JP2011101745A - X-ray imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To match the central axes of an X-ray irradiator and an X-ray plane detector when sides of a subject are shot. <P>SOLUTION: Detection signals from encoders arranged in a horizontal moving mechanism 11, a suspension holding mechanism 12, an X-ray tube arm 13, an X-ray tube 2 are input to a focal position information detector 58, and accordingly, the focal point coordinates of X-rays in the X-ray tube 2 are detected. Also, detection signals from encoders arranged in a joint of a detector arm 25 and an arm base 24 are input to an FPD position information detector 57, and accordingly, central coordinates of a detection surface of an FPD 4 are detected. Radiography system driving vectors for matching the center axis of the detection surface of the FPD 4 and the center axis of the irradiation surface of the X-ray tube 2 are calculated by a radiography system driving vector calculating part 61. In this way, a radiography system driving controller 62 controls the movement of the horizontal moving mechanism 11, the suspension holding mechanism 12, the X-ray tube arm 13 and the X-ray tube 2 and positions the X-ray tube 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray imaging apparatus that obtains a fluoroscopic image of a subject, and particularly relates to imaging of a side surface of a subject.

  Conventionally, an X-ray imaging apparatus includes an X-ray irradiator that irradiates X-rays, a top plate on which the subject is placed, and an X-ray flat panel detector that detects X-rays transmitted through the subject. When photographing a fluoroscopic image of a subject, X-rays are irradiated from above the subject, and X-rays transmitted through the subject and the top plate are detected by an X-ray flat detector provided at the bottom of the top plate. Is common. Since the top plate is made of a material that hardly absorbs X-rays, the attenuation of X-rays by the top plate is very small.

  In addition, the X-ray imaging apparatus includes a C-type arm imaging apparatus in which an X-ray irradiator and an X-ray flat panel detector are connected by a C-type arm, and an X-ray irradiator and an X-ray flat panel detector. There is an X-ray imaging apparatus that can be positioned with ease. Furthermore, as disclosed in Patent Document 1, an X-ray irradiator and an X-ray flat panel detector are attached to the tip of an articulated robot arm, and the articulated robot is operated to operate the X-ray irradiator and the X-ray irradiator. Some imaging devices perform alignment with a line plane detector. Patent Document 1 describes that a visual sensor system detects target marks marked on important points of a top plate and a subject and positions an articulated robot.

  The radiographer uses these X-ray radiographing apparatuses properly depending on the radiographic part of the subject. It is clearer to place the X-ray irradiator and the X-ray flat panel detector on the upper side of the top plate mounting surface without allowing the top plate to pass through, rather than transmitting through the top plate and photographing from the top to the bottom. Sometimes you can shoot. For example, when imaging the side surface of an ankle joint, it may be preferable to raise the ankle of the subject placed on the top and irradiate with X-rays from the side surface. When the X-ray irradiator and the X-ray flat panel detector are positioned independently, the fluoroscopic imaging direction can be determined more freely than the C-arm imaging apparatus.

Japanese Patent Laid-Open No. 2-71730

  However, in the case where the X-ray irradiator and the X-ray flat detector are positioned independently, the radiographer has the central axis of the X-ray irradiated from the X-ray irradiator and the central axis of the detection surface of the X-ray flat detector. And the X-ray irradiator and the X-ray flat panel detector must be arranged to face each other. This is the same whether the alignment is performed manually or when the multi-joint robot is operated for alignment. In the case of the technique disclosed in Patent Document 1, since the target mark on the top plate cannot be used for positioning in the case of side photographing, the articulated robot must be directly operated for positioning.

  When the position of the X-ray irradiated from the X-ray irradiator is determined by visual measurement so that the center axis of the irradiation surface of the X-ray irradiator coincides with the center axis of the detection surface of the X-ray flat panel detector. Time is required, and misalignment tends to occur between the central axes of each other. If there is a deviation between the central axis of the irradiation surface of the X-ray irradiator and the central axis of the detection surface of the X-ray flat panel detector, the region of interest will be imaged without being placed in the center of the captured image, and fluoroscopic imaging will be performed again. There must be.

  Further, if the irradiation surface of the X-ray irradiator and the detection surface of the X-ray flat panel detector are not arranged in parallel to each other, oblique imaging is performed, and a fluoroscopic image in which the imaging region is extended obliquely is obtained. Will get. Furthermore, if the X-ray flat panel detector is provided with a grid, the shadow of the grid also extends obliquely. Thus, an optimal fluoroscopic image cannot be obtained.

  This invention is made | formed in view of such a situation, Comprising: In X-ray imaging apparatus with which an X-ray irradiator and an X-ray plane detector move independently, it is irradiated from an X-ray irradiator. An object of the present invention is to provide an X-ray imaging apparatus capable of matching the X-ray central axis with the central axis of the detection surface of the X-ray detector.

In order to achieve such an object, the present invention has the following configuration.
That is, the invention described in claim 1 is an X-ray imaging apparatus, in which an X-ray irradiator that irradiates X-rays, a top plate on which a subject is placed, and the subject on the top plate are placed. An X-ray flat panel detector disposed on the same side as the X-ray irradiator and moved independently of the X-ray irradiator; and the X-ray connected to one side of the top plate Based on the arm supporting the detector, the joint provided in the arm, the angle detector for detecting the rotation angle of the joint, and the rotation angle detected by the angle detector, the X-ray flat panel detector A detector position information detector for detecting a center coordinate and a center axis angle of a detection surface; a focus position information detector for detecting a focus coordinate and a center axis angle of an X-ray emitted from the X-ray irradiator; and the detection Positioning so that the central axis of the surface coincides with the central axis of the X-rays emitted from the X-ray irradiator Characterized in that it comprises a control unit.

  According to the first aspect of the present invention, in the X-ray imaging apparatus in which the X-ray irradiator and the X-ray flat panel detector are moved independently from each other, the X-ray flat panel detector is disposed on one side of the top plate. It is connected via an arm. This arm is provided with a joint, and the rotation angle of the joint is detected by an angle detector. Based on the detected rotation angle, the detector position information detection unit detects the center coordinates and the center axis angle of the detection surface of the X-ray flat panel detector. Further, the focal position information detection unit detects the focal point coordinates and the central axis angle of the X-rays emitted from the X-ray irradiator. Based on the center coordinates and center axis angle of the detection surface and the focal point and center axis angle of the X-ray, the positioning control unit matches the center axis of the detection surface with the center axis of the X-ray irradiated from the X-ray irradiator. .

  As a result, it is not necessary for the photographer to match the central axis of the detection surface of the X-ray flat panel detector with the central axis of the X-ray emitted from the X-ray irradiator, so that the imaging time can be shortened. it can. In addition, since the X-ray flat panel detector and the X-ray irradiator can be positioned more accurately than the eye measurement, the imaging region is not displaced from the center of the imaging image. In addition, the captured image does not extend obliquely. As a result, re-shooting due to erroneous shooting can be prevented.

  In addition, the positioning control unit calculates an X-ray focus target coordinate at a predetermined distance with respect to the center coordinate of the detection surface and an X-ray center axis target angle that coincides with the center axis of the detection surface. A focus target value calculation unit, and an irradiator that is a difference between a focus target coordinate and center axis target angle calculated by the focus target value calculation unit and an X-ray focus coordinate and center axis angle detected by the focus position information detection unit An irradiator drive vector calculating unit that calculates a drive vector and an irradiator drive control unit that controls movement of the X-ray irradiator based on the irradiator drive vector may be provided.

  According to the above configuration, the X-ray coincident with the X-ray focus target coordinate and the center axis of the detection surface at which the focus target value calculation unit is at a predetermined distance from the center coordinate of the detection surface of the X-ray flat panel detector The center axis target angle of is calculated. The X-ray focal point target coordinates and the central axis target angle are targets for moving the irradiator. The irradiator drive vector is calculated by calculating the irradiator drive vector, which is the difference between the focus target coordinate and the center axis target angle calculated by the focus target value calculator and the X-ray focus coordinate and center axis angle detected by the focus position information detector. Part calculates. This irradiator drive vector is the amount of movement required to align the X-ray irradiator relative to the X-ray flat panel detector. The irradiator drive control unit controls the movement of the irradiator based on the irradiator drive vector, so that the center axes of the X-ray flat panel detector coincide with each other at a predetermined distance from each other. And the X-ray irradiator can be aligned so that the X-ray focal point and central axis are located at an angle.

  In addition, the positioning control unit is configured so that the detection surface coincides with a central target coordinate of the detection surface at a predetermined distance with respect to the focal point coordinate and a central axis of the X-ray irradiated from the X-ray irradiator. A detector target value calculation unit for calculating a central axis target angle, and a central target coordinate and a central axis target angle of the detection surface calculated by the detector target value calculation unit and the detection detected by the detector position information detection unit A detector drive vector calculating unit that calculates a detector drive vector that is a difference between the center coordinate and the center axis angle of the surface; and a detector drive that controls movement of the X-ray flat panel detector based on the detector drive vector And a control unit.

  According to the above configuration, the detector target value calculation unit has a predetermined target distance with respect to the X-ray focal point coordinates, and the center target coordinates of the detection surface and the central axis of the X-rays emitted from the X-ray irradiator The center axis target angle of the detection surface that coincides with is calculated. The center target coordinates and the center axis target angle of the detection surface are targets for moving the X-ray flat panel detector. A detector drive vector that is the difference between the center target coordinate and center axis target angle of the detection surface calculated by the detector target value calculation unit and the center coordinate and center axis angle of the detection surface detected by the detector position information detection unit is The detector drive vector calculation unit calculates. This detector drive vector is the amount of movement necessary to align the X-ray flat detector irradiator relative to the X-ray irradiator. The detector drive control unit controls the movement of the X-ray flat panel detector based on the detector drive vector so that the center axes of the X-ray focal point coordinates coincide with each other at a predetermined distance. The x-ray flat detector can be aligned so that the focus and the central axis of the detection surface are arranged at an angle.

  Moreover, it is preferable that the said arm is equipped with the motor which drives rotation of the said joint for every said joint. Thus, the detector drive control unit can accurately control the movement of the X-ray flat panel detector.

  The invention described in claim 5 is an X-ray imaging apparatus, wherein an X-ray irradiator that irradiates X-rays, a top plate on which the subject is placed, and the subject on the top plate is placed. An X-ray flat panel detector disposed on the same side as the X-ray irradiator and moved independently of the X-ray irradiator; and the X-ray connected to one side of the top plate Based on the arm supporting the detector, the joint provided in the arm, the angle detector for detecting the rotation angle of the joint, and the rotation angle detected by the angle detector, the X-ray flat panel detector A detector position information detector for detecting a center coordinate and a center axis angle of a detection surface; a focus position information detector for detecting a focus coordinate and a center axis angle of an X-ray emitted from the X-ray irradiator; and the detection X-ray focus target coordinates at a predetermined distance from the center coordinates of the surface and the detection surface A focus target value calculation unit that calculates a center axis target angle of an X-ray that matches the center axis, a focus target coordinate and center axis target angle of the X-ray calculated by the focus target value calculation unit, and the focus position information detection unit An irradiator drive vector calculation unit that calculates an irradiator drive vector that is a difference between the focal point coordinates and the central axis angle of the detected X-ray, and a central axis of the detection surface and X-rays irradiated from the X-ray irradiator And an alarm device for notifying that the center axis coincides.

  According to the fifth aspect of the present invention, in the X-ray imaging apparatus in which the X-ray irradiator and the X-ray flat panel detector are moved independently of each other, the X-ray flat panel detector is placed on one side of the top plate. It is connected via an arm. This arm is provided with a joint, and the rotation angle of the joint is detected by an angle detector. Based on the detected rotation angle, the detector position information detection unit detects the center coordinates and the center axis angle of the detection surface of the X-ray flat panel detector. Further, the focal position information detection unit detects the focal point coordinates and the central axis angle of the X-rays emitted from the X-ray irradiator. The irradiator drive vector is calculated by calculating the irradiator drive vector, which is the difference between the focus target coordinate and the center axis target angle calculated by the focus target value calculator and the X-ray focus coordinate and center axis angle detected by the focus position information detector. Part calculates. This irradiator drive vector is the amount of movement required to align the X-ray irradiator relative to the X-ray flat panel detector. When the illuminator drive vector becomes zero by moving the X-ray irradiator with respect to the X-ray flat panel detector, the center axis of the detection surface and the central axis of the X-ray irradiated from the X-ray irradiator Matches. The notification device notifies that the central axis of the detection surface coincides with the central axis of the X-rays emitted from the X-ray irradiator.

  Thus, even when the radiographer manually aligns the X-ray irradiator and the X-ray flat panel detector, the center axis of the detection surface of the X-ray flat panel detector and the central axis of the irradiation surface of the X-ray irradiator are determined. Can be matched exactly. As a result, the imaging region does not deviate from the center of the captured image, and the captured image does not extend obliquely, so that re-imaging due to erroneous imaging can be prevented.

  The arm preferably includes a plurality of the joints. By providing a plurality of joints on the arm, the degree of freedom of movement of the arm can be increased, and the degree of freedom of movement of the X-ray flat panel detector can be increased.

  In addition, a rail provided along the longitudinal direction of the top plate is provided on a side portion of the top plate, and the arm is connected to the top plate via an arm base portion slidable along the rail. Also good. The arm can be smoothly moved in the longitudinal direction of the top plate by connecting the arm to the top plate via an arm base portion that is slidable along the rail.

  A grid for removing scattered X-rays from X-rays transmitted through the subject may be provided on the X-ray irradiator side of the X-ray flat panel detector. Since the central axis of the irradiation surface of the X-ray irradiator coincides with the central axis of the detection surface of the X-ray flat panel detector, it is possible to prevent the grid shadow from extending obliquely. As described above, since the grid can be used also in the X-ray imaging apparatus in which the X-ray irradiator and the X-ray plane detector are moved independently from each other, the scattered X-rays can be removed and noise can be reduced. Photographed images can be obtained.

  According to the X-ray imaging apparatus of the present invention, in the X-ray imaging apparatus in which the X-ray irradiator and the X-ray flat panel detector are moved independently of each other, the central axis of the detection surface of the X-ray flat panel detector and X The central axis of the irradiation surface of the line irradiator can be exactly matched. As a result, the imaging region does not deviate from the center of the captured image, and the captured image does not extend obliquely, so that re-imaging due to erroneous imaging can be prevented.

1 is a side view of an X-ray imaging apparatus according to Embodiment 1. FIG. 1 is a side view of an X-ray imaging apparatus according to Embodiment 1. FIG. 1 is a front view of an X-ray imaging apparatus according to Embodiment 1. FIG. 2 is a longitudinal sectional view of an arm base portion according to Embodiment 1. FIG. 1 is a schematic diagram of a detector arm according to Embodiment 1. FIG. 1 is a block diagram illustrating a configuration of an X-ray imaging apparatus according to Embodiment 1. FIG. It is explanatory drawing which shows the positional relationship of the X-ray plane detector which concerns on Example 1, and the focus of an X-ray. 6 is a schematic diagram of a detector arm according to Embodiment 2. FIG. 6 is a block diagram illustrating a configuration of an X-ray imaging apparatus according to Embodiment 2. FIG. 6 is a block diagram illustrating a configuration of an X-ray imaging apparatus according to Embodiment 3. FIG.

Embodiment 1 of the present invention will be described below with reference to the drawings.
1 is a side view of the X-ray imaging apparatus, FIG. 2 is a side view of the X-ray imaging apparatus viewed from the subject's head, and FIG. 3 is a front view of the X-ray imaging apparatus.

<X-ray equipment>
As shown in FIG. 1, an X-ray imaging apparatus 1 is attached to an X-ray tube 2 suspended vertically from a ceiling, a bed 3 on which a subject M to be imaged is placed, and a bed 3. X-ray flat panel detector 4 (Flat Panel Detector; hereinafter referred to as FPD).

The X-ray tube 2 includes an X-ray tube operation unit 5 for setting various conditions for X-ray imaging, an X-ray tube monitor 6 for displaying the set conditions, and a handle for manually moving and rotating the X-ray tube 2. 7 and a collimator 8 for narrowing down X-rays generated in the X-ray tube 2. The surface of the collimator 8 is referred to as an X-ray irradiation surface. X-ray tube operating unit 5 can set the distance or a SID (Source Image Distance) L _GF connecting the center F of FPD4 the X-ray focal point G in the X-ray tube 2 (see FIG. 3). The X-ray tube 2 corresponds to the X-ray irradiator in the present invention.

  The X-ray tube 2 can be moved in the X direction, which is the short direction of the bed 3, and the Y direction, which is the longitudinal direction of the bed 3, by a horizontal movement mechanism 11 disposed on the ceiling. The horizontal movement mechanism 11 is attached with an upper end of a suspension holding mechanism 12 that holds the X-ray tube 2 up and down in the vertical direction. The X-ray tube 2 is attached to the lower end of the suspension holding mechanism 12 via an X-ray tube arm 13. The suspension holding mechanism 12 holds the X-ray tube 2 so that the X-ray tube 2 can be moved up and down in the vertical direction, that is, in the Z direction that is the ceiling direction. The X-ray tube arm 13 is attached so as to be rotatable around the axis of the suspension holding mechanism 12. The X-ray tube 2 is suspended and held around θ1 parallel to a plane including the axis of the suspension holding mechanism 12 and the axis of the X-ray tube arm 13, and around θ2 around the axis of the X-ray tube arm 13. The mechanism 12 can rotate around θ3 around the axis of the mechanism 12.

  The horizontal movement mechanism 11, the suspension holding mechanism 12, the X-ray tube arm 13 and the X-ray tube 2 are provided with motors (not shown), respectively, in six directions of X, Y, Z, θ1, θ2, and θ3, respectively. The X-ray tube 2 can be moved manually or electrically. The X-ray tube operation unit 2 can select whether to move manually or electrically. When the X-ray tube 2 is moved manually, it can be moved by operating the handle 7. When the X-ray tube 2 is moved electrically, it can be moved by operating the X-ray tube operation unit 2. Thus, the X-ray tube 2 can arbitrarily change the total six degrees of freedom of the position in the three-dimensional space and the rotation angle around the three axes.

  Further, the horizontal movement mechanism 11, the suspension holding mechanism 12, the X-ray tube arm 13 and the X-ray tube 2 are each provided with an encoder, and each movement amount in six directions of X, Y, Z, θ1, θ2, and θ3 is provided. Can be detected.

  As shown in FIG. 2, the horizontal movement mechanism 11 is supported by two fixed rails 14 and 15 fixed to the ceiling in parallel to each other and movably along both rails so as to be orthogonal to both rails. The moving rail 16 is provided. The moving rail 16 moves in the Y direction along the fixed rail 14 and the fixed rail 15. The upper end of the suspension holding mechanism 12 is attached to the moving rail 16. The suspension holding mechanism 12 moves in the Y direction along the fixed rail 14 and the fixed rail 15 together with the moving rail 16, and moves in the X direction along the moving rail 16.

  The bed 3 includes a top plate 21 on which the subject M is placed and a base 22 that supports the top plate 21. A rail 23 is fixed to one side of the top plate 21 along the longitudinal direction of the top plate 21. A detector arm 25 is connected to the rail 23 via an arm base portion 24. An FPD 4 is attached to the tip of the detector arm 25. Thus, the X-ray tube 2 and the FPD 4 can move independently. The detector arm 25 corresponds to the arm in the present invention.

  In the first embodiment, the FPD 4 employs a direct conversion X-ray detector using an X-ray sensitive semiconductor such as a-Se (amorphous selenium). A grid 26 for removing scattered X-rays included in the X-rays irradiated from the X-ray tube 2 is detachably mounted on the surface of the FPD 4.

  Next, with reference to FIG. 4, the arm base part 24 which connects the detector arm 25 and the side part of the top plate 21 is demonstrated. FIG. 4 is a longitudinal sectional view of the arm base portion. The arm base 24 is attached to a rail 23 provided on the side of the top plate 21 so as to be movable along the top plate 21. The upper part of the arm base part 24 is connected to the lower end of the detector arm 25. The arm base portion 24 is supported by sandwiching the upper end portion of the rail 23 between the two rollers 31 and 32. The amount of movement of the arm base portion 24 is detected by an encoder 34 that detects the amount of rotation of the roller 33 whose one end is in contact with the rail 23.

<Detector arm>
Next, the configuration of the detector arm 25 will be described with reference to FIG. FIG. 5 is a schematic diagram showing a joint structure of a detector arm joint and a link in a skeleton diagram.

  The detector arm 25 has seven links, a first link LN1 to a seventh link LN7, and six joints, a first joint EL1 to a sixth joint EL6. The lower end of the first link LN1 is fixed to the arm base 24. That is, the detector arm 25 can move along the side of the top plate 21 in the Y direction on the rail 23 together with the arm base portion 24.

  The first link LN1 and the second link LN2 are connected by a first joint EL1 so as to be rotatable about the link axis as a rotation axis. The second link LN2 and the third link LN3 are coupled to each other by a second joint EL2 so as to be rotatable about a plane perpendicular to the plane including the link axes of the second link LN2 and the third link LN3. In FIG. 5, a third joint EL3 and a fifth joint EL5 represented by rectangles like the first joint EL1 are joints whose link axes are links connected to the respective joints. Further, the fourth joint EL4 and the sixth joint EL6, which are displayed in a circle like the second joint EL2, have a rotation axis in the direction perpendicular to the plane including the link axis of each connected link.

  The third link LN3 and the fourth link LN4 are rotatably connected by a third joint EL3, and the fourth link LN4 and the fifth link LN5 are rotatably connected by a fourth joint EL4. Similarly, the fifth link LN5 and the sixth link LN6 are rotatably connected by a fifth joint EL5, and the sixth link LN6 and the seventh link LN7 are rotatably connected by a sixth joint EL6. In addition, encoders 41a to 41f are attached to the respective joints from the first joint EL1 to the sixth joint EL6.

The detector arm 25 is a 6-DOF multi-joint arm having six joints from the first joint EL1 to the sixth joint EL6. Therefore, the FPD 4 attached to the tip of the detector arm 25 can arbitrarily change the total six degrees of freedom of the position in the three-dimensional space and the rotation angle around the three axes.
In the following, when all the links from the first link LN1 to the seventh link LN7 are collectively referred to as a link LN, and when all the joints from the first joint EL1 to the sixth joint EL6 are collectively referred to, It is expressed as joint EL. Further, when all the encoders of the first encoder 41a to the sixth encoder 41f are collectively referred to as an encoder 41. The encoder 41 corresponds to the angle detector in the present invention.

  The rotation angle of each joint can be detected by the encoder 41 attached to each joint EL. Each joint EL can be manually rotated. Each joint EL prevents rotation due to its own weight due to frictional force. The photographer can manually set the position and orientation of the FPD 4 arbitrarily according to the size of the body of the subject M and the imaging region.

  The length from the first indirect EL1 to the second joint EL2 is a, and the length from the second joint EL2 to the third joint EL3 is b. The length from the third joint EL3 to the fourth joint EL4 is c, and the length from the fourth joint EL4 to the fifth joint EL5 is d. The length from the fifth joint EL5 to the sixth joint EL6 is e, and the length from the sixth joint EL7 to the center of the FPD4 is f.

<Control configuration>
Next, the control configuration of the X-ray imaging apparatus will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the X-ray imaging apparatus.

  The X-ray imaging apparatus 1 includes an image processing unit 51 that configures a fluoroscopic image based on an X-ray detection signal converted from X-rays by the FPD 4, a monitor 52 that displays the configured fluoroscopic image, and a configuration A storage unit 53 for storing the fluoroscopic images, an operation unit 54 for setting various conditions of X-ray imaging provided separately from the X-ray tube operation unit 5, and a host computer 55 for overall control thereof. Is provided. The operation unit 54 includes a keyboard, a mouse, a joystick, and the like.

  The host computer 55 includes an imaging control unit 56, an FPD position information detection unit 57, a focus position information detection unit 58, and a positioning control unit 59. The imaging control unit 56 transfers the fluoroscopic image transferred from the image processing unit 51 to the monitor 52 or the storage unit 53 in accordance with an instruction from the operation unit 54.

  A detection signal is input to the FPD position information detection unit 57 from the encoder 34 of the detector arm 25. Further, the FPD position information detector 57 also receives detection signals from the encoders 41 of the detector arm 25. The FPD position information detection unit 57 detects the coordinates of the central portion F of the FPD 4 in the reference coordinate system and the angle of the central axis passing through the central portion F from these detection signals. The FPD position information detection unit 57 corresponds to the detector position information detection unit in the present invention.

  A detection signal is input to the focal position information detection unit 58 from encoders provided in the X-ray tube 2, the horizontal movement mechanism 11, the suspension holding mechanism 12, and the X-ray tube arm 13. Based on these detection signals, the coordinates of the focal point G of the X-ray tube 2 in the reference coordinate system and the angle of the central axis of the X-ray passing through the focal point G are detected.

Positioning control unit 59 calculates the distance L _GF apart coordinates angle and SID center coordinates and central axes of FPD4 detected by FPD position information detecting unit 57, positions the focus G of the X-ray tube 2 in this coordinate While controlling, positioning control is performed so that the X-ray axis irradiated from the X-ray tube 2 and the center axis of the FPD 4 coincide. The positioning control unit 59 includes a focus target value calculation unit 60, an imaging system drive vector calculation unit 61, and an imaging system drive control unit 62.

  The focus target value calculation unit 60 calculates X-ray focus target coordinates that are SIDs away from the coordinates of the FPD 4 detected by the FPD position information detection unit 57, and the X-ray center axis target angle that coincides with the center axis of the FPD 4 Is calculated. That is, the focus target coordinates and the focus target angle calculated by the focus target value calculation unit 60 are the targets for the movement of the focus G of the X-ray tube 2. At this time, if the calculated focus target coordinates are at a position where the X-ray tube 2 is not movable, such as the lower part of the top plate 1, the monitor 52 or the X-ray tube monitor 5 is connected via the imaging control unit 56. Alert the photographer with a warning above.

  The imaging system drive vector calculation unit 61 compares the focus target coordinates and the focus target angle calculated by the focus target value calculation unit 60 with the coordinates of the X-ray focus G detected by the focus position information detection unit 58 and the angle of the central axis. An imaging system driving vector is calculated. The calculated imaging system drive vector is a drive amount in each of six directions of X, Y, Z, θ1, θ2, and θ3. The imaging system drive vector calculator 61 corresponds to the irradiator drive vector calculator in the present invention.

  The imaging system drive control unit 62 applies the X-ray tube 2, the horizontal movement mechanism 11, the suspension holding mechanism 12, and the X-ray tube arm 13 based on the driving amounts in the six directions calculated by the imaging system drive vector calculation unit 61. A control signal (current command value) is output to each motor provided. The X-ray tube 2, the horizontal movement mechanism 11, the suspension holding mechanism 12 and the X-ray tube arm 13 are moved by the imaging system drive control unit 62 controlling each motor, and the X-ray tube 2 is moved to the target position. Positioning in a posture can be performed. The imaging system drive control unit 62 corresponds to the irradiator drive control unit in the present invention.

<Positioning operation>
Next, calculation of coordinates in the reference coordinates of the FPD 4, focus target coordinates, and focus target angle will be described with reference to FIGS. 2, 4, and 5 to 7. FIG. 7 is an explanatory diagram showing the positional relationship between the X-ray flat panel detector and the focal point of the X-ray at the target position for alignment. After the photographer manually positions the FPD 4, when the X-ray tube 2 is instructed by the X-ray tube operation unit 5 or the operation unit 54, the FPD position information detection unit 57 in the host computer 55 sets the reference coordinates of the FPD 4. calculate.

The rotation amount of the first joint EL1 is φ _O , the rotation amount of the second joint EL2 is θ _A , the rotation amount of the third joint EL3 is φ _B , the rotation amount of the fourth joint EL4 is θ _C , and the rotation of the fifth joint EL5 Let φ _{D be} the amount, and θ _{E be} the rotation amount of the sixth joint EL6.

The reference coordinate system _O as _{R -X} R _Y R _Z R, the coordinate system converted by the rotation of the joint EL1 and _O O _-X O _Y O _{Z O.} Furthermore, the coordinate system converted by the rotation of the joint EL2 and _{O A -X A Y A Z A} . Similarly, each of the coordinate system converted by the joint EL3~ joint _{EL6, O B -X B Y B} Z B, O C -X C Y C Z C, O D -X D Y D Z D, O E and -X _E Y _E Z _E.

When the coordinate system of the center origin of the first joint portion EL1 articular EL1 is not rotating at all the O-XYZ, O-XYZ reference coordinate system _{O R -X} R _Y R _Z R transformation which relates the following conversion It becomes an expression.

When a coordinate system joints EL1 is rotated phi _O and _{O-X O Y O Z O} , O-X O Y O Z O conversion which relates to the coordinate system O-XYZ before joint EL1 is rotated following conversion It becomes an expression.

The coordinate system AX _A Y _A Z _{A in} which the joint EL2 rotates θ _A and the coordinate system O-X _O Y _O Z _{O in} which the joint EL2 does not rotate at all are related by the following conversion formula.

The coordinate system _{A-X A} Y _{A Z A} of the coordinate system _{B-X B} joint EL3 is rotated φ _B Y _{B Z B} and joint EL3 is not rotating at all, are related by the following conversion equation.

The coordinate system C-X _C Y _C Z _{C in} which the joint EL4 rotates θ _C and the coordinate system B-X _B Y _B Z _{B in} which the joint EL4 does not rotate at all are related by the following conversion formula.

The coordinate system _{C-X C} Y _{C Z C} of the coordinate system _{D-X D} Y _{D Z D} and joint EL5 articular EL5 is rotated phi _D is not rotated at all, are related by the following conversion equation.

The coordinate system _{D-X D} Y _{D Z D} coordinate joint EL6 rotates theta _E based _{E-X E} Y _{E Z E} and joint EL6 is not rotating at all, are related by the following conversion equation.

The transformation relating the coordinate system E-X _E Y _E Z _E to the reference coordinate system O _R -X _R Y _R Z _R is the following transformation formula.

Transformation relating the coordinate system _{F-X F} Y F _{Z F} of the center F of FPD4 the reference coordinate system _{O R -X} R _Y R _Z R are the following conversion equation.

Transformation relating the coordinate system _{G-X G} Y G _{Z G} focus G of the detector 2 is aligned goals reference coordinate system _{O R -X} R _Y R _Z R are the following conversion equation.

Since the center F of the FPD 4 is (0, 0, f) on the coordinate system E-X _E Y _E Z _E , the point F is converted into the coordinate system O _R -X _R Y _R Z _R in the following equation.

As shown in FIG. 7, since the point G is located at (L, 0, 0) on the coordinate system F-X _F Y _F Z _F , the point G on the coordinate system E-X _E Y _E Z _E ( L, 0, f). From this, point G in the formula is converted into the coordinate system _{O R -X R Y R Z R} .

In addition, the Euler angles (φ, θ, ξ) of the coordinate system G-X _G Y _G Z _G are calculated by the following equations.

The coordinates of the center F of the FPD 4 can be detected by Expressions 8 to 11. Further, the X-ray focal point target coordinates and the X-ray central axis target angle that coincides with the central axis of the FPD detection surface can be calculated by Equations 8-13. An irradiator drive vector that is a difference between the X-ray focal point coordinate and the central axis target angle calculated in this way and the X-ray focal point coordinate and central axis angle before alignment is calculated. Based on this irradiator driving vector, by moving the X-ray tube 2, relative to the coaxially with the center F of the focus G and FPD4 at a SID distance L _GF.

<X-ray photography>
After the alignment between the X-ray tube 2 and the FPD 4 is completed, when the photographer inputs an imaging instruction from the operation unit 54, the subject M is irradiated with X-rays from the X-ray tube 2. X-rays transmitted through the subject M are detected by the FPD 4. The FPD 4 converts the X-rays into X-ray detection signals according to the X-ray intensity. From the converted X-ray detection signal, noise is removed by the image processing unit 51 to form a fluoroscopic image. The configured fluoroscopic image is displayed on the monitor 33 or stored in the storage unit 11 via the imaging control unit 32.

  As described above, according to the X-ray imaging apparatus 1 of the first embodiment, even if the FPD 4 is aligned at an arbitrary position, the central axis of the detection surface of the FPD 4 and the central axis passing through the focal point G of the X-ray tube 2 are obtained. Can be matched. Since the photographer does not have to make the center axis of the detection surface of the FPD 4 coincide with the center axis of the X-ray by eye measurement, the photographing time can be shortened. Further, since the FPD 4 and the X-ray tube 2 can be positioned more accurately than the visual measurement, the imaging region is not displaced from the center of the imaging image. Further, since the center axis of the detection surface of the FPD 4 and the center axis passing through the focal point G of the X-ray tube 2 coincide with each other, the detection surface of the FPD 4 and the irradiation surface of the X-ray tube 2 are positioned in parallel. It doesn't stretch diagonally or the shadow of the grid doesn't stretch. As a result, re-shooting due to erroneous shooting can be prevented.

  A second embodiment of the present invention will be described below with reference to FIGS. FIG. 8 is a schematic diagram of a detector arm in the second embodiment, and FIG. 9 is a configuration diagram of the X-ray imaging apparatus in the second embodiment. In addition, about the same structure as Example 1, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  A feature of the second embodiment is that the joints EL1 to EL6 provided in the detector arm 71 are provided with motors MT1 to MT6 that rotate and drive the joints EL. In the X-ray imaging apparatus 70 according to the second embodiment, after the X-ray tube 2 is manually aligned, the central axis of the detection surface of the FPD 4 with respect to the central axis of the X-rays emitted from the X-ray tube 2 by the control unit 72 The movement of the detector arm 71 is controlled so as to match. The control unit 72 includes an imaging control unit 56, an FPD position information detection unit 57, and a focus position information detection unit 58 as in the first embodiment, and further includes a positioning control unit 73.

The positioning control unit 73 in the second embodiment uses the coordinates of the X-ray focal point G in the X-ray tube 2 detected by the focal position information detection unit 58 and the coordinates of the X-ray central axis angle and the SID distance _LGF. The position of the center F of the detection surface of the FPD 4 is calculated and the position of the coordinates is controlled so that the X-ray axis irradiated from the X-ray tube 2 coincides with the center axis of the detection surface of the FPD 4. The positioning control unit 73 includes an FPD target value calculation unit 74, a detector system drive amount calculation unit 75, and a detector system drive control unit 76.

  The FPD target value calculation unit 74 calculates the center target coordinates of the detection surface of the FPD 4 that is SID away from the coordinates of the focus G detected by the focus position information detection unit 58, and the X-rays irradiated from the X-ray tube 2. The center axis target angle of the detection surface of the FPD 4 that coincides with the center axis is calculated. That is, the center target coordinates and the center axis target angle calculated by the FPD target value calculation unit 74 are the targets for movement of the center F of the FPD 4. At this time, if the calculated center target coordinates are at a position where the FPD 4 is not movable, such as the lower part of the top board 1, a warning is given on the monitor 52 or the X-ray tube monitor 5 via the imaging control unit 56. To inform the photographer.

  The detector system drive vector calculator 75 calculates the center target coordinates and center axis target angle calculated by the FPD target value calculator 74, the center coordinates of the detection surface of the FPD 4 detected by the FPD position information detector 57, and the angle of the center axis. The detector system drive vector that is the difference between the two is calculated. The calculated detector system driving vector is the driving amount of each motor provided in the arm base unit 25 and the detector arm 71.

  Based on the detector system drive vector calculated by the detector system drive vector calculation unit 75, the detector system drive control unit 76 transfers the motor provided in the arm base unit 25 and each motor MO provided in the detector arm 71. A control signal (current command value) is output. The detector system drive control unit 76 controls each motor, so that the arm base unit 25 and the detector arm 71 move, and the FPD 4 can be positioned to the target position in the target posture.

  According to the invention of the second embodiment, even if the X-ray tube 2 is aligned at an arbitrary position, the center axis of the detection surface of the FPD 4 and the center axis of the X-ray passing through the focal point of the X-ray tube 2 are matched. Can do. Since the photographer does not have to make the center axis of the detection surface of the FPD 4 coincide with the center axis of the X-ray by eye measurement, the photographing time can be shortened. In addition, since the FPD 4 and the X-ray tube 2 can be positioned more accurately than the visual measurement, the imaging region is not displaced from the center of the imaging image. Also, since the center axis of the detection surface of the FPD 4 and the center axis passing through the focal point G of the X-ray tube 2 coincide with each other, the detection surface of the FPD 4 and the irradiation surface of the X-ray tube 2 are positioned in parallel. The shot image does not stretch diagonally or the grid shadow does not stretch. As a result, re-shooting due to erroneous shooting can be prevented.

  A third embodiment of the present invention will be described below with reference to FIG. FIG. 10 is a configuration diagram of an X-ray imaging apparatus according to the third embodiment.

  The feature of the third embodiment is that the X-ray tube 2 is also manually aligned after the FPD 4 is manually aligned. As in the first embodiment, the control unit 81 in the third embodiment includes a shooting system drive vector, an FPD position information detection unit 57, a focus position information detection unit 58, and a focus target value calculation unit 60, in addition to the shooting control unit 56. And a calculation unit 82.

  Similarly to the imaging system drive vector calculation unit 61 of the first embodiment, the imaging system drive vector calculation unit 82 uses the focus target coordinates and the focus target angle calculated by the focus target value calculation unit 60 and the X detected by the focus position information detection unit 58. An imaging system drive vector that is the difference between the coordinates of the focal point G of the line and the angle of the central axis is calculated. The imaging system drive vector calculation unit 82 further displays the imaging system drive vector on the X-ray tube monitor 6. That is, the required drive amounts in the X, Y, Z, θ1, θ2, and θ3 directions are displayed on the X-ray tube monitor 6. The photographer can accurately match the center axis of the X-rays emitted from the X-ray tube 2 with the center axis of the detection surface of the FPD 4 with reference to this display. This display may indicate a specific direction, or may blink if the direction in which the photographer operates the X-ray tube 2 approaches the target. Further, when movement in each direction of X, Y, Z, θ1, θ2, and θ3 is made accurate, the movement may be locked in each direction. The X-ray tube monitor 6 corresponds to a notification device in the present invention.

  According to the invention of Embodiment 3, X-rays irradiated from the central axis of the detection surface of the FPD 4 and the X-ray tube 2 even when the photographer manually aligns the X-ray irradiator and the X-ray flat panel detector. It is possible to make it coincide with the center axis of. In addition, since the center axis of the detection surface of the FPD 4 and the center axis passing through the focal point G of the X-ray tube 2 coincide with each other, the detection surface of the FPD 4 and the irradiation surface of the X-ray tube 2 are positioned in parallel. The image does not stretch diagonally or the grid shadow does not stretch. As a result, the imaging region does not deviate from the center of the captured image, and re-imaging due to erroneous imaging can be prevented.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (1) In the above-described embodiment, the detector arm 25 is mounted on the arm base portion 24 that can move along the side surface of the top plate 3, but the detector arm 25 is directly mounted on the side surface of the top plate 3. Also good.

  (2) In the above-described embodiment, the detector arm 25 includes the six joints EL. However, the number of joints may be larger or smaller. If the number of joints EL is large, the FPD 4 can be moved finely. Even if the number of joints EL is small, the X-ray tube 2 has six degrees of freedom, so that the central axis of the detection surface of the FPD 4 and the central axis of the X-rays irradiated from the X-ray tube 2 should coincide with each other. Can

  (3) In the embodiment described above, the FPD 4 is a direct conversion X-ray detector using a semiconductor, but may be an indirect conversion X-ray detector, a film cassette, or an image intensifier.

DESCRIPTION OF SYMBOLS 1 ... X-ray imaging apparatus 2 ... X-ray tube 4 ... X-ray plane detector (FPD)
6 ... X-ray tube monitor 9 ... Grid 21 ... Top plate 23 ... Rail 24 ... Arm base unit 25 ... Detector arm 41 ... Encoder 57 ... FPD coordinate detection unit 58 ... Focus coordinate detection unit 59, 73 ... Positioning control unit EL1 EL6 ... Joint MT1 to MT7 ... Motor

Claims (8)

An X-ray imaging apparatus,
An X-ray irradiator that emits X-rays;
A top plate on which the subject is placed;
An X-ray flat panel detector disposed on the same side as the X-ray irradiator with respect to the surface of the top plate on which the subject is placed, and moved independently of the X-ray irradiator;
An arm connected to one side of the top plate and supporting the X-ray detector;
A joint provided on the arm;
An angle detector for detecting a rotation angle of the joint;
A detector position information detector for detecting a center coordinate and a center axis angle of a detection surface of the X-ray flat panel detector based on a rotation angle detected by the angle detector;
A focal position information detection unit for detecting a focal coordinate and a central axis angle of X-rays emitted from the X-ray irradiator;
An X-ray imaging apparatus comprising: a positioning control unit that aligns a central axis of the detection surface with a central axis of X-rays emitted from the X-ray irradiator. The X-ray imaging apparatus according to claim 1,
The positioning control unit
A focus target value calculation unit for calculating an X-ray focus target coordinate at a predetermined distance with respect to the center coordinate of the detection surface and an X-ray center axis target angle coinciding with the center axis of the detection surface;
An irradiator that calculates an irradiator drive vector that is a difference between a focus target coordinate and center axis target angle calculated by the focus target value calculation unit and an X-ray focus coordinate and center axis angle detected by the focus position information detection unit. A drive vector calculation unit;
An X-ray imaging apparatus comprising: an irradiator drive control unit that controls movement of the X-ray irradiator based on the irradiator drive vector. The X-ray imaging apparatus according to claim 1,
The positioning control unit
Detection for calculating a central target coordinate of the detection surface that coincides with a central target coordinate of the detection surface at a predetermined distance from the focal point coordinate and a central axis of the X-ray irradiated from the X-ray irradiator. A target value calculator,
A detector that is the difference between the center target coordinates and center axis target angle of the detection surface calculated by the detector target value calculation unit and the center coordinates and center axis angle of the detection surface detected by the detector position information detection unit A detector drive vector calculation unit for calculating a drive vector;
An X-ray imaging apparatus comprising: a detector drive control unit that controls movement of the X-ray flat panel detector based on the detector drive vector. The X-ray imaging apparatus according to claim 3,
The said arm is equipped with the motor which drives rotation of the said joint for every said joint. X-ray imaging apparatus characterized by the above-mentioned. An X-ray imaging apparatus,
An X-ray irradiator that emits X-rays;
A top plate on which the subject is placed;
An X-ray flat panel detector disposed on the same side as the X-ray irradiator with respect to the surface of the top plate on which the subject is placed, and moved independently of the X-ray irradiator;
An arm connected to one side of the top plate and supporting the X-ray detector;
A joint provided on the arm;
An angle detector for detecting a rotation angle of the joint;
A detector position information detector for detecting a center coordinate and a center axis angle of a detection surface of the X-ray flat panel detector based on a rotation angle detected by the angle detector;
A focal position information detection unit for detecting a focal coordinate and a central axis angle of X-rays emitted from the X-ray irradiator;
A focus target value calculation unit for calculating an X-ray focus target coordinate at a predetermined distance with respect to the center coordinate of the detection surface and an X-ray center axis target angle coinciding with the center axis of the detection surface;
An irradiator drive vector that is a difference between the X-ray focus target coordinates and center axis target angle calculated by the focus target value calculation unit and the X-ray focus coordinates and center axis angle detected by the focus position information detection unit is calculated. An irradiator drive vector calculating unit to perform,
An X-ray imaging apparatus comprising: a notification device that notifies that a central axis of the detection surface and a central axis of X-rays emitted from the X-ray irradiator coincide with each other. An X-ray imaging apparatus according to any one of claims 1 to 5,
The X-ray imaging apparatus according to claim 1, wherein the arm includes a plurality of the joints. The X-ray imaging apparatus according to any one of claims 1 to 6,
A rail provided along the longitudinal direction of the top plate on the side of the top plate,
The X-ray imaging apparatus according to claim 1, wherein the arm is connected to the top plate via an arm base portion slidable along the rail. The X-ray imaging apparatus according to any one of claims 1 to 7,
An X-ray imaging apparatus comprising a grid for removing scattered X-rays from X-rays transmitted through the subject on the X-ray irradiator side of the X-ray flat panel detector.

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