Pet system and its calibration method, system, device and medium

Abstract

The disclosure provides a PET system and a correction method, system, device and medium thereof, the correction method comprising: obtaining 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 interaction depth interlayer information; obtaining a normalization factor correction coefficient of the target response line relative to the initial response line; and obtaining a target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient, so as to correct the PET system. The disclosure obtains the target normalization correction factor corresponding to the target LOR related to the DOI based on the initial LOR unrelated to the DOI, realizes the normalization correction of the PET system, and improves the accuracy of the PET system reconstruction image with the DOI interlayer information and the maintainability of the PET system without increasing the correction complexity and statistics.

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

[0002] PET is a high-end nuclear medical imaging diagnostic device. In actual operation, a radionuclide is used to label metabolites. The labeled metabolite drug emits a positron through decay, which annihilates with the surrounding electrons to produce a pair of photons with opposite directions of emission. If two photons are simultaneously detected by the detector crystals of the PET detection system, it is considered that the radionuclide is on the line connecting the pair of detectors (a group of detectors) corresponding to the detected photons, which is called a line of response (LOR). The set of all response lines in each examination forms the original data of PET, which is called list-mode data. When a large range is imaged by PET, a moving scanning mode is usually adopted. The moving position of the bed body is usually transmitted to the PET detection system in real time and stored in the list-mode data. Through a series of physical corrections on the list-mode data, a three-dimensional image is finally generated by a reconstruction algorithm, functional metabolic imaging is performed, and the situation of life metabolism is reflected.

[0003] Since the depth of interaction between the annihilation photons and the detector crystals is arbitrary, even inter-crystal penetration occurs, there is a serious depth of interaction (DOI) effect or radial parallax in the determined transverse PET system field of view, that is, the resolution of the reconstructed image at different radial positions is not uniform. In particular, when the object is close to the edge of the field of view, the resolution will be significantly reduced and a serious "smearing" effect will be presented.

[0004] The normalization correction scheme of the PET system is 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 system, due to the excessive amount of statistics required, it is generally not implemented.

[0005] Component normalization is a method of decomposing LOR-level normalization into multiple smaller dimensions to reduce the correction complexity and the required amount of statistics. For example, the correction method using a moving phantom for a long-axis system, but current methods have not involved PET systems with DOI information.

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

[0007] If the number of DOI division layers is not large, the traditional component normalization method can be continued to be used, and the detector can be considered as only the number of crystals is doubled. However, for a DOI detector with many layers, this method cannot be continued to be used, or it is extremely difficult to continue to be used, because the required statistics is too large. SUMMARY

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

[0009] The present disclosure solves the above technical problems by the following technical solutions:

[0010] The positive progress effect of the present disclosure is that:

[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 normalization correction factor of an initial response line corresponding to a target detector crystal group in the PET system;

[0013] 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 correct the PET system.

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

[0018] obtaining 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 mode;

[0019] Preferably, the preset normalization correction mode comprises a direct normalization correction mode and / or a component normalization correction mode.

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

[0021] calculating the product value of the initial normalization correction factor and the normalization factor correction coefficient, and taking the product value as the target normalization correction factor to correct the PET system.

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

[0023] obtaining the initial response line total count corresponding to the target detector crystal group irrelevant to the interaction depth interlayer information;

[0024] obtaining the target response line total count corresponding to the target detector crystal group relevant to the interaction depth interlayer information;

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

[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 initial response line total count and the target response line total count comprises:

[0027] calculating the ratio of the initial response line total count and the target response line total count, and taking the ratio as the normalization factor correction coefficient.

[0028] Preferably, the correction method further comprises:

[0029] obtaining the spatial position corresponding to each target response line;

[0030] merging a plurality of target response lines in the same preset spatial position range into a same virtual reconstructed response line;

[0031] obtain a reconstruction normalization correction factor corresponding to the virtual reconstructed response line based on the target normalization correction factors corresponding to the target response lines respectively;

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

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

[0034] obtain the target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient;

[0035] perform PET image reconstruction based on the target normalization correction factor to correct the PET system.

[0036] The second aspect further provides a correction system of a PET system, applied to a PET system including interaction depth interlayer information, the correction system comprising:

[0037] a first data obtaining module, configured to obtain an initial normalization 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 irrelevant to the interaction depth interlayer information;

[0039] a second data obtaining 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 obtaining module, configured to obtain a normalization factor correction coefficient of the target response line relative to the initial response line;

[0041] a data processing module, configured to obtain a target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient to correct the PET system.

[0042] Preferably, the first data obtaining module is further configured to obtain 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 mode;

[0043] wherein the preset normalization correction mode comprises a direct normalization correction mode and / or a component normalization correction mode.

[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, configured to acquire an initial total count of response lines corresponding to the target detector crystal group and independent of the interaction depth interlayer information;

[0047] a target total count acquisition unit, configured 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 configured 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 configured to calculate a 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 includes:

[0051] A position acquisition module, configured to acquire the spatial position corresponding to each target response line;

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

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

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

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

[0056] a target factor acquisition unit, configured to acquire the target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization 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 configured to run on the processor, wherein the processor implements the above-mentioned correction method for the PET system 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 conforming to the common sense in this field, 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 normalization correction factor of the initial response line (LOR) that is independent of the interaction depth (DOI) inter-layer information, and introduces a normalization factor correction coefficient of the target response line related to the interaction depth inter-layer information relative to the initial response line. Through the initial normalization correction factor and the normalization factor correction coefficient, the target normalization correction factor corresponding to the target response line is obtained, 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 including the DOI inter-layer 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 a 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 Example 1 of the present disclosure;

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

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

[0069] Figure 7 A sixth flowchart of a correction method of a PET system according to Embodiment 1 of the present disclosure is provided.

[0070] Figure 8 A seventh flowchart of a correction method of a PET system according to Embodiment 1 of the present disclosure is provided.

[0071] Figure 9 A reconstructed image diagram of a correction method of a PET system according to Embodiment 1 of the present disclosure is provided.

[0072] Figure 10 A structure diagram of a correction system of a PET system according to Embodiment 2 of the present disclosure is provided.

[0073] Figure 11 A structure diagram of an electronic device according to Embodiment 4 of the present disclosure is provided. DETAILED DESCRIPTION

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

[0075] Embodiment 1

[0076] The present embodiment provides a correction method of a PET system, applied to a PET system including interaction depth interlayer information, such as Figure 1 As shown in the figure, the correction method includes:

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

[0078] Wherein, the initial response line is irrelevant to the interaction depth interlayer information.

[0079] S102, determining 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, obtaining a target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient, to correct 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 certain coincidence event are the target detector crystal group in the present disclosure, which can also be called a target detector crystal pair.

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

[0084] For the PET system including DOI interlayer information, the detector crystal has certain DOI interlayer information, i.e. the crystal has certain layers, and according to the DOI interlayer information, it can be known not only which target detector crystal group the coincidence event occurs in, but also which layer of the crystal the coincidence event falls in, i.e. 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, which respectively correspond to the depth of 1 cm and the depth of 1.5 cm from the surface of the crystal. According to the DOI interlayer information, the direction of the gamma ray transmission can be more accurately known, and thus 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 of the embodiment is based on the initial normalization correction factor of the initial LOR which is irrelevant to the DOI interlayer information, introduces the normalization factor correction coefficient of the target LOR relative to the initial LOR which is relevant to the DOI interlayer information, and obtains the target normalization correction factor corresponding to the target LOR through the initial normalization correction factor and the normalization factor correction coefficient, so as to realize the normalization correction of the PET system. Without increasing the complexity and the amount of 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 implementation, as shown in Figure 2 the above step S101 includes:

[0087] S1011, obtaining an initial normalization correction factor of an initial response line corresponding to a target detector crystal group in a PET system based on a preset normalization correction mode.

[0088] The preset normalization correction mode includes a direct normalization correction mode and / or a component normalization correction mode.

[0089] The initial response line corresponding to the target detector crystal group in the PET system, i.e. the response line without DOI interlayer information, the initial normalization correction factor corresponding to the initial response line is irrelevant to the DOI interlayer information, and how to obtain the initial normalization correction factor of the initial response line is the prior art, which will not be described here.

[0090] In an optional implementation, as shown in Figure 3 the above step S104 includes:

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

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

[0093] The following is a specific example to further illustrate the present embodiment.

[0094] Specifically, for a conventional cylindrical PET system with a specific number of rings, the initial normalization correction factor of the initial LOR of the coincidence event of the u-th ring i-th crystal a and the v-th ring j-th crystal b is Nc=N(ui,vj), wherein u, i, v and j are 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 single-ring crystals, 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 are connected to form an initial LOR, and the initial normalization correction factor of the initial LOR is Nc=N(ui,vj).

[0095] If the interaction depth layer information corresponds to the m-th layer in crystal a and the n-th layer in crystal b, it can be known that the target response line occurs in the m-th layer in crystal a and the n-th layer in crystal b, and the target normalization correction factor corresponding to the target response line is Nm=N(uim,vjn), wherein 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 m-th layer of crystal a, vjn corresponds to the n-th layer of crystal b, and the photon incident point of the m-th layer of crystal a and the photon incident point of the n-th layer of crystal b are connected to form a target LOR, and the target LOR is a more accurate LOR relative to the initial LOR, and 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] N(uim,vjn)=N(ui,vj)*D(m,n,rdif,r,k);

[0098] wherein, the parameters of D in D(m, n, rdif, r, k) include DOI layer number m and n, crystal ring difference rdif = |u-v|, target LOR ring direction ordinal number r (irad), and target LOR ring direction angle ordinal number k (iphi) in addition. The normalization factor correction coefficient D(m, n, rdif, r, k) can be obtained from the sinogram data corresponding to the target LOR, and can be obtained by table lookup.

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

[0100] After the gamma ray is incident on the crystal, the deposition probability between different DOI crystals is determined by the incident direction of the gamma ray, the DOI layer thickness, 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 for determining the relative direction of the target LOR and the crystal.

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

[0102] For example, for different target LORs with rotational symmetry, the same coefficient can be shared, i.e. k = i wherein, i phi refers to the target LOR ring direction angle ordinal number without considering the rotational symmetry, is the number of target LOR symmetry angles. Assuming that a ring of a PET detector has 1000 detector crystals, the angle is generally defined as 500 angles from 0 to 180 degrees, i.e. there are 500 different angles from 0 to 180 degrees. For different target LORs with rotational symmetry, the same coefficient can be used, so the angle coefficient k is selected as the input parameter. Assuming that the detector crystal ring is a 50-hedron, and each face has 20 detectors, the 0th angle and the 20th angle are rotationally symmetric, so only the coefficients k from 0 to 19 need to be generated, and the others can be directly found by rotational symmetry. When the symmetry is not considered, i phi is 0-499, and when the symmetry is considered, i phi is 0-19, and the available dimension of k is changed from 0-499 to 00-19, which simplifies the data amount of the lookup table.

[0103] For LORs that are symmetrical 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 symmetrical 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 scope of protection of the present disclosure. The parameter dimension of D(m,n,rdif,r,k) is determined by simplification using symmetry. If 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 scope of protection of the present disclosure.

[0105] In this embodiment, an initial LOR of a coincidence event between target detector crystal groups is defined. DOI Under 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 the two-dimensional analytical calculation as an example:

[0109] Assume that the target LOR of the event is as follows Figure 4 As shown, the DOI interlayer information is divided along the crystal depth direction. If 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 θ1 and θ2 respectively, there are a total of n DOI For a single-layer DOI crystal with a 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 using the above formula.

[0112] For DOI interlayer information corresponding n DOI Layer DOI crystal, the number of LORs is n without DOI interlayer information DOI 2 times, for example, a DOI crystal with 8 layers, the number of LORs is 64 times without DOI interlayer information, the more the number of layers, the more the amount of calculation, greatly increasing the complexity and statistics of correction.

[0113] The correction method of the PET system of the embodiment is based on the initial normalization correction factor of the initial LOR without DOI interlayer information, introduces the normalization factor correction coefficient of the target LOR relative to the initial LOR related to the DOI interlayer information, 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, and realizes the normalization correction of the PET system, improves the accuracy of the detector reconstruction image of the PET system with DOI interlayer information without increasing the complexity and statistics of correction, and greatly improves the maintainability of the PET system.

[0114] In an optional embodiment, as shown in Figure 5 The above step S103 includes:

[0115] S1031, obtaining the initial response line total count corresponding to the target detector crystal group without DOI interlayer information.

[0116] S1032, obtaining the target response line total count corresponding to the target detector crystal group related to the DOI interlayer information.

[0117] S1033, based on the initial response line total count and the target response line total count, obtaining the 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) further includes Monte Carlo simulation and experimental measurement. Through Monte Carlo simulation or standard phantom experiment, the count quantity (total count) of the target LOR corresponding to the different DOI interlayer information coincidence events of the target detector crystal group is obtained, and the initial response line total count corresponding to the target detector crystal group without DOI interlayer information is obtained. Based on the initial response line total count and the target response line total count, the normalization factor correction coefficient of the target response line relative to the initial response line is determined.

[0119] In an optional embodiment, as shown in Figure 6 The above step S1033 includes:

[0120] S10331、calculate the ratio of the initial response line total count and the target response line total count, and correct the ratio as a normalization factor correction coefficient.

[0121] Specifically, the ratio of the initial LOR count quantity and the target LOR count quantity of the different DOI interlayer information coincidence events is obtained by Monte Carlo simulation or by a standard phantom experiment to determine.

[0122] The formula for determining the normalization factor correction coefficient according to the ratio of the initial LOR count quantity and the target LOR count quantity is as follows:

[0123]

[0124] Wherein, C(rdif,r,k) is the initial LOR total count corresponding to the target detector crystal group irrelevant to the interaction depth interlayer information, C(m,n,rdif,r,k) is the target LOR total count corresponding to the target detector crystal group relevant to the interaction depth interlayer information, specifically, C(rdif,r,k) is the initial LOR total count with ring difference rdif, ring ordinal number r, and angle ordinal number k, irrelevant to the DOI interlayer information, and C(m,n,rdif,r,k) is the target LOR count with crystal ring difference rdif, ring ordinal number r, ring angle ordinal number k, one end DOI layer number m, and the other end DOI layer number n.

[0125] Since the normalization correction is for the True coincidence events that have not occurred scattering and deflection before entering the detector, in the Monte Carlo simulation, generally, a non-attenuation phantom covering the full space effective LOR needs to be simulated, and the schemes that can be used include a full space non-attenuation barrel source, a rotating plane source, a rotating rod source, etc. In the experimental measurement, since the scattering events need to be reduced as much as possible, generally, a rotating rod source or a rotating plane source is used for measurement.

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

[0127] The correction method of the PET system of the embodiment can quickly and accurately calculate the normalization factor correction coefficient of the target LOR relative to the initial LOR related to the DOI interlayer information, and based on the initial normalization correction factor of the initial LOR unrelated to the DOI interlayer information, obtain 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, so as to realize the normalization correction of the PET system, improve the accuracy of the detector reconstruction image of the PET system with the DOI interlayer information, and greatly improve the maintainability of the PET system.

[0128] In an optional embodiment, as shown in Figure 7 the correction method further comprises:

[0129] S105, acquiring the spatial position corresponding to each target response line.

[0130] S106, merging several target response lines in the same preset spatial position range into a same virtual reconstruction response line.

[0131] S107, acquiring the reconstruction normalization correction factor corresponding to the virtual reconstruction response line based on the target normalization correction factors corresponding to the several target response lines.

[0132] S108, correcting the PET system based on the reconstruction normalization correction factor.

[0133] The several target response lines in the same preset spatial position range are several target response lines close in space.

[0134] In PET reconstruction, due to the excessive number of target LORs of DOI interlayer coincidence events, it is often necessary to perform reconstruction on the LOR dimension after rebinning (data rearrangement). That is, it is assumed that several target LORs close in space (i.e., in the same preset spatial position range) are merged into a same LOR (i.e., a virtual reconstruction LOR) for calculation. At this time, the target normalization correction factor of the virtual reconstruction LOR is represented by N rebin , and the calculation formula of N rebin is as follows:

[0135]

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

[0137] The LORs close to each other are regarded as one LOR, for example, several hundred close target LORs are regarded as one virtual reconstructed LOR, so as to improve the reconstruction speed.

[0138] In an optional embodiment, as shown in Figure 8 The step S104 includes:

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

[0140] S1043, performing PET image reconstruction based on the target normalization correction factor to correct the PET system.

[0141] After obtaining the target normalization correction factor corresponding to the target response line, the PET image reconstruction is performed based on the target normalization correction factor to correct the PET system, thereby improving the resolution of the reconstructed image.

[0142] Figure 9 The comparative diagram of the uniform water phantom reconstructed without using DOI interlayer information (i.e. Non-DOI recon), with incorrect DOI normalization correction factor (DOI recon with incorrect DOI NC), and with the correct target normalization correction factor provided by the present disclosure (DOI recon with correct DOI NC) is shown, and it can be seen from the comparison that the water film image reconstructed with the target normalization correction factor of the present disclosure is very uniform, thereby verifying the superiority of the technical solution of the present disclosure.

[0143] Embodiment 2

[0144] The present embodiment provides a correction system of a PET system, which is applied to a PET system including interaction depth interlayer information, as shown in Figure 10 The correction system includes:

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

[0146] The initial response line is irrelevant to the interaction depth interlayer information;

[0147] A second data acquisition module 2 is configured to determine a 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 configured to acquire a normalization factor correction coefficient of the target response line relative to the initial response line;

[0149] The data processing module 4 is configured to obtain a target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient, and correct the PET system based on the target normalization correction factor.

[0150] In an optional embodiment, the first data obtaining module 1 is further configured to obtain 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 mode.

[0151] The preset normalization correction mode includes, but is not limited to, a direct normalization correction mode and an assembly normalization correction mode.

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

[0153] In an optional embodiment, the third data obtaining module 3 includes:

[0154] The initial total count obtaining unit 31 is configured to obtain an initial response line total count corresponding to the target detector crystal group and irrelevant to the interaction depth layer information.

[0155] The target total count obtaining unit 32 is configured to obtain a target response line total count corresponding to the target detector crystal group and relevant to the interaction depth layer information.

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

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

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

[0159] The position obtaining module 5 is configured to obtain a spatial position corresponding to each target response line.

[0160] The merging module 6 is configured to merge a plurality of target response lines within a same preset spatial position range into a same virtual reconstructed response line.

[0161] The reconstruction factor obtaining module 7 is configured to obtain a reconstruction normalization correction factor corresponding to the virtual reconstructed response line based on target normalization correction factors corresponding to the plurality of target response lines respectively.

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

[0163] In an optional embodiment, the data processing module 4 comprises:

[0164] The target factor obtaining unit 41 is configured to obtain a target normalized correction factor corresponding to a target response line based on the initial normalized correction factor and the normalization factor correction coefficient.

[0165] The image reconstruction unit 42 is configured to perform PET image reconstruction based on the target normalized correction factor to correct the PET system.

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

[0167] The correction system of the PET system of the present embodiment is based on the initial normalized correction factor of the initial LOR which is irrelevant to the DOI interlayer information, and introduces the normalization factor correction coefficient of the target LOR relative to the initial LOR which is related to the DOI interlayer information. The target normalized correction factor corresponding to the target LOR is obtained through the initial normalized correction factor and the normalization factor correction coefficient, so as to realize the normalization correction of the PET system. Without increasing the complexity and statistical amount of 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] Embodiment 3

[0169] The present embodiment provides a PET system, which comprises the correction system of the PET system of embodiment 2.

[0170] The PET system can further comprise other components, such as a bed body, a shell, a detector crystal, and the like.

[0171] The PET system of the present embodiment is based on the correction system of the PET system of embodiment 2, and is based on the initial normalized correction factor of the initial LOR which is irrelevant to the DOI interlayer information. The normalization factor correction coefficient of the target LOR relative to the initial LOR which is related to the DOI interlayer information is introduced. The target normalized correction factor corresponding to the target LOR is obtained through the initial normalized correction factor and the normalization factor correction coefficient, so as to realize the normalization correction of the PET system. Without increasing the complexity and statistical amount of 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] Embodiment 4

[0173] The embodiment provides an electronic device, Figure 11 The structure schematic diagram of the electronic device provided by the embodiment is shown, and the electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor implements the correction method of the PET system in Embodiment 1 when executing the computer program. Figure 11 The electronic device 70 shown is merely an example and should not limit the functions and use range of the embodiments of the present disclosure. As Figure 11 shown, the electronic device 70 can be in the form of a general computing device, for example, it can be a server device. The components of the electronic device 70 can include but are not limited to: the above-mentioned at least one processor 71, the above-mentioned at least one memory 72, 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 can include volatile memory, such as a random access memory (RAM) 721 and / or a cache memory 722, and can further include a read-only memory (ROM) 723.

[0176] The memory 72 can also include a program tool 725 (or utility tool) having a set of (at least one) program modules 724, such as an operating system, one or more application programs, other program modules, and program data, and each of these examples, or some combination thereof, can include implementation of a network environment.

[0177] The processor 71 performs various function applications and data processing by running the computer program stored in the memory 72, such as the correction method of the PET system in Embodiment 1.

[0178] The electronic device 70 can also communicate with one or more external devices 74. Such communication can occur via Input / Output (I / O) interface 75. Still yet, such electronic device 70 can communicate with one or more networks, such as a local area network (LAN), a wide area network (WAN), and / or the public network, such as the Internet, via network adapter 76. As Figure 11 shown, the network adapter 76 communicates with the other modules of the electronic device 70 through the bus 73. It should be understood that although not shown, other hardware and / or software modules could be used in conjunction with the electronic device 70, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID (Redundant Array of Independent Disks) systems, tape drives, and data archival storage systems, etc.

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

[0180] Embodiment 5

[0181] The embodiment provides a computer readable storage medium, which stores a computer program. The computer program, when executed by a processor, implements the correction method of the PET system in Embodiment 1.

[0182] More specifically, the readable storage medium can include, but is not limited to, a portable disc, 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 possible embodiments, the disclosure can also be implemented in the form of a program product, which includes program codes for causing a terminal device to execute the steps of the correction method of the PET system in Embodiment 1 when the program product is run on the terminal device.

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

[0185] Although the specific embodiments of the disclosure are described above, those skilled in the art should understand that this is only an illustration, and the protection scope of the disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the disclosure, and such changes and modifications all fall within the protection scope of the 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 includes: 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, wherein: The step of obtaining an initial normalized correction factor of an 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, wherein: The step of obtaining a target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient to calibrate the PET system includes: A 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, wherein: The step of obtaining a normalization factor correction coefficient of the target response line relative to the initial response line includes: Obtaining a total count of initial response lines corresponding to the target detector crystal group that is 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 line of response relative to the initial line of response is obtained based on the total count of the initial line of response and the total count of the target line of response.

5. The calibration method according to claim 4, wherein: 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: A ratio of the total count of the initial line of response to the total count of the target line of response is calculated, and the ratio is used as the normalization factor correction coefficient.

6. The calibration method according to claim 1, wherein: The correction method further comprises: Obtaining the spatial position corresponding to each target response line; Merging a plurality of target response lines within the same preset spatial position range into a same virtual reconstructed response line; Based on the target normalization correction factors respectively corresponding to the plurality of target response lines, obtaining a reconstruction normalization 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 a target normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization factor correction coefficient to calibrate the PET system includes: Based on the initial normalization correction factor and the normalization factor correction coefficient, obtaining the target normalization correction factor corresponding to the target response line; PET image reconstruction is performed 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 obtain 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, configured to determine a target response line corresponding to the target detector crystal group based on the interaction depth interlayer information; a third data acquisition module, configured 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 normalization correction factor corresponding to the target response line based on the initial normalization correction factor and the normalization 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 configured to run on the processor, wherein: 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 calibration method of the PET system according to any one of claims 1 to 6 is implemented.

Images