CT device

Abstract

It achieves optimal resolution by realizing FCD (Field Control Diode) according to the shape of the object being inspected and the set scan area. [Solution] The CT scanner comprises an examination table 1, a radiation source 2, a detector, and a control unit 8. The control unit determines the critical distance FCD, which is the minimum distance required to prevent the object under examination from coming into contact with the radiation source during rotation, at the distance FCD between the focal point F of the radiation source and the center of the object under examination. L A limit distance calculation unit 85 calculates the limit distance FD, and a scan area distance calculation unit 86 calculates the scan area distance FCDs, which is the distance between the focal point F of the radiation source and the center of the object under inspection in the set scan area S, and the limit distance FCD L The system includes a comparison unit 87 that compares the scan area distance FCDs with the imaging distance FCD to determine the imaging distance FCD, and an inspection table control unit 81 that controls the inspection table to move the object to be inspected closer to or further away from the radiation source 2 based on the imaging distance FCD determined by the comparison unit 87 during imaging.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a CT scanner. [Background technology]

[0002] Industrial CT scanners, used to inspect small electronic components such as lithium-ion batteries with high resolution, are widely used. These CT scanners consist of a radiation source that emits radiation, such as an X-ray beam, and a detector that detects the X-ray beam with two-dimensional resolution, positioned opposite each other. A rotatable inspection platform is located between the radiation source and the detector. The object to be inspected is placed on the inspection platform and rotates during scanning, irradiating it with radiation from all directions.

[0003] Generally, the focal point distance (FCD) is the distance between the focal point of the radiation source and the rotational center of the object being examined. A shorter FCD results in higher resolution, so imaging is sometimes performed by bringing the object being examined as close to the radiation source as possible.

[0004] When the object being photographed has a high aspect ratio shape, such as a rectangle or ellipse, if the shorter side faces the radiation source, the object can be brought closer to the radiation source, while if the longer side faces the radiation source, it needs to be moved away. Therefore, it is necessary to understand the shape of the object being photographed and change the FCD during photography according to that shape. A known method involves calculating the dimension d from the center of rotation of the object A to its end, and adjusting the object's proximity to the radiation source according to this dimension d. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-71371 [Overview of the project] [Problems that the invention aims to solve]

[0006] On the one hand, when performing imaging, a scan area is set in advance. The required FCDs need to be calculated separately from the shape of the inspected object according to the size of the set scan area. When this FCDs exceeds the dimension d of the inspected object, if the FCD is controlled according to the dimension d of the inspected object, there will be a problem that the scan area becomes smaller.

[0007] The embodiment of the present invention is made to solve the above problems, and its object is to provide a CT apparatus that realizes an FCD according to the shape of the inspected object and the set scan area and realizes an optimal resolution.

Means for Solving the Problems

[0008] The CT apparatus in the embodiment of the present invention is a CT apparatus that performs imaging while rotating an inspected object, and includes an inspection table on which the inspected object is placed and that moves and rotates the inspected object, a radiation source that irradiates the inspected object with a radiation beam, a detector provided opposite to the radiation source with the inspected object interposed therebetween, and a limit distance FCD that is the minimum distance required for the inspected object not to contact the radiation source during rotation of the inspected object at a distance FCD between the focal point of the radiation source and the center of the inspected object L a limit distance calculation unit that calculates the limit distance FCD, a scan area distance calculation unit that calculates scan area distances FCDs that are the distances between the focal point of the radiation source and the center of the inspected object required in the set scan area, and the limit distance FCD L a comparison unit that compares the limit distance FCD with the scan area distances FCDs to determine a shooting distance that becomes the distance FCD during imaging, and an inspection table control unit that controls the inspection table to move the inspected object closer to and away from the radiation source based on the shooting distance determined by the comparison unit during imaging.

Brief Description of the Drawings

[0009] [Figure 1] It is a side view schematically showing the CT apparatus of the embodiment. [Figure 2] It is a plan view schematically showing the CT apparatus of the embodiment. [Figure 3] This is a block diagram showing the configuration of the control unit. [Figure 4] This is a flowchart showing the method for calculating the shooting distance FCD in the embodiment. [Figure 5] This diagram shows the ROI set on a perspective image. [Figure 6] This diagram shows the distance from the center of rotation of the object under inspection to its end. [Figure 7] This graph shows the relationship between the critical distance FCDL and the rotation angle. [Figure 8] This graph shows the relationship between the limit distance FCDL and the rotation angle when the graph in Figure 7 is shifted by 90 degrees. [Figure 9] This graph shows the relationship between the rotation angle and the limit distance FCDL when a predetermined distance is added. [Figure 10] This diagram shows the settings for the scan area. [Figure 11] This graph shows the scanning distance when the scan area distance FCDs is longer than the maximum value of the limit distance FCDL. [Figure 12] This graph shows the shooting distance when the scan area distance FCDs is shorter than the minimum value of the limit distance FCDL. [Figure 13] This graph shows the shooting distance when the scan area distance FCDs is between the minimum and maximum values ​​of the limit distance FCDL. [Figure 14] This figure shows the perspective image 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 showing a modified CT scanner. [Figure 16] This diagram shows how the object being inspected is moved in the modified form. [Figure 17] This figure shows the trajectory of the movement of the center of rotation of the object under inspection in a modified case. [Modes for carrying out the invention]

[0010] [Embodiment] The CT apparatus according to the embodiment will be described in detail below with reference to the drawings. Figure 1 is a schematic side view showing the CT apparatus of the embodiment. Figure 2 is a schematic top view showing the CT apparatus of the embodiment.

[0011] The CT scanner 100 is a device used for non-destructive testing of an object A to be inspected. The CT scanner 100 irradiates the object A to be inspected with a radiation beam B that penetrates the object A and detects the amount of radiation attenuated by the radiation passing through the object A. Based on this detection result, it generates a CT image, which is a cross-sectional image of the object A to be inspected. The CT scanner 100 also generates a 3D image from the multiple CT images that have been generated. The object A to be inspected is a shape with a high aspect ratio, for example, a cylindrical shape that is elliptical when viewed from the direction of the rotation axis C. In this embodiment, during imaging, the object A to be inspected is moved closer to and further away from the radiation source 2 according to the shape of the object A to be inspected.

[0012] As shown in Figure 1, the CT scanner 100 comprises 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 table having a mounting surface on which the object to be examined A is placed. The examination table 1 is movable in a direction parallel to or perpendicular to the mounting surface. The examination table 1 is also rotatable with a rotation axis C perpendicular to the mounting surface. During imaging, the examination table 1 rotates and moves the object to be examined A. The examination table 1 has a rotary table 11, a lifting mechanism 12, a Y mechanism 13, and an X mechanism 14.

[0013] The rotary table 11 is used to place the object to be inspected A. The object to be inspected A is placed on the rotary table 11 such that the rotation axis C of the rotary table 11 is coaxial with the center of the object to be inspected A. The rotary table 11 is composed of an actuator that includes a drive source such as a motor, and is rotatably mounted with the rotation axis C perpendicular to the mounting surface. While the radiation beam B is irradiating, the rotary table 11 rotates, so that the radiation beam B is irradiated in all directions on the object to be inspected A. Alternatively, a sample table may be placed on the rotary table 11, and the object to be inspected A may be placed on the sample table.

[0014] The lifting mechanism 12 is located beneath the rotary table 11. The lifting mechanism 12 can utilize a ball screw mechanism driven by a servo motor. The lifting mechanism 12 is movable in a direction perpendicular to the mounting surface. That is, the height of the object A under inspection can be adjusted by moving the lifting mechanism 12 in a direction perpendicular to the mounting surface.

[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 movable in a direction parallel to the mounting surface and perpendicular 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 movable 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 moving the object under inspection A with the X mechanism 14, the object under inspection A is moved closer to and further away from the radiation source 2.

[0017] The radiation source 2, for example, irradiates the object A under inspection with a radiation beam B that penetrates it. The radiation beam B is a beam of radiation that spreads out in a conical shape with a fan angle and a cone angle, 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 microfocus X-ray tube or a nanofocus X-ray tube, and the radiation beam B is an X-ray beam. Note that the radiation beam B is not limited to an X-ray beam; any beam that penetrates the object A under inspection, such as gamma rays, can be used. The radiation source 2 is supported by a support frame 21. The radiation source 2 is movable in the X direction by an X mechanism 14.

[0018] The detector 3 is positioned opposite the radiation source 2, with the inspection table 1 and the object under inspection A in between. The detector 3 is positioned so that the center of its imaging area coincides with the optical axis of the radiation source 2. The detector 3 detects the two-dimensional distribution of attenuated radiation intensity according to the transmission path of the radiation beam B and outputs a fluoroscopic image. The detector 3 is composed of, for example, a flat panel detector (FPD). The detector 3 is supported by a support frame 31. The distance of the detector 3 from the object under inspection A is adjusted by the X mechanism 14.

[0019] The filter section 4 is positioned between the object under inspection A and the radiation source 2, close to the radiation source 2. The filter section 4 is a thin plate-like member with a thickness of several millimeters. The filter section 4 is a metal plate made of copper, aluminum, iron, or an alloy containing these materials. Multiple filter sections 4 are provided, and each filter section 4 differs in material and thickness.

[0020] The filter unit 4 is provided to be movable by 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 filter unit 4 selected by the user along the optical axis of the radiation source 2. The radiation beam B is irradiated onto the filter unit 4 positioned on the optical axis, and the radiation beam B that has passed through the filter unit 4 is irradiated onto the object A under inspection. By allowing the radiation to pass through the filter unit 4, the occurrence of metal artifacts is suppressed.

[0021] Furthermore, the CT apparatus 100 may be equipped with a collimator (not shown). A collimator is a device that restricts the path and incident area of ​​the radiation beam B. The collimator is made of a material with high specific gravity and high shielding ability, such as tungsten or molybdenum. The collimator is installed between the radiation source 2 and the object under inspection A, symmetrically positioned vertically with respect to 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 under inspection A in between. Camera 5 is, for example, a CCD camera. Camera 5 photographs the object under inspection A from above.

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

[0024] The input unit 7 can use a keyboard, mouse, touch panel, etc. The input unit 7 accepts various operations such as selecting a menu for actual shooting or test shooting, adjusting the shooting time and shooting conditions, manually operating the movement mechanism, starting shooting, and selecting the area of ​​the object A to be observed.

[0025] The control unit 8 consists of a computer and driver circuits. The computer consists of storage such as an HDD or SSD, RAM, a CPU, etc. The control unit 8 controls each component of the CT device 100. The control unit 8 is connected to the input unit 7, and the user causes the control unit 8 to control each component of the CT device 100 via the input unit 7.

[0026] Figure 3 is a block diagram showing the configuration of the control unit 8. As shown in Figure 3, the control unit 8 includes an examination 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 scan area distance calculation unit 86, a comparison unit 87, and a magnification factor 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. The inspection table control unit 81 controls the object under inspection A placed on the inspection table 1 to align with the optical axis of the radiation beam B, and allows the object under inspection A to rotate 360 ​​degrees while the radiation beam B is irradiated. Furthermore, by moving the inspection table 1 under the control of the inspection table control unit 81, the distance FCD between the focal point F of the radiation source 2 and the center of the object under inspection A is adjusted. In other words, during imaging, the object under inspection 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 during imaging to change the distance FCD.

[0028] The radiation source control unit 82 controls the radiation source 2 to irradiate the object A under inspection with the radiation beam B. That is, the inspection table control unit 81 and the radiation source control unit 82 control the radiation beam B to irradiate the object A under inspection in all directions.

[0029] The reconstruction unit 83 reconstructs the CT imaging area encompassed by the radiation beam B based on fluoroscopic images obtained in a 360-degree direction for a number of views. The reconstruction unit 83 transmits the fluoroscopic images to the limit distance calculation unit 85. If the magnification calculation unit 88 has calculated the magnification, the reconstruction unit 83 reconstructs the image based on that magnification. The reconstruction unit 83 reconstructs multiple cross-sectional images arranged continuously at equal intervals in a direction perpendicular to the mounting surface of the object under inspection A, and forms 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 the like.

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

[0031] The limit distance calculation unit 85 calculates the limit distance FCD based on the fluoroscopic image of the object A under inspection. L Calculate the limit distance FCD. LThis is the minimum distance required to prevent the test object A from contacting the radiation source 2 during rotation at the distance FCD. The limit distance calculation unit 85 calculates the limit distance FCD for 360 degrees of the test object A. L It calculates.

[0032] The limit distance calculation unit 85 may add a predetermined distance α to the calculated limit distance FCD. For example, if there is a distance from the focal point F of the radiation source 2 to the window of the radiation source 2 from which the radiation is emitted, this length may be added as the predetermined distance α. Also, in order to form a slight gap between the radiation source 2 and the test object A, the length corresponding to this gap may be added as the predetermined distance α. L

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

[0034] The scan area distance calculation unit 86 calculates the diameter Sa of the set scan area. Then, the scan area distance calculation unit 86 calculates the scan area distance FCDs from the focal point F of the radiation source 2 to the center of the test object A required in the set scan area.

[0035] The comparison unit 87 compares the limit distance FCD calculated by the limit distance calculation unit 85 L with the scan area distance FCDs calculated by the scan area distance calculation unit 86 to determine the shooting distance FCD at each rotation angle. The shooting distance FCD is the distance from the focal point F of the radiation source 2 to the center of the test object A when actually shooting. More specifically, the comparison unit 87 compares the minimum distance FCD L And the maximum distance FCD Lmin With the scan area distance FCDs. The minimum distance FCD Lmax Is the limit distance FCD for rotation angles 0 degrees to 360 degrees Lmin L ​This refers to the shortest distance among them. Maximum distance FCD Lmax This refers to the limit distance FCD of rotation angles from 0 to 360 degrees. L This refers to the longest distance among them. The comparison unit 87 determines the rotational distance FCD based on the comparison result and transmits the determined shooting distance FCD to the inspection table control unit 81. The comparison unit 87 also refers to the limit distance FCD. L If a predetermined distance α is added to the distance, the scanning distance FCD is determined by comparing the distance with the predetermined distance α added to the scanning distance FCDs.

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

[0037] [Operation] Next, the calculation of the imaging distance FCD in this embodiment will be explained using the flowchart in Figure 4. First, the CT scanner 100 acquires a fluoroscopic image of the object A to be examined (step S01). The rotary table 11 is rotated, and the radiation beam B from the radiation source 2 is irradiated from all directions onto the object A to be examined, thereby acquiring a fluoroscopic image.

[0038] The acquired perspective image is displayed on the display unit 6. As shown in Figure 5, the perspective image is displayed as an ellipse. The user draws a rectangular ROI that circumscribing the perspective image displayed on the display unit 6 (step S02).

[0039] The limit distance calculation unit 85 calculates the number of pixels dg from the rotation center to the edge of the ROI at a rotation angle of 0 degrees, based on the rectangular ROI (step S03). Then, based on the number of pixels dg, the limit distance calculation unit 85 calculates the distance d from the rotation axis C shown in Figure 6 to the edge of the object under inspection A (the edge 90 degrees in front of where the radiation beam is irradiated). The limit distance calculation unit 85 calculates the distance d (mm) using the following formula (1). This distance d is the limit distance FCD. L This is what happens (Step S04).

[0040] (Equation 1) TIFF2026072249000002.tif17101dpm: Dimensions per pixel

[0041] The limit distance calculation unit 85 calculates the limit distance FCD for all directions of the object A under inspection, i.e., from a rotation angle of 0 degrees to 360 degrees. L The limit distance calculation unit 85 calculates the limit distance FCD at 45-degree intervals. L The limit distance calculation unit 85 calculates the limit distance FCD for rotation angles from 0 to 360 degrees, as shown in the graph in Figure 7. L Calculate the limit distance FCD. L The rotation angle pitch used to calculate the limit distance FCD is preferably fine. L For calculating the limit distance FCD, a rotation angle pitch of 45 degrees is preferable to a 90-degree interval, for example. L By calculating this, the dimensions of the object A under inspection can be calculated with high accuracy.

[0042] However, the limit distance FCD calculated as described above L This is the distance calculated when the position is 90 degrees in front of the radiation beam, as shown in Figure 6. Therefore, the limit distance FCD calculated at the position opposite the radiation source 2 is different. L For the object under inspection A to be positioned in the corresponding area, it needs to be shifted by 90 degrees. Shifting the graph in Figure 7 by 90 degrees results in Figure 8.

[0043] The limit distance calculation unit 85 calculates the limit distance FCD L A predetermined distance α is added (step S05). The predetermined distance α is stored in a memory unit (not shown) in advance to allow for a small gap between the focal point F of the radiation source 2 and the window of the radiation source 2 from which the radiation is emitted, as well as between the radiation source 2 and the object under inspection A. Limit distance FCD L When a predetermined distance α is added, the distance increases by the predetermined distance α at each rotation angle, as shown in Figure 9. The limit distance calculation unit 85 calculates the distance obtained by adding the predetermined distance α as the limit distance FCD. L Let's assume that.

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

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

[0046] (Equation 2) TIFF2026072249000003.tif25145D: Vertical length of detector 3 FDD: Distance between the focal point F of radiation source 2 and detector 3

[0047] Note that steps S06 and S07 do not necessarily have to be performed after steps S01 to S05. In other words, steps S06 and S07 may be performed before steps S01 to S05, or they may be performed concurrently with steps S01 to S05.

[0048] Limit Distance FCD L Once the calculation of the scan area distance FCDs is complete, the comparison unit 87 calculates the limit distance FCD LThe scan area distance FCDs are compared (step S08). The comparison unit 87 compares the limit distance FCD L Minimum distance FCD Lmin and maximum distance FCD Lmax Compare this with the scan area distance FCDs.

[0049] The comparison unit 87 determines the shooting distance FCD based on the comparison result (step S09). As shown in Figure 11, the scan area distances FCDs are the maximum distance FCD Lmax In the above cases, the limit distance FCD L If the scanning distance FCD is set to [value missing], the scan area S becomes smaller. Therefore, the comparison unit 87 determines the scanning area distance FCDs as the scanning distance FCD, which is the distance during scanning (see the thick solid line in Figure 11). In this case, since the scanning distance FCD is constant, the object under inspection A does not move closer to or further away from the radiation source 2 during scanning.

[0050] On the other hand, as shown in Figure 12, the scan area distance FCDs is the minimum distance FCD Lmin In the following case, if the scan area distance FCDs is set to the imaging distance FCD, the object under inspection A will come into contact with the radiation source 2. Therefore, the comparison unit 87 sets the limit distance FCD to L This is determined as the shooting distance FCD (see the thick solid line in Figure 12).

[0051] Furthermore, as shown in Figure 13, the scan area distance FCDs is the minimum distance FCD Lmin Longer than maximum distance FCD Lmax If shorter than, the limit distance FCD L If only one of the scan area distances FCDs is used as the imaging distance, depending on the rotation angle, the object under inspection A may come into contact with the radiation source 2, or the scan area S may become smaller. Therefore, the comparison unit 87 uses the limit distance FCD L For the portion where the scan area distance FCDs is less than or equal to the scan area distance FCDs, the scan area distance FCDs is determined as the shooting distance FCD, and the limit distance FCD L The portion where the scan area distance is greater than or equal to the FCDs is the limit distance FCD LThis is determined as the shooting distance FCD (see the thick solid line in Figure 13). That is, the limit distance FCD L In the portion where the scan area distance FCDs is less than or equal to the limit distance FCD, the shooting distance FCD is constant, and the limit distance FCD L In the portion where the scan area distance is greater than or equal to FCDs, the limit distance FCD L The shooting distance FCD changes based on this.

[0052] Once the shooting distance FCD is determined, the magnification calculation unit 88 calculates the magnification (step S10). As shown in Figures 12 and 13, if the shooting distance FCD changes with the rotation of the rotary table 11, the size of the perspective image generated will differ depending on the rotation angle. Therefore, the magnification calculation unit 88 calculates the magnification for each rotation angle, taking into account the shooting distance FCD.

[0053] Specifically, the magnification calculation unit 88 calculates the magnification at each rotation angle so that it is the same as the magnification at the shortest shooting distance FCD, which is FCDmin. The magnification calculation unit 88 calculates the magnification based on the following formula (3). Therefore, as shown in Figure 14, even small-scale perspective images are magnified, and perspective images of the same size can be generated. Note that, as shown in Figure 11, when the shooting distance FCD is constant, the magnification calculation unit 88 does not need to calculate the magnification.

[0054] (Equation 3) TIFF2026072249000004.tif23148

[0055] Once the magnification calculation is complete, imaging begins (step S11). That is, the inspection table control unit 81 controls the X mechanism 14 so that the imaging distance FCD is determined by the comparison unit 87. In other words, for an object A with a high aspect ratio, the inspection table control unit 81 controls the X mechanism 14 so that when the long side is positioned on the optical axis of the radiation beam B, the object A moves away from the radiation source 2, and when the short side is positioned on the optical axis of the radiation beam B, the object A moves closer to the radiation source 2.

[0056] Once imaging of the object A to be examined is complete, the reconstruction unit 83 generates a CT image based on the fluoroscopic images obtained in a 360-degree direction (step S13). At this time, the reconstruction unit 83 generates the fluoroscopic image and then the 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 comprises an inspection table 1 on which the object to be inspected A is placed and on which the object to be inspected A is moved and rotated, a radiation source 2 that irradiates the object to be inspected A with a radiation beam B, a detector 3 provided opposite the radiation source 2 with the object to be inspected A in between, and a limit distance FCD which is the minimum distance required so that the object to be inspected A does not come into contact with the radiation source 2 while rotating, at the distance FCD between the focal point F of the radiation source 2 and the center of the object to be inspected A. L A limit distance calculation unit 85 calculates the limit distance FCD, and a scan area distance calculation unit 86 calculates the scan area distance FCDs, which is the distance between the focal point F of the radiation source 2 and the center of the object A to be inspected in the set scan area S, and the limit distance FCD L The system includes a comparison unit 87 that compares the scan area distance FCDs with the imaging distance FCD to determine the imaging distance FCD, and an inspection table control unit 81 that controls the inspection table 1 during imaging to move the object to be inspected A closer to or further away from the radiation source 2 based on the imaging distance FCD determined by the comparison unit 87.

[0058] Thus, the CT apparatus 100 of this embodiment has a limit distance FCD corresponding to the shape of the object A to be inspected. L Furthermore, the imaging distance FCD is determined not only by the scan area S itself, but also by taking into account the scan area distance FCDs required for the scan area S. Therefore, imaging can be performed at the optimal imaging distance FCD without reducing the scan area S. Consequently, high-quality CT images can be generated with optimal resolution.

[0059] The limit distance calculation unit 85 calculates the limit distance FCD L A predetermined distance α is added to the limit distance FCD, and the comparison unit 87 determines the limit distance FCD after adding the predetermined distance α. L The shooting distance FCD is determined by comparing it with the scan area distance FCDs.

[0060] This creates a spatial gap of a predetermined distance α between the object under inspection A and the radiation source 2. Therefore, it effectively prevents the object under inspection A from coming into contact with the radiation source 2 during rotation. Furthermore, if there is a certain distance between the focal point of the radiation source 2 and the window into which the radiation beam B is irradiated, the predetermined distance α is set based on this distance, and the limit distance FCD is set. L By adding a predetermined distance α, contact between the object under inspection A and the radiation source 2 can be prevented.

[0061] The system further includes a magnification calculation unit 88 that calculates the magnification of the fluoroscopic image at each rotation angle. When the shooting distance FCD changes with the rotation angle, the magnification calculation unit calculates the magnification so that it is the same as the magnification of the fluoroscopic image taken at the shortest shooting distance FCDmin.

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

[0063] [Differentiation]

[0064] (1) In the above embodiment, the user drew the circumscribing of the object A under inspection on the perspective image, but the ROI drawing may be performed automatically. That is, the limit distance calculation unit 85 may draw the ROI by image processing the perspective image and calculate the number of pixels dg based on this drawn ROI. This eliminates the need for the user to draw, thus improving productivity.

[0065] (2) In the above embodiment, the limit distance calculation unit 85 draws ROI on the perspective image and calculates various values ​​such as the number of pixels dg, and the limit distance FCD LAlthough this was determined, it is not necessary to calculate it based on perspective images. For example, the limit distance FCD at each rotation angle. L The user may determine this visually. In this case, the user also sets the scan area visually. The comparison unit 87 compares each set value with the limit distance FCD calculated by the limit distance calculation unit 85. L The scan area distance FCDs calculated by the scan area distance calculation unit 86 are taken as such, and the imaging distance FCD is determined. This eliminates the need to create a fluoroscopic image before imaging, thus eliminating the need to emit X-rays.

[0066] (3) This method may also be applied to a helical scan system in which the object A under inspection is rotated and raised and lowered while being continuously photographed. This can shorten the shooting time.

[0067] (4) The inspection table 1 may have an XY table 15 on a rotary table 11, as shown in Figure 15. The XY table 15 is on which the object to be inspected A is placed. The XY table 15 moves the object to be inspected A in the X direction or the Y direction. The XY table 15 rotates in conjunction with the rotation of the rotary table 11. The inspection table control unit 81 controls the XY table 15 to move the object to be inspected A based on the imaging distance FCD determined by the comparison unit 87.

[0068] Specifically, as shown in Figure 16, the XY table 15 is used to move the object under inspection A so that its rotation center Ac is on the optical axis of the radiation beam emitted from the radiation source 2, while the object under inspection A is moved to achieve the imaging distance FCD. Specifically, as shown in Figure 16(a), when the rotation angle is 0 degrees, the rotation center Ac of the object under inspection A is located coaxially with the rotation axis C. At this time, the long side of the object under inspection A is positioned parallel to the optical axis. When the rotation of the rotary table 11 begins, the object under inspection A rotates so that its short side is parallel to the optical axis. As shown in Figure 16(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 under inspection is positioned closer to the radiation source 2 than when the imaging distance FCD is 0 degrees (closer to the radiation source 2 by a distance of 1 / 2 of the radius from the rotation axis C). Then, as shown in Figure 16(c), when the rotation angle reaches 90 degrees, the rotation center Ac of the object under inspection A is closest to the radiation source 2. That is, the imaging distance FCD becomes the minimum imaging distance FCDmin.

[0069] Then, between rotation angles of 90 and 180 degrees, the object under inspection A rotates so that its long side is parallel to the optical axis. As shown in Figures 16(d) and (e), the rotation center Ac of object under inspection A moves away from the radiation source 2 and is positioned coaxially with the rotation axis C at a rotation angle of 180 degrees. Furthermore, between rotation angles of 180 and 270 degrees, the object under inspection A rotates again so that its short side is parallel to the optical axis. As shown in Figures 16(f) and (g), the rotation center Ac of object under inspection A moves in a direction toward the radiation source 2, and at a rotation angle of 270 degrees, it is closest to the radiation source 2, resulting in the minimum imaging distance FCDmin. Between rotation angles of 270 and 360 degrees, the object under inspection A rotates so that its long side is parallel to the optical axis. As shown in Figures 16(h) and (i), the rotation center Ac of object under inspection A moves away from the radiation source 2 and returns to the position of 0 degrees rotation at a rotation angle of 360 degrees. When the trajectory of the rotation center Ac of the object under inspection A on the XY table 15 is plotted at rotation angles from 0 to 360 degrees, the result is as shown in Figure 17.

[0070] Thus, instead of moving the position of the object A under inspection by the X mechanism 14, the object A under inspection may be moved by the XY table 15.

[0071] (5) The rotation angle pitch when capturing fluoroscopic images does not need to be at equal intervals and may be varied according to the shape of the object A under inspection. That is, for simple shapes of object A under inspection, the rotation angle pitch may be larger, for example, 45 degrees, and for complex shapes, the rotation angle pitch may be smaller, for example, 10 degrees. This allows for more accurate calculation of the dimensions of object A under inspection and enables the generation of high-quality images while preventing contact between object A under inspection and the radiation source 2. Furthermore, for example, for simple shapes, increasing the rotation angle pitch has little effect on image quality. Therefore, the total number of views can be reduced, and thus the scanning time can be shortened.

[0072] (Other embodiments) While embodiments of the present invention have been described herein, these embodiments are presented as examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. Embodiments and their variations are included in the scope and essence of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0073] 100 CT equipment 1. Examination table 11 Rotating Table 12 Lifting mechanism 13 Y mechanism 14X mechanism 2 Radiation source 21 Support frame 3 Detectors 31 Support frame 4. Filter section 5 Cameras 6 Display section 7 Input section 8 Control Unit 81 Inspection Table Control Unit 82 Radiation Source Control Unit 83 Reconstruction part 84 Camera Control Unit 85 Limit Distance Calculation Unit 86 Scan Area Distance Calculation Unit 87 Comparison Section 88 Magnification Calculation Unit

Claims

1. A CT scanner that takes images while rotating the object to be examined, An inspection table on which the object to be inspected is placed, and on which the object to be inspected is moved and rotated, A radiation source that irradiates the object to be inspected with a radiation beam, A detector is provided facing the radiation source with the object to be inspected in between, The critical distance FCD is the minimum distance required to prevent the object under inspection from coming into contact with the radiation source during rotation, in the distance FCD between the focal point of the radiation source and the center of the object under inspection. Ｌ A limit distance calculation unit that calculates the limit distance, A scan area distance calculation unit calculates scan area distances FCDs, which are the distances between the focal point of the radiation source and the center of the object under inspection within the set scan area. The aforementioned limit distance FCD Ｌ A comparison unit that compares the scan area distances FCDs with the distance FCD used when taking a picture to determine the shooting distance, During imaging, the inspection table control unit controls the inspection table to move the object to be inspected closer to or further away from the radiation source based on the imaging distance determined by the comparison unit, A CT scanner equipped with [a specific feature / feature].

2. The limit distance calculation unit calculates the limit distance FCD based on the dimensions of the ROI that circumscribes the drawn perspective image. Ｌ A CT apparatus according to claim 1 for calculating [value].

3. The CT apparatus according to claim 2, wherein the ROI is drawn by the limit distance calculation unit.

4. The limit distance calculation unit calculates the limit distance FCD Ｌ Add a predetermined distance to this, The comparison unit is the limit distance FCD. Ｌ A CT apparatus according to any one of claims 1 to 3, wherein the imaging distance is determined by comparing the distance obtained by adding the predetermined distance to the imaging distance with the scan area distances FCDs.

5. The system further includes a magnification calculation unit that calculates the magnification of the perspective image at each rotation angle. The CT apparatus according to any one of claims 1 to 3, wherein the magnification calculation unit calculates the magnification such that, when the shooting distance changes with the rotation angle, the magnification becomes the same as that of the fluoroscopic image taken at the shortest shooting distance.

Images