X-ray image acquisition method

Abstract

To provide an X-ray image acquisition method capable of acquiring an X-ray image in which misalignment is corrected even when the relationship between the relative position and the posture between an X-ray imaging unit and a subject deviates from the reference state in a two-dimensional X-ray image that is taken while moving the X-ray imaging device and the subject relative to each other using a general motor.SOLUTION: An X-ray image acquisition method P in an embodiment includes; step P1 of capturing multiple calibration images of a calibration object; step P2 of calculating and recording image correction amounts for matching each calibration image to the reference image; step P3 of capturing multiple X-ray images of the subject from multiple shooting positions using the X-ray imaging unit; and step P4 of acquiring multiple images in which each of the multiple X-ray images of the object is corrected based on the image correction amount.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an X-ray image acquisition method.

Background Art

[0002] Conventionally, an invention related to an X-ray tomography apparatus that takes an X-ray fluoroscopic image of a subject while rotating and moving an X-ray source and a two-dimensional detector installed opposite to the X-ray source on a circular orbit plane having the same rotation center is known (see Patent Document 1 below). The X-ray tomography apparatus described in Patent Document 1 includes an X-ray source, two-dimensional X-ray imaging means, rotation means, a correction table, conversion means, and correction table creation means (paragraph 0031, claim 1, summary, and FIG. 1).

[0003] The above X-ray source irradiates X-rays in a conical shape. The above two-dimensional X-ray imaging means is arranged opposite to the X-ray source and takes an image of the X-rays transmitted through the subject. The above rotation means rotates and moves the X-ray source and the two-dimensional X-ray imaging means on a circular orbit having the same rotation center. The above correction table stores correction constants for correcting the distortion of the image caused by the two-dimensional X-ray imaging means. The above conversion means converts the image taken by the two-dimensional X-ray imaging means into predetermined orthogonal coordinates of the two-dimensional detection means based on the correction constants stored in the above correction table.

[0004] The above correction table creation means creates the above correction table based on a predetermined procedure. This correction table creation means includes coordinate axis correction table creation means for creating conversion constants in which the orthogonal coordinates are parallel and perpendicular to the rotation center axis. According to this conventional X-ray tomography apparatus, the image taken by the two-dimensional X-ray detection means can be corrected to an image parallel to the rotation center axis and perpendicular to the mid-plane (Patent Document 1, paragraph 0125).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The conventional X-ray tomography apparatus described above is premised on the use of a high-precision circular scanning drive means, which is generally used in medical CT apparatuses, as the rotation means (Patent Document 1, paragraphs 0052 and 0056, and Figure 1). Therefore, this conventional apparatus cannot use a general motor, such as that used in industrial robots, which increases the overall cost of the apparatus. Furthermore, this conventional apparatus makes it difficult to correct images when misalignment occurs between the subject and the X-ray source and two-dimensional X-ray imaging means in a direction parallel to the central axis of rotation.

[0007] The present disclosure provides an X-ray image acquisition method that can acquire an X-ray image with the deviation corrected even if the relative position and posture between the X-ray imaging device and the subject deviates from a reference state when a two-dimensional X-ray image is captured by moving the X-ray imaging device and the subject relative to each other using a general motor. [Means for solving the problem]

[0008] One aspect of the present disclosure is to dispose an X-ray imaging apparatus opposite to a calibration object having a rotationally symmetric three-dimensional shape and a plurality of portions having different radial dimensions orthogonal to the axis of symmetry, and to use a rotating device including a motor to move the calibration object and the X-ray imaging apparatus relative to each other about a rotation center axis aligned with the axis of symmetry of the calibration object. A step of taking a plurality of calibration images of the calibration object by the X-ray imaging apparatus from a plurality of imaging positions where the two-dimensional shape of the calibration object is the same; and a feature amount of a reference image of the calibration object taken by the X-ray imaging apparatus in a reference state where the three-dimensional orthogonal coordinate systems of the X-ray imaging apparatus and the calibration object are aligned, and a feature amount of each of the calibration images are compared to calculate and record an image correction amount for aligning each of the calibration images with the reference image; disposing a subject opposite to the X-ray imaging apparatus in the same manner as the calibration object, and using the rotating device to relatively rotate the X-ray imaging apparatus and the subject about the rotation center axis, and taking a plurality of X-ray images of the subject by the X-ray imaging apparatus from the plurality of imaging positions; and a step of obtaining a plurality of corrected images obtained by correcting each of the plurality of X-ray images of the subject based on the image correction amount. An X-ray image acquisition method characterized by comprising:

[0009] The X-ray image acquisition method according to the above aspect may include a step of constructing a three-dimensional CT image of the subject using the plurality of corrected images.

[0010] In the X-ray image acquisition method according to the above aspect, the rotating device may include a rotating support base that rotates about the rotation center axis while supporting the calibration object or the subject, and an industrial robot that disposes the X-ray imaging apparatus opposite to the calibration object or the subject.

[0011] In the X-ray image acquisition method according to the above aspect, the rotating device may include a mounting table for disposing the calibration object or the object on the rotation central axis, and an industrial robot for disposing the X-ray imaging device opposite to the calibration object or the object disposed on the mounting table and rotating the calibration object or the object around the rotation central axis.

[0012] In the X-ray image acquisition method according to the above aspect, the rotating device includes a first industrial robot for holding the calibration object or the object and disposing it on the rotation central axis, and a second industrial robot for holding the X-ray imaging device and facing it to the calibration object or the object, and at least one of the first industrial robot and the second industrial robot may relatively rotate the X-ray imaging device and the calibration object or the object around the rotation central axis.

Advantages of the Invention

[0013] According to each of the above aspects of the present disclosure, when a two-dimensional X-ray image is taken by relatively moving an X-ray imaging device and an object with a general motor, even if the relative position and posture relationship between the X-ray imaging device and the object deviates from the reference state, an X-ray image acquisition method capable of acquiring an X-ray image in which the deviation is corrected can be provided.

Brief Description of the Drawings

[0014] [Figure 1] Schematic configuration diagram showing the device configuration according to an embodiment of the X-ray image acquisition method of the present disclosure. [Diagram 2] Functional block diagram of the control device constituting the X-ray image acquisition device shown in FIG. 1. [Figure 3] Flow chart showing an embodiment of the X-ray image acquisition method according to the present disclosure. [Figure 4A] Perspective view showing the reference state of the X-ray imaging device and the calibration object in FIG. 1. [Figure 4B] Reference image taken by the X-ray imaging device in FIG. 4A. [Figure 5A]Perspective view showing the deviation of the calibration object from the reference state of the X-ray imaging apparatus of FIG. 1. [Figure 5B] Calibration image taken by the X-ray imaging apparatus of FIG. 5A. [Figure 6A] Perspective view showing the deviation of the calibration object from the reference state of the X-ray imaging apparatus of FIG. 1. [Figure 6B] Calibration image taken by the X-ray imaging apparatus of FIG. 6A. [Figure 7] Schematic configuration diagram showing a modified example of the X-ray image acquisition apparatus of FIG. 1. [Figure 8] Schematic configuration diagram showing a modified example of the X-ray image acquisition apparatus of FIG. 1.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the X-ray image acquisition method according to the present disclosure will be described with reference to the drawings.

[0016] FIG. 1 is a schematic configuration diagram showing an example of the apparatus configuration according to an embodiment of the X-ray image acquisition method of the present disclosure. FIG. 2 is a functional block diagram of the control device 4 that constitutes the X-ray image acquisition apparatus 1 shown in FIG. 1. FIG. 3 is a flowchart showing an embodiment of the X-ray image acquisition method according to the present disclosure.

[0017] The X-ray image acquisition method P of the present embodiment shown in FIG. 3 can be implemented, for example, by the X-ray image acquisition apparatus 1 as shown in FIG. 1. The X-ray image acquisition apparatus 1 includes, for example, an X-ray imaging apparatus 2, a rotation device 3, a control device 4, and a display device 5.

[0018] The X-ray imaging apparatus 2 includes, for example, an X-ray generator 21 and an X-ray detector 22. The X-ray generator 21 is controlled, for example, by a control signal CS21 input from the control device 4, and irradiates a conical X-ray beam (cone beam) onto a subject O disposed between the X-ray generator 21 and the X-ray detector 22. The X-ray detector 22 is controlled, for example, by a control signal CS22 input from the control device 4, detects the X-rays transmitted through the subject O, and outputs an X-ray image RI of the subject O corresponding to the detected X-rays to the control device 4.

[0019] The X-ray detector 22 can be configured, for example, by a flat panel detector, a combination of an image intensifier and a visible light sensor such as a CMOS sensor, an X-ray line sensor, etc. The X-ray generator 21 and the X-ray detector 22 output, for example, their respective operating states AS21 and AS22 to the control device 4.

[0020] The rotation device 3 includes, for example, at least one of a rotation support base 31 and an industrial robot 32. In the example shown in Fig. 1, the rotation device 3 is composed of one rotation support base 31 and two industrial robots 32. The rotation support base 31 and each of the industrial robots 32 are driven by a general industrial motor M, rather than a high-precision scanning drive device such as that used in a medical CT device.

[0021] The rotation support base 31 rotates, for example, a support base 311 supporting a subject O around a central rotation axis A perpendicular to the support base 311 by a motor M built into the rotation drive unit 312. The rotation drive unit 312 rotates the support base 311 in response to, for example, a control signal CS31 input from the control device 4, and outputs to the control device 4 a rotation angle θ31 of the support base 311 detected by an angle sensor.

[0022] The industrial robot 32 is, for example, a 4- to 7-axis vertical articulated robot, with a motor M and an encoder built into each joint. In the example shown in Fig. 1, an X-ray detector 22 of an X-ray imaging device 2 is attached to an attachment at the tip of a first industrial robot 32A, and an X-ray generator 21 of an X-ray imaging device 2 is attached to an attachment at the tip of a second industrial robot 32B. Control signals CS32A and CS32B are input from a control device 4 to each of the industrial robots 32A and 32B, and the industrial robots 32A and 32B output rotation angles θ32A and θ32B of their respective joints to the control device 4.

[0023] The control device 4 is composed of, for example, a central processing unit (CPU) (not shown), a memory, a timer, and one or more microcontrollers including an input / output unit. The control device 4 may include a storage device such as a hard disk, for example. As shown in FIG. 2, for example, the control device 4 has an X-ray imaging device control unit 41, a rotation device control unit 42, and an image processing unit 43. Each part of the control device 4 shown in FIG. 2 represents each function of the control device 4 realized by, for example, the CPU executing a program stored in the memory or the storage device.

[0024] The X-ray imaging device control unit 41 controls the operation of the X-ray imaging device 2. The X-ray imaging device control unit 41 includes, for example, an X-ray generator control unit 411 and an X-ray detector control unit 412. Based on the operation state AS21 input from the X-ray generator 21, the X-ray generator control unit 411 outputs a control signal CS21 to the X-ray generator 21 to control the start, stop, and output of X-ray irradiation by the X-ray generator 21. Based on the operation state AS22 input from the X-ray detector 22, the X-ray detector control unit 412 outputs a control signal CS22 to the X-ray detector 22 to control the detection conditions of X-rays by the X-ray detector 22.

[0025] The rotation device control unit 42 has, for example, a rotation support base control unit 421, a first robot control unit 422A, and a second robot control unit 422B. Based on the rotation angle θ31 of the support base 311 input from the rotation support base 31, the rotation support base control unit 421 outputs a control signal CS31 to the rotation drive unit 312 to control the rotation of the support base 311. Based on information such as the angles θ32A and θ32B of the respective joints input from the first and second industrial robots 32A and 32B, the first and second robot control units 422A and 422B output control signals CS32A and CS32B to these robots to control the operations of these robots.

[0026] The image processing unit 43 receives, for example, an X-ray image RI output from the X-ray detector 22 as input, and acquires a corrected image CRI by correcting the X-ray image RI. The image processing unit 43 also constructs a three-dimensional CT image 3DRI based on the acquired corrected image CRI, and outputs the image to the display device 5. The image processing unit 43 has, for example, an X-ray image collection unit 431, an X-ray image processing unit 432, a correction amount calculation unit 433, a correction amount storage unit 434, an X-ray image correction unit 435, and a three-dimensional image construction unit 436. The operation of each unit of the image processing unit 43 will be described later.

[0027] Next, a description will be given of an X-ray image acquisition method P of this embodiment using the above-mentioned X-ray image acquisition device 1. As shown in Fig. 3, when the X-ray image acquisition method P of this embodiment is started, a step P1 of capturing a calibration image is performed. In this step P1, for example, the X-ray imaging device 2 and a calibration subject CO (see Fig. 4A) are arranged opposite each other, and an X-ray image of the calibration subject CO is captured by the X-ray imaging device 2 to obtain a calibration image CI.

[0028] 4A is a perspective view showing a reference state of the X-ray imaging device 2 and calibration subject CO of FIG. 1. FIG. 4B is an image diagram showing an example of a reference image SI captured by the X-ray imaging device 2 of FIG. 4A. In step P1, first, the X-ray imaging device 2 and the calibration subject CO are arranged facing each other. More specifically, for example, the calibration subject CO is placed and fixed on the support base 311 of the rotating support base 31 of the X-ray image acquisition device 1.

[0029] Here, the calibration subject CO is formed of, for example, a material such as metal having a predetermined X-ray transmittance or X-ray absorption coefficient that allows X-ray images to be acquired, and has a rotationally symmetric three-dimensional shape. The calibration subject CO also has multiple portions with different radial dimensions perpendicular to the axis of symmetry. In the example shown in FIGS. 4A and 4B , the calibration subject CO has a cylindrical shape with different diameters at one end and a radial step at the center along the axis of symmetry. Information such as the three-dimensional shape and dimensions of the calibration subject CO is stored in advance in, for example, a memory or storage device that constitutes the image processing unit 43.

[0030] Note that the shape of the calibration object CO is not particularly limited as long as it has a rotationally symmetric three-dimensional shape and has a plurality of portions with different radial dimensions orthogonal to the axis of symmetry. The shape of the calibration object CO can adopt, for example, a shape other than a cylinder having a plurality of portions with different diameters, such as a cylindrical shape, a polygonal columnar or tubular shape, a single or a plurality of solid or hollow spherical shapes, or a shape having a plurality of concave and convex portions.

[0031] The calibration object CO is supported and fixed to the support base 311 of the rotary support base 31, for example, so that the axis of symmetry of the rotationally symmetric three-dimensional shape coincides with the rotation center axis A of the support base 311 of the rotary support base 31. Note that when the rotary support base 31 is not rotated during the shooting of the calibration image CI by the X-ray imaging apparatus 2 or when a non-rotating support base is used, the axis of symmetry of the calibration object CO is made to coincide with the rotation center axis A of the X-ray imaging apparatus 2 that rotates around the calibration object CO.

[0032] Next, as shown in FIG. 4A, the X-ray generator 21 and the X-ray detector 22 of the X-ray imaging apparatus 2 are opposed to the calibration object CO. More specifically, the operation of the first industrial robot 32A is controlled by the first robot control unit 422A of the control device 4 to move the X-ray generator 21 to face the calibration object CO. Also, the operation of the second industrial robot 32B is controlled by the second robot control unit 422B of the control device 4 to move the X-ray generator 21 to face the X-ray generator 21 with the calibration object CO interposed therebetween.

[0033] Here, FIG. 4A shows a reference state in which the three-dimensional orthogonal coordinate system of the X-ray imaging apparatus 2 coincides with the three-dimensional orthogonal coordinate system of the calibration object CO. Further, FIG. 4B shows a reference image SI which is an X-ray image of the calibration object CO taken by the X-ray imaging apparatus 2 in the reference state shown in FIG. 4A. That is, in the reference state, the width direction (X-axis direction), the depth direction (Y-axis direction), and the height direction (Z-axis direction) in the X-ray imaging apparatus 2 are parallel to the width direction (X-axis direction), the depth direction (Y-axis direction), and the height direction (Z-axis direction) in the calibration object CO, and the respective coordinate origins coincide.

[0034] In such a reference state, the operation of the X-ray generator 21 and the X-ray detector 22 of the X-ray imaging apparatus 2 is controlled by the X-ray generator control unit 411 and the X-ray detector control unit 412 of the control device 4 to capture a reference image SI which is an X-ray image of the calibration object CO. Note that the reference image SI of the calibration object CO can also be obtained by calculation based on the three-dimensional shape information of the calibration object CO and the positional relationship between the X-ray imaging apparatus 2 in the reference state and the calibration object CO. The reference image SI of the calibration object CO is input to, for example, the X-ray image acquisition unit 431 of the control device 4 and stored in a memory or a storage device constituting the image processing unit 43.

[0035] Next, the calibration object CO and the X-ray imaging apparatus 2 are relatively rotated about the rotation center axis A by the rotating device 3 including the motor M. More specifically, the support base 311 of the rotating support base 31 is rotated by the rotating support base control unit 421 of the control device 4, and the calibration object CO is rotated about the rotation center axis A of the rotating support base 31 which coincides with the symmetry axis of the calibration object CO. Alternatively, without rotating the support base 311 of the rotating support base 31, the operations of the first and second industrial robots 32A and 32B are controlled by the first robot control unit 422A and the second robot control unit 422B of the control device 4 to rotate the X-ray imaging apparatus 2 about the rotation center axis A around the calibration object CO.

[0036] Then, a plurality of calibration images CI of the calibration subject CO are captured by the X-ray imaging device 2 from a plurality of imaging positions where the two-dimensional shape of the calibration subject CO is the same. The X-ray detector 22 of the X-ray imaging device 2 outputs the captured calibration images CI to the image processing unit 43 of the control device 4. The image processing unit 43 stores the calibration images CI input from the X-ray detector 22 to the X-ray image collection unit 431 in a memory or storage device constituting the image processing unit 43, for example. This completes step P1 shown in FIG. 3.

[0037] 3, step P2 is performed to calculate and record image correction amounts. In step P2, the feature amounts of the reference image SI are compared with the feature amounts of the plurality of calibration images CI, and an image correction amount for matching each calibration image CI to the reference image SI is calculated and recorded. More specifically, the image processing unit 43, for example, calculates the feature amounts of the reference image SI and the feature amounts of each calibration image CI using the X-ray image collection unit 431.

[0038] Here, the reference image SI is an X-ray image of the calibration subject CO as shown in Fig. 4B, which is captured by the X-ray imaging device 2 in the reference state as shown in Fig. 4A, in which the three-dimensional Cartesian coordinate systems of the X-ray imaging device 2 and the calibration subject CO are aligned, as described above. The X-ray image acquisition unit 431 calculates the feature quantities of the reference image SI and each calibration image CI, such as the outline of the outer shape of the image of the calibration subject CO, the outline of the inner wall of the hollow calibration subject CO, or the shapes, dimensions, and positions of irregularities and steps.

[0039] 5A and 5B, and 6A and 6B respectively show a perspective view and a calibration image CI when the positional relationship between the X-ray imaging device 2 and the calibration subject CO deviates from the reference state.

[0040] As shown in FIG. 5A, as a result of relatively rotating the X-ray imaging apparatus 2 and the calibration object CO about the rotation center axis A by a rotating device 3 including a motor M, it is assumed that an angular deviation occurs in which the calibration object CO rotates about the Y axis. In this case, as shown in FIG. 5B, in the calibration image CI, the image of the calibration object CO is shifted from the image of the calibration object CO in the reference image SI by a predetermined angle about the Y axis perpendicular to the image plane.

[0041] Also, as shown in FIG. 6A, as a result of relatively rotating the X-ray imaging apparatus 2 and the calibration object CO about the rotation center axis A by a rotating device 3 including a motor M, it is assumed that an angular deviation occurs in which the calibration object CO rotates about the X axis. In this case, as shown in FIG. 5B, in the calibration image CI, in the vertical direction parallel to the Z axis, the dimension in the left-right direction parallel to the X axis is reduced toward the upper side of the image.

[0042] The X-ray image processing unit 432 calculates, for example, the feature amount of the calibration object CO in the reference image SI as shown in FIG. 4B and the feature amounts of each of the plurality of calibration images CI as shown in FIGS. 5B and 6B taken at a plurality of imaging positions on a circular orbit centered on the rotation center axis A. Then, the correction amount calculation unit 433 compares, for example, the feature amount of the reference image SI calculated by the X-ray image processing unit 432 with the feature amounts of the respective calibration images CI, and calculates an image correction amount for matching each calibration image CI with the reference image SI.

[0043] Note that the X-ray image processing unit 432 and the correction amount calculation unit 433 can similarly calculate feature amounts and calculate an image correction amount for the deviation of the calibration object CO in each axial direction of the three-dimensional orthogonal coordinate system in the calibration image CI. Further, the correction amount storage unit 434 stores the image correction amount of each calibration image CI calculated by the correction amount calculation unit 433 in a memory or a storage device constituting the image processing unit 43. Thus, the process P2 shown in FIG. 3 is completed. Thereafter, as shown in FIGS. 1 and 3, a process P3 of taking an X-ray image RI of the object O is performed.

[0044] In this step P3, first, similar to the calibration object CO, for example, an object O such as an automotive part and the X-ray imaging device 2 are arranged to face each other. More specifically, instead of the calibration object CO, the object O is placed on the support base 311 of the rotary support base 31. Then, the operation of the first and second industrial robots 32A and 32B is controlled by the rotation device control unit 42 of the control device 4, and the object O and the X-ray imaging device 2 are arranged to face each other in the same manner as the calibration object CO shown in FIG. 4A.

[0045] Thereafter, the rotation device 3 relatively rotates the X-ray imaging device 2 and the object O about the rotation center axis A, and the X-ray imaging device 2 captures a plurality of X-ray images RI of the object O. More specifically, for example, the rotation of the rotation drive unit 312 of the rotary support base 31 or the rotation operation of the first and second industrial robots 32A and 32B is controlled by the rotation device control unit 42 of the control device 4 to relatively rotate the X-ray imaging device 2 and the object O about the rotation center axis A.

[0046] Furthermore, the X-ray imaging device 2 is controlled by the X-ray imaging device control unit 41 of the control device 4 to capture X-ray images RI of the object O by the X-ray imaging device 2 from each of the imaging positions where the respective calibration images CI are obtained. The X-ray detector 22 outputs the plurality of captured X-ray images RI to the X-ray image collection unit 431 of the image processing unit 43. Thus, the step P3 shown in FIG. 3 is completed. Thereafter, the step P4 of obtaining the correction image shown in FIG. 3 is performed.

[0047] In this step P4, for example, the X-ray image correction unit 435 of the image processing unit 43 obtains a plurality of corrected images CRI obtained by correcting each of the plurality of X-ray images RI of the object O based on the image correction amount recorded in the correction amount storage unit 434 in the above-described step P2. More specifically, the X-ray image correction unit 435 uses, for example, the image correction amount for rotating the calibration image CI of the calibration object CO to match the reference image SI at the imaging position where the calibration image CI shown in FIG. 5B is captured, and corrects the X-ray image RI of the object O to obtain the corrected image CRI.

[0048] 6B, the X-ray image corrector 435 corrects the X-ray image RI of the subject O using an image correction amount that enlarges the reduced portion of the calibration image CI of the calibration subject CO to match it with the reference image SI, thereby acquiring a corrected image CRI. The X-ray image corrector 435 outputs the multiple corrected images CRI acquired by correcting each X-ray image RI using the image correction amount corresponding to each imaging position of the subject O to, for example, the three-dimensional image constructor 436.

[0049] This completes step P4 shown in Fig. 3. Thereafter, step P5 is performed to construct a three-dimensional computed tomography (CT) image, for example. In step P5, for example, a three-dimensional CT image 3DRI of the subject O is constructed by the three-dimensional image construction unit 436 of the image processing unit 43 using the multiple corrected images CRI. The three-dimensional image construction unit 436 outputs the constructed three-dimensional CT image 3DRI to the display device 5, for example.

[0050] The display device 5 is configured, for example, by a liquid crystal display device or an organic EL display device, and displays the three-dimensional CT image 3DRI of the subject O input from the three-dimensional image construction unit 436. This completes step P5 shown in Fig. 3, and all steps of the X-ray image acquisition method P of this embodiment.

[0051] As described above, the X-ray image acquisition method P of the present embodiment includes a step P1 of taking a plurality of calibration images CI, a step P2 of calculating and recording an image correction amount, a step P3 of taking a plurality of X-ray images RI of a subject O, and a step P4 of obtaining a plurality of corrected images CRI. In step P1, an X-ray imaging apparatus 2 and a calibration object CO having a rotationally symmetric three-dimensional shape and a plurality of portions having different radial dimensions orthogonal to the axis of symmetry are arranged to face each other. Then, the calibration object CO and the X-ray imaging apparatus 2 are relatively rotated about a rotation center axis A that coincides with the axis of symmetry of the calibration object CO by a rotating device 3 including a motor M. Then, a plurality of calibration images CI of the calibration object CO are taken by the X-ray imaging apparatus 2 from a plurality of imaging positions where the two-dimensional shape of the calibration object CO is the same. In step P2, the feature amount of a reference image SI of the calibration object CO taken by the X-ray imaging apparatus 2 in a reference state where the three-dimensional orthogonal coordinate systems of the X-ray imaging apparatus 2 and the calibration object CO coincide is compared with the feature amount of each calibration image CI. Then, an image correction amount for making each calibration image CI coincide with the reference image SI is calculated and recorded. In step P3, the subject O and the X-ray imaging apparatus 2 are arranged to face each other in the same manner as the calibration object CO. Then, the rotating device 3 relatively rotates the X-ray imaging apparatus 2 and the subject O about the rotation center axis A, and a plurality of X-ray images RI of the subject O are taken by the X-ray imaging apparatus 2 from the plurality of imaging positions. In step P4, a plurality of corrected images CRI obtained by correcting each of the plurality of X-ray images RI of the subject O based on the image correction amount are obtained.

[0052] In the X-ray image acquisition method P of the present embodiment, a general motor M such as that used in the rotary support base 31 of the X-ray imaging apparatus 2 or the industrial robot 32 is used to relatively rotate the X-ray imaging apparatus 2 and the subject O about the rotation center axis A to take a two-dimensional X-ray image. Therefore, unlike the high-precision scanning drive device used in a medical CT apparatus, the relative position and posture relationship between the X-ray imaging apparatus 2 and the subject O may deviate from the reference state. Even in such a case, in the X-ray image acquisition method P of the present embodiment, an image correction amount can be obtained and recorded in advance for each imaging position using the calibration object CO.

[0053] Therefore, according to the X-ray image acquisition method P of the present embodiment, the X-ray image RI of the subject O taken at each imaging position and including the deviation caused by the motor M can be corrected to a corrected image CRI without deviation using the image correction amount. As a result, the cost of the X-ray image acquisition device 1 can be reduced by using a general industrial motor M, and even when a positional deviation occurs in a direction parallel to the rotation center axis A between the X-ray imaging device 2 and the subject O, it is possible to obtain a corrected image CRI obtained by correcting the X-ray image RI.

[0054] In addition, the X-ray image acquisition method P of the present embodiment has a step P5 of constructing a three-dimensional CT image 3DRI of the subject O using a plurality of corrected images CRI. As a result, even when the relative position and posture relationship between the X-ray imaging device 2 and the subject O deviate from the reference state by using a general motor M, it is possible to construct a three-dimensional CT image 3DRI using the corrected image CRI in which the influence of the deviation is corrected.

[0055] In addition, in the X-ray image acquisition method P of the present embodiment, the rotating device 3 includes a rotation support base 31 and an industrial robot 32. The rotation support base 31 rotates about the rotation center axis A while supporting the calibration subject CO or the subject O. The industrial robot 32 arranges the X-ray imaging device 2 to face the calibration subject CO or the subject O. As a result, compared with the case of using a high-precision scanning drive device used in a medical CT device, the degree of freedom in the position where the X-ray imaging device 2 is installed is dramatically improved, and the restrictions on the size and shape of the subject O for which the X-ray image RI can be taken are significantly relaxed.

[0056] Furthermore, in the X-ray image acquisition method P of this embodiment, as described above, it is not necessary to rotate the calibration subject CO or subject O relative to the X-ray imaging device 2 using the rotary support table 31. That is, the rotation device 3 can include a mounting table for placing the calibration subject CO or subject O on the rotation center axis A, and an industrial robot 32 that faces the X-ray imaging device 2 toward the calibration subject CO or subject O placed on the mounting table. In this case, the industrial robot 32 rotates the X-ray imaging device 2 around the rotation center axis A around the calibration subject CO or subject O. This makes it possible to capture an X-ray image RI of a large subject O that is difficult to rotate using the rotary support table 31.

[0057] Fig. 7 is a schematic configuration diagram showing a modified example of the X-ray image acquisition device 1 of Fig. 1. In the X-ray image acquisition device 1 shown in Fig. 1, an example has been described in which the rotation device 3 is configured by one rotation support base 31 and two industrial robots 32, but the rotation device 3 can also be configured by, for example, one rotation support base 31 and one industrial robot 32. In this case, the rotation device 3 can be provided with a bracket 33 that supports the X-ray generator 21 and X-ray detector 22 of the X-ray imaging device 2 in a state where they face each other.

[0058] The bracket 33 is attached to, for example, an attachment at the tip of the industrial robot 32, and is supported above the calibration subject CO or subject O. In this state, the control device 4 rotates the rotary support base 31, or the control device 4 rotates the attachment at the tip of the industrial robot 32, thereby rotating the calibration subject CO or subject O and the industrial robot 32 relatively around the central axis of rotation A.

[0059] By using the X-ray image acquisition device 1 according to the modified example of Fig. 7, it is easier to adjust the relative positions of the calibration subject CO and the subject O and the X-ray imaging device 2 compared to the X-ray image acquisition method P according to the above-described embodiment, which uses the X-ray image acquisition device 1 shown in Fig. 1. This reduces the burden of adjusting the imaging system when taking an X-ray image RI of a portion or multiple locations of the subject O. In addition, it is also possible to replace the rotating support base 31 with a non-rotating mounting base and configure the rotation device 3 using only the industrial robot 32 and bracket 33.

[0060] FIG. 8 is a schematic diagram showing another modified example of the X-ray image acquisition device 1 of FIG. 1. In the X-ray image acquisition device 1 according to this modified example, the rotation device 3 includes a first industrial robot 32A and a second industrial robot 32B, and does not have a rotation support base 31. The first industrial robot 32A holds a calibration subject CO or subject O and places it on the rotation axis A. The second industrial robot 32B holds the X-ray imaging device 2 via a bracket 33 and faces the calibration subject CO or subject O, as in the modified example shown in FIG. 7. The rotation device 3 rotates the X-ray imaging device 2 and the calibration subject CO or subject O relatively around the rotation axis A using at least one of the first industrial robot 32A and the second industrial robot 32B.

[0061] 8, the X-ray image acquisition method P of this embodiment uses the X-ray image acquisition device 1 according to the modified example shown in Fig. 8, and controls the first industrial robot 32A by the control device 4 to automate the picking of the subject O, the capture of the X-ray image RI, and the transportation of the subject O after capture. Therefore, it is possible to improve the efficiency of acquiring the X-ray image RI and the corrected image CRI of the subject O.

[0062] As described above, according to the present embodiment and its modified examples, when a general motor M is used to relatively move the X-ray imaging apparatus 2 and the subject O to capture a two-dimensional X-ray image RI, even if the relative position and orientation relationship between the X-ray imaging apparatus 2 and the subject O deviate from the reference state, it is possible to provide an X-ray image acquisition method P capable of acquiring a corrected image CRI in which the deviation is corrected. Therefore, while reducing the cost of the X-ray image acquisition apparatus 1, it becomes possible to acquire a corrected image CRI in which the deviation of the X-ray image RI of the subject O caused by the motor M including the deviation in the direction parallel to the rotation center axis A is corrected.

[0063] As described above, the embodiments and modified examples of the X-ray image acquisition method according to the present disclosure have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments and modified examples, and even if there are design changes and the like within the scope not departing from the gist of the present disclosure, they are included in the present disclosure.

Explanation of Reference Numerals

[0064] 2 X-ray imaging apparatus 3 Rotation device 31 Rotation support base (mounting table) 32 Industrial robot 32A First industrial robot 32B Second industrial robot 3DRI 3D CT image A Rotation center axis CI Calibration image CO Calibration subject CRI Corrected image M Motor O Subject P X-ray image acquisition method P1 Step of capturing a calibration image P2 Step of calculating and recording the image correction amount P3 Step of capturing an X-ray image of the subject P4 Step of acquiring a corrected image P5 Step of constructing a 3D CT image RI X-ray image SI Reference image

Claims

1. An X-ray imaging apparatus and a calibration object having a rotationally symmetric three-dimensional shape and a plurality of portions having different radial dimensions orthogonal to the axis of symmetry are arranged to face each other, and the calibration object and the X-ray imaging apparatus are relatively rotated about a rotation center axis aligned with the axis of symmetry of the calibration object by a rotating device including a motor. A step of taking a plurality of calibration images of the calibration object by the X-ray imaging apparatus from a plurality of imaging positions where the two-dimensional shape of the calibration object is the same when no angular deviation occurs; A step of comparing a feature amount of a reference image of the calibration object taken by the X-ray imaging apparatus in a reference state where the three-dimensional orthogonal coordinate systems of the X-ray imaging apparatus and the calibration object are aligned, and a feature amount of each of the calibration images, and calculating and recording an image correction amount for matching each of the calibration images with the reference image; A step of arranging the object and the X-ray imaging apparatus to face each other in the same manner as the calibration object, and relatively rotating the X-ray imaging apparatus and the object about the rotation center axis by the rotating device, and taking a plurality of X-ray images of the object by the X-ray imaging apparatus from the plurality of imaging positions; A step of obtaining a plurality of corrected images obtained by correcting each of the plurality of X-ray images of the object based on the image correction amount; An X-ray image acquisition method, characterized by comprising the above steps.

2. The X-ray image acquisition method according to claim 1, further comprising a step of constructing a three-dimensional CT image of the object using the plurality of corrected images.

3. The rotating device according to claim 1, comprising: a rotating support base that rotates about the rotation center axis while supporting the calibration object or the object; and an industrial robot that arranges the X-ray imaging apparatus to face the calibration object or the object.

4. The rotating device according to claim 1, comprising: a mounting table for arranging the calibration object or the object on the rotation center axis; and an industrial robot that arranges the X-ray imaging apparatus to face the calibration object or the object arranged on the mounting table and rotates about the rotation center axis around the calibration object or the object.

5. The rotation device includes a first industrial robot for holding the calibration object or the object and disposing it above the rotation central axis, and a second industrial robot for holding the X-ray imaging device and facing it to the calibration object or the object. The X-ray image acquisition method according to claim 1, wherein at least one of the first industrial robot and the second industrial robot relatively rotates the X-ray imaging device and the calibration object or the object about the rotation central axis.

Images