not limit the functions and scope of use of the embodiments of the present disclosure. Fig.11 As shown, the electronic device 70 may be in the form of a general-purpose computing device, for example, it may be a server device. The components of the electronic device 70 may include, but are not limited to: at least one processor 71, at least one memory 72, and a bus 73 connecting different system components (including the memory 72 and the processor 71).

[0174] The bus 73 includes a data bus, an address bus, and a control bus.

[0175] The memory 72 may include a volatile memory, such as a random access memory (RAM) 721 and / or a cache memory 722 , and may further include a read-only memory (ROM) 723 .

[0176] The memory 72 may also include a program tool 725 (or utility) having a set (at least one) of program modules 724, such program modules 724 including but not limited to: an operating system, one or more application programs, other program modules and program data, each of which or some combination may include an implementation of a network environment.

[0177] The processor 71 executes various functional applications and data processing by running the computer programs stored in the memory 72, such as the calibration method of the PET system in the above-mentioned embodiment 1.

[0178] The electronic device 70 may also communicate with one or more external devices 74. Such communication may be performed via an input / output (I / O) interface 75. Furthermore, the model generating electronic device 70 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 76. Fig.11 As shown, the network adapter 76 communicates with other modules of the electronic device 70 via the bus 73. It should be understood that, although not shown in the figure, other hardware and / or software modules can be used in conjunction with the electronic device 70, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, and data backup storage systems, etc.

[0179] It should be noted that although several units / modules or sub-units / modules of the electronic device are mentioned in the above detailed description, this division is merely exemplary and not mandatory. In fact, according to the embodiments of the present disclosure, the features and functions of two or more units / modules described above can be embodied in one unit / module. Conversely, the features and functions of one unit / module described above can be further divided into multiple units / modules to be embodied.

[0180] Example 5

[0181] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the correction method of the PET system in the above-mentioned embodiment 1 is implemented.

[0182] The readable storage medium may include but is not limited to: a portable disk, a hard disk, a random access memory, a read-only memory, an erasable programmable read-only memory, an optical storage device, a magnetic storage device or any suitable combination of the above.

[0183] In a possible implementation, the present disclosure may also be implemented in the form of a program product, which includes program code. When the program product is run on a terminal device, the program code is used to enable the terminal device to execute the steps in the correction method of the PET system in the above-mentioned embodiment 1.

[0184] Among them, the program code for executing the present disclosure can be written in any combination of one or more programming languages, and the program code can be executed completely on the user device, partially on the user device, as a separate software package, partially on the user device and partially on a remote device, or completely on the remote device.

[0185] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. A calibration method for a PET system, characterized in that: Applied to a PET system including interaction depth inter-layer information, the correction method comprises: Obtaining an initial normalized correction factor for an initial response line corresponding to a target detector crystal group in the PET system; Wherein, the initial response line is independent of the interaction depth interlayer information; Determining a target response line corresponding to the target detector crystal group based on the interaction depth interlayer information; Obtaining a normalization factor correction coefficient of the target response line relative to the initial response line; Based on the initial normalization correction factor and the normalization factor correction coefficient, a target normalization correction factor corresponding to the target response line is obtained to calibrate the PET system.

2. The calibration method according to claim 1, characterized in that: The step of obtaining the initial normalized correction factor of the initial response line corresponding to the target detector crystal group in the PET system comprises: Based on a preset normalization correction method, the initial normalization correction factor of the initial response line corresponding to the target detector crystal group in the PET system is obtained.

3. The calibration method according to claim 1, characterized in that: The step of obtaining the target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient to calibrate the PET system includes: The product value of the initial normalization correction factor and the normalization factor correction coefficient is calculated, and the product value is used as the target normalization correction factor to calibrate the PET system.

4. The calibration method according to claim 1, characterized in that: The step of obtaining a normalization factor correction coefficient of the target response line relative to the initial response line comprises: Obtaining a total count of initial response lines corresponding to the target detector crystal group that are independent of the interaction depth interlayer information; Obtaining a total count of target response lines corresponding to the target detector crystal group and related to the interaction depth interlayer information; The normalization factor correction coefficient of the target response line relative to the initial response line is obtained based on the total count of the initial response line and the total count of the target response line.

5. The calibration method according to claim 4, characterized in that: The step of obtaining the normalization factor correction coefficient of the target response line relative to the initial response line based on the total count of the initial response line and the total count of the target response line includes: The ratio of the total count of the initial response line to the total count of the target response line is calculated, and the ratio is used as the normalization factor correction coefficient.

6. The calibration method according to claim 1, characterized in that: The correction method also includes: Obtaining the spatial position corresponding to each of the target response lines; Merging a plurality of target response lines within the same preset spatial position range into a same virtual reconstruction response line; Based on the target normalized correction factors respectively corresponding to the plurality of target response lines, obtaining a reconstruction normalized correction factor corresponding to the virtual reconstruction response line; calibrating the PET system based on the reconstruction normalization correction factor; And / or, the step of obtaining the target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient to calibrate the PET system includes: Based on the initial normalization correction factor and the normalization factor correction coefficient, acquiring the target normalization correction factor corresponding to the target response line; A PET image is reconstructed based on the target normalized correction factor to calibrate the PET system.

7. A calibration system for a PET system, characterized in that: Applied to a PET system including interaction depth inter-layer information, the correction system comprises: A first data acquisition module is used to acquire an initial normalized correction factor of an initial response line corresponding to a target detector crystal group in the PET system; Wherein, the initial response line is independent of the interaction depth interlayer information; A second data acquisition module is used to determine the target response line corresponding to the target detector crystal group based on the interaction depth interlayer information; A third data acquisition module, used to acquire a normalization factor correction coefficient of the target response line relative to the initial response line; A data processing module is used to obtain a target normalized correction factor corresponding to the target response line based on the initial normalized correction factor and the normalized factor correction coefficient, so as to calibrate the PET system.

8. A PET system, characterized in that: A calibration system for a PET system comprising the steps of claim 7.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and used to run on the processor, characterized in that: When the processor executes the computer program, the correction method for the PET system according to any one of claims 1 to 6 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the correction method of the PET system according to any one of claims 1 to 6 is implemented.

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