CT device

Abstract

A CT device capable of easily and appropriately determining the start and end positions of imaging in helical scanning imaging is provided. [Solution] The CT apparatus is a helical scan type CT apparatus that continuously images an object being inspected while moving and rotating it, and includes an examination table 1 on which the object being inspected is placed and which moves and rotates the object being inspected, a radiation source 2 that irradiates the object being inspected with a radiation beam, a detector 3 that is provided opposite the radiation source 2 with the object being sandwiched between them, and an examination table position calculation unit 74 that calculates the position of the examination table 1 during imaging. The examination table position calculation unit 74 calculates a reconstruction start position Zs and a reconstruction end position Ze of the object being inspected, and calculates a data acquisition start position Zdas and a data acquisition end position Zdae based on the reconstruction start position Zs and the reconstruction end position Ze.

Description

[Technical Field]

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

[0002] Industrial CT systems are widely used for high-resolution inspection of small electronic components such as lithium-ion batteries. These CT systems consist of a radiation source that emits radiation, such as an X-ray beam, and a detector that detects the X-ray beam from the radiation source with two-dimensional resolution, arranged opposite each other. A rotatable inspection table is provided between the radiation source and the detector. The inspection table is configured to be rotatable and movable up and down. While the X-ray beam is irradiating an object placed on the inspection table, the inspection table rotates and moves up and down, thereby irradiating the X-ray beam in all directions from the bottom to the top of the object. A helical scanning method is known in which the object is continuously imaged while being rotated and moved up and down. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-113715 Summary of the Invention [Problem to be solved by the invention]

[0004] In this way, in a helical scan CT scan, the object to be inspected is photographed not only by rotating it but also by raising and lowering it. Therefore, if imaging is started when the bottom edge of the object is positioned at the bottom of the fluoroscopic image (see Figure 5), the bottom edge of the object will immediately fall out of the irradiation range of the X-ray beam, and it will not be possible to photograph the bottom edge of the object in all directions, making it impossible to image it.

[0005] Therefore, with the helical scan method, it is necessary to place the examination table in an appropriate position lower than that shown in Figure 5 before performing imaging. However, the calculation of the appropriate position is done intuitively based on the user's experience, and there may be errors from the appropriate position, making it difficult for users without specialized knowledge to place it intuitively. In addition, although the user can calculate the appropriate position by hand, the calculation is complicated and time-consuming.

[0006] The embodiment of the present invention has been made to solve the above-mentioned problems, and its purpose is to provide a CT device that can easily and appropriately determine the start and end positions of imaging in helical scanning mode. [Means for solving the problem]

[0007] A CT apparatus according to an embodiment of the present invention is a helical scan type CT apparatus that continuously captures images of an object being inspected while moving and rotating the object, and includes an examination table on which the object is placed and which moves and rotates the object being inspected, a radiation source that irradiates the object being inspected with a radiation beam, a detector that is provided opposite the radiation source across the object being inspected, and an examination table position calculation unit that calculates the position of the examination table during imaging, wherein the examination table position calculation unit calculates a reconstruction start position and a reconstruction end position of the object being inspected based on a current position of the examination table, and calculates a data collection start position and a data collection end position based on the reconstruction start position and the reconstruction end position, calculating an examination table lifting start position and an examination table lifting end position based on the data collection start position and the data collection end position; The data collection start position is a position where one end of the object to be inspected can be imaged, and the data collection end position is a position where the other end of the object to be inspected can be imaged. When calculating the data acquisition start position and the data acquisition end position, the examination table position calculation unit calculates the data acquisition start position and the data acquisition end position taking into account an overscan angle required to suppress artifacts, and determines whether the examination table lifting / lowering start position and the examination table lifting / lowering end position are within a range of a lower limit and an upper limit of lifting / lowering of the examination table. do. Furthermore, a CT apparatus in an embodiment of the present invention is a helical scan type CT apparatus that continuously captures images of an object under test while moving and rotating the object, and includes: an examination table on which the object under test is placed and which moves and rotates the object under test; a radiation source that irradiates the object under test with a radiation beam; a detector that is provided opposite the radiation source with the object under test sandwiched between them; an examination table position calculation unit that calculates the position of the examination table during imaging; and an input unit that receives input of upper and lower end positions of the object under test from a user, wherein the examination table position calculation unit calculates a reconstruction start position and a reconstruction end position of the object under test based on the upper and lower end positions of the object under test input by the input unit, and calculates a data collection start position and a data collection end position based on the reconstruction start position and the reconstruction end position; calculating an examination table lifting start position and an examination table lifting end position based on the data collection start position and the data collection end position; The data collection start position is a position where one end of the object to be inspected can be imaged, and the data collection end position is a position where the other end of the object to be inspected can be imaged. When calculating the data collection start position and the data collection end position, the examination table position calculation unit calculates the data collection start position and the data collection end position taking into account an overscan angle required to suppress artifacts, and determines whether the examination table lifting / lowering start position and the examination table lifting / lowering end position are within a range of a lower limit and an upper limit of the lifting / lowering of the examination table. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view schematically showing a CT apparatus according to a first embodiment. [Figure 2] FIG. 1 is a plan view schematically showing a CT apparatus according to a first embodiment. [Figure 3] FIG. 2 is a block diagram showing the configuration of a control unit. [Figure 4] FIG. 2 is a schematic diagram showing the positional relationship of an examination table. [Figure 5] FIG. 2 is a diagram showing an example of an image of an object to be inspected. [Figure 6] FIG. 2 is a diagram showing an example of an image of an object to be inspected. [Figure 7] 1 is a schematic diagram showing that the same location on an object to be inspected is projected onto different positions on a detector in a helical scanning method. [Figure 8] FIG. 10 is a diagram showing the locus of a point P on a perspective image. [Figure 9] FIG. 10 is a diagram illustrating the rotation of a rotary table. [Figure 10]FIG. 10 is a diagram for explaining overscanning. [Figure 11] 5 is a flowchart showing a procedure for calculating the position of an examination table in the CT apparatus of the first embodiment. [Figure 12] FIG. 2 is a diagram showing various parameters. [Figure 13] 10 is a flowchart showing a procedure for calculating the position of an examination table in the CT apparatus according to the second embodiment. [Figure 14] FIG. 10 is a schematic diagram showing a state in which a user aligns the upper end position of an object to be inspected using an image. [Figure 15] FIG. 12 is a schematic diagram showing the position of the examination table and various parameters in FIG. 11. [Figure 16] FIG. 10 is a schematic diagram showing a state in which a user aligns the lower end position of an object to be inspected using an image. [Figure 17] FIG. 13 is a schematic diagram showing the position of the examination table and various parameters in FIG. 12. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] Hereinafter, a CT device according to a first embodiment will be described in detail with reference to the drawings. Fig. 1 is a side view schematically showing the CT device of the first embodiment. Fig. 2 is a plan view schematically showing the CT device of the first embodiment.

[0010] The CT device 100 is a device used for non-destructive testing of an object A to be inspected. The CT device 100 irradiates the periphery of the object A with a radiation beam B that passes through the object A to detect the amount of radiation attenuated by passing through the object A. The CT device 100 of this embodiment is a helical scan type device that irradiates the object A with the radiation beam B while rotating and elevating it, thereby continuously capturing images. Then, based on the detection results, it generates CT images, which are cross-sectional images of the object A to be inspected. The CT device 100 also generates a 3D image from the multiple CT images generated.

[0011] As shown in FIG. 1, the CT device 100 includes an examination table 1, a radiation source 2, a detector 3, a filter unit 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 or perpendicular to the mounting surface. The examination table 1 is also rotatable around an axis perpendicular to the mounting surface. The examination table 1 rotates and elevates the object A to be inspected during imaging. The examination table 1 includes a rotary table 11, an elevating mechanism 12, a Y mechanism 13, and an X mechanism 14.

[0012] The object to be inspected A is placed on the turntable 11. The turntable 11 is configured, for example, by an actuator including a drive source such as a motor, and is provided so as to be rotatable about an axis perpendicular to the surface on which the table is placed. While the radiation beam B is being irradiated, the turntable 11 rotates, thereby irradiating the radiation beam B in all directions on the object to be inspected A. Alternatively, a sample table may be provided on the turntable 11, and the object to be inspected A may be placed on the sample table.

[0013] The lifting mechanism 12 is provided below the rotary table 11. A ball screw mechanism driven by a servo motor can be used as the lifting mechanism 12. The lifting mechanism 12 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 12 in a direction perpendicular to the mounting surface.

[0014] Y mechanism 13 is provided below lifting mechanism 12. For example, a ball screw mechanism driven by a servo motor can be used as Y mechanism 13. Y mechanism 13 is movable in a direction parallel to the placement surface and perpendicular to the optical axis C of radiation beam B.

[0015] X mechanism 14 is provided below Y mechanism 13. X mechanism 14 can be, for example, a ball screw mechanism driven by a servo motor. X mechanism 14 is movable in a direction parallel to optical axis C of radiation beam B. X mechanism 14 is configured to be able to move examination table 1, radiation source 2, and detector 3 independently of each other.

[0016] The radiation source 2 irradiates, for example, a radiation beam B that penetrates the object A to be inspected. The radiation beam B is a bundle of radiation rays 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 reflective or transmissive 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 object A to be inspected, such as gamma rays, can be used. The radiation source 2 is supported by a support frame 21. The distance between the radiation source 2 and the object A to be inspected is adjusted by an X mechanism 14.

[0017] The detector 3 is provided facing the radiation source 2 with the examination table 1 and the object to be inspected A sandwiched between them. The detector 3 is provided so that the center of the imaging area coincides with the optical axis C 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, and outputs a fluoroscopic image. The detector 3 is configured by, for example, a flat panel detector (FPD). The detector 3 is supported by a support frame 31. The distance between the detector 3 and the object to be inspected A is adjusted by an X mechanism 14. The detector 3 can be moved in a direction perpendicular to the imaging area (a direction parallel to the optical axis of the radiation source 2) by a movement mechanism (not shown).

[0018] The filter unit 4 is disposed in a position close to the radiation source 2 and between the object to be inspected A and the radiation source 2. The filter unit 4 is a thin plate-like member having a thickness of about several mm. The filter unit 4 is a metal plate made of copper, aluminum, iron, or an alloy containing these. A plurality of filter units 4 are provided, and the filter units 4 differ in material and thickness.

[0019] The filter unit 4 is provided so as to be movable by a moving mechanism (not shown). The moving mechanism may be, for example, a ball screw mechanism driven by a servo motor. The moving mechanism moves the filter unit 4, which is made of a material and has a thickness corresponding to the imaging time selected by the user, onto the optical axis of the radiation source 2. The filter unit 4 arranged on the optical axis is irradiated with a radiation beam B, and the radiation beam B that has passed through the filter unit 4 is irradiated onto the object A to be inspected. By passing the radiation beam through the filter unit 4, the occurrence of metal artifacts is suppressed.

[0020] The CT apparatus 100 may also include a collimator (not shown). The collimator is a device that limits the path and incident area of ​​the radiation beam B. The collimator is made of a material with a high specific gravity and excellent shielding ability, such as tungsten or molybdenum. The collimators are provided between the radiation source 2 and the object A to be inspected, symmetrically above and below the optical axis C of the radiation beam B from the radiation source 2.

[0021] The display unit 5 is, for example, a monitor such as a liquid crystal display or an organic EL display. The display unit 5 displays various images of the object A, such as a fluoroscopic image, a CT image, and a 3D image, an imaging area, an imaging time, imaging conditions, and the like.

[0022] A keyboard, mouse, 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, correction of photography time and photography conditions, manual operation of the movement mechanism, start of photography, and selection of a location of the inspection object A to be observed.

[0023] The control unit 7 is configured with a computer and a driver circuit. The computer is configured with storage such as an HDD or SSD, RAM, a CPU, etc. The control unit 7 is connected to the input unit 6, and a user controls each component of the CT device 100 via the input unit 6.

[0024] 3 is a block diagram showing the configuration of the control unit 7. As shown in FIG. 3, the control unit 7 includes an examination table control unit 71, a radiation source control unit 72, a reconstruction unit 73, and an examination table position calculation unit 74.

[0025] The inspection table control unit 71 controls the rotary table 11, the lifting mechanism 12, the Y mechanism 13, and the X mechanism 14. By controlling the inspection table control unit 71, the object A to be inspected placed on the inspection table 1 can be aligned with the optical axis C of the radiation beam B, and the object A to be inspected can be rotated once or raised and lowered while being irradiated 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.

[0026] The radiation source control unit 72 controls the radiation source 2 to irradiate the object to be inspected 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 object to be inspected A is irradiated with the radiation beam B in all directions.

[0027] The reconstruction unit 73 reconstructs the CT imaging region encompassed by the radiation beam B based on the number of transmission images obtained in 360-degree directions for the number of views. The reconstruction unit 73 reconstructs a plurality of cross-sectional images that are arranged continuously at equal intervals in a direction perpendicular to the surface on which the object A is placed, and forms three-dimensional data from these cross-sectional images. The three-dimensional data can be displayed on the display unit 5 in MPR (Multi-planar Reconstruction) display or the like.

[0028] The examination table position calculation unit 74 calculates the position of the examination table 1 and the imaging range during imaging. Information regarding the position of the examination table 1 is pre-programmed in a storage unit (not shown). In this embodiment, the examination table position calculation unit 74 calculates the reconstruction start position Zs and the reconstruction end position Ze of the object A to be inspected based on the current position Z0, which is the current examination table 1 (see FIG. 4). In FIG. 4, the range requiring reconstruction is hatched. The range between the reconstruction start position Zs and the reconstruction end position Ze is the range in which a cross-sectional image of the object A is generated from data acquired by CT scanning, and the reconstruction start position Zs is on one end side of the object A to be inspected, and the reconstruction end position Ze is on the other end side of the object A to be inspected. The method for calculating each position will be described later.

[0029] 5 shows an image obtained when radiation beam B is irradiated onto object A so that the position of the examination table is in contact with the lower end of reconstruction start position Zs. In the non-helical scan method, object A does not move up or down, so data can be acquired and object A can be imaged by capturing an image in a state where at least reconstruction start position Zs and reconstruction end position Ze are within the range of radiation beam B. That is, in the non-helical scan method, the examination table 1 can start capturing an image from the state shown in FIG.

[0030] On the other hand, in the case of helical scanning as in this embodiment, if imaging is started with the inspection table 1 placed at a position where the image in Fig. 5 can be obtained, the object A moves downward as it moves up and down, and data on the lower end portion of the object A cannot be collected, and it cannot be imaged. Therefore, the imaging range in helical scanning needs to be wider than the range between the reconstruction start position Zs and the reconstruction end position Ze.

[0031] Therefore, the examination table position calculation unit 74 calculates a data collection start position Zdas and a data collection end position Zdae based on the reconstruction start position Zs and reconstruction end position Ze of the object A. The data collection start position Zdas is a position where one end of the object A can be imaged in a helical scan, and the data collection end position Zdae is a position where the other end of the object A can be imaged. By the examination table position calculation unit 74 calculating the data collection start position Zdas, imaging can be started with the bottom end of the object A positioned at the top end of the image, as shown in FIG. 6.

[0032] Furthermore, the examination table position calculation unit 74 takes into account the rotation and elevation for overscanning when calculating the data collection start position Zdas and the data collection end position Zdae. In helical scanning, the object A is imaged while being elevated, so as shown in FIG. 7, point P of the object A at rotation angles 0 (rad) and 2π (rad) is projected at different positions on the detector 3. When projected at different positions, artifacts are likely to occur due to density differences at those positions. Therefore, to mitigate artifacts, an overscan is performed to collect data over a rotation angle α (radian) (α / 2 at each end) more than the data collection range actually required. The examination table position calculation unit 74 calculates the data collection start position Zdas and the data collection end position Zdae taking into account the rotation angle α of this overscan.

[0033] Overscanning will be explained in detail with reference to Figures 8 to 10. In the case of non-helical scanning, the examination table 1 does not move up and down during rotation, so the locus of point P is detected as an ellipse on the fluoroscopic image, as shown in Figure 8(a). The positions of point P at rotation angles of 0 (rad) and 2π (rad) are detected at the same location on the detector 3, so artifacts are unlikely to occur.

[0034] On the other hand, in the case of helical scanning, the examination table 1 also moves up and down while rotating. Therefore, on the fluoroscopic image, as shown in Figure 8(b), the trajectory of point P becomes a curve as the object A rotates and moves up and down, and the positions of point P at rotation angles of 0 (rad) and 2π (rad) are detected at different points on the detector 3.

[0035] Specifically, for example, let Z be the height of the inspection table 1 when the rotation angle φ of the turntable 11 is 0 (see FIGS. 7 and 9). When the inspection table 1 is at height Z, point P on the reconstructed cross section of the object A is projected onto the position of point A on the detector 3. On the other hand, when the turntable 11 rotates once (φ=2π), the inspection table 1 moves from height Z to a position (Z+Zp) that is higher by the helical pitch Zp. When the inspection table 1 is at height Z+Zp, point P on the reconstructed cross section of the object A is projected onto the position of point B on the detector 3, which is a different position from point A.

[0036] In this way, in the case of helical scanning, the position where the detector 3 projects the position of point P on the object A varies depending on the height of the inspection table 1, and artifacts are likely to occur due to the difference in density between points A and B. Therefore, overscanning is performed to collect data that is greater than the originally required data collection range by a rotation angle α (radian) (α / 2 minutes at each end) (see FIG. 10). As described above, the turntable 11 rotates by 2π+α, and data for the rotation angle α is also used and synthesized, thereby mitigating artifacts.

[0037] The examination table position calculation unit 74 calculates the examination table lift start position Zss and the examination table lift end position Zse. It takes a certain amount of time for the rotation and lift of the examination table 1 to become constant from a stopped state. Therefore, the examination table position calculation unit 74 calculates the distance dza from the state where the examination table 1 is not rotating or lifting to the predetermined rotation speed and lifting speed. The examination table position calculation unit 74 then calculates the position from the data collection start position Zdas, taking into account the distance dza, as the examination table lift start position Zss. That is, when the examination table 1 reaches the data collection start position Zdas, the rotation and lifting speed of the examination table 1 become constant. The examination table position calculation unit 74 also calculates the distance dzd from the predetermined rotation speed and lifting speed until the rotation and lifting speed of the examination table 1 stops. The examination table position calculation unit 74 then calculates the position from the data collection start position Zdas, taking into account the distance dzd, as the examination table lift start position Zss.

[0038] Finally, the examination table position calculation unit 74 determines whether the calculated examination table lifting start position Zss and examination table lifting end position Zse are within the range of the lower limit and upper limit of the lifting of the examination table 1. The lower limit and upper limit of the lifting of the examination table 1 are stored in advance in a storage unit (not shown). If the examination table position calculation unit 74 determines that they are within the range, it moves the examination table 1 to the examination table lifting start position Zss and starts imaging. On the other hand, if it determines that they are outside the range, imaging does not start. In this case, an error message may be displayed on the display unit 5, indicating that the imaging range exceeds the lower limit or upper limit of the examination table 1.

[0039] [Calculating the position of the examination table] Next, a specific method for calculating the position of the examination table 1 and the imaging range at the start of imaging in the CT device 100 of this embodiment will be described with reference to the flowchart in Fig. 11. First, the examination table position calculation unit 74 calculates the current position Z0 of the examination table 1 (step S01).

[0040] In this embodiment, for example, as shown in Fig. 4, the position where the radiation beam B is irradiated onto the object A so that the inspection table 1 is in contact with the lower end of the reconstruction start position Zs is set as the current position Z0. As described above, when the inspection table 1 is placed at the current position Z0, the object A moves downward as the object A rotates and moves up and down, and data on the lower end portion of the object A cannot be collected, and the object A cannot be imaged.

[0041] Therefore, a data collection start position Zdas is calculated that is below the reconstruction start position Zs of the object A and that can image the lower end of the object A. In this embodiment, the examination table position calculation unit 74 calculates the data collection start position Zdas based on the current position Z0 of the examination table 1. Specifically, the examination table position calculation unit 74 calculates the reconstruction start position Zs and the reconstruction start position Ze of the object A based on the following equations (1) and (2) (step S02).

[0042]

number

[0043]

number

[0044] ΔZ·(K-1) in the above equation (1) is the range of data required for reconstruction, i.e., the length from the reconstruction start position Zs to the reconstruction start position Ze. The examination table position calculation unit 74 calculates ZW0 using the following equation (3) (see FIG. 12).

[0045]

number

[0046] After calculating the reconstruction start position Zs and reconstruction start position Ze of the object A, the examination table position calculation unit 74 calculates the data acquisition start position Zdas (step S03). When calculating the data acquisition start position Zdas, the examination table position calculation unit 74 takes into account rotation and elevation for overscanning. Therefore, the examination table position calculation unit 74 calculates the data acquisition start position Zdas based on the following equations (4) and (5).

[0047]

number

[0048]

number

[0049] When the inspection table 1 is positioned at the data collection start position Zdas, as shown in Figure 6, the bottom end of the object A to be inspected is positioned at the top end of the image, so even if the object A to be inspected descends, the radiation beam B can be irradiated in all directions to the bottom end part of the object A to be inspected, allowing it to be imaged.

[0050] The overscan angle α may be an angle stored in advance in the storage unit, or an angle input by the user via the input unit 6. Note that overscan does not need to be taken into consideration. In this case, α is set to 0, and 1 is substituted for Kzp in the above equation (4).

[0051] Next, based on the data collection start position Zdas, the examination table position calculation unit 74 calculates the examination table lifting start position Zss at which the rotation and lifting speed of the examination table 1 becomes constant when the examination table 1 reaches the data collection start position Zdas (step S04). The examination table position calculation unit 74 calculates the distance dza required for the rotation and lifting speed of the examination table 1 to become constant based on the following equation (6).

[0052]

number

[0053] Then, the examination table position calculation unit 74 calculates the examination table lift start position Zss based on the following formula (7).

[0054]

number

[0055] As described above, the examination table position calculation unit 74 calculates the examination table lift start position Zss and determines the position of the examination table 1 at the start of imaging. Next, the examination table position calculation unit 74 calculates the data acquisition end position Zdae based on the following equation (8) (step S05).

[0056]

number

[0057] The examination table position calculation unit 74 also takes overscan into consideration when calculating the data acquisition end position Zdae. After completing calculation of the data acquisition end position Zdae, the examination table position calculation unit 74 calculates the examination table lifting end position Zse based on the following equations (9) and (10) in consideration of the distance dzd until the rotation and lifting of the examination table 1 stops (step S06).

[0058]

number

[0059]

number

[0060] As described above, after the examination table position calculation unit 74 has finished calculating the examination table lift start position Zss and the examination table lift end position Zse, it determines whether or not they are within the range of the lower limit position (Lower Limit) and upper limit position (Upper Limit) of the movement of the examination table 1 shown in Figure 4 (step S07).

[0061] If the examination table position calculation unit 74 determines that the examination table is not within the range (step S07 No), imaging cannot be performed and the process ends. On the other hand, if the examination table position calculation unit 74 determines that the examination table is within the range (step S07 Yes), the examination table 1 is moved to the examination table lifting start position Zss (step S08). The examination table 1 may be moved automatically, or the examination table lifting start position Zss may be displayed on the display unit 5 and the user may move it manually. After the examination table 1 has been moved, the user begins imaging (step S09).

[0062] [effect] As described above, the CT apparatus 100 of this embodiment is a helical scan type CT apparatus 100 that continuously images the object A while raising, lowering, and rotating it, and includes the examination table 1 on which the object A is placed and which raises, lowers, and rotates the object A, the radiation source 2 that irradiates the object A with a radiation beam B, the detector 3 that is provided opposite the radiation source 2 across the object A, and an examination table position calculation unit 74 that calculates the position of the examination table 1 during imaging. The examination table position calculation unit 74 calculates the reconstruction start position Zs and reconstruction end position Ze of the object A based on the current position Z0 of the examination table 1, and calculates the data acquisition start position Zdas and data acquisition end position Zdae based on the reconstruction start position Zs and the reconstruction end position Ze.

[0063] In this way, the examination table position calculation unit 74 calculates the data acquisition start position Zdas at the lower end position where data acquisition is required in helical scanning, and the data acquisition end position Zdae at the upper end position, so the user does not need to calculate the position of the examination table 1 manually. Also, the user does not need to intuitively adjust the position of the examination table 1, so the imaging start position and end position can be easily and appropriately determined. Therefore, even an inexperienced user can perform helical scanning with high accuracy.

[0064] When calculating the data collection start position Zdas and the data collection end position Zdae, the examination table position calculation unit 74 calculates the data collection start position Zdas and the data collection end position Zdae taking into account the overscan angle α required to suppress artifacts. This makes it possible to combine data for the extra overscan angle α caused by rotation. Therefore, it is possible to suppress artifacts that occur when the same location P of the object A is detected from different positions on the detector 3 and are caused by density differences.

[0065] The examination table position calculation unit 74 calculates distances dzd, dza until the rotation and elevation of the examination table 1 reach a constant speed, and calculates, based on the distances dzd, dza, the examination table elevation start position Zss at which to start the rotation and elevation of the examination table 1. This allows imaging of the reconstruction range to begin when the rotation and elevation of the examination table 1 reach a constant speed, thereby improving imaging accuracy.

[0066] [Second embodiment] A CT apparatus 100 according to the second embodiment will be described with reference to the flowchart of FIG. 13. Note that the same configurations and functions as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In the first embodiment, the reconstruction start position Zs and the reconstruction end position Ze are calculated based on the current position Z0 of the examination table 1 and formulas (1) to (3). However, in the second embodiment, the user manually aligns the bottom and top end positions of the object A in the image using the input unit 6 (step S11). Then, the examination table position calculation unit 74 calculates the reconstruction start position Zs and the reconstruction start position Ze of the object A based on the bottom and top end positions of the object A (step S02). Note that the processes from step S03 onwards are the same as those in the first embodiment.

[0067] The user selects the upper end of the object A from the image of the object A. For example, a horizontal line moving up and down is displayed on the display unit 5, as shown by the solid line in FIG. 14, and the user aligns this horizontal line with the upper end of the object A using the input unit 6. At this time, if the vertical coordinate of the fluoroscopic image shown in FIG. 14 is j and the horizontal coordinate is i, then the vertical center coordinate of the fluoroscopic image j is c is expressed as the following equation (11).

[0068]

number

[0069] And the vertical center coordinate of the perspective image j c The coordinate j of the upper end position of the object A to be inspected is located Δt above the e is expressed by the following equation (12): Δt is the number of pixels, and the distance can be calculated from the size of one pixel.

[0070]

number

[0071] The examination table position calculation unit 74 calculates the reconstruction end position Ze based on Δt (pixels) (see FIG. 15). Specifically, the examination table position calculation unit 74 calculates the reconstruction end position Ze based on the following equation (13).

[0072]

number

[0073] Similarly, the examination table position calculation unit 74 calculates the reconstruction start position Zs. First, the user aligns the position with the lower end of the object A in the perspective image shown in FIG. 16. At this time, the vertical center coordinate j of the perspective image is c The coordinate j of the lower end position of the object A to be inspected is located Δb below s is expressed as the following equation (14).

[0074]

number

[0075] The examination table position calculation unit 74 calculates the reconstruction start position Zs based on Δb (pixels) (see FIG. 17). Specifically, the examination table position calculation unit 74 calculates the reconstruction start position Zs based on the following equation (15).

[0076]

number

[0077] As described above, in the second embodiment, the user manually selects the upper and lower end positions of the object A through the input unit 6. Then, the examination table position calculation unit 74 calculates the reconstruction start position Zs and the reconstruction start position Ze of the object A based on the lower and upper end positions of the object A. As a result, the user only needs to align the positions of the lower and upper ends of the object A, and the examination table position calculation unit 74 calculates the reconstruction start position Zs and the reconstruction start position Ze. Even with this configuration, the imaging start and end positions can be easily and appropriately determined in a helical scan.

[0078] [Other embodiments] Although the present specification describes an embodiment of the present invention, this embodiment is presented as an example and is not intended to limit the scope of the invention. The above-described embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0079] In the first embodiment, the current position Z0 is the position where the radiation beam B is irradiated onto the object A so that the inspection table 1 contacts the lower end of the reconstruction start position Zs, but the current position Z0 may be located anywhere.

[0080] In the second embodiment, the upper and lower ends of the object A to be inspected are aligned by aligning the solid horizontal lines shown in Fig. 14 and Fig. 16, but any method can be used as long as it is possible to select the upper and lower ends of the object A to be inspected. For example, it is also possible to simply click the upper and lower end positions of the object A to be inspected with the cursor.

[0081] Furthermore, the upper and lower ends of the object A to be inspected may be automatically set by image processing. That is, the object A to be inspected may be photographed in advance, and the control unit 7 may set the upper and lower ends of the object A to be inspected based on the photographed image. This saves the user time and effort and improves productivity. [Explanation of symbols]

[0082] 100 CT equipment 1 Examination table 11 Rotating table 12 Lifting mechanism 13 Y mechanism 14X mechanism 2 Radiation source 21 Support frame 3. Detector 31 Support frame 4. Filter section 5 Display section 6 Input section 7 Control Unit 71 Examination table control unit 72 Radiation Source Control Unit 73 Reconstruction part 74 Examination table position calculation unit

Claims

1. A helical scan CT device that continuously captures images of an object while moving and rotating it, an inspection table on which the object to be inspected is placed and which moves and 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; an examination table position calculation unit that calculates the position of the examination table during imaging; Equipped with the examination table position calculation unit calculates a reconstruction start position and a reconstruction end position of the object based on a current position of the examination table, calculates a data collection start position and a data collection end position based on the reconstruction start position and the reconstruction end position, and calculates an examination table lifting start position and an examination table lifting end position based on the data collection start position and the data collection end position; the data collection start position is a position where one end of the object to be inspected can be imaged, and the data collection end position is a position where the other end of the object to be inspected can be imaged; When calculating the data collection start position and the data collection end position, the examination table position calculation unit calculates the data collection start position and the data collection end position taking into account an overscan angle required to suppress artifacts, and determines whether the examination table lifting / lowering start position and the examination table lifting / lowering end position are within a range of an upper limit and a lower limit of the examination table lifting / lowering.

2. A helical scan CT device that continuously captures images of an object while moving and rotating it, an inspection table on which the object to be inspected is placed and which moves and 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; an examination table position calculation unit that calculates the position of the examination table during imaging; an input unit that receives input of the upper end position and the lower end position of the object to be inspected from a user; Equipped with the examination table position calculation unit calculates a reconstruction start position and a reconstruction end position of the object to be inspected based on the upper end position and the lower end position of the object to be inspected input by the input unit, calculates a data collection start position and a data collection end position based on the reconstruction start position and the reconstruction end position, and calculates an examination table lifting start position and an examination table lifting end position based on the data collection start position and the data collection end position, the data collection start position is a position where one end of the object to be inspected can be imaged, and the data collection end position is a position where the other end of the object to be inspected can be imaged; When calculating the data collection start position and the data collection end position, the examination table position calculation unit calculates the data collection start position and the data collection end position taking into account an overscan angle required to suppress artifacts, and determines whether the examination table lifting / lowering start position and the examination table lifting / lowering end position are within a range of an upper limit and a lower limit of the examination table lifting / lowering.

3. 3. The CT apparatus according to claim 1, wherein the examination table position calculation unit calculates a distance from a stopped state until the rotation and elevation of the examination table reach a certain speed, and calculates an examination table elevation start position at which the rotation and elevation of the examination table starts based on the calculated distance.

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