X-ray CT device and method for controlling x-ray CT device

Abstract

To provide an X-ray CT device that allows easy setting of magnification, while improving the image quality of a tomographic image of the entire analyte in helical scanning, and a method for controlling an X-ray CT device.SOLUTION: An X-ray CT device 1 has a photographing control unit 30 that rotates a stage 13 located in an X-axis direction centered on a rotation axis P1, moves the stage 13 and an X-ray source 11 and a detector 12 relatively in a Z-axis direction, and irradiates an analyte W placed on a stage surface 13a with an X-ray to acquire projection data DP20 with the use of the detector 12. The photographing control unit 30 controls a rotation driving mechanism 14 to relatively rotate the stage 13, and on the basis of magnification for expanding part of a target area of a detection area 12a while maintaining the ratio between a Y-axis direction and the Z-axis direction, controls a Z-axis direction moving mechanism 16 to relatively move the stage 13 in the Z-axis direction, thereby acquiring the projection data DP20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an X-ray CT apparatus that obtains a tomographic image of a subject by irradiating the subject with X-rays. [Background technology]

[0002] There is known an X-ray CT (Computed Tomography) device that irradiates a specimen such as a sample with X-rays from an X-ray source while rotating the specimen on a rotating table, and obtains a tomographic image of the sample based on X-ray projection data obtained from multiple directions.

[0003] One method for obtaining a high-resolution tomographic image is to increase the magnification of X-ray projection data. The magnification can be increased by moving the rotating table of the X-ray CT device, together with the subject, closer to the X-ray source. Also, for example, a higher-resolution tomographic image can be obtained by setting the magnification so that the entire or part of the subject is within the range of the detection area of ​​the detector that detects X-rays. However, in order to set the magnification so that the subject is within the range of the detection area of ​​the detector, it is necessary to move the rotating table many times while acquiring the X-ray projection data until a desired magnification is obtained, thereby correcting the position of the subject relative to the X-ray source.

[0004] Therefore, Patent Document 1 discloses an X-ray CT device for easily calculating the amount of movement that will give a desired imaging magnification. Specifically, the X-ray CT device of Patent Document 1 sets an ROI (region of interest) in a projection image of a reconstructed image reconstructed based on preliminarily acquired X-ray projection data, viewed in one direction, and calculates the amount of movement that will allow X-ray CT imaging of the ROI while keeping it within the detection region of the detector.

[0005] Furthermore, Patent Document 2 discloses an X-ray inspection device that performs a preliminary inspection to calculate the distance between an X-ray source and an object to be inspected so that a high-magnification image of the object to be inspected can be obtained in a back projection image. The X-ray inspection device of Patent Document 2 performs the preliminary inspection before a main inspection. In the preliminary inspection, in order to enlarge the projection image of the object to be inspected, a movement amount for moving the object to be inspected closer to the X-ray source is calculated based on an object region determined by the outer edge of the object in X-ray projection data acquired at multiple rotation angles. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-134528 A [Patent Document 2] International Publication No. 2016 / 170685 Summary of the Invention [Problem to be solved by the invention]

[0007] By the way, a technique called helical scan is known in which a rotating table is moved in the direction of the rotation axis to obtain X-ray projection data of a subject. With the helical scan, for example, it is possible to image the entire subject that is long in the direction of the rotation axis of the rotating table. In the helical scan, it is desired to improve the quality of the tomographic image of the entire subject while facilitating the setting of the magnification.

[0008] Patent Documents 1 and 2 do not specifically disclose a method for setting the imaging magnification in the helical scan so that the subject fits within the detection region. Therefore, in order to obtain a desired imaging magnification, it is necessary to determine the position of the subject relative to the X-ray source by trial and error. For this reason, depending on the knowledge and experience of the operator, it is difficult and time-consuming to set an appropriate magnification.

[0009] An object of the present invention is to provide an X-ray CT apparatus and a control method for an X-ray CT apparatus that can easily set a magnification ratio while improving the image quality of a tomographic image of the entire subject in a helical scan. [Means for solving the problem]

[0010] The X-ray CT device according to the first aspect includes an X-ray source that irradiates X-rays in an X-axis direction, a detector having a detection region for the X-rays irradiated by the X-ray source, a stage located between the X-ray source and the detector and having a stage surface capable of supporting a subject, a rotation drive mechanism that rotates the stage relatively to the X-ray source and the detector about a rotation axis that is perpendicular to the X-ray irradiation direction and the stage surface of the stage, an X-axis direction movement mechanism that moves the stage relatively to the X-ray source and the detector in the X-axis direction, and The X-ray CT apparatus includes a Z-axis direction moving mechanism that moves the stage, the X-ray source, and the detector relatively in the Z-axis direction, which is the direction in which the rotation axis extends, and an imaging control unit that rotates the stage positioned in the X-axis direction relatively around the rotation axis, moves the stage, the X-ray source, and the detector relatively in the Z-axis direction, and acquires projection data by the detector by irradiating the X-rays to the subject supported on the stage surface, and reconstructs a tomographic image of the subject based on the projection data. The imaging control unit of the X-ray CT apparatus controls the rotation drive mechanism to rotate the stage relatively, and controls the Z-axis direction moving mechanism to move the stage relatively in the Z-axis direction based on an enlargement magnification that enlarges a target region that is a part of the detection region in the Y-axis direction while maintaining a ratio between a Y-axis direction orthogonal to the X-axis direction and the Z-axis direction, respectively, to acquire the projection data.

[0011] In the above-described configuration, a part of the projected image can be enlarged by moving in the X-axis direction. Here, when a target area of ​​a part of the detection area is enlarged, the enlarged target area may be located outside the range of the detection area in the Z-axis direction. In the above-described configuration, in order to capture an image of the protruding part of the target area located outside the range of the detection area, the subject is captured while moving relatively in the Z-axis direction.

[0012] This allows the projected image to be enlarged in the width direction (Y-axis direction) and allows the entire subject to be imaged in the Z-axis direction.

[0013] Therefore, the image quality of the tomographic image of the entire subject can be improved, and the magnification can be easily set.

[0014] In the X-ray CT device of aspect 2, in aspect 1, the imaging control unit controls the X-axis direction moving mechanism to move the stage relatively in the X-axis direction based on the magnification ratio, thereby enlarging a target area of ​​a part of the detection area, and then controls the rotation drive mechanism to rotate the stage relative to the X-ray source and the detector, and controls the Z-axis direction moving mechanism to move the stage and the X-ray source relatively in the Z-axis direction to acquire projection data.

[0015] In the above-mentioned configuration, the stage is moved in the X-axis direction based on the magnification ratio to enlarge a target area that is a part of the detection area. After the movement in the X-axis direction, the stage is rotated and moved in the Z-axis direction to acquire projection data. This allows the target area that is a part of the detection area to be efficiently enlarged.

[0016] In the X-ray CT apparatus according to aspect 3, in addition to aspect 1, the imaging control unit determines, as the enlargement magnification, a magnification at which a target region that is a part of the detection region falls within a range of the detection region in the Y-axis direction.

[0017] According to the above-mentioned configuration, it is possible to prevent the magnification of the target area from being set beyond the range of the detection area of ​​the detector in the Y-axis direction. This makes it possible to prevent projection data from being acquired in which the subject protrudes from the detection area. Therefore, it is possible to suppress errors during imaging.

[0018] In the X-ray CT apparatus according to aspect 4, in addition to aspect 1, the imaging control unit determines the magnification ratio based on a position of the object where the width in the Y-axis direction is the widest.

[0019] In the above-mentioned configuration, even if the width in the Y-axis direction changes in the Z-axis direction, the object can be made to fit within the detection area. This makes it possible to prevent projection data from being acquired that causes the object to protrude from the detection area, thereby suppressing errors during imaging.

[0020] In the X-ray CT device of aspect 5, in aspect 1, the shooting control unit controls the stage to move relatively in one direction in the Z-axis direction until the other end of the enlarged target area coincides with the other end of the detection area, and then controls the stage to move relatively in the other direction in the Z-axis direction to acquire a projection image.

[0021] With the above-mentioned configuration, the stage can be moved efficiently for imaging, thereby shortening the imaging time.

[0022] In the X-ray CT device of aspect 6, in any one of aspects 1 to 5, the imaging control unit includes a magnification determination unit that sets the magnification ratio, a Z-axis direction movement amount determination unit that determines the amount of movement in the Z-axis direction to image a portion of the target area that is outside the detection area in the Z-axis direction when enlarging by the magnification ratio, an X-axis direction movement control unit that controls the X-axis direction movement mechanism to move the stage and the X-ray source relatively in the X-axis direction in accordance with the magnification ratio, and a Z-axis direction movement control unit that controls the Z-axis direction movement mechanism to move the stage, the X-ray source, and the detector relatively in the Z-axis direction in accordance with the amount of movement in the Z-axis direction.

[0023] According to the above-mentioned configuration, it is possible to easily realize an imaging control unit that can determine the amount of movement in the Z-axis direction and the amount of movement in the X-axis direction according to the set enlargement magnification.

[0024] A control method for an X-ray CT device according to aspect 7 is a control method for an X-ray CT device having an X-ray source that irradiates X-rays in the X-axis direction, a detector having a detection area for X-rays irradiated by the X-ray source, and a stage located between the X-ray source and the detector and having a stage surface capable of supporting a subject, and which reconstructs a tomographic image of the subject based on projection data acquired by the detector by irradiating the X-rays to the subject supported on the stage surface while rotating the stage relative to the X-ray source and the detector around rotation axes that are respectively perpendicular to the irradiation direction of the X-rays and the stage surface of the stage. The control method of the X-ray CT device includes an enlargement step of enlarging a target area of ​​a part of the detection area in the Y-axis direction while maintaining a ratio between the Y-axis direction and the Z-axis direction, which are respectively perpendicular to the X-axis direction and the Z-axis direction in which the rotation axis extends, and a projection data acquisition step of rotating the stage and moving the stage and the X-ray source relatively in the Z-axis direction based on the enlargement magnification in the enlargement step, and acquiring projection data by the detector by irradiating the X-rays to the subject placed or attached on the stage.

[0025] In the above-described configuration, a part of the projected image can be enlarged by moving in the X-axis direction. Here, when a target area of ​​a part of the detection area is enlarged, a part of the target area after enlargement may be located outside the range of the detection area in the Z-axis direction. In the above-described configuration, in order to capture an image of the protruding part of the target area located outside the range of the detection area, the subject is captured while being moved relatively in the Z-axis direction.

[0026] This allows the projected image to be enlarged in the width direction (Y-axis direction) and allows the entire subject to be imaged in the Z-axis direction.

[0027] Therefore, the image quality of the tomographic image of the entire subject can be improved, and the magnification can be easily set.

[0028] A control method for an X-ray CT apparatus according to an eighth aspect of the present invention is characterized in that in the enlarging step, the stage is moved in the X-axis direction based on the enlargement magnification.

[0029] In the above-described configuration, the stage is moved in the X-axis direction based on the magnification ratio to enlarge the target area of ​​the detection area, thereby enabling efficient enlargement of the target area of ​​the detection area.

[0030] A control method for an X-ray CT device in accordance with aspect 9, in accordance with aspect 7 or 8, further includes a positioning step of positioning the subject in the X-axis direction so that the entire subject is contained within the detection area when viewed in at least one direction perpendicular to the rotation axis, and in the enlargement step, the target area is enlarged while the subject is positioned in the X-axis direction.

[0031] According to the above-mentioned configuration, even if the width in the Y-axis direction changes in the Z-axis direction when viewed from one direction, the object can be contained within the detection area. This makes it possible to prevent projection data from being acquired that causes the object to protrude from the detection area before the target area is expanded. This makes it possible to prevent errors during imaging or deterioration of the image quality of the tomographic image. Effect of the Invention

[0032] In an X-ray CT device according to one embodiment of the present invention, an imaging control unit controls the rotation drive mechanism to rotate the stage, and also controls the Z-axis direction moving mechanism to move the stage and the X-ray source relatively in the Z-axis direction based on an enlargement magnification ratio that enlarges a target area of ​​a part of the detection area in the Y-axis direction while maintaining a ratio between a Y-axis direction and the Z-axis direction, which are perpendicular to the X-axis direction and the Z-axis direction, respectively, to acquire the projection data.

[0033] According to the above-described aspect, the magnification can be easily set while improving the image quality of the tomographic image of the entire subject. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a functional block diagram showing a schematic configuration of an X-ray CT apparatus according to an embodiment. [Diagram 2] FIG. 2 is a plan view illustrating the magnification of the projected image. [Diagram 3] FIG. 3 is a side view illustrating the magnification of the projected image, and is a view seen from the direction of the white arrow III in FIG. [Figure 4] FIG. 4 is a diagram showing the relationship between the detection region and the target region before the target region is enlarged. [Diagram 5] FIG. 5 is a diagram showing the relationship between the detection region and the target region after the target region is enlarged. [Figure 6] FIG. 6 is a diagram showing a state in which one end of the detection area and one end of the enlarged target area are moved relatively in the Z-axis direction so as to coincide with each other. [Figure 7] FIG. 7 is a diagram showing a state in which the detection area and the enlarged target area are moved relatively in the Z-axis direction so that the other end of the detection area and the other end of the enlarged target area coincide with each other. [Figure 8] FIG. 8 is a flowchart showing the flow of operations of the X-ray CT apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. Furthermore, the dimensions of the components in each drawing do not faithfully represent the actual dimensions of the components and the dimensional ratios of each component.

[0036] (Overall composition) FIG. 1 is a functional block diagram showing a schematic configuration of an X-ray CT apparatus 1 according to an embodiment.

[0037] In FIG. 1, the arrow X indicates the X-axis in the coordinate system of the X-ray CT device 1, the arrow Y indicates the Y-axis in the coordinate system of the X-ray CT device 1, and the arrow Z indicates the Z-axis in the coordinate system of the X-ray CT device 1. The direction of the arrow in each of the X-ray CT device 1, Y-axis, and Z-axis is the positive direction, and the direction opposite to the arrow is the negative direction. The X-axis and Y-axis are axes extending in the horizontal direction of the X-ray CT device 1. The Z-axis is an axis extending in the up-down direction of the X-ray CT device 1. Hereinafter, the up-down direction of the X-ray CT device 1 is simply referred to as the up-down direction. In the Z-axis direction, the direction of the arrow of the Z-axis is referred to as one side, and the direction opposite to the arrow is referred to as the other side. The Z-axis is perpendicular to the horizontal plane including the X-axis and the Y-axis. From another perspective, the Y-axis direction is perpendicular to the X-axis direction and the Z-axis direction.

[0038] As shown in FIG. 1, the X-ray CT device 1 has an X-ray source 11, a detector 12, a stage 13, a rotation drive mechanism 14, an X-axis direction moving mechanism 15, a Z-axis direction moving mechanism 16, a memory unit 20, an imaging control unit 30, a reconstruction unit 40, an operation unit 51, and a display unit 52.

[0039] The X-ray source 11 generates X-rays in a cone beam shape. The X-ray source 11 includes a microfocus X-ray tube with a focal point of several micrometers to several tens of micrometers. In a microfocus X-ray tube, electrons generated from a filament are focused and the focused electrons are directed to an anode, which is a target, to generate X-rays. The X-ray source 11 has an X-ray optical axis AX that extends in the X-axis direction, which is one horizontal direction. The X-ray source 11 irradiates X-rays in the X-axis direction to a detector 12 located in one direction of the X-ray optical axis AX.

[0040] The detector 12 has a detection region 12a for detecting X-rays irradiated by the X-ray source 11. The detector 12 is a two-dimensional X-ray detector having pixels arranged two-dimensionally. The detector 12 generates projection data DP20 based on the detected X-rays.

[0041] The stage 13 is a platform that supports the subject W. The stage 13 is located between the X-ray source 11 and the detector 12. The stage 13 has a stage surface 13a that is parallel to the XY plane. The subject W can be placed on the stage surface 13a of the stage 13. The stage 13 rotates about a rotation axis P1 that extends in the vertical direction by the driving force of a rotation driving mechanism 14, which will be described later.

[0042] The rotation drive mechanism 14 rotates the stage 13 relative to the X-ray source 11 and the detector 12 around a rotation axis P1 extending in the vertical direction. The rotation axis P1 is perpendicular to the X-ray optical axis AX, which is the irradiation direction of the X-rays, and the stage surface 13a of the stage 13. The rotation axis P1 extends in the Z-axis direction. As a result, the rotation drive mechanism 14 rotates the subject W placed on the stage 13 relative to the X-ray source 11 around the rotation axis P1. Specifically, the rotation drive mechanism 14 rotates the stage 13 at a constant speed in the direction of the arrow R11 shown in FIG. 1 around the rotation axis P1 extending in the vertical direction. When imaging the subject W, the rotation drive mechanism 14 rotates the stage 13 on which the subject W is placed by a predetermined angle or number of times under the control of the imaging control unit 30. The rotation drive mechanism 14 is realized by a driving device such as a motor.

[0043] The X-axis direction moving mechanism 15 moves the stage 13 in the X-axis direction relative to the X-ray source 11 and the detector 12. When imaging the subject W, the X-axis direction moving mechanism 15 moves the stage 13, on which the subject W is placed, to a predetermined position in the X-axis direction under the control of the imaging control unit 30.

[0044] The Z-axis direction moving mechanism 16 moves the stage 13 in the Z-axis direction relative to the X-ray source 11 and the detector 12. When imaging the subject W, the Z-axis direction moving mechanism 16 moves the stage 13, on which the subject W is placed, to a predetermined position in the Z-axis direction under the control of the imaging control unit 30.

[0045] The X-axis direction movement mechanism 15 and the Z-axis direction movement mechanism 16 are realized by a drive mechanism that converts the rotational drive force of an electric motor such as a motor into linear motion, and a motion controller board for operating the mechanism.

[0046] The storage unit 20 stores various data such as programs executed in the imaging control unit 30 and data used in the programs. The storage unit 20 can be realized, for example, by a volatile or non-volatile storage device. The storage unit 20 can be realized, for example, by a built-in or external storage device or removable media. To be specific, the storage unit 20 can be realized by a cache memory and a main storage device. To be specific, the storage unit 20 can be realized by an auxiliary storage device such as an SSD (Solid State Drive) or an HDD (Hard Disk). The storage unit 20 also stores projection data DP20 obtained by imaging the subject W at each angle.

[0047] The imaging control unit 30 controls imaging of the subject W using X-rays. The imaging control unit 30 of the X-ray CT device 1 realizes various functions by reading out a program stored in the storage unit 20 and executing the read out program using an arithmetic device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The imaging control unit 30 rotates the stage 13 positioned in the X-axis direction about a rotation axis P1, and moves the stage 13, the X-ray source 11, and the detector 12 relatively in the Z-axis direction, and irradiates the subject W placed on the stage surface 13a with the X-rays to obtain projection data using the detector 12. The detailed configuration of the imaging control unit 30 will be described later.

[0048] The reconstruction unit 40 reconstructs a tomographic image of the subject W based on the projection data DP20.

[0049] The operation unit 51 is a user interface for performing various operations in the X-ray CT apparatus 1. The operation unit 51 can be realized by, for example, an input device such as a keyboard or a button, or a pointing device such as a mouse, a pen tablet, or a touch panel. For example, an operator operates the operation unit 51 to perform imaging operations in the X-ray CT apparatus 1.

[0050] The display unit 52 presents to the user various data in the X-ray CT apparatus 1. The display unit 52 can be realized by a display device such as a liquid crystal or organic EL display device.

[0051] (Regarding magnification) The magnification of the projected image will be described with reference to Fig. 2 and Fig. 3 in addition to Fig. 1. Fig. 2 is a plan view for explaining the magnification of the projected image. Fig. 3 is a side view for explaining the magnification of the projected image, and is a view seen from the arrow III in Fig. 2.

[0052] In the X-ray CT apparatus 1, the closer the subject W is to the X-ray source 11, the greater the geometric magnification becomes, and therefore a tomographic image with higher resolution can be obtained.

[0053] In the following description, the point PX at which the X-ray source 11 is located means the position of the focal point of the X-ray source 11. For convenience of description, the size of the focal point of the X-ray source 11 is not taken into consideration.

[0054] 2 and 3, the X-ray optical axis AX of the X-ray source 11 extends in the X-axis direction from a point PX where the X-ray source 11 is located toward a detection region 12a of the detector 12. The X-ray optical axis AX is perpendicular to the detection region 12a. The point PX where the X-ray source 11 is located and the detection region 12a are located apart by a distance L1. In other words, the distance L1 is FDD (Focus Detector Distance).

[0055] A comparison is made between a magnification M1 when the subject W is at a position PS1 that is a distance D1 away from the point PX where the X-ray source 11 is located, and a magnification M2 when the subject W is at a position PS2 that is a distance D2 away from the point PX where the X-ray source 11 is located. Note that positions PS1 and PS2 are based on a rotation axis P1 of the stage 13 on which the subject W is placed. Also, distances D1 and D2 are FOD (Focus Object Distance).

[0056] The geometric magnification M1 at the position PS1 and the geometric magnification M2 at the position PS2 are given by the following equations (1) and (2), respectively. M1=L1 / D1 (1) M2=L1 / D2 (2)

[0057] Since the distance D2 is smaller than the distance D1, the enlargement magnification M2 at the position PS2 is larger than the enlargement magnification M1 at the position PS1.

[0058] More specifically, at a position PS1 that is a distance D1 away from the point PX where the X-ray source 11 is located, the size of the projection image of the subject W projected onto the detection area 12a of the detector 12 is height H1 and width W1. At the position PS1, the entire projection image of the subject W fits within the detection area 12a.

[0059] In contrast, at position PS2, which is closer to point PX where X-ray source 11 is located by Δx than position PS1, the size of the projection image of subject W projected onto detection region 12a of detector 12 is height H2 and width W2. The height H2 and width W2 of the projection image at position PS2 are greater than the height H1 and width W1 of the projection image at position PS1, respectively. At position PS1, a part of the projection image of subject W is outside the range of detection region 12a.

[0060] (Details of the imaging control unit) The details of the imaging control unit 30 will be described with reference to Figs. 1 to 3 as well as Figs. 4 to 7. Fig. 4 is a diagram showing the relationship between the detection area 12a and the target area TG1. Fig. 5 is a diagram showing the relationship between the detection area 12a and the target area TG2 after the target area TG1 has been enlarged. Fig. 6 is a diagram showing a state in which one end of the detection area 12a and one end of the enlarged target area TG2 are moved relatively in the Z-axis direction so as to coincide with each other. Fig. 7 is a diagram showing a state in which the other end of the detection area 12a and the other end of the enlarged target area TG2 are moved relatively in the Z-axis direction so as to coincide with each other.

[0061] The imaging control unit 30 controls the X-ray source 11, the detector 12, the rotation drive mechanism 14, the X-axis direction moving mechanism 15, and the Z-axis direction moving mechanism 16 to image the subject W. The imaging control unit 30 controls the rotation drive mechanism 14 to rotate the stage 13, and controls the Z-axis direction moving mechanism 16 to relatively move the stage 13, the X-ray source 11, and the detector 12 in the Z-axis direction based on an enlargement magnification that enlarges a target region TG1, which is a part of the detection region 12a, in the Y-axis direction while maintaining the ratio between the Y-axis direction and the Z-axis direction, to acquire projection data DP20.

[0062] Specifically, the shooting control unit 30 has an area setting unit 31, a magnification determination unit (shooting control unit) 32, a Z-axis direction movement amount determination unit 33, an X-axis direction movement control unit 34, and a Z-axis direction movement control unit (shooting control unit) 35.

[0063] The region setting unit 31 sets a target region TG1 to be enlarged in response to an operator's operation on the operation unit 51. For example, as shown in Fig. 4, the region setting unit 31 outputs a projection image PR1 to the display unit 52 by detecting X-rays irradiated to the subject W located at the position PS1 before enlargement with the detector 12. When a region of a portion of the projection image PR1 is specified on the operation unit 51, the portion of the projection image PR1 is set as the target region TG1. That is, the region setting unit 31 sets a portion of the detection region 12a in which the projection image PR1 is detected as the target region TG1.

[0064] The magnification determination unit 32 sets an enlargement magnification in accordance with the target region TG1. The magnification determination unit 32 determines, as the enlargement magnification, a magnification at which the target region TG1, which is a part of the detection region 12a, falls within the width DW1 of the detection region 12a in the Y-axis direction. According to the above-mentioned configuration, it is possible to prevent the enlargement magnification of the target region TG1 from being set beyond the range of the detection region 12a of the detector 12 in the Y-axis direction. This makes it possible to prevent projection data DP20 from being acquired in which the subject W extends beyond the detection region 12a in the Y-axis direction. Therefore, errors during imaging can be suppressed.

[0065] Here, the object W is wide or narrow at each position in the Z-axis direction. For example, the width of the object W in the Y-axis direction is W1 at its widest position and W10 at its narrowest position. The magnification determination unit 32 determines the enlargement magnification based on the position of the object W where the width in the Y-axis direction is widest. According to the above-mentioned configuration, even if the width in the Y-axis direction changes in the Z-axis direction, the object W can be made to fit within the detection region 12a. This makes it possible to prevent projection data DP20 from being acquired that causes the object W to protrude from the detection region 12a. Therefore, errors during imaging can be suppressed.

[0066] Moreover, the magnification determination unit 32 enlarges the target area TG1 based on the center C1 in the Z-axis direction of the projection image as shown in Figures 4 and 5. Therefore, when the target area TG1 is enlarged by the enlargement magnification, one end TG21 and the other end TG22 of the enlarged target area TG2 in the Z-axis direction are positioned outside the range of the detection area 12a as shown in Figure 5. That is, the height H2 of the enlarged target area TG2 becomes greater than the height DH1 of the detection area 12a in the Z-axis direction.

[0067] Moreover, the magnification determining unit 32 calculates the amount of movement in the X-axis direction according to the enlargement magnification.

[0068] The Z-axis direction movement amount determination unit 33 determines the movement amount in the Z-axis direction according to the enlargement magnification. Specifically, when the target area TG1 shown in FIG. 4 is enlarged by the enlargement magnification, the Z-axis direction movement amount determination unit 33 determines the movement amount in the Z-axis direction for photographing one end TG21 and the other end TG22 of the target area TG2 located outside the range of the detection area 12a in the Z-axis direction as shown in FIG. 5. As described above, since the center C1 in the Z-axis direction of the projected image is used as a reference, as shown in FIG. 5, one end of the target area TG2 in the Z-axis direction is shifted in one direction by Δz from one end of the detection area 12a. Also, the other end of the target area TG2 in the Z-axis direction is shifted in the other direction by Δz from the other end of the detection area 12a. Therefore, when the target area TG2 is moved in one direction in the Z-axis direction by Δz, the other end of the enlarged target area TG2 coincides with the other end of the detection area 12a. In this manner, the Z-axis direction movement amount determination unit 33 calculates the movement amount Δz in the Z-axis direction whereby the other end of the enlarged target area TG2 coincides with the other end of the detection area 12a.

[0069] The X-axis direction movement control unit 34 controls the X-axis direction movement mechanism 15 to relatively move the stage 13, the X-ray source 11, and the detector 12 in the X-axis direction according to the magnification and the movement amount in the X-axis direction determined by the magnification determination unit 32. The X-axis direction movement control unit 34 moves the stage 13 by ΔX in the other direction in the X-axis direction. As a result, the X-axis direction movement control unit 34 expands the target area TG1 of a part of the detection area 12a. As shown in FIG. 5, due to the expansion of the target area TG1, one end TG21 and the other end TG22 of the target area TG2 are outside the range of the detection area 12a. In the state shown in FIG. 5, the detector 12 obtains a projection image PR2 in which one end TG21 and the other end TG22 of the target area TG2 are outside the range. That is, only a part of the target area TG2 of the subject W is reflected in the projection image PR2.

[0070] The Z-axis direction movement control unit 35 controls the Z-axis direction movement mechanism 16 to relatively move the stage 13, the X-ray source 11, and the detector 12 in the Z-axis direction based on the movement amount Δz in the Z-axis direction determined by the Z-axis direction movement amount determination unit 33. The Z-axis direction movement control unit 35 moves the stage 13 in one direction in the Z-axis direction by the movement amount Δz. As a result, as shown in FIG. 6, the other end of the enlarged target area TG2 coincides with the other end of the detection area 12a in the Z-axis direction. Furthermore, the Z-axis direction movement control unit 35 moves the stage 13 in the other direction in the Z-axis direction in accordance with the rotation of the stage 13 for acquiring the projection data DP20.

[0071] In the above-described configuration, imaging can be performed by efficiently moving the stage 13. This can shorten the imaging time.

[0072] According to the configuration of the shooting control unit 30 described above, it is possible to easily realize an shooting control unit 30 that can determine the amount of movement in the Z-axis direction and the amount of movement in the X-axis direction according to the set magnification ratio.

[0073] (Specific examples of magnification calculations) A specific example will be given of the calculation of the enlargement magnification by the magnification determination unit 32 of the X-ray CT apparatus 1. In the following, the following parameters are used (see also Figs. 2 to 5).

[0074] Magnification at position PS1: M1 Resolution of the detection area 12a of the detector 12: width DW1 × height DH1 pixels Pixel size of detection area 12a: PxSz (mm) Size of target area TG1: width W1 x height H1 (=DH1) pixels Width of the target area TG2 after enlargement: W2 = DW1 pixels That is, in the following description, the height H1 of the target area TG1 before enlargement is the same as the height DH1 of the detection area 12a. Also, the width W2 of the target area TG2 after enlargement is the same as the width DW1 of the detection area 12a. Below, a case of calculating the enlargement ratio for enlarging the width W1 of the target area TG1 to the width DW1 of the detection area 12a will be described.

[0075] First, the magnification determination unit 32 calculates the pixel size of the specified target area TG1 in the detection area 12a.

[0076] As described above, the target region TG1 has a width W1 in the projection image at the magnification M1. Therefore, the size in pixels px(y) of the detection region 12a can be calculated by the following formula (3).

[0077] px(y) = W1 / M1 (3) In order to expand this pixel size px(y) to the width DW1 of the detection region 12a, the enlargement magnification M2 of the target region TG1 to be obtained can be calculated by the following formula (4).

[0078] M2 = DW1 / px(y) (4) Moreover, the distance D2 can be obtained by applying M2 to the above equation (2).

[0079] In the above manner, the magnification determination unit 32 calculates the magnification M2 and the position to which the stage 13 should be moved, i.e., the distance D2. The X-axis direction movement control unit 34 performs pulse conversion based on the difference Δx between the distances D1 and D2 calculated by the magnification determination unit 32, and generates a signal for operating the X-axis direction movement mechanism 15.

[0080] (Specific examples of calculation of movement amount) A specific example will be given of the calculation of the enlargement magnification by the Z-axis direction movement amount determination unit 33 of the X-ray CT apparatus 1. In the following, the parameters described in the specific example of the calculation of the enlargement magnification are used.

[0081] The Z-axis direction movement amount determination unit 33 calculates the size of one end TG21 and the other end TG22 of the target area TG2 that is located outside the range of the detection area 12a after enlarging the target area TG2 while maintaining the ratio between the Y-axis direction and the Z-axis direction, as shown in Figure 5.

[0082] First, the area of ​​the enlarged target area TG2 that is reflected as a projected image within the detection area 12a is calculated.

[0083] First, the ratio RT1 of the width W1 of the target region TG2 before enlargement to the width W2 of the target region TG2 after enlargement (that is, the width DW1 of the detection region 12a) is calculated using the following formula (6). RT1 = W1 / W2 (= W1 / DW1) (6) Since the ratios in the Y-axis direction and the Z-axis direction are the same, the size PH1 (see Figure 4) of the portion of the target region TG1 that fits within the detection region 12a after enlarging the target region TG1 in the Z-axis direction can be calculated using the following equation (7).

[0084] PH1 = H1 × RT1 (7) That is, the size of the portion of the target region TG1 that fits within the detection region 12a after enlargement within the range of width W1 × height H1 is width W1 × height PH1. Meanwhile, the size of the portion of the target region TG1 that falls outside the range of the detection region 12a after enlargement in the Z-axis direction can be calculated by the following formula (8).

[0085] XPH1=H1-PH1 (8) As described above, the magnification determination unit 32 enlarges the target area TG1 based on the center C1 in the Z-axis direction of the projection image. Therefore, in the Z-axis direction, the sizes of one end TG21 and the other end TG22 of the enlarged target area TG2 that are outside the range of the detection area 12a are the same. Therefore, in the Z-axis direction, the sizes of one end TG11 and the other end TG12 that are outside the range of the detection area 12a in the target area TG1 shown in FIG. 4 that are enlarged are also the same.

[0086] In the Z-axis direction, the size Δpz of each of the one end TG11 and the other end TG12 of the target region TG1 can be calculated by the following formula (9).

[0087] Δpz=XPH1 / 2 (9) Since the stage 13 on which the object W is placed is moved in the X-axis direction and then moved in the Z-axis direction, the magnification changes from M1 to M2 before and after the magnification caused by the movement in the X-axis direction as described above.

[0088] Δpz calculated by equation (9) is converted into a scale at the enlargement magnification M2 after enlargement of the target region TG1. This conversion can be obtained by the following equation (10).

[0089] Δz = Δpz × (M2 / M1) (10) Furthermore, the size of Δz in pixels can be converted to the size Δz (mm) in mm by the following equation (11).

[0090] Δz(mm)=Δz×(PxSz / M2) (11) The Z-axis direction movement amount determination unit 33 calculates the movement amount Δz (mm) in the Z-axis direction in the above manner. The Z-axis direction movement control unit 35 performs pulse conversion based on the movement amount Δz (mm) calculated by the Z-axis direction movement amount determination unit 33, and generates a signal for operating the Z-axis direction movement mechanism 16.

[0091] As described above, the X-ray CT apparatus 1 is an apparatus that reconstructs a tomographic image of the subject W based on the projection data DP20. The imaging control unit 30 of the X-ray CT apparatus 1 controls the rotation drive mechanism 14 to rotate the stage 13 relatively to the X-ray source 11 and the detector 12, and controls the Z-axis direction moving mechanism 16 to relatively move the stage 13 in the Z-axis direction based on the enlargement magnification that enlarges a target region TG1, which is a part of the detection region 12a, in the Y-axis direction while maintaining the ratio between the Y-axis direction and the Z-axis direction, to acquire the projection data DP20.

[0092] In the above-mentioned configuration, a part of the projection image can be enlarged by moving in the X-axis direction. Here, when a target region TG1 that is a part of the detection region 12a is enlarged, the enlarged target region TG2 may be located outside the range of the detection region 12a in the Z-axis direction. In the above-mentioned configuration, in order to image the part of the target region TG1 that is located outside the range of the detection region 12a, the subject W is imaged so as to move relatively in the Z-axis direction.

[0093] This allows the projected image to be enlarged in the width direction (Y-axis direction) and allows the entire subject to be imaged in the Z-axis direction.

[0094] Therefore, the image quality of the tomographic image of the entire subject can be improved, and the magnification can be easily set.

[0095] In addition, the shooting control unit 30 of the X-ray CT device 1 controls the X-axis direction moving mechanism 15 to move the stage 13 relatively in the X-axis direction based on the magnification ratio, thereby enlarging a target area TG1 that is a part of the detection area 12a, and then controls the rotation drive mechanism 14 to rotate the stage 13 relatively to the X-ray source 11 and the detector 12, and controls the Z-axis direction moving mechanism 16 to move the stage 13 and the X-ray source 11 relatively in the Z-axis direction to acquire projection data DP20.

[0096] In the above-described configuration, the stage 13 is moved in the X-axis direction based on the magnification ratio to enlarge the target region TG1, which is a part of the detection region 12a. After the movement in the X-axis direction, the stage 13 is rotated and moved in the Z-axis direction to obtain the projection data DP20. This allows the target region TG1, which is a part of the detection region 12a, to be efficiently enlarged.

[0097] (Operation flow of X-ray CT scanner) The flow of operations of the X-ray CT apparatus 1 will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the flow of a control method S1 of the X-ray CT apparatus 1.

[0098] First, in the control method S1 of the X-ray CT device 1, the X-ray CT device 1 executes a positioning step S11 in which the subject W is positioned in the X-axis direction so that the entire projection image of the subject W fits within the detection region 12a when viewed in the X-axis direction. For example, as shown in FIG. 2 and FIG. 3, the imaging control unit 30 controls the X-axis direction moving mechanism 15 to move the stage 13 to a position PS1. According to the above-mentioned configuration, even if the width in the Y-axis direction changes in the Z-axis direction when viewed in one direction, the subject W can be accommodated within the detection region 12a. This makes it possible to suppress the acquisition of projection data DP20 in which the subject W protrudes from the detection region 12a before the expansion of the target region TG1. This makes it possible to suppress errors during imaging or deterioration in image quality of the tomographic image.

[0099] Next, the region setting unit 31 executes a region setting step S12 for setting a target region TG1. As described above, the X-ray CT apparatus 1 outputs the projection image PR1 to the display unit 52. In addition, the X-ray CT apparatus 1 acquires, via the operation unit 51, a designation of a partial region of the projection image PR1 by the operator.

[0100] Next, the X-ray CT device 1 executes an enlargement step S13 in which the target region TG1, which is a part of the detection region 12a, is enlarged in the Y-axis direction while maintaining the ratio between the Y-axis direction and the Z-axis direction. In the enlargement step S13, the X-ray CT device 1 moves the stage 13 in the X-axis direction based on the enlargement magnification. In the above-mentioned configuration, the target region TG1, which is a part of the detection region 12a, is enlarged by moving the stage 13 in the X-axis direction based on the enlargement magnification. This allows the target region TG1, which is a part of the detection region 12a, to be efficiently enlarged.

[0101] Next, the X-ray CT device 1 rotates the stage 13 and moves the stage 13 in the Z-axis direction based on the magnification ratio in the magnification step S13, and executes a projection data acquisition step S14 in which the detector 12 acquires projection data DP20 by irradiating the subject W placed on the stage 13 with the X-rays.

[0102] Next, the X-ray CT apparatus 1 executes a reconstruction step S15 for reconstructing a tomographic image of the subject W based on the acquired projection data DP20.

[0103] In the above-described configuration, a part of the projection image can be enlarged by moving in the X-axis direction. Here, when a target region TG1 that is a part of the detection region 12a is enlarged, a part of the enlarged target region TG2 may be located outside the range of the detection region 12a in the Z-axis direction. In the above-described configuration, in order to image the part of the target region TG2 that is located outside the range of the detection region 12a, the subject W is imaged while being relatively moved in the Z-axis direction.

[0104] This allows the projection image to be enlarged in the width direction (Y-axis direction) and allows the entire subject W to be imaged in the Z-axis direction.

[0105] Therefore, the image quality of the entire tomographic image of the subject W can be improved, and the magnification can be easily set.

[0106] [Other embodiments] Although the embodiment of the present invention has been described above, the above-mentioned embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-mentioned embodiment, and the above-mentioned embodiment can be appropriately modified and carried out without departing from the spirit of the present invention.

[0107] In the embodiment, the imaging control unit 30 of the X-ray CT apparatus 1 executes a program to realize various functions. That is, the imaging control unit 30 is realized by software. However, the present invention is not limited to this, and the control unit may be realized by hardware such as a dedicated integrated circuit. The program may be stored in a computer-readable storage medium capable of storing data not temporarily but substantially. The storage medium may be a part of the storage unit of the X-ray CT apparatus. The program may be supplied to the X-ray CT apparatus via any wired or wireless transmission medium.

[0108] In the embodiment, the X-ray source 11 includes a microfocus X-ray tube with a focal spot of several micrometers to several tens of micrometers. However, the X-ray source may have a focal spot larger than the order of micrometers.

[0109] In the above embodiment, the X-ray source 11 has an X-ray optical axis AX extending in one horizontal direction. However, the X-ray optical axis of the X-ray source may be in the vertical direction or in another direction. For example, when the X-ray optical axis of the X-ray source is in the vertical direction, the stage may be capable of mounting the subject via a jig or the like. There is no limitation on the method of supporting the subject on the stage surface of the stage.

[0110] Although not specifically described in the above embodiment, the X-ray source, the detector, and the rotating table may each have a moving mechanism for moving in the Y-axis direction.

[0111] In the embodiment, the stage 13 is rotated by the rotation drive mechanism 14. However, the rotation drive mechanism may rotate the pair of the X-ray source and the detector relative to the subject. The rotation drive mechanism may relatively rotate at least one of the subject and the X-ray source that irradiates the subject with X-rays.

[0112] In the embodiment, the X-ray CT apparatus 1 stores the projection data DP20 in the storage unit 20. However, the X-ray CT apparatus may upload the projection images to an external server connected via a communication network.

[0113] In the embodiment, the reconstruction unit 40 reconstructs a tomographic image of the subject W based on the projection data DP20. However, the reconstruction unit may perform reconstruction based on the projection data that has been subjected to various correction processes. Also, the imaging control unit may perform various corrections on the projection data during imaging.

[0114] In the embodiment, the X-ray CT apparatus 1 performs a helical scan in which the stage 13 is rotated in a spiral shape to perform imaging. However, the X-ray CT apparatus may perform a non-helical scan in which the subject placed on the stage is irradiated with the X-rays while rotating the stage about the rotation axis without moving the stage in the Z-axis direction, thereby acquiring projection data by the detector. Alternatively, an offset scan may be performed in which the X-ray optical axis of the X-ray source and the detection area of ​​the detector are shifted in the Y-axis direction relative to the stage to perform imaging.

[0115] In the embodiment, the region setting unit 31 sets a target region TG1 to be enlarged in the projection image PR1 in response to an operator's operation on the operation unit 51. However, the region setting unit may recognize the contour of the subject by performing image processing on the projection image, and set the target region based on the recognized contour. The region setting unit may also set the target region based on a three-dimensional model of the subject obtained by reconstructing the projection data, rather than the projection image. That is, the region setting unit may set the target region based on the appearance of the three-dimensional model when viewed in any direction perpendicular to the rotation axis.

[0116] Although not specifically described in the above embodiment, after the projection data acquisition step of the control method for the X-ray CT apparatus, the stage may be returned to the position before the target region was enlarged.

[0117] Although not specifically described in the above embodiment, the imaging control unit 30 may start subsequent imaging when at least one of the relative movement in the X-axis direction or the relative movement in the Z-axis direction is not restricted after the enlargement magnification based on the target area TG1 is determined. For example, when the movement in the X-axis direction or the Z-axis direction accompanying the enlargement of the target area is a movement into a space where the movement is restricted by hardware or software, the imaging control unit may stop imaging. The restriction of the movement by hardware is a so-called hardware limit. When a sensor or the like detects that the subject or the stage has entered a space where the movement is restricted, the imaging control unit stops imaging.

[0118] Moreover, the software-based movement restriction is what is called a software limit. A space for restricting movement is set in the coordinate system of the three-dimensional space of the X-ray CT device. The imaging control unit judges whether or not the coordinates of the stage, etc., move into the space for restricting movement due to movement in the X-axis or Z-axis direction accompanying the expansion of the target area. If the imaging control unit judges that the coordinates of the stage, etc., move into the space for restricting movement, it stops imaging.

[0119] In the above-described configuration, it is possible to prevent the stage from moving into a space where movement is restricted as the target area expands, thereby suppressing the occurrence of unnecessary movement that would prevent imaging.

[0120] In the embodiment, the width W2 of the target region TG2 after the target region TG1 is enlarged is equal to the width DW1 of the detection region 12a. However, the width W2 of the target region TG2 may be greater than the width W1 of the target region TG1 and less than the width DW1 of the detection region 12a.

[0121] In the above embodiment, the imaging control unit 30 acquires the projection data DP20 while moving the stage 13 in one direction in the Z-axis direction, and then in the other direction in the Z-axis direction. However, the imaging control unit may acquire the projection data while moving the stage in one direction in the Z-axis direction, and then in the other direction in the Z-axis direction. The imaging control unit may also acquire the projection data while moving the stage back and forth in the Z-axis direction.

[0122] In the embodiment, the magnification determination unit 32 enlarges the target region TG1 based on the center C1 of the projected image in the Z axis direction. However, the magnification determination unit may enlarge the target region based on any position of the projected image in the Z axis direction.

[0123] In the embodiment, the magnification determination unit 32 calculates Δx by taking the distance D1 at the position PS1 and the distance D2 at the position PS2 as the FOD. However, the magnification determination unit may apply a correction value to the distance D1 and the distance D2. For example, the magnification determination unit may take the closest position between the object and the point where the X-ray source is located as the FOD. For this purpose, the magnification determination unit may apply the size of the object in the X-axis direction as a correction value to the distance D1 and the distance D2. Also, for example, when the object has a cylindrical shape when viewed in the Z-axis direction, the magnification determination unit may calculate the FOD at each position by subtracting the radius R of the cylinder as a correction value from the distance D1 and the distance D2. Also, the magnification determination unit may correct the position of the point where the X-ray source is located by a calibration value for each X-ray CT device. [Industrial Applicability]

[0124] The present invention can be used in an X-ray CT apparatus that obtains a tomographic image of a subject by irradiating the subject with X-rays. [Explanation of symbols]

[0125] 1 X-ray CT device 11 X-ray source 12 Detector 13 Stages 14 Rotational drive mechanism 15 X-axis direction movement mechanism 16 Z-axis direction movement mechanism 20 Memory section 30 Shooting control section 31 Area setting section 32 Magnification determination section 33 Z-axis direction movement amount determining section 34 X-axis direction movement control section 35 Z-axis direction movement control section 40 Reconstruction part 51 Operation section 52 Display section DP20 Projection Data W Subject

Claims

1. an X-ray source that irradiates X-rays in an X-axis direction; a detector having a detection area for the X-rays irradiated by the X-ray source; a stage located between the X-ray source and the detector and having a stage surface capable of supporting a subject; a rotation drive mechanism that rotates the stage relatively to the X-ray source and the detector around a rotation axis that is perpendicular to the irradiation direction of the X-rays and the stage surface of the stage; an X-axis direction movement mechanism that moves the stage relative to the X-ray source and the detector in the X-axis direction; a Z-axis direction movement mechanism that moves the stage, the X-ray source, and the detector relatively in a Z-axis direction, which is a direction along which the rotation axis extends; an imaging control unit that relatively rotates the stage positioned in the X-axis direction about the rotation axis and relatively moves the stage, the X-ray source, and the detector in the Z-axis direction, and irradiates the X-rays onto the subject supported on a surface of the stage, thereby acquiring projection data by the detector; having An X-ray CT apparatus that reconstructs a tomographic image of the subject based on the projection data, the imaging control unit controls the rotation drive mechanism to rotate the stage relatively, and controls the Z-axis direction moving mechanism to relatively move the stage in the Z-axis direction based on an enlargement magnification for enlarging a target area that is a part of the detection area in the Y-axis direction while maintaining a ratio between a Y-axis direction orthogonal to the X-axis direction and the Z-axis direction, respectively, to the Z-axis direction, thereby acquiring the projection data. X-ray CT device.

2. 2. The X-ray CT apparatus according to claim 1, the imaging control unit controls the X-axis direction moving mechanism to relatively move the stage in the X-axis direction based on the enlargement magnification, thereby enlarging a target area that is a part of the detection area, and then controls the rotation drive mechanism to rotate the stage relatively to the X-ray source and the detector, and controls the Z-axis direction moving mechanism to relatively move the stage and the X-ray source in the Z-axis direction, thereby acquiring projection data. X-ray CT device.

3. 2. The X-ray CT apparatus according to claim 1, The imaging control unit determines, as the enlargement magnification, a magnification at which a part of a target area of ​​the detection area falls within a range of the detection area in a Y-axis direction. X-ray CT device.

4. 2. The X-ray CT apparatus according to claim 1, The imaging control unit determines the enlargement magnification based on a position of the subject at which the width in the Y-axis direction is the widest. X-ray CT device.

5. 2. The X-ray CT apparatus according to claim 1, the imaging control unit performs control to relatively move the stage in one direction in the Z-axis direction until the other end of the enlarged target area coincides with the other end of the detection area in the Z-axis direction, and then performs control to relatively move the stage in the other direction in the Z-axis direction to obtain a projection image. X-ray CT device.

6. 6. The X-ray CT apparatus according to claim 1, The imaging control unit is A magnification determination unit that sets the enlargement magnification; a Z-axis movement amount determination unit that determines a movement amount in the Z-axis direction for capturing an image of a portion of the target area that is located outside the detection area in the Z-axis direction when enlarging the target area by the enlargement magnification; an X-axis direction movement control unit that controls the X-axis direction movement mechanism in accordance with the magnification ratio to relatively move the stage and the X-ray source in the X-axis direction; a Z-axis direction movement control unit that controls the Z-axis direction movement mechanism in accordance with the amount of movement in the Z-axis direction to relatively move the stage, the X-ray source, and the detector in the Z-axis direction; Including, X-ray CT device.

7. an X-ray source that irradiates X-rays in an X-axis direction; a detector having a detection area for X-rays irradiated by the X-ray source; a stage located between the X-ray source and the detector and having a stage surface capable of supporting a subject; having A control method for an X-ray CT apparatus for reconstructing a tomographic image of an object based on projection data acquired by a detector by irradiating the object supported on a stage surface with X-rays while rotating the stage relatively to the X-ray source and the detector about a rotation axis perpendicular to the irradiation direction of the X-rays and the stage surface of the stage, the control method comprising: an enlarging step of enlarging a part of a target area of ​​the detection area in a Y-axis direction while maintaining a ratio between a Y-axis direction perpendicular to the X-axis direction and a Z-axis direction in which the rotation axis extends, and the Z-axis direction; a projection data acquisition step of rotating the stage and relatively moving the stage, the X-ray source, and the detector in the Z-axis direction based on the magnification in the magnification step, to irradiate the subject placed or attached on the stage with the X-rays, thereby acquiring projection data by the detector; Including, A method for controlling an X-ray CT apparatus.

8. 8. The method for controlling an X-ray CT apparatus according to claim 7, In the enlarging step, the stage is moved in the X-axis direction based on the enlargement magnification. A method for controlling an X-ray CT apparatus.

9. 9. The method for controlling an X-ray CT apparatus according to claim 7, a positioning step of positioning the subject in the X-axis direction so that the entire subject falls within the detection region when viewed in at least one direction perpendicular to the rotation axis; In the enlarging step, the target region is enlarged while the subject is positioned in the X-axis direction. A method for controlling an X-ray CT apparatus.

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