Data correction method, bad channel data correction method for multi-source CT system, and multi-source computed tomography system

Abstract

A data correction method, a bad channel data correction method for a multi-source CT system, and a multi-source computed tomography system. The data correction method comprises: determining the position and a distribution of a bad channel in a first projection of a first bulb tube detector combination (S1); when the distribution of the bad channel does not meet a preset condition, determining opposite projection data corresponding to the bad channel in a second projection of a second bulb tube detector combination (S2); and using the opposite projection data to correct projection data of the bad channel (3). Thus, the image quality is ensured, the yield of detectors is improved, and the system costs are reduced.

Description

Data correction method, bad channel data correction method of multi-source CT system, and multi-source computed tomography system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure is based on and claims priority to an application with CN application number 202311286387.7 and filing date October 31, 2023. The disclosure content of this CN application is hereby incorporated into this disclosure as a whole. Technical Field

[0003] The present disclosure belongs to the application field of X-ray medical imaging equipment, and specifically provides a data correction method, a bad channel data correction method for a multi-source CT system, and a multi-source computed tomography system. Background Art

[0004] To obtain high-quality reconstructed images, CT (computed tomography) systems require preprocessing of the collected projection data. This involves determining the accuracy and reliability of the signals read from the CT detector, as well as the performance of each detector channel (also known as a pixel). If the data is abnormal, and the number of abnormalities is within a certain range, the data from the abnormal detector channels must be corrected. Completely discarding modules containing bad channels will significantly reduce detector yield and increase costs.

[0005] As the size of CT detector units becomes smaller and smaller, the number of rows increases, and the integration of detectors and data acquisition systems becomes higher and higher, these factors lead to more and more cases of bad channels in detectors.

[0006] In photon counting CT systems, in addition to the above factors, flaws and defects in the detector's semiconductor direct conversion materials also lead to a significantly higher proportion of bad channels than in indirect conversion detectors.

[0007] In traditional single-source CT systems, bad channels can be detected by the average response value of the detector module (CN112656435A). Correction is generally performed by replacing the bad channel data with the data difference of adjacent channels (CN104939859A), or by rotating the projection data of other channels 180 degrees (CN201410428793.7) to replace the bad channel data.

[0008] However, the closer to the center of rotation (central channel), the more limited the reconstruction data source. At the center of rotation, the reconstruction data comes almost entirely from the central channel. Furthermore, the human body is complex and the scanned area is not uniform or slowly changing. Therefore, interpolation repair of detector data near the central channel is prone to artifacts.

[0009] Therefore, traditional CT systems have strict requirements for the distribution of bad channels. For example, there cannot be adjacent bad channels; there cannot be bad channels within a 16cm field of view; and there cannot be bad channels in the outermost slices of the scan. Data correction for bad channels is therefore also subject to these restrictions. Summary of the Invention

[0010] In order to address the defects and deficiencies in the above-mentioned related technologies, the present disclosure provides a bad channel data correction method for a multi-source CT system for ensuring image quality, improving detector yield, and reducing system cost.

[0011] According to one aspect of the present disclosure, a data correction method for a multi-source computed tomography (CT) system is provided, comprising: determining the location and distribution of bad channels in a first projection of a first tube-detector assembly; determining opposite projection data corresponding to the bad channels in a second projection of a second tube-detector assembly if the distribution of the bad channels does not meet a preset condition; and correcting projection data of the bad channels using the opposite projection data.

[0012] According to another aspect of the present disclosure, a method for correcting bad channel data of a multi-source CT system is provided, comprising the following steps:

[0013] Step 1. Collect data of different tube currents for the system multiple times and determine the location and distribution of bad channels through linearity inspection;

[0014] Step 2. If the distribution of bad channels satisfies:

[0015] a) Adjacent channels are all good channels;

[0016] b) The bad channel is not within a certain field of view;

[0017] c) The bad channel is not in the outermost row of several detector acquisition modes supported by the system;

[0018] The data of the target bad channel is corrected by interpolating the data of the current sampling peripheral channels of the current detector;

[0019] Step 3. If the distribution of bad channels does not meet the conditions of Step 2, check whether the previous or next tube + detector combination can provide opposite projection data to correct the data of the target bad channel according to the following scheme;

[0020] Step 4. If the current bad channel can be corrected using the previous or next set of tube + detector subtending projection data, the data is corrected and the subsequent preprocessing process begins, selecting subtending projection data based on the number of tubes + detectors in the CT system.

[0021] Step 5. After determining the corresponding tube + detector combination and sampling angle, calculate the corresponding channel based on the angle between the channel and the central channel. Assuming that the channel interval is dβ degrees, the corresponding channel is ch = -β / dβ. If ch is a non-integer, the corresponding projection value can be calculated using linear interpolation.

[0022] In some embodiments, in a multi-source CT system, there are more than one set of radiation sources and detectors. In a dual-source CT system, the angle between the two sets of radiation sources + detectors is approximately 90 degrees; in a triple-source CT system, the angle between two adjacent sets of the three sets of radiation sources + detectors is approximately 120 degrees.

[0023] In some embodiments, for a certain tube + detector set, if the bad channel is located on the detector row closest to the center of the data of the center channel β in the projection with an angle α, then:

[0024] a) Compensation is performed using the data from the next adjacent detector in the same direction of gantry rotation. The corresponding channel data is the channel -β data offset from the center in the projection of α + 180° - 2β. Assuming the angle between the two adjacent tube + detector combinations is A, the angle of rotation of the tube + detector combination used for compensation is: α + 180° - 2β - (α + A) = 180° - A - 2β.

[0025] b) Compensation is performed using the data from the previous detector adjacent to the gantry rotation direction. The corresponding channel data is the channel -β data offset from the center in the projection of α-180°+2β. Assuming the angle between the two adjacent tube + detector combinations is A, the angle of rotation of the tube + detector combination used for compensation is: α-180°-2β–(α-A)=-2β+A-180°. In some embodiments, in a dual-source system:

[0026] a) The angle A is approximately 90 degrees and 270 degrees, respectively. If the data from the next adjacent tube + detector combination in the rotational direction is used to correct the data of the current combination, the angle interval of the tube rotation is (180°-90°-2β), and the time interval is: (180°-90°-2β) / 360°·r. When the rotation speed r is 1 second / revolution and the fan angle Fan is 52 degrees, the value range of β is [-26°, 26°]. Therefore, the time difference between correcting the current data with the data from the adjacent tube + detector combination is between [0.11r, 0.39r], which is significantly lower than 0.64r.

[0027] b) Similarly, using the data from the previous tube + detector combination, the same time difference range can be obtained, but it is a negative value, that is, the corresponding data of the previous tube + detector combination was generated earlier;

[0028] c) If it is ensured that the two tube + detector combinations do not scan repeatedly, the combination behind in the rotation direction should stop exposing and collecting data after passing the angle A between the two sets of radiation sources + detectors. This will also result in only data within the range A being able to be corrected using data from adjacent tube + detector combinations.

[0029] In some embodiments, in a three-source system:

[0030] a) The angle A is approximately 120 degrees. Therefore, if the data from the next adjacent tube + detector combination in the rotational direction is used to correct the data of the current combination, the angular interval of the tube rotation is (180°-120°-2β), and the time interval is: (180°-120°-2β) / 360°·r. When the rotation speed r is 1 second / revolution and the fan angle Fan is 52 degrees, the value range of β is [-26°, 26°]. The time difference between correcting the current data with the data from the adjacent tube + detector combination is between [0.02r, 0.31r], which is significantly lower than the maximum value of 0.64r for a single source and 0.39r for a dual source.

[0031] b) Similarly, using the data from the previous tube + detector combination, the same time difference range can be obtained, but it is a negative value, that is, the corresponding data of the previous tube + detector combination was generated earlier;

[0032] c) For a three-source system, since all three tube + detector combinations rotate 120 degrees without duplication to cover all scan angles, data from all angles can be used to find the data from the previous or next tube + detector combination to correct bad data in the current tube + detector channel;

[0033] d) When the starting angle is 0, the value range of α is [0,120), and the possible value range of the projection angle of the subtended ray is α+180°-2β [180°-2β, 300°-2β). When β<60°, it does not fall within the data angle range of [120°, 240°) that can be obtained by the next set of tube + detector combinations, but falls within the angle range of [240°, 360°) of the previous set (which can also be considered as the second set with an interval of 240 degrees). The next set of tube + detector compensation method can be used with a 240-degree angle interval, or the previous set of tube + detector compensation method can be used with a 120-degree interval. The angle interval and time interval results of the two are consistent, both -2β–60°, and

[0034] e) When the starting angle s is not 0 degrees, replace α in the above description with the angle the tube and detector have rotated from the starting angle. In other words, replace α with α-s. This means the algorithm only considers the angle relative to the starting angle.

[0035] According to yet another aspect of the present disclosure, a multi-source computed tomography (CT) system is provided, configured to execute the data correction method or the bad channel data correction method as described above.

[0036] The present disclosure is used to ensure image quality, improve detector yield, and reduce system costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 1 and 2 are schematic diagrams of the application of the present disclosure in a dual-source system;

[0038] 3 and 4 are schematic diagrams of the application of the present disclosure in a three-source system;

[0039] FIG5 is a flowchart of the present disclosure for generating and storing a bad channel distribution map in a three-source system;

[0040] FIG6A is a flow chart of a data correction method according to some embodiments of the present disclosure;

[0041] FIG6B is a flowchart of the bad channel correction process in the present disclosure applied to a three-source system;

[0042] FIG7 is a schematic diagram of using opposite projection data across the same path to correct the current channel in the present disclosure;

[0043] FIG8 is a schematic diagram of time difference correction using reverse ray projection in a three-source system according to the present disclosure. DETAILED DESCRIPTION

[0044] The following will be combined with the accompanying drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0045] In some embodiments, a method for correcting bad channel data of a multi-source CT system includes the following steps: in a multi-source CT system, there are more than one set of radiation sources and detectors; in a dual-source CT system, the angle between the two sets of radiation sources + detectors is approximately 90 degrees; and in a triple-source CT system, the angle between two adjacent sets of the three sets of radiation sources + detectors is approximately 120 degrees.

[0046] The system collects data of different tube currents multiple times, and determines the location and distribution of bad channels through linearity inspection. The projection with the bad channels is the first projection of the first tube-detector combination.

[0047] If the distribution of bad channels satisfies:

[0048] a) Adjacent channels are all good channels;

[0049] b) The bad channel is not within a certain field of view (e.g., 20 cm);

[0050] c) The bad channel is not in the outermost row of several detector acquisition modes supported by the system;

[0051] The data of the target bad channel is corrected by interpolating the data of the channels surrounding the current sampled target bad channel of the current detector.

[0052] If the distribution of bad channels does not meet the above conditions, the following scheme is used to check whether the previous or next tube-detector combination can provide sub-projection data for correcting the target bad channel data. The tube-detector combination that can provide data for correcting the bad channel is the second tube-detector combination.

[0053] If the current bad channel can be corrected using the previous or next set of tube + detector opposite projection data, the data is corrected and then enters the subsequent preprocessing process. The selection of opposite projection data is based on the location and distribution of the bad channel.

[0054] The sampling angle of the first projection and the projection angle of the bad channel in the first projection can be determined by the position and distribution of the bad channel. The projection angle is the angle at which the bad channel deviates from the central channel in the first tube-detector combination.

[0055] For a set of tubes and detectors, if the bad channel is located in the data of the center channel β (on the detector row closest to the center) in the projection with an angle of α, then:

[0056] When compensation is performed using data from the next adjacent detector in the same direction of gantry rotation, the corresponding channel data is -β data offset from the center channel in the projection of α+180°-2β. In other words, the second projection is the projection acquired by the second tube-detector combination at a sampling angle of α+180°-2β. The opposite projection angle is the angle by which the channel corresponding to the bad channel in the second tube-detector combination deviates from the center channel, i.e., -β. Assuming the angle between the two adjacent tube-detector combinations is A, the angle of rotation of the tube-detector combination used for compensation is: α+180°-2β-(α+A)=180°-A-2β. In this case, the second projection is acquired after the first projection.

[0057] When compensation is performed using data from the previous detector adjacent to the gantry rotation, the corresponding channel data is the -β-degree deviation from the center channel in the projection of α-180° + 2β. In other words, the second projection is obtained by the second tube-detector combination at a sampling angle of α-180° + 2β. The subtended projection angle is the angle by which the channel corresponding to the defective channel in the second tube-detector combination deviates from the center channel, i.e., -β. Assuming the angle between the two adjacent tube-detector combinations is A, the angle of rotation of the tube-detector combination used for compensation is: α-180° - 2β – (α-A) = -2β + A-180°. In this case, the second projection is acquired before the first projection.

[0058] In a dual-source system:

[0059] The angles A are approximately 90 degrees and 270 degrees, respectively, as shown in Figure 1. Therefore, if the data from the next adjacent tube + detector combination in the rotational direction is used to correct the data of the current combination, the angular interval of the tube rotation is (180° - 90° - 2β), and the time interval is: (180° - 90° - 2β) / 360°·r. When the rotation speed r is 1 second / rev and the fan angle Fan is 52 degrees, the value range of β is [-26°, 26°]. Therefore, the time difference between correcting the current data with the data from the adjacent tube + detector combination is between [0.11r, 0.39r], which is significantly lower than the time interval between projections used for data correction in a single-source CT system.

[0060] Similarly, using the data of the previous adjacent tube + detector combination, the same time difference range can be obtained, but it is a negative value, that is, the corresponding data of the previous tube + detector combination was generated earlier.

[0061] If it is ensured that the two tube + detector combinations do not scan repeatedly, the combination behind in the rotation direction should stop exposing and collecting data after passing the angle A between the two sets of radiation sources + detectors (as shown in Figure 2). This will also result in only the data within the range of A being corrected using the data from the adjacent tube + detector combination.

[0062] In a three-source system:

[0063] The angle A is approximately 120 degrees, as shown in Figure 3. Therefore, if the data of the next adjacent tube + detector combination in the rotation direction is used to correct the data of the current combination, the angular interval of the tube rotation is (180°-120°-2β), and the time interval is: (180°-120°-2β) / 360°·r. When the rotation speed r is 1 second / revolution and the fan angle Fan is 52 degrees, the value range of β is [-26°, 26°]. Therefore, the time difference between correcting the current data with the data of the adjacent tube + detector combination is between [0.02r, 0.31r], which is significantly lower than the time interval between projections used for data correction in a single-source CT system and the time interval between projections used for data correction in a dual-source CT system.

[0064] Similarly, using the data of the previous adjacent tube + detector combination, the same time difference range can be obtained, but it is a negative value, that is, the corresponding data of the previous tube + detector combination was generated earlier.

[0065] For a three-source system, since all three tube + detector combinations rotate 120 degrees without duplication to cover all scanning angles, as shown in Figure 4, data from all angles can be used to find the data of the previous or next tube + detector combination to correct bad data in the current tube + detector channel.

[0066] When the starting angle is 0, the value range of α is [0,120), and the possible value range of the projection angle of the subtended ray is α+180°-2β [180°-2β, 300°-2β). When β<60°, it does not fall within the data angle range of [120°, 240°) that can be obtained by the next set of tube + detector combinations, but falls within the angle range of [240°, 360°) of the previous set (which can also be considered as the second set with an interval of 240 degrees). Therefore, the next set of tube + detector compensation method can be used with a 240-degree angle interval, or the previous set of tube + detector compensation method can be used with a 120-degree interval. The angle interval and time interval results of the two are consistent, both -2β–60°, and

[0067] When the starting angle s is not 0 degrees, α in the above description can be replaced with the angle of rotation of the tube and detector from the starting angle. In other words, α in the above description can be replaced with α-s. This means that the algorithm only considers the angle of rotation relative to the starting angle. It should be understood that when the starting angle s is not 0 degrees, the range of α is [0+s, 120+s), and the possible range of the sampling angle of the projection of the subtended ray is α+180°-2β [180°+s-2β, 300°+s-2β].

[0068] After determining the corresponding tube + detector combination and sampling angle, the corresponding channel is calculated based on the angle between the channel and the central channel. Assuming the channel spacing is dβ degrees, the corresponding channel is ch = -β / dβ. If ch is an integer, the corresponding channel exists, and the projection data of channel ch is directly used as the subtended projection data. If ch is a non-integer, the corresponding projection value can be calculated using linear interpolation.

[0069] In a CT system, the data correction process includes two parts: bad channel distribution map generation and storage (Figure 5) and bad channel correction during scanning (Figures 6A-6B).

[0070] The following describes the process of a data correction method according to some embodiments of the present disclosure, with reference to Figure 6A. As shown in Figure 6A, the data correction method includes: Step S1, determining the location and distribution of bad channels in a first projection of a first tube-detector assembly; Step S2, if the distribution of the bad channels does not meet a preset condition, determining opposite projection data corresponding to the bad channels in a second projection of a second tube-detector assembly; and Step S3, correcting the projection data of the bad channels using the opposite projection data.

[0071] Since the opposite-ray projection data of the three-source CT system is more complete than that of the dual-source system and the single-source system is relatively simple, only the process of correcting bad channel data using the opposite-ray projection data in the three-source system is given here, as shown in Figure 6B.

[0072] To reduce or relax the requirements for bad channel distribution, the current channel can be corrected using projection data from opposite directions that traverse the same path. Figure 7 shows that for a fan-beam projection with an angle α, a projection line that deviates from the center channel by an angle β and a projection line that deviates from the center channel by an angle α+180°-2β traverse the same path, allowing them to compensate for each other. (β is centered on the focal point and the line passing through the center channel is 0 degrees. The leading - sign indicates that the angle is in the opposite direction of β. Assuming the fan angle is Fan, the value range of β is [-Fan / 2, +Fan / 2].)

[0073] For CT systems with wider detectors, due to the influence of the cone angle, the outer rows of the detector in the z direction are not suitable for compensation in this way, but the errors of several rows close to the center of the detector in the z direction are small enough.

[0074] Although using the two projection data of α and α+180°-2β to compensate each other brings more data for compensation, it also has limitations. In medical CT, the patient himself has various movements, such as breathing, heartbeat, and peristalsis of the gastrointestinal tract in the patient's body.

[0075] In a single-source CT system, α and α+180°-2β. Since the value range of β is [-Fan / 2, +Fan / 2], the maximum interval between the two is 180°+Fan. Assuming the gantry speed is r seconds / revolution, the time interval between the two projections is r(180°+Fan) / 360. When the fan angle is 52 degrees, the interval is 0.64r. Therefore, the time interval is relatively large. Using data with a large time interval to compensate for the artifacts that are easily affected by patient motion.

[0076] In the dual-source system disclosed herein, the current data is corrected using the data from the adjacent tube + detector combination. At a fan angle of 52 degrees, the interval is between [0.11r, 0.39r], which is significantly lower than the longest time interval of 0.64r between the current data and the correction using the tube + detector combination itself.

[0077] In the three-source system disclosed herein, the current data is corrected using the data from the adjacent tube + detector combination. At a fan angle of 52 degrees, the interval is between [0.02r, 0.31r], which is significantly lower than the longest time interval of 0.64r between the current data and the correction using the tube + detector combination itself, and also lower than the longest time interval of 0.39r in the dual-source system.

[0078] For a three-source system with a 120-degree interval and a 52-degree fan angle, the time difference corrected by back-ray projection for each channel and sampling angle is shown in Figure 8. It can be seen that the maximum time difference is 0.31 times the gantry speed.

[0079] The data correction method proposed in the present disclosure significantly reduces the time interval between the projection used for correction and the projection with the bad channel, thereby ensuring image quality, improving detector yield, and reducing system cost.

[0080] In some embodiments, the present disclosure also proposes a multi-source computed tomography (CT) system that can execute the data correction method described above or the bad channel data correction method described above, thereby ensuring image quality, improving detector yield, and reducing system costs.

[0081] Thus far, various embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details known in the art have not been described. Based on the above description, those skilled in the art can fully understand how to implement the technical solutions disclosed herein.

[0082] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art will understand that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. Those skilled in the art will understand that the above embodiments may be modified or some technical features may be replaced with equivalents without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A data correction method for a multi-source computed tomography (CT) system, comprising: Determine the location and distribution of bad channels in a first projection of a first tube-detector combination; When the distribution of the bad channels does not satisfy a preset condition, determining opposite projection data corresponding to the bad channels in a second projection of a second tube-detector combination; The projection data of the bad channel is corrected using the opposite projection data.

2. The data correction method according to claim 1, wherein: Determining the subtended projection data corresponding to the bad channel in the second projection of the second tube-detector combination includes: Determining a sampling angle of the first projection and a projection angle of the bad channel according to the position and distribution of the bad channel; Determining the second projection according to a sampling angle of the first projection and a projection angle of the bad channel; Determine, according to the projection angle of the bad channel, a subtended projection angle corresponding to the bad channel in the second projection; The opposite projection data is determined according to the opposite projection angle.

3. The data correction method according to claim 2, wherein: Determining the second projection according to the sampling angle of the first projection and the distribution of the bad channels includes: In the case where the second projection is acquired after the first projection, the second projection is a projection of the second tube-detector combination at a sampling angle α+180°-2β, wherein α is a sampling angle of the first projection, β is a projection angle of the bad channel, and the projection angle is an angle at which the bad channel in the first tube-detector combination deviates from the central channel; In the case where the second projection is acquired before the first projection, the second projection is a projection of the second tube-detector combination at a sampling angle α-180°+2β.

4. The data correction method according to claim 3, wherein: The opposite projection angle is the angle at which the channel corresponding to the bad channel in the second tube detector combination deviates from the central channel, which is -β.

5. The data correction method according to claim 4, wherein: Determining the opposite projection data according to the opposite projection angle includes: According to the opposite projection angle -β and the channel interval dβ in the second tube detector combination, determining that the channel corresponding to the opposite projection angle in the second tube detector combination is ch=-β / dβ; When ch is an integer, the subtended projection data is determined according to the projection data of the channel ch; When ch is a non-integer, the projection data corresponding to the channel ch is calculated using a linear interpolation method based on the projection data of adjacent channels.

6. The data correction method according to any one of claims 1 to 5, further comprising: According to the first projection of the first tube-detector combination and the second projection of the second tube-detector combination, an angle at which a gantry of a CT system rotates between the first projection and the second projection is determined.

7. The data correction method according to claim 6, wherein: Determining an angle at which a gantry of a CT system rotates between the first projection and the second projection includes: When the second projection is a projection of the second tube-detector assembly at a sampling angle of α+180°-2β, the angle of rotation of the gantry is determined to be α+180°-2β-(α+A)=180°-A-2β, wherein A is the angle between the first tube-detector assembly and the second tube-detector assembly; and / or When the second projection is a projection of the second tube-detector combination at a sampling angle of α-180°+2β, the gantry rotation angle is determined to be α-180°+2β−(α-A)=2β+A-180°.

8. The data correction method according to claim 7, wherein: The CT system is a dual-source CT system, the angle A between the first tube-detector assembly and the second tube-detector assembly is 90° or 270°, and the gantry rotation angle is 180°-90°-2β or 2β+90°-180°.

9. The data correction method according to claim 7, wherein: The CT system is a three-source CT system, the angle A between the first tube-detector combination and the second tube-detector combination is 120°, and the gantry rotation angle is 180°-120°-2β or 2β+120°-180°.

10. The data correction method according to any one of claims 1 to 9, wherein: The CT system is a three-source CT system, and when the distribution of the bad channels does not meet the preset conditions, further includes: A second tube-detector combination is determined according to the starting angle s of the three-source CT system, the sampling angle α of the first image, and the projection angle β of the bad channel.

11. The data correction method according to claim 10, wherein determining the second tube-detector combination comprises: When the value of α+180°-2β is within the angle range [120°+s, 240°+s), the second tube detector combination is determined to be the first tube detector combination in the clockwise direction of the first tube detector combination; When the value of α+180°-2β is within the angle range [240°+s, 360°+s), the second tube-detector combination is determined to be the first tube-detector combination in the counterclockwise direction of the first tube-detector combination.

12. The data correction method according to any one of claims 1 to 11, further comprising: When the distribution of the bad channel meets a preset condition, projection data of the bad channel is interpolated and corrected by using projection data of a channel adjacent to the bad channel in the first projection, and the preset condition includes: The adjacent channels of the bad channel are all good channels; The bad channel is not within a certain visual range close to the central channel; The bad channel is not in the outermost row of several detector acquisition modes supported by the CT system.

13. A method for correcting bad channel data of a multi-source CT system, characterized by: The steps are as follows: Step 1. Collect data of different tube currents for the system for multiple times, and determine the location and distribution of the bad channel through linear inspection; Step 2. If the distribution of bad channels satisfies: a) Adjacent channels are all good channels; b) The bad channel is not within a certain field of view close to the center; c) The bad channel is not in the outermost row of several detector acquisition modes supported by the system; Then the data of the target bad channel is corrected by interpolating the data of the channels surrounding the bad channel of the current detector; Step 3. If the distribution of the bad channels does not meet the conditions of step 2, then check whether the previous or next tube + detector combination can provide opposite projection data to correct the data of the target bad channels; Step 4. If the target bad channel can be corrected by using the opposite projection data of the previous or next group of tubes + detectors, the opposite projection data is selected according to the number of tubes + detectors and the relative position relationship of the CT system, and then the data is corrected and enters the subsequent preprocessing process; The selection of opposite projection data is performed according to the number and relative position relationship of the tubes + detectors of the CT system, specifically including: for a certain set of tubes + detectors, when the sampling angle is α, if the bad channel is located on a channel that deviates from the center channel by an angle of β, then: The data of the next adjacent detector with the same rotation direction as the gantry is used for compensation. The corresponding data is the projection data deviating from the center channel -β in the projection with a sampling angle of α+180°-2β; assuming that the angle between the two adjacent tube + detector combinations is A, the angle of rotation of the tube + detector combination used for compensation is: α+180°-2β-(α+A)=180°-A-2β; Alternatively, the data of the previous detector adjacent to the gantry rotation direction is used for compensation. The corresponding data is the projection data deviating from the center channel -β in the projection with a sampling angle of α-180°+2β; assuming that the angle between the two adjacent tube + detector combinations is A, the angle of rotation of the tube + detector combination used for compensation is: α-180°-2β–(α-A)=-2β+A-180°; After determining the corresponding tube + detector combination and sampling angle, the corresponding channel is calculated according to the angle between the target channel and the center channel. Assuming that the interval between the detector channels is dβ degrees, the corresponding channel is ch = -β / dβ. If ch is a non-integer, the corresponding projection value is calculated using the linear interpolation method.

14. The method for correcting bad channel data of a multi-source CT system according to claim 13, characterized in that: In a multi-source CT system, there are more than one set of radiation sources and detectors. In a dual-source CT system, the angle between two sets of radiation sources + detectors is about 90 degrees; in a triple-source CT system, the angle between two adjacent sets of three sets of radiation sources + detectors is about 120 degrees.

15. The method for correcting bad channel data of a multi-source CT system according to claim 14, characterized in that: In a dual-source CT system: a) The angle A between the two tube + detector combinations is approximately 90 degrees (for the group of detectors at the rear in the rotation direction) and 270 degrees (for the group of detectors at the front in the rotation direction). If the data of the next tube + detector combination adjacent in the rotation direction is used to correct the data of the current combination, the angle interval of the tube rotation is (180°-90°-2β), and the time interval is: (180°-90°-2β) / 360°·r, where r is the rotation speed of the rack. For example: when the rotation speed r is 1 second / revolution and the fan angle Fan of the beam composed of all detector channels and radiation sources is 52 degrees, the value range of β [-Fan / 2, Fan / 2] is [-26°, 26°]. Therefore, the time difference between the correction of the current data with the adjacent tube + detector combination data is between [0.11r, 0.39r], which is significantly lower than the time difference of 0.64r between the correction of the current data and the use of the own tube + detector combination; b) Similarly, using the data of the previous adjacent tube + detector combination, the same time difference range can be obtained, but it is a negative value, that is, the corresponding data of the previous tube + detector combination was generated earlier; c) If it is ensured that the two tube + detector combinations do not scan repeatedly, the combination behind in the rotation direction should stop exposing and collecting data after passing the angle A between the two sets of radiation sources + detectors. This will result in only data within the range of A being corrected using data from the adjacent tube + detector combination.

16. The method for correcting bad channel data of a multi-source CT system according to claim 14, characterized in that: In a three-source CT system: a) The angle A is approximately 120 degrees. Therefore, if the data of the next adjacent tube + detector combination in the rotation direction is used to correct the data of the current combination, the angle interval of the tube rotation is (180°-120°-2β), and the time interval is: (180°-120°-2β) / 360°·r. When the rotation speed r is 1 second / rotation and the fan angle Fan is 52 degrees, the value range of β is [-Fan / 2, Fan / 2] to [-26°, 26°]. The time difference of correcting the current data with the adjacent tube + detector combination data is between [0.02r, 0.31r], which is significantly lower than the maximum value of 0.64r for a single source (the time difference between the current data and the tube + detector combination can only be used for correction) and the maximum value of 0.39r for dual sources. b) Similarly, using the data of the previous adjacent tube + detector combination, the same time difference range can be obtained, but it is a negative value, that is, the corresponding data of the previous tube + detector combination was generated earlier; c) For the three-source system, since the three tube + detector combinations are rotated 120 degrees respectively without repeating the coverage of all scanning angles, the data of all angles can find the data of the previous or next tube + detector combination to correct the bad data in the current tube + detector channel; d) When the starting angle is 0, the value range of α is [0,120), and the possible value range of the projection angle α+180°-2β of the opposite ray is [180°-2β,300°-2β). When β<60°, it does not fall within the data angle range [120°,240°) of the next tube + detector combination, but falls within the angle range [240°,360°) of the previous group. The angle interval and time interval results of the two are consistent, both -2β–60°, and e) When sampling begins and the starting angle s of the tube is not 0 degrees, replace α in the above description with the angle that the tube + detector has rotated from the starting angle, that is, use α-s to replace α in the above description, that is, the algorithm is only related to the angle rotated relative to the starting angle. 17 . A multi-source computed tomography (CT) system, configured to execute the data correction method according to any one of claims 1 to 12 or the bad channel data correction method according to any one of claims 13 to 16.

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