CT device

Abstract

To provide a CT device which comprises a collimator and facilitates operation performed by a user, by automatically adjusting width of the opening of the collimator.SOLUTION: A CT device comprises: an inspection table 1 on which an inspection-target is mounted and rotates the inspection-target; a radiation source 2 irradiating the inspection-target with radiation beam; a detector which faces the radiation source in a state of sandwiching the inspection-target between the detector and the radiation source ; a collimator 4 which is arranged between the radiation source and the inspection-target and restricts a radiation range of the radiation beam; a transparent image creation portion 73 creating a transparent image on the basis of a radiation dose detected by the detector; a sample extraction portion 74 extracting the inspection-target on the basis of the transparent image created by the transparent image creation portion; an optimal opening width calculation portion 76 calculating an optimal width of the opening of the collimator, on the basis of the size of the inspection-target extracted by the sample extraction portion and distance from the focus F of the radiation source to the center of the inspection table; and a collimator control portion 77 adjusting the position of the collimator, on the basis of the result of calculation performed by the optimal opening width calculation portion.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to a CT device. [Background technology]

[0002] Industrial CT devices are widely used for inspecting small electronic components such as lithium ion batteries with high resolution. As shown in Figs. 11 to 14, this CT device has a radiation source 20 that irradiates a radiation beam, for example an X-ray beam, and a detector 30 that detects the X-ray beam from the radiation source 20 with two-dimensional resolution, which are arranged facing each other. A rotatable inspection table 10 is provided between the radiation source 20 and the detector 30. While an X-ray beam is irradiated onto an object to be inspected A placed on the inspection table 10, the inspection table 10 rotates once, whereby the X-ray beam is irradiated in all directions of the object to be inspected A.

[0003] In this type of CT device, cone beam imaging is performed in which an X-ray beam is irradiated from a radiation source 20 in a cone-shaped manner. In cone beam imaging, a two-dimensional area sensor, for example, a flat panel detector (hereinafter referred to as "FPD") is used as a detector 30 that detects the X-ray beam.

[0004] When performing cone beam imaging, if the irradiation width of the X-ray beam is not limited, scattered rays unnecessary for imaging will be incident on the FPD, resulting in a deterioration in image quality. In order to suppress the influence of such scattered rays, it is known to use a collimator 40. The collimator 40 is made of a material such as tungsten or molybdenum, which has a high specific gravity and a high shielding ability. The collimator 40 has an opening 410. The collimator 40 is provided between the radiation source 20 and the object A to be inspected, and limits the irradiation width of the X-ray beam by the width of the opening 41.

[0005] However, if the width of the X-ray beam is limited by the collimator 40, the X-ray beam may become smaller than the dimension in the vertical direction (the direction perpendicular to the surface on which the object is placed) of the detector 30, making it impossible to obtain a desired image. Therefore, it is important to optimize the width of the opening 410 of the collimator 40. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-041838 A Summary of the Invention [Problem to be solved by the invention]

[0007] Conventionally, the width of the opening 410 of the collimator 40 has been adjusted manually by the user. However, in cone beam imaging, the object to be inspected is rotated once to be imaged, so even if the width of the opening of the collimator 40 is optimal for the rotation angle shown in Fig. 11, for example, a part of the object to be inspected A is outside the range of the X-ray beam (the dotted circle part in Fig. 12) for another angle shown in Fig. 12. Therefore, the user has to make adjustments while rotating the object to be inspected A, which is cumbersome.

[0008] The width of the opening of the collimator 40 also depends on the distance (FCD) from the focal point F of the radiation source 20 to the center position of the inspection table 10. Therefore, even if the entire object A to be inspected is within the range of the X-ray beam when FCD is L as shown in Fig. 13, part of the object A to be inspected is outside the range of the X-ray beam (two dotted circle portions in Fig. 14) when FCD is L' as shown in Fig. 14, and therefore it is necessary to readjust the width of the opening of the collimator 40.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a CT apparatus that automatically adjusts the optimal collimator opening width to simplify the user's work. [Means for solving the problem]

[0010] a collimator control unit that adjusts a position of the collimator based on a calculation result of the optimal aperture width calculation unit. The CT apparatus according to an embodiment of the present invention includes: an inspection table on which an object to be inspected is placed and which rotates the object to be inspected; a radiation source that irradiates a radiation beam onto the object to be inspected; a detector that is provided facing the radiation source with the object to be inspected in between; a collimator that is disposed between the radiation source and the object to be inspected and limits an irradiation range of the radiation beam; a fluoroscopic image creation unit that creates a fluoroscopic image based on an amount of radiation received by the detector; a sample extraction unit that extracts the object to be inspected from the fluoroscopic image created by the fluoroscopic image creation unit; [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a side view diagrammatically illustrating a CT apparatus according to a first embodiment. [Diagram 2] FIG. 1 is a plan view illustrating a CT apparatus according to a first embodiment. [Diagram 3] FIG. 2 is a block diagram showing the configuration of a control unit according to the first embodiment. [Figure 4] 5 is a flowchart for calculating the width of an opening of a collimator in the first embodiment. [Diagram 5] FIG. 4 is a diagram showing an example of calculation of a diameter D of an object to be inspected in the first embodiment. [Figure 6] 5 is a diagram showing an example of calculation of a height Y of an object to be inspected in the first embodiment. FIG. [Figure 7] 6 is a diagram showing an example of calculation of the width of an opening in the first embodiment. FIG. [Figure 8] 13A and 13B are diagrams illustrating an example of calculation of the width of an opening in a modified example. [Figure 9] FIG. 11 is a block diagram showing the configuration of a control unit according to a second embodiment. [Figure 10]13 is a diagram showing an example of calculation of the width of an opening in the second embodiment. FIG. [Figure 11] FIG. 13 is a diagram showing adjustment of the width of the opening of a collimator in the conventional method. [Figure 12] FIG. 13 is a diagram showing adjustment of the width of the opening of a collimator in the conventional method. [Figure 13] FIG. 13 is a diagram showing adjustment of the width of the opening of a collimator in the conventional method. [Figure 14] FIG. 13 is a diagram showing adjustment of the width of the opening of a collimator in the conventional method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (First embodiment) Hereinafter, the CT device according to the first embodiment will be described in detail with reference to the drawings. Fig. 1 is a side view showing the CT device according to the first embodiment. Fig. 2 is a plan view showing the CT device according to the first embodiment.

[0013] The CT device 100 is a device used for non-destructive inspection of an object to be inspected A. The CT device 100 irradiates the periphery of the object to be inspected A with a radiation beam B that passes through the object to be inspected A, and detects the amount of radiation attenuated by passing through the object to be inspected A. Then, based on the detection result, the CT device 100 generates a CT image, which is a cross-sectional image of the object to be inspected A. The CT device 100 also generates a 3D image from the multiple CT images generated.

[0014] As shown in Fig. 1, the CT apparatus 100 includes an examination table 1, a radiation source 2, a detector 3, a collimator 4, a display unit 5, an input unit 6, and a control unit 7. The examination table 1 is a table having a mounting surface on which an object A to be inspected is placed. The examination table 1 is movable in a direction parallel to the mounting surface or in a direction perpendicular to the mounting surface. The examination table 1 is also rotatable around an axis perpendicular to the mounting surface. The examination table 1 includes an XY mechanism 11, a rotating table 12, and a lifting mechanism 13.

[0015] The XY mechanism 11 places the object to be inspected A on it. The XY mechanism 11 may be, for example, a ball screw mechanism driven by a servo motor. The XY mechanism 11 is movable in a direction parallel to the optical axis of the radiation beam B and in a direction parallel to the placement surface and perpendicular to the optical axis of the radiation beam. The direction parallel to the optical axis of the radiation beam B is referred to as the X direction, and the direction parallel to the placement surface and perpendicular to the optical axis of the radiation beam is referred to as the Y direction.

[0016] The turntable 12 is provided below the XY mechanism 11. The turntable 12 is configured, for example, by an actuator including a drive source such as a motor, and is provided rotatable about an axis perpendicular to the mounting surface. While the radiation beam B is being irradiated, the turntable 12 rotates, whereby the radiation beam B is irradiated in all directions on the inspection object A. The direction perpendicular to the mounting surface is referred to as the Z direction.

[0017] The lifting mechanism 13 is provided below the rotary table 12. A ball screw mechanism driven by a servo motor can be used as the lifting mechanism 13. The lifting mechanism 13 is movable in a direction perpendicular to the mounting surface. That is, the height of the object A to be inspected can be adjusted by moving the lifting mechanism 13 in a direction perpendicular to the mounting surface.

[0018] The radiation source 2 irradiates, for example, a radiation beam B that penetrates the inspection object A. The radiation beam B is a bundle of radiation that spreads in a cone 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 reflection type or transmission type microfocus X-ray tube or 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, and any beam that penetrates the inspection object A, such as gamma rays, can be used.

[0019] The detector 3 is provided facing the radiation source 2 across the inspection table 1 and the object to be inspected A. The detector 3 is provided so that the center of the imaging area coincides with the optical axis of the radiation source 2. The detector 3 detects a two-dimensional distribution of radiation intensity attenuated according to the transmission path of the radiation beam B. The detector 3 is configured by, for example, a flat panel detector (FPD).

[0020] The collimator 4 is a device that limits the path and incident area of ​​the radiation beam B. The collimator 4 is made of a material with a high specific gravity and high shielding ability, such as tungsten or molybdenum. The collimator 4 is provided between the radiation source 2 and the object to be inspected A, symmetrically above and below the optical axis of the radiation beam B from the radiation source 2.

[0021] The collimator 4 comprises two thin plates arranged to form an opening 41, and these two thin plates are movable in a direction perpendicular to the placement surface of the object A to be inspected. The two thin plates are moved by a drive mechanism (not shown). The drive mechanism is composed of a drive power supply, a motor, rails, a belt, etc. The width of the opening 41 of the collimator 4 is adjusted by adjusting the position of the thin plates with the drive mechanism. The drive mechanism is connected to a collimator control unit 77 described later, and adjusts the width of the opening 41 of the collimator 4 according to commands from the collimator control unit 77.

[0022] The display unit 5 is, for example, a monitor such as a liquid crystal display or an organic EL display, etc. The display unit 5 displays various images such as a fluoroscopic image, a CT image, and a 3D image of the object A, an imaging area, imaging conditions, and the like.

[0023] A keyboard, a mouse, a touch panel, etc. can be used as the input unit 6. The input unit 6 accepts various operations such as menu selection for actual photography or test photography, setting of photography conditions, manual operation of the moving mechanism, start of photography, and selection of a part of the inspection object A to be observed.

[0024] The control unit 7 is configured with a computer and a driver circuit. The computer is configured with a storage such as an HDD or SSD, a RAM, a CPU, etc. The control unit 7 is connected to the input unit 6, and a user causes the control unit 7 to control each component of the CT device 100 via the input unit 6.

[0025] Fig. 3 is a block diagram showing the configuration of the control unit 7. As shown in Fig. 3, the control unit 7 has an examination table control unit 71, a radiation source control unit 72, a fluoroscopic image creation unit 73, a sample extraction unit 74, a size calculation unit 75, an optimal aperture width calculation unit 76, and a collimator control unit 77.

[0026] The inspection table control unit 71 controls the XY mechanism 11, the rotating table 12, and the lifting mechanism 13. By controlling the inspection table control unit 71, the object A placed on the inspection table 1 can be aligned with the optical axis of the radiation beam B, and the object A can be rotated once during irradiation with the radiation beam B. In addition, by moving the inspection table 1 under the control of the inspection table control unit 71, the distance (FCD) between the radiation source 2 and the center of the inspection table 1 can be adjusted.

[0027] The radiation source control unit 72 controls the radiation source 2 to irradiate the inspection object A with the radiation beam B. That is, under the control of the inspection table control unit 71 and the radiation source control unit 72, the inspection object A is irradiated with the radiation beam B in all directions.

[0028] The fluoroscopic image creating unit 73 creates a fluoroscopic image of the object A to be inspected based on the amount of radiation received by the detector 3. The fluoroscopic image creating unit 73 creates a fluoroscopic image of the object A to be inspected in a state where it is not placed on the examination table 1. The fluoroscopic image creating unit 73 also creates a fluoroscopic image of the object A to be inspected in a state where it is placed on the examination table 1.

[0029] The sample extraction unit 74 extracts the contour of the object A based on the two fluoroscopic images created by the fluoroscopic image creation unit 73. Specifically, the sample extraction unit 74 subtracts a fluoroscopic image in which the object A is not placed on the examination table 1 from a fluoroscopic image in which the object A is placed on the examination table 1, and extracts the contour of the object A on the fluoroscopic image.

[0030] The size calculation unit 75 calculates various sizes based on the fluoroscopic image created by the fluoroscopic image creation unit 73. The size calculation unit 75 calculates the size Mw in the Y direction and the size Mh in the Z direction of the entire fluoroscopic image, and the size d in the Y direction and the size h in the Z direction on the fluoroscopic image of the object A extracted by the sample extraction unit 74. The entire fluoroscopic image here refers to the entire captured area including air portions.

[0031] For example, the size calculation unit 75 adds the fluoroscopic images in the circumferential direction. The size calculation unit 75 projects the addition result in a direction parallel to the placement surface to calculate a size Mh of the entire fluoroscopic image in the Z direction and a size h of the object A in the Z direction on the fluoroscopic image. The size calculation unit 75 also projects the addition result in a direction perpendicular to the placement surface to calculate a size Mw of the entire fluoroscopic image in the Y direction and a size d of the object A in the Y direction on the fluoroscopic image.

[0032] In addition, the size calculation unit 75 assumes that the shape of the object to be inspected A is cylindrical, and calculates the actual diameter D and height (size in the Z direction) Y of the object to be inspected A from the entire perspective image and the Z-direction size and Y-direction size of the object to be inspected A on the perspective image.

[0033] The optimum aperture width calculation unit 76 calculates the optimum width w of the aperture 41 of the collimator 4 for the object A to be inspected. The optimum aperture width calculation unit 76 calculates the width w of the aperture 41 using the diameter D and height Y calculated by the size calculation unit 75.

[0034] After calculating the width w of the opening 41, the optimum opening width calculation unit 76 determines whether or not the distance (FCD) between the radiation source 2 and the center of the examination table 1 has been changed. If the distance (FCD) has been changed, the optimum opening width calculation unit 76 recalculates the width w of the opening 41 of the collimator 4 based on the changed FCD.

[0035] The collimator control unit 77 controls the collimator 4 to adjust the width w of the opening 41 of the collimator 4. The collimator control unit 77 issues a command to a moving mechanism of the collimator 4 so that the width of the opening 41 becomes the width w calculated by the optimum opening width calculation unit 76. The width of the opening 41 is automatically set to the optimum width by the command of the collimator control unit 77.

[0036] Next, a description will be given of the calculation of the optimum width w of the opening 41 of the collimator 4. Fig. 4 is a flowchart showing the calculation of the optimum width w of the opening 41 of the collimator 4.

[0037] First, a test shot is taken (step S01). The test shot is taken twice. In the first shot, the inspection table 1 is rotated once while the inspection object A is not placed on the inspection table 1, and the shot is taken. In the second shot, the inspection table 1 is rotated once while the inspection object A is placed on the inspection table 1. Note that the collimator 4 is not used during the test shot.

[0038] After two photographs are taken, the fluoroscopic image creation unit 73 creates respective fluoroscopic images (step S02). Then, the sample extraction unit 74 subtracts the fluoroscopic image without the object A placed from the fluoroscopic image with the object A placed, and extracts the contour of the object A (step S03). Since the difference image of the background portion (air portion) becomes 0, it is possible to extract the contour of the object A.

[0039] When the extraction of the object to be inspected A is completed, the size calculation unit 75 calculates the size Mw in the Y direction and the size Mh in the Z direction of the entire fluoroscopic image, and the size d in the Y direction and the size h in the Z direction of the object to be inspected A on the fluoroscopic image (step S04). The size Mw in the Y direction and the size Mh in the Z direction of the entire fluoroscopic image, and the size d in the Y direction and the size h in the Z direction of the object to be inspected A on the fluoroscopic image are calculated in pixel units. The size of one captured pixel may be stored in advance and calculated in mm units. The size Mw in the Y direction and the size Mh in the Z direction of the entire fluoroscopic image may be calculated before the extraction of the object to be inspected A.

[0040] The size calculation unit 75 regards the shape of the object A to be inspected as a cylinder, and calculates the diameter D and height Y of the object A, which is regarded as a cylinder, from the entire perspective image and the sizes in the Y direction and the Z direction of the object A on the perspective image (step S05).

[0041] 5 and the following formulas (1) and (2). The size Dw of the detector 3 in the Y direction and the size Dh of the detector 3 in the Z direction are stored in advance in a storage unit (not shown) included in the control unit 7. (Formula 1) TIFF2025057145000002.tif28162

[0042] When this is expanded, we obtain the following equation (2). (Formula 2) TIFF2025057145000003.tif21153FDD: Distance from the focal point F of radiation source 2 to the center of examination table 1 FCD: distance from the focal point F of the radiation source 2 to the detector 3 Dw: Size of detector 3 in the Y direction

[0043] Moreover, the height Y is calculated from FIG. 6 and the following formulas (3) and (4). (Formula 3) TIFF2025057145000004.tif39165Dh: Z-direction size of detector 3

[0044] When this is expanded, the following equation (4) is obtained. (Formula 4) TIFF2025057145000005.tif32150

[0045] When the diameter D and height Y of the object A to be inspected are calculated by the size calculation unit 75, the optimum opening width calculation unit 76 calculates the optimum width w of the opening 41 of the collimator 4 based on the calculated diameter D and height Y of the object A to be inspected (step S06). The opening width w is calculated from FIG. 7 and the following formula (5). (Formula 5) TIFF2025057145000006.tif48152 CM: distance from the focal point F of the radiation source 2 to the surface of the collimator 4 facing the radiation source 2 (see Figures 7 and 8)

[0046] The optimum opening width calculation unit 76 judges whether the FCD has been changed after calculating the width w of the opening 41 (step S07). If the FCD has been changed after calculating the width w of the opening 41 (step S07 Yes), the process returns to step S06 and the optimum width w of the opening 41 is calculated again. In this case, the FCD in the denominator of the above formula (5) can be calculated by changing it to the changed FCD'. This process is repeated every time the FCD is changed.

[0047] On the other hand, if the FCD has not been changed (No in step S07), the collimator control unit 77 adjusts the collimator 4 so that the width becomes the width w calculated by the optimal aperture width calculation unit 76 (step S08). The collimator control unit 77 issues a command to the movement mechanism of the collimator 4, and causes the movement mechanism to move the collimator 4 so that the width becomes the width w of the aperture 41.

[0048] (effect) As described above, the CT apparatus 100 of this embodiment includes the examination table 1 on which the object A is placed and which rotates the object A, the radiation source 2 which irradiates the object A with a radiation beam B, the detector 3 which is provided facing the radiation source 2 across the object A, the collimator 4 which is disposed between the radiation source 2 and the object A and which limits the irradiation range of the radiation beam B, and the controller 7. The controller 7 includes a fluoroscopic image creating unit 73 which creates a fluoroscopic image based on the amount of radiation received by the detector 3, a sample extracting unit 74 which extracts the object A from the fluoroscopic image created by the fluoroscopic image creating unit 73, an optimal aperture width calculating unit 76 which calculates an optimal width w of the opening 41 of the collimator 4 based on the size of the object A extracted by the sample extracting unit 74 and the distance (FCD) from the focal point F of the radiation source 2 to the center of the examination table 1, and a collimator controller 77 which adjusts the position of the collimator 4 based on the calculation result of the optimal aperture width calculating unit 76.

[0049] This automatically adjusts the optimal width w of the opening 41 of the collimator 4, eliminating the need for the user to manually perform a complex task of fine alignment, making it possible to capture high-quality CT images with simple operations.

[0050] Also, the angle at which the inspection table 1 is rotated during the test imaging may be increased. In this case, the time required for the test imaging can be shortened. However, the smaller the rotation angle during the test imaging, the more detailed the image of the inspection object A can be captured, and therefore the more accurate the optimum width w of the opening 41 can be calculated.

[0051] (Modification) A modified CT device 100 will be described. The same configurations and functions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In the first embodiment, the object A is regarded as a cylinder, various sizes are calculated, and the optimum width w of the opening 41 is obtained. In the modified embodiment, the object A is regarded as a sphere, and the optimum width w of the opening 41 is obtained.

[0052] 8, an optimal width w of the opening 41 of the collimator 4 is calculated by calculating an area X where the radiation that has passed through the object A regarded as a sphere strikes the detector 3. The sample extraction unit 74 extracts the contour of the object A based on the fluoroscopic image created by the fluoroscopic image creation unit 73.

[0053] The size calculation unit 75 regards the object A as a sphere, and calculates the size h of the object A in the Z direction on the fluoroscopic image and the size Mh of the entire fluoroscopic image in the Z direction. Then, based on the size Dh of the detector 3 in the Z direction, which is stored in advance in the storage unit, the size calculation unit 75 calculates the area X where the radiation that has passed through the object A, which is regarded as a sphere, strikes the detector 3, based on the following formulas (6) and (7). The area X refers to the length of the detector 3 in the height direction (Z direction). (Equation 6) TIFF2025057145000007.tif55164

[0054] Expanding this gives the following equation (7). (Formula 7) TIFF2025057145000008.tif28160

[0055] When the size calculation unit 75 finishes the calculation, the optimum aperture width calculation unit 76 calculates the optimum width w of the aperture 41 of the collimator 4. The width w of the aperture 41 is calculated by the following formulas (8) and (9). (Formula 8) TIFF2025057145000009.tif57165

[0056] (Equation 9) TIFF2025057145000010.tif23165

[0057] When the optimum aperture width calculation unit 76 finishes calculating the width w of the aperture 41, the optimum aperture width calculation unit 76 judges whether the examination table 1 has been moved and the FCD has been changed. If the FCD has not been changed, the collimator control unit 77 controls the collimator 4 so that the width w becomes the width calculated by the optimum aperture width calculation unit 76.

[0058] On the other hand, when the FCD is changed to an FCD', the optimum opening width calculation unit 76 calculates a width w' that is an optimum opening 41 in the changed FCD' by the following formula (10). (Equation 10) TIFF2025057145000011.tif36147

[0059] Each time the FCD is changed, the width w of the aperture 41 is calculated by the above formula (11). If the FCD is not changed, the collimator control unit 77 controls the collimator 4 so that the width w becomes the width calculated by the optimal aperture width calculation unit .

[0060] In this manner, the CT apparatus 100 in the modified example calculates various sizes by regarding the object A as a sphere. Then, based on the various calculated sizes, the optimum aperture width calculation unit 76 calculates the optimum width of the aperture 41. Even when the width w of the aperture 41 is calculated in this manner, the collimator 4 can be automatically adjusted to the optimum aperture width w, so that the workload of the user can be reduced.

[0061] Moreover, by regarding the object A to be inspected as a sphere as in the modified example, there is no need to calculate the size in the Y direction as in the above embodiment. Therefore, the amount of calculation can be reduced, and the optimal width w of the opening 41 of the collimator 4 can be calculated easily. Even if the FCD is changed after the optimal width w of the opening 41 of the collimator 4 is calculated, it can be calculated by a simple proportional formula using the above formula (10). Therefore, even if the FCD is changed, the optimal width w of the opening 41 of the collimator 4 can be calculated easily.

[0062] Incidentally, regarding whether the object to be inspected A is regarded as a cylinder as in the embodiment or as a sphere as in the modified example, the precision is improved by adopting the one closer to the actual shape of the object to be inspected A. That is, when the shape of the actual object to be inspected A is closer to a cylinder, the width w of the opening 41 can be calculated more precisely by adopting the first embodiment, whereas when the shape of the actual object to be inspected A is closer to a sphere, the width w of the opening 41 can be calculated more precisely by adopting the modified example.

[0063] Second Embodiment A CT device 100 according to the second embodiment will be described. The same configurations and functions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In the first embodiment, the object A is regarded as a cylinder, and in the modified example, it is regarded as a sphere, and the size is calculated to obtain the optimum width w of the opening 41. In the second embodiment, a 3D image is created, and the optimum width w of the opening 41 is calculated.

[0064] Fig. 9 is a block diagram showing the configuration of the control unit 7 in the second embodiment. As shown in Fig. 9, the control unit 7 further includes a 3D image creation unit 78. The 3D image creation unit 78 creates a 3D image, which is three-dimensional data, by reconstructing the perspective image created by the perspective image creation unit 73. This 3D image is a grayscale image, and a sample extraction unit 74 binarizes the 3D image to extract the contour of the object A to be inspected.

[0065] The optimum aperture width calculation unit 76 uses the 3D image to calculate the optimum width w of the aperture 41 of the collimator 4. Specifically, as shown in Fig. 10, first, a raster scan is performed on the 3D image of a rectangular parallelepiped at a certain angle (also referred to as a reference angle) to move point P.

[0066] The distance from point P to the center of the 3D image in the optical axis direction (X direction) is Δα, and the distance from point P to the optical axis C in the direction (Z direction) perpendicular to the optical axis C of the radiation beam is Δβ. The projection position of the detector 3 on the extension of the straight line connecting the focal point F and point P is Q, and the distance from point Q to the optical axis C in the direction (Z direction) perpendicular to the optical axis C is G. If point P is within the inspection object A region, the optimal aperture width calculation unit 76 calculates G based on the following formula (11). Note that Δα, Δβ, and G are positive and negative values. If point P is not within the inspection object A region but is located in air, G is not calculated, and point P is moved until it is located within the inspection object A region. (Equation 11) TIFF2025057145000012.tif12165

[0067] The optimum aperture width calculation unit 76 moves the position of point P in the state of the reference angle, and similarly obtains G. This is repeated to create points P for all of the objects A to be inspected, calculate G, and calculate and store the maximum value Gmax and minimum value Gmin of G at the reference angle.

[0068] After the calculation of G at the reference angle is completed, the 3D image is rotated by a small angle (for example, 0.3 degrees) and raster-scanned in the same manner. The optimal aperture width calculation unit 76 calculates G in the same manner as for the reference angle. If the value of G is greater than the stored maximum value Gmax, the optimal aperture width calculation unit 76 updates the value as the maximum value Gmax. If the value of G is less than the stored minimum value Gmin, the optimal aperture width calculation unit 76 updates the value as the minimum value Gmin.

[0069] This is repeated for 360 degrees until it returns to the reference angle. The optimum opening width calculation unit 76 calculates X by the following formula (12) based on the final maximum value Gmax and minimum value Gmin. (Formula 12) TIFF2025057145000013.tif12144

[0070] The X found here corresponds to the region X calculated by the above formula (6) or (7). Then, the optimum aperture width calculation unit 76 calculates the optimum width w of the aperture 41 of the collimator 4 based on the above formula (9).

[0071] As described above, in the CT apparatus 100 of the second embodiment, the control unit 7 further includes the 3D image creation unit 78, which creates a 3D image of the object A to be inspected, and the sample extraction unit 74 extracts the object A from the 3D image by binarization. Then, the optimal aperture width calculation unit 76 uses the 3D image to calculate various sizes and calculates the optimal width w of the aperture 41 of the collimator 4.

[0072] In this way, in the second embodiment, various sizes are calculated based on the reconstructed 3D image, so that X can be calculated with high accuracy, and as a result, the optimal width w of the opening 41 of the collimator 4 can be obtained with high accuracy.

[0073] Note that the 3D image is rotated by a small angle, and by reducing this angle, it is possible to calculate X more accurately. On the other hand, by increasing the small angle, the calculation accuracy of X decreases, but the calculation time can be shortened.

[0074] (Other embodiments) In this specification, an embodiment of the present invention has been described, but this embodiment is presented as an example and is not intended to limit the scope of the invention. The above-mentioned embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiment and its modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and gist of the invention. [Explanation of symbols]

[0075] 100 CT equipment 1 Examination table 11 XY mechanism 12 Rotating table 13 Lifting mechanism 2 Radiation source 3. Detector 4 Collimator 41 Aperture 5 Display section 6 Input section 7 Control section 71 Examination table control unit 72 Radiation Source Control Section 73 Fluoroscopic Image Creation Department 74 Sample Extraction Section 75 Size Calculation Section 76 Optimum opening width calculation section 77 Collimator control section 78 3D Image Creation Department 10 Inspection table 20 Radiation source 30 Detector 40 Collimator 410 Aperture F focus A. Inspection item

Claims

1. an inspection table on which an object to be inspected is placed and which rotates the object to be inspected; a radiation source that irradiates the object to be inspected with a radiation beam; a detector disposed opposite the radiation source across the object to be inspected; a collimator disposed between the radiation source and the object to be inspected, the collimator limiting an irradiation range of the radiation beam; a fluoroscopic image creating unit that creates a fluoroscopic image based on the amount of radiation received by the detector; a sample extracting unit that extracts a contour of the object on the fluoroscopic image from the fluoroscopic image created by the fluoroscopic image creating unit; an optimal aperture width calculation unit that calculates an optimal width of the aperture of the collimator based on the size of the object on the fluoroscopic image extracted by the sample extraction unit and the distance from a focus of the radiation source to a center of the examination table; a collimator control unit that adjusts a position of the collimator based on a calculation result of the optimal aperture width calculation unit; A CT apparatus comprising:

2. A 3D image creation unit that reconstructs the fluoroscopic image created by the fluoroscopic image creation unit and creates a three-dimensional 3D image, The sample extraction unit extracts a contour of the object to be inspected based on the 3D image created by the 3D image creation unit. The CT apparatus according to claim 1.

3. The collimator comprises: Two thin plates, A moving mechanism for moving the thin plate; having The collimator control unit adjusts the width of the opening between the two thin plates by controlling the moving mechanism.

3. A CT apparatus according to claim 1 or 2.

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