CT device

Abstract

The present invention provides a CT scanner that allows for easy and appropriate determination of the start and end positions during helical scanning. [Solution] The CT scanner is a helical scan type CT scanner that continuously images an object to be examined while moving and rotating it, and comprises an examination table 1 on which the object to be examined is placed and on which the object to be examined is moved and rotated, a radiation source 2 that irradiates the object to be examined with a radiation beam, a detector 3 provided opposite the radiation source 2 with the object to be examined in between, 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 the reconstruction end position Ze of the object to be examined, and calculates the data acquisition start position Zdas and the data acquisition end position Zdae based on the reconstruction start position Zs and the reconstruction end position Ze.

Description

Technical Field

[0001] Embodiments of the present invention relate to a CT apparatus.

Background Art

[0002] Industrial CT apparatuses for inspecting small electronic components such as lithium ion batteries with high resolution are widely used. In this CT apparatus, a radiation source that irradiates, for example, an X-ray beam as radiation and a detector that detects the X-ray beam of the radiation source with two-dimensional resolution are arranged to face each other. A rotatable inspection table is provided between the radiation source and the detector. The inspection table is configured to be rotatable and vertically movable. While the object to be inspected placed on the inspection table is irradiated with an X-ray beam, the inspection table rotates and moves vertically, so that the X-ray beam is irradiated in all directions from the lower end to the upper end of the object to be inspected. Thus, a helical scan method in which the object to be inspected is continuously photographed while being rotated and vertically moved is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Thus, in helical scan CT scanning, since the object to be inspected is photographed while being rotated as well as vertically moved, if the photographing is started in a state where the lower end of the object to be inspected is located at the lower end portion of the fluoroscopic image (see FIG. 5), the lower end of the object to be inspected immediately deviates from the irradiation range of the X-ray beam, and it is impossible to photograph all directions of the lower end portion of the object to be inspected and to form an image.

[0005] Therefore, with the helical scan method, it is necessary to position the examination table in an appropriate location below the state shown in Figure 5 before taking images. However, calculating the appropriate position is based on the user's intuition and experience, which can lead to errors, and it is difficult for users without specialized knowledge to position it intuitively. While users can also calculate the appropriate position manually, the calculation is complicated and time-consuming.

[0006] Embodiments of the present invention have been made to solve the above problems, and their objective is to provide a CT apparatus that can easily and appropriately determine the start and end positions of imaging in helical scanning. [Means for solving the problem]

[0007] The CT apparatus in the embodiment of the present invention is a helical scan type CT apparatus that continuously images an object to be examined while moving and rotating it, comprising: an examination table on which the object to be examined is placed and on which the object to be examined is moved and rotated; a radiation source that irradiates the object to be examined with a radiation beam; a detector provided opposite the radiation source with the object to be examined in between; 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 the reconstruction start position and reconstruction end position of the object to be examined, and calculates the data acquisition start position and data acquisition end position based on the reconstruction start position and reconstruction end position. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic side view showing the CT apparatus of the first embodiment. [Figure 2] This is a schematic plan view showing the CT apparatus of the first embodiment. [Figure 3] This is a block diagram showing the configuration of the control unit. [Figure 4] This is a schematic diagram showing the relative positions of the examination tables. [Figure 5] This figure shows an example of an image of an object being inspected. [Figure 6]It is a diagram showing an example of an image of the object to be inspected. [Figure 7] It is a schematic diagram showing that the same location of the object to be inspected is projected onto different positions of the detector in the helical scan method. [Figure 8] It is a diagram showing the locus of point P on the fluoroscopic image. [Figure 9] It is a diagram showing the rotation of the rotary table. [Figure 10] It is a diagram for explaining overscan. [Figure 11] It is a flowchart showing the procedure for calculating the position of the examination table in the CT apparatus of the first embodiment. [Figure 12] It is a diagram showing various parameters. [Figure 13] It is a flowchart showing the procedure for calculating the position of the examination table in the CT apparatus of the second embodiment. [Figure 14] It is a schematic diagram showing the state in which the user aligns with the upper end position of the object to be inspected using the image. [Figure 15] It is a schematic diagram showing the position of the examination table and various parameters in FIG. 11. [Figure 16] It is a schematic diagram showing the state in which the user aligns with the lower end position of the object to be inspected using the image. [Figure 17] It is a schematic diagram showing the position of the examination table and various parameters in FIG. 12.

Embodiments for Carrying Out the Invention

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

[0010] The CT apparatus 100 is an apparatus for non-destructive inspection of the object to be inspected A. The CT apparatus 100 irradiates a radiation beam B that penetrates the object to be inspected A around the object to be inspected A, and detects the radiation dose attenuated by passing through the object to be inspected A. The CT apparatus 100 in this embodiment is a helical scan type apparatus that irradiates the radiation beam B while rotating and lifting the object to be inspected A, and continuously performs imaging. Then, a CT image, which is a cross-sectional image of the object to be inspected A, is generated based on this detection result. Further, the CT apparatus 100 generates a 3D image from a plurality of generated CT images.

[0011] As shown in FIG. 1, the CT apparatus 100 includes an inspection 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 inspection table 1 is a table having a placement surface on which the object to be inspected A is placed. The inspection table 1 is movable in a direction parallel to or orthogonal to the placement surface. Further, the inspection table 1 is rotatable about an axis perpendicular to the placement surface. The inspection table 1 rotates and lifts the object to be inspected A during imaging. The inspection table 1 has a rotary table 11, a lifting mechanism 12, a Y mechanism 13, and an X mechanism 14.

[0012] The rotary table 11 places the object to be inspected A. The rotary table 11 is constituted by, for example, an actuator including a drive source such as a motor, and is provided so as to be rotatable about an axis perpendicular to the placement surface. While the radiation beam B is being irradiated, the rotary table 11 rotates, so that the radiation beam B is irradiated to all directions of the object to be inspected A. Note that a sample table may be provided on the rotary table 11, and the object to be inspected A may be placed on the sample table.

[0013] The lifting mechanism 12 is provided under the rotary table 11. The lifting mechanism 12 can use a ball screw mechanism driven by a servo motor. The lifting mechanism 12 is movable in a direction perpendicular to the placement surface. That is, by moving the lifting mechanism 12 in a direction perpendicular to the placement surface, the height of the object to be inspected A can be adjusted.

[0014] 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 C of the radiation beam B.

[0015] The X mechanism 14 is located below the Y mechanism 13. The X mechanism 14 can use, 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 C of the radiation beam B. The X mechanism 14 is configured to allow the inspection table 1, the radiation source 2, and the detector 3 to move independently.

[0016] 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 distance of the radiation source 2 from the object A under inspection is adjusted by the X mechanism 14.

[0017] 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 C of the radiation source 2. The detector 3 detects the two-dimensional distribution of radiation intensity, which is attenuated 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. The detector 3 is movable in a direction perpendicular to the imaging area (parallel to the optical axis of the radiation source 2) by a movement mechanism (not shown).

[0018] 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.

[0019] The filter section 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 section 4 of the material and thickness corresponding to the exposure time selected by the user along the optical axis of the radiation source 2. The radiation beam B is irradiated onto the filter section 4 positioned on the optical axis, and the radiation beam B that has passed through the filter section 4 is irradiated onto the object A under inspection. By allowing the radiation to pass through the filter section 4, the occurrence of metal artifacts is suppressed.

[0020] 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 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 under inspection A, such as fluoroscopic images, CT images, and 3D images, as well as the shooting area, shooting time, and shooting conditions.

[0022] The input unit 6 can use a keyboard, mouse, touch panel, etc. The input unit 6 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 inspected to be observed.

[0023] The control unit 7 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 7 is connected to the input unit 6, and the user controls the various components of the CT device 100 via the input unit 6 to the control unit 7.

[0024] Figure 3 is a block diagram showing the configuration of the control unit 7. As shown in Figure 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. Through the control of the inspection table control unit 71, the object under inspection A placed on the inspection table 1 can be aligned with the optical axis C of the radiation beam B, and the object under inspection A can be rotated or raised / lowered while the radiation beam B is irradiating it. Furthermore, 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 is adjusted.

[0026] The radiation source control unit 72 controls the radiation source 2 and irradiates the object A under inspection with the radiation beam B. That is, the inspection table control unit 71 and the radiation source control unit 72 control the radiation beam B to irradiate the object A under inspection in all directions.

[0027] The reconstruction unit 73 reconstructs the CT imaging area encompassed by the radiation beam B based on the number of transmission images obtained in the 360-degree direction. The reconstruction unit 73 reconstructs multiple cross-sectional images arranged continuously at equal intervals in a direction perpendicular to the mounting surface of the object under examination A, and forms three-dimensional data from these multiple cross-sectional images. The three-dimensional data can be displayed on the display unit 5 using MPR (Multi-planar Reconstruction) display or the like.

[0028] The inspection table position calculation unit 74 calculates the position and imaging range of the inspection table 1 during imaging. Information regarding the position of the inspection table 1 is pre-programmed in a storage unit (not shown). In this embodiment, the inspection table position calculation unit 74 calculates the reconstruction start position Zs and reconstruction end position Ze of the object under inspection A based on the current position Z0, which is the current position of the inspection table 1 (see Figure 4). In Figure 4, the area 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 is generated from the data acquired by the CT scan of the object under inspection A. The reconstruction start position Zs is on one end side of the object under inspection A, and the reconstruction end position Ze is on the other end side of the object under inspection A. The calculation method for each position will be described later.

[0029] Figure 5 shows an image when the object under inspection A is irradiated with radiation beam B so that the position of the inspection table is in contact with the lower end of the reconstruction start position Zs. In the non-helical scan method, the object under inspection A does not move up or down, so data can be acquired and the object under inspection A can be imaged as long as the image is taken with at least the reconstruction start position Zs and the reconstruction end position Ze within the range of radiation beam B. In other words, in the non-helical scan method, the inspection table 1 can start taking images from the state shown in Figure 5.

[0030] On the other hand, in the case of helical scanning as in this embodiment, if the inspection table 1 is positioned at the location where the image in Figure 5 is obtained and imaging is started, the object under inspection A will move downward as it moves up and down, and data from the lower end of the object under inspection A cannot be collected, making it impossible to create an image. Therefore, the imaging range in helical scanning needs to cover a wider area than the range of the reconstruction start position Zs and the reconstruction end position Ze.

[0031] Therefore, the inspection table position calculation unit 74 calculates the data acquisition start position Zdas and data acquisition end position Zdae based on the reconstruction start position Zs and reconstruction end position Ze of the object under inspection A. The data acquisition start position Zdas is the position where one end of the object under inspection A can be imaged in helical scanning, and the data acquisition end position Zdae is the position where the other end of the object under inspection A can be imaged. By the inspection table position calculation unit 74 calculating the data acquisition start position Zdas, imaging can be started with the lower end of the object under inspection A positioned at the upper end of the image, as shown in Figure 6.

[0032] Furthermore, the inspection table position calculation unit 74 considers the rotation and elevation required for overscanning when calculating the data acquisition start position Zdas and the data acquisition end position Zdae. In helical scanning, the object under inspection A is photographed while being raised and lowered, so as shown in Figure 7, point P of the object under inspection A at rotation angles of 0 (rad) and 2π (rad) is projected onto different positions on the detector 3. When projected onto different positions, artifacts are likely to occur due to the difference in density at those positions. Therefore, in order to mitigate artifacts, an overscan is performed to collect more data by a rotation angle α (radian) (α / 2 at each end) than the data acquisition range that is originally required. The inspection table position calculation unit 74 calculates the data acquisition start position Zdas and the data acquisition end position Zdae considering this overscan rotation angle α.

[0033] Overscan will be explained in detail with the help of Figures 8-10. In the case of non-helical scanning, the examination table 1 does not move up or down during rotation, so on the fluoroscopic image, the trajectory of point P is detected as an ellipse, as shown in Figure 8(a). Furthermore, since the position of point P at rotation angles of 0 (rad) and 2π (rad) is detected at the same point on the detector 3, artifacts are less likely to occur.

[0034] On the other hand, in the case of helical scanning, the inspection table 1 also moves up and down while rotating. Therefore, as shown in Figure 8(b), the trajectory of point P on the fluoroscopic image becomes a curve as the object A rotates and moves up and down, and the position of point P at rotation angles of 0 (rad) and 2π (rad) is 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 rotary table 11 is 0 (see Figures 7 and 9). When the height of the inspection table 1 is at Z, point P on the reconstructed cross-section of the object under inspection A is projected onto the position of point A on the detector 3. On the other hand, when the rotary table 11 makes one rotation (φ=2π), the inspection table 1 moves to a position higher by a helical pitch Zp from the height Z (Z+Zp). When the height of the inspection table 1 is at Z+Zp, point P on the reconstructed cross-section of the object under inspection A is projected onto the position of point B on the detector 3, which is a different position from point A.

[0036] Thus, in the case of helical scanning, the position of point P on the object A under inspection differs depending on the height of the inspection table 1, and artifacts are likely to occur due to the difference in density between point A and point B. Therefore, an overscan is performed to collect data for more than the data acquisition range that is originally required, by a rotation angle α (radians) (α / 2 minutes at each end) (see Figure 10). As described above, the rotary table 11 rotates by 2π+α, and the data from the rotation angle α is also used in the synthesis, so artifacts can be mitigated.

[0037] The inspection table position calculation unit 74 calculates the inspection table lifting start position Zss and the inspection table lifting end position Zse. A certain amount of time is required for the rotation and lifting of the inspection table 1 to become constant from a stopped state. Therefore, the inspection table position calculation unit 74 calculates the distance dza from the state in which the inspection table 1 is not rotating or lifting until it reaches a predetermined rotational speed and lifting speed. Then, the inspection table position calculation unit 74 calculates the position from the data acquisition start position Zdas, taking the distance dza into consideration, as the inspection table lifting start position Zss. That is, when the inspection table 1 reaches the data acquisition start position Zdas, its rotation and lifting speed becomes constant. The inspection table position calculation unit 74 also calculates the distance dzd from the predetermined rotational speed and lifting speed until the rotation and lifting of the inspection table 1 stops. Then, the inspection table position calculation unit 74 calculates the position from the data acquisition start position Zdas, taking the distance dzd into consideration, as the inspection table lifting start position Zss.

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

[0039] [Calculation of the position of the examination table] Next, the specific method for calculating the position of the examination table 1 and the scanning range at the start of scanning in the CT apparatus 100 of this embodiment will be explained with reference to the flowchart in Figure 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 Figure 4, the current position Z0 is defined as the position where the radiation beam B is irradiated onto the object A to be inspected so that the inspection table 1 is in contact with the lower end of the reconstruction start position Zs. As described above, when the inspection table 1 is positioned at the current position Z0, as the object A to be inspected rotates and moves up and down, the object A to be inspected moves downward, making it impossible to collect data from the lower end of the object A to be inspected and thus impossible to image it.

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

[0042]

number

[0043]

number

[0044] In the above number (1), ΔZ·(K-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 inspection table position calculation unit 74 calculates ZW0 using the following formula (3) (see Figure 12).

[0045]

number

[0046] After calculating the reconstruction start position Zs and reconstruction start position Ze of the object under inspection A, the inspection table position calculation unit 74 calculates the data acquisition start position Zdas (step S03). When calculating the data acquisition start position Zdas, the inspection table position calculation unit 74 takes into account the rotation and elevation for overscanning. Therefore, the inspection 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 acquisition start position Zdas, as shown in Figure 6, the lower end of the object under inspection A is positioned at the upper end of the image. Therefore, even if the object under inspection A descends, the radiation beam B can be irradiated in all directions onto the lower end of the object under inspection A, and it can be imaged.

[0050] The overscan angle α may be an angle pre-stored in the memory unit, or an angle entered by the user via the input unit 6. Overscan does not need to be considered. In this case, α becomes 0, and 1 should be substituted for Kzp in equation (4) above.

[0051] Next, the inspection table position calculation unit 74 calculates the inspection table lifting start position Zss, based on the data acquisition start position Zdas, at which the rotation and lifting of the inspection table 1 will be at a constant speed when it reaches the data acquisition start position Zdas (step S04). The inspection table position calculation unit 74 calculates the distance dza required for the rotation and lifting of the inspection table 1 to be at a constant speed based on the following formula (6).

[0052]

number

[0053] The inspection table position calculation unit 74 then calculates the inspection table lifting start position Zss based on the following formula (7).

[0054]

number

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

[0056]

number

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

[0058]

number

[0059]

number

[0060] As described above, once the inspection table position calculation unit 74 has finished calculating the inspection table lifting start position Zss and the inspection table lifting end position Zse, it determines whether or not the movement of the inspection table 1 is within the range of the Lower Limit and Upper Limit shown in Figure 4 (step S07).

[0061] If the inspection table position calculation unit 74 determines that the table is not within range (step S07 No), the imaging cannot be performed and the process ends. On the other hand, if the inspection table position calculation unit 74 determines that the table is within range (step S07 Yes), the inspection table 1 is moved to the inspection table lifting start position Zss (step S08). The movement of the inspection table 1 may be performed automatically, or the inspection table lifting start position Zss may be displayed on the display unit 5 and the user may move it manually. Once the movement of the inspection table 1 is complete, the user starts the imaging process (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 to be inspected A while raising, lowering and rotating it, and comprises an inspection table 1 on which the object to be inspected A is placed and which raises, lowers and rotates the object to be inspected A, 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 an inspection table position calculation unit 74 that calculates the position of the inspection table 1 during imaging. The inspection table position calculation unit 74 calculates the reconstruction start position Zs and reconstruction end position Ze of the object to be inspected A based on the current position Z0 of the inspection table 1, and calculates the data acquisition start position Zdas and data acquisition end position Zdae based on the reconstruction start position Zs and reconstruction end position Ze.

[0063] Thus, the inspection table position calculation unit 74 calculates the data acquisition start position Zdas at the lower end and the data acquisition end position Zdae at the upper end during helical scanning, eliminating the need for the user to manually calculate the position of the inspection table 1. Furthermore, the user does not need to intuitively adjust the position of the inspection table 1, making it easy and accurate to determine the start and end positions for imaging. Consequently, even inexperienced users can perform helical scanning with high accuracy.

[0064] The inspection table position calculation unit 74 calculates the data acquisition start position Zdas and data acquisition end position Zdae by considering the overscan angle α necessary to suppress artifacts. This allows for the synthesis of data corresponding to the extra overscan angle α. As a result, artifacts caused by the difference in density when the same location P of the object under inspection A is detected from different positions on the detector 3 can be suppressed.

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

[0066] [Second Embodiment] The CT apparatus 100 according to the second embodiment will be described with reference to the flowchart in Figure 13. Note that components with the same configuration and functions as those in the first embodiment are denoted by the same reference numerals, and detailed explanations are omitted. In the first embodiment, the reconstruction start position Zs and reconstruction end position Ze were calculated based on the current position Z0 of the examination table 1 and formulas (1) to (3). In the second embodiment, the user manually aligns the lower and upper end positions of the object A to be inspected using the input unit 6 in the image (step S11). The examination table position calculation unit 74 then calculates the reconstruction start position Zs and reconstruction start position Ze of the object A to be inspected based on the lower and upper end positions of the object A to be inspected (step S02). Note that the steps from step S03 onward are the same as in the first embodiment.

[0067] The user selects the upper edge of the object A being inspected from the imaged object A. For example, as shown by the solid line in Figure 14, a horizontal line that moves up and down is displayed on the display unit 5, and the input unit 6 aligns this horizontal line with the upper edge of the object A being inspected. At this time, if the vertical coordinate of the perspective image shown in Figure 14 is j and the horizontal coordinate is i, then the vertical center coordinate of the perspective image is j. c This is given by the following equation (11).

[0068]

number

[0069] Then, the vertical center coordinate j of the perspective image c The coordinate j of the upper end position of object A under inspection, which is located Δt above the above position. e This is given by equation (12) below. Δt is the number of pixels, and its distance can be calculated from the size of one pixel.

[0070]

number

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

[0072]

number

[0073] Similarly, the inspection table position calculation unit 74 calculates the reconstruction start position Zs. First, the user aligns the lower end of the object A under inspection with the fluoroscopic image shown in Figure 16. At this time, the vertical center coordinate j of the fluoroscopic image is... c The coordinate j of the lower end position of object A under inspection, which is located Δb lower than the coordinate j of the lower end position of object A under inspection. s This is given by the following equation (14).

[0074]

number

[0075] The inspection table position calculation unit 74 calculates the reconstruction start position Zs based on Δb (pixels) (see Figure 17). Specifically, the inspection table position calculation unit 74 calculates the reconstruction start position Zs based on the following formula (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 to be inspected using the input unit 6. The inspection table position calculation unit 74 then calculates the reconstruction start position Zs and reconstruction start position Ze of the object A to be inspected based on the lower and upper end positions of the object A to be inspected. As a result, the user only needs to align the lower and upper end positions of the object A to be inspected, and the inspection table position calculation unit 74 will calculate the reconstruction start position Zs and reconstruction start position Ze. Even with this configuration, the start and end positions of imaging can be easily and appropriately determined in helical scanning.

[0078] [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.

[0079] In the first embodiment, the current position Z0 was defined as the position where the radiation beam B was irradiated onto the object A under inspection so that the inspection table 1 was in contact with the lower end of the reconstruction start position Zs. However, the current position Z0 can be anywhere.

[0080] In the second embodiment, the upper and lower ends of the object A under inspection were aligned by matching the solid horizontal lines shown in Figures 14 and 16. However, any method is acceptable as long as the upper and lower ends of the object A under inspection can be selected. For example, it is sufficient to simply click on the upper and lower end positions of the object A under inspection with the cursor.

[0081] Alternatively, 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 reduces the effort required from the user 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 Detectors 31 Support frame 4. Filter section 5 Display section 6 Input section 7 Control Unit 71 Inspection Table Control Unit 72 Radiation Source Control Unit 73 Reconstruction part 74 Inspection table position calculation unit

Claims

1. A helical scan type CT scanner that continuously images the object under examination while moving and rotating it, 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, An inspection table position calculation unit that calculates the position of the inspection table during shooting, Equipped with, The inspection table position calculation unit calculates the reconstruction start position and reconstruction end position of the object to be inspected, and the CT device calculates the data acquisition start position and data acquisition end position based on the reconstruction start position and reconstruction end position.

2. The CT apparatus according to claim 1, wherein the examination table position calculation unit calculates the reconstruction start position and the reconstruction end position based on the current position of the examination table.

3. The system further includes an input unit that receives input from the user for the upper and lower end positions of the object to be inspected. The CT apparatus according to claim 1, wherein the inspection table position calculation unit calculates the reconstruction start position and the reconstruction end position based on the upper end position and lower end position of the object to be inspected input by the input unit.

4. The CT apparatus according to any one of claims 1 to 3, wherein the examination table position calculation unit calculates the data acquisition start position and the data acquisition end position taking into account the overscan angle necessary to suppress artifacts when calculating the data acquisition start position and the data acquisition end position.

5. The CT apparatus according to any one of claims 1 to 3, wherein the inspection table position calculation unit calculates the distance from which the rotation and raising / lowering of the inspection table moves from a stopped state to a constant speed, and calculates the inspection table raising / lowering start position at which the rotation and raising / lowering of the inspection table begins based on the said distance.

6. The CT apparatus according to claim 5, wherein the inspection table position calculation unit calculates the data acquisition start position and the data acquisition end position taking into account the overscan angle necessary to suppress artifacts when calculating the data acquisition start position and the data acquisition end position.

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