JP2015047392A - X-ray tomography apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tomography apparatus capable of performing photography of a more accurate X-ray tomographic image to a region whose diagnosis has been difficult while maintaining a patient in a stable attitude.SOLUTION: In an X-ray tomographic image photographing apparatus 1, an X-ray tube movement drive part 17, an X-ray tube rotation drive part 21, and an X-ray detector movement drive part 23 incline a direction of X-rays radiated from an X-ray tube 9 with respect to a transverse direction of a top plate 11. Thereby, the X-ray tomographic image photographing apparatus 1 can acquire a suitable X-ray tomographic image for a region whose diagnosis has been difficult before. The apparatus inclines the X-ray radiation direction with respect to the transverse direction of the top plate 11 while making a subject maintain a stable attitude. That is, since the subject M maintains the stable attitude during X-ray transmission image photography, the attitude of the subject M in pictures of a series of X-ray transmission images is not displaced. Accordingly, since the X-ray tomographic image formed from the X-ray transmission images becomes clearer and more accurate, the X-ray tomographic image photographing apparatus 1 can photograph the X-ray tomographic image more suitable for the diagnosis.

Description

  The present invention sequentially irradiates a subject with X-rays from the X-ray tube while moving the X-ray tube and the X-ray detector in opposite directions with the subject interposed therebetween. By detecting transmitted X-rays with an X-ray detector and capturing projection images, and performing image reconstruction processing on the projection images, each imaging section parallel to the detection surface of the X-ray detector within the tomographic range The present invention relates to an X-ray tomography apparatus that generates tomographic images by tomosynthesis and displays those images.

  As an apparatus for acquiring a tomographic image of a subject using X-rays, there is an X-ray tomography apparatus based on an imaging technique called tomosynthesis (for example, Patent Document 1). This X-ray tomography apparatus keeps the X-ray tube and the X-ray detector facing each other, and repeats acquisition of X-ray transmission images while synchronously moving in opposite directions with the subject interposed therebetween. Based on the acquired X-ray transmission images, the X-ray tomographic image of the subject at an arbitrary cutting position is reconstructed by digital processing and displayed on a display unit such as a monitor.

  The configuration of an X-ray tomography apparatus according to a conventional example will be described with reference to FIG. A conventional X-ray tomography apparatus 100 includes an X-ray tube 101, a collimator 102, an X-ray detector 103, a column 104, a top plate 105, an imaging system drive mechanism 107, and an irradiation angle drive mechanism 109. I have. A transmission image forming unit 111 is provided at the subsequent stage of the X-ray detector 103, and a tomographic image reconstruction unit 113 is provided at the subsequent stage of the transmission image forming unit 111.

  The X-ray tube 101 irradiates the placed subject M with a cone-shaped X-ray beam 115. The X-ray detector 103 detects the X-ray beam 115 irradiated from the X-ray tube 101 and passed through the subject M, and outputs it as an X-ray detection signal. The top plate 105 places the subject M in a horizontal posture.

  The imaging system drive mechanism 107 horizontally moves the X-ray detector 103 and the support column 104 in the opposite directions to each other along the z direction shown in the drawing, that is, the body axis direction of the subject M. Accordingly, the X-ray tube 101 connected to the support column 104 and the X-ray detector 103 are synchronously moved in opposite directions with the subject M interposed therebetween while maintaining the arrangement facing each other.

  The irradiation angle drive mechanism 109 changes the irradiation angle of X-rays emitted from the X-ray tube 101 so as to be inclined with respect to the z direction. Since the X-ray irradiation angle is sequentially changed in conjunction with the horizontal movement in the z direction, the X-ray tube 101 can always irradiate the region of interest in the subject M with X-rays.

  The transmission image forming unit 111 acquires an X-ray transmission image of the subject M based on the X-ray detection signal output from the X-ray detector 103. That is, when the X-ray tube 101 sequentially irradiates X-rays, a large number of X-ray transmission images having different X-ray incident directions with respect to the region of interest are acquired. The tomographic image reconstruction unit 113 acquires an X-ray tomographic image of the subject M at a desired cutting position by reconstructing a large number of acquired X-ray transmission images.

  The principle of acquiring an X-ray tomographic image by tomosynthesis in the X-ray tomography apparatus 100 will be described with reference to FIG. For example, the reference tomographic plane Ma parallel to the top plate 105 will be described using points P and Q that are arbitrary points located on the reference tomographic plane Ma. When the X-ray tube 101 emits X-rays from the position indicated by the solid line toward the reference tomographic plane Ma, on the X-ray detection surface 103a detected by the X-ray detector 103, the points P and Q are points p1 And projected as point q1.

  The X-ray tube 101 moves along a trajectory parallel to the z direction while changing the irradiation angle of the X-ray beam 115 so that the X-ray beam 115 always irradiates the reference tomographic plane Ma. The X-ray detector 103 moves synchronously in the direction opposite to the X-ray tube 101 in accordance with the irradiation direction of the X-ray beam 115. Therefore, when the X-ray tube 101 moves from the position indicated by the solid line to the position indicated by the broken line, the X-ray detector 103 moves to the position indicated by the broken line. When the X-ray tube 101 emits X-rays from the position indicated by the broken line toward the reference tomographic plane Ma, the points P and Q located on the reference tomographic plane Ma are the points p2 and p on the X-ray detection plane 103b. Projected as point q2.

  Since the X-ray tube 101 and the X-ray detector 103 move opposite to each other in accordance with the irradiation direction of the X-ray beam 115, the positions of the points p1 and q1 on the X-ray detection surface 103a and the point p2 on the X-ray detection surface 103b. And the position of the point q2 is the same. That is, in the series of X-ray transmission images, the projection positions of the point P and the point Q all match. Therefore, as a result of the X-ray transmission image being superposed by the tomographic image acquisition unit 113, the X-ray transmission images of the points P and Q are accumulated and appear as clear points in the acquired X-ray tomographic image.

  On the other hand, the projection position on the X-ray detection surface of the point R located on the parallel cut section deviated vertically from the reference tomographic plane Ma changes according to the imaging position. That is, the point r1 projected on the X-ray detection surface 103a and the point r2 projected on the X-ray detection surface 103b are different in position on each X-ray detection surface. Accordingly, when the respective X-ray transmission images are superimposed by the tomographic image acquisition unit 113, the X-ray transmission image at the point R is dispersed and dispersed over the entire tomographic image, so that it is clear in the acquired X-ray tomographic image. I can't tie a statue. Thus, only by superimposing the X-ray transmission images, an X-ray tomographic image in which only an image located on the reference tomographic plane Ma of the subject M is clarified is acquired.

  When it is desired to obtain an X-ray tomographic image at a parallel cut section where the point R is located, a reference tomographic plane is obtained by using a shift addition method (for example, Patent Document 2) in which an X-ray transmission image is shifted by an appropriate amount in the operation direction and superimposed. An X-ray tomographic image can be reconstructed at a cutting plane parallel to Ma. As a method for reconstructing an X-ray tomographic image, there is a filter back projection method (for example, Patent Document 3) in addition to the shift addition method. In this way, dozens of continuous tomographic images can be acquired in one imaging by X-ray tomography using tomosynthesis, so that the skeleton and organs can be clearly observed while suppressing the exposure to the subject. Is possible.

JP 2006-271513 A JP 2005-305113 A JP 2004-313391 A

However, the conventional example having such a configuration has the following problems.
That is, in the conventional apparatus, there is a part where X-ray tomography is difficult for a subject in a horizontal posture. One example is the back of the spine. As shown in FIG. 11A, when X-ray 117 is irradiated to a subject M in a horizontal posture, X-ray 117 is absorbed by spine A (see symbol x in the figure). Therefore, the X-ray 117 is not irradiated to the part B corresponding to the back part of the spine A. In this case, since the image of the part B does not appear in the acquired X-ray transmission image and X-ray tomographic image, an accurate diagnosis regarding the part B cannot be performed.

  Therefore, in order to capture an X-ray transmission image in which the image of the part B is reflected, the subject M is inclined with respect to the y direction, that is, the short direction of the top 105 as shown in FIG. You have to shoot. In this case, the X-ray 117 is irradiated to the site B without being blocked by the spine A. However, on the other hand, a great stress is applied to the subject M and an unstable posture is maintained for a long time. As a result, the posture of the subject changes while taking a series of X-ray transmission images, so that the X-ray tomographic image acquired by reconstruction is likely to be an unclear and inaccurate image.

  The present invention has been made in view of such circumstances, and is suitable for more accurate diagnosis with respect to a portion that is difficult to diagnose with a conventional apparatus while maintaining the patient in a stable posture. It is an object of the present invention to provide an X-ray tomography apparatus that can capture an X-ray tomographic image.

In order to achieve such an object, the present invention has the following configuration.
That is, an X-ray tomography apparatus according to the present invention includes an X-ray source that irradiates a subject with X-rays, an X-ray detection unit that detects X-rays transmitted through the subject, the X-ray source, and the X-rays The top plate on which the subject is placed at a position sandwiched by the detection means, and the X-ray source and the X-ray detection means are opposed to each other in the longitudinal direction of the top plate with the subject interposed therebetween. An X-ray irradiation control unit for controlling the X-ray source to repeat X-ray irradiation during the counter-movement by the counter-moving unit, and X-ray irradiation by the X-ray source. Transmission image acquisition means for acquiring a transmission image based on a detection signal output from the X-ray detection means, tomographic image acquisition means for acquiring a tomographic image from a plurality of transmission images acquired by the transmission image acquisition means, The direction of X-ray irradiation from the X-ray source is set to the top plate. It is characterized in that a radiation direction tilting means for tilting with respect to longitudinal direction.

  [Operation / Effect] According to the X-ray tomography apparatus of the present invention, the irradiation direction tilting means tilts the X-ray irradiation direction with respect to the short direction of the top plate. That is, when acquiring an X-ray tomographic image by tomosynthesis, the direction of X-ray irradiation from the X-ray source to the region of interest of the subject is changed from the direction perpendicular to the horizontal plane to the lateral direction of the top plate. Tilt against.

  Thereby, the irradiated X-rays are suitably irradiated to the region of interest on the back side of the spine without being blocked by the spine or the like. Then, the X-rays applied to the region of interest are detected by the X-ray detection means and output as an X-ray detection signal. Therefore, by providing such a configuration, it becomes possible to acquire a clear and accurate X-ray tomographic image of a site that is difficult to diagnose with a conventional apparatus.

  In addition, the apparatus according to the present invention has an advantage that the X-ray irradiation direction can be changed with respect to the short direction of the top plate while maintaining a stable posture such as a supine on the subject. That is, the X-ray tomographic image is taken while the X-ray irradiation direction is inclined with respect to the lateral direction of the top plate while keeping the subject in a stable posture such as on his back. Since the subject maintains a stable posture while sequentially taking X-ray transmission images, the posture of the subject does not shift in a series of acquired X-ray transmission images. Therefore, an X-ray tomographic image formed by reconstructing X-ray transmission images is clearer and more accurate.

  In the above-described invention, the irradiation direction tilting means rotates the X-ray source around the longitudinal axis of the top plate to change the X-ray irradiation direction from the X-ray source to the short side of the top plate. It is preferable to incline with respect to the hand direction.

  [Operation / Effect] According to the above-described configuration, the X-ray source can rotate around the longitudinal axis of the top plate. Then, by rotating the X-ray source around the longitudinal axis of the top plate, the X-ray irradiation direction is configured to be inclined with respect to the short side direction of the top plate. Thereby, without changing the spatial position of the X-ray source, the X-ray irradiation direction is inclined from the direction perpendicular to the short direction of the top plate to the short direction of the top plate. Can be changed to

  In the above-described invention, it is preferable that the irradiation direction tilting unit moves the X-ray source in a short direction of the top plate.

  [Operation / Effect] According to the above-described configuration, the irradiation direction tilting means moves the X-ray source in the short direction of the top plate. In this case, the X-ray source moves from the position on the vertical line of the subject so as to move away from the subject in the short direction of the top board. Therefore, the straight line connecting the X-ray source and the region of interest is sufficiently inclined with respect to the short direction of the top board. Accordingly, the X-ray irradiation direction can be changed from the vertical direction to a direction inclined with respect to the short side direction of the top plate.

  In the above-described invention, it is preferable that the irradiation direction tilting unit moves the X-ray detection unit in a short direction of the top plate.

  [Operation and Effect] According to the above-described configuration, the irradiation direction tilting means moves the X-ray detection means in the short direction of the top plate. In this case, the X-ray detection means moves from the position on the vertical line of the subject so as to move away from the subject in the short direction of the top board. For this reason, the straight line connecting the X-ray source and the X-ray detection means is inclined with respect to the short direction of the top plate across the region of interest of the subject. Therefore, the X-ray detection means can accurately detect X-rays transmitted through the subject from an oblique direction.

  In the above-described invention, it is preferable that the X-ray source and the X-ray detection means are opposed to each other with the subject interposed therebetween and move in opposite directions in the short direction of the top plate.

  [Operation / Effect] According to the above-described configuration, the X-ray source and the X-ray detection means move in directions opposite to each other in the short direction of the top of the subject. That is, the X-ray detection means moves in the direction opposite to the movement direction of the X-ray source across the region of interest of the subject. The X-ray source and the X-ray detection means move from the position on the vertical line of the subject so as to move away from the subject in the short direction of the top plate. Therefore, the straight line connecting the X-ray source and the X-ray detection means is sufficiently inclined with respect to the short direction of the top plate across the region of interest of the subject. Therefore, the X-ray detection means can more accurately detect X-rays transmitted through the subject from an oblique direction.

  According to the X-ray tomography apparatus according to the present invention, the X-ray irradiation direction is inclined with respect to the lateral direction of the top board. By providing such a configuration, it is possible to obtain a suitable X-ray tomographic image for a site that is difficult to diagnose with a conventional apparatus. In the apparatus according to the present invention, an X-ray tomographic image is taken while the X-ray irradiation direction is inclined with respect to the short direction of the top board while the subject is in a stable posture. Since the subject maintains a stable posture while sequentially capturing X-ray transmission images, the posture of the subject does not shift in a series of acquired X-ray transmission images. Accordingly, X-ray tomographic images acquired from a plurality of X-ray transmission images are clearer and more accurate. Further, since imaging is performed while maintaining a stable posture, an X-ray tomographic image suitable for diagnosis can be acquired without applying stress to the subject even when imaging is performed for a long time.

1 is a perspective view illustrating a schematic configuration of an X-ray tomography apparatus according to an embodiment. It is a functional block diagram of the X-ray tomography apparatus which concerns on an Example. In the X-ray tomography apparatus which concerns on an Example, it is a side view explaining the outline of the mechanism which controls the movement of the imaging system with respect to ay direction. In the X-ray tomography apparatus according to the embodiment, (a) is a schematic diagram for explaining the configuration of an X-ray tube movement drive unit, and (b) is an X-ray detector movement drive unit. (A) is a flowchart explaining the operation | movement which concerns on an Example, (b) is a side view which shows the structure of the X-ray tomography apparatus in step S1 in an Example. In an Example, it is a side view which shows the state of the X-ray tomography apparatus in step S2. It is a front view explaining the operation | movement which concerns on imaging | photography of an X-ray transmission image in the X-ray tomography apparatus which concerns on an Example. It is a side view for demonstrating the effect acquired in the X-ray tomography apparatus which concerns on an Example compared with a prior art example, (a), (b) is a prior art example, (c) is an Example. It is a front view explaining schematic structure of the X-ray tomography apparatus which concerns on a prior art example. It is a front view explaining the operation | movement which concerns on imaging | photography of an X-ray transmission image in the X-ray tomography apparatus which concerns on a prior art example. (A), (b) is a side view explaining the problem which generate | occur | produces about the X-ray tomography apparatus concerning a prior art example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view illustrating a schematic configuration of an X-ray tomography apparatus according to the embodiment, and FIG. 2 is a functional block diagram of the X-ray tomography apparatus according to the embodiment.

<Description of overall configuration>
As shown in FIG. 1, the X-ray tomography apparatus 1 according to the embodiment includes a base 3, a column 5, an X-ray tube support unit 7, an X-ray tube 9, a top plate 11, and an X-ray detection. And a collimator 15. One end of an X-ray tube support portion 7 is connected to the support column 5 so as to be able to advance and retreat, and an X-ray tube 9 for irradiating X-rays is provided at the other end of the X-ray tube support portion 7. Below the X-ray tube 9 is provided a collimator 15 that collimates the irradiated X-rays in a cone shape that is a pyramid. The X-ray tube 9 and the X-ray detector 13 form an imaging system that captures an X-ray transmission image.

  The top plate 11 is supported by the base 3 and places the subject M in a horizontal posture. The X-ray detector 13 is provided below the top plate 11, detects X-rays transmitted through the subject M from the X-ray tube 9, detects them, converts them into electrical signals, and outputs them as X-ray detection signals. . As the X-ray detector 13, a flat panel detector (FPD: Flat Panel Detector) is used.

  The X-ray tube 9 corresponds to the X-ray source in the present invention, and the X-ray detector 13 corresponds to the X-ray detection means in the present invention.

  As shown in FIG. 2, a z-direction counter movement drive unit 16 is connected to the column 5, the X-ray tube 9, and the X-ray detector 13. The column 5, the X-ray tube 9, and the X-ray detector 13 are configured to face each other along a trajectory parallel to the z direction, that is, the longitudinal direction of the top plate 11, under the control of the z direction facing movement driving unit 16. ing. The X-ray tube support unit 7, the X-ray tube 9, and the X-ray detector 13 have an X-ray tube movement driving unit 17, an X-ray tube rotation driving unit 21, and an X-ray detector movement driving unit as y-direction opposed movement driving units. 23 are connected to each other.

  An X-ray tube moving drive unit 17 is connected to the X-ray tube support unit 7. The X-ray tube support unit 7 is configured to horizontally move in the y direction, that is, the short direction of the top plate 11 on which the subject M is placed by the X-ray tube movement driving unit 17.

  An X-ray irradiation control unit 19 is connected to the X-ray tube 9. And based on the signal output by the X-ray irradiation control part 19, it is comprised so that the X-ray dose irradiated from the X-ray tube 9 and the timing which irradiates an X-ray may be controlled.

  Further, an X-ray tube rotation drive unit 21 is connected to the X-ray tube 9. The X-ray tube rotation drive unit 21 is configured so that the X-ray tube 9 can be driven to rotate around the z-axis. Therefore, the X-ray tube rotation drive unit 21 can control the X-ray tube 9 to change the X-ray irradiation angle with respect to the y direction without changing its own spatial position.

  An X-ray detector movement drive unit 23 is connected to the X-ray detector 13, and the X-ray detector 13 is configured to horizontally move in the y direction by the X-ray detector movement drive unit 23. Therefore, the X-ray detector 13 is moved to a position where the irradiated X-rays can be suitably received according to the position of the X-ray tube 9 and the X-ray irradiation angle. Since the X-ray detector 13 moved to a suitable position receives X-rays on the entire surface, the X-rays can be efficiently converted into electric signals and output as X-ray detection signals.

  Further, a transmission image forming unit 25 is provided in the subsequent stage of the X-ray detector 13, and a tomographic image reconstruction unit 27 is provided in the subsequent stage of the transmission image forming unit 25. The transmission image forming unit 25 forms an X-ray transmission image of the subject M based on the X-ray detection signal output from the X-ray detector 13. The tomographic image reconstruction unit 27 forms an X-ray tomographic image by reconstructing a plurality of X-ray transmission images formed by the transmission image forming unit 25.

  Further, the X-ray tomography apparatus 1 includes a display unit 29 and a main control unit 31. The tomographic image reconstruction unit 27 reconstructs image information of the X-ray transmission image and forms an X-ray tomographic image of the subject M at a desired cutting position. The display unit 29 displays the X-ray tomographic image formed by the tomographic image reconstruction unit 27. The z-direction opposed movement drive unit 16, the X-ray tube movement drive unit 17, the X-ray irradiation control unit 19, the X-ray tube rotation drive unit 21, the X-ray detector movement drive unit 23, and the transmission image forming unit 25 are the main control unit. 31 is controlled in an integrated manner.

  The z-direction counter movement drive unit 16 corresponds to the counter movement unit in the present invention, and the X-ray irradiation control unit 19 corresponds to the X-ray irradiation control unit in the present invention. The X-ray tube movement drive unit 17, the X-ray tube rotation drive unit 21, and the X-ray detector movement drive unit 23 correspond to the irradiation direction tilting means in the present invention. The transmission image forming unit 25 corresponds to the transmission image acquisition unit in the present invention, and the tomographic image reconstruction unit 27 corresponds to the tomographic image acquisition unit in the present invention.

  Next, a mechanism for controlling the movement of the imaging system in the y direction will be described with reference to the drawings. FIG. 3 is a right side view of the X-ray tomography apparatus 1.

  Of the y-direction opposing movement drive units, the X-ray tube movement drive unit 17 is provided on the column 5 as shown in FIG. As an example, the X-ray tube movement drive unit 17 has a configuration including a motor 17a and a screw rod 17b as shown in FIG. The X-ray tube support portion 7 is provided with an X-ray tube 9 on one end side, and the other end side is screwed to the screw rod 17b. The screw rod 17b extends in the y direction, and the screw rod 17b is rotated in both forward and reverse directions by the motor 17a. For example, when the motor 17a is rotated in the forward direction, the X-ray tube 9 together with the X-ray tube support portion 7 moves horizontally to the left in the figure with respect to the y direction, as shown by the one-dot chain line in FIG. When the motor 17a is rotated in the reverse direction, the X-ray tube 9 moves horizontally to the right side of the drawing as shown by the two-dot chain line in FIG.

  The mechanism in which the X-ray detector movement drive unit 23 controls the movement of the X-ray detector 13 in the y direction among the y direction opposite movement drive units is the same as this. That is, the X-ray detector movement drive unit 23 is provided below the top plate 11 as shown in FIG. As an example, the X-ray detector movement drive unit 23 has a configuration including a motor 23a and a screw rod 23b as shown in FIG. 4B. The X-ray detector 13 is mounted on a mounting plate 33, and the mounting plate 33 is screwed to the screw rod 23b. Therefore, when the motor 23a is rotated in the forward direction, the X-ray detector 13 moves horizontally to the left side of the figure as shown by the one-dot chain line in FIG. Then, when the motor 23a is rotated in the reverse direction, the X-ray detector 13 moves horizontally to the right side of the figure as shown by the two-dot chain line in FIG.

  As shown in FIG. 3, the x-ray tube rotation drive unit 21 of the y-direction counter movement drive unit is attached to the x-ray tube 9, and a motor is used as an example. The X-ray tube rotation drive unit 21 has a configuration that can rotate forward and backward around the z-axis. Therefore, the X-ray tube 9 can rotate around the z-axis according to the rotation direction of the X-ray tube rotation drive unit 21.

<Operation of X-ray tomography apparatus>
Next, the operation of the X-ray tomography apparatus 1 will be described with reference to the drawings. FIG. 5A is a flowchart for explaining the operation according to the embodiment. As shown in FIG. 3, in the X-ray tomography apparatus 1, the subject M is placed on the top 11 in a supine posture, and the imaging system comprising the X-ray tube 9 and the X-ray detector 13 is It is assumed that it is located on the vertical line of the region of interest S of the sample M.

Step S1 (determination of the tilt angle with respect to the y direction)
First, as shown in FIG. 5B, the angle at which X-rays are irradiated is determined with respect to the short direction of the top plate 11, that is, the direction indicated by the symbol y. As described above, the imaging system is located on the vertical line of the region of interest S of the subject M, that is, at each location indicated by the solid line. If X-rays are irradiated toward the region of interest S in this state, the X-rays from the X-ray tube 9 toward the region of interest S may be blocked by the spine T, and the region of interest S may not be irradiated with X-rays.

  Therefore, in order to obtain suitable image information related to the region of interest S without being blocked by the spine T, the X-ray is irradiated from a direction sufficiently inclined with respect to the y direction from the vertical direction. For example, when X-rays are irradiated toward the site of interest S from a direction inclined by an angle θ with respect to the y direction from the vertical direction, the site of interest S is irradiated without being blocked by the spine T. In this case, the X-ray tube 9 irradiates the region of interest S with X-rays from the position indicated by the two-dot chain line in FIG.

  In order for the X-ray detector 13 to receive X-rays preferably, it is preferable that the X-ray detector 13 is always moved to a position facing the X-ray tube 9 across the region of interest S. Therefore, when the X-ray tube 9 emits X-rays from the position of the two-dot chain line, the X-ray detector 13 is moved from the position indicated by the solid line to the position indicated by the two-dot chain line to receive the X-ray. Become. The position of the imaging system in the y direction and the angle θ in the X-ray transmission image capturing process are determined in this way.

Step S2 (moving the imaging system opposite in the y direction, rotating the X-ray tube around the z axis)
When the inclination angle of the imaging system with respect to the y direction is determined, a signal is output from the main control unit 31 to the X-ray tube movement drive unit 17. Based on the output signal, the X-ray tube movement drive unit 17 moves the X-ray tube support unit 7 straight along a linear trajectory parallel to the y direction, as shown in FIG. Since the X-ray tube 9 is provided at the tip of the X-ray tube support portion 7, the X-ray tube 9 is horizontally moved from the broken line position to the solid line position as the X-ray tube support portion 7 moves.

  At this time, a signal is output from the main control unit 31 to the X-ray detector movement drive unit 23 synchronously. The X-ray detector movement driving unit 23 moves the X-ray detector 13 straight so as to face the X-ray tube 9 based on the output signal. That is, the X-ray detector 13 and the X-ray tube 9 go straight in opposite directions and are horizontally moved from the position of the broken line to the position of the solid line.

  Further, at this time, a signal is output from the main control unit 31 to the X-ray tube rotation driving unit 21 synchronously. The X-ray tube rotation drive unit 21 rotates the X-ray tube 9 around the z-axis as shown in FIG. 6 based on the output signal. At this time, rotation control of the X-ray tube 9 is performed so that the center 35a of the X-ray beam 35 irradiated from the X-ray tube 9 indicated by a solid line is incident on the region of interest S. In this case, the incident angle of the center 35a of the X-ray beam 35 is inclined by an angle θ with respect to the vertical line. Therefore, the plane Mb, which is inclined from the horizontal plane Ma by the angle θ in the y direction, becomes the reference cross section. By completing the steps S1 to S2 described above, preparation for acquiring an X-ray transmission image is completed for the imaging surface inclined in the y direction.

Step S3 (formation of X-ray transmission image)
When preparation for acquiring an X-ray transmission image is completed, a signal is output from the main control unit 31 to the z-direction counter movement drive unit 16 and the X-ray irradiation control unit 19.

  Based on the signal output from the main control unit 31, the z-direction opposite movement drive unit 16 moves the column 5, the X-ray tube 9, and the X-ray detector 13 in the z direction shown in FIG. 7, that is, the body axis direction of the subject M. To move along. At this time, the movement of the X-ray detector 13 is controlled so that the central axis 35 a of the X-ray beam 35 emitted from the X-ray tube 9 passes through the center of the X-ray detector 13. That is, the X-ray tube 9 and the X-ray detector 13 are horizontally moved from the position indicated by the solid line to the position indicated by the broken line synchronously in the opposite directions with the subject M interposed therebetween while maintaining the arrangement facing each other. To do.

  At this time, rotation control of the X-ray tube 9 is performed so that the central axis 35a of the X-ray beam 35 emitted from the X-ray tube 9 always passes through the region of interest S. That is, while the support column 5 moves horizontally in the z direction, the X-ray irradiation angle with respect to the z direction of the X-ray tube 9 is sequentially changed. Since the X-ray tube 9 is not rotated in the y direction after the start of step S3, the X-ray tube 9 is maintained in an inclined state by an angle θ with respect to the y direction.

  Based on the output signal, the X-ray irradiation control unit 19 irradiates the cone-shaped X-ray beam 35 from the horizontally moving X-ray tube 9. The irradiated X-ray beam 35 passes through the subject M and is detected by the X-ray detector 13. The X-ray detector 13 that has detected the X-ray outputs an X-ray detection signal, and the transmission image forming unit 25 forms an X-ray transmission image based on the X-ray detection signal.

  In this way, the X-ray beam 35 is intermittently irradiated from the X-ray tube 9 while the imaging system is horizontally moved from the position indicated by the solid line to the position indicated by the broken line. The number of times of irradiation of the X-ray beam 35 is several tens of times or more, for example, 74 times. Since an X-ray transmission image is taken every time X-rays are irradiated, a series of X-ray transmission images taken from different directions with respect to the region of interest S are acquired while the imaging system is moved horizontally once. The When the acquisition of a series of X-ray transmission images is completed, the acquired X-ray transmission image data is sent from the transmission image forming unit 25 to the tomographic image reconstruction unit 27.

Step S4 (Reconstruction of X-ray tomographic image)
When a series of X-ray transmission images are acquired, the tomographic image reconstruction unit 27 reconstructs image information relating to the series of X-ray transmission images. By reconstructing, X-ray tomographic image data at an arbitrary cut surface parallel to the reference cut surface Mb can be acquired. The display unit 29 displays the X-ray tomographic image data acquired by the tomographic image reconstruction unit 27.

<Effects of Configuration of Example>
Here, the effect obtained based on the structure which concerns on an Example is demonstrated using FIG.

  As shown in FIG. 8A, in the X-ray tomography apparatus having the conventional configuration, the direction of the central axis 35a of the X-ray beam irradiated from the X-ray tube 9 to the subject M is the y direction. It is always perpendicular to it. Therefore, the reference cut surface Ma is always parallel to the horizontal plane. The X-ray tomographic image acquired by the X-ray tomography apparatus is an image relating to an arbitrary plane parallel to the reference cut surface Ma. Therefore, in the X-ray tomography apparatus according to the conventional example, only an X-ray tomographic image having a plane parallel to the horizontal plane, for example, the plane Ma1 and the plane Ma2 can be acquired.

  In this case, there is a site that is difficult to diagnose by X-ray tomography, and an example of this is the back of the spine. The spine is an organ located parallel to the z direction, that is, the height direction of the subject M. X-ray transmission images are taken while the imaging system is horizontally moved in the z direction. Therefore, as shown in FIG. 8A, in all radiographic image capturing, the part B corresponding to the back of the spine is aligned with the spine A and the X-ray tube 9 on the vertical line. In this case, the X-rays 37 from the X-ray tube 9 toward the site B are absorbed by the spine A, so that the site B is not irradiated with X-rays (see symbol x in the figure). As a result, since the X-ray detection signal relating to the part B is not output from the X-ray detector 13, even if an X-ray tomographic image is acquired for the cut surface Ma2 including the part B, the image of the part B does not appear in the tomographic image. .

  In the X-ray tomography apparatus according to the conventional example, in order to diagnose the region B, as shown in FIG. 8B, imaging must be performed while the subject M is inclined with respect to the y direction. In this case, the X-ray 37 irradiated from the X-ray tube 9 to the site B is not blocked by the spine A. As a result, since an X-ray tomographic image in which an image of the part B is reflected is acquired, the part B can be diagnosed by the X-ray tomographic image. However, since the subject M is kept in an unstable tilt posture for a long time, the posture of the subject M easily shifts while a series of X-ray transmission images are taken. If the posture of the subject M shown in each X-ray transmission image is shifted, the reconstructed X-ray tomographic image becomes unclear and inaccurate. Therefore, it is difficult for an apparatus according to the conventional configuration to acquire an X-ray tomographic image showing clear and accurate information about the part B.

  On the other hand, in the X-ray tomography apparatus according to the present invention, as shown in FIG. 8C, the X-ray irradiation angle on the subject M is changed from the vertical direction to the y direction prior to the X-ray transmission image capturing. Tilt by an angle θ. As the X-ray irradiation angle is inclined by the angle θ, the reference cut surface is also inclined by the angle θ in the y direction from the horizontal plane. That is, the plane Mb inclined by the angle θ from the horizontal plane Ma is the reference cut surface. The X-ray tomographic image acquired by the X-ray tomography apparatus is an image relating to an arbitrary plane parallel to the reference cutting plane Mb. Therefore, the imaging apparatus according to the present invention can acquire an X-ray tomographic image having a plane inclined with respect to the y direction, for example, the plane Mb1 and the plane Mb2 as a cutting plane.

  In the X-ray tomography apparatus according to the embodiment of the present invention, the imaging system is moved oppositely in the y direction in order to tilt the X-ray irradiation angle with respect to the y direction from the vertical direction. Therefore, when the X-ray transmission image is taken, the positions of the site B, the spine A, and the X-ray tube 9 are not aligned. That is, since the X-rays 37 irradiated from the X-ray tube 9 to the site B are not blocked by the spine A, an X-ray tomographic image in which the image of the site B is appropriately reflected can be acquired.

  In addition, in the X-ray tomography apparatus according to the embodiment of the present invention, the part B can be suitably imaged in a horizontal posture without inclining the subject M with respect to the y direction from the vertical direction. That is, since a series of X-ray transmission images are taken while maintaining a stable posture on the subject M, the posture of the subject M does not shift during the photographing. Therefore, in the X-ray tomography apparatus according to the present invention, an X-ray tomographic image in which the image of the site B is reflected more clearly and accurately can be acquired and used for diagnosis. Such an X-ray tomographic image is particularly useful for imaging and diagnosis of posterior longitudinal ligament ossification (OPLL), for example.

  In addition, since X-ray tomographic imaging is performed with the subject M in a stable posture, stress applied to the subject during X-ray tomographic imaging can be suppressed, and long-time imaging can be suitably performed. . As described above, with the X-ray tomography apparatus according to the present invention, it is possible to obtain a more suitable X-ray tomographic image for a human body structure, which has been difficult to diagnose in the past, and use it for diagnosis.

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

  (1) Although the motor and the screw rod are used as the X-ray tube movement drive unit 17 and the X-ray detector movement drive unit 23 in the above-described embodiment, the present invention is not limited to this. For example, a mechanism that can move the object bidirectionally, such as a rack and pinion, may be used.

  (2) In the above-described embodiment, the X-ray tomographic image is taken with the subject M in a horizontal posture, but the present invention is not limited to this. That is, imaging may be performed with the subject M in a standing posture. In this case, the z direction, that is, the body axis direction of the subject M is parallel to the vertical direction.

  (3) In the above-described embodiment, the X-ray detector 13 is displaced in the opposite y direction in synchronization with the displacement of the X-ray tube 9 in the y direction. However, when the X-ray detector 13 has a sufficient width with respect to the y direction, the X-ray detector 13 does not have to be displaced in the y direction.

  (4) In the above-described embodiment, as a method for acquiring an X-ray tomographic image from an X-ray transmission image, a method for reconstructing an X-ray fluoroscopic image, that is, a shift addition method is used. Instead of the shift addition method, a filter back projection method or a successive approximation method may be used.

  (5) In the above-described embodiments, the medical device is used. However, the present invention can also be applied to industrial and nuclear devices.

DESCRIPTION OF SYMBOLS 1 ... X-ray tomography apparatus 7 ... X-ray tube support part 9 ... X-ray tube (X-ray source)
13 ... X-ray detector (X-ray detection means)
16 ... z-direction opposed movement drive unit (opposite moving means)
DESCRIPTION OF SYMBOLS 17 ... X-ray tube movement drive part 21 ... X-ray tube rotation drive part 23 ... X-ray detector movement drive part 25 ... Transmission image formation part (Transmission image acquisition means)
27 ... Tomographic image reconstruction unit (tomographic image acquisition means)
M: Subject S: Region of interest y: Short direction of the top plate z: Longitudinal direction of the top plate (body axis direction of the subject)

Claims (5)

An X-ray source for irradiating the subject with X-rays;
X-ray detection means for detecting X-rays transmitted through the subject;
A top plate for placing a subject at a position between the X-ray source and the X-ray detection means;
Opposing movement means for moving the X-ray source and the X-ray detection means opposite to each other in the longitudinal direction of the top plate in a state where the X-ray source and the X-ray detection means are opposed to each other,
X-ray irradiation control means for controlling the X-ray source to repeat X-ray irradiation during the opposing movement by the opposing movement means;
Transmission image acquisition means for acquiring a transmission image based on a detection signal output by the X-ray detection means for each X-ray irradiation by the X-ray source;
A tomographic image acquisition unit for acquiring a tomographic image from a plurality of transmission images acquired by the transmission image acquisition unit;
An X-ray tomography apparatus comprising irradiation direction tilting means for tilting an irradiation direction of X-rays irradiated from the X-ray source with respect to a short direction of the top plate. The X-ray tomography apparatus according to claim 1,
The irradiation direction tilting means rotates the X-ray source around the longitudinal axis of the top plate and tilts the X-ray irradiation direction from the X-ray source with respect to the short direction of the top plate. An X-ray tomography apparatus characterized in that: The X-ray tomography apparatus according to claim 2,
The X-ray tomography apparatus according to claim 1, wherein the irradiation direction tilting means moves the X-ray source in a short direction of the top plate. The X-ray tomography apparatus according to any one of claims 1 to 3,
The X-ray tomography apparatus according to claim 1, wherein the irradiation direction tilting means moves the X-ray detection means in a lateral direction of the top plate. The X-ray tomography apparatus according to claim 4,
The X-ray tomography apparatus, wherein the X-ray source and the X-ray detection means are opposed to each other with a subject interposed therebetween and move in opposite directions in the short direction of the top plate.

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