A method, device, equipment and storage medium for determining bias scanning offset

Abstract

The embodiment of the present application provides a method, device, equipment and storage medium for determining the offset of bias scanning, which belongs to the field of bias scanning technology. The electronic device can obtain projection data obtained by bias scanning the target object; determine the predicted position of the rotation center axis mapped in the detector based on the difference in pixel values ​​of the projection data pairs in each column in the projection data; determine the offset range of the detector according to the difference in pixel values ​​of the projection data pairs within a preset range; determine the offset of the bias scanning according to the fluctuation of the pixel values ​​of the reconstructed image, wherein the preset range is a preset number of columns of data including the predicted position in the projection data, and the reconstructed image is obtained by reconstructing the projection data based on the offset. Since a more accurate offset of the bias scanning is determined by directly analyzing and processing the projection data, there is no need to use a correction model, so the process of determining the offset of the bias scanning can be simplified, and the efficiency of determining the offset of the bias scanning can be improved.

Description

Technical Field

[0001] The present application relates to the field of bias scanning technology, and in particular to a method, device, equipment and storage medium for determining a bias scanning offset. Background Art

[0002] CT (Computed Tomography) technology uses a radiation source to perform layer-by-layer scanning of target objects, which can quickly and clearly image the target object. It is widely used in security inspections, object detection, disease diagnosis, etc. The scanning field of view of CT equipment is limited by the size of the detector. If the size of the target object is close to or exceeds the size of the detector, a complete CT image cannot be obtained.

[0003] In order to obtain a larger scanning field of view under limited conditions, bias scanning has become a common large field of view scanning method. Bias scanning includes two scanning modes: detector bias scanning and turntable bias scanning.

[0004] The scanning field of view of the offset scan is closely related to the offset. The larger the offset, the larger the scanning field of view. In the current related technology, before each offset scan, a correction phantom is needed to calibrate the CT device to obtain accurate geometric parameters such as the offset. As the offset increases, the imaging of the correction phantom may move out of the field of view. In this case, the correction phantom and the correction algorithm need to be improved and optimized accordingly according to the offset. It can be seen that the current method of determining the offset in the related technology is relatively cumbersome and inefficient. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a method, device, equipment and storage medium for determining a biased scanning offset, so as to simplify the process of determining a biased scanning offset and improve the efficiency of determining the biased scanning offset. The specific technical solution is as follows:

[0006] In a first aspect, an embodiment of the present application provides a method for determining a bias scanning offset, which is applied to a bias scanning system, wherein the bias scanning system includes a ray source, a detector, and a turntable for carrying a target object, wherein the turntable is located between the ray source and the detector and can rotate around a rotation center axis, and the method includes:

[0007] Acquire projection data obtained by offset scanning of the target object;

[0008] Determine the predicted position of the rotation center axis mapped in the detector based on the difference in pixel values ​​of the projection data pair in each column in the projection data, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than a preset threshold;

[0009] Determining the offset range of the detector according to the difference in pixel values ​​of the projection data within a preset range, wherein the preset range is a preset number of columns of data in the projection data including the predicted position;

[0010] The offset of the offset scan is determined according to the fluctuation of the pixel value of the reconstructed image, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range.

[0011] In a second aspect, an embodiment of the present application provides a device for determining a bias scanning offset, which is applied to a bias scanning system, wherein the bias scanning system includes a ray source, a detector, and a turntable for carrying a target object, wherein the turntable is located between the ray source and the detector and can rotate around a rotation center axis, and the device includes:

[0012] A data acquisition module, used to acquire projection data obtained by offset scanning of a target object;

[0013] a predicted position determination module, configured to determine a predicted position of the rotation center axis mapped in the detector based on a difference in pixel values ​​of a projection data pair in each column of the projection data, wherein the projection data pair is two projection data having a projection angle difference of a preset value, and a difference between the preset value and 180 degrees is less than a preset threshold;

[0014] An offset range determination module, configured to determine an offset range of the detector according to a difference in pixel values ​​of the projection data within a preset range, wherein the preset range is a preset number of columns of data in the projection data including the predicted position;

[0015] The offset determination module is used to determine the offset of the offset scan according to the fluctuation of the pixel value of the reconstructed image, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range.

[0016] In a third aspect, an embodiment of the present application provides an electronic device, including:

[0017] Memory, used to store computer programs;

[0018] The processor is used to implement any method described in the first aspect when executing a program stored in the memory.

[0019] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any method described in the first aspect is implemented.

[0020] Beneficial effects of the embodiments of the present application:

[0021] In the scheme provided by the embodiment of the present application, the electronic device can obtain the projection data obtained by bias scanning the target object; based on the difference in pixel values ​​of the projection data pair in each column in the projection data, determine the predicted position of the rotation center axis mapping in the detector, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than a preset threshold; according to the difference in pixel values ​​of the projection data pair within a preset range, determine the offset range of the detector, wherein the preset range is a preset number of columns of data including the predicted position in the projection data; according to the fluctuation of the pixel values ​​of the reconstructed image, determine the offset of the bias scanning, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range. If the angle of rotation of the target object is close to 180 degrees, then the two projection data corresponding to the rotation before and after can be approximated to the half and the other half of the target object, respectively. Since these two parts have an overlapping part on the vertical center axis of the target object, and have a large difference on both sides of the vertical center axis, and the vertical center axis coincides with the rotation center axis, the pixel values ​​corresponding to the two projection data near the rotation center axis have a small difference, and the pixel values ​​corresponding to both sides near the rotation center axis have a large difference. Based on this characteristic, the electronic device can determine the predicted position of the rotation center axis mapping in the detector, that is, the approximate position of the detector offset, based on the difference in pixel values ​​of the projection data pairs in each column in the projection data. Furthermore, the offset range of the detector can be determined based on the difference in pixel values ​​of the projection data pairs within a preset range. Next, the projection data can be reconstructed based on the offset within the offset range to obtain a reconstructed image. Assuming that the offset based on which the reconstruction is based is close to the actual offset, the reconstructed image will contain most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be large. Therefore, the electronic device can determine the offset of the offset scan based on the pixel value fluctuation of the reconstructed image. Since a relatively accurate offset scan offset can be determined by directly analyzing and processing the projection data without using a calibration phantom, the process of determining the offset scan offset can be simplified and the efficiency of determining the offset scan offset can be improved. Of course, implementing any product or method of the present application does not necessarily require achieving all of the above advantages at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0023] Figure 1 A flowchart of a method for determining a bias scanning offset provided in an embodiment of the present application;

[0024] Figure 2 Based on Figure 1 A schematic diagram of a vertical cone-beam CT scanning system of the illustrated embodiment;

[0025] Figure 3 for Figure 1 A specific flow chart of step S102 in the illustrated embodiment;

[0026] Figure 4 for Figure 3 A specific flow chart of step S302 in the illustrated embodiment;

[0027] Figure 5 for Figure 1 A specific flow chart of step S103 in the illustrated embodiment;

[0028] Figure 6 for Figure 5 A specific flow chart of step S502 in the illustrated embodiment;

[0029] Figure 7 for Figure 6 A specific flow chart of step S602 in the illustrated embodiment;

[0030] Figure 8 for Figure 6 A specific flow chart of step S604 in the illustrated embodiment;

[0031] Fig. 9 for Figure 1 A specific flow chart of step S104 in the illustrated embodiment;

[0032] Fig.10 for Fig. 9 A specific flow chart of step S902 in the illustrated embodiment;

[0033] Fig.11 for Fig.10 A specific flow chart of step S1003 in the illustrated embodiment;

[0034] Fig.12 Based on Figure 1 A flow chart of determining a detector offset according to the illustrated embodiment;

[0035] Fig.13 Based on Figure 1 A flow chart of determining an offset for a bias scan according to the illustrated embodiment;

[0036] Fig.14 A schematic diagram of the structure of a device for determining a bias scanning offset provided in an embodiment of the present application;

[0037] Fig.15 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field based on the present application belong to the scope of protection of the present application.

[0039] In order to simplify the process of determining the bias scanning offset and improve the efficiency of determining the bias scanning offset, the embodiments of the present application provide a method, device, electronic device, computer-readable storage medium and computer program product for determining the bias scanning offset. The following first introduces a method for determining the bias scanning offset provided by the embodiments of the present application.

[0040] The method for determining the offset of bias scanning provided in the embodiment of the present application can be applied to any electronic device that needs to determine the offset of bias scanning, for example, it can be an image processor, an image processor, a processing device, etc., which is not specifically limited here. For the sake of clarity, it is subsequently referred to as an electronic device in this article.

[0041] like Figure 1 As shown, a method for determining a bias scanning offset is applied to a bias scanning system, wherein the bias scanning system includes a ray source, a detector, and a turntable for carrying a target object, wherein the turntable is located between the ray source and the detector and can rotate around a rotation center axis, and the method includes:

[0042] S101, acquiring projection data obtained by performing offset scanning on a target object;

[0043] S102, determining a predicted position of the rotation center axis mapped in the detector based on a difference in pixel values ​​of a projection data pair in each column of the projection data;

[0044] The projection data pair is two projection data whose projection angle difference is a preset value, and the difference between the preset value and 180 degrees is less than a preset threshold.

[0045] S103, determining an offset range of the detector according to a pixel value difference of the projection data pair within a preset range;

[0046] The preset range is a preset number of columns of data including the predicted position in the projection data.

[0047] S104, determining an offset of the bias scan according to the fluctuation of the pixel value of the reconstructed image.

[0048] The reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range.

[0049] It can be seen that in the embodiment of the present application, the electronic device can obtain the projection data obtained by bias scanning the target object; based on the difference in pixel values ​​of the projection data pair in each column in the projection data, determine the predicted position of the rotation center axis mapping in the detector, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than the preset threshold; according to the difference in pixel values ​​of the projection data pair within a preset range, determine the offset range of the detector, wherein the preset range is a preset number of columns of data including the predicted position in the projection data; according to the fluctuation of the pixel values ​​of the reconstructed image, determine the offset of the bias scanning, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range. If the angle of rotation of the target object is close to 180 degrees, then the two projection data corresponding to the rotation before and after can be approximated to the half and the other half of the target object, respectively. Since these two parts have an overlapping part on the vertical center axis of the target object, and have a large difference on both sides of the vertical center axis, and the vertical center axis coincides with the rotation center axis, the pixel values ​​corresponding to the two projection data near the rotation center axis have a small difference, and the pixel values ​​corresponding to both sides near the rotation center axis have a large difference. Based on this characteristic, the electronic device can determine the predicted position of the rotation center axis mapping in the detector, that is, the approximate position of the detector offset, based on the difference in pixel values ​​of the projection data pairs in each column in the projection data. Furthermore, the offset range of the detector can be determined based on the difference in pixel values ​​of the projection data pairs within a preset range. Next, the projection data can be reconstructed based on the offset within the offset range to obtain a reconstructed image. Assuming that the offset based on which the reconstruction is based is close to the actual offset, the reconstructed image will contain most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be large. Therefore, the electronic device can determine the offset of the offset scan based on the pixel value fluctuation of the reconstructed image. Since a relatively accurate offset of the bias scan can be determined by directly analyzing and processing the projection data without using a correction phantom, the process of determining the offset of the bias scan can be simplified and the efficiency of determining the offset of the bias scan can be improved.

[0050] The application scenario of the present application may be a vertical CT scanning system, for example, a vertical cone-beam CT scanning system. A schematic diagram of a vertical cone-beam CT scanning system may be as follows: Figure 2 As shown, it includes a radiation source S, a target object O and a detector. The target object O is carried on a turntable (not shown in the figure) and can rotate with the turntable. Figure 2As shown, when no offset scanning is performed, the target object is located between the ray source and the detector, and the target point position of the ray source S and the central axis of the detector (passing through the center D) are located on the same straight line SD, and the rotation center axis of the turntable is perpendicular to the horizontal plane where the target point of the ray source S and the central axis of the detector are located.

[0051] Bias scanning can include two methods: detector bias and turntable bias. In actual application, the scanning bias method and bias direction can be determined according to the need to increase the scanning field of view. Detector bias means that compared with the unbiased case, the target position of the ray source S and the turntable position remain unchanged, and the position of the detector changes, for example, the target position of the ray source S and the central axis of the detector are no longer collinear. Turntable bias means that compared with the unbiased case, the target position of the ray source S and the position of the detector remain unchanged, and the position of the turntable changes, for example, the rotation center axis of the turntable deviates from the straight line SD where the target of the ray source S and the central axis of the detector are located by a preset distance. Whether it is detector bias or turntable bias, during the bias scanning process, the target object can rotate with the turntable according to the scanning requirements, thereby obtaining different projection data.

[0052] For example, in Figure 2 In the case, the detector is offset, and the extension line of the line between the target position of the ray source S and the target object O does not intersect the detector at the center D of the detector, but intersects at D'. The interval between the center D and D' of the detector is the offset of the detector. In this case, various parameters of the above-mentioned cone beam CT scanning system can be recorded. For example, the distance SD' between the ray source S and the detector and the distance SO between the ray source S and the rotation center axis can be recorded. The scanning angle, scanning angle interval, voltage and current, etc. can also be recorded. It should be understood that Figure 2 As an example, the case where the detector is biased is shown in which the detector is biased in a direction parallel to the i direction. Similarly, the detector can also be biased in a direction parallel to the j direction, depending on actual needs.

[0053] In step S101, the electronic device may obtain projection data obtained by performing offset scanning on a target object. The target object is a scanned object in a CT scanning system. For example, Figure 2 As shown in FIG. 1 , during the bias scanning process, the positions of the ray source S and the detector remain unchanged, and the target object O rotates along the rotation center axis perpendicular to the horizontal plane with the turntable, so that the projection data of the target object O can be collected. The projection data can be recorded as , where row pixels , column pixels , projection angle , is the number of channels of the row pixels of the detector, is the number of channels of the detector column pixels, is the maximum value of the projection angle, is the projection angle interval. The direction is the row direction of the detector, the vertical axis The direction is the column direction of the detector.

[0054] During the offset scanning process, the target object can rotate around the vertical rotation center axis. Assuming that the target object rotates 180 degrees, the two projection data collected by the detector before and after the rotation can respectively correspond to one half and the other half of the target object.

[0055] For the left and right halves of the target object, the two halves have an overlapped portion on the vertical center axis of the target object, and there is usually a difference on both sides of the vertical center axis. Since the rotation center axis coincides with the vertical center axis of the target object, the pixel value difference between the two projection data is minimal for the position where the rotation center axis is mapped in the detector, and there is a large value fluctuation on both sides near the position where the rotation center axis is mapped in the detector, that is, the pixel value difference between the two projection data is large.

[0056] Based on the above characteristics, the electronic device can determine the predicted position of the rotation center axis mapping in the detector based on the difference in pixel values ​​of the projection data pair in each column in the projection data, that is, execute step S102. The projection data pair can be two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees can be less than a preset threshold.

[0057] The value of the preset threshold is usually small, and can be 0 degree, 0.5 degree, 1 degree, etc., which is not specifically limited here. For example, assuming that the preset threshold is 0 degree, the projection angle difference between the two projection data in the projection data pair is 180 degrees; for another example, assuming that the preset threshold is 1 degree, the projection angle difference between the two projection data in the projection data pair is 179 degrees.

[0058] The above step of determining the predicted position can be implemented in the following two embodiments: In the first embodiment, the electronic device can calculate the pixel value difference in each column of two projection data included in a projection data pair, and determine the column coordinate corresponding to the maximum pixel value difference and the average of the column coordinate corresponding to the minimum pixel value difference as the predicted position. The column coordinate is the identifier of the projection data in the column direction.

[0059] In a second implementation, the electronic device may calculate, for each projection data pair in the plurality of projection data pairs, a pixel value difference between two projection data included in the projection data pair in each column, and calculate the column coordinates corresponding to the maximum pixel value difference and the mean of the column coordinates corresponding to the minimum pixel value difference. Next, an average operation may be performed on the mean values ​​corresponding to each projection data pair, and the obtained result may be determined as the predicted position.

[0060] Since the position of the rotation center axis mapped to the detector is the position of the center of the detector after the detector is offset, the above-mentioned predicted position can also be regarded as the approximate position where the detector is offset. As mentioned above, since the pixel values ​​corresponding to the two projection data included in the projection data pair near the rotation center axis are slightly different, and the pixel values ​​corresponding to the two sides near the rotation center axis are relatively different, the electronic device can determine the offset range of the detector according to the difference in pixel values ​​of the projection data pair within a preset range, that is, execute step S103.

[0061] The preset range may be a preset number of columns of data including the predicted position in the projection data, and the preset number may be set according to actual needs. For example, the preset number may be 5, 7, 9, etc., which is not specifically limited here.

[0062] After determining the detector's offset range, in order to determine the detector's offset within the offset range, the electronic device can perform CT image reconstruction on the projection data based on the offset within the offset range to obtain a reconstructed image. CT image reconstruction is a process of inferring the material attenuation coefficient inside the target object from the projection data.

[0063] If the offset based on which the CT image reconstruction is based is close to the actual detector offset, then the reconstructed image will contain most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be large. Correspondingly, if the offset based on which the CT image reconstruction is based is significantly different from the actual detector offset, then the reconstructed image will lack most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be small.

[0064] Therefore, the electronic device can determine the offset of the bias scan according to the fluctuation of the pixel value of the reconstructed image, that is, execute step S104. Wherein, when the scanning mode of the bias scan is the detector bias scan, the offset of the bias scan determined is the detector offset; when the scanning mode of the bias scan is the turntable bias scan, the offset of the bias scan determined is the turntable offset.

[0065] It can be seen that in the embodiment of the present application, if the angle of rotation of the target object is close to 180 degrees, the two projection data corresponding to the rotation before and after can be respectively approximated to one half of the target object and the other half. Since the two parts have an overlapping part on the vertical center axis of the target object, the difference is large on both sides of the vertical center axis, and the vertical center axis coincides with the rotation center axis, therefore, the pixel values ​​corresponding to the two projection data near the rotation center axis are small, and the pixel values ​​corresponding to both sides near the rotation center axis are large. Based on this characteristic, the electronic device can determine the predicted position of the rotation center axis mapping in the detector based on the difference in pixel values ​​of the projection data pairs in each column in the projection data, that is, the approximate position of the detector offset. Furthermore, the offset range of the detector can be determined based on the difference in pixel values ​​of the projection data pairs within a preset range. Next, the projection data can be reconstructed based on the offset within the offset range to obtain a reconstructed image. Assuming that the offset based on which the reconstruction is based is close to the actual offset, the reconstructed image will contain most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be large. Therefore, the electronic device can determine the offset of the offset scan based on the pixel value fluctuation of the reconstructed image. The method for determining the bias scanning offset provided in the present application can be applied to the field of X-ray non-destructive testing. Since a more accurate bias scanning offset can be determined by directly analyzing and processing the projection data without using a correction model, the process of determining the bias scanning offset can be simplified and the efficiency of determining the bias scanning offset can be improved.

[0066] As an implementation method of the present application, Figure 3 As shown, the step of determining the predicted position of the rotation center axis mapped in the detector based on the pixel value difference of the projection data pair in each column in the projection data may include:

[0067] S301, determining, according to the projection angle of the projection data, a projection data pair whose projection angle difference is a preset value from the projection data;

[0068] The electronic device can determine the projection data whose difference between two corresponding projection angles is a preset value according to the projection angle of the projection data as a projection data pair. For example, assuming the preset value is 180 degrees, the electronic device can select any two projection data whose interval between projection angles is 180 degrees from the projection data and record them as and .in, is the smaller value between the two projection angles, .

[0069] S302, calculating the pixel value difference of the projection data pair in each column, and determining the column coordinate corresponding to the maximum pixel value difference and the column coordinate corresponding to the minimum pixel value difference;

[0070] Since the difference in pixel values ​​corresponding to the two projection data included in the projection data pair is small near the rotation center axis, and the difference in pixel values ​​corresponding to the two sides near the rotation center axis is large, in order to determine the approximate position of the rotation center axis mapped in the detector, the electronic device can calculate the difference in pixel values ​​in each column of the projection data pair, and determine the column coordinates corresponding to the largest pixel value difference, and the column coordinates corresponding to the smallest pixel value difference.

[0071] In one implementation, before executing step S302, filtering processing may be performed on the two projection data included in the projection data pair, and then step S302 is performed based on the projection data pair after filtering processing, that is, the difference in pixel values ​​in each column of the projection data pair after filtering processing is calculated. The filtering processing method may be mean filtering, Gaussian filtering, and median filtering, which are not specifically limited here.

[0072] Assume that the projection data After filtering, it can be expressed as , then and After filtering, we can get and .

[0073] S303: Determine the mean value of the determined column coordinates as the predicted position of the rotation center axis mapped in the detector.

[0074] Since the column coordinate corresponding to the largest pixel value difference is closer to the actual position of the rotation center axis mapped to the detector, and the column coordinate corresponding to the smallest pixel value difference is farther away from the actual position of the rotation center axis mapped to the detector, the actual position of the rotation center axis mapped to the detector is between the column coordinate corresponding to the largest pixel value difference and the column coordinate corresponding to the smallest pixel value difference. The electronic device can determine the mean of the determined column coordinates as the predicted position of the rotation center axis mapped in the detector.

[0075] For example, assuming that the projection data includes 10 columns, and the pixel value differences corresponding to the projection data in columns 1 to 10 are 21, 45, 81, 96, 53, 68, 46, 7, 35 and 69 respectively, then it can be determined that the column coordinate corresponding to the largest pixel value difference is 4, and the column coordinate corresponding to the smallest pixel value difference is 8, and then the mean of the two column coordinates 6 is determined as the predicted position of the rotation center axis mapping in the detector.

[0076] It can be seen that in the embodiment of the present application, the electronic device can determine the projection data pair with the projection angle difference being a preset value from the projection data according to the projection angle of the projection data; calculate the pixel value difference of the projection data pair in each column, and determine the column coordinates corresponding to the maximum pixel value difference and the column coordinates corresponding to the minimum pixel value difference; determine the mean of the determined column coordinates as the predicted position of the rotation center axis mapped in the detector. Since the actual position of the rotation center axis of the maximum pixel value difference mapped to the detector is located between the column coordinates corresponding to the maximum pixel value difference and the column coordinates corresponding to the minimum pixel value difference, the electronic device can calculate the pixel value difference of the projection data pair in each column, and then determine the column coordinates corresponding to the maximum pixel value difference and the column coordinates corresponding to the minimum pixel value difference, and then determine the mean of the determined column coordinates as the predicted position. Since in the process of determining the predicted position, it is based only on one projection data pair, it is possible to reduce the amount of calculation, improve the efficiency of determining the predicted position, and quickly determine the approximate position of the detector offset.

[0077] As an implementation method of the present application, Figure 4 As shown, the step of calculating the pixel value difference of the projection data pair in each column may include:

[0078] S401, subtracting pixel values ​​of each pixel point at the same position in the projection data pair to obtain a first difference image;

[0079] In order to calculate the difference in pixel values ​​of the projection data pair in each column, the electronic device may subtract the pixel values ​​of each pixel point at the same position in the projection data pair to obtain a first difference image.

[0080] Assuming the above process is expressed in the form of a formula, the electronic device can and Subtract and get the difference image ,in, .

[0081] Next, the electronic device may execute any one of step S402 and step S403.

[0082] S402, calculating the mean pixel value of each column of the first difference image;

[0083] After obtaining the first difference image, the electronic device may calculate the average pixel value of each column of the first difference image. Then, the electronic device may determine the column coordinates corresponding to the maximum pixel value average from the pixel value averages of each column as the column coordinates corresponding to the maximum pixel value difference, and determine the column coordinates corresponding to the minimum pixel value average as the column coordinates corresponding to the minimum pixel value difference.

[0084] Assuming that the above process is expressed in the form of a formula, the electronic device can calculate the difference image Find the mean by column, and we get Among them, The formula for solving the column mean is as follows:

[0085] , Represents the difference image In the Row and The pixel value of the column.

[0086] Then, we can determine The column coordinates of the detector corresponding to the maximum and minimum values ​​of and , and then it can be determined that when the detector is offset, the predicted position of the rotation center axis mapped to the detector is List.

[0087] S403: Calculate the pixel value and value of each column of the first difference image.

[0088] After obtaining the first difference image, the electronic device may also calculate the pixel values ​​and values ​​of each column of the first difference image. Then, the electronic device may determine the column coordinates corresponding to the maximum pixel value and value from the pixel values ​​and values ​​of each column as the column coordinates corresponding to the maximum pixel value difference, and determine the column coordinates corresponding to the minimum pixel value and value as the column coordinates corresponding to the minimum pixel value difference.

[0089] It can be seen that in the embodiment of the present application, the electronic device can subtract the pixel values ​​of the same pixel points in each position in the projection data pair to obtain the first difference image; calculate the average value of the pixel values ​​in each column of the first difference image; or calculate the sum of the pixel values ​​in each column of the first difference image. In this way, the difference in the pixel values ​​of the projection data pair in each column can be quickly and accurately determined by any of the above two methods.

[0090] As an implementation method of the present application, Figure 5 As shown, the step of determining the offset range of the detector according to the pixel value difference of the projection data within a preset range may include:

[0091] S501, taking the predicted position as the center column of the range, determining the left boundary of the range to the left, and determining the right boundary of the range to the right, to obtain a preset range including a preset number of columns of data;

[0092] In order to determine the offset of the biased scan near the predicted position, the electronic device can use the predicted position as the center column of the range, determine the left boundary of the range to the left, and determine the right boundary of the range to the right, to obtain a preset range including a preset number of columns of data, that is, execute step S501.

[0093] In one embodiment, the preset number of columns can be determined in advance based on a preset number. In this case, the predicted position can be used as the center column of the range, and the left boundary that is separated from the center column of the range by a preset number of columns can be determined to the left, and the right boundary that is separated from the center column of the range by a preset number of columns can be determined to the right, to obtain a preset range including a preset number of column data.

[0094] Assuming that the above process is expressed in the form of a formula, the electronic device can And the preset number of columns , determine the position of the detector mapped to the rotation center axis when the detector is offset Between columns. Among them, the preset number of columns It is an integer and can be determined based on the accuracy of the CT equipment or can be set manually based on experience.

[0095] S502, determining the offset range of the detector according to the difference in pixel values ​​of each column of a plurality of projection data pairs within the preset range, and the number of column pixels and the pixel size of the detector.

[0096] For two projection data with an imaging projection angle difference of nearly 180 degrees, the imaging values ​​of the two projection data near the rotation center axis are relatively close, and the difference in imaging values ​​will become larger and larger as the displacement moves to the left and right from the rotation center axis. In addition, the number of column pixels and the pixel size of the detector can be used to convert the column coordinates from the coordinate system of the projection data to the world coordinate system. Therefore, the electronic device can determine the displacement range of the detector according to the difference in pixel values ​​of each column within the preset range of the plurality of projection data pairs, as well as the number of column pixels and the pixel size of the detector, that is, execute step S502.

[0097] It can be seen that in the embodiment of the present application, the electronic device can use the predicted position as the center column of the range, determine the left boundary of the range to the left, and determine the right boundary of the range to the right, to obtain a preset range including a preset number of columns of data; determine the offset range of the detector according to the difference in pixel values ​​of each column of the multiple projection data pairs within the preset range, and the number of column pixels and pixel size of the detector. The imaging values ​​of the two projection data included in the projection data pair near the rotation center axis are relatively close, and the difference in imaging values ​​will become larger and larger when shifted to the left and right from the rotation center axis. In addition, the number of column pixels and pixel size of the detector can be used to convert the column coordinates from the coordinate system of the projection data to the world coordinate system. Therefore, the electronic device can determine the offset range of the detector according to the difference in pixel values ​​of each column of the multiple projection data pairs within the preset range, and the number of column pixels and pixel size of the detector. In this way, a more accurate offset range of the detector can be further determined through the determined predicted position.

[0098] As an implementation method of the present application, Figure 6 As shown, the step of determining the offset range of the detector according to the difference in pixel values ​​of each column of the plurality of projection data within the preset range, and the number of column pixels and pixel size of the detector may include:

[0099] S601, determining, from the projection data, a plurality of projection data pairs whose projection angle differences are preset values ​​according to the projection angles of the projection data;

[0100] The electronic device can determine multiple projection data pairs with projection angle differences of a preset value from the projection data according to the projection angle of the projection data, that is, execute step S601. Assuming that the above process is expressed in the form of a formula, taking the preset value of 180 degrees as an example, the electronic device can select The projection data with a difference of 180 degrees are recorded as and ,in, , the projection data pair identification It should be understood that in the above formula It means the The smaller projection angle of the projection data pair is , does not mean and Multiply.

[0101] S602, calculating the pixel value difference of each column of each projection data pair within the preset range, and determining the minimum pixel value difference corresponding to each projection data pair;

[0102] Since the difference in pixel values ​​corresponding to the two projection data included in the projection data pair near the rotation center axis is small, in order to determine the position where the rotation center axis is mapped to the detector, that is, the offset of the detector, the electronic device can calculate the pixel value difference of each column of the projection data pair within a preset range for each projection data pair, and determine the minimum pixel value difference corresponding to the projection data pair, thereby obtaining the minimum pixel value difference corresponding to each projection data pair.

[0103] S603, determining a maximum value and a minimum value from a plurality of minimum pixel value differences;

[0104] Since among multiple minimum pixel value differences, the column coordinate corresponding to the maximum value is the position farthest from the actual offset, and the column coordinate corresponding to the minimum value is the position closest to the actual offset, in order to further reduce the range used to determine the offset based on the preset range, the electronic device can determine the maximum and minimum values ​​from multiple minimum pixel value differences.

[0105] S604 , determining an offset range of the detector based on the column coordinate corresponding to the maximum value, the column coordinate corresponding to the minimum value, and the number of column pixels and the pixel size of the detector.

[0106] When determining the offset of the offset scan, the offset of the detector can be determined first, and then the offset of the offset scan can be determined based on the offset of the detector. The offset of the detector is the distance between the position where the rotation center axis is mapped to the detector and the center of the detector. Since the number of column pixels of the detector can be used to determine the column coordinates of the center of the detector, the column coordinates corresponding to the maximum value and the column coordinates corresponding to the minimum value can represent the fluctuation range of the position where the rotation center axis is mapped to the detector, and the pixel size can convert the column coordinates from the coordinate system of the projection data to the world coordinate system, the electronic device can determine the offset range of the detector based on the column coordinates corresponding to the maximum value, the column coordinates corresponding to the minimum value, and the number of column pixels and the pixel size of the detector.

[0107] It can be seen that in the embodiment of the present application, the electronic device can determine multiple projection data pairs with a projection angle difference of a preset value from the projection data according to the projection angle of the projection data; calculate the pixel value difference of each column of each projection data pair within the preset range, and determine the minimum pixel value difference corresponding to each projection data pair; determine the maximum value and the minimum value from the multiple minimum pixel value differences; determine the offset range of the detector based on the column coordinates corresponding to the maximum value, the column coordinates corresponding to the minimum value, and the number of column pixels and the pixel size of the detector. Since the number of column pixels of the detector can be used to determine the column coordinates of the center of the detector, the column coordinates corresponding to the maximum value and the column coordinates corresponding to the minimum value can be used to determine the fluctuation range of the position of the rotation center axis mapped to the detector, and the pixel size can convert the column coordinates from the coordinate system of the projection data to the world coordinate system, the electronic device can determine the offset range of the detector based on the column coordinates corresponding to the maximum value, the column coordinates corresponding to the minimum value, and the number of column pixels and the pixel size of the detector. In this way, the offset range of the detector can be determined quickly and accurately.

[0108] As an implementation method of the present application, Figure 7 As shown, the step of calculating the pixel value difference of each column of each projection data pair within the preset range may include:

[0109] S701, for each projection data pair, subtract the pixel values ​​of each pixel point at the same position in the projection data pair to obtain a second difference image;

[0110] In order to determine the difference in pixel values ​​of the projection data pair in each column, the electronic device may, for each projection data pair, subtract the pixel values ​​of each pixel point at the same position in the projection data pair, thereby obtaining a second difference image corresponding to each projection data pair. Next, the electronic device may perform any step in step S702 to step S704.

[0111] S702, taking the absolute value of each element in the second difference image to obtain an absolute value image, and calculating the pixel value and value of each column of the absolute value image within the preset range;

[0112] The electronic device can take the absolute value of each element in the second difference image to obtain an absolute value image. If the pixel value and value of the absolute value image in a certain column are large, it means that the difference in pixel values ​​of the projection data corresponding to the absolute value image in the column is large. Correspondingly, if the pixel value and value of the absolute value image in a certain column are small, it means that the difference in pixel values ​​of the projection data corresponding to the absolute value image in the column is small. Therefore, after obtaining the absolute value image, the electronic device can calculate the pixel value and value of each column of the absolute value image within a preset range, that is, execute step S702.

[0113] Assuming that the above process and the process of determining the offset range are expressed in the form of a formula, then each projection data pair can be subtracted and its absolute value can be taken to obtain the absolute value image , , Indicates The absolute value image corresponding to the projection data pair.

[0114] Next, the electronic device can process the image Find the pixel value and value by column, and get the The pixel values ​​and values ​​corresponding to the projection data pairs , the absolute value image The formula for summing the pixel values ​​of a column can be as follows:

[0115] ;

[0116] For the For each pair of projection data, the electronic device can In the The column coordinates corresponding to the minimum value between columns are recorded as .

[0117] The electronics can then determine the predicted range of the detector offset using the following formula :

[0118] ;

[0119] .

[0120] in, is the minimum value among multiple minimum pixel value differences, is the maximum value among multiple minimum pixel value differences, is the pixel size of the detector. In this way, a more accurate offset range can be determined compared to the preset range. .

[0121] S703, calculating the sum of squares of pixel values ​​of each column of the second difference image within the preset range;

[0122] If the square sum of the pixel values ​​of the second difference image in a certain column is large, it means that the pixel value difference of the projection data pair corresponding to the second difference image in the column is large. Correspondingly, if the square sum of the pixel values ​​of the second difference image in a certain column is small, it means that the pixel value difference of the projection data pair corresponding to the second difference image in the column is small. Therefore, after obtaining the second difference image, the electronic device can calculate the square sum of the pixel values ​​of each column of the second difference image within the preset range, that is, execute step S703.

[0123] S704: Calculate the first-order derivative of the pixel value of each column of the second difference image within the preset range.

[0124] Since the first-order derivative can reflect the change of the value, the electronic device can calculate the first-order derivative of the pixel value of each column of the second difference image within the preset range, that is, execute step S704. If the first-order derivative of the pixel value of the second difference image in a certain column is large, it means that the pixel value difference of the projection data pair corresponding to the second difference image in this column is large. Correspondingly, if the first-order derivative of the pixel value of the second difference image in a certain column is small, it means that the pixel value difference of the projection data pair corresponding to the second difference image in this column is small.

[0125] Since steps S702 to S704 only require the pixel value differences of each column of the projection data pair within a preset range, and do not require the pixel value differences of all columns, in step S701, the electronic device may also, for each projection data pair, subtract the pixel values ​​of each pixel point at the same position in the projection data pair only within the preset range to obtain a second difference image corresponding to the preset range.

[0126] It can be seen that in the embodiment of the present application, the electronic device can, for each projection data pair, subtract the pixel values ​​of each pixel point at the same position in the projection data pair to obtain a second difference image; take the absolute value of each element in the second difference image to obtain an absolute value image, and calculate the pixel value and value of each column of the absolute value image within a preset range; or, calculate the square sum of the pixel values ​​of each column of the second difference image within a preset range; or, calculate the first-order derivative of the pixel value of each column of the second difference image within a preset range. In this way, the electronic device can use any of the above three calculation methods to quickly and accurately determine the pixel value difference of the projection data pair within the preset range.

[0127] As an implementation method of the present application, Figure 8 As shown, the step of determining the offset range of the detector based on the column coordinates corresponding to the maximum value, the column coordinates corresponding to the minimum value, and the number of column pixels and the pixel size of the detector may include:

[0128] S801, calculating 1 / 2 of the number of column pixels of the detector to obtain the center column coordinates of the detector;

[0129] Since the column pixels of the detector are evenly distributed on the detector, the electronic device calculates 1 / 2 of the number of the column pixels of the detector to obtain the center column coordinates of the detector.

[0130] S802, multiplying the difference between the column coordinate corresponding to the minimum value and the center column coordinate by the pixel size of the detector to obtain the left boundary of the offset range of the detector;

[0131] The column coordinate corresponding to the minimum value may indicate the position of the detector mapped to the center axis of rotation, which is a position that is relatively close to the actual offset. The electronic device may calculate the difference between the column coordinate corresponding to the minimum value and the center column coordinate, and the difference indicates the offset corresponding to the minimum value in the coordinate system of the projection data. Next, the electronic device may multiply the above difference by the pixel size of the detector, convert the offset corresponding to the minimum value in the coordinate system of the projection data to the world coordinate system, and obtain the left boundary of the offset range of the detector.

[0132] S803: Multiply the difference between the column coordinate corresponding to the maximum value and the center column coordinate by the pixel size of the detector to obtain the right boundary of the offset range of the detector.

[0133] The column coordinate corresponding to the maximum value may indicate the position of the detector mapped to the central axis of rotation, which is a position relatively far from the actual offset. The electronic device may calculate the difference between the column coordinate corresponding to the maximum value and the center column coordinate, and the difference indicates the offset corresponding to the maximum value in the coordinate system of the projection data. Next, the electronic device may multiply the above difference by the pixel size of the detector, convert the offset corresponding to the maximum value in the coordinate system of the projection data to the world coordinate system, and obtain the right boundary of the offset range of the detector.

[0134] It can be seen that in the embodiment of the present application, the electronic device can calculate 1 / 2 of the number of column pixels of the detector to obtain the center column coordinate of the detector; multiply the difference between the column coordinate corresponding to the minimum value and the center column coordinate by the pixel size of the detector to obtain the left boundary of the offset range of the detector; multiply the difference between the column coordinate corresponding to the maximum value and the center column coordinate by the pixel size of the detector to obtain the right boundary of the offset range of the detector. In this way, the offset in the coordinate system of the projection data can be quickly and accurately converted to the world coordinate system, further improving the efficiency of determining the offset of the offset scan.

[0135] As an implementation method of the present application, Fig. 9 As shown, the step of determining the offset of the bias scan according to the fluctuation of the pixel value of the reconstructed image may include:

[0136] S901, determining data to be reconstructed from the projection data;

[0137] Since the projection data is reconstructed using the offset, the fluctuation of the pixel value of the reconstructed image can be used to measure the proximity between the offset corresponding to the reconstructed image and the actual offset. Therefore, the electronic device can determine the data to be reconstructed from the projection data. The data to be reconstructed can specifically be a two-dimensional sine graph or a two-dimensional cosine graph.

[0138] Reconstructing the projection data collected by the row pixels can better reflect the difference between the offset and the actual offset. The data to be reconstructed can be the projection data corresponding to the row pixels of at least one row of the detector.

[0139] In one embodiment, the data to be reconstructed may be projection data corresponding to a row of pixels of a detector. In this case, since only the projection data corresponding to a row of pixels need to be reconstructed, the amount of data to be reconstructed is small, so the amount of calculation in the reconstruction process can be reduced, and the efficiency of determining the offset of the bias scan can be improved. For example, Figure 2 As shown, assuming that the projection data is represented by , then we can determine the The projection data corresponding to the row pixel 201 of the row , that is, the data to be rebuilt.

[0140] In another embodiment, the data to be reconstructed may be projection data corresponding to multiple rows of row pixels of the detector. In this case, since the projection data corresponding to multiple rows of row pixels are reconstructed, the amount of data to be reconstructed is large, thus improving the accuracy of determining the offset of the bias scan.

[0141] S902, reconstructing the data to be reconstructed by using the offset within the offset range, calculating the loss function value corresponding to the reconstructed image, and determining the offset of the offset scan based on the offset corresponding to the maximum loss function value.

[0142] After determining the data to be reconstructed, the electronic device can reconstruct the data to be reconstructed by using the offset within the offset range to obtain a reconstructed image. Next, the electronic device can calculate the loss function value corresponding to the reconstructed image, which is used to characterize the pixel value fluctuation of the reconstructed image.

[0143] If the offset based on which the reconstruction is based is close to the actual offset, the reconstructed image will contain most of the information of the target object, the reconstructed image will contain richer information, and the pixel value fluctuation will be larger. If the offset based on which the reconstruction is based is significantly different from the actual offset, the reconstructed image will lack most of the information of the target object, the reconstructed image will contain less information, and the pixel value fluctuation will be smaller.

[0144] Therefore, the degree of proximity between the offset corresponding to the reconstructed image and the actual offset can be determined by the loss function value corresponding to the reconstructed image, and the electronic device can determine the offset of the biased scan based on the offset corresponding to the maximum loss function value.

[0145] It can be seen that in the embodiment of the present application, the electronic device can determine the data to be reconstructed from the projection data, wherein the data to be reconstructed is the projection data corresponding to the row pixels of at least one row of the detector; reconstruct the data to be reconstructed by the offset within the offset range, and calculate the loss function value corresponding to the reconstructed image, and determine the offset of the biased scan based on the offset corresponding to the maximum loss function value, wherein the loss function value is used to characterize the pixel value fluctuation of the reconstructed image. If the offset based on which the reconstruction is based is close to the actual offset, then the reconstructed image will contain most of the information of the target object, the reconstructed image contains richer information, and the pixel value fluctuation is larger. Therefore, the electronic device can determine the offset of the biased scan based on the offset corresponding to the maximum loss function value. In this way, the offset of the biased scan can be determined quickly and accurately.

[0146] As an implementation method of the present application, Fig.10 As shown, the above-mentioned step of reconstructing the data to be reconstructed by the offset within the offset range, calculating the loss function value corresponding to the reconstructed image, and determining the offset of the offset scan based on the offset corresponding to the maximum loss function value may include:

[0147] S1001, taking the left boundary, the center column of the range, and the right boundary of the offset range as the first offset, the second offset, and the third offset, respectively;

[0148] The offset range is the range for determining the offset of the biased scan, so the binary method can be used to determine the offset of the biased scan in a circular manner. Specifically, after determining the offset range, the electronic device can use the left boundary, the center column of the range, and the right boundary of the offset range as the first offset, the second offset, and the third offset, respectively.

[0149] Assuming the above process is expressed in the form of a formula, the offset range can be determined The left border, range center column, and right border of , as well as , and then the first offset can be determined , the second offset , the third offset .

[0150] S1002, reconstructing the data to be reconstructed according to the current first offset, second offset, and third offset, respectively, to obtain a first reconstructed image, a second reconstructed image, and a third reconstructed image;

[0151] Next, the electronic device can use the current first offset, second offset, and third offset to reconstruct the data to be reconstructed, respectively, to obtain a first reconstructed image, a second reconstructed image, and a third reconstructed image. Specifically, the electronic device can use the offset to correct the data to be reconstructed, the corrected data to be reconstructed is aligned, and then the corrected data to be reconstructed is back-projected to obtain a reconstructed image.

[0152] Assuming that the above process is expressed in the form of a formula, we can use , as well as , treat the reconstruction data separately Reconstruct and obtain the first reconstructed image , the second reconstructed image And the third reconstructed image .

[0153] S1003, calculating the loss function value corresponding to each reconstructed image, and taking the offset corresponding to the maximum loss function value as the current detector offset;

[0154] After obtaining three reconstructed images, the electronic device can calculate the loss function value corresponding to each reconstructed image. If the loss function value corresponding to the reconstructed image is large, it means that the offset corresponding to the reconstructed image is closer to the actual offset. Therefore, the electronic device can use the offset corresponding to the largest loss function value as the current detector offset, which is the offset closest to the actual offset among the current first offset, second offset, and third offset.

[0155] S1004, determining whether the current number of cycles is less than the preset number of cycles, and whether the absolute value of the difference between the first offset and the third offset is greater than the preset difference; if the current number of cycles is less than the preset number of cycles, and the absolute value of the difference between the first offset and the third offset is greater than the preset difference, executing step S1005; if the current number of cycles is not less than the preset number of cycles, or the absolute value of the difference between the first offset and the third offset is not greater than the preset difference, executing step S1006;

[0156] Before using the binary method to determine the offset of the bias scan, a preset number of times and a preset difference can be set in advance. The preset number of times is the maximum number of cycles, and the preset difference is the minimum deviation between the first offset and the third offset. The preset number of times and the preset difference are used to determine the cycle end condition.

[0157] In step S1004, the electronic device can determine whether the current number of cycles is less than the preset number of cycles, and whether the absolute value of the difference between the first offset and the third offset is greater than the preset difference. If the current number of cycles is less than the preset number of cycles, and the absolute value of the difference between the first offset and the third offset is greater than the preset difference, the cycle will continue. If the current number of cycles is not less than the preset number of cycles, or the absolute value of the difference between the first offset and the third offset is not greater than the preset difference, the cycle will end.

[0158] The process of determining the cycle conditions can be expressed in the form of a formula: ,and, In the case of, execute step S1005; ,or, In this case, execute step S1006.

[0159] S1005, determining the two largest loss function values ​​from the loss function values, and using the offsets corresponding to the determined loss function values ​​as the updated first offset and the third offset, respectively, and using the average of the updated first offset and the third offset as the updated second offset;

[0160] If the cycle needs to be continued, the electronic device can determine the two largest loss function values ​​from the three loss function values. The offsets corresponding to the two loss function values ​​are the two offsets closest to the actual offset among the current first offset, second offset and third offset.

[0161] Next, the offsets corresponding to the two determined loss function values ​​can be used as the updated first offset and the third offset, respectively, and the average of the updated first offset and the third offset can be used as the updated second offset. For example, assuming that the first offset, the second offset, and the third offset are 7, 9, and 11, respectively, and the loss function values ​​corresponding to the first reconstructed image and the second reconstructed image are the largest, then the updated first offset and the third offset can be determined to be 7 and 9, respectively, and then the updated second offset can be determined to be the average of the updated first offset and the third offset, which is 8.

[0162] Then, the electronic device may return to step S1002, that is, execute steps S1002 to S1004 again based on the updated first offset, second offset, and third offset.

[0163] S1006, determining an offset of the bias scan based on the current detector offset.

[0164] When the cycle ends, the electronic device can determine the offset of the bias scan based on the current detector offset. Assuming that the current detector offset is offset, the electronic device can determine the offset of the bias scan based on the current detector offset offset.

[0165] It can be seen that in the embodiment of the present application, the electronic device can use the dichotomy method to continuously determine the updated offset in the offset range of the detector based on the offset that makes the loss function value take the maximum value in a cyclic manner, so that the determined current detector offset constantly approaches the actual offset. In this way, the calculation process is simple, and the current detector offset can be determined quickly and accurately, and then the offset of the bias scan can be determined quickly and accurately.

[0166] As an implementation method of the present application, Fig.11 As shown, the above step of calculating the loss function value corresponding to each reconstructed image may include:

[0167] S1101, for each reconstructed image, calculating the mean pixel value of all pixel points included in the reconstructed image;

[0168] The electronic device may calculate the average pixel value of all pixels included in each reconstructed image. In one embodiment, the electronic device may use the following formula to calculate the average pixel value: :

[0169] ;

[0170] in, To reconstruct the image The row height, To reconstruct the image The column width, Represents the reconstructed image Located in The pixel value of the pixel.

[0171] S1102, determining a loss function value corresponding to the reconstructed image according to a difference between a pixel value of each pixel point included in the reconstructed image and the pixel value mean.

[0172] After determining the mean pixel value corresponding to each reconstructed image, the electronic device can determine the loss function value corresponding to the reconstructed image according to the difference between the pixel value of each pixel point included in the reconstructed image and the mean pixel value according to the pre-constructed loss function. In this way, the loss function value can represent the fluctuation of the pixel value of the reconstructed image.

[0173] As long as the loss function can characterize the difference between the pixel value of each pixel and the mean pixel value, the specific form of the loss function is not limited here.

[0174] It can be seen that in the embodiment of the present application, the electronic device can calculate the average pixel value of all pixels included in each reconstructed image; and determine the loss function value corresponding to the reconstructed image according to the difference between the pixel value of each pixel included in the reconstructed image and the average pixel value. In this way, the loss function value can represent the fluctuation of the pixel value of the reconstructed image, and then the detector offset closest to the actual offset can be determined based on the size of the loss function value.

[0175] As an implementation manner of an embodiment of the present application, the step of determining the loss function value corresponding to the reconstructed image according to the difference between the pixel value of each pixel point included in the reconstructed image and the pixel value mean may include:

[0176] Based on the average pixel value of the reconstructed image, the loss function value corresponding to the reconstructed image is calculated using the following formula: :

[0177] .

[0178] The above formula can be regarded as the variance of each pixel value in the reconstructed image. The variance can represent the fluctuation of the data. Therefore, the loss function value calculated based on this formula can characterize the fluctuation of the pixel value of the reconstructed image. , the second reconstructed image And the third reconstructed image , respectively calculate the loss function value , as well as .

[0179] It can be seen that in the embodiment of the present application, the electronic device can calculate the loss function value based on the above formula, and the loss function value can characterize the fluctuation of the pixel value of the reconstructed image. In this way, the loss function value corresponding to each reconstructed image can be calculated quickly and accurately, and the loss function value can better reflect the fluctuation of the pixel value of the reconstructed image, thereby improving the accuracy of determining the offset of the bias scan.

[0180] As an implementation of an embodiment of the present application, the step of determining the offset of the bias scan based on the current detector offset may include:

[0181] If the scanning mode of the bias scanning is a detector bias scanning, determining the offset of the detector to be a current detector offset;

[0182] If the scanning mode of the bias scanning is turntable bias scanning, the multiplication value between the current detector offset and the proportional coefficient is used as the turntable offset. The proportional coefficient may be a ratio between a first distance and a second distance, the first distance being the distance between the ray source and the target object, and the second distance being the distance between the ray source and the detector.

[0183] In the first way, assuming that the scanning mode of the offset scanning is the detector offset scanning, that is, the detector in the CT scanning system is offset, then the electronic device can determine that the offset of the detector is the current detector offset.

[0184] In the second method, it is assumed that the scanning mode of the offset scanning is turntable offset scanning, that is, the offset occurs on the turntable in the CT scanning system, the target object is located on the turntable, and the center axis of the turntable in the vertical direction is the rotation center axis. In this case, since the ratio between the offset of the turntable and the offset of the detector is the ratio of the distance between the ray source and the target object to the distance between the ray source and the detector, the electronic device can use the multiplication value between the current detector offset and the proportional coefficient as the offset of the turntable, which is also the offset of the center of the turntable.

[0185] Assuming that the second method is expressed in the form of a formula, the offset of the turntable can be calculated using the following formula:

[0186] ;

[0187] in, is the distance between the ray source and the target object, is the distance between the radiation source and the detector.

[0188] It can be seen that in the embodiment of the present application, if the scanning mode of the bias scanning is the detector bias scanning, the electronic device can determine the offset of the detector as the current detector offset; if the scanning mode of the bias scanning is the turntable bias scanning, the electronic device can use the multiplication value between the current detector offset and the proportional coefficient as the offset of the turntable. In this way, the detector offset can be converted based on the scanning mode of the bias scanning, and not only the detector offset can be accurately determined in the scanning mode of the detector bias scanning, but also the turntable offset can be accurately determined in the scanning mode of the turntable bias scanning.

[0189] As an implementation method of the present application, a flow chart for determining the detector offset can be as follows: Fig.12 As shown, the following steps may be specifically included:

[0190] S1201, obtaining the data to be reconstructed corresponding to the row pixels of a row of the detector;

[0191] The electronic device can obtain the to-be-reconstructed data corresponding to the row pixels of a row of the detector from the projection data, thereby reducing the amount of subsequent calculations and improving the efficiency of determining the detector offset.

[0192] S1202, determining a first offset, a second offset, and a third offset according to an offset range of the detector;

[0193] The electronic device may determine the left boundary, the center column of the range, and the right boundary of the offset range as the initial first offset, the second offset, and the third offset, respectively.

[0194] S1203, using the current first offset, second offset, and third offset, respectively reconstructing the data to be reconstructed to obtain a first reconstructed image, a second reconstructed image, and a third reconstructed image;

[0195] The electronic device can use the current first offset, second offset and third offset to reconstruct the data to be reconstructed, respectively, to obtain a first reconstructed image, a second reconstructed image and a third reconstructed image. The specific reconstruction method has been introduced in the above embodiment and will not be repeated here.

[0196] S1204, calculating the loss function value corresponding to each reconstructed image to obtain a first loss function value, a second loss function value, and a third loss function value;

[0197] For each reconstructed image, the electronic device can calculate the loss function value corresponding to the reconstructed image to obtain a first loss function value corresponding to the first reconstructed image, a second loss function value corresponding to the second reconstructed image, and a third loss function value corresponding to the third reconstructed image.

[0198] S1205, comparing multiple loss function values, and recording the offset corresponding to the reconstructed image corresponding to the maximum value as the current detector offset;

[0199] Since the larger the loss function value, the closer the offset of the reconstructed image corresponding to the loss function value is to the actual offset, the electronic device can compare multiple loss function values ​​and record the offset corresponding to the reconstructed image corresponding to the maximum value as the current detector offset.

[0200] S1206, determining whether the current number of cycles is not less than a preset number, or whether the absolute value of the difference between the first offset and the third offset is not greater than a preset difference; if not, executing step S1207; if yes, executing step S1208;

[0201] The electronic device can determine whether the current condition satisfies the loop termination condition, that is, whether the current number of loops is not less than a preset number, or whether the absolute value of the difference between the first offset and the third offset is not greater than a preset difference.

[0202] S1207, determining the offsets corresponding to the reconstructed images corresponding to two larger loss function values ​​among the multiple loss function values ​​as the updated first offset and third offset;

[0203] If the above judgment result is no, it means that the current number of loops is less than the preset number, and the absolute value of the difference between the first offset and the third offset is greater than the preset difference, then the electronic device can determine the offsets corresponding to the reconstructed images corresponding to the two larger loss function values ​​among the multiple loss function values ​​as the updated first offset and the third offset, and then use the average of the updated first offset and the second offset as the updated second offset.

[0204] Next, the electronic device may return to step S1202.

[0205] S1208, determining that the detector offset is the current detector offset.

[0206] If the above judgment result is yes, it means that the current number of cycles is not less than the preset number, or the absolute value of the difference between the first offset and the third offset is not greater than the preset difference, then the electronic device can determine that the detector offset is the current detector offset.

[0207] As an implementation method of the present application, a flow chart for determining the offset of the bias scan can be as follows: Fig.13 As shown, the following steps may be specifically included:

[0208] S1301, determining relevant parameters of the cone beam CT scanning system;

[0209] The electronic device can determine relevant parameters of the cone beam CT scanning system, wherein the relevant parameters may include the distance between the ray source and the detector, the distance between the ray source and the rotation center axis, the scanning angle, the scanning angle interval, the voltage and the current.

[0210] S1302, acquiring projection data obtained by offset scanning by a cone beam CT scanning system;

[0211] The electronic device can obtain projection data obtained by the cone-beam CT scanning system performing offset scanning on the target object, and the projection data is the original projection data.

[0212] S1303, selecting any two projection data with a projection angle difference of 180 degrees from the projection data, and determining a predicted position of the detector offset by performing data processing and analysis on the selected projection data;

[0213] The electronic device can select any two projection data with a projection angle difference of 180 degrees from the projection data to obtain a projection data pair. Then, by processing and analyzing the projection data pair, the approximate position of the detector offset is determined. Specifically, the electronic device can determine the predicted position of the rotation center axis mapping in the detector based on the difference in pixel values ​​of the projection data pair in each column in the projection data.

[0214] S1304, selecting a plurality of pairs of projection data with a projection angle difference of 180 degrees from the original projection data, and determining the offset range of the detector offset by performing data processing and analysis on the selected projection data;

[0215] The electronic device can select multiple pairs of projection data with a projection angle difference of 180 degrees from the original projection data to obtain multiple projection data pairs. Next, the multiple projection data pairs can be processed and analyzed to determine the precise range of the detector offset. Specifically, the electronic device can determine the detector offset range based on the pixel value difference of the projection data pair within a preset range.

[0216] S1305, obtaining projection data corresponding to row pixels of a row of the detector, and determining the detector offset by analyzing the reconstructed image using a binary method;

[0217] The electronic device can use the projection data corresponding to the row pixels of a row of the detector as the data to be reconstructed. Next, the offset of the detector can be determined from the above offset range using the dichotomy method. Specifically, the data to be reconstructed can be reconstructed using the offset within the offset range to obtain a reconstructed image, and then the detector offset can be determined based on the pixel value fluctuation represented by the loss function value corresponding to the reconstructed image.

[0218] S1306, determine the scanning mode of the bias scanning; if the scanning mode is the detector bias scanning, execute step S1307; if the scanning mode is the turntable bias scanning, execute step S1308.

[0219] If the scanning mode of the bias scanning is different, the way of determining the offset of the bias scanning will also be different, so the electronic device can determine the scanning mode of the bias scanning. The scanning mode can include detector bias scanning and turntable bias scanning.

[0220] S1307, determining that the detector offset is the current detector offset;

[0221] If the scan mode of the bias scan is a detector bias scan, the electronics may determine the detector offset directly.

[0222] S1308, taking the multiplication value between the detector offset and the proportional coefficient as the offset of the turntable.

[0223] If the scanning mode of the bias scanning is the turntable bias scanning, the electronic device may use the multiplication value between the detector offset and the proportionality coefficient as the turntable offset, wherein the proportionality coefficient is the ratio of the distance between the ray source and the target object to the distance between the ray source and the detector.

[0224] Corresponding to the above-mentioned method for determining a biased scanning offset, the embodiment of the present application further provides a device for determining a biased scanning offset. The following is an introduction to a device for determining a biased scanning offset provided in the embodiment of the present application.

[0225] like Fig.14 As shown, a device for determining a bias scanning offset is applied to a bias scanning system, wherein the bias scanning system includes a ray source, a detector, and a turntable for carrying a target object, wherein the turntable is located between the ray source and the detector and can rotate around a rotation center axis, and the device includes:

[0226] The data acquisition module 1401 is used to acquire projection data obtained by performing offset scanning on the target object;

[0227] A predicted position determination module 1402 is used to determine the predicted position of the rotation center axis mapped in the detector based on the difference in pixel values ​​of a projection data pair in each column in the projection data, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than a preset threshold;

[0228] An offset range determination module 1403, configured to determine an offset range of the detector according to a difference in pixel values ​​of the projection data within a preset range, wherein the preset range is a preset number of columns of data in the projection data including the predicted position;

[0229] The offset determination module 1404 is used to determine the offset of the offset scan according to the fluctuation of the pixel value of the reconstructed image, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range.

[0230] It can be seen that in the embodiment of the present application, the electronic device can obtain the projection data obtained by bias scanning the target object; based on the difference in pixel values ​​of the projection data pair in each column in the projection data, determine the predicted position of the rotation center axis mapping in the detector, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than the preset threshold; according to the difference in pixel values ​​of the projection data pair within a preset range, determine the offset range of the detector, wherein the preset range is a preset number of columns of data including the predicted position in the projection data; according to the fluctuation of the pixel values ​​of the reconstructed image, determine the offset of the bias scanning, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range. If the angle of rotation of the target object is close to 180 degrees, then the two projection data corresponding to the rotation before and after can be approximated to the half and the other half of the target object, respectively. Since these two parts have an overlapping part on the vertical center axis of the target object, and have a large difference on both sides of the vertical center axis, and the vertical center axis coincides with the rotation center axis, the pixel values ​​corresponding to the two projection data near the rotation center axis have a small difference, and the pixel values ​​corresponding to both sides near the rotation center axis have a large difference. Based on this characteristic, the electronic device can determine the predicted position of the rotation center axis mapping in the detector, that is, the approximate position of the detector offset, based on the difference in pixel values ​​of the projection data pairs in each column in the projection data. Furthermore, the offset range of the detector can be determined based on the difference in pixel values ​​of the projection data pairs within a preset range. Next, the projection data can be reconstructed based on the offset within the offset range to obtain a reconstructed image. Assuming that the offset based on which the reconstruction is based is close to the actual offset, the reconstructed image will contain most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be large. Therefore, the electronic device can determine the offset of the offset scan based on the pixel value fluctuation of the reconstructed image. Since a relatively accurate offset of the bias scan can be determined by directly analyzing and processing the projection data without using a correction phantom, the process of determining the offset of the bias scan can be simplified and the efficiency of determining the offset of the bias scan can be improved.

[0231] As an implementation of the embodiment of the present application, the above-mentioned predicted position determination module 1402 may include:

[0232] A projection data pair determination submodule, configured to determine, from the projection data, a projection data pair whose projection angle difference is a preset value according to the projection angle of the projection data;

[0233] A column coordinate determination submodule, used to calculate the pixel value difference of the projection data pair in each column, and determine the column coordinate corresponding to the maximum pixel value difference and the column coordinate corresponding to the minimum pixel value difference;

[0234] The predicted position determination submodule is used to determine the mean value of the determined column coordinates as the predicted position of the rotation center axis mapped in the detector.

[0235] As an implementation of the embodiment of the present application, the column coordinate determination submodule may include:

[0236] A difference image determining unit, configured to subtract pixel values ​​of pixels at the same position in each projection data pair to obtain a first difference image;

[0237] The difference determination unit is used to calculate the mean value of the pixel values ​​in each column of the first difference image; or calculate the sum of the pixel values ​​in each column of the first difference image.

[0238] As an implementation of the embodiment of the present application, the above-mentioned offset range determination module 1403 may include:

[0239] A preset range determination submodule is used to determine the left boundary of the range to the left and the right boundary of the range to the right with the predicted position as the center column of the range, so as to obtain a preset range including a preset number of columns of data;

[0240] The offset range determination submodule is used to determine the offset range of the detector according to the difference in pixel values ​​of each column of a plurality of projection data pairs within the preset range, as well as the number of column pixels and pixel size of the detector.

[0241] As an implementation of an embodiment of the present application, the above-mentioned offset range determination submodule may include:

[0242] a projection data pair determining unit, configured to determine, from the projection data, a plurality of projection data pairs whose projection angle differences are preset values ​​according to the projection angles of the projection data;

[0243] a pixel value difference determination unit, configured to calculate the pixel value difference of each column of each projection data pair within the preset range, and determine the minimum pixel value difference corresponding to each projection data pair;

[0244] A maximum value determining unit, used for determining a maximum value and a minimum value from a plurality of minimum pixel value differences;

[0245] The offset range determining unit is used to determine the offset range of the detector based on the column coordinate corresponding to the maximum value, the column coordinate corresponding to the minimum value, and the number of column pixels and the pixel size of the detector.

[0246] As an implementation manner of the embodiment of the present application, the above-mentioned pixel value difference determination unit may include:

[0247] A difference image determination subunit is used for subtracting the pixel values ​​of each pixel point at the same position in each projection data pair from each other to obtain a second difference image;

[0248] The difference determination subunit is used to take the absolute value of each element in the second difference image to obtain an absolute value image, and calculate the pixel value and value of each column of the absolute value image within the preset range; or, calculate the square sum of the pixel values ​​of each column of the second difference image within the preset range; or, calculate the first-order derivative of the pixel value of each column of the second difference image within the preset range.

[0249] As an implementation of the embodiment of the present application, the above-mentioned offset range determination unit may include:

[0250] A center column coordinate calculation subunit, used for calculating 1 / 2 of the number of column pixels of the detector to obtain the center column coordinate of the detector;

[0251] a left boundary determination subunit, configured to multiply the difference between the column coordinate corresponding to the minimum value and the center column coordinate by the pixel size of the detector to obtain the left boundary of the offset range of the detector;

[0252] The right boundary determination subunit is used to multiply the difference between the column coordinate corresponding to the maximum value and the center column coordinate by the pixel size of the detector to obtain the right boundary of the offset range of the detector.

[0253] As an implementation of the embodiment of the present application, the above-mentioned offset determination module 1404 may include:

[0254] A submodule for determining data to be reconstructed, used to determine data to be reconstructed from the projection data, wherein the data to be reconstructed is projection data corresponding to row pixels of at least one row of the detector;

[0255] The reconstruction submodule is used to reconstruct the data to be reconstructed through the offset within the offset range, and calculate the loss function value corresponding to the reconstructed image, and determine the offset of the biased scan based on the offset corresponding to the maximum loss function value, wherein the loss function value is used to characterize the pixel value fluctuation of the reconstructed image.

[0256] As an implementation of an embodiment of the present application, the above-mentioned reconstruction submodule may include:

[0257] an initial offset determination unit, configured to use the left boundary, the center column of the range, and the right boundary of the offset range as the first offset, the second offset, and the third offset, respectively;

[0258] a reconstruction unit, configured to reconstruct the data to be reconstructed according to the current first offset, the second offset, and the third offset, respectively, to obtain a first reconstructed image, a second reconstructed image, and a third reconstructed image;

[0259] A loss function value calculation unit, used to calculate the loss function value corresponding to each reconstructed image, and use the offset corresponding to the maximum loss function value as the current detector offset;

[0260] a cycle condition determination unit, configured to determine whether the current number of cycles is less than a preset number, and whether the absolute value of the difference between the first offset and the third offset is greater than a preset difference;

[0261] an offset updating unit, configured to determine the two largest loss function values ​​from the loss function values ​​if the current number of cycles is less than the preset number of cycles and the absolute value of the difference between the first offset and the third offset is greater than the preset difference, and use the offsets corresponding to the determined loss function values ​​as the updated first offset and the third offset, respectively, and use the average of the updated first offset and the third offset as the updated second offset;

[0262] a returning unit, configured to return the step of reconstructing the data to be reconstructed according to the current first offset, the second offset, and the third offset, respectively, to obtain a first reconstructed image, a second reconstructed image, and a third reconstructed image;

[0263] The offset determination unit is used to determine the offset of the bias scan based on the current detector offset if the current cycle number is not less than the preset number, or the absolute value of the difference between the first offset and the third offset is not greater than the preset difference.

[0264] As an implementation of an embodiment of the present application, the above-mentioned loss function value calculation unit may include:

[0265] A mean value calculation subunit, used for calculating, for each reconstructed image, a mean value of pixel values ​​of all pixel points included in the reconstructed image;

[0266] The loss function value calculation subunit is used to determine the loss function value corresponding to the reconstructed image according to the difference between the pixel value of each pixel point included in the reconstructed image and the pixel value mean.

[0267] As an implementation of an embodiment of the present application, the above-mentioned loss function value calculation subunit may include:

[0268] The formula calculation subunit is used to calculate the loss function value corresponding to the reconstructed image based on the average pixel value of the reconstructed image using the following formula :

[0269] ;

[0270] in, is the average pixel value, is the row height of the reconstructed image, The column width for this reconstructed image.

[0271] As an implementation of an embodiment of the present application, the above-mentioned offset determination unit may include:

[0272] An offset determination subunit is used to use the multiplication value between the current detector offset and the proportional coefficient as the offset of the turntable if the scanning mode of the offset scanning is the turntable offset scanning, wherein the proportional coefficient is the ratio between the first distance and the second distance, the first distance is the distance between the ray source and the target object, and the second distance is the distance between the ray source and the detector.

[0273] The present application also provides an electronic device, such as Fig.15 As shown, including:

[0274] Memory 1501, used for storing computer programs;

[0275] The processor 1502 is used to implement the method for determining the bias scanning offset described in any of the above embodiments when executing the program stored in the memory 1501.

[0276] In addition, the electronic device may further include a communication bus and / or a communication interface, and the processor 1502, the communication interface, and the memory 1501 communicate with each other via the communication bus.

[0277] It can be seen that in the embodiment of the present application, the electronic device can obtain the projection data obtained by bias scanning the target object; based on the difference in pixel values ​​of the projection data pair in each column in the projection data, determine the predicted position of the rotation center axis mapping in the detector, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than the preset threshold; according to the difference in pixel values ​​of the projection data pair within a preset range, determine the offset range of the detector, wherein the preset range is a preset number of columns of data including the predicted position in the projection data; according to the fluctuation of the pixel values ​​of the reconstructed image, determine the offset of the bias scanning, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range. If the angle of rotation of the target object is close to 180 degrees, then the two projection data corresponding to the rotation before and after can be approximated to the half and the other half of the target object, respectively. Since these two parts have an overlapping part on the vertical center axis of the target object, and have a large difference on both sides of the vertical center axis, and the vertical center axis coincides with the rotation center axis, the pixel values ​​corresponding to the two projection data near the rotation center axis have a small difference, and the pixel values ​​corresponding to both sides near the rotation center axis have a large difference. Based on this characteristic, the electronic device can determine the predicted position of the rotation center axis mapping in the detector, that is, the approximate position of the detector offset, based on the difference in pixel values ​​of the projection data pairs in each column in the projection data. Furthermore, the offset range of the detector can be determined based on the difference in pixel values ​​of the projection data pairs within a preset range. Next, the projection data can be reconstructed based on the offset within the offset range to obtain a reconstructed image. Assuming that the offset based on which the reconstruction is based is close to the actual offset, the reconstructed image will contain most of the information of the target object, and the pixel value fluctuation of the reconstructed image will be large. Therefore, the electronic device can determine the offset of the offset scan based on the pixel value fluctuation of the reconstructed image. Since a relatively accurate offset of the bias scan can be determined by directly analyzing and processing the projection data without using a correction phantom, the process of determining the offset of the bias scan can be simplified and the efficiency of determining the offset of the bias scan can be improved.

[0278] The communication bus mentioned in the above electronic device can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The communication bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus.

[0279] The communication interface is used for communication between the above electronic device and other devices.

[0280] The memory may include a random access memory (RAM) or a non-volatile memory (NVM), such as at least one disk memory. Optionally, the memory may also be at least one storage device located away from the aforementioned processor.

[0281] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0282] In another embodiment provided in the present application, a computer-readable storage medium is provided, in which a computer program is stored. When the computer program is executed by a processor, the steps of any of the above-mentioned methods for determining the bias scanning offset are implemented.

[0283] In another embodiment provided in the present application, a computer program product including instructions is also provided. When the computer program product is run on a computer, the computer executes any method for determining the bias scanning offset in the above embodiments.

[0284] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a solid-state hard disk (SSD), etc.

[0285] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0286] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device, electronic device, computer-readable storage medium, and computer program product embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0287] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A method for determining a bias scanning offset, characterized in that: The method is applied to a bias scanning system, which is a detector bias scanning system or a turntable bias scanning system. The bias scanning system includes a ray source, a detector, and a turntable for carrying a target object. The turntable is located between the ray source and the detector and can rotate around a rotation center axis. The target point position of the ray source, the central axis of the detector, and the rotation center axis of the turntable are not collinear. The method includes: Acquire projection data obtained by offset scanning of the target object; Determine the predicted position of the rotation center axis mapped in the detector based on the difference in pixel values ​​of the projection data pair in each column in the projection data, wherein the projection data pair is two projection data with a projection angle difference of a preset value, and the difference between the preset value and 180 degrees is less than a preset threshold; Determining the offset range of the detector according to the difference in pixel values ​​of the projection data within a preset range, wherein the preset range is a preset number of columns of data in the projection data including the predicted position; The offset of the offset scan is determined according to the fluctuation of the pixel value of the reconstructed image, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range.

2. The method according to claim 1, characterized in that The step of determining the predicted position of the rotation center axis mapped in the detector based on the pixel value difference of the projection data pairs in each column in the projection data comprises: According to the projection angle of the projection data, determining a projection data pair whose projection angle difference is a preset value from the projection data; Calculating the pixel value difference of the projection data pair in each column, and determining the column coordinate corresponding to the maximum pixel value difference and the column coordinate corresponding to the minimum pixel value difference; The mean of the determined column coordinates is determined as the predicted position of the rotation center axis mapped in the detector.

3. The method according to claim 2, characterized in that The step of calculating the difference in pixel values ​​of the projection data pair in each column comprises: Subtracting pixel values ​​of each pixel point at the same position in the projection data pair to obtain a first difference image; Calculate the mean value of the pixel values ​​in each column of the first difference image; or calculate the sum of the pixel values ​​in each column of the first difference image.

4. The method according to claim 1, characterized in that: The step of determining the offset range of the detector according to the pixel value difference of the projection data within a preset range comprises: Taking the predicted position as the center column of the range, determining the left boundary of the range to the left, and determining the right boundary of the range to the right, to obtain a preset range including a preset number of columns of data; The offset range of the detector is determined according to the difference in pixel values ​​of each column of a plurality of projection data within the preset range, as well as the number of column pixels and pixel size of the detector.

5. The method according to claim 4, characterized in that The step of determining the offset range of the detector according to the difference in pixel values ​​of each column within the preset range for a plurality of projection data pairs, and the number of column pixels and pixel size of the detector comprises: According to the projection angles of the projection data, determining from the projection data a plurality of projection data pairs whose projection angle differences are preset values; Calculating the pixel value difference of each column of each projection data pair within the preset range, and determining the minimum pixel value difference corresponding to each projection data pair; From the plurality of minimum pixel value differences, determining a maximum value and a minimum value; The offset range of the detector is determined based on the column coordinate corresponding to the maximum value, the column coordinate corresponding to the minimum value, and the number of column pixels and the pixel size of the detector.

6. The method according to claim 5, characterized in that The step of calculating the pixel value difference of each column of each projection data pair within the preset range comprises: For each projection data pair, subtract the pixel values ​​of each pixel point at the same position in the projection data pair to obtain a second difference image; Take the absolute value of each element in the second difference image to obtain an absolute value image, and calculate the sum of pixel values ​​of each column of the absolute value image within the preset range; or, calculate the sum of squares of pixel values ​​of each column of the second difference image within the preset range; or, calculate the first-order derivative of the pixel values ​​of each column of the second difference image within the preset range.

7. The method according to claim 5, characterized in that The step of determining the offset range of the detector based on the column coordinates corresponding to the maximum value, the column coordinates corresponding to the minimum value, and the number of column pixels and the pixel size of the detector comprises: Calculate 1 / 2 of the number of column pixels of the detector to obtain the center column coordinates of the detector; Multiplying the difference between the column coordinate corresponding to the minimum value and the center column coordinate by the pixel size of the detector to obtain the left boundary of the offset range of the detector; The difference between the column coordinate corresponding to the maximum value and the center column coordinate is multiplied by the pixel size of the detector to obtain the right boundary of the offset range of the detector.

8. The method according to any one of claims 1 to 7, characterized in that: The step of determining the offset of the bias scan according to the fluctuation of the pixel value of the reconstructed image comprises: Determine data to be reconstructed from the projection data, wherein the data to be reconstructed is projection data corresponding to row pixels of at least one row of the detector; The data to be reconstructed is reconstructed by the offset within the offset range, and the loss function value corresponding to the reconstructed image is calculated, and the offset of the bias scan is determined based on the offset corresponding to the maximum loss function value, wherein the loss function value is used to characterize the pixel value fluctuation of the reconstructed image.

9. The method according to claim 8, characterized in that The step of reconstructing the data to be reconstructed by the offset within the offset range, calculating the loss function value corresponding to the reconstructed image, and determining the offset of the offset scan based on the offset corresponding to the maximum loss function value includes: The left boundary, the center column of the range and the right boundary of the offset range are used as the first offset, the second offset and the third offset respectively; Reconstructing the data to be reconstructed according to the current first offset, second offset and third offset respectively to obtain a first reconstructed image, a second reconstructed image and a third reconstructed image; Calculate the loss function value corresponding to each reconstructed image, and use the offset corresponding to the maximum loss function value as the current detector offset; Determine whether the current number of cycles is less than a preset number, and whether the absolute value of the difference between the first offset and the third offset is greater than a preset difference; If the current number of cycles is less than the preset number of times, and the absolute value of the difference between the first offset and the third offset is greater than the preset difference, determine the two largest loss function values ​​from the loss function values, and use the offsets corresponding to the determined loss function values ​​as the updated first offset and the third offset, respectively, and use the average of the updated first offset and the third offset as the updated second offset; Returning to the step of reconstructing the data to be reconstructed according to the current first offset, second offset and third offset, respectively, to obtain a first reconstructed image, a second reconstructed image and a third reconstructed image; If the current number of cycles is not less than the preset number, or the absolute value of the difference between the first offset and the third offset is not greater than the preset difference, the offset of the bias scan is determined based on the current detector offset.

10. The method according to claim 9, characterized in that The step of calculating the loss function value corresponding to each reconstructed image comprises: For each reconstructed image, calculating the mean pixel value of all pixel points included in the reconstructed image; The loss function value corresponding to the reconstructed image is determined according to the difference between the pixel value of each pixel point included in the reconstructed image and the pixel value mean.

11. The method according to claim 10, characterized in that The step of determining the loss function value corresponding to the reconstructed image according to the difference between the pixel value of each pixel point included in the reconstructed image and the pixel value mean comprises: Based on the average pixel value of the reconstructed image, the loss function value corresponding to the reconstructed image is calculated using the following formula: : ； in, is the average pixel value, is the row height of the reconstructed image, The column width for this reconstructed image.

12. The method according to claim 9, characterized in that The step of determining the offset of the bias scan based on the current detector offset comprises: If the scanning mode of the bias scanning is turntable bias scanning, the multiplication value between the current detector offset and the proportional coefficient is used as the offset of the turntable, wherein the proportional coefficient is the ratio between the first distance and the second distance, the first distance is the distance between the ray source and the target object, and the second distance is the distance between the ray source and the detector.

13. A device for determining a bias scanning offset, characterized in that: The device is applied to a bias scanning system, which is a detector bias scanning system or a turntable bias scanning system. The bias scanning system includes a ray source, a detector, and a turntable for carrying a target object. The turntable is located between the ray source and the detector and can rotate around a rotation center axis. The target position of the ray source, the central axis of the detector, and the rotation center axis of the turntable are not collinear. The device includes: A data acquisition module, used to acquire projection data obtained by offset scanning of a target object; a predicted position determination module, configured to determine a predicted position of the rotation center axis mapped in the detector based on a difference in pixel values ​​of a projection data pair in each column of the projection data, wherein the projection data pair is two projection data having a projection angle difference of a preset value, and a difference between the preset value and 180 degrees is less than a preset threshold; An offset range determination module, configured to determine an offset range of the detector according to a difference in pixel values ​​of the projection data within a preset range, wherein the preset range is a preset number of columns of data in the projection data including the predicted position; The offset determination module is used to determine the offset of the offset scan according to the fluctuation of the pixel value of the reconstructed image, wherein the reconstructed image is an image obtained by reconstructing the projection data based on the offset within the offset range.

14. An electronic device, characterized in that: include: Memory, used to store computer programs; A processor, for implementing any of the methods described in claims 1-12 when executing a program stored in a memory.

15. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 12 is implemented.

Images