X-ray imaging device

Abstract

This X-ray imaging device (100) comprises a control unit (32) that calculates the distance (D1) between an X-ray tube (11) and a subject (101) on the basis of the coordinates of a prescribed position (33c) in an irradiation field region (33a) captured on the body surface of the subject (101) in an optical image (70) that is captured by an optical imaging unit (31).

Description

X-ray equipment

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

[0002] 2. Description of the Related Art Conventionally, an X-ray imaging device including an optical imaging unit has been known. Such an X-ray imaging device is disclosed, for example, in Japanese Patent Application Laid-Open No. 2012-147978.

[0003] Japanese Patent Application Laid-Open Publication No. 2012-147978 describes an X-ray imaging device that includes a camera (optical imaging unit) attached to an X-ray tube that captures an image of a subject, and a control unit that recognizes the position of the subject from the image captured by the camera.

[0004] JP 2012-147978 A

[0005] When irradiating a subject with X-rays using an X-ray imaging device such as that disclosed in JP 2012-147978 A, an operator (a medical professional such as a radiologist or a doctor) must determine appropriate X-ray conditions for the subject (such as the X-ray dose to be irradiated to the subject). Therefore, although not described in JP 2012-147978 A, in order for the operator to determine appropriate X-ray conditions for the subject, in an X-ray imaging device such as that disclosed in JP 2012-147978 A, a control unit specifies a point for calculating the X-ray tube-subject distance between the X-ray tube and the subject from a distance value map (an image including distance information) obtained by imaging with a 3D camera, and calculates the X-ray tube-subject distance between the X-ray tube and the subject. In this case, a relatively expensive 3D camera is required. Therefore, a configuration capable of calculating the X-ray tube-subject distance without using a 3D camera is desired.

[0006] 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 is capable of calculating the X-ray tube-subject distance without using a 3D camera.

[0007] An X-ray imaging device according to one aspect of the present invention includes an X-ray irradiation unit including an X-ray tube, an X-ray detection unit that detects X-rays irradiated from the X-ray tube and transmitted through a subject, a light source unit that irradiates visible light onto an irradiation field area indicating an area irradiated with X-rays from the X-ray tube, an optical imaging unit that has an optical axis shifted from the irradiation axis of the X-rays irradiated from the X-ray tube and captures an optical image of the subject, and a control unit that calculates an X-ray tube-subject distance between the X-ray tube and the subject based on the coordinates of a predetermined position within the irradiation field area of ​​the light source unit that appears on the body surface of the subject in the optical image captured by the optical imaging unit.

[0008] In one aspect, the X-ray imaging device includes a control unit that calculates the X-ray tube-subject distance between the X-ray tube and the subject based on the coordinates of a predetermined position within the irradiation field area of ​​the light source unit that is captured on the body surface of the subject in the optical image captured by the optical imaging unit. This allows the X-ray tube-subject distance to be calculated geometrically based on the coordinates of the predetermined position within the irradiation field area of ​​the light source unit that is captured on the body surface of the subject in the optical image. In this case, the optical image may be captured by a monocular camera. As a result, the X-ray tube-subject distance can be calculated without using a 3D camera.

[0009] FIG. 1 is a schematic diagram showing the overall configuration of an X-ray imaging apparatus according to a first embodiment. FIG. 2 is a schematic diagram showing the configuration of a holding unit according to the first embodiment. FIG. 3 is a block diagram showing the overall configuration of an X-ray imaging apparatus according to the first embodiment. FIG. 4 is a schematic diagram showing an optical image generated by an optical imaging control unit of the X-ray imaging apparatus according to the first embodiment. FIG. 5 is a schematic diagram for explaining an optical image in which a detection unit region display, an irradiation field region display, and an AEC region display are superimposed on an optical image in the X-ray imaging apparatus according to the first embodiment. FIG. 6 is a schematic diagram (1) for explaining calculation of an X-ray tube-to-subject distance by an optical imaging control unit of the X-ray imaging apparatus according to the first embodiment. FIG. 7 is a schematic diagram (2) for explaining calculation of an X-ray tube-to-subject distance by an optical imaging control unit of the X-ray imaging apparatus according to the first embodiment. FIG. 8 is a block diagram showing the overall configuration of an X-ray imaging apparatus according to a second embodiment. FIG. 9 is a schematic diagram (1) for explaining calculation of an X-ray tube-to-subject distance by an optical imaging control unit of the X-ray imaging apparatus according to the second embodiment. FIG. 10 is a schematic diagram (2) for explaining calculation of an X-ray tube-to-subject distance by an optical imaging control unit of the X-ray imaging apparatus according to the second embodiment.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] First Embodiment The configuration of an X-ray imaging apparatus 100 according to a first embodiment of the present invention will be described with reference to FIGS.

[0012] (Overall Configuration of X-Ray Imaging Apparatus) As shown in Fig. 1, the X-ray imaging apparatus 100 includes an X-ray irradiator 10, an X-ray detector 20, an optical imaging unit 31, a holder 40, a moving mechanism 50, an apparatus controller 60, and an input unit 61. The X-ray imaging apparatus 100 is an imaging apparatus including a medical X-ray imaging device, and is configured to perform X-ray imaging of a subject 101 to be imaged. In the X-ray imaging apparatus 100, X-rays irradiated from the X-ray irradiator 10 are detected by the X-ray detector 20, thereby performing X-ray imaging of the subject 101. In the X-ray imaging apparatus 100, an optical image 70 (see Fig. 4) capturing the appearance of the subject 101 is also captured by the optical imaging unit 31. In addition, in the X-ray imaging device 100, the X-ray irradiation unit 10, the X-ray detection unit 20, the optical imaging unit 31, the holding unit 40, and the moving mechanism 50 are installed in the imaging room 110, and the device control unit 60 and the input unit 61 are installed outside the imaging room 110.

[0013] The X-ray imaging device 100 is a ceiling-suspended type imaging device. In the X-ray imaging device 100, a holding unit 40 that holds the X-ray irradiation unit 10 is suspended from the ceiling by a moving mechanism 50 that is arranged on the ceiling of an imaging room 110. The holding unit 40 is held by the moving mechanism 50 so as to be movable within the imaging room 110.

[0014] 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. A moving mechanism 50 can move the holding unit 40 at least between an imaging position in a supine position using the imaging table 21 (position indicated by a solid line in FIG. 1 ) and an imaging position in an upright position using the imaging stand 22 (position indicated by a two-dot chain line in FIG. 1 ).

[0015] The X-ray detection unit 20 is provided with an AEC (Auto Exposure Control) 23. The AEC is a device that detects X-rays that have passed through the subject 101 and controls the tube voltage, tube current, irradiation time, etc. of the X-ray tube 11 (see FIG. 2 ) included in the X-ray irradiation unit 10 according to the detected X-ray dose.

[0016] In X-ray imaging in a lying position, the holding unit 40 is arranged at a position vertically facing the X-ray detection unit 20 of the imaging table 21, and X-ray imaging of the subject 101 lying on the imaging table 21 is performed between the X-ray irradiation unit 10 and the X-ray detection unit 20 that are vertically facing each other, and an image (optical imaging) of the subject 101 lying on the imaging table 21 is taken by the optical imaging unit 31. In X-ray imaging in a standing position, the holding unit 40 is arranged at a position horizontally facing the X-ray detection unit 20 of the imaging stand 22, and X-ray imaging of the subject 101 standing in front of the imaging stand 22 is performed between the X-ray irradiation unit 10 and the X-ray detection unit 20 that are horizontally facing each other, and an image of the subject 101 standing in front of the imaging stand 22 is taken by the optical imaging unit 31.

[0017] The moving mechanism 50 is configured to hold the holding unit 40 so that it can move in the horizontal and vertical directions. The moving mechanism 50 includes a ceiling suspension unit 51 and a support unit 52. The moving mechanism 50 is supported by rails 53 provided on the ceiling of the radiography room 110. The ceiling suspension unit 51 is configured to be movable in the horizontal direction by the rails 53. The ceiling suspension unit 51 is configured to support the support unit 52. The support unit 52 is configured to support the holding unit 40. The support unit 52 is configured to be extendable and retractable in the vertical direction. The holding unit 40 is configured to be movable in the vertical direction by the support unit 52. The moving mechanism 50 also moves the X-ray detection units 20 arranged on the radiography table 21 and the radiography stand 22.

[0018] As shown in FIG. 2 , the X-ray irradiation unit 10 includes an X-ray tube 11 and a collimator unit 12. The X-ray irradiation unit 10 is configured to irradiate a subject 101 (see FIG. 1 ) 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 collimator unit 12 has a plurality of shielding plates (collimator leaves) whose positions can be adjusted. The collimator unit 12 is configured to 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 unit 12 is provided near the X-ray tube 11 in the X-ray irradiation direction of the X-ray tube 11.

[0019] The holding unit 40 includes a display operation unit 41 and a grip unit 42. The holding unit 40 is configured to be movable in the horizontal and vertical directions via a movement mechanism 50 (see FIG. 1) either manually or under the control of a device control unit 60 (see FIG. 1). The optical imaging unit 31 is provided in the holding unit 40 together with the X-ray irradiation unit 10. Specifically, the holding unit 40 is provided with an imaging unit 30 composed of the optical imaging unit 31 and an optical imaging control unit 32. An irradiation field lamp 33 and an input receiving unit 43 are also provided in the holding unit 40. The optical imaging control unit 32, the display operation unit 41, and the irradiation field lamp 33 are examples of the "control unit," "display unit," and "light source unit" in the claims, respectively.

[0020] The display operation unit 41 includes, for example, a touch panel type liquid crystal display. The display operation unit 41 is configured to function as an image display unit that displays the optical image 70 (see FIG. 4) captured by the optical imaging unit 31, and also as an operation unit into which various operations are input by an operator (a medical professional such as a radiologist or a doctor). The display operation unit 41 outputs a signal indicating the received input operation to the optical imaging control unit 32 and the device control unit 60 (see FIG. 1).

[0021] The grip portion 42 is provided for an operator to hold when manually moving the holding portion 40. The grip portion 42 transmits the operating force of the operator to the holding portion 40.

[0022] The optical imaging unit 31 is provided on the outer surface of the collimator unit 12. When the patient is in a lying position, the optical imaging unit 31 is provided on the outer surface of the collimator unit 12 on a longitudinal side of the imaging table 21 (see FIG. 1). When the patient is in an upright position, the optical imaging unit 31 is provided on the outer surface of the collimator unit 12 on a side that intersects with the detection plane of the X-ray detection unit 20 (see FIG. 1). The optical imaging unit 31 faces the direction of X-ray irradiation from the X-ray tube 11. When the X-ray irradiator 10 faces the subject 101 (see FIG. 1) and the X-ray detection unit 20, the optical imaging unit 31 can capture an optical image 70 (see FIG. 4) of the subject 101 and the X-ray detection unit 20 from the X-ray irradiator 10 side. An imaging range 31a (see FIG. 6) of the optical imaging unit 31 is set to include the range of the irradiation field irradiated with X-rays and to be larger than the range of the X-ray irradiation field.

[0023] The collimator unit 12 is provided with an irradiation field lamp 33 and an input receiving unit 43. The irradiation field lamp 33 is provided inside the collimator unit 12. The irradiation field lamp 33 is configured to irradiate visible light onto an irradiation field region 33a (see FIG. 6 ) that indicates the region irradiated with X-rays by the X-ray irradiation unit 10. Specifically, like the X-rays irradiated from the X-ray irradiation unit 10, a portion of the visible light irradiated from the irradiation field lamp 33 is blocked by multiple shielding plates (collimator leaves) of the collimator unit 12, thereby adjusting the irradiation field. Therefore, the irradiation field of the visible light irradiated from the irradiation field lamp 33 is adjusted by the multiple shielding plates (collimator leaves) of the collimator unit 12 to be equal to the irradiation field of the X-rays irradiated from the X-ray irradiation unit 10. Note that the optical axis 33b (see FIG. 6 ) of the irradiation field lamp 33 coincides with the optical axis of the X-rays irradiated from the X-ray irradiation unit 10. The irradiation field lamp 33 includes a light emitting element such as an LED (Light Emitting Diode).

[0024] The input accepting unit 43 is configured to accept input from the operator. The input accepting unit 43 is, for example, a push button for operating the irradiation field lamp 33. That is, the input accepting unit 43 is configured to accept an operation input for turning on the irradiation field lamp 33. When the input accepting unit 43 is operated (pressed) by the operator, visible light is irradiated from the irradiation field lamp 33.

[0025] 3, the optical imaging unit 31 includes a monocular camera 31b (2D camera). On the other hand, the optical imaging unit 31 does not include a 3D camera. The monocular camera 31b includes an imaging element such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor.

[0026] The optical imaging control unit 32 is, for example, a microcomputer including a CPU (Central Processing Unit), a memory, etc. The optical imaging control unit 32 transmits and receives signals to and from the device control unit 60 via a wireless or wired connection.

[0027] As shown in FIG. 4 , the optical imaging unit 31 (see FIG. 3 ) is configured to capture an optical image 70 of the subject 101. The optical imaging control unit 32 (see FIG. 3 ) is configured to receive a signal output from the optical imaging unit 31 and generate the optical image 70 based on the received signal. The optical imaging control unit 32 is also configured to control the display operation unit 41 (see FIG. 3 ) to output and display the generated optical image 70. FIG. 4 shows the optical image 70 in a state where visible light emitted from the irradiation field lamp 33 (see FIG. 3 ) is irradiated onto the irradiation field region 33 a (see FIG. 6 ). Therefore, the optical image 70 shown in FIG. 4 includes the subject 101, the X-ray detection unit 20, and the irradiation field region 33 a. Note that if visible light is not irradiated from the irradiation field lamp 33, the irradiation field region 33 a is not captured in the optical image 70.

[0028] As shown in FIG. 3 , the device control unit 60 includes a CPU and a memory 60a. The device control unit 60 controls X-ray imaging by the X-ray irradiator 10 and the X-ray detector 20, and controls the movement of the holder 40. The input unit 61 has a function of accepting input operations related to X-ray imaging. The input operations include setting imaging conditions for X-ray imaging and issuing an instruction to start X-ray irradiation. The device control unit 60 controls X-ray imaging based on parameters and various programs that are set in advance and stored in the memory 60a. The device control unit 60 controls the amount of adjustment of the irradiation field by the collimator unit 12 (see FIG. 2 ).

[0029] The movement mechanism 50 includes a drive unit 50a such as a motor and a motion detector 50b that detects the operation of the drive unit 50a. The motion detector 50b includes, for example, a potentiometer that detects the rotation of the motor. The drive unit 50a and the motion detector 50b are disposed in various parts of the movement mechanism 50 that move the holder 40, and are also disposed on the radiography table 21 (see FIG. 1) and the radiography stand 22 (see FIG. 1) to change the position of the X-ray detection unit 20. The device controller 60 controls the operation of the movement mechanism 50 based on an input operation on the input unit 61 (see FIG. 1) or the display / operation unit 41, or an operating force on the grip 42 (see FIG. 2) of the holder 40, thereby changing the position and angle of the X-ray irradiation unit 10 and the position of the X-ray detection unit 20. In addition, the device control unit 60 outputs a control signal to control the operation of the drive unit 50a, and controls the operation of the moving mechanism 50 by feedback control by inputting a detection signal indicating the operation of the drive unit 50a detected by the operation detection unit 50b.

[0030] The device control unit 60 outputs the position and angle of the X-ray irradiator 10 held by the holder 40 and the positions of the X-ray detectors 20 arranged on the radiography table 21 (see FIG. 1) and the radiography stand 22 (see FIG. 1) to the optical imaging control unit 32. The optical imaging control unit 32 acquires the arrangement of the X-ray irradiator 10 and the arrangement of the X-ray detectors 20 based on the input from the device control unit 60. The optical imaging control unit 32 also acquires the amount of adjustment of the irradiation field by the collimator unit 12 based on the input from the device control unit 60.

[0031] (Display Control by Optical Imaging Controller) As shown in FIG. 5 , the optical imaging controller 32 (see FIG. 3 ) is configured to superimpose a detection unit region display 81, an irradiation field region display 84, and an AEC region display 87 on the optical image 70 and display them on the display operation unit 41. The optical imaging controller 32 displays the detection unit region display 81 on the display operation unit 41 based on the calculated X-ray tube-to-subject distance D1 (see FIG. 6 ). Details of the calculation of the X-ray tube-to-subject distance D1 will be described later. Note that the following description will discuss control of the display on the display operation unit 41 by the optical imaging controller 32 when X-ray imaging is performed with the subject 101 in an upright position (standing position). The above control is also similar when X-ray imaging is performed with the subject 101 lying on the imaging table 21 (see FIG. 1 ), and therefore will not be described again.

[0032] The detection unit region display 81 indicates the region in the optical image 70 where the X-ray detection unit 20 (see FIG. 3) is located. The optical imaging control unit 32 (see FIG. 3) acquires the three-dimensional layout of the X-ray irradiator 10 (see FIG. 3) and the X-ray detection unit 20, as well as the three-dimensional layout of the optical imaging unit 31 (see FIG. 3). Because the optical imaging unit 31 is disposed in the holder 40 (see FIG. 3) together with the X-ray irradiator 10, the optical imaging control unit 32 calculates the three-dimensional position of the optical imaging unit 31 using pre-stored parameters based on the acquired position of the X-ray irradiator 10. The optical imaging control unit 32 then detects the region in the optical image 70 where the X-ray detection unit 20 is located by performing geometric calculations based on the acquired three-dimensional positional relationship between the X-ray irradiator 10, the X-ray detection unit 20, and the optical imaging unit 31. The optical imaging control unit 32 may also acquire the position of the optical imaging unit 31 calculated by the device control unit 60 (see FIG. 3).

[0033] The optical imaging control unit 32 (see FIG. 3 ) generates a detection unit area display 81 based on the area where the detected X-ray detection unit 20 (see FIG. 3 ) is located. The detection unit area display 81 shows the area where the X-ray detection unit 20 is located in a rectangular shape. The detection unit area display 81 shows, for example, a rectangular area. The detection unit area display 81 has a center display 82 indicating the center of the area where the X-ray detection unit 20 is located and four L-shaped area displays 83 indicating the four corners of the rectangular area. The center display 82 has a cross shape and is located at the position where the diagonal lines of the rectangular area intersect. The center display 82 and the four area displays 83 are displayed, for example, in blue. The detection unit area display 81 also provides a guide to the position and range of the area in the optical image 70 where X-rays can be detected by the X-ray detection unit 20. Note that the area shown by the detection unit area display 81 may be smaller or larger than the actual area where X-rays can be detected by the X-ray detection unit 20.

[0034] The optical imaging control unit 32 (see FIG. 3) is also configured to control the display operation unit 41 to display an irradiation field area display 84 indicating the irradiation field area 33a (see FIG. 6) together with the detection unit area display 81 superimposed on the optical image 70. As with the detection unit area display 81, the optical imaging control unit 32 detects the irradiation field area 33a in the optical image 70 to which X-rays are irradiated by the X-ray irradiation unit 10 by performing geometric calculations based on the acquired three-dimensional positional relationships among the X-ray irradiation unit 10 (see FIG. 3), the X-ray detection unit 20 (see FIG. 3), and the optical imaging unit 31 (see FIG. 3). The optical imaging control unit 32 then generates the irradiation field area display 84 based on the detected irradiation field area 33a to which X-rays are irradiated.

[0035] The irradiation field area display 84 shows the area irradiated with X-rays in a rectangular shape. The irradiation field area display 84 shows, for example, a square area. The irradiation field area display 84 has an area display 85, which is a rectangular frame line showing the irradiation field area 33a (see FIG. 6 ) irradiated with X-rays, and a pair of dotted lines 86, which are perpendicular to each other and indicate the center of the irradiation field area 33a irradiated with X-rays. The pair of dotted lines 86 are arranged perpendicular to each other and pass through the center position where the diagonal lines of the rectangle of the area display 85 intersect. The pair of dotted lines 86 are also arranged to extend outside the rectangular frame line of the area display 85. The area display 85 and the pair of dotted lines 86 are displayed in a color (e.g., yellow) different from that of the detection unit area display 81. The irradiation field area display 84 also provides a guide to the position and range of the area irradiated with X-rays in the optical image 70. The area indicated by the radiation field area display 84 may be smaller or larger than the area actually irradiated with X-rays.

[0036] The optical imaging control unit 32 (see FIG. 3) is configured to change the size of an irradiation field region display 84 superimposed on the optical image 70 on the display operation unit 41 (see FIG. 3) in accordance with the X-ray irradiation field defined by adjustment of the multiple shielding plates of the collimator unit 12 (see FIG. 2). The optical imaging control unit 32 changes the size of a region display 85, which is a rectangular frame line, in the irradiation field region display 84 superimposed on the optical image 70, based on the value of the adjustment amount of the multiple shielding plates of the collimator unit 12 acquired from the device control unit 60 (see FIG. 3). Note that even if the size of the region display 85 indicated by the rectangular frame line in the irradiation field region display 84 is changed, the size of the dotted line display 86 is not changed.

[0037] The AEC region display 87 shows the position and shape of the AEC 23 (see FIG. 1) provided in the X-ray detection unit 20 (see FIG. 3). The position and shape of the AEC 23 provided in the X-ray detection unit 20 are known. Furthermore, as described above, the optical imaging control unit 32 (see FIG. 3) detects the region in the optical image 70 where the X-ray detection unit 20 is located when generating the detection unit region display 81. Therefore, the optical imaging control unit 32 generates the AEC region display 87 based on the detected location of the X-ray detection unit 20 and the position and shape of the AEC 23 in the X-ray detection unit 20. The AEC is provided in the X-ray detection unit 20. Therefore, the AEC region display 87 is displayed in the same color (e.g., blue) as the detection unit region display 81. In the example shown in FIG. 5, two AEC region displays 87 are superimposed on the optical image 70.

[0038] (Calculation of X-ray Tube-Subject Distance) When X-rays are irradiated onto the subject 101 using the X-ray imaging device 100 (see FIG. 1 ), an operator (a medical professional such as a radiologist or a doctor) needs to determine appropriate X-ray conditions (such as the amount of X-rays to be irradiated onto the subject 101) for the subject 101. Therefore, in order for the operator to determine appropriate X-ray conditions for the subject 101, as shown in FIGS. 6 and 7 , the optical imaging control unit 32 (see FIG. 3 ) calculates the X-ray tube-subject distance D1 between (the focal point of) the X-ray tube 11 and the subject 101 based on the coordinates of the center of a predetermined position 33 c of an irradiation field region 33 a shown on the body surface of the subject 101 in an optical image 70 captured by the monocular camera 31 b (see FIG. 3 ) of the optical imaging unit 31.

[0039] Specifically, the optical imaging control unit 32 (see FIG. 3) calculates a detector-body-surface distance D3 between the X-ray detection unit 20 and the body surface of the subject 101 in the optical axis direction of the irradiation field lamp 33 (see FIG. 3) based on a coordinate difference D2 between the coordinate of the center of the predetermined position 20a of the X-ray detection unit 20 in the optical image 70 and the coordinate of the center of the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70. Then, the optical imaging control unit 32 calculates an X-ray tube-subject distance D1 based on the calculated detector-body-surface distance D3 and an X-ray tube-detector distance D4 between the X-ray tube 11 and the X-ray detection unit 20.

[0040] Specifically, as shown in Fig. 6, the optical axis 31c of the optical imaging unit 31 is parallel to the optical axis 33b of the irradiation field lamp 33. In other words, the optical imaging unit 31 has an optical axis that is shifted in the direction in which the optical imaging unit 31 and the X-ray irradiation unit 10 are aligned with respect to the irradiation axis of X-rays irradiated from the X-ray irradiation unit 10 (the optical axis 33b of the irradiation field lamp 33). Therefore, as shown in Fig. 7, in the optical image 70, the center of the X-ray detection unit 20 as the predetermined position 20a is shifted from the center of the irradiation field region 33a as the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101. Therefore, the optical imaging control unit 32 (see Fig. 3) first calculates a coordinate difference D2 between the coordinate of the center of the X-ray detection unit 20 as the predetermined position 20a in the optical image 70 and the coordinate of the center of the irradiation field region 33a as the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70.

[0041] Next, as shown in FIG. 6 , the optical imaging control unit 32 (see FIG. 3 ) calculates the detector-body-surface distance D3 between the X-ray tube 11 and the X-ray detection unit 20 from the equation tan θ = (coordinate difference D2 / detector-body-surface distance D3), where θ is the angle between the optical axis 33b of the irradiation field lamp 33 and the line connecting the optical imaging unit 31 and the center 20b of the X-ray detection unit 20. That is, the optical imaging control unit 32 calculates the detector-body-surface distance D3 in the optical axis direction of the X-ray tube 11 based on the coordinate difference D2 as well as the angle θ between the optical axis 33b of the irradiation field lamp 33 and the line connecting the optical imaging unit 31 and the center 20b of the X-ray detection unit 20. Next, the optical imaging control unit 32 calculates the X-ray tube-subject distance D1 by subtracting the detector-body-surface distance D3 from the X-ray tube-detector distance D4.

[0042] As shown in FIG. 5 , the optical imaging control unit 32 (see FIG. 3 ) causes the display operation unit 41 to display the calculated X-ray tube-subject distance D1 (see FIG. 6 ). Specifically, the optical imaging control unit 32 causes the display operation unit 41 to display a display area 91 displaying the X-ray tube-subject distance D1. In addition to the X-ray tube-subject distance D1, the optical imaging control unit 32 also causes the display operation unit 41 to display the SID (Source to Image Receptor Distance), which is the distance between the X-ray tube 11 (see FIG. 2 ) (the focal point) and the X-ray detection unit 20 (see FIG. 1 ), an irradiation unit angle, which displays the angle of the X-ray irradiation unit 10 (see FIG. 1 ) with respect to the radiography table 21 (see FIG. 1 ) or the radiography stand 22 (see FIG. 1 ), and the like. Specifically, the optical imaging control unit 32 causes the display operation unit 41 to display a display area 90 displaying the SID, a display area 92 displaying the irradiation unit angle, and the like. In FIG. 5, the X-ray tube-to-subject distance D1 is indicated as SOD.

[0043] (Effects of First Embodiment) In the first embodiment, the following effects can be obtained.

[0044] In the first embodiment, as described above, the X-ray imaging apparatus 100 includes an optical imaging control unit 32 (control unit) that calculates the X-ray tube-subject distance D1 between the X-ray tube 11 and the subject 101 based on the coordinates of the predetermined position 33c in the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70 captured by the optical imaging unit 31. This makes it possible to geometrically calculate the X-ray tube-subject distance D1 based on the coordinates of the predetermined position 33c in the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70. In this case, the optical image 70 may be an image captured by the monocular camera 31b. As a result, the X-ray tube-subject distance D1 can be calculated without using a 3D camera.

[0045] Furthermore, in the first embodiment, the following additional effects can be obtained by configuring as follows.

[0046] That is, in the first embodiment, as described above, the optical imaging unit 31 includes the monocular camera 31b. The optical imaging control unit 32 (control unit) calculates the X-ray tube-subject distance D1 based on the coordinates of a predetermined position 33c in the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70 captured by the monocular camera 31b. With this configuration, it is possible to reliably realize a configuration that allows the X-ray tube-subject distance D1 to be calculated without using a 3D camera.

[0047] Furthermore, in the first embodiment, as described above, the optical imaging control unit 32 (control unit) calculates a detector-to-body-surface distance D3 between the X-ray detection unit 20 and the body surface of the subject 101 in the optical axis direction of the X-ray tube 11, based on a coordinate difference D2 between the coordinate of the predetermined position 20a of the X-ray detection unit 20 in the optical image 70 and the coordinate of the predetermined position 33c in the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70. Then, the optical imaging control unit 32 calculates an X-ray tube-to-subject distance D1 based on the calculated detector-to-body-surface distance D3 and an X-ray tube-to-detector distance D4 between the X-ray tube 11 and the X-ray detection unit 20. With this configuration, the detector-to-body-surface distance D3 can be geometrically calculated based on the coordinate difference D2 and the coordinates of the predetermined position 20a of the X-ray detection unit 20 in the optical image 70, which is information that can be recognized by the optical imaging control unit 32, such as the relative positional relationship of each part of the X-ray imaging device 100, and the X-ray tube-to-subject distance D1 can be calculated by subtracting the detector-to-body-surface distance D3 from the X-ray tube-to-detection unit distance D4.

[0048] Furthermore, in the first embodiment, as described above, the optical imaging control unit 32 (control unit) calculates the detector-body-surface distance D3 in the direction of the optical axis of the irradiation field lamp 33 (light source unit) based on not only the coordinate difference D2 but also the angle θ formed between the optical axis of the irradiation field lamp 33 and the line connecting the optical imaging unit 31 and the center 20b of the X-ray detection unit 20. With this configuration, the detector-body-surface distance D3 can be easily calculated geometrically from the coordinate difference D2 and the angle θ using the geometric relationship tan θ = (coordinate difference D2 / detector-body-surface distance D3).

[0049] Furthermore, in the first embodiment, as described above, the optical imaging control unit 32 (control unit) calculates the X-ray tube-subject distance D1 based on the coordinates of the center of the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70. With this configuration, the coordinates of the center of the predetermined position 33c of the irradiation field region 33a in the optical image 70 can be easily determined using a mark indicating the center of the irradiation field region 33a, which is generally displayed at the center of the irradiation field region 33a in the optical image 70. As a result, the X-ray tube-subject distance D1 can be easily calculated compared to when coordinates other than the center are used as the coordinates of the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70.

[0050] Furthermore, in the first embodiment, as described above, the optical axis of the optical imaging unit 31 is parallel to the optical axis of the irradiation field lamp 33 (light source unit). With this configuration, when calculating the X-ray tube-to-subject distance D1, it is not necessary to take into consideration that the optical axis of the optical imaging unit 31 is tilted with respect to the optical axis of the irradiation field lamp 33. Therefore, compared to a case where the optical axis of the optical imaging unit 31 is not parallel to the optical axis of the irradiation field lamp 33, the X-ray tube-to-subject distance D1 can be calculated more easily.

[0051] Furthermore, in this embodiment, as described above, the X-ray imaging apparatus 100 includes the display operation unit 41 (display unit). The optical imaging control unit 32 (control unit) then displays the calculated X-ray tube-to-subject distance D1 on the display operation unit 41. With this configuration, the operator can easily visually recognize the X-ray tube-to-subject distance D1 displayed on the display operation unit 41. As a result, the operator can easily determine appropriate X-ray conditions for the subject.

[0052] Furthermore, in this embodiment, as described above, the optical imaging control unit 32 (control unit) causes the display operation unit 41 (display unit) to display the detection unit area display 81 indicating the area in which the X-ray detection unit 20 is located in the optical image 70, based on the calculated X-ray tube-to-subject distance D1. With this configuration, the operator can easily visually recognize the detection unit area display 81 displayed on the display operation unit 41. As a result, the operator can easily grasp the position where the X-ray detection unit 20 is located.

[0053] Second Embodiment The configuration of an X-ray imaging apparatus 200 according to a second embodiment of the present invention will be described with reference to Figures 8 to 10. In the figures, the same components as those in the first embodiment are denoted by the same reference numerals.

[0054] (Overall Configuration of X-ray Imaging Apparatus) As shown in Fig. 8, the X-ray imaging apparatus 200 includes a holding section 40. The holding section 40 has an imaging unit 230 configured by an optical imaging section 31 and an optical imaging control section 232. The optical imaging control section 232 is an example of the "control section" in the claims.

[0055] (Calculation of X-ray tube-subject distance) As shown in Figures 9 and 10 , similarly to the first embodiment, the optical imaging control unit 232 (see Figure 8 ) calculates the X-ray tube-subject distance D1 between the X-ray tube 11 and the subject 101 based on the coordinates of the center as a predetermined position 33c of the irradiation field area 33a shown on the body surface of the subject 101 in the optical image 70 captured by the monocular camera 31b (see Figure 8 ) of the optical imaging unit 31 (see Figure 8 ).

[0056] Specifically, the optical imaging control unit 232 (see FIG. 8 ) calculates an imaging unit-body-surface distance D5 between the optical imaging unit 31 and the body surface of the subject 101 in the optical axis direction of the irradiation field lamp 33 (see FIG. 8 ) based on the coordinates of the center as a predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70, the coordinates of an imaging unit coordinate system centered on the optical imaging unit 31, and a relational expression (relational expression using a matrix of internal parameters of the optical imaging unit 31) for converting the coordinates of the imaging unit coordinate system into coordinates of an image coordinate system indicating the coordinates in the optical image 70. Then, the optical imaging control unit 232 calculates an X-ray tube-subject distance D1 based on the calculated imaging unit-body-surface distance D5 and an X-ray tube-imaging unit distance D6 between the X-ray tube 11 and the optical imaging unit 31 in the optical axis direction of the irradiation field lamp 33.

[0057] Specifically, the irradiation axis direction of the X-ray irradiator 10 is the Z direction, and the directions orthogonal to each other in a plane orthogonal to the Z direction are the X and Y directions, respectively. The coordinates of the center of the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70 in the imaging unit coordinate system (Xc, Yc, Zc) with the optical imaging unit 31 as the center (origin) in real space, and the coordinates of the image coordinate system (x, y) showing the coordinates in the optical image 70 are respectively (Xc ｈ , Yc ｈ , Zc ｈ ) and (x ｈ , y ｈ ), the following equation (1) holds: Here, K is a matrix for converting coordinates in the imaging unit coordinate system into coordinates in the image coordinate system, and is what is called a matrix of internal parameters of the optical imaging unit 31. That is, f is the focal length of the lens of the monocular camera 31b of the optical imaging unit 31, (Sx, Sy) is the size of the imaging element of the monocular camera 31b of the optical imaging unit 31, and (w, h) is the number of pixels of the imaging element of the monocular camera 31b of the optical imaging unit 31.

[0058] From the above formula (1), the following formulas (2) and (3) are derived.

[0059] The following equations (4) and (5) are derived from the above equations (2) and (3), respectively.

[0060] As a result, from the above formula (4) or formula (5), Zc ｈ Zc can be calculated. ｈ is the Z-direction component of the coordinates of the center of the predetermined position 33c of the irradiation field region 33a on the body surface of the subject 101 in the optical image 70, in the image capturing unit coordinate system with the optical image capturing unit 31 as the center (origin). ｈ is equal to the distance D5 between the imaging unit and the body surface.

[0061] Then, the optical imaging control unit 232 (see Figure 8) calculates the X-ray tube-to-subject distance D1 by adding the imaging unit-to-body surface distance D5 and the X-ray tube-to-imaging unit distance D6 between the X-ray tube 11 and the optical imaging unit 31 in the optical axis direction of the irradiation field lamp 33 (see Figure 8).

[0062] The other configurations of the second embodiment are the same as those of the first embodiment.

[0063] (Effects of Second Embodiment) In the second embodiment, the following effects can be obtained.

[0064] In the second embodiment, as described above, the X-ray imaging apparatus 200 includes an optical imaging control unit 232 (control unit) that calculates the X-ray tube-subject distance D1 between the X-ray tube 11 and the subject 101 based on the coordinates of the predetermined position 33c in the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70 captured by the optical imaging unit 31. This allows the X-ray tube-subject distance D1 to be geometrically calculated based on the coordinates of the predetermined position 33c in the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70. In this case, as in the first embodiment, the optical image 70 may be an image captured by the monocular camera 31b. As a result, as in the first embodiment, the X-ray tube-subject distance D1 can be calculated without using a 3D camera.

[0065] Furthermore, in the second embodiment, the following additional effects can be obtained by the following configuration.

[0066] That is, in the second embodiment, as described above, the optical imaging control unit 32 (control unit) calculates an imaging unit-body-surface distance D5 between the optical imaging unit 31 and the body surface of the subject 101 in the optical axis direction of the irradiation field lamp 33 (light source unit) based on the coordinates of a predetermined position 33c in the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70, the coordinates of an imaging unit coordinate system centered on the optical imaging unit 31, and a relational expression for converting the coordinates of the imaging unit coordinate system into coordinates of an image coordinate system that indicates the coordinates in the optical image 70. Then, the optical imaging control unit 32 calculates an X-ray tube-subject distance D1 based on the calculated imaging unit-body-surface distance D5 and an X-ray tube-imaging unit distance D6 between the X-ray tube 11 and the optical imaging unit 31 in the optical axis direction of the irradiation field lamp 33. With this configuration, the distance D5 between the imaging unit and the body surface can be geometrically calculated based on the coordinates of a predetermined position 33c in the irradiation field area 33a that is shown on the body surface of the subject 101 in the optical image 70, the coordinates of the imaging unit coordinate system, and a relational expression for converting the coordinates of the imaging unit coordinate system into coordinates of the image coordinate system, and the distance D5 between the imaging unit and the body surface and the distance D6 between the X-ray tube and the imaging unit can be added together to calculate the distance D1 between the X-ray tube and the subject.

[0067] Furthermore, in the second embodiment, as described above, the optical imaging control unit 32 (control unit) calculates the imaging unit-body-surface distance D5 in the optical axis direction of the irradiation field lamp 33 (light source unit) based on the coordinates of the predetermined position 33c of the irradiation field region 33a that appears on the body surface of the subject 101 in the optical image 70, the coordinates of the imaging unit coordinate system, and a relational expression using the matrix of internal parameters of the optical imaging unit 31. With this configuration, the coordinates of the imaging unit coordinate system and the coordinates of the image coordinate system can be easily converted by the relational expression for converting the coordinates of the imaging unit coordinate system into coordinates of the image coordinate system, using the matrix of internal parameters of the optical imaging unit 31, and therefore the imaging unit-body-surface distance D5 in the optical axis direction of the irradiation field lamp 33 can be easily calculated.

[0068] The other effects of the second embodiment are the same as those of the first embodiment.

[0069] [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.

[0070] For example, in the above first and second embodiments, an example has been shown in which the optical imaging control unit 32 (232) (control unit) causes the display operation unit 41 (display unit) to display the detection unit area display 81 indicating the area in the optical image 70 where the X-ray detection unit 20 is located based on the calculated X-ray tube-to-subject distance D1, but the present invention is not limited to this. In the present invention, the control unit does not need to cause the display unit to display the detection unit area display indicating the area in the optical image where the X-ray detection unit is located based on the calculated X-ray tube-to-subject distance.

[0071] In the first and second embodiments, the optical imaging control unit 32 (232) (control unit) displays the calculated X-ray tube-subject distance D1 on the display operation unit 41. However, the present invention is not limited to this. In the present invention, the control unit does not need to display the calculated X-ray tube-subject distance on the display unit.

[0072] Furthermore, in the first and second embodiments, the optical axis of the optical imaging unit 31 is parallel to the optical axis of the irradiation field lamp 33 (light source unit), but the present invention is not limited to this. In the present invention, the optical axis of the optical imaging unit does not have to be parallel to the optical axis of the light source unit. In this case, when calculating the X-ray tube-subject distance, it is necessary to take into account that the optical axis of the optical imaging unit is tilted relative to the optical axis of the irradiation field lamp. For example, in the first embodiment, when calculating the coordinate of a predetermined position of the X-ray detection unit in the optical image, it is taken into account that the optical axis of the optical imaging unit is tilted relative to the optical axis of the irradiation field lamp. Furthermore, in the second embodiment, the coordinates of the imaging unit coordinate system used in the above equation (1) take into account that the optical axis of the optical imaging unit is tilted relative to the optical axis of the irradiation field lamp.

[0073] In the first and second embodiments, the optical imaging control unit 32 (232) (control unit) calculates the X-ray tube-subject distance D1 based on the coordinates of the center of the predetermined position 33c of the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70. However, the present invention is not limited to this. In the present invention, the control unit may use coordinates other than the center as the coordinates of the predetermined position of the irradiation field region shown on the body surface of the subject in the optical image. In this case, any coordinates of the irradiation field region shown on the body surface of the subject in the optical image may be used as long as the position can be recognized.

[0074] Furthermore, in the above-described first embodiment, an example was shown in which the optical imaging control unit 232 (control unit) calculates the imaging unit-body-surface distance D5 in the optical axis direction of the irradiation field lamp 33 (light source unit) based on the coordinates of a predetermined position 33c in the irradiation field region 33a shown on the body surface of the subject 101 in the optical image 70, the coordinates of the imaging unit coordinate system, and a relational expression using a matrix of internal parameters of the optical imaging unit 31. However, the present invention is not limited to this. In the present invention, the control unit may calculate the imaging unit-body-surface distance D5 in the optical axis direction of the light source unit based on the coordinates of a predetermined position in the irradiation field region shown on the body surface of the subject in the optical image, the coordinates of the imaging unit coordinate system, and a relational expression for converting the coordinates of the imaging unit coordinate system to the coordinates of the optical image coordinate system other than the relational expression using the matrix of internal parameters of the optical imaging unit.

[0075] Furthermore, in the first embodiment described above, an example was shown in which the optical imaging control unit 32 (control unit) calculates the detection unit-body-surface distance D3 in the optical axis direction of the irradiation field lamp 33 based on the coordinate difference D2 as well as the angle θ formed between the optical axis of the irradiation field lamp 33 (light source unit) and the line connecting the optical imaging unit 31 and the center 20b of the X-ray detection unit 20, but the present invention is not limited to this. In the present invention, the control unit may calculate the detection unit-body-surface distance in the optical axis direction of the light source unit based on information recognizable by the optical imaging control unit, such as the relative positional relationship between each part of the X-ray imaging device, other than the angle formed between the optical axis of the light source unit and the line connecting the optical imaging unit and the center of the X-ray detection unit, in addition to the coordinate difference.

[0076] In the first embodiment, the optical imaging control unit 32 (control unit) calculates a detector-to-body-surface distance D3 between the X-ray detection unit 20 and the body surface of the subject 101 in the optical axis direction of the irradiation field lamp 33 (light source unit) based on a coordinate difference D2 between the coordinate of a predetermined position 20a of the X-ray detection unit 20 in the optical image 70 and the coordinate of a predetermined position 33c in the irradiation field region 33a on the body surface of the subject 101 in the optical image 70, and calculates an X-ray tube-to-subject distance D1 based on the calculated detector-to-body-surface distance D3 and an X-ray tube-to-detector distance D4 between the X-ray tube 11 and the X-ray detection unit 20. In the second embodiment, the optical imaging control unit 232 (control unit) calculates a detector-to-body-surface distance D3 between the X-ray detection unit 20 and the body surface of the subject 101 in the optical axis direction of the irradiation field lamp 33 based on a coordinate difference D2 between the coordinate of a predetermined position 20a of the X-ray detection unit 20 in the optical image 70 and the coordinate of a predetermined position 33c in the irradiation field region 33a on the body surface of the subject 101 in the optical image 70. In the above example, the optical imaging control unit 32 calculates the imaging unit-body-surface distance D5 between the optical imaging unit 31 and the body surface of the subject 101 in the optical axis direction of the irradiation field lamp 33 based on the coordinates of a predetermined position 33c in the irradiation field region 33a imaged on the body surface of the subject 101 in the image, the coordinates of an imaging unit coordinate system centered on the optical imaging unit 31, and a relational expression for converting the coordinates of the imaging unit coordinate system into coordinates of an image coordinate system indicating coordinates in the optical image 70, and the optical imaging control unit 32 calculates the X-ray tube-subject distance D1 based on the calculated imaging unit-body-surface distance D5 and the X-ray tube-imaging unit distance D6 between the X-ray tube 11 and the optical imaging unit 31 in the optical axis direction of the irradiation field lamp 33. However, the present invention is not limited to this. In the present invention, the control unit may be configured to calculate the X-ray tube-subject distance using the method of the first embodiment and to calculate the X-ray tube-subject distance using the method of the second embodiment.

[0077] In the first and second embodiments, the imaging unit 30, which is configured by the optical imaging unit 31 and the optical imaging control unit 32 (control unit), is disposed in the holding unit 40 that holds the X-ray irradiation unit 10. However, the present invention is not limited to this. In the present invention, the optical imaging unit and the control unit may be disposed at positions spaced apart from each other. The optical imaging unit may also be disposed at a position different from the holding unit, such as on the ceiling or wall of the imaging room. The control unit may also be disposed at a position different from the holding unit. The imaging unit may also be configured as a unit that is added to the X-ray imaging device.

[0078] In the first and second embodiments, the detection unit area display 81 includes a cross-shaped center display 82 and four area displays 83 indicating the four corners, and the irradiation field area display 84 includes a rectangular frame area display 85 and a pair of dotted line displays 86. However, the present invention is not limited to this. In the present invention, the detection unit area display and the irradiation field area display may be displayed in a manner different from that of the above embodiments. For example, either the detection unit area display or the irradiation field area display may not include an indication indicating the center of the area. Furthermore, the detection unit area display may indicate the extent of the area using a rectangular frame line. The irradiation field area display may not include a pair of dotted line displays, but may instead only show the rectangular frame line, or may only show the four corners. At least one of the detection unit area display and the irradiation field area display may be displayed transparently or flashing.

[0079] Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0080] (Item 1) An X-ray imaging device comprising: an X-ray irradiation unit including an X-ray tube; an X-ray detection unit that detects X-rays irradiated from the X-ray irradiation unit and transmitted through a subject; a light source unit that irradiates visible light onto an irradiation field area that indicates an area irradiated with X-rays by the X-ray irradiation unit; an optical imaging unit that has an optical axis shifted from the irradiation axis of the X-ray irradiated from the X-ray irradiation unit and captures an optical image of the subject; and a control unit that calculates an X-ray tube-to-subject distance between the X-ray tube and the subject based on coordinates of a predetermined position within the irradiation field area that appears on the body surface of the subject in the optical image captured by the optical imaging unit.

[0081] (Item 2) The X-ray imaging device according to Item 1, wherein the optical imaging unit includes a monocular camera, and the control unit calculates the X-ray tube-subject distance based on coordinates of a predetermined position in the irradiation field region that appears on the body surface of the subject in the optical image captured by the monocular camera.

[0082] (Item 3) The X-ray imaging device according to item 1 or 2, wherein the control unit calculates a detector-to-body-surface distance between the X-ray detection unit and the body surface of the subject in the optical axis direction of the light source unit based on a coordinate difference between a coordinate of a predetermined position of the X-ray detection unit in the optical image and a coordinate of a predetermined position in the irradiation field region on the body surface of the subject in the optical image, and calculates the X-ray tube-to-subject distance based on the calculated detector-to-body-surface distance and an X-ray tube-to-detector distance between the X-ray tube and the X-ray detection unit.

[0083] (Item 4) The X-ray imaging device according to Item 3, wherein the control unit calculates the distance between the detector and a body surface in the optical axis direction of the X-ray tube based on the coordinate difference as well as an angle formed between the optical axis of the light source unit and a line connecting the optical imaging unit and the center of the X-ray detection unit.

[0084] (Item 5) The X-ray imaging device according to item 1 or 2, wherein the control unit calculates an imaging unit-body-surface distance between the optical imaging unit and the body surface of the subject in the optical axis direction of the light source unit based on coordinates of a predetermined position in the irradiation field region that appears on the body surface of the subject in the optical image, coordinates in an imaging unit coordinate system centered on the optical imaging unit, and a relational expression for converting the coordinates in the imaging unit coordinate system into coordinates in an image coordinate system that indicates coordinates in the optical image, and calculates the X-ray tube-subject distance based on the calculated imaging unit-body-surface distance and an X-ray tube-imaging unit distance between the X-ray tube and the optical imaging unit in the optical axis direction of the light source unit.

[0085] (Item 6) The X-ray imaging device according to Item 5, wherein the control unit calculates a distance between the imaging unit and the body surface in the optical axis direction of the light source unit based on the coordinates of a predetermined position in the irradiation field region that is shown on the body surface of the subject in the optical image, the coordinates of the imaging unit coordinate system, and the relational expression that uses a matrix of internal parameters of the optical imaging unit.

[0086] (Item 7) The X-ray imaging device according to any one of Items 1 to 6, wherein the control unit calculates the X-ray tube-subject distance based on coordinates of a center as a predetermined position of the irradiation field region that is shown on the body surface of the subject in the optical image.

[0087] (Item 8) The X-ray imaging apparatus according to any one of Items 1 to 7, wherein the optical axis of the optical imaging unit is parallel to the optical axis of the light source unit.

[0088] (Item 9) The X-ray imaging apparatus according to any one of Items 1 to 8, further comprising a display unit, wherein the control unit causes the display unit to display the calculated X-ray tube-subject distance.

[0089] (Item 10) The X-ray imaging device according to any one of Items 1 to 9, wherein the control unit causes the display unit to display a detection unit area display indicating an area in which the X-ray detection unit is located in the optical image based on the calculated X-ray tube-subject distance.

[0090] REFERENCE SIGNS LIST 10 X-ray irradiation unit 11 X-ray tube 20 X-ray detection unit 20a Predetermined position (of X-ray detection unit in optical image) 20b Center of X-ray detection unit 31 Optical imaging unit 31b Monocular camera 31c Optical axis (of optical imaging unit) 32, 232 Optical imaging control unit (control unit) 33 Irradiation field lamp (light source unit) 33a Irradiation field area 33b Optical axis (of light source unit) 33c Predetermined position (of irradiation field area shown on the body surface of the subject in the optical image) 41 Display operation unit (display unit) 70 Optical image 81 Detection unit area display 100, 200 X-ray imaging device 101 Subject D1 X-ray tube-subject distance D2 Coordinate difference D3 Detection unit-body surface distance D4 X-ray tube-detection unit distance D5 Imaging unit-body surface distance D6 X-ray tube-imaging unit distance θ (the angle between the optical axis of the light source unit and the line connecting the center of the optical imaging unit and the X-ray detection unit)

Claims

1. An X-ray imaging device comprising: an X-ray irradiation unit including an X-ray tube; an X-ray detection unit which detects X-rays irradiated from the X-ray irradiation unit and transmitted through a subject; a light source unit which irradiates visible light onto an irradiation field area which indicates the area irradiated with X-rays by the X-ray irradiation unit; an optical imaging unit which has an optical axis shifted with respect to the irradiation axis of the X-rays irradiated from the X-ray irradiation unit and which captures an optical image of the subject; and a control unit which calculates an X-ray tube-to-subject distance between the X-ray tube and the subject based on the coordinates of a predetermined position within the irradiation field area which appears on the body surface of the subject in the optical image captured by the optical imaging unit.

2. The X-ray imaging device of claim 1, wherein the optical imaging unit includes a monocular camera, and the control unit calculates the X-ray tube-to-subject distance based on the coordinates of a specified position in the irradiation field area that appears on the body surface of the subject in the optical image captured by the monocular camera.

3. The X-ray imaging device described in claim 1, wherein the control unit calculates a detection-to-body-surface distance between the X-ray detection unit and the subject's body surface in the optical axis direction of the light source unit based on a coordinate difference between the coordinates of a predetermined position of the X-ray detection unit in the optical image and the coordinates of a predetermined position of the irradiation field area shown on the subject's body surface in the optical image, and calculates the X-ray tube-to-subject distance based on the calculated detection-to-body-surface distance and an X-ray tube-detection unit distance between the X-ray tube and the X-ray detection unit.

4. The X-ray imaging device described in claim 3, wherein the control unit calculates the distance between the body surface of the detection unit in the optical axis direction of the light source unit based on the coordinate difference as well as the angle between the optical axis of the light source unit and a straight line connecting the optical imaging unit and the center of the X-ray detection unit.

5. The X-ray imaging device described in claim 1, wherein the control unit calculates an imaging unit-body-surface distance between the optical imaging unit and the subject's body surface in the optical axis direction of the light source unit based on the coordinates of a predetermined position of the irradiation field area shown on the subject's body surface in the optical image, the coordinates of an imaging unit coordinate system centered on the optical imaging unit, and a relational equation for converting the coordinates of the imaging unit coordinate system into coordinates of an image coordinate system indicating coordinates in the optical image, and calculates the X-ray tube-subject distance based on the calculated imaging unit-body-surface distance and the X-ray tube-imaging unit distance between the X-ray tube and the optical imaging unit in the optical axis direction of the light source unit.

6. The X-ray imaging device described in claim 5, wherein the control unit calculates the distance between the imaging unit and the body surface in the optical axis direction of the X-ray tube based on the coordinates of a specified position of the irradiation field area shown on the body surface of the subject in the optical image, the coordinates of the imaging unit coordinate system, and the relational equation using a matrix of internal parameters of the optical imaging unit.

7. The X-ray imaging device according to claim 1, wherein the control unit calculates the X-ray tube-subject distance based on the coordinates of a center of a predetermined position of the irradiation field area shown on the body surface of the subject in the optical image.

8. The X-ray imaging device according to claim 1, wherein the optical axis of the optical imaging unit is parallel to the optical axis of the light source unit.

9. The X-ray imaging device according to claim 1, further comprising a display unit, wherein the control unit causes the calculated X-ray tube-subject distance to be displayed on the display unit.

10. The X-ray imaging device according to claim 9, wherein the control unit causes the display unit to display a detection unit area display indicating the area in the optical image in which the X-ray detection unit is located based on the calculated X-ray tube-subject distance.

Images