A method and device for correcting eccentricity of multi-tube CT equipment

Abstract

The present invention discloses a method and device for correcting the eccentricity of a multi-tube CT device. The method includes the following steps: setting a marking point in the detection area of ​​the detection ring so that the rays emitted by the tube can cover the marking point; obtaining the projection image on the detection ring after the rays emitted by the tube cover the marking point; derivatizing the projection image of the tube, and obtaining the pixel coordinates of the area corresponding to the marking point on the projection image of the tube based on the grayscale change of the projection image of the tube; obtaining the spatial physical coordinates of the pixel coordinates on the detection ring; comparing the spatial physical coordinates with the preset coordinates of the marking point to obtain the projection angle offset of the tube; repeating the above steps to obtain the projection angle offset of each tube to perform eccentricity correction on each tube. This method is not only safe and reliable, simple and efficient, but also has higher correction accuracy; in addition, it can also be used with interface software for flexible interface display to more intuitively observe the adjustment results.

Description

Technical Field

[0001] The present invention relates to an eccentricity correction method for multi-tube CT equipment and also relates to a corresponding eccentricity correction device, belonging to the technical field of medical equipment. Background Art

[0002] CT (Computed Tomography) is short for computed tomography. It uses precisely collimated X-ray beams, gamma rays, and ultrasound waves, along with highly sensitive CT detectors, to perform cross-sectional scans of specific parts of the human body. It boasts fast scan times and clear images, making it suitable for diagnosing a wide range of diseases. Currently, tens of thousands of CT machines of various models are installed in hospitals at all levels nationwide. CT examinations are rapidly gaining popularity nationwide, becoming an indispensable tool in medical diagnosis.

[0003] As the signal source of a CT scanner, the tube is one of its most critical core components. Its performance directly impacts image quality and service life. For CT scanners with multiple tubes, ensuring that the tubes are aligned at the same rotational center during installation is challenging. Eccentric tube installation can severely impact the quality of reconstructed images, leading to significant diagnostic errors.

[0004] Traditional methods often use the method of finding the center of gravity of a slender PIN to correct eccentricity. For example, Chinese patent application number 202011121859.X provides a method for achieving precise CT alignment. During the CT alignment process, this method uses the projection data obtained from the scan, combined with the angle information of the specific light beam direction of each channel of the detector, and through an iterative method, accurately calculates the position of the iso channel and the position coordinate of the tube focus on the X-axis. The adjustment amount of the tube focus position is then determined, and the tube focus is mechanically adjusted. This process is repeated until the iso channel reaches the desired position, ultimately achieving precise alignment of the CT equipment.

[0005] However, the above method is not only algorithmically complex but also time-consuming and cannot quickly and easily perform eccentricity correction on a multi-tube CT device. Summary of the Invention

[0006] The primary technical problem to be solved by the present invention is to provide a method for correcting the eccentricity of a multi-tube CT device.

[0007] Another technical problem to be solved by the present invention is to provide an eccentricity correction device for a multi-tube CT device.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] According to a first aspect of an embodiment of the present invention, a method for correcting eccentricity of a multi-tube CT device is provided, comprising the following steps:

[0010] Setting a marking point in the detection area of ​​the detection ring so that the marking point is within the range covered by the rays emitted by the tube;

[0011] Acquire the projection image of the ray emitted by the tube on the detection ring after covering the marking point;

[0012] Derivatively performing a calculation on the projection image of the tube, and obtaining pixel coordinates of an area corresponding to the marking point on the projection image of the tube based on a grayscale change of the projection image;

[0013] Obtaining the spatial physical coordinates of the pixel coordinates on the detection ring;

[0014] Comparing the spatial physical coordinates with the preset coordinates of the marking point to obtain the projection angle offset of the tube;

[0015] Repeat the above steps to obtain the projection angle offset of each tube;

[0016] Based on the projection angle offset of each tube, eccentricity correction is performed on each tube so that the rays emitted by each tube are all directed toward the center of the multi-tube CT device.

[0017] Preferably, acquiring the projection image on the detection ring after the ray emitted by the tube covers the marking point specifically includes:

[0018] Rotate the tube to a set angle around the rotation center of the multi-tube CT device;

[0019] acquiring a plurality of sub-projection images on the detection ring after the rays emitted by the tube cover the marking point during the rotation;

[0020] Arrange the multiple sub-projection images corresponding to the tube in time sequence to obtain a projection image of the tube on the detection ring.

[0021] Preferably, after obtaining the projection images of each tube, the method further includes:

[0022] Arranging the projection images of the tubes to obtain eccentricity curves formed by areas corresponding to the marking points on the projection images of the tubes;

[0023] Comparing the eccentricity curve with a reference curve of each tube relative to the marking point to obtain a reference angle offset of each tube;

[0024] Based on the reference angle offset and the projection angle offset of each tube, eccentricity correction is performed on each tube.

[0025] Preferably, the eccentricity curve and the reference curve are both formed in a projection coordinate system, and the projection coordinate system is established based on a projection angle and pixel positions on the detection ring.

[0026] Preferably, the method of performing a derivation on the projection image of any one of the tubes specifically includes:

[0027] In the projection image of the tube, grayscale values ​​of two adjacent pixel blocks are sequentially subtracted to obtain grayscale difference;

[0028] Comparing the grayscale difference with a set threshold, if the grayscale difference is not greater than the set threshold, the grayscales of the two adjacent pixel blocks have no significant change; if the grayscale difference is greater than the set threshold, the grayscales of the two adjacent pixel blocks have a significant change;

[0029] The coordinates of the pixel block with obvious grayscale changes are used as the pixel coordinates of the area corresponding to the marking point on the projection image of the tube.

[0030] Preferably, during the rotation, a plurality of the tubes are exposed sequentially.

[0031] Preferably, the exposure duration and exposure interval of each tube are the same.

[0032] According to a second aspect of an embodiment of the present invention, there is provided an eccentricity correction device for a multi-tube CT device, comprising:

[0033] A tube support, wherein the tube support has a plurality of tube mounting positions for mounting the tube;

[0034] A detection ring is provided on the inner side of the tube support, and is used to obtain a projection image of the rays emitted by each tube on the detection ring;

[0035] A metal marker is arranged on the inner side of the detection ring and close to the rotation center of the tube holder so that the radiation emitted by each tube can cover the metal marker;

[0036] The image processing unit is connected to the detection ring to receive the projection image and perform derivative processing on the projection image.

[0037] Preferably, the ball tube holder is capable of rotating around a rotation center of the ball tube holder, and a plurality of ball tube mounting positions are evenly distributed on the ball tube holder around the rotation center.

[0038] Preferably, the eccentricity correction device further includes a control system, which is respectively connected to the detection ring, the image processing unit and each of the tubes for program control.

[0039] Compared with the prior art, the present invention has the following technical effects:

[0040] 1) It is not only safe, reliable, simple and efficient, but also has higher correction accuracy than the traditional method of finding the center of gravity of slender markers by differentiating the projection image of the marker points.

[0041] 2) It can be used with interface software to flexibly display interface results through simple interface operations to help users observe the adjustment results more intuitively. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic flow chart of a method for correcting eccentricity of a multi-tube CT device provided in accordance with the first embodiment of the present invention;

[0043] Figure 2 Schematic diagram of the projection image formed by a single tube;

[0044] Figure 3 A schematic flow chart of a method for correcting eccentricity of a multi-tube CT device provided in accordance with a second embodiment of the present invention;

[0045] Figure 4 A schematic diagram of a projection image formed by multiple tubes;

[0046] Figure 5 This is a schematic structural diagram of an eccentricity correction device for a multi-tube CT device provided in a third embodiment of the present invention. DETAILED DESCRIPTION

[0047] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] <First embodiment>

[0049] like Figure 1 As shown, a method for correcting the eccentricity of a multi-tube CT device provided by the first embodiment of the present invention specifically includes steps S1 to S6:

[0050] S1: Set the marking (PIN) point.

[0051] Specifically, such as Figure 5 As shown, after the multiple tubes 10 are installed, a marking point 3 is set in the detection area of ​​the detection ring 2 so that the rays emitted by each tube 10 can cover the marking point 3.

[0052] S2: Obtain the projection image of the tube on the detection ring.

[0053] When tube 10 emits radiation, it impinges on detection ring 2, resulting in a projection image corresponding to tube 10. It should be understood that the radiation emitted from tube 10 is emitted in a fan-shaped pattern. When a radiation impinges on the area where marker 3 is located, it is blocked, while the remaining radiation impinges on detection ring 2. This results in the area corresponding to the marker on detection ring 2 being darker, while the areas corresponding to the remaining radiation are brighter. Consequently, a projection image with a corresponding "dark spot" can be obtained for each tube 10.

[0054] In this embodiment, the process specifically includes steps S21 to S23:

[0055] S21: Rotate the tube around the rotation center of the multi-tube CT device to a set angle.

[0056] Specifically, after the bulb 10 is installed, the bulb 10 needs to be rotated uniformly around the rotation center O by a set angle (for example, 15°, 20°, or 30°).

[0057] S22: Acquire multiple sub-projection images of the tube 10 during the rotation.

[0058] Specifically, during rotation, each tube 10 is exposed at regular intervals. After each exposure, a sub-projection image corresponding to that tube 10 is obtained on the detection ring 2. Thus, during the entire rotation, each tube 10 can obtain multiple sub-projection images. In this embodiment, the angle is set to 15°. With each 1 / 3° rotation, all tubes 10 complete an exposure (in this embodiment, all tubes 10 are exposed sequentially). After the rotation is complete, each tube 10 can obtain 45 sub-projection images.

[0059] It is understood that in this embodiment, the exposure duration and exposure interval of each tube 10 are the same. Of course, in other embodiments, the exposure duration and exposure interval of each tube 10 may be partially the same or completely different, and the specific selection can be adaptive according to actual needs.

[0060] S23: Obtain a projection image of the tube 10 on the detection ring.

[0061] After obtaining the multiple sub-projection images corresponding to the tube 10 in step S22, the multiple sub-projection images corresponding to the tube are arranged in chronological order to obtain the projection image of the tube 10 on the detection ring. Similarly, the projection images of the remaining tubes 10 on the detection ring can be obtained.

[0062] Therefore, the projection image obtained by arranging the multiple sub-projection images can improve the overall clarity and accuracy of the image, which is beneficial to improving the accuracy of subsequent eccentricity adjustment of the tube 10.

[0063] S3: Derivative the projection image of the tube to obtain pixel coordinates of an area corresponding to the marked point on the projection image of the tube.

[0064] Specifically, it includes steps S31 to S33:

[0065] S31: In the projection image of the tube 10, grayscale values ​​of two adjacent pixel blocks are sequentially subtracted to obtain grayscale difference.

[0066] It is understood that each projected image is composed of multiple pixel blocks, and different pixel blocks have different grayscale values. However, the grayscale value differences between pixel blocks in the same brightness area are relatively small, while the grayscale value differences between pixel blocks in different brightness areas are relatively large. In this embodiment, the grayscale value difference between the "dark spot" area and the non-dark spot area of ​​the projected image is relatively large, which can be used to determine the location of the "dark spot" area (described in detail below).

[0067] S32: Compare the grayscale difference with the set threshold.

[0068] Specifically, in this embodiment, a grayscale difference threshold (eg, 1 to 3) is preset. After obtaining the grayscale difference between two adjacent pixel blocks in step S31 , the grayscale difference can be compared with the preset threshold.

[0069] If the grayscale difference is not greater than the set threshold (for example, a grayscale difference of 1, 1.5, or 2), there is no significant change in the grayscale of the two adjacent pixel blocks. If the grayscale difference is greater than the set threshold (for example, a grayscale difference of 10 or greater), there is a significant change in the grayscale of the two adjacent pixel blocks. It can be understood that if there is no significant change in the grayscale of two adjacent pixel blocks, it means that the brightness of the areas where the two pixels are located is similar, and if there is a significant change in the grayscale of two adjacent pixel blocks, it means that the brightness of the areas where the two pixels are located is different.

[0070] like Figure 2 As shown, it is a projection image formed by a single tube 10. The projection image can be regarded as a projection image formed by S1 to S2 in the X direction. n pixel blocks. Among them, S i ~S i+w The area where S1~S2 is located is the "dark spot" area, and the other areas are non-dark spot areas. i-1 The grayscale value difference between them is small, S i-1 With S i The grayscale difference is large, S i ~Si+w The grayscale value difference between them is small, S i+w With S i+w+1 The grayscale difference is large, S i+w+1 ~S n The grayscale value difference between them is small. Therefore, through the change of grayscale, we can find out S i With S i+w The location of the two pixel blocks.

[0071] S33: The coordinates of the pixel block with obvious grayscale changes are used as the pixel coordinates of the area corresponding to the marked point on the projection image of the tube.

[0072] Specifically, once a pixel block with a significant grayscale change is identified in step S32, it indicates that the projected image has entered the "dark spot" region starting from that pixel block. Therefore, the coordinates of that pixel block are used as the pixel coordinates of the region corresponding to the marked point on the projected image of tube 10. It will be appreciated that the significance of these pixel coordinates is to determine the starting point of the "dark spot" region.

[0073] S4: Obtain the spatial physical coordinates of the pixel coordinates on the detection ring.

[0074] Specifically, after determining the starting point of the "dark spot" area, the spatial physical coordinates of that pixel coordinate on the detection ring are determined based on a pre-established spatial coordinate system. This further spatially confirms the starting point of the "dark spot" area. It should be understood that the spatial physical coordinates determined by these pixel coordinates are the actual spatial physical coordinates corresponding to the marked point after illumination by the tube 10.

[0075] S5: Compare the spatial physical coordinates with the preset coordinates of the marking points to obtain the projection angle offset of each tube.

[0076] Specifically, after obtaining the actual spatial physical coordinates corresponding to the marker point in step S4, the spatial physical coordinates are compared with the preset coordinates of the marker point. Based on the comparison results, the offset of the projection angle of the tube can be determined. The preset coordinates of the marker point are the theoretical spatial physical coordinates of the marker point, assuming that the projection angle of the tube 10 is not offset.

[0077] Therefore, by comparing the two, it is possible to determine whether the projection angle of the tube 10 is offset, and if so, the offset amount of the projection angle.

[0078] S6: performing eccentricity correction on each tube based on the projection angle offset of each tube.

[0079] Repeating steps S1 to S5 can obtain the projection angle offset of each tube, so that the eccentricity of each tube can be corrected according to the different projection angle offsets of each tube, so that the rays emitted by each tube are all directed towards the center O of the multi-tube CT device.

[0080] To sum up, the eccentricity correction method provided by the first embodiment of the present invention is not only safe, reliable, simple and efficient, but also has higher correction accuracy than the traditional method of calculating the center of gravity of slender marking points by differentiating the projection image of the marking point; in addition, this method can also be used in conjunction with interface software, and the interface results can be flexibly displayed through simple interface operations to help users observe the adjustment results more intuitively.

[0081] <Second embodiment>

[0082] like Figure 3 As shown, a method for correcting eccentricity of a multi-tube CT device provided by the second embodiment of the present invention is provided. The difference between this embodiment and the first embodiment is that, in this embodiment, after step S2, the method further includes: obtaining a reference angle offset of each tube.

[0083] Specifically, in this embodiment, obtaining the reference angle offset of each tube includes steps S10 to S20:

[0084] S10: Arranging the projection images of the respective tubes 10 to obtain eccentricity curves formed by areas corresponding to the marking points on the projection images of the respective tubes.

[0085] like Figure 4 As shown in FIG. 1 , in this embodiment, the multi-tube CT has a total of 24 tubes 10, so that the projection images of the 24 tubes can be obtained according to step S2. After the projection images of the 24 tubes are arranged in sequence according to the arrangement order of the tubes, the positions corresponding to the marked points on the 24 projection images can be formed as shown in FIG. Figure 4 The eccentricity curve shown (i.e. Figure 4 The eccentricity curve is approximately a sine curve, reflecting the actual position of the projection image formed by the rays emitted by each tube 10 on the detection ring 2.

[0086] S20: Compare the eccentricity curve with a reference curve of each tube relative to the marking point to obtain a reference angle offset of each tube.

[0087] Specifically, in this embodiment, assuming that the projection angles of each tube 10 are uniform, the projection images formed by the rays emitted by each tube 10 are arranged in sequence to form a reference curve for each tube relative to the marked point. This reference curve reflects the theoretical position of the projection images formed by the rays emitted by each tube 10 on the detection ring 2.

[0088] By comparing the actual position with the theoretical position, the reference angle offset of each tube can be obtained using the eccentricity curve and the reference curve. It should be understood that in this embodiment, the eccentricity curve and the reference curve are both generated in a projected coordinate system, which is established based on the projection angle and the pixel position on the detection ring.

[0089] After obtaining the reference angle offset, each tube can be corrected for decentering based on both overall and individual tube data, based on the reference angle offset for each tube in this embodiment and the projection angle offset for each tube obtained in the first embodiment. This improves the accuracy of the decentering correction for each tube.

[0090] Except for the above differences, the remaining steps of this embodiment are the same as those of the first embodiment and will not be repeated here.

[0091] <Third embodiment>

[0092] like Figure 5 As shown, the third embodiment of the present invention further provides an eccentricity correction device for a multi-tube CT device, which specifically includes: a tube holder 1, a detection ring 2, a metal marker (PIN) 3 and an image processing unit 4.

[0093] The tube holder 1 has multiple tube mounting positions 101 for mounting tubes 10. The tube holder 1 is capable of rotating about its rotation center O, with the multiple tube mounting positions 101 evenly distributed around the rotation center. In this embodiment, there are 24 tube mounting positions 101, allowing 24 tubes 10 to be mounted simultaneously on the tube holder 1. The angle between adjacent tubes 10 is 15°. Every time the tube holder 1 rotates 1 / 3° about the rotation center O, the 24 tubes 10 complete one exposure cycle. A 15° rotation of the tube holder 1 constitutes one rotation cycle, and within this rotation cycle, each tube 10 completes 45 exposures.

[0094] A detection ring 2 is disposed inside the tube holder 1 and is used to capture projection images of the radiation emitted by each tube 10 on the detection ring 2. In this embodiment, during one rotation cycle of the tube holder 1, 45 sub-projection images are acquired for each tube 10. These 45 sub-projection images are then arranged in sequence according to the exposure time sequence to form a projection image specific to each tube 10 during that rotation cycle.

[0095] The metal marker 3 is positioned inside the detection ring 2 and near the rotation center O of the tube holder 1, so that the radiation emitted by each tube 10 can cover the metal marker 3. Specifically, in this embodiment, the metal marker 3 is a metal screw, but this structure is not limited to this structure. Other non-transparent materials and appropriately sized structural members can also be used as marking points as needed.

[0096] The image processing unit 4 is connected to the detection ring 2 to receive the projection images of each tube 10 and perform derivative processing on the projection images. Thus, by using interface software, simple interface operations can flexibly display interface results, helping users to more intuitively observe the adjustment results.

[0097] In the above embodiment, the eccentricity correction device may further include a control system. The control system is connected to the detection ring 2, the image processing unit 4, and each tube 10 for program control. Specifically, the control system can control the exposure time of each tube 10 and the detection time of the detection ring 2. Furthermore, the control system can control the image processing unit 4 to perform image processing on the projection images captured by each tube 10 to obtain the projection angle offset and reference angle offset of each tube 10.

[0098] The above describes in detail the eccentricity correction method and apparatus for a multi-tube CT system provided by the present invention. For those skilled in the art, any obvious modification thereof without departing from the essence of the present invention would constitute an infringement of the present invention's patent rights and would incur corresponding legal liability.

Claims

1. A method for correcting the eccentricity of a multi-tube CT device, characterized in that The steps include: Setting a marking point in the detection area of ​​the detection ring so that the marking point is within the range covered by the rays emitted by the tube; Acquire the projection image of the ray emitted by the tube on the detection ring after covering the marking point; The projection image of the tube is differentiated, and based on the grayscale change of the projection image, pixel coordinates of the area corresponding to the marking point on the projection image of the tube are obtained; wherein the differentiation of the projection image of any one of the tubes specifically includes: in the projection image of the tube, sequentially subtracting the grayscale values ​​of two adjacent pixel blocks to obtain a grayscale difference; comparing the grayscale difference with a set threshold; if the grayscale difference is not greater than the set threshold, the grayscale of the two adjacent pixel blocks has not changed significantly; if the grayscale difference is greater than the set threshold, the grayscale of the two adjacent pixel blocks has changed significantly; and using the coordinates of the pixel block with the significant grayscale change as the pixel coordinates of the area corresponding to the marking point on the projection image of the tube; Obtaining the spatial physical coordinates of the pixel coordinates on the detection ring; Comparing the spatial physical coordinates with the preset coordinates of the marking point to obtain the projection angle offset of the tube; Repeat the above steps to obtain the projection angle offset of each tube; Based on the projection angle offset of each tube, eccentricity correction is performed on each tube so that the rays emitted by each tube are all directed toward the center of the multi-tube CT device.

2. The eccentricity correction method according to claim 1, wherein The step of acquiring a projection image on the detection ring after the ray emitted by the tube covers the marking point specifically includes: Rotate the tube to a set angle around the rotation center of the multi-tube CT device; acquiring a plurality of sub-projection images on the detection ring after the rays emitted by the tube cover the marking point during the rotation; Arrange the multiple sub-projection images corresponding to the tube in time sequence to obtain a projection image of the tube on the detection ring.

3. The eccentricity correction method according to claim 1, wherein After obtaining the projection images of each tube, the method further includes: Arranging the projection images of the tubes to obtain eccentricity curves formed by areas corresponding to the marking points on the projection images of the tubes; Comparing the eccentricity curve with a reference curve of each tube relative to the marking point to obtain a reference angle offset of each tube; Based on the reference angle offset and the projection angle offset of each tube, eccentricity correction is performed on each tube.

4. The eccentricity correction method according to claim 3, wherein: The eccentricity curve and the reference curve are both formed in a projection coordinate system, and the projection coordinate system is established based on a projection angle and pixel positions on the detection ring.

5. The eccentricity correction method according to claim 2, wherein: During the rotation, a plurality of the tubes are exposed sequentially.

6. The eccentricity correction method according to claim 5, wherein: The exposure duration and exposure interval of each tube are the same.

7. An eccentricity correction device for a multi-tube CT device, characterized in that include: A tube support, wherein the tube support has a plurality of tube mounting positions for mounting the tube; A detection ring is provided on the inner side of the tube support, and is used to obtain a projection image of the rays emitted by each tube on the detection ring; A metal marker is provided at a marking point on the inner side of the detection ring and close to the rotation center of the tube holder so that the rays emitted by each tube can cover the metal marker; an image processing unit connected to the detection ring to receive the projection image and perform derivative processing on the projection image; The method of deriving the projection image of any one of the tubes specifically includes: In the projection image of the tube, grayscale values ​​of two adjacent pixel blocks are sequentially subtracted to obtain grayscale difference; Comparing the grayscale difference with a set threshold, if the grayscale difference is not greater than the set threshold, the grayscales of the two adjacent pixel blocks have no significant change; if the grayscale difference is greater than the set threshold, the grayscales of the two adjacent pixel blocks have a significant change; The coordinates of the pixel block with obvious grayscale changes are used as the pixel coordinates of the area corresponding to the marking point on the projection image of the tube.

8. The eccentricity correction device according to claim 7, characterized in that: The ball tube bracket can rotate around the rotation center of the ball tube bracket, and a plurality of ball tube mounting positions are evenly distributed on the ball tube bracket around the rotation center.

9. The eccentricity correction device according to claim 7, characterized in that It also includes a control system, which is respectively connected to the detection ring, the image processing unit and each of the tubes for program control.

Images