X-ray imaging device

Abstract

This X-ray imaging device (100) comprises a rotation drive unit (31), movement units (32, 33, 34), and a control unit (40). The rotation drive unit (31) rotates an X-ray irradiation unit (10) about a rotation axis extending along the horizontal direction at a position spaced apart from the X-ray focal spot. The movement units (32, 33, 34) change the position of the X-ray irradiation unit (10) in an orthogonal plane orthogonal to the rotation axis. When the rotation drive unit (31) rotates the X-ray irradiation unit (10) from a first rotation angle to a second rotation angle, the control unit (40) causes the movement units (32, 33, 34) to operate such that the position of the X-ray focal spot at the second rotation angle matches the position of the X-ray focal spot at the first rotation angle.

Description

X-ray equipment

[0001] The present invention relates to an X-ray imaging apparatus.

[0002] BACKGROUND ART Conventionally, an X-ray imaging apparatus has been known. Such an X-ray imaging apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 2021-151387.

[0003] JP 2021-151387 A discloses an X-ray imaging device. This X-ray imaging device includes an X-ray irradiation unit that is moved by a movable device. The X-ray irradiation unit has an X-ray tube and a movable diaphragm device. The movable device includes a rotating structure that rotates the X-ray tube and the movable diaphragm device together around an axis that passes through the X-ray focal point (hereinafter referred to as the X-ray focal point) and is aligned horizontally. In the X-ray imaging device described in JP 2021-151387 A, the X-ray tube and the movable diaphragm device are moved together by the movable device including the rotating structure, either manually by an operator holding the X-ray irradiation unit or automatically through an input operation. Furthermore, in the X-ray imaging device described in JP 2021-151387 A, tomosynthesis imaging is performed to acquire multiple pieces of imaging image data corresponding to each of multiple irradiation directions by combining the sliding movement of the rotating structure in a direction parallel to the detection surface of the X-ray detector with the rotational movement of the X-ray irradiation unit by the rotating structure.

[0004] Japanese Patent Application Laid-Open No. 2021-151387

[0005] Here, although not described in the above-mentioned JP 2021-151387 A, when the weight of the X-ray tube (X-ray source) is small, the position of the center of gravity of the entire X-ray irradiation unit having the X-ray tube and the position of the X-ray focus are different from each other. In that case, as in the X-ray imaging device of the above-mentioned JP 2021-151387 A, when the X-ray irradiation unit is rotated around an axis that passes through the X-ray focus and is along the horizontal direction, the position of the rotation axis and the position of the center of gravity of the X-ray irradiation unit are different from each other, and the moment around the rotation axis becomes large. Therefore, when gripping and manually rotating the X-ray irradiation unit, an extra operating force is required to compensate for the moment due to the position of the center of gravity.

[0006] Therefore, it is conceivable to rotate the X-ray irradiator around an axis passing through the center of gravity of the X-ray irradiator rather than the X-ray focus. However, if the X-ray irradiator is rotated around a center of gravity of the X-ray irradiator that is different from the X-ray focus, the position of the X-ray focus will change as the rotation occurs. For example, when the rotation angle of the X-ray irradiator about the rotation axis is rotated from a first rotation angle to a second rotation angle, the position of the X-ray focus at the first rotation angle and the position of the X-ray focus at the second rotation angle will be different from each other. In this case, when imaging is performed while rotating the X-ray irradiator, such as in tomosynthesis imaging, as in the X-ray imaging apparatus described in JP 2021-151387 A, it is thought that abnormalities such as curvature of the tomographic plane may occur in the generated image due to changes in the position of the X-ray focus caused by the rotation. Therefore, it is desirable to suppress abnormalities in the generated image even when the rotation axis of the X-ray irradiator is separated from the X-ray focus.

[0007] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide an X-ray imaging device that can prevent abnormalities from occurring in the generated image even when the rotation axis of the X-ray irradiation unit is separated from the X-ray focal point.

[0008] According to one aspect of the present invention, an X-ray imaging apparatus includes an X-ray irradiator including an X-ray source, an X-ray detector that detects X-rays from the X-ray irradiator, a rotation driver that rotates the X-ray irradiator about a rotation axis extending horizontally at a position spaced apart from an X-ray focal point of the X-ray source, a mover that changes the position of the X-ray irradiator in an orthogonal plane perpendicular to the rotation axis, and a controller that, when the rotation driver rotates the X-ray irradiator about the rotation axis from a first rotation angle to a second rotation angle, operates the mover to match the position of the X-ray focal point at the second rotation angle with the position of the X-ray focal point at the first rotation angle. Note that in this specification, the term "match" is used as a broad concept that not only refers to the exact same position of the X-ray focal point but also includes errors due to device configuration or control processing.

[0009] In one aspect, the X-ray imaging apparatus includes a control unit that, when the rotation drive unit rotates the rotation angle of the X-ray irradiator about the rotation axis from the first rotation angle to the second rotation angle, operates the moving unit to make the position of the X-ray focal point at the second rotation angle coincide with the position of the X-ray focal point at the first rotation angle. By operating the moving unit to make the position of the X-ray focal point at the second rotation angle coincide with the position of the X-ray focal point at the first rotation angle, even when the position of the X-ray focal point and the position of the rotation axis differ from each other, the position of the X-ray focal point can be corrected to the same position as when the X-ray irradiator is rotated about an axis passing through the X-ray focal point. As a result, even when the rotation axis of the X-ray irradiator is separated from the X-ray focal point, it is possible to prevent abnormalities from occurring in the generated image.

[0010] FIG. 1 is a schematic diagram showing the overall configuration of an X-ray imaging apparatus according to an embodiment; FIG. 2 is a block diagram showing the overall configuration of an X-ray imaging apparatus according to an embodiment; FIG. 3 is a schematic diagram showing the configuration of an X-ray irradiation unit according to an embodiment; FIG. 4 is a block diagram showing the configuration of a control unit; FIG. 5 is a diagram for explaining a long image; FIG. 6 is a diagram for explaining a tomographic image; FIG. 7 is a diagram for explaining positional deviation of an X-ray focus in generating a long image; FIG. 8 is a diagram showing an example of deviation of a long image caused by positional deviation of an X-ray focus; FIG. 9 is a diagram for explaining correction of positional deviation of an X-ray focus in generating a long image; FIG. 10 is a diagram showing the positional relationship between a rotation axis, an X-ray focus, and a focus position; FIG. 11 is a diagram for explaining positional deviation of an X-ray focus in generating a tomographic image; FIG. 12 is a diagram for explaining correction of positional deviation of an X-ray focus in generating a tomographic image; FIG. 13 is a flowchart for explaining control processing of an X-ray imaging method using an X-ray imaging apparatus; FIG. 14 is a diagram for explaining correction of positional deviation of an X-ray focus in generating a tomographic image according to a modified example of the present invention.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] (Configuration of X-Ray Imaging Apparatus) The configuration of an X-ray imaging apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0013] 1 shows an example of a ceiling-suspended X-ray imaging device 100 installed in an imaging room 110. The X-ray imaging device 100 includes an X-ray irradiation unit 10, an X-ray detection unit 20, and a holding unit 30. The X-ray imaging device 100 includes a medical X-ray imaging device and is configured to perform X-ray imaging of a subject 101, which is the imaging target. In the X-ray imaging device 100, X-rays irradiated from the X-ray irradiation unit 10 are detected by the X-ray detection unit 20, thereby performing X-ray imaging of the subject 101.

[0014] In the ceiling-suspended X-ray imaging device 100, a holder 30 arranged on the ceiling surface of an imaging room 110 holds the X-ray irradiator 10. That is, the X-ray irradiator 10 is held so as to be suspended from the ceiling by the holder 30. The holder 30 is also arranged to be movable within the imaging room 110. The vertical (perpendicular) direction is defined as the Z direction, and two horizontal directions that are orthogonal to each other are defined as the X direction and the Y direction.

[0015] The X-ray imaging apparatus 100 includes an imaging table 21 for imaging a subject 101 in a lying position (supine position), and an imaging stand 22 for imaging a subject 101 in an upright position (standing position). An X-ray detection unit 20 is movably supported on each of the imaging table 21 and the imaging stand 22. The X-ray detection unit 20 includes, for example, a flat panel detector (FPD). The X-ray detection unit 20 is configured to detect X-rays irradiated from the X-ray irradiation unit 10 and transmitted through the subject 101. The holding unit 30 can move the X-ray irradiation unit 10 at least between an imaging position in a supine position using the imaging table 21 (see solid line in FIG. 1 ) and an imaging position in an upright position using the imaging stand 22 (see two-dot chain line in FIG. 1 ).

[0016] In X-ray imaging in a lying position, the X-ray detection unit 20 is placed on the imaging table 21 with its detection surface aligned horizontally. The holder 30 holds the X-ray irradiator 10 at a position facing the X-ray detection unit 20 on the imaging table 21 in the vertical direction. X-ray imaging of the subject 101 lying on the imaging table 21 is performed between the X-ray irradiator 10 and the X-ray detection unit 20, which are facing each other in the vertical direction (Z direction). In X-ray imaging in a standing position, the X-ray detection unit 20 is placed on the imaging stand 22 with its detection surface aligned vertically. The holder 30 holds the X-ray irradiator 10 at a position facing the X-ray detection unit 20 on the imaging stand 22 in the horizontal direction. X-ray imaging of the subject 101 standing in front of the imaging stand 22 is performed between the X-ray irradiator 10 and the X-ray detection unit 20, which are facing each other in the horizontal direction.

[0017] 4, the X-ray detection unit 20 moves horizontally on the radiography table 21 by the operation of a drive unit 21a. The X-ray detection unit 20 moves vertically on the radiography stand 22 by the operation of a drive unit 22a. Each of the drive units 21a and 22a has, for example, a servo motor as a drive source.

[0018] As shown in FIG. 2 , the X-ray irradiator 10 includes an X-ray tube 11, a collimator 12, and a gripper 13. The X-ray irradiator 10 is configured to irradiate the subject 101 with X-rays from the X-ray tube 11. The X-ray tube 11 is configured to irradiate X-rays by applying a predetermined voltage. The X-ray tube 11 irradiates X-rays radially from an X-ray focal point 11a (see FIG. 3 ). The collimator 12 has a plurality of position-adjustable shielding plates (collimator leaves). The collimator 12 is configured to define (adjust) the irradiation field of the X-rays irradiated from the X-ray tube 11 by shielding a portion of the X-rays from the X-ray tube 11. The collimator 12 is provided near the X-ray tube 11. The X-ray tube 11 is an example of an "X-ray source" in the claims.

[0019] As shown in FIG. 3 , the X-ray irradiator 10 is configured to be rotatable around a rotation axis 10a. That is, in the X-ray irradiator 10, the X-ray tube 11, the collimator 12, and the grip 13 rotate integrally around the rotation axis 10a. The rotation axis 10a is disposed to extend horizontally. The "horizontal direction" here refers to a direction parallel to a horizontal plane (XY plane) perpendicular to the Z direction, which is the vertical direction. For example, in FIG. 3 , the X-ray irradiator 10 is configured to be rotatable around the rotation axis 10a, which extends horizontally along the Y direction. The rotation axis 10a is disposed at a position spaced apart from the X-ray focal point 11a of the X-ray tube 11. The grip 13 is held by an operator when manually moving the X-ray irradiator 10. The gripping portion 13 is gripped by an operator when an operating force is applied to rotate the X-ray irradiation unit 10 about the rotation axis 10a. In this embodiment, the rotation axis 10a is located at the center of gravity of the entire X-ray irradiation unit 10, which includes the X-ray tube 11 and the collimator unit 12. In other words, the position of the X-ray focal point 11a is different from the position of the center of gravity of the entire X-ray irradiation unit 10. The X-ray irradiation unit 10 is configured to be able to change the X-ray irradiation direction (irradiation angle) by rotating about the rotation axis 10a, which is along the horizontal direction and passes through the center of gravity of the X-ray irradiation unit 10, which is different from the position of the X-ray focal point 11a.

[0020] As shown in FIG. 2 , the holding unit 30 includes a rotation drive unit 31, an elevation movement unit 32, a horizontal movement unit 33, and a horizontal movement unit 34. The holding unit 30 is configured to hold the X-ray irradiator 10 movably in the horizontal directions (X direction and Y direction) and the vertical direction (Z direction), and to rotatably hold the X-ray irradiator 10. The holding unit 30 is supported by rails provided on the ceiling surface of the imaging room 110 and is configured to be movable horizontally on the rails. The elevation movement unit 32 has a support unit that can extend and retract in the vertical direction. The X-ray irradiator 10 is disposed at the lower end of the support unit of the elevation movement unit 32. The elevation movement unit 32 extends and retracts the support unit to raise and lower the X-ray irradiator 10 in the vertical direction, i.e., the Z direction. The horizontal movement unit 33 translates the X-ray irradiator 10 in a horizontal plane along the X direction. The horizontal moving unit 34 translates the X-ray irradiator 10 in the Y direction within a horizontal plane. The horizontal moving units 33 and 34 are guided by rail members arranged on the ceiling surface, thereby moving the X-ray irradiator 10 in the X and Y directions, respectively. That is, the horizontal moving units 33 and 34 move the support column of the elevation moving unit 32 and the entire X-ray irradiator 10 in parallel along the horizontal plane. The elevation moving unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 are examples of a "moving unit" in the claims.

[0021] In this embodiment, the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 move the X-ray irradiator 10 vertically and the horizontal moving units 33 and 34 move the X-ray irradiator 10 horizontally, thereby changing the position of the X-ray irradiator 10 in an orthogonal plane perpendicular to the rotation axis 10a (see FIG. 3 ). The holder 30 rotatably holds the X-ray irradiator 10 at the tip of the support column of the lifting / lowering unit 32. The rotation drive unit 31 rotates the X-ray irradiator 10 around the rotation axis 10a (see FIG. 3 ). Each of the rotation drive unit 31, the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 has, for example, a servo motor as a drive source. The X-ray irradiator 10 is configured to be rotatable around the support column of the lifting / lowering unit 32, with the Z direction as its rotation axis.

[0022] 2, the X-ray imaging apparatus 100 includes a control unit 40 and an image processing unit 50. The control unit 40 controls the movement of the holding unit 30. Specifically, the control unit 40 controls the operations of the rotation drive unit 31, the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 by feedback control.

[0023] As shown in FIG. 4 , the control unit 40 includes controllers 41, 42, 43, 44, 45, and 46 and a system control unit 47. Each of the controllers 41, 42, 43, 44, 45, and 46 and the system control unit 47 includes a calculation device such as a central processing unit (CPU) and a storage device such as a memory. In each of the controllers 41, 42, 43, 44, 45, and 46 and the system control unit 47, the calculation device performs calculation processing based on programs and parameters stored in the storage device, thereby executing various control processes in the control unit 40. The controllers 41, 42, 43, and 44 control the operation of the rotation drive unit 31, the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34, respectively. The controllers 45 and 46 control the operation of the drive units 21a and 22a, respectively. The system control unit 47 controls the entire controllers 41 to 46. Controllers 41 to 46 generate drive signals for operating the respective servo motors of rotation drive unit 31, elevation movement unit 32, horizontal movement unit 33, horizontal movement unit 34, drive unit 21a, and drive unit 22a based on signals from system control unit 47. Controllers 41 to 46 generate drive signals through feedback control by obtaining feedback signals indicating the rotation angle of each servo motor from encoders arranged on each servo motor.

[0024] 5 and 6 , the image processing unit 50 acquires a detection signal from the X-ray detection unit 20 that detects X-rays from the X-ray irradiator 10, and generates an X-ray image 51 based on the acquired detection signal. In this embodiment, the image processing unit 50 generates a long image 52 and a tomographic image 53 as reconstructed images based on multiple X-ray images 51 captured at different rotation angles (irradiation directions) while the rotation drive unit 31 rotates the X-ray irradiator 10 around the rotation axis 10a. That is, the X-ray imaging device 100 is configured to perform irradiance imaging in which imaging is performed with the irradiation direction tilted with respect to a direction perpendicular to the detection surface of the X-ray detection unit 20. The X-ray imaging device 100 then generates a long image 52 and a tomographic image 53 as reconstructed images based on the multiple X-ray images 51 acquired by irradiance imaging. The image processing unit 50 includes, for example, a CPU, a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The image processing unit 50 may also include a processor such as a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array) configured for image processing.

[0025] 5 , the long image 52 is a reconstructed image generated by stitching together multiple X-ray images 51 captured by performing incident imaging. In this embodiment, the control unit 40 performs multiple X-ray imaging to generate the long image 52, with the irradiation directions being different from each other and the X-ray focal point 11a being positioned at a common focal position 70. For example, when generating the long image 52, the control unit 40 performs X-ray imaging in a standing position by moving the X-ray detection unit 20 in the vertical direction and rotating the X-ray irradiator 10 using the rotation drive unit 31 so that X-rays are irradiated toward the X-ray detection unit 20 moved in the vertical direction, thereby performing X-ray imaging while changing the irradiation direction.

[0026] Specifically, in X-ray imaging in a standing position, the control unit 40 moves the X-ray detection unit 20 to each of three different positions, position P1, position P2, and position P3. The control unit 40 performs X-ray imaging to generate a total of three X-ray images 51 with the X-ray detection unit 20 positioned at each of positions P1, P2, and P3. At this time, the control unit 40 changes the direction of X-ray irradiation by the X-ray irradiator 10 based on the movement distance of the X-ray detection unit 20 associated with the change in position and the SID (Source to Image Receptor Distance). The image processing unit 50 generates the three X-ray images 51 based on the detection results of the X-ray detection unit 20 at each of the three different positions, position P1, position P2, and position P3. The image processing unit 50 then vertically stitches together a plurality of X-ray images 51, each taken at a different position on the subject 101 in the vertical direction, to generate a long image 52. That is, the image processing unit 50 generates one long image 52 based on three X-ray images 51.

[0027] 6 , the tomographic image 53 is a reconstructed image generated by performing reconstruction processing on multiple X-ray images 51 captured by tomosynthesis imaging while changing the irradiation direction (rotation angle) through incident imaging, so as to show a cross-section of the subject 101 on a predetermined tomographic plane 53a. To generate the tomographic image 53, the control unit 40 captures multiple X-ray images 51, for example, by X-ray imaging in the supine position, while moving the X-ray irradiator 10 and the X-ray detector 20 using a parallel plane movement method. The control unit 40 sets the positions and orientations of the X-ray irradiator 10 and the X-ray detector 20 for generating the tomographic image 53 based on the position of the set tomographic plane 53a, the SID, and the imaging angle. In X-ray imaging in the supine position, the tomographic plane 53a is set as a plane along a horizontal plane parallel to the detection plane of the X-ray detector 20.

[0028] In tomosynthesis imaging, for example, a virtual fulcrum 53b is set at the center position of the slice plane 53a. Then, the X-ray focal point 11a moves on a focal point movement plane 80 parallel to the detection plane of the X-ray detection unit 20, and the rotation angle (irradiation direction) of the X-ray irradiator 10 is set so that the X-ray irradiation direction is directed toward the virtual fulcrum 53b. The controller 40 sets the position of the focal point movement plane 80 based on, for example, the input position of the slice plane 53a and the SID value. As an example, the controller 40 captures a total of 61 X-ray images 51 by moving the X-ray irradiator 10 and the X-ray detection unit 20 in parallel, opposing directions along the X direction by one degree each within a range from +30 degrees to −30 degrees, with the direction perpendicular to the detection plane being 0 degrees, based on the parallel plane movement method. That is, in tomosynthesis imaging, the image processor 50 generates 61 X-ray images 51 whose irradiation directions differ from each other by one degree each within a range from +30 degrees to −30 degrees. The image processing unit 50 then performs reconstruction processing on the captured 61 X-ray images 51 to generate one tomographic image 53 .

[0029] 7 , when capturing a plurality of X-ray images 51 for generating a long image 52, if the plurality of X-ray images 51 are captured while rotating the X-ray irradiator 10 with the position of the rotation axis 10a fixed, the position of the X-ray focal point 11a changes during capture of each of the plurality of X-ray images 51. For example, when the X-ray irradiator 10 is positioned so that X-rays are irradiated onto the X-ray detection unit 20 at position P1 as indicated by the solid line in FIG. 7 , and then the X-ray irradiator 10 is rotated while the position of the rotation axis 10a is fixed so that X-rays are irradiated onto the X-ray detection unit 20 at position P2 as indicated by the two-dot chain line in FIG. 7 , a positional deviation occurs in the X-ray focal point 11a due to the misalignment of the rotation axis 10a and the X-ray focal point 11a in the X-ray irradiator 10. That is, when the rotation angle of the X-ray irradiation unit 10 around the rotation axis 10a is rotated from a first rotation angle toward the X-ray detection unit 20 located at position P1 to a second rotation angle toward the X-ray detection unit 20 located at position P2, the position of the X-ray focal point 11a at the first rotation angle and the position of the X-ray focal point 11a at the second rotation angle are mutually different positions.

[0030] 8, a misalignment occurs in the portion where the X-ray images 51 are joined in the generated long image 52. For example, if X-ray imaging is performed on a rectangular parallelepiped subject 101a that is placed at a position corresponding to the portion where the X-ray images 51 are joined in the long image 52, with the X-ray focal points 11a positioned at different positions, a misalignment occurs in the subject 101a in the generated long image 52.

[0031] 9 , in this embodiment, when the rotation drive unit 31 rotates the X-ray irradiation unit 10, the control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 to correct the positional deviation of the X-ray focal point 11a caused by the distance s between the X-ray focal point 11a and the rotation axis 10a, based on the distance s between the X-ray focal point 11a and the rotation axis 10a and the rotation angle θ of the rotation of the X-ray irradiation unit 10 by the rotation drive unit 31. Specifically, when the rotation drive unit 31 rotates the X-ray irradiation unit 10 about the rotation axis 10a from the first rotation angle to the second rotation angle, the control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 based on the distance s and the rotation angle θ to match the position of the X-ray focal point 11a at the second rotation angle with the position of the X-ray focal point 11a at the first rotation angle. The control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 to align the position of the X-ray focal point 11a with the same position as when the X-ray irradiator 10 is not rotated, for each of the multiple X-ray images 51 to generate the long image 52, thereby correcting the positional deviation caused by the separation distance s. Specifically, the control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 to position the X-ray focal point 11a at a common focal position 70, which is a set predetermined position, for each of the multiple X-ray images 51 to be captured. That is, when the rotation drive unit 31 rotates the X-ray irradiator 10, the control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 so that the position of the X-ray focal point 11a aligns (does not change) before and after the rotation, regardless of the rotation angle.

[0032] When X-ray imaging is performed multiple times while the X-ray irradiation unit 10 is automatically rotated by the rotation drive unit 31, rather than when the X-ray irradiation unit 10 is rotated manually, the control unit 40 corrects the positional deviation of the X-ray focal point 11a in the X-Z plane, which is an orthogonal plane perpendicular to the rotation axis 10a, by operating the elevation movement unit 32 and the horizontal movement units 33 and 34 so that the position of the X-ray focal point 11a at the second rotation angle, which is the rotation angle after rotation, coincides with the position of the X-ray focal point 11a at the first rotation angle, which is the rotation angle without rotation, in each X-ray imaging. In other words, the control unit 40 corrects the positional deviation of the X-ray focal point 11a when the X-ray irradiation unit 10 is rotated by the driving force of the rotation drive unit 31 separately from the operating force applied to the gripper 13.

[0033] Specifically, the control unit 40 rotates the X-ray irradiator 10 by the rotation angle θ using the rotation drive unit 31 and moves the X-ray irradiator 10 parallel to a plane perpendicular to the rotation axis 10a so that the X-ray focal point 11a is located at the set focal point position 70. That is, when capturing multiple X-ray images 51 to generate a long image 52, the control unit 40 not only rotates the X-ray irradiator 10 using the rotation drive unit 31 but also translates the X-ray irradiator 10 using the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34, thereby placing the X-ray focal point 11a at the common focal point position 70. The control unit 40 obtains the rotation angle θ based on the set SID and the position at which the X-ray detection unit 20 is located for each capture. The rotation angle θ is, for example, an angle with a direction perpendicular to the detection surface of the X-ray detection unit 20 as a reference angle (0 degrees). That is, when a reference angle perpendicular to the detection surface is defined as a first rotation angle and a rotation angle toward the X-ray detection units 20 disposed at positions P1, P2, and P3 is defined as a second rotation angle, the control unit 40 acquires the angular difference between the first rotation angle and the second rotation angle as the rotation angle θ. The control unit 40 acquires the rotation angle θ of the X-ray irradiator 10 for imaging at each of positions P1, P2, and P3 based on the set SID and the positions of the centers of the detection surfaces of the X-ray detection units 20 at positions P1, P2, and P3. The control unit 40 corrects the position of the X-ray irradiator 10 in the XZ plane, which is an orthogonal plane perpendicular to the rotation axis 10a, based on the acquired rotation angle θ, thereby matching the position of the X-ray focal point 11a at the second rotation angle with the position of the X-ray focal point 11a at the first rotation angle.

[0034] For example, as shown in FIG. 10 , when the X-ray focal point 11a is located at focal position 70 and the X-ray irradiation direction is perpendicular to the detection surface of the X-ray detection unit 20 and oriented along the X direction, if the X-ray irradiator 10 is rotated around a rotation axis 10a extending along the Y direction by a rotation angle θ, the position of the X-ray focal point 11a in the XZ plane, which is an orthogonal plane perpendicular to the rotation axis 10a, shifts by s-s·cos θ in the X direction and by s·sin θ in the Z direction. Therefore, when rotating the X-ray irradiator 10 by a rotation angle θ around the rotation axis 10a extending along the Y direction, the controller 40 moves the X-ray irradiator 10 by s-s·cos θ in the X direction using the horizontal moving unit 33 and by s·sin θ in the Z direction using the elevation moving unit 32, thereby moving the X-ray irradiator 10 so that the X-ray irradiation direction is rotated by the rotation angle θ and the X-ray focal point 11a is positioned at the set common focal position 70. As a result, the controller 40 captures multiple X-ray images 51 with the X-ray focal point 11a positioned at the common focal position 70 but with different X-ray irradiation directions. The image processor 50 generates a long image 52 based on the multiple X-ray images 51 captured with the X-ray focal point 11a positioned at the common focal position 70. This corrects the positional deviation of the X-ray focal point 11a. When the X-ray irradiation unit 10 is rotated around the rotation axis 10a extending along the Y direction, the positional deviation of the X-ray focal point 11a is corrected by movement in the Z direction by the lifting / lowering unit 32 and movement in the X direction by the horizontal moving unit 33. However, when the rotation axis 10a is arranged to extend along the X direction, the positional deviation of the X-ray focal point 11a is corrected by movement in the Z direction by the lifting / lowering unit 32 and movement in the Y direction by the horizontal moving unit 34.

[0035] (Correction of X-ray Focus in Generation of Tomographic Image) Furthermore, as shown in FIG. 11 , the control unit 40 corrects the positional deviation of the X-ray focal point 11a caused by the separation distance s when capturing multiple X-ray images 51 for generating a tomographic image 53. X-ray imaging for generating the tomographic image 53 is performed using the parallel plane movement method. Here, as shown by the solid line in FIG. 11 , when the entire X-ray irradiator 10 is moved horizontally by the horizontal movement unit 33, the rotation axis 10a moves horizontally. In this case, when the X-ray irradiation direction is changed so as to move toward the virtual fulcrum 53b in conjunction with the horizontal movement of the X-ray irradiator 10, the greater the angle by which the irradiation direction is changed, the more the X-ray focal point 11a will be positioned at a position shifted in the Z direction from the focal point movement plane 80. In generating the tomographic image 53, if the X-ray focal point 11a is not positioned on a common plane for each of the multiple X-ray images 51 to be reconstructed, the tomographic plane 53a will not be flat and will be misaligned in the tomographic image 53 generated based on the multiple X-ray images 51. In other words, the tomographic plane 53a will be curved, and the tomographic image 53 will show a cross section along the curved surface of the subject 101.

[0036] 11 , if the X-ray irradiator 10 is rotated by a rotation angle θ from the vertical (Z direction) so that the irradiation direction is toward the virtual fulcrum 53b while moving horizontally with the rotation axis 10a fixed in position in the Z direction, the X-ray focal point 11a will be displaced downward in the Z direction from the focal point movement plane 80 due to the misalignment between the rotation axis 10a and the X-ray focal point 11a. Specifically, as shown by the solid line in Fig. 11 , if the X-ray irradiator 10 is placed at a position tilted by the rotation angle θ while moving the rotation axis 10a parallel to the X direction, the distance in the Z direction of the X-ray focal point 11a from the slice plane 53a will be D-s(1-cos θ), which is smaller than D, where D is the distance in the Z direction from the slice plane 53a to the set focal point movement plane 80.

[0037] Therefore, when the rotation drive unit 31 rotates the rotation angle of the X-ray irradiation unit 10 about the rotation axis 10a from the first rotation angle to the second rotation angle when capturing a plurality of X-ray images 51 for generating a tomographic image 53, the control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 based on the separation distance s and the rotation angle θ so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. Specifically, the control unit 40 operates the lifting / lowering unit 32, the horizontal moving unit 33, and the horizontal moving unit 34 so as to correct the positional deviation of the X-ray focal point 11a caused by the separation distance s for each capture of a plurality of X-ray images 51 for generating a tomographic image 53 so that the X-ray focal point 11a is positioned on a common focal point movement plane 80 as a predetermined position.

[0038] In X-ray photography for generating a tomographic image 53, the X-ray focal point 11a is positioned on a focal point movement plane 80 parallel to the tomographic plane 53a, and the lifting / lowering movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 are operated so that the X-ray focal point 11a is positioned on the common focal point movement plane 80 even when the X-ray irradiation unit 10 is rotated (when the rotation angle is the second rotation angle) from a state in which the X-ray focal point 11a is positioned on the focal point movement plane 80 when the X-ray irradiation unit 10 is not rotated (when the rotation angle is the first rotation angle). For example, the control unit 40 defines 0 degrees, which is the direction perpendicular to the detection surface, as the first rotation angle, and each rotation angle from +30 degrees to -30 degrees as the second rotation angle, and operates the lifting / lowering movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 so that the position of the X-ray focal point 11a at each of +30 degrees to -30 degrees in the parallel plane movement method coincides with the position where it would be located if the X-ray irradiation unit 10 were moved parallel to the slice plane 53a when the rotation angle is 0 degrees.

[0039] As shown in FIG. 12, for example, if the position of the X-ray focal point 11a when the rotation axis 10a is moved parallel to the XY plane at a rotation angle θ is separated from the ideal focal point position 80a on the focal point movement plane 80 by a distance δ, δ can be expressed by the following equation (1): Therefore, the control unit 40 moves the entire X-ray irradiation unit 10 by δ·sin θ in the X direction using the horizontal movement unit 33, and moves it by δ·cos θ in the Z direction using the elevation movement unit 32, thereby matching the position of the X-ray focal point 11a with the ideal focal point position 80a on the common focal point movement plane 80. δ·sin θ and δ·cos θ are expressed by the following equation (2). That is, δ is expressed by the separation distance s and the rotation angle θ. The ideal focal position 80a is the ideal position of the X-ray focal point 11a on the focal point movement plane 80 corresponding to the rotation angle θ. That is, in generating the tomographic image 53, the ideal focal position 80a corresponds to the position of the X-ray focal point 11a at the first rotation angle. Therefore, the ideal focal position 80a is a different position for each rotation angle θ.

[0040] When capturing the tomographic image 53, the control unit 40 calculates the amount of movement of the X-ray irradiator 10 in the X direction before correction for each rotation angle θ based on the distance D from the position of the set tomographic plane 53a to the position of the focal point movement plane 80 and the rotation angle θ, and calculates δ as a correction amount using the separation distance s and the rotation angle θ, thereby correcting the positional deviation so that the X-ray focal point 11a is positioned on the focal point movement plane 80 for each rotation angle θ. Specifically, from a state in which the X-ray focal point 11a and the rotation axis 10a are positioned directly above the virtual fulcrum 53b that is the center of the tomographic plane 53a, the control unit 40 moves the X-ray irradiator 10 parallel to the X direction by (D-s)·tan θ while rotating the X-ray irradiator 10 about the rotation axis 10a by the rotation angle θ, and also moves by δ·sin θ and δ·cos θ in the X direction and the Z direction, respectively, thereby positioning the X-ray focal point 11a at a position on the focal point movement plane 80 that corresponds to the rotation angle θ with the positional deviation corrected.

[0041] For example, when 61 X-ray images 51 are captured by performing tomosynthesis imaging at one-degree intervals within a range from +30 degrees to −30 degrees to generate a tomographic image 53, the control unit 40 calculates a correction amount δ for each of 60 positions corresponding to each of the 60 images 51 excluding 0 degree, based on the separation distance s and the rotation angle θ. Then, based on the δ calculated for each rotation angle θ, the control unit 40 operates the elevation movement unit 32 and the horizontal movement unit 33 so that the X-ray focal point 11a is positioned on the focal point movement plane 80 throughout the entire range from +30 degrees to −30 degrees. In this manner, the control unit 40 captures multiple X-ray images 51 with the X-ray focal point 11a positioned on a common focal point movement plane 80 and with different X-ray irradiation directions. The image processing unit 50 generates a tomographic image 53 based on the multiple X-ray images 51 captured with the X-ray focal point 11a positioned on the common focal point movement plane 80.

[0042] In both the case of X-ray imaging in an upright position with the X-ray detection unit 20 arranged vertically and the case of X-ray imaging in a lying position with the X-ray detection unit 20 arranged horizontally, when the rotation drive unit 31 rotates the X-ray irradiation unit 10 from the first rotation angle to the second rotation angle, the control unit 40 operates the lifting and lowering movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. That is, when the control unit 40 rotates the X-ray irradiation unit 10 using the rotation drive unit 31 in both the upright and supine positions, whether generating the long image 52 or the tomographic image 53, the control unit 40 corrects the positional deviation of the X-ray focus 11a by operating the lifting and lowering movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 so that the position of the X-ray focus 11a at the second rotation angle coincides with the position of the X-ray focus 11a at the first rotation angle.

[0043] (X-ray Imaging Method) Next, the control processing of the X-ray imaging method by the X-ray imaging apparatus 100 of this embodiment will be described with reference to Fig. 13. The control processing of the X-ray imaging method in steps 201 to 204 is executed by the control unit 40.

[0044] First, the separation distance s and the rotation angle θ are acquired in step 201. For example, the separation distance s, which is set and stored in advance, is acquired, and the rotation angle θ for each X-ray imaging is acquired based on the imaging conditions including the SID for acquiring each of the multiple X-ray images 51.

[0045] Next, in step 202, the amount of misalignment is calculated. The amount of misalignment is calculated based on the obtained separation distance s and rotation angle θ. For example, in X-ray imaging to generate long image 52 in an upright position, the values ​​of s-s·cos θ and s·sin θ are calculated as the amounts of misalignment in the X and Z directions, respectively. In addition, in X-ray imaging to generate tomographic image 53 in a supine position, the value of δ expressed by equation (1) is calculated, and the values ​​of δ·sin θ and δ·cos θ are calculated as the amounts of misalignment in the X and Z directions, respectively.

[0046] Next, in step 203, the amount of positional deviation is corrected. Based on the amount of positional deviation calculated in step 202, the position and irradiation direction of the X-ray irradiator 10 are calculated for each of the X-ray images 51, thereby correcting the amount of positional deviation. That is, based on the calculated position and irradiation direction of the X-ray irradiator 10, the control unit 40 rotates the X-ray irradiator 10 using the rotation drive unit 31, while operating the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 so as to correct the positional deviation of the X-ray focal point 11a. In other words, in step 203, when the control unit 40 rotates the rotation angle of the X-ray irradiation unit 10 around the rotation axis 10a by the rotation angle θ from the first rotation angle to the second rotation angle by the rotation drive unit 31, the control unit 40 operates the lifting and lowering movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 based on the separation distance s and the rotation angle θ so that the position of the X-ray focal point 11a at the second rotation angle after rotation matches the position of the X-ray focal point 11a at the first rotation angle without rotation.

[0047] Next, in step 204, X-ray imaging is performed by fluoroscopy in a state where the positional deviation of the X-ray focal point 11a in the X-ray irradiation unit 10 has been corrected. In other words, in this embodiment, when fluoroscopy is performed by rotating the X-ray irradiation unit 10 with the rotation drive unit 31, the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 are operated to perform X-ray imaging in a state where the positional deviation of the X-ray focal point 11a caused by the separation distance s between the X-ray focal point 11a and the rotation axis 10a has been corrected.

[0048] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0049] In this embodiment, as described above, the X-ray imaging apparatus 100 includes a control unit 40 that, when the rotation angle of the X-ray irradiator 10 about the rotation axis 10a is rotated from the first rotation angle to the second rotation angle by the rotation drive unit 31, operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. Thus, by operating the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle, even when the positions of the X-ray focal point 11a and the rotation axis 10a are different from each other, the position of the X-ray focal point 11a can be corrected to the same position as when the X-ray irradiator 10 is rotated about an axis passing through the X-ray focal point 11a. As a result, even when the rotation axis 10a of the X-ray irradiation unit 10 is separated from the X-ray focal point 11a, it is possible to prevent abnormalities from occurring in the generated images (long image 52 and tomographic image 53).

[0050] Furthermore, when the weight of the X-ray tube 11 (X-ray source) is small, it is possible to arrange a counterweight (weight) in the X-ray irradiator 10 to align the position of the center of gravity of the entire X-ray irradiator 10 with the position of the X-ray focal point 11a. However, in this case, the weight of the entire X-ray irradiator 10 increases due to the arrangement of the counterweight, which increases the load on the rotation drive unit 31 that rotates the X-ray irradiator 10 and the holder 30 that holds the X-ray irradiator 10. In contrast, in this embodiment, when the X-ray irradiator 10 is rotated from a first rotation angle to a second rotation angle, the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) are operated so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. This makes it possible to correct the position of the X-ray focal point 11a while suppressing an increase in the weight of the X-ray irradiator 10. Therefore, even when the rotation axis 10a of the X-ray irradiation unit 10 is separated from the X-ray focal point 11a, it is possible to prevent abnormalities from occurring in the generated images (long image 52 and tomographic image 53), and it is possible to prevent an increase in the load on the rotation drive unit 31 that rotates the X-ray irradiation unit 10 and the holding unit 30 that holds the X-ray irradiation unit 10.

[0051] Furthermore, in this embodiment, the following additional effects can be obtained by the following configuration.

[0052] That is, in this embodiment, as described above, when the control unit 40 rotates the X-ray irradiator 10 from the first rotation angle to the second rotation angle by the rotation drive unit 31, the control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle, based on the separation distance s between the X-ray focal point 11a and the rotation axis 10a and the rotation angle θ of the rotation of the X-ray irradiator 10 by the rotation drive unit 31. With this configuration, by using the separation distance s between the X-ray focal point 11a and the rotation axis 10a and the rotation angle θ of the rotation of the X-ray irradiator 10 by the rotation drive unit 31, it is possible to more accurately obtain the change in the position of the X-ray focal point 11a that occurs with the rotation of the X-ray irradiator 10. Therefore, the lifting / lowering movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 can be operated to more accurately correct the positional deviation of the X-ray focal point 11a, thereby more effectively preventing abnormalities from occurring in the generated long-length image 52 and tomographic image 53.

[0053] In this embodiment, the X-ray imaging apparatus 100 also includes an image processing unit 50 that generates a long image 52 and a tomographic image 53 (reconstructed image) based on a plurality of X-ray images 51 captured at different rotation angles θ while rotating the X-ray irradiation unit 10 by the rotation drive unit 31. The control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) for each capture of a plurality of X-ray images 51 for generating the long image 52 and the tomographic image 53, so as to align the X-ray focal point 11a with the same position as when the X-ray irradiation unit 10 is not rotated. With this configuration, for each capture of the multiple X-ray images 51, the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 are operated so that the X-ray focal point 11a coincides with the same position as when the X-ray irradiator 10 is not rotated, thereby correcting the position of the X-ray focal point 11a to the same position as when the X-ray irradiator 10 is rotated about an axis passing through the X-ray focal point 11a. Therefore, even when the rotation axis 10a of the X-ray irradiator 10 is separated from the X-ray focal point 11a, positional deviation can be corrected when capturing each of the multiple X-ray images 51, thereby preventing abnormalities from occurring in the long images 52 and the tomographic images 53 generated based on each of the multiple X-ray images 51.

[0054] Furthermore, in this embodiment, the control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement units) so that the X-ray focal point 11a is positioned at a predetermined position for each capture of the multiple X-ray images 51. With this configuration, by operating the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34, each of the multiple X-ray images 51 can be captured with the X-ray focal point 11a positioned at the predetermined position. Therefore, it is possible to easily prevent abnormalities from occurring in the long image 52 and the tomographic image 53 (reconstructed image) generated based on each of the multiple X-ray images 51.

[0055] In this embodiment, the image processing unit 50 generates a long image 52 (reconstructed image) based on the multiple X-ray images 51. The control unit 40 operates the elevator movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the X-ray focal point 11 a is positioned at a common focal position 70, which is a predetermined position, for each of the multiple X-ray images 51 captured to generate the long image 52. If the position of the X-ray focal point 11 a differs for each of the multiple X-ray images 51 captured, an abnormality such as a deviation in the position where the images are stitched together may occur in the long image 52 generated based on the multiple X-ray images 51. In contrast, in this embodiment, by operating the elevator movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34, each of the multiple X-ray images 51 can be captured with the X-ray focal point 11 a positioned at the common focal position 70. Therefore, even when a long image 52 is generated based on multiple X-ray images 51 taken while rotating the X-ray irradiation unit 10, abnormalities in the generated long image 52 can be effectively prevented.

[0056] In this embodiment, the image processing unit 50 generates a tomographic image 53 (reconstructed image) based on the multiple X-ray images 51. The control unit 40 operates the elevator movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the X-ray focal point 11a is positioned on a common focal point movement plane 80, which serves as a predetermined position, for each of the multiple X-ray images 51 captured to generate the tomographic image 53. If the X-ray focal point 11a is not positioned on a common plane for each of the multiple X-ray images 51 captured, the tomographic plane 53a in the tomographic image 53 generated based on the multiple X-ray images 51 will not be flat, resulting in a deviation. In contrast, in this embodiment, by operating the elevator movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34, each of the multiple X-ray images 51 can be captured with the X-ray focal point 11a positioned on the common focal point movement plane 80. Therefore, even when a tomographic image 53 is generated based on multiple X-ray images 51 taken while rotating the X-ray irradiation unit 10, abnormalities in the generated tomographic image 53 can be effectively prevented.

[0057] In this embodiment, the X-ray imaging apparatus 100 includes, as movement units, an elevation movement unit 32 that moves the X-ray irradiator 10 up and down, and a horizontal movement unit 33 and a horizontal movement unit 34 that translate the X-ray irradiator 10 in a horizontal plane. The control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. With this configuration, the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 move the X-ray irradiator 10 in an orthogonal plane, thereby easily correcting the positional deviation of the X-ray focal point 11a. Therefore, even when the rotation axis 10a of the X-ray irradiator 10 is separated from the X-ray focal point 11a, it is possible to prevent abnormalities from occurring in the generated long image 52 and tomographic image 53.

[0058] Furthermore, in this embodiment, the X-ray irradiator 10 includes a gripping unit 13 that is gripped by the operator when an operating force is applied to rotate the X-ray irradiator 10 about the rotation axis 10a. When the control unit 40 rotates the X-ray irradiator 10 by the driving force of the rotation drive unit 31 separately from the operating force applied to the gripping unit 13, the control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. With this configuration, since the X-ray irradiator 10 includes the gripping unit 13, by gripping the gripping unit 13, the X-ray irradiator 10 can be easily rotated by an operating force. Furthermore, when the X-ray irradiation unit 10 is rotated by the driving force of the rotation drive unit 31 separately from the operating force applied to the grip unit 13, the occurrence of abnormalities in the generated images can be suppressed by operating the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 to correct the positional deviation of the X-ray focal point 11a. As a result, the X-ray irradiation unit 10 can be easily rotated when rotated manually, and abnormalities in the long image 52 and the tomographic image 53 generated when the X-ray irradiation unit 10 is rotated automatically can be suppressed.

[0059] In this embodiment, the X-ray irradiation unit 10 includes a collimator unit 12 that defines an irradiation field of X-rays from the X-ray tube 11 (X-ray source). The rotation drive unit 31 rotates the X-ray irradiation unit 10 around a rotation axis 10a that is located at the center of gravity of the X-ray irradiation unit 10, including the collimator unit 12. When the rotation drive unit 31 rotates the X-ray irradiation unit 10 around the rotation axis 10a that is located at the center of gravity of the X-ray irradiation unit 10 and that differs from the position of the X-ray focal point 11a, the control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. With this configuration, the X-ray irradiation unit 10 can be configured to rotate about the rotation axis 10a passing through the center of gravity of the X-ray irradiation unit 10 including the collimator unit 12, thereby reducing the moment about the rotation axis 10a when rotating the X-ray irradiation unit 10. Therefore, when manually rotating the X-ray irradiation unit 10 including the collimator unit 12 about the rotation axis 10a, it is possible to suppress the need for excessive operating force.

[0060] Furthermore, in this embodiment, when the control unit 40 rotates the X-ray irradiation unit 10 using the rotation drive unit 31, whether the X-ray detection unit 20 is arranged vertically or horizontally, the control unit 40 operates the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) so that the position of the X-ray focal point 11a at the second rotation angle coincides with the position of the X-ray focal point 11a at the first rotation angle. With this configuration, whether the X-ray detection unit 20 is arranged vertically or horizontally, it is possible to prevent abnormalities from occurring in the generated long image 52 and tomographic image 53.

[0061] In this embodiment, the X-ray irradiator 10 is held by the holder 30 arranged on the ceiling surface. With this configuration, even when the X-ray irradiator 10 is held by the holder 30 arranged on the ceiling surface, the controller 40 can operate the elevation movement unit 32, the horizontal movement unit 33, and the horizontal movement unit 34 (movement unit) to correct the positional deviation of the X-ray focal point 11a, thereby preventing abnormalities from occurring in the generated images (the long image 52 and the tomographic image 53).

[0062] [Modifications] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above-mentioned embodiments, and further includes all modifications (modifications) within the meaning and scope of the claims.

[0063] For example, in the above embodiment, when the X-ray irradiation unit 10 is rotated around the rotation axis 10a along the Y direction, an example is shown in which the positional deviation is corrected by operating the elevation movement unit 32 and the horizontal movement unit 33 (movement unit) to change the position of the X-ray irradiation unit 10 in the XZ plane, but the present invention is not limited to this. In the present invention, when the X-ray irradiation unit is rotated around the rotation axis along the X direction, the positional deviation may be adjusted by moving the X-ray irradiation unit in the YZ plane, which is an orthogonal plane perpendicular to the rotation axis, using the movement unit.

[0064] In the above embodiment, in generating the tomographic image 53, the position of the rotation axis 10a is moved parallel to the XY plane by a distance corresponding to the rotation angle θ, and then the X-ray focal point 11a is corrected to be positioned on the focal point movement plane 80 by moving the rotation axis 10a in the horizontal direction (X direction) and the vertical direction (Z direction) by the operation of the elevator movement unit 32 and the horizontal movement unit 33 (movement unit) by a correction amount δ. However, the present invention is not limited to this. In the present invention, as shown in a modified example in Fig. 14, before rotating the X-ray irradiator 10, the X-ray irradiator 10 may be translated in the horizontal direction (X direction) so that the X-ray focal point 11a is positioned at the ideal focal point position 80a, and then the X-ray irradiator 10 may be rotated around the rotation axis 10a by the rotation angle θ, and the movement unit (elevation movement unit 32 and horizontal movement unit 33) may be operated to correct the positional deviation so that the X-ray focal point 11a is positioned at the ideal focal point position 80a. In this case, the movement (correction amount) due to the correction to the ideal focal position 80a is s·sin θ in the X direction and s−s·cos θ in the Z direction, based on the same concept as the correction in generating the long image 52. Note that although the calculation methods for the correction amount in the embodiment and the calculation method for the correction amount in the modified example are different, the positions of the X-ray irradiation unit 10 calculated ultimately are the same.

[0065] In addition, in the above embodiment, an example has been shown in which the X-ray irradiator 10 is held by the holder 30 arranged on the ceiling surface, but the present invention is not limited to this. In the present invention, the X-ray irradiator may be held by a holder arranged on the floor surface. That is, the X-ray imaging apparatus of this embodiment may be a ceiling-suspended (ceiling-traveling) X-ray imaging apparatus or a stationary X-ray imaging apparatus.

[0066] In the above embodiment, the positional deviation of the X-ray focal point 11a is corrected for each of the multiple X-ray images 51, but the present invention is not limited to this. In the present invention, when one X-ray image is captured by fluoroscopic imaging, the positional deviation of the X-ray focal point caused by the distance between the X-ray focal point and the rotation axis may be corrected.

[0067] Furthermore, in the above embodiment, the X-ray irradiator 10 includes the collimator 12 that defines the X-ray irradiation field. However, the present invention is not limited to this. In the present invention, the collimator may include an optical imaging unit including an image sensor that optically captures an image of the subject. In this case, the weight of the collimator increases due to the weight of the optical imaging unit, thereby increasing the distance between the X-ray focal point and the center of gravity of the X-ray irradiator. Therefore, when the rotation axis is positioned at the center of gravity, the distance between the X-ray focal point and the rotation axis of the X-ray irradiator increases. Therefore, when the X-ray irradiator is rotated, the X-ray focal point position shift becomes larger. Therefore, by operating the moving unit to align the X-ray focal point with the same position as when the X-ray irradiator is not rotated, as in the present embodiment, the X-ray focal point position shift can be corrected, thereby more effectively preventing abnormalities from occurring in the generated image.

[0068] In the above embodiment, the controllers 41, 42, 43, 44, 45, and 46 each include a calculation device such as a CPU and a storage device such as a memory, and the system control unit 47 are included, but the present invention is not limited to this. In the present invention, the control unit may be configured as any one of a personal computer, a processor, and a circuit, or a combination of these. Furthermore, each control process performed by the control unit may be performed by a combination of different hardware.

[0069] Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0070] (Item 1) An X-ray imaging device comprising: an X-ray irradiation unit including an X-ray source; an X-ray detection unit that detects X-rays from the X-ray irradiation unit; a rotation drive unit that rotates the X-ray irradiation unit around a rotation axis that extends along a horizontal direction at a position spaced apart from an X-ray focal point of the X-ray source; a movement unit that changes a position of the X-ray irradiation unit within an orthogonal plane that is perpendicular to the rotation axis; and a control unit that, when the rotation drive unit rotates the rotation angle of the X-ray irradiation unit around the rotation axis from a first rotation angle to a second rotation angle, operates the movement unit so that the position of the X-ray focal point at the second rotation angle coincides with the position of the X-ray focal point at the first rotation angle.

[0071] (Item 2) The X-ray imaging device according to Item 1, wherein when the rotation drive unit rotates the X-ray irradiation unit from the first rotation angle to the second rotation angle, the control unit operates the moving unit so as to match the position of the X-ray focal point at the second rotation angle with the position of the X-ray focal point at the first rotation angle based on a separation distance between the X-ray focal point and the rotation axis and a rotation angle of the rotation of the X-ray irradiation unit by the rotation drive unit.

[0072] (Item 3) The X-ray imaging device according to item 1 or 2, further comprising an image processing unit that generates a reconstructed image based on a plurality of X-ray images taken at mutually different rotation angles while rotating the X-ray irradiation unit by the rotation drive unit, wherein the control unit operates the moving unit to align the X-ray focal point with the same position as when the X-ray irradiation unit is not rotated, for each of the plurality of X-ray images taken to generate the reconstructed image.

[0073] (Item 4) The X-ray imaging device according to Item 3, wherein the control unit operates the moving unit so that the X-ray focal point is positioned at a set predetermined position for each of the plurality of X-ray images.

[0074] (Item 5) The X-ray imaging device according to Item 4, wherein the image processing unit generates the reconstructed image including a long image based on the plurality of X-ray images, and the control unit operates the moving unit so that the X-ray focal point is positioned at a common focal position as the predetermined position for each of the plurality of X-ray images taken to generate the long image.

[0075] (Item 6) The X-ray imaging device according to Item 4, wherein the image processing unit generates the reconstructed image including a tomographic image based on the plurality of X-ray images, and the control unit operates the moving unit so that the X-ray focal point is positioned on a common focal point moving plane as the predetermined position for each capture of the plurality of X-ray images for generating the tomographic image.

[0076] (Item 7) The X-ray imaging device according to any one of Items 1 to 6, wherein the movement unit includes an elevation movement unit that moves the X-ray irradiation unit up and down and a horizontal movement unit that moves the X-ray irradiation unit in parallel within a horizontal plane, and the control unit operates the elevation movement unit and the horizontal movement unit so that the position of the X-ray focal point at the second rotation angle coincides with the position of the X-ray focal point at the first rotation angle.

[0077] (Item 8) The X-ray imaging device according to any one of Items 1 to 7, wherein the X-ray irradiation unit includes a gripping unit that is gripped by an operator when an operating force is applied to rotate the X-ray irradiation unit around the rotation axis, and the control unit, when rotating the X-ray irradiation unit by a driving force of the rotation drive unit separately from the operating force applied to the gripping unit, operates the moving unit to make the position of the X-ray focal point at the second rotation angle coincide with the position of the X-ray focal point at the first rotation angle.

[0078] (Item 9) The X-ray imaging device according to any one of Items 1 to 8, wherein the X-ray irradiation unit includes a collimator unit that defines an irradiation field of X-rays from the X-ray source, the rotation drive unit rotates the X-ray irradiation unit around the rotation axis that is located at the center of gravity of the X-ray irradiation unit that includes the collimator unit, and the control unit operates the moving unit to make the position of the X-ray focal point at the second rotation angle coincide with the position of the X-ray focal point at the first rotation angle when the rotation drive unit rotates the X-ray irradiation unit around the rotation axis that is located at the center of gravity of the X-ray irradiation unit that is different from the position of the X-ray focal point.

[0079] (Item 10) The X-ray imaging device according to any one of Items 1 to 9, wherein when the control unit rotates the X-ray irradiation unit using the rotation drive unit, the control unit operates the moving unit so that the position of the X-ray focal point at the second rotation angle coincides with the position of the X-ray focal point at the first rotation angle, regardless of whether the X-ray detection unit is arranged along the vertical direction or along the horizontal direction.

[0080] (Item 11) The X-ray imaging device according to any one of Items 1 to 10, wherein the X-ray irradiation unit is held by a holder arranged on a ceiling surface.

[0081] REFERENCE SIGNS LIST 10 X-ray irradiation unit 11 X-ray tube (X-ray source) 12 Collimator unit 13 Grip unit 20 X-ray detection unit 30 Holding unit 31 Rotation drive unit 32 Elevation movement unit (moving unit) 33 Horizontal movement unit (moving unit) 34 Horizontal movement unit (moving unit) 40 Control unit 50 Image processing unit 51 X-ray image 52 Long-length image 53 Tomographic image 70 Focal position 80 Focal movement plane 100 X-ray imaging device 101 Subject

Claims

1. An X-ray imaging device comprising: an X-ray irradiation unit including an X-ray source; an X-ray detection unit that detects X-rays from the X-ray irradiation unit; a rotation drive unit that rotates the X-ray irradiation unit around a rotation axis that extends along a horizontal direction at a position spaced apart from the X-ray focal point of the X-ray source; a movement unit that changes the position of the X-ray irradiation unit within an orthogonal plane that is perpendicular to the rotation axis; and a control unit that, when the rotation drive unit rotates the rotation angle of the X-ray irradiation unit around the rotation axis from a first rotation angle to a second rotation angle, operates the movement unit so that the position of the X-ray focal point at the second rotation angle coincides with the position of the X-ray focal point at the first rotation angle.

2. The X-ray imaging device of claim 1, wherein when the control unit rotates the X-ray irradiation unit from the first rotation angle to the second rotation angle using the rotation drive unit, the control unit operates the moving unit so that the position of the X-ray focus at the second rotation angle coincides with the position of the X-ray focus at the first rotation angle based on the distance between the X-ray focal point and the rotation axis and the rotation angle of the rotation of the X-ray irradiation unit using the rotation drive unit.

3. The X-ray imaging device according to claim 1, further comprising an image processing unit that generates a reconstructed image based on a plurality of X-ray images taken at mutually different rotation angles while rotating the X-ray irradiation unit using the rotation drive unit, wherein the control unit operates the moving unit so that the X-ray focus is aligned at the same position as when the X-ray irradiation unit is not rotated, for each of the plurality of X-ray images taken to generate the reconstructed image.

4. The X-ray imaging device according to claim 3, wherein the control unit operates the moving unit so that the X-ray focus is positioned at a predetermined set position for each of the plurality of X-ray images.

5. The X-ray imaging device of claim 4, wherein the image processing unit generates the reconstructed image including a long image based on the plurality of X-ray images, and the control unit operates the moving unit so that the X-ray focal point is positioned at a common focal position as the predetermined position for each of the plurality of X-ray images taken to generate the long image.

6. The X-ray imaging device of claim 4, wherein the image processing unit generates the reconstructed image including a tomographic image based on the plurality of X-ray images, and the control unit operates the moving unit so that the X-ray focal point is positioned on a common focal point moving plane as the predetermined position for each of the plurality of X-ray images taken to generate the tomographic image.

7. The X-ray imaging device of claim 1, wherein the moving unit includes an elevation moving unit that moves the X-ray irradiation unit up and down, and a horizontal moving unit that moves the X-ray irradiation unit in parallel within a horizontal plane, and the control unit operates the elevation moving unit and the horizontal moving unit so that the position of the X-ray focal point at the second rotation angle coincides with the position of the X-ray focal point at the first rotation angle.

8. The X-ray imaging device of claim 1, wherein the X-ray irradiation unit includes a gripping unit that is gripped by an operator when an operating force is applied to rotate the X-ray irradiation unit around the rotation axis, and the control unit, when rotating the X-ray irradiation unit by a driving force of the rotation drive unit separately from the operating force applied to the gripping unit, operates the moving unit so that the position of the X-ray focal point at the second rotation angle coincides with the position of the X-ray focal point at the first rotation angle.

9. The X-ray imaging device of claim 1, wherein the X-ray irradiation unit includes a collimator unit that defines an irradiation field of X-rays from the X-ray source, the rotation drive unit rotates the X-ray irradiation unit around the rotation axis that is located at the center of gravity of the X-ray irradiation unit that includes the collimator unit, and the control unit operates the moving unit so that the position of the X-ray focus at the second rotation angle coincides with the position of the X-ray focus at the first rotation angle when the rotation drive unit rotates the X-ray irradiation unit around the rotation axis that is located at the center of gravity of the X-ray irradiation unit that is different from the position of the X-ray focus.

10. The X-ray imaging device of claim 1, wherein when the control unit rotates the X-ray irradiation unit using the rotation drive unit, the control unit operates the moving unit so that the position of the X-ray focus at the second rotation angle coincides with the position of the X-ray focus at the first rotation angle, regardless of whether the X-ray detection unit is arranged vertically or horizontally.

11. The X-ray imaging device according to claim 1, wherein the X-ray irradiation unit is held by a holder disposed on the ceiling surface.

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