CT device

Abstract

The present invention achieves an optimal resolution by achieving an imaging distance (FCD) corresponding to the shape of an object to be inspected and a set scanning region. The CT apparatus includes: an examination table on which an object to be examined is placed and which moves and rotates the object to be examined; a radiation source that irradiates a radiation beam on the object to be inspected; a detector provided facing the radiation source across the object to be inspected; a limit distance calculation unit that calculates a limit distance, which is the minimum distance required to prevent the inspection object from coming into contact with the radiation source during rotation, among the distances between the focal point of the radiation source and the center of the inspection object; a scanning region distance calculation unit that calculates a scanning region distance, which is a distance between a focal point of the radiation source required in the set scanning region and a center of the object to be inspected; a comparison section that compares the limit distance with the scanning region distance to determine a photographing distance; and an inspection table control unit that controls the inspection table so that the object to be inspected approaches or moves away from the radiation source.

Description

Technical Field

[0001] The embodiments of the present invention relate to a CT device. Background Technology

[0002] Industrial CT scanners are widely used for high-resolution inspection of small electronic components such as lithium-ion batteries. In these scanners, a radiation source, which irradiates the object as an X-ray beam, and a detector, which detects the X-ray beam at two-dimensional resolution, are positioned opposite each other. A rotating inspection table is placed between the radiation source and the detector. The object being inspected is placed on the inspection table, rotates during imaging, and is irradiated with radiation from all directions.

[0003] The distance between the focal point of the radiation source and the center of rotation of the object being examined is usually called the focal depth (FCD). Since a shorter FCD results in higher resolution, the object being examined is sometimes placed as close as possible to the radiation source for imaging.

[0004] When the object being photographed is a rectangle, ellipse, or other shape with a high aspect ratio, it's possible to bring the object closer to the radiation source when the shorter side faces it; however, when the longer side faces it, the object needs to be moved away from the radiation source. Therefore, it's necessary to know the shape of the object and adjust the FCD accordingly during photography. One known method involves calculating the dimension d from the rotation center of the object A to its end, and using this dimension d to move the object closer to or further away from the radiation source. Existing technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2024-71371 Summary of the Invention The problem that the invention aims to solve

[0006] On the other hand, when taking a picture, the scanning area is set in advance. The number of FCDs required based on the size of the set scanning area needs to be calculated separately from the shape of the object being inspected. If the number of FCDs exceeds the size d of the object being inspected, and the FCDs are controlled according to the size d of the object being inspected, the scanning area will become too small.

[0007] The embodiments of the present invention were made to solve the above-mentioned problems, and their purpose is to provide a CT device that realizes FCD corresponding to the shape of the object being examined and the set scanning area, thereby achieving optimal resolution. Methods for solving problems

[0008] The CT apparatus in the embodiments of the present invention is a CT apparatus that performs imaging while rotating the subject being examined, comprising: an examination table for placing the subject being examined and for moving and rotating the subject being examined; a radiation source for irradiating the subject being examined with a radiation beam; a detector disposed opposite to the radiation source across the subject being examined; and a limit distance calculation unit for calculating the limit distance FCD. L The limiting distance FCD L The minimum distance required to prevent the object from contacting the radiation source during rotation is defined in the distance FCD between the focal point of the radiation source and the center of the object being inspected; the scanning area distance calculation unit calculates the scanning area distance FCDs, which are the distances between the focal point of the radiation source and the center of the object being inspected within the set scanning area; the comparison unit compares the limit distance FCDs. L The scanning area is compared with the distance to the FCDs to determine the imaging distance of the FCDs when imaging is performed; and the inspection table control unit controls the inspection table to move the object under inspection closer to or further away from the radiation source based on the imaging distance determined by the comparison unit during imaging. Attached Figure Description

[0009] Figure 1 This is a side view schematically illustrating an embodiment of a CT device. Figure 2 This is a top view schematically illustrating an embodiment of a CT apparatus. Figure 3 It is a block diagram showing the structure of the control unit. Figure 4 This is a flowchart illustrating the calculation method of the shooting distance FCD in the implementation method. Figure 5 It is a diagram that represents the state of setting the ROI on a perspective image. Figure 6 It is a graph showing the distance from the center of rotation of the object being inspected to its end. Figure 7 It represents the limit distance FCD L A graph showing the relationship between rotation angle and rotation angle. Figure 8 It means in the future Figure 7 When the chart is offset by 90 degrees, the limit distance FCD L A graph showing the relationship between rotation angle and rotation angle. Figure 9 This indicates the FCD at its maximum distance. L A graph showing the relationship between the rotation angle and the specified distance is added above. Figure 10 This is a diagram showing the settings for the scanning area. Figure 11 This indicates that the distance from the FCDs in the scanning area is longer than the limit distance of the FCD. L A chart showing the shooting distance at its maximum value. Figure 12 This indicates that the distance from the FCDs in the scanning area is shorter than the limit distance of the FCD. L A chart showing the shooting distance at its minimum value. Figure 13 This indicates that the scanned area is at the limit distance of the FCDs. L A chart showing the shooting distance when the value is above the minimum and below the maximum. Figure 14 These are images showing perspective images before and after magnification. (a) is the perspective image before magnification, and (b) is the perspective image after magnification. Figure 15 This is a schematic side view of a modified CT device. Figure 16 This is a diagram illustrating the method of moving the object under inspection in a modified example. Figure 17 It is a diagram showing the movement trajectory of the rotation center of the inspected object in a modified example. Explanation of reference numerals in the attached figures 100: CT apparatus; 1: Examination table; 11: Rotary worktable; 12: Lifting mechanism; 13: Y-mechanism; 14: X-mechanism; 2: Radiation source; 21: Support frame; 3: Detector; 31: Support frame; 4: Filter unit; 5: Camera; 6: Display unit; 7: Input unit; 8: Control unit; 81: Examination table control unit; 82: Radiation source control unit; 83: Reconstruction unit; 84: Camera control unit; 85: Limit distance calculation unit; 86: Scanning area distance calculation unit; 87: Comparison unit; 88: Magnification calculation unit. Detailed Implementation

[0010] [Implementation Method] The CT apparatus of the embodiment will now be described in detail with reference to the accompanying drawings. Figure 1 This is a side view schematically illustrating an embodiment of a CT device. Figure 2 This is a top view schematically illustrating an embodiment of a CT apparatus.

[0011] The CT apparatus 100 is a device for non-destructive examination of an object A. The CT apparatus 100 irradiates the area around the object A with a radiation beam B that passes through it, and detects the amount of radiation attenuated due to the passing through the object A. Then, based on the detection result, a cross-sectional image of the object A, i.e., a CT image, is generated. Furthermore, the CT apparatus 100 generates a 3D image based on the generated multiple CT images. The object A refers to an object with a high aspect ratio, such as a cylindrical object that is elliptical when viewed from the axis of rotation C. In this embodiment, during imaging, the object A is positioned closer to or further away from the radiation source 2, depending on its shape.

[0012] like Figure 1 As shown, the CT apparatus 100 includes an examination table 1, a radiation source 2, a detector 3, a filter unit 4, a camera 5, a display unit 6, an input unit 7, and a control unit 8. The examination table 1 is a platform having a mounting surface for placing the object A to be examined. The examination table 1 can move in a direction parallel or orthogonal to the mounting surface. Furthermore, the examination table 1 can rotate about a rotation axis C perpendicular to the mounting surface. During imaging, the examination table 1 rotates and moves the object A to be examined. The examination table 1 includes a rotary table 11, a lifting mechanism 12, a Y-mechanism 13, and an X-mechanism 14.

[0013] A rotary stage 11 holds the object to be inspected, A. The rotary stage 11 holds the object to be inspected such that its rotation axis C is coaxial with the center of the object to be inspected, A. The rotary stage 11 is, for example, composed of an actuator including a drive source such as a motor, and is configured to rotate about the rotation axis C in a direction perpendicular to the mounting surface. During irradiation with the radiation beam B, the rotary stage 11 rotates, thereby irradiating the object to be inspected A from all directions with the radiation beam B. Alternatively, a sample stage may be provided on the rotary stage 11, and the object to be inspected A may be placed on the sample stage.

[0014] The lifting mechanism 12 is located below the rotary table 11. The lifting mechanism 12 can be a ball screw mechanism driven by a servo motor. The lifting mechanism 12 can move in a direction orthogonal to the mounting surface. That is, by moving the lifting mechanism 12 in a direction orthogonal to the mounting surface, the height of the object to be inspected A can be adjusted.

[0015] The Y-mechanism 13 is located below the lifting mechanism 12. The Y-mechanism 13 can be, for example, a ball screw mechanism driven by a servo motor. The Y-mechanism 13 is capable of moving in a direction parallel to the mounting surface and orthogonal to the optical axis of the radiation beam B (hereinafter also referred to as the Y direction).

[0016] The X-mechanism 14 is located below the Y-mechanism 13. The X-mechanism 14 can be, for example, a ball screw mechanism driven by a servo motor. The X-mechanism 14 is capable of moving in a direction parallel to the optical axis of the radiation beam B (hereinafter also referred to as the X-direction). The X-mechanism 14 is configured to allow the inspection table 1, the radiation source 2, and the detector 3 to move independently. By using the X-mechanism 14 to move the object A under inspection, the object A can be moved closer to or further away from the radiation source 2.

[0017] The radiation source 2, for example, irradiates the object A being examined with a radiation beam B. The radiation beam B is a conical beam of radiation that diffuses in a fan-shaped and conical shape, with the focal point F of the radiation source 2 as its apex. In this embodiment, the radiation source 2 is, for example, a reflective or transmissive micro-focusing X-ray tube or a nano-focusing X-ray tube, and the radiation beam B is an X-ray beam. Furthermore, the radiation beam B is not limited to an X-ray beam; any beam that transmits through the object A, such as gamma rays, can be used. The radiation source 2 is supported by a support frame 21. The radiation source 2 can be moved in the X-direction by the X-mechanism 14.

[0018] Detector 3 is positioned opposite radiation source 2, separated from inspection table 1 and the object being inspected A. Detector 3 is positioned so that the center of the imaging area is aligned with the optical axis of radiation source 2. Detector 3 detects the two-dimensional distribution of radiation intensity, which is reduced according to the transmission path of radiation beam B, and outputs a radiographic image. Detector 3 may be, for example, a flat panel display (FPD). Detector 3 is supported by support frame 31. The distance between detector 3 and the object being inspected A is adjusted by X-mechanism 14.

[0019] The filter section 4 is positioned close to the radiation source 2, between the object being inspected A and the radiation source 2. The filter section 4 is a thin plate-like component with a thickness of approximately a few millimeters. The filter section 4 is made of a metal plate formed from copper, aluminum, iron, or alloys containing these materials. Multiple filter sections 4 are provided, and each has a different material and thickness.

[0020] The filter unit 4 is configured to be movable via a moving mechanism (not shown). The moving mechanism can be, for example, a ball screw mechanism driven by a servo motor. The moving mechanism moves the user-selected filter unit 4 along the optical axis of the radiation source 2. A radiation beam B is irradiated onto the filter unit 4 positioned on the optical axis, and the radiation beam B passing through the filter unit 4 irradiates the object A under inspection. By allowing the radiation to pass through the filter unit 4, the generation of metal artifacts is suppressed.

[0021] Additionally, the CT device 100 may also include a collimator (not shown). The collimator is a device that restricts the forward path and incident area of ​​the radiation beam B. The collimator is formed of a material with high specific gravity and high shielding capability, such as tungsten or molybdenum. The collimator is symmetrically arranged vertically between the radiation source 2 and the object being examined A, centered on the optical axis of the radiation beam B from the radiation source 2.

[0022] Camera 5 is positioned above the rotary table 11. That is, camera 5 is positioned opposite the rotary table 11, with the object being inspected A in between. Camera 5 is, for example, a CCD camera. Camera 5 takes pictures of the object being inspected A from above.

[0023] Display unit 6 is, for example, a monitor such as a liquid crystal display or an organic EL display. Display unit 6 displays various images, including fluoroscopic images, CT images, and 3D images of the object being inspected A, as well as the shooting area, shooting time, and shooting conditions.

[0024] The input unit 7 can be used with a keyboard, mouse, touch panel, etc. The input unit 7 accepts various operations such as menu selection for formal shooting or test shooting, shooting time, shooting conditions modification, manual operation of the moving mechanism, shooting start, and selection of the part of the object to be inspected A to be observed.

[0025] The control unit 8 consists of a computer and drive circuitry. The computer comprises a memory such as an HDD or SSD, RAM, a CPU, etc. The control unit 8 controls the various components of the CT device 100. The control unit 8 is connected to the input unit 7, and the user controls the various components of the CT device 100 via the input unit 7.

[0026] Figure 3 This is a block diagram showing the structure of the control unit 8. For example... Figure 3 As shown, the control unit 8 includes an inspection table control unit 81, a radiation source control unit 82, a reconstruction unit 83, a camera control unit 84, a limit distance calculation unit 85, a scanning area distance calculation unit 86, a comparison unit 87, and a magnification calculation unit 88.

[0027] The inspection table control unit 81 controls the rotary table 11, the lifting mechanism 12, the Y mechanism 13, and the X mechanism 14. Through the control of the inspection table control unit 81, the object A placed on the inspection table 1 can be aligned with the optical axis of the radiation beam B, or the object A can be rotated one revolution during irradiation by the radiation beam B. Furthermore, by controlling the inspection table control unit 81, the inspection table 1 can be moved, thereby adjusting the distance FCD between the focal point F of the radiation source 2 and the center of the object A. That is, during imaging, the object A can be moved closer to or further away from the radiation source 2. Based on the results of the comparison unit 87, the inspection table control unit 81 controls the X mechanism 14 to change the distance FCD during imaging.

[0028] The radiation source control unit 82 controls the radiation source 2 to irradiate the object being inspected, A, with radiation beam B. That is, through the control of the inspection table control unit 81 and the radiation source control unit 82, the object being inspected is irradiated with radiation beam B from all directions.

[0029] The reconstruction unit 83 reconstructs the CT imaging area encompassed by the radiation beam B based on the fluoroscopic images obtained in a 360-degree direction. The reconstruction unit 83 sends the fluoroscopic images to the limit distance calculation unit 85. If the magnification is calculated by the magnification calculation unit 88, the reconstruction unit 83 performs reconstruction based on that magnification. The reconstruction unit 83 reconstructs multiple cross-sectional images arranged continuously at equal intervals in a direction orthogonal to the mounting plane of the object being examined A, forming three-dimensional data from these multiple cross-sectional images. The three-dimensional data can be displayed on the display unit 6 using MPR (Multi-planar Reconstruction) display or similar methods.

[0030] The camera control unit 84 controls the camera 5. The camera control unit 84 controls the position of the camera 5 and the timing of shooting. The camera control unit 84 sends the data captured by the camera 5 to the scanning area distance calculation unit 86.

[0031] The limit distance calculation unit 85 calculates the limit distance FCD based on the perspective image of the inspected object A. L Extreme distance FCD L This refers to the minimum distance required from the FCD to prevent the inspected object A from contacting the radiation source 2 during rotation. The limit distance calculation unit 85 calculates the limit distance of the inspected object A to the FCD over 360 degrees. L .

[0032] The limit distance calculation unit 85 can calculate the limit distance FCD. L Add a predetermined distance α. For example, if there is a distance between the focal point F of radiation source 2 and the window of radiation source 2, this length can be added as the predetermined distance α. Additionally, to create gaps between radiation source 2 and the object A being inspected, the length of these gaps can be added as the predetermined distance α.

[0033] The scanning area distance calculation unit 86 sets the scanning area on the image captured by the camera 5. The scanning area can be set by the user using the input unit 7, or the scanning area distance calculation unit 86 can automatically set the optimal scanning area based on the image captured by the camera 5.

[0034] The scanning area distance calculation unit 86 calculates the diameter Sa of the set scanning area. Then, the scanning area distance calculation unit 86 calculates the scanning area distance FCDs between the focal point F of the radiation source 2 required in the set scanning area and the center of the object A under inspection.

[0035] The comparison unit 87 calculates the limit distance FCD by the limit distance calculation unit 85. L The scanning area distances (FCDs) calculated by the scanning area distance calculation unit 86 are compared to determine the imaging distance (FCD) at each rotation angle. The imaging distance (FCD) refers to the distance between the focal point F of the radiation source 2 and the center of the object A being inspected during actual imaging. More specifically, the comparison unit 87 determines the limiting distance (FCD). L Minimum distance FCD Lmin and maximum distance FCD Lmax Compare with FCDs in terms of scanned area distance. Minimum distance FCD Lmin This refers to the extreme distance of the FCD rotation angle from 0 degrees to 360 degrees. L The shortest distance. Maximum distance FCD Lmax This refers to the extreme distance of the FCD rotation angle from 0 degrees to 360 degrees. L The longest distance. The comparison unit 87 determines the distance FCD during rotation based on the comparison result and sends the determined shooting distance FCD to the inspection table control unit 81. Furthermore, when the FCD is at its maximum distance... L When a predetermined distance α is added, the comparison unit 87 compares the distance obtained by adding the predetermined distance α with the scanning area distance FCDs to determine the shooting distance FCD.

[0036] The magnification calculation unit 88 calculates the magnification based on the shooting distance FCD determined by the comparison unit 87. Specifically, during shooting, the magnification calculation unit 88 calculates the magnification even when the distance FCD changes, ensuring that the magnification of the captured image remains the same. The magnification calculation unit 88 calculates the magnification based on the minimum shooting distance FCDmin, which is the shortest shooting distance FCD, ensuring that the magnification at each rotation angle is the same as the minimum shooting distance FCDmin.

[0037] [action] Next, use Figure 4 The flowchart below explains the calculation of the imaging distance FCD in this embodiment. First, the CT device 100 acquires a fluoroscopic image of the object being examined, A (step S01). The rotating stage 11 is rotated, and the object being examined is irradiated from all directions by the radiation source 2 with the radiation beam B, thereby acquiring a fluoroscopic image.

[0038] The obtained perspective image is displayed on display unit 6. For example... Figure 5 As shown, the perspective image is displayed as an ellipse. The user draws a rectangle ROI that is circumscribed by the perspective image displayed on the display unit 6 (step S02).

[0039] The extreme distance calculation unit 85 calculates the number of pixels dg from the rotation center at a rotation angle of 0 degrees to the end of the ROI based on the rectangular ROI (step S03). Then, the extreme distance calculation unit 85 calculates the distance from the end of the ROI based on the number of pixels dg. Figure 6 The distance d from the rotation axis C shown to the end of the object being inspected A (the end at 90 degrees and the front side of the irradiated radiation beam). The limit distance calculation unit 85 calculates the distance d (mm) using the following formula (1). This distance d becomes the limit distance FCD. L (Step S04).

[0040] (Mathematical Formula 1) d = dg·dpm…(1) dpm: Size per pixel

[0041] The limit distance calculation unit 85 calculates the limit distance FCD for the inspected object A in all directions, from a rotation angle of 0 degrees to 360 degrees. L The calculation is performed. In this embodiment, the limit distance calculation unit 85 calculates the limit distance FCD at 45-degree intervals. L .like Figure 7 As shown in the chart, the limit distance calculation unit 85 calculates the limit distance FCD from a rotation angle of 0 degrees to 360 degrees. L Furthermore, the limiting distance FCD is calculated. L The smaller the spacing of the rotation angles, the better. That is, calculate the limiting distance FCD. L The spacing of the rotation angles is preferably 45 degrees compared to a 90-degree spacing. The limiting distance FCD is calculated by using a smaller spacing of rotation angles. L It can calculate the dimensions of the inspected object A with high accuracy.

[0042] However, as Figure 6 As shown, the limiting distance FCD calculated as described above L This is the distance calculated when the target is located at a 90-degree angle to the beam of radiation. Therefore, in order to determine the FCD's calculated limit distance... L The corresponding part of the object being inspected, A, needs to be positioned opposite the radiation source 2, offset by 90 degrees. If... Figure 7 If the chart is offset by 90 degrees, it becomes Figure 8 That way.

[0043] The limit distance calculation unit 85 calculates the limit distance FCD. L Add a predetermined distance α (step S05). Regarding the predetermined distance α, in order to set the distance between the focal point F of the radiation source 2 and the window of the radiation source 2, and to set several gaps between the radiation source 2 and the object A being inspected, the predetermined distance α is pre-stored in a storage unit (not shown). If at the limit distance FCD... L Adding a specified distance α, then as follows Figure 9 As shown, a predetermined distance α is added at each rotation angle. The limit distance calculation unit 85 uses the distance obtained by adding the predetermined distance α as the limit distance FCD. L .

[0044] Next, the scanning area calculation unit 86 sets the scanning area (step S06). For example, as... Figure 10 As shown, the scanning area distance calculation unit 86 sets a circular scanning area S on the image captured by the camera 5. The scanning area distance calculation unit 86 calculates the diameter Sa of the scanning area S. The diameter Sa (mm) can be calculated based on the number of pixels in the image.

[0045] Then, the scanning area distance calculation unit 86 calculates the scanning area distance FCDs based on the diameter Sa and the following formula (2) (step S07).

[0046] (Mathematical Formula 2) D: The longitudinal length of detector 3 FDD: Distance between the focal point F of radiation source 2 and detector 3

[0047] Furthermore, steps S06 and S07 do not necessarily need to be performed after steps S01 to S05. That is, steps S06 and S07 can be performed before steps S01 to S05, or they can be performed simultaneously with steps S01 to S05.

[0048] When the extreme distance FCD L When the calculation of the distance between the scanning area and the FCDs is completed, the comparison unit 87 will set the limit distance FCD. L The distance to the scanned area FCDs is compared (step S08). The comparison unit 87 compares the extreme distance FCDs. L Minimum distance FCD Lmin and maximum distance FCD Lmax Compare with the distance of the scanned area to FCDs.

[0049] The comparison unit 87 determines the shooting distance FCD based on the comparison result (step S09). For example... Figure 11 As shown, the scanning area is at its maximum distance from the FCDs. Lmax In the above cases, if the extreme distance FCD is... L If the shooting distance is set to FCD, then the scanning area S becomes smaller. Therefore, the comparison unit 87 determines the distance of the scanning area from FCDs as the shooting distance, i.e., the shooting distance FCD (reference). Figure 11 (thick solid line). In this case, since the shooting distance FCD is constant, the object A being inspected will not approach or move away from the radiation source 2 during the shooting.

[0050] On the other hand, such as Figure 12 As shown, the minimum distance between the scanned area and the FCDs is [missing information]. Lmin In the following cases, if the scanning area distance FCDs is set to the imaging distance FCD, the object A under inspection will come into contact with the radiation source 2. Therefore, the comparison unit 87 will set the limit distance FCD. L Determined as the shooting distance FCD (reference) Figure 12 (thick solid line).

[0051] In addition, such as Figure 13 As shown, the scanned area distance from FCDs is greater than the minimum distance from FCDs. Lmin Longer than the maximum distance FCD Lmax In the short case, if only the extreme distance FCD is considered... L If the scanning area is taken as the distance from any of the FCDs, then depending on the rotation angle, the object A under inspection will come into contact with the radiation source 2, or the scanning area S will become smaller. Therefore, the comparison unit 87 determines the limiting distance FCD. L For the portion of the scanning area below the FCDs, the scanning area distance FCDs is defined as the shooting distance FCD. For the extreme distance FCD... L For the portion of the scanned area above FCDs, the limit distance FCDs will be [defined]. L Determined as the shooting distance FCD (reference) Figure 13 (The thick solid line). That is, at the extreme distance FCD L For the portion of the scanning area below the FCDs, the shooting distance to the FCD is constant; at the extreme distance of the FCD... L For the portion of the scanning area above the FCDs, the shooting distance of the FCD is determined according to the limit distance of the FCD. L And change.

[0052] When the shooting distance FCD is determined, the magnification calculation unit 88 calculates the magnification (step S10). For example... Figure 12 , Figure 13 As shown, when the shooting distance FCD changes with the rotation of the rotary stage 11, the size of the generated perspective image varies depending on the rotation angle. Therefore, the magnification calculation unit 88 calculates the magnification at each rotation angle based on the shooting distance FCD.

[0053] Specifically, the magnification calculation unit 88 calculates the magnification at each rotation angle, such that the magnification at the shooting distance FCD is the same as that at the shortest shooting minimum distance FCDmin. The magnification calculation unit 88 calculates the magnification based on the following formula (3). Therefore, as Figure 14 As shown, smaller perspective images are also magnified, enabling the generation of perspective images of the same size. Furthermore, as... Figure 11As shown, when the shooting distance FCD is constant, the magnification calculation unit 88 does not need to calculate the magnification.

[0054] (Mathematical Formula 3) Magnification = Shooting distance FCD / Minimum shooting distance FCDmin ... (3)

[0055] When the magnification calculation is completed, the imaging begins (step S11). That is, the inspection stage control unit 81 controls the X mechanism 14 to reach the imaging distance FCD determined by the comparison unit 87. In other words, for the inspected object A with a high aspect ratio, the inspection stage control unit 81 controls the X mechanism 14 so that when the long side portion is arranged on the optical axis of the radiation beam B, the inspected object A is far away from the radiation source 2, and when the short side portion is arranged on the optical axis of the radiation beam B, the inspected object A is close to the radiation source 2.

[0056] When the imaging of the object A is completed, the reconstruction unit 83 generates a CT image based on the fluoroscopic image obtained in the 360-degree direction (step S13). At this time, the reconstruction unit 83 generates a fluoroscopic image and a CT image based on the magnification calculated by the magnification calculation unit 88.

[0057] [Effect] As described above, the CT apparatus 100 of this embodiment includes: an examination table 1 for placing a subject A and moving and rotating the subject A; a radiation source 2 for irradiating the subject A with a radiation beam B; a detector 3 disposed opposite to the radiation source 2 across the subject A; and a limit distance calculation unit 85 for calculating the limit distance FCD. L The limiting distance FCD L The minimum distance FCD between the focal point F of radiation source 2 and the center of the object A being inspected is the distance required to prevent the object A from contacting radiation source 2 during rotation. The scanning area distance calculation unit 86 calculates the scanning area distance FCDs, which is the distance between the focal point F of radiation source 2 and the center of the object A being inspected within the set scanning area S. The comparison unit 87 compares the minimum distance FCDs with the minimum distance FCDs. L The imaging distance FCD is determined by comparing the imaging distance FCD with the scanning area distance FCD; and the inspection table control unit 81 controls the inspection table 1 to move the object A to be inspected closer to or further away from the radiation source 2 during imaging, based on the imaging distance FCD determined by the comparison unit 87.

[0058] Thus, the CT device 100 of this embodiment not only determines the limit distance FCD corresponding to the shape of the object being examined A, but also... LThe imaging distance FCD is determined based on the required scanning area distance FCDs for the scanning area S. Therefore, the scanning area S does not become smaller, allowing imaging at the optimal imaging distance FCD. Consequently, high-quality CT images can be generated with optimal resolution.

[0059] The limit distance calculation unit 85 calculates the limit distance FCD. L The comparison unit 87 adds a predetermined distance α to the limit distance FCD obtained by adding the predetermined distance α. L The image capture distance of the FCD is determined by comparing it with the distance of the scanned area to the FCDs.

[0060] This creates a spatial margin of a predetermined distance α between the inspected object A and the radiation source 2. Therefore, it effectively prevents the inspected object A from contacting the radiation source 2 during rotation. Furthermore, when there is a certain distance between the focal point of the radiation source 2 and the window irradiating the radiation beam B, a predetermined distance α is set based on this distance, and this is achieved through the limit distance FCD. L Adding a specified distance α can prevent the inspected object A from coming into contact with the radiation source 2.

[0061] It also includes a magnification calculation unit 88, which calculates the magnification of the perspective image at each rotation angle. When the shooting distance FCD changes according to the rotation angle, the magnification calculation unit calculates the magnification so that the magnification is the same as the magnification of the perspective image taken at the shortest shooting distance FCDmin.

[0062] As the imaging distance FCD changes, the magnification of the fluoroscopic image of the object A being examined also changes. Therefore, the magnification calculation unit 88 calculates the magnification for each rotation angle based on the minimum imaging distance FCDmin. As a result, each fluoroscopic image becomes the same size, and a CT image can be generated based on this. In addition, since the resolution is highest (smallest pixel size) at the minimum imaging distance FCDmin, an image matching this high resolution can be generated.

[0063] [Variation Example]

[0064] (1) In the above embodiment, the user draws the tangent of the object A to be inspected on the perspective image, but the ROI can also be drawn automatically. That is, the limit distance calculation unit 85 can draw the ROI by performing image processing on the perspective image, and calculate the number of pixels dg based on the drawn ROI. As a result, the user's drawing can be omitted, thus improving productivity.

[0065] (2) In the above embodiment, the limit distance calculation unit 85 obtains the limit distance FCD by drawing the ROI on the perspective image and calculating values ​​such as the number of pixels dg. L However, calculations do not need to be based on perspective images. For example, the limiting distance FCD at various rotation angles. L Alternatively, the user can determine the area visually. In this case, the user also sets the scanning area visually. The comparison unit 87 considers the set values ​​as the limit distance FCD calculated by the limit distance calculation unit 85. L The scanning area distance FCDs are calculated by the scanning area distance calculation unit 86, and the imaging distance FCD is determined. Therefore, it is not necessary to create a fluoroscopic image before imaging, and thus no X-rays are required.

[0066] (3) It can also be applied to a spiral scanning method in which the object being inspected A is rotated and raised while being photographed continuously. This can shorten the shooting time.

[0067] (4) Figure 15 As shown, the inspection table 1 may have an XY stage 15 on top of the rotary table 11. The XY stage 15 holds the object to be inspected, A. The XY stage 15 moves the object to be inspected, A, in the X or Y direction. The XY stage 15 rotates as the rotary table 11 rotates. The inspection table control unit 81 controls the XY stage 15 based on the shooting distance FCD determined by the comparison unit 87, so as to move the object to be inspected, A.

[0068] Specifically, such as Figure 16 As shown, the XY stage 15 is used to align the rotation center Ac of the object being inspected A with the optical axis of the radiation beam irradiated from the radiation source 2, and the object being inspected A is moved to the imaging distance FCD. Specifically, as... Figure 16 As shown in (a), when the rotation angle is 0 degrees, the rotation center Ac of the inspected object A is coaxial with the rotation axis C. At this time, the long side of the inspected object A is parallel to the optical axis. When the rotary table 11 starts to rotate, the inspected object A rotates, causing the short side of the inspected object A to be parallel to the optical axis. Figure 16 As shown in (b), when the rotary table 11 rotates 45 degrees, the XY table 15 also rotates 45 degrees. At this time, the rotation center Ac of the object being inspected A is positioned closer to the radiation source 2 (at a distance of approximately half the radius from the rotation axis C towards the radiation source 2) compared to when the imaging distance FCD is 0 degrees of rotation. Then, as... Figure 16 As shown in (c), when the rotation angle is 90 degrees, the rotation center Ac of the object being inspected A is closest to the radiation source 2. That is, the imaging distance FCD becomes the minimum imaging distance FCDmin.

[0069] Furthermore, when rotating between 90 and 180 degrees, the rotation causes the long side of the object being inspected, A, to be parallel to the optical axis, thus... Figure 16 As shown in (d) and (e), the rotation center Ac of the object being inspected A is far from the radiation source 2, and is coaxial with the rotation axis C at a rotation angle of 180 degrees. Furthermore, when rotating from 180 degrees to 270 degrees, it rotates again, so that the short side of the object being inspected A is parallel to the optical axis, thus... Figure 16 As shown in (f) and (g), the rotation center Ac of the object A moves towards the radiation source 2. At a rotation angle of 270 degrees, it is closest to the radiation source 2, becoming the minimum imaging distance FCDmin. Between 270 and 360 degrees, the rotation causes the long side of the object A to be parallel to the optical axis, thus... Figure 16 As shown in (h) and (i), the rotation center Ac of the inspected object A moves away from the radiation source 2, returning to the position of 0 degrees rotation after a rotation angle of 360 degrees. When plotting the trajectory of the rotation center Ac of the inspected object A on the XY stage 15 from 0 degrees to 360 degrees rotation angle, as shown... Figure 17 As shown.

[0070] In this way, the position of the object A to be inspected can be moved without using the X mechanism 14, but rather through the XY worktable 15.

[0071] (5) The intervals of the rotation angles when capturing perspective images do not need to be equal and can vary depending on the shape of the object A being inspected. That is, for simple shapes in the object A, the intervals of the rotation angles can be increased by, for example, by 45 degrees, while for complex shapes, the intervals can be decreased by, for example, by 10 degrees. This allows for more accurate calculation of the dimensions of the object A and enables the generation of images with good image quality while preventing contact between the object A and the radiation source 2. Furthermore, for example, increasing the intervals of the rotation angles for simple shapes has little impact on image quality. Therefore, the overall number of views can be reduced, thus shortening the scanning time.

[0072] (Other implementation methods) This specification describes embodiments of the invention, but these embodiments are provided as examples and are not intended to limit the scope of the invention. The embodiments described above can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the claims and their equivalents.

Claims

1. A CT device, wherein the CT device performs imaging while rotating the object being examined, characterized in that, The CT device includes: An inspection table, which holds the object to be inspected and allows the object to be inspected to move and rotate; A radiation source that irradiates the object under inspection with a beam of radiation. The detector is positioned opposite the radiation source, with the object being inspected in between; Limit distance calculation unit, calculates the limit distance FCD L The limiting distance FCD L It is the minimum distance required in the distance FCD between the focal point of the radiation source and the center of the object being inspected so that the object being inspected does not come into contact with the radiation source during rotation; The scanning area distance calculation unit calculates the scanning area distance FCDs, which is the distance between the focal point of the radiation source required in the set scanning area and the center of the object being inspected. The comparison unit will compare the limit distance FCD. L The distance to the FCDs is compared with the distance to the scanning area to determine the shooting distance of the FCDs at the time of shooting; and The inspection table control unit, during imaging, controls the inspection table to move the object being inspected closer to or further away from the radiation source based on the imaging distance determined by the comparison unit.

2. The CT device according to claim 1, characterized in that, The limiting distance calculation unit calculates the limiting distance FCD based on the size of the ROI tangent to the drawn perspective image. L .

3. The CT device according to claim 2, characterized in that, The ROI is drawn by the extreme distance calculation unit.

4. The CT device according to any one of claims 1 to 3, characterized in that, The limit distance calculation unit calculates the limit distance FCD. L Add a pre-set distance above; The comparison unit will be at the extreme distance FCD L The distance obtained by adding the specified distance to the image is compared with the scanning area distance FCDs to determine the shooting distance.

5. The CT device according to any one of claims 1 to 3, characterized in that, The CT device also includes a magnification calculation unit, which calculates the magnification of the fluoroscopic image at each rotation angle. When the shooting distance changes according to the rotation angle, the magnification calculation unit calculates the magnification so that the magnification is the same as that of the perspective image taken at the shortest distance in the shooting distance.

Images