JP6165826B2 - X-ray imaging apparatus, image processing apparatus, and X-ray imaging method - Google Patents

Description

  The present invention relates to X-ray imaging technology.

  Conventionally, CT imaging (Computed Tomography) using an X-ray imaging apparatus has been performed for the purpose of medical diagnosis or nondestructive inspection. Further, in an X-ray imaging apparatus, multi-energy scanning is performed in which the same part of a subject is imaged using a plurality of X-rays having different X-ray energy distributions (for example, Patent Document 1).

  According to this multi-energy scan, it is possible to obtain tomographic images corresponding to X-rays having a plurality of energy distribution characteristics different from each other on the same tomographic plane of the same part of the subject. With respect to these tomographic images having different energy distribution characteristics, for example, an image of a specific part can be extracted by taking a difference.

  In the X-ray CT imaging apparatus described in Patent Document 1, a subject is placed between an X-ray tube that is a radiation source and an X-ray detector that is a detection means for detecting radiation. In this state, the X-ray tube and the X-ray detector are rotated 360 degrees around the rotation axis set at the center of the CT imaging region. Between the X-ray tube and the subject, two types of filters that make the energy distribution of transmitted X-rays different from each other are arranged. For this reason, the subject is simultaneously irradiated with X-rays having different energy distributions on the left and right.

  In addition, in a helical scan type X-ray CT apparatus, a technique for performing dual energy scan by continuously arranging two detectors having different energy characteristics in the slice direction is already known (Patent Document 2).

JP 2008-54831 A JP-A-6-296607

  However, in the case of the X-ray CT imaging apparatus described in Patent Document 1, X-ray scattering occurs at the boundary between two types of filters. Since there is a considerable distance between the two types of filters and the X-ray detector, scattered X-rays are incident on a position away from the position where they should be incident. As a result, the projection image obtained may be unclear.

  In Patent Document 2, the two detectors include two scintillators having different thicknesses, or two filters having different X-ray absorption rate, thickness, shape, and material. The energy characteristics are different. Then, X-rays scattered at the boundary portion between the two filters or the two scintillators are concentrated and incident on a specific position of each detector. Then, at the incident position of scattered X-rays at the detector, there is a possibility that X-rays that have passed through the imaging region that should be detected cannot be detected.

  Therefore, an object of the present invention is to provide a technique for reducing the influence of X-ray scattering in projection image data acquired in a multi-energy scan.

In order to solve the above-described problem, a first aspect includes an X-ray generation unit including an X-ray generator that generates an X-ray beam, and the X-ray beam irradiated from the X-ray generation unit and transmitted through the subject. An X-ray detection unit including a two-dimensional X-ray detector that detects and detects light, a support unit that supports the X-ray generation unit and the X-ray detection unit in an opposing state, the X-ray generation unit, and the A moving mechanism for rotating the support unit relative to the subject with the X-ray detection unit sandwiched between the subject, and between the subject in the X-ray beam path and the two-dimensional X-ray detector An energy conversion unit in which a first part and a second part having different energy distribution conversion characteristics of the X-ray beam are arranged in a two-dimensional manner; and in X-ray imaging, the energy during the turning of the support unit the conversion unit, so as to cross the X-ray beam Kita Tsu along the detection surface of the two-dimensional X-ray detector, and a energy conversion unit moving mechanism for moving the moving direction or the opposite direction of the two-dimensional X-ray detector.
According to a second aspect, an X-ray generator composed of an X-ray generator that generates an X-ray beam, and the X-ray beam irradiated from the X-ray generator and transmitted through the subject are received and detected. An X-ray detector provided with a dimensional X-ray detector, a support unit that supports the X-ray generator and the X-ray detector while maintaining an opposed state, the X-ray generator and the X-ray detector A moving mechanism for rotating the support relative to the subject with the subject sandwiched between the subject, and the subject in the path of the X-ray beam and the two-dimensional X-ray detector; An energy conversion unit in which a first part and a second part having different conversion characteristics of the energy distribution of the beam are two-dimensionally arranged; and, in X-ray imaging, the energy conversion unit is rotated during rotation of the support unit. The two-dimensional X-ray detector so as to cross the beam Along the detection plane, and a energy conversion unit moving mechanism for moving in a direction intersecting with the moving direction of the two-dimensional X-ray detector.

In addition, a third aspect is the X-ray imaging apparatus according to the first or second aspect, in which the energy conversion unit has a filter in the first part and does not have a filter in the second part. Contains a filter construct.

According to a fourth aspect, in the X-ray imaging apparatus according to the first or second aspect, the energy conversion unit has a first filter in the first part, and the conversion characteristic is in the second part. A second filter arrangement having a second filter different from the first filter;

According to a fifth aspect, in the X-ray imaging apparatus according to any one of the first to fourth aspects, the energy conversion unit moving mechanism is a motor as a drive source for moving the energy conversion unit; And a transmission portion for transmitting the movement of the motor.

Also, aspects of the sixth, in the X-ray imaging apparatus according to the first embodiment, the direction parallel to the axial direction of the pivot axis the support portion is pivoted to the z-direction, perpendicular to the z-direction, the X-ray When the direction in which the generation unit and the X-ray detection unit face each other is the y direction, and the direction orthogonal to the z direction and the y direction is the x direction, the energy conversion unit moving mechanism moves the energy conversion unit to the second direction. The position is between the dimensional X-ray detector and the subject and is moved in the x direction .

According to a seventh aspect, in the X-ray imaging apparatus according to the sixth aspect, the X-ray imaging performed by the X-ray imaging apparatus is CT imaging, and the first portion and the second portion are striped patterns. Are arranged in a shape.

According to an eighth aspect, in the X-ray imaging apparatus according to the sixth aspect, the X-ray imaging performed by the X-ray imaging apparatus is CT imaging, and the first part and the second part are in a checkered pattern. Is arranged.

According to a ninth aspect, in the X-ray imaging apparatus according to the seventh or eighth aspect, the energy conversion unit moving mechanism is disposed in a housing of the X-ray detection unit.

Further, a tenth aspect, in the X-ray imaging apparatus according to the eighth aspect, wherein the energy conversion unit, to the dynamic shift Te the housing smell of the X-ray detector.

  In addition, an eleventh aspect further includes an X-ray restriction unit for restricting X-rays emitted from the X-ray generator in the X-ray imaging apparatus according to any one of the first to tenth aspects. The X-ray is formed into an X-ray cone beam by the X-ray restricting unit.

  The twelfth aspect is the X-ray imaging apparatus according to the eleventh aspect, in which the X-ray imaging performed by the X-ray imaging apparatus is CT imaging, and the energy conversion unit moving mechanism is configured by the energy conversion unit. Is retracted from the position where the X-ray cone beam transmitted through the CT imaging region is incident.

  The thirteenth aspect is the X-ray imaging apparatus according to the eleventh or twelfth aspect, wherein panoramic X-ray imaging or cephalometric imaging is performed using the X-ray slit beam formed by the X-ray restricting unit. To do.

Further, the fourteenth aspect is the X-ray imaging apparatus according to the second aspect, wherein the energy conversion unit moving mechanism moves the energy conversion unit during CT imaging, so that the support unit is rotated halfway. While performing the turning with the fan angle of the X-ray beam, at least one of the first part and the second part is displaced by the width in the intersecting direction of the one part, and the support part is further halved. While performing the rotation by adding the fan angle of the X-ray beam to the rotation, the one is further displaced by the width in the intersecting direction, and the other of the first part and the second part is the X-ray. X-rays of the remaining part other than the part incident on the one of the beams are received.

  Further, in the X-ray imaging apparatus according to the tenth aspect, the fifteenth aspect is that during the CT imaging, the energy conversion unit moving mechanism moves the energy conversion unit, so that the support unit is rotated. The first part is displaced by a width in the moving direction of the X-ray detector, the second part is a direction in which the first part is displaced simultaneously with the displacement of the first part, and the displacement amount of the first part It is displaced by the amount of displacement that matches.

  A sixteenth aspect is an image processing apparatus that processes image data acquired by the X-ray imaging apparatus according to any one of the first to fifteenth aspects, wherein the first part of the energy conversion unit And image data obtained by passing through or passing through each of the second parts and detecting the X-ray beam with the two-dimensional X-ray detector, and obtaining X-ray images corresponding to the respective energy distribution characteristics. An image processing unit to be generated.

  According to a seventeenth aspect, in the image processing device according to the sixteenth aspect, the image processing unit obtains an image of a difference between the image data corresponding to each energy distribution characteristic by calculation.

An eighteenth aspect is an X-ray imaging method in which an X-ray generator that generates an X-ray beam and a two-dimensional X-ray detector that detects an X-ray beam transmitted through a subject are opposed to each other. A rotation step of rotating around the subject; and during the rotation step, the X-ray beam energy distribution is interposed between the subject in the X-ray beam path and the two-dimensional X-ray detector. the energy conversion unit in which the first and second portions of the conversion characteristics are different, which are arranged in a two-dimensional, and Tsu along the detection surface of the two-dimensional X-ray detector so as to cross the X-ray beam, An energy conversion unit moving step of moving the two-dimensional X-ray detector in the moving direction or in the opposite direction.
According to a nineteenth aspect, in the X-ray imaging apparatus according to any one of the first to fifteenth aspects, the energy conversion unit movement mechanism is configured such that the movement amount of the energy conversion unit is swung by the movement mechanism. The energy conversion unit is moved so as to be proportional to the amount of change in the rotation angle of the support unit.

According to the first and second aspects, during the X-ray imaging, the boundary between the first part and the second part of the energy conversion unit is moved by moving the energy conversion unit so as to cross the X-ray beam. Can do. For this reason, it can reduce that the X-rays which entered and scattered to the said boundary part concentrate and inject into the specific position of a two-dimensional X-ray detector. Therefore, the influence of scattered X-rays of X-rays in the projection data can be reduced. Thus, for example, when two types of CT images (tomographic images) corresponding to the energy distribution characteristics of the X-rays that have passed through the first part and the second part of the energy conversion unit are obtained by reconstruction, the influence of the scattered X-rays It can be made small and clear, and the discrimination ability of X-ray energy can be improved.

In addition, according to the third aspect, by causing X-rays to enter each of the first part having the filter and the second part not having the filter, the X-rays have different energy distribution characteristics from each other. Can be converted to a line.

Moreover, according to the 4th aspect, by making an X-ray inject into each of a 1st filter and a 2nd filter, each X-ray can be converted into an X-ray with the energy distribution characteristic which is mutually different.

Moreover, according to the 5th aspect, an energy conversion part can be easily moved with a motor and a conduction part.

According to the sixth aspect, since the energy conversion unit can be disposed at a position relatively close to the two-dimensional X-ray detector, the boundary portion between the first portion and the second portion is brought closer to the two-dimensional X-ray detector. be able to. As a result, it is possible to reduce the incidence of X-rays scattered at the boundary portion at a position far from the original incident position in the two-dimensional X-ray detector.

  Moreover, according to the 11th aspect, a cone beam can be formed by the X-ray control part. For this reason, CT imaging can be performed using a cone beam.

  According to the twelfth aspect, CT imaging without using a filter can be performed by retracting the energy conversion unit from the position where the cone beam is incident.

  According to the thirteenth aspect, the X-ray slit beam can be formed by the X-ray restricting portion. For this reason, panoramic X-ray imaging and cephalo imaging can be performed using an X-ray slit beam.

1 is a schematic perspective view showing an X-ray imaging apparatus according to a first embodiment. It is a front view which shows the cephalostat applicable to an X-ray imaging apparatus. It is a block diagram which shows the structure of an X-ray imaging apparatus. It is a schematic perspective view for demonstrating CT imaging | photography of the jaw part by a main-body part. It is the schematic plan view which looked at the main-body part which performs CT imaging | photography of the jaw part in a to-be-photographed head along the rotation-axis direction of a X-ray generator and a two-dimensional X-ray detector from the to-be-photographed head side. FIG. 3 is a schematic plan view for explaining a first CT imaging example in the X-ray imaging apparatus according to the first embodiment. It is a figure which shows typically the sinogram obtained in the 1st CT imaging example shown in FIG. It is a schematic plan view which shows the modification of the 1st CT imaging example shown in FIG. It is a schematic plan view for demonstrating the 2nd CT imaging example in the X-ray imaging apparatus which concerns on 1st Embodiment. It is a figure which shows typically the sinogram obtained in the 2nd CT imaging example shown in FIG. It is a schematic plan view for demonstrating the 3rd CT imaging example in the X-ray imaging apparatus which concerns on 2nd Embodiment. It is a schematic plan view for demonstrating the 3rd CT imaging example in the X-ray imaging apparatus 100a which concerns on 2nd Embodiment. It is a figure which shows typically the sinogram obtained by the 3rd CT imaging example shown in FIG.11 and FIG.12. It is a figure which shows typically the sinogram which reorganized the sinogram shown in FIG. It is a figure which shows typically the sinogram for demonstrating the 4th CT imaging example in the X-ray imaging apparatus which concerns on 2nd Embodiment. It is a schematic plan view which shows the 5th CT imaging example in the X-ray imaging apparatus which concerns on 2nd Embodiment. It is a schematic plan view which shows the 5th CT imaging example in the X-ray imaging apparatus which concerns on 2nd Embodiment. It is a figure which shows typically the sinogram obtained by the 5th CT imaging example shown in FIG.16 and FIG.17. It is a schematic plan view for demonstrating the 6th CT imaging example in the X-ray imaging apparatus which concerns on 3rd Embodiment. It is a schematic perspective view which shows the X-ray imaging apparatus which concerns on 4th Embodiment. It is a schematic front view which shows the energy conversion part which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the component described in this embodiment is an illustration to the last, and is not a thing of the meaning which limits the scope of the present invention only to them. In the drawings, the size and number of each part may be exaggerated or simplified as necessary for easy understanding.

<1. First Embodiment>
FIG. 1 is a schematic perspective view showing an X-ray imaging apparatus 100 according to the first embodiment. The X-ray imaging apparatus 100 performs X-ray imaging (for example, CT imaging), collects projection image data, processes the projection image data collected in the main body 1, and generates various images. The information processing apparatus 8 is roughly classified. Note that the X-ray imaging apparatus 100 is configured to execute not only CT imaging but also panoramic X-ray imaging and cephalometric radiography (cephalometric imaging).

  In FIG. 1, a left-handed XYZ orthogonal coordinate system and an xyz orthogonal coordinate system are attached. Here, the direction (here, the vertical direction) parallel to the axial direction of the turning axis (rotating axis) 31 of the support unit 300 is referred to as “Z-axis direction”, and the direction crossing the Z-axis is referred to as “X-axis direction”. Further, a direction intersecting the X-axis direction and the Z-axis direction is defined as “Y-axis direction”. Although the X-axis and Y-axis directions can be arbitrarily determined, here, the left and right directions of the subject when the subject who is the subject M1 is positioned in the X-ray imaging apparatus 100 and directly faces the column 50 are defined as X The axial direction is defined, and the front-rear direction of the subject is defined as the Y-axis direction. In the following description, the Z-axis direction may be referred to as the vertical direction, and the direction on the plane defined in two dimensions, the X-axis direction and the Y-axis direction, may be referred to as the horizontal direction.

  The xyz orthogonal coordinate system is a three-dimensional coordinate system defined on the support arm 30 that rotates. Here, the direction in which the X-ray generation unit 10 and the X-ray detection unit 20 face each other is referred to as “y-axis direction”, and the horizontal direction orthogonal to the y-axis direction is referred to as “x-axis direction”. The perpendicular direction that is orthogonal is defined as the “z-axis direction”. In the present embodiment, the Z-axis direction is the same direction as the z-axis direction. In addition, the support arm 30 of the present embodiment rotates around a turning shaft 31 extending in the vertical direction. Therefore, the xyz orthogonal coordinate system rotates around the Z axis (= z axis) with respect to the XYZ orthogonal coordinate system.

  In the present embodiment, as shown in FIG. 1, the right hand direction when the subject faces the support 50 is the (+ X) direction, the back direction is the (+ Y) direction, and the vertical direction is upward (+ Z). The direction. Further, when the X-ray generation unit 10 and the X-ray detection unit 20 are viewed from above, the direction from the X-ray generation unit 10 to the X-ray detection unit 20 is the (+ y) direction and the (+ y) side. The left hand direction is the (+ x) direction, and the upward direction in the vertical direction is the (+ z) direction. Therefore, the direction from the X-ray detection unit to the 20 X-ray generation unit 10 is the (−y) direction, the right-hand direction when facing the (+ y) side is the (−x) direction, and the downward direction in the vertical direction is (− z) direction.

  Furthermore, in the following, X, Y, Z, x, y, and z may be used to define a two-dimensional coordinate or a plane. For example, a two-dimensional coordinate composed of an X coordinate and a Y coordinate is defined as an XY coordinate, and a two-dimensional plane extending in the X direction and the Y direction is defined as an XY plane.

  The main unit 1 emits an X-ray beam composed of a bundle of X-rays toward the subject M1, and detects the X-rays emitted from the X-ray generator 10 and passed through the subject M1. The X-ray detection unit 20, the support unit 300 (support arm 30) that supports the X-ray generation unit 10 and the X-ray detection unit 20, and the support unit 300 are suspended and moved up and down in the vertical direction with respect to the support column 50. A possible lifting unit 40, a support column 50 extending in the vertical direction, and a main body control unit 60 are provided.

  The X-ray generation unit 10 and the X-ray detection unit 20 are respectively suspended and fixed at both ends of the support arm 30 and supported so as to face each other. The support arm 30 is suspended and fixed to the elevating unit 40 via a turning shaft 31 extending in the vertical direction.

  The X-ray generation unit 10 includes an X-ray generator 11 having an X-ray tube as an X-ray source, and a housing for housing the X-ray generator 11. The housing is attached to the support portion 300 so as to be rotatable around the Z axis. This rotation function is used, for example, at the time of cephalometric photography (see FIG. 2).

  The X-ray detection unit 20 includes a two-dimensional X-ray detector 21 that detects X-rays transmitted through the subject M1. The two-dimensional X-ray detector 21 constitutes an image sensor composed of a plurality of X-ray detection elements arranged so as to spread on a two-dimensional plane (here, xz plane). The X-ray detection element converts a signal corresponding to the intensity of the X-ray into an electric signal and outputs it to the outside. Frame image data (projection representing an X-ray projection image) in which the intensity of X-rays incident on the X-ray detection unit 20 by the image sensor is a required frame rate and each pixel has a pixel value corresponding to the X-ray intensity. Image data).

  In the present embodiment, the support unit 300 is configured by a support arm 30 that revolves around the revolving shaft 31, and the X-ray generation unit 10 and the X-ray detection unit 20 are attached to both ends of the substantially rectangular parallelepiped support arm 30. ing. However, the configuration of the support unit 300 that supports the X-ray generation unit 10 and the X-ray detection unit 20 is not limited to this. For example, the X-ray generator 10 and the X-ray detector 20 may be supported by an annular member in a state of facing each other, and the annular member may be rotated around an axis passing through the center thereof.

  The raising / lowering part 40 is engaged with the support | pillar 50 standingly arranged so that it may extend along a perpendicular direction. The elevating part 40 has a substantially U-shaped structure in which the upper frame 41 and the lower frame 42 protrude on the opposite side of the side engaged with the support column 50.

  An upper end portion of the support arm 30 is attached to the upper frame 41. Thus, the support arm 30 is suspended from the upper frame 41 of the elevating unit 40, and the support arm 30 moves up and down as the elevating unit 40 moves along the column 50.

  The lower frame 42 is provided with subject holding means 421. The subject holding means 421 is provided with a subject holding means 421 including a rod that fixes the head of the subject M1 from the left and right, a chin rest that fixes the chin, and the like. The head of the subject is fixed so that the front-rear direction of the head is parallel or substantially parallel to the Y-axis direction. That is, in a state where the head is fixed, the median sagittal section of the head is parallel or substantially parallel to the YZ plane defined by the Y-axis direction and the Z-axis direction. Note that the subject holding means 421 is not limited to a rod or a chin rest, and may include, for example, a bite block that fixes the head when the subject M1 bites.

  The support arm 30 is raised and lowered according to the height of the lifting / lowering unit 40 according to the height of the subject M1 and brought into an appropriate position, and the subject M1 is fixed to the subject holding means 421 in this state. In the example shown in FIG. 1, the subject holding unit 421 fixes the subject M1 so that the body axis of the subject M1 is the same or substantially the same as the axial direction of the turning shaft 31.

  As shown in FIG. 1, a main body control unit 60 that controls the operation of each component of the main body unit 1 is provided inside the X-ray detection unit 20. Each configuration of the main body 1 is accommodated in the X-ray prevention chamber 70. On the outside of the wall of the X-ray prevention chamber 70, various displays are provided with respect to the main body control unit 60 and a display unit 61 configured with a liquid crystal monitor or the like for displaying various information based on control from the main body control unit 60. An operation panel 62 composed of buttons and the like for realizing command input is attached. The operation panel 62 is also used for designating the position of an imaging region such as a living organ. X-ray imaging includes various modes (panoramic X-ray imaging, CT imaging, cephalometric imaging, etc.), and the mode can be selected by operating the operation panel 62.

  An operation panel 62A having the same or similar function as the operation panel 62 and a display unit having the same or similar function as the display unit 61 are provided on the back side of the two-dimensional X-ray detector 21 of the X-ray detection unit 20 of the main body 1. 61A is provided. For this reason, the operation of the main body 1 can be performed both inside and outside the X-ray prevention chamber 70.

  The information processing apparatus 8 includes an information processing main body 80 configured by, for example, a computer or a workstation, and can transmit and receive various data to and from the main body 1 using a communication cable. However, data may be exchanged between the main body 1 and the information processing apparatus 8 wirelessly.

  For example, a display unit 81 including a display device such as a liquid crystal monitor and an operation unit 82 including a keyboard and a mouse are connected to the information processing body unit 80. The operator can give various commands to the information processing main body 80 by a pointer operation using a mouse or the like on the characters and images displayed on the display unit 81. The display unit 81 can also be configured with a touch panel. In this case, the display unit 81 includes a part or all of the functions of the operation unit 82.

  FIG. 2 is a front view showing a cephalostat 43 applicable to the X-ray imaging apparatus 100. As shown in FIG. 2, a cephalostat 43 may be provided in the elevating unit 40. The cephalostat 43 is attached to, for example, an arm 501 that extends in the horizontal direction from the middle of the column 50. The cephalostat 43 is provided with a fixture 431 for fixing the head in a fixed position and an x-ray detector 432 for cephalo imaging. As the cephalostat 43, various types including a cephalostat disclosed in Japanese Patent Application Laid-Open No. 2003-245277 can be adopted.

  FIG. 3 is a block diagram illustrating a configuration of the X-ray imaging apparatus 100. As shown in FIG. 3, the main body 1 includes a turning mechanism 65 including a turning motor 60R, an X-axis motor 60X, and a Y-axis motor 60Y. The X-axis motor 60X and the Y-axis motor 60Y are an X-direction moving mechanism including a mechanical element that displaces the turning shaft 31 in the X-axis direction relative to the subject M1, and a machine that displaces in the Y-axis direction. The revolving shaft 31 is horizontally moved in the X-axis direction and the Y-axis direction, respectively, via the XY movement mechanism composed of both of the Y-direction movement mechanisms composed of the target elements.

  Further, the turning motor 60R rotates the turning shaft 31 around the Z axis via a turning mechanism including a mechanical element that rotates the turning shaft 31 relative to the subject M1. That is, the turning mechanism 65 causes the support arm 30 to move relatively horizontally or turn relative to the subject M1 positioned at the required position. In this sense, the turning mechanism 65 is also a moving mechanism that moves the support unit 300 relative to the subject M1. In the present embodiment, the turning mechanism 65 and the turning shaft 31 constitute a support part moving part. In the case where the displacement driving of the support portion 300 in the Z direction is also included in the movement of the support portion, the lifting and lowering motor (not shown) that drives the lifting and lowering portion 40 up and down in the vertical direction with respect to the support column 50 is also a turning mechanism 65. Included.

  The main body control unit 60 includes a CPU 601 and a fixed disk such as a hard disk, and is configured as a general computer in which a storage unit 602 that stores various data and programs PG1, a ROM 603, and a RAM 604 are connected to a bus line. have.

  The CPU 601 executes various control programs including a program PG1 for controlling the turning mechanism 65. More specifically, the CPU 601 executes the program PG1 stored in the storage unit 602 on the RAM 604, thereby controlling the X-ray generation unit control unit 601a that controls the X-ray generation unit 10 according to various imaging modes. And functions as an X-ray detector controller 601b that controls the X-ray detector 20. The X-ray generation unit control unit 601a can also control the X-ray irradiation X-ray dose, and may also have the function of an X-ray irradiation control unit. The X-ray detection unit control unit 601b controls the energy conversion unit moving mechanism 25 provided in the X-ray detection unit 20, for example.

  The CPU 601 functions as a drive control unit that drives and controls the turning mechanism 65, and controls the drive so that, for example, the X-ray generation unit 10 and the X-ray detection unit 20 move in a trajectory corresponding to various imaging. The CPU 601 controls the driving of the support unit moving unit by driving and controlling the turning mechanism 65 as a driving control unit.

  The CPU 601 constituting the main body control unit 60 and the CPU 801 constituting the information processing main body unit 80 integrally constitute a control system in the X-ray imaging apparatus 100.

  An operation panel 62 connected to the main body control unit 60 includes a plurality of operation buttons and the like. In addition to the operation buttons, a keyboard, a mouse, a touch pen, or the like can be used as an input device instead of the operation panel 62 or used together with the operation panel 62. Further, a voice command may be received and recognized by a microphone or the like. That is, the operation panel 62 is an example of an operation unit (operation unit). Therefore, the operation means may be provided with a configuration that accepts an operator's operation. In addition, the display unit 61 can be configured by a touch panel. In this case, the display unit 61 includes a part or all of the functions of the operation panel 62.

  Various kinds of information necessary for operation of the main body 1 are displayed on the display unit 61 as characters, images, and the like. However, the display content displayed on the display unit 81 of the information processing apparatus 8 may be displayed on the display unit 61. Further, various commands may be issued to the main body unit 1 through a pointer operation with a mouse or the like on a character or image displayed on the display unit 61.

  The main body control unit 60 specifies the position of the subject M1, and adjusts the trajectory when the X-ray generator 11 and the two-dimensional X-ray detector 21 are turned according to the specified position of the subject M1. For example, as shown in FIG. 4, the position of the subject M1 is such that the head of the subject M1 is located at a position where the jaw is fixed to the main body 1 by the chin rest. For this reason, the position of each part (especially jawbone and teeth) of the head can be easily specified. The same applies when a bite block is used as the subject holding means 421.

  The main body unit 1 is a region of interest (including a living organ, a bone (including a plurality of teeth, jaw bones, etc. constituting a dentition) or a joint) of the subject M1 in accordance with a command from the operation panel 62 or the information processing device 8. , Shoot using X-rays. The main body 1 receives various commands, coordinate data, and the like from the information processing device 8, and transmits X-ray projection image data acquired by imaging to the information processing device 8.

  The information processing main unit 80 includes a CPU 801 that executes various programs, a fixed disk such as a hard disk, and includes a storage unit 802 that stores various data (including projection image data) and a program PG2, a ROM 803, and a RAM 804. The computer has a configuration as a general computer connected to the bus line.

  The CPU 801 functions as a position setting unit 801a and an image generation unit 801b by executing the program PG2 stored in the storage unit 802 on the RAM 804. The position setting unit 801a sets the position of the tomographic plane according to the shape of the region of interest. More specifically, the position setting unit 801a receives a command based on an operation input via the operation unit 82 and sets a CT imaging region. The image generation unit 801b generates a CT image by performing image processing for reconstructing the projection image data acquired at the time of CT imaging.

  In the present embodiment, as will be described later, two projection image data having different energy distribution characteristics are acquired for the same CT imaging region. The projection image data is subjected to image processing, whereby a CT image corresponding to each energy distribution characteristic is generated in the information processing apparatus 8. As described above, the information processing apparatus 8 is an example of an image processing apparatus.

  FIG. 4 is a schematic perspective view for explaining CT imaging of the jaw by the main body 1. The turning mechanism 65 is connected to the turning shaft 31 and can turn the turning shaft 31 by 360 degrees or more. The turning mechanism 65 moves the support arm 30 along the XY plane. As a result, the positions of the X-ray generator 11 and the two-dimensional X-ray detector 21 in the XY plane are changed.

  In the present embodiment, the X-ray generator 11 and the two-dimensional X-ray detector 21 are rotated around the subject M1 by the turning mechanism 65, but the subject M1 may be rotated. In this case, a chair on which the subject M1 is seated may be provided and the chair may be rotated. As a result, the X-ray generator 11 and the two-dimensional X-ray detector 21 can be turned relative to the subject M1.

  In addition, the X-ray generation unit 10 includes an irradiation field control unit 12. The irradiation field control unit 12 includes a slit plate 12a disposed in front of the X-ray generator and a moving mechanism that slides the slit plate 12a. A plurality of slits having different shapes are formed in the slit plate 12a. The irradiation field control unit 12 can select a specific slit from a plurality of slits by sliding the slit plate 12 a to the left and right based on a control signal from the main body control unit 60. The X-rays emitted from the X-ray generator 11 pass through the selected rectangular slit, and are shaped into a substantially pyramid-shaped (cross-sectionally rectangular) X-ray cone beam BX1. When performing panoramic X-ray imaging or cephalometric imaging, a vertically long X-ray slit beam is formed by moving the slit plate 12a to an appropriate position. In the X-ray imaging apparatus 100, panoramic X-ray imaging or cephalometric imaging is performed using the X-ray slit beam. The irradiation field control unit 12 is an example of an X-ray restriction unit.

  In addition, it is also conceivable to form a slit through which X-rays pass by combining a plurality of members instead of the slit plate 12a. In this case, a moving mechanism for moving each member may be provided so that the vertical and horizontal sizes of the slit can be controlled by moving each member. This makes it possible to arbitrarily adjust the spread of the X-ray beam.

  FIG. 5 shows the main body 1 that performs CT imaging of the jaw of the subject head along the direction of the rotation axis RA of the X-ray generator 11 and the two-dimensional X-ray detector 21 from the head side of the subject M1. FIG. Here, the X-ray cone beam BX1 has the entire jaw portion of the subject M1 as a CT imaging region RR, and has a spread including the upper and lower jaw teeth DA. In the present application, the CT imaging region refers to a range in which the X-ray cone beam BX1 is always irradiated in order to collect projection image data. In the example shown in FIG. 5, the CT imaging region RR is cylindrical. For this reason, when the CT imaging region RR is viewed from above along the axial direction of the turning shaft 31, it is a perfect circle. The plane shape of the CT imaging region is not limited to a perfect circle. For example, the planar shape of the CT imaging region may be an elliptical shape.

  In the example shown in FIG. 5, the rotation axis RA is fixed at a position passing through the inside of the dental arch formed by the tooth group DA. Further, the rotation axis RA coincides with the turning axis 31 of the support arm 30. Further, the main body control unit 60 drives the turning mechanism 65 in a state where the subject M1 is irradiated with the X-ray cone beam BX1, and rotates the support arm 30 by a required angle (for example, 360 degrees). Thereby, the projection image projected on the detection surface 21S of the two-dimensional X-ray detector 21 is collected as projection data of the subject M1. The collected projection image data is stored in the storage unit of the main body control unit 60. The projection image data is appropriately transmitted to the information processing apparatus 8 after CT imaging or during CT imaging.

  During CT imaging, the X-ray generator 11 and the two-dimensional X-ray detector 21 relatively rotate around the subject M1 while facing each other with the tooth group DA that is a region of interest of the subject M1 interposed therebetween. At this time, the turning shaft 31 may be fixed at a specific location on the XY plane, but may be moved within the XY plane. In any case, the rotation axis RA during CT imaging is set at a specific location on the XY plane. FIG. 5 illustrates a case where the rotation axis is the turning axis 31.

  Next, the configuration of the X-ray detection unit 20 will be described. As shown in FIGS. 3 and 4, the X-ray detector 20 includes a two-dimensional X-ray detector 21 and an energy converter 23. In FIG. 5, the X-ray detection unit 20 is simply indicated by an arrow, but the configuration can be easily understood with reference to FIGS. 3 and 4. The two-dimensional X-ray detector 21 has a flat X-ray receiving surface that receives X-rays. The two-dimensional X-ray detector 21 is formed by two-dimensionally arranging a plurality of elements that output generated charges as electric signals on the X-ray light receiving surface. The element is made of, for example, a cadmium telluride semiconductor or an amorphous selenium semiconductor. X-rays that have passed through the subject M1 are converted into X-rays having different energy distributions by the filters 231 and 233 and enter each element made of a semiconductor.

  The energy conversion unit 23 is disposed so as to be interposed between the subject M1 and the two-dimensional X-ray detector 21. The energy conversion unit 23 is arranged in the path of the X-ray cone beam BX1, or at least arranged so as to appear in the path of the X-ray cone beam BX1.

  The detection surface 21S of the two-dimensional X-ray detector 21 may not be a plane. For example, the detection surface may be a curved surface that is recessed in the + y direction. In addition, one detection surface 21S may be formed by connecting several flat surface portions or curved surface portions.

  The two-dimensional X-ray detector 21 is composed of a scintillator and a semiconductor element that detects light (fluorescence) generated when X-rays enter the scintillator instead of including a semiconductor element that directly detects X-rays. It may be.

  The energy conversion unit 23 is disposed on the front surface of the two-dimensional X-ray detector 21. The energy conversion unit 23 is configured by two-dimensionally arranging two filters 231 and 233 having different characteristics (conversion characteristics) for converting the energy distribution of the X-ray cone beam BX1. That is, the energy conversion unit 23 is a filter configuration having a filter 231 (first filter) in the first part and a filter 233 (second filter) having a conversion characteristic different from that of the filter 231 in the second part. is there.

  For example, one of the filters 231 and 233 is a filter that passes X-rays in a relatively low energy region, and the other is a filter that passes X-rays in a relatively high energy region. As the filters 231 and 233, for example, different plate materials may be selected from an aluminum plate, a titanium plate, an iron plate, and a copper plate. In addition, you may use the board | plate material of the same material about the filters 231,233. In this case, the energy distributions of the transmitted X-rays can be made different from each other by making the thicknesses (widths in the y-axis direction) of the filters 231 and 233 different from each other.

  The filters 231 and 233 are arranged on the front side (that is, the −y side) of the two-dimensional X-ray detector 21 and are arranged continuously without a gap in the x-axis direction. More specifically, the filters 231 and 233 are integrally held by a holding mechanism (not shown). That is, the energy conversion unit 23 constitutes a single plate-like body. In the example illustrated in FIG. 4, the filter 231 is disposed on the + X side, and the filter 233 is disposed on the −X side.

  The X-ray detection unit 20 includes an energy conversion unit moving mechanism 25 that moves the energy conversion unit 23. As shown in FIG. 4, the energy conversion unit moving mechanism 25 includes, for example, a motor 251 as a drive source that moves the energy conversion unit, and a transmission unit 252 that transmits the motor movement (rotational movement) to the energy conversion unit 23. In addition, it is composed of a guide member that defines the moving direction of the energy conversion unit 23.

  In CT imaging, the energy conversion unit moving mechanism 25 moves the energy conversion unit 23 so as to cross the X-ray cone beam BX1 while the support arm 30 (support unit 300) rotates. In other words, the energy conversion unit moving mechanism 25 moves the energy conversion unit 23 in a direction intersecting the central axis of the X-ray cone beam BX1 during X-ray imaging. In the present embodiment, the energy conversion unit moving mechanism 25 moves the energy conversion unit 23 in the direction along the detection surface 21S of the two-dimensional X-ray detector 21 (in the example shown in FIG. 4, the x axis is parallel to the detection surface 21S). Direction).

  A typical example of the direction along the detection surface 21S in which the energy conversion unit 23 moves is a direction parallel to the two-dimensional direction in which the detection surface 21S spreads. However, if the object of obtaining projection image data having different characteristics by passing each of the portions having different energy distribution conversion characteristics through the X-ray beam is achieved, the moving direction of the energy conversion unit 23 is determined by the detection surface 21S. It may be a combined direction in which the orthogonal directions orthogonal to are also combined. Therefore, the moving direction of the energy conversion unit 23 is not necessarily a direction parallel to the detection surface 21S of the two-dimensional X-ray detector 21. That is, the moving direction of the energy conversion unit 23 may be a combined direction obtained by combining a two-dimensional direction defined on a two-dimensional detection surface and an orthogonal direction orthogonal to the detection surface 21S.

  The two-dimensional X-ray detector 21, the energy conversion unit 23, and the energy conversion unit moving mechanism 25 are disposed in the housing 210 of the X-ray detection unit. The energy conversion unit 23 moves inside the housing 210.

  Although illustration is omitted, the energy conversion unit 23 may include an attachment / detachment mechanism that detachably holds the filters 231 and 233. This makes it easy to replace the filter. It is also possible to perform X-ray imaging with the filter removed.

  Further, either one of the filters 231 and 233 can be omitted. In this case, the energy conversion unit is a filter structure (first filter structure) having a filter in the first part and no filter in the second part. In the case of such a filter configuration, the X-rays incident on the part having the filter and the part not having the filter can have different energy distribution conversion characteristics. Thereby, the X-rays incident on the first part and the second part can be converted into X-rays having different energy distribution characteristics. Further, if the entire region of the X-ray cone beam BX1 passes through the second part without a filter, X-ray imaging without a filter can be performed.

  On the other hand, the above-described filter structure having the filter 231 (first filter) in the first part and the filter 233 (second filter) having a conversion characteristic different from that of the filter 231 in the second part is as follows. It is a 2nd filter structure.

<First CT imaging example>
FIG. 6 is a schematic plan view for explaining a first CT imaging example in the X-ray imaging apparatus 100 according to the first embodiment. In this CT imaging example, the two-dimensional X-ray detector 21 detects the X-ray cone beam BX1 irradiated to the CT imaging region RR1 through the filter 231 and the filter 233. In the following description, the projection image data obtained through the filter 231 may be referred to as first projection image data, and the projection image data obtained through the filter 233 may be referred to as second projection image data. Further, the spread angle (fan angle) of the X-ray cone beam BX1 in the xy plane is defined as α.

  In this CT imaging example, the X-ray generator 11, the two-dimensional X-ray detector 21, and the energy conversion unit 23 are rotated around the center C1 (here, clockwise) of the CT imaging region RR1. In the following description, the rotation angle is defined with the clockwise direction as the positive direction.

  6A is a state where the rotation angle is 0 degree, FIG. 6B is a state where the rotation angle is 180-α degrees, FIG. 6C is a state where the rotation angle is 180 degrees, and FIG. Shows a state where the rotation angle is 180 + α degrees, and FIG. 6E shows a state where the rotation angle is 360 degrees.

  Points E11 and E12 shown in FIG. 6A are points on the contour line that defines the CT imaging region RR1, and are contact points that contact the outer edge of the X-ray cone beam BX1 when the rotation angle is 0 degrees. The point E11 is located on the + x side in the CT imaging region RR1, and the point E12 is located on the −x side in the CT imaging region RR1.

As shown in FIG. 6A, immediately after the start of CT imaging in this example, the energy conversion unit 23 is arranged so that the entire region of the X-ray cone beam BX1 that has passed through the CT imaging region RR1 enters the filter 231. The In this case, the width of the X-ray cone beam BX1 in the filter 231 is incident (the length of the x-axis direction) _{W 1.}

  At the start of CT imaging, the energy conversion unit 23 is at a position where X-rays that have passed through the point E12 irradiate the boundary portion 235 of the filters 231 and 233. The energy conversion unit 23 does not displace the filters 231 and 233 until the rotation angle is 180-α degrees shown in FIG.

  From this state, the X-ray generator 11, the two-dimensional X-ray detector 21, and the energy conversion unit 23 rotate together to detect X-rays through the filter 231 for a predetermined period. However, the X-ray generator 11 starts to rotate from a position closer to the rotation direction than the position shown in FIG. 6A (that is, a position on the −X side from the position shown in FIG. 6A). You may do it.

  As shown in FIG. 6B, when the rotation angle is changed from 0 degrees to 180-α degrees, the outer edge on the −x side of the X-ray cone beam BX1 contacts the point E11 of the CT imaging region RR1. That is, by changing the rotation angle from 0 degrees to 180-α degrees, X-ray irradiation is performed on each point E11 from exactly 180 degrees. That is, the first projection image data for 180 degrees for the point E11 in the CT imaging region RR1 is collected. Then, the energy conversion unit moving mechanism 25 moves the energy conversion unit 23 in the + x direction from the time when the rotation angle exceeds 180−α degrees. This movement in the + x direction is a movement in a direction opposite to the movement direction of the two-dimensional X-ray detector 21.

  As shown in FIG. 6B, when the rotation angle reaches 180-α degrees, the outer edge on the −x side of the X-ray cone beam BX1 passes through the boundary portion 235 of the filters 231 and 233. At the same time, the displacement of the energy conversion unit 23 in the + x direction starts, so that X-rays that have passed through the filter 233 begin to enter the two-dimensional X-ray detector 21 immediately after the movement of the energy conversion unit 23 starts. That is, as shown in FIG. 6B, the state in which the rotation angle is 180-α degrees is a state in which acquisition of the second projection image data for the point E11 is started. Here, a range in which the X-ray cone beam BX1 is incident in the two-dimensional X-ray detector 21 is defined as a total incident range RA1. Then, in the two-dimensional X-ray detector 21, the range in which the X-ray cone beam BX1 transmitted through the filter 233 is incident gradually spreads from the −x side end portion to the + x side in the total incident range RA1. Become.

The amount of movement of the energy conversion unit 23 is set to a magnitude proportional to the amount of change in the rotation angle. More specifically, the amount of movement of the energy conversion unit 23 is W ₁ / 2α per rotation angle. Therefore, as shown in FIG. 6C, when the rotation angle is 180 degrees, the rotation is α degrees. For this reason, the movement amount of the energy conversion unit 23 is W _1/2 . Therefore, in the X-ray cone beam BX 1, the + x side half enters the filter 231 and the −x side half enters the filter 233. In addition, among the X-ray cone beam BX1, X-rays passing through the center C1 of the CT imaging region RR1 enter the boundary portion 235.

Further, as shown in FIG. 6D, when the rotation angle is 180 + α degrees, the rotation angle is 2α degrees from the state shown in FIG. Therefore, the amount of movement of the energy conversion unit 23 is W _1. Filter 233 same displacement amount _{W 1} minute displacement and the filter 231 in the same direction. Therefore, the outer edge on the + x side of the X-ray beam is in contact with the point E12. In this CT imaging example, the movement of the energy conversion unit 23 by the energy conversion unit moving mechanism 25 is completed at this point. In this state, the entire region of the X-ray cone beam BX1 passes through the filter 233 and enters the two-dimensional X-ray detector 21. In other words, this state is a state in which the acquisition of the second projection image data for the point E12 is started. In this CT imaging example, the X-ray generator 11 continues to rotate until the rotation angle reaches 360 degrees, and projection image data is acquired.

  FIG. 7 is a diagram schematically showing a sinogram obtained in the first CT imaging example shown in FIG. In FIG. 7, the horizontal axis indicates the position of the detection surface 21S in the two-dimensional X-ray detector 21 in the x-axis direction, and the vertical axis indicates the rotation angle. A curve CL11 shows the movement locus of the projection position of the point E11, and a curve CL12 shows the movement locus of the projection position of the point E12.

  As indicated by the curve CL11, the projection position of the point E11 starts from the + x side end of the total incident range RA1, and gradually moves to the −x side. The projection position is located at the −x side end of the entire incident range RA1 when the rotation angle is 180−α degrees. When the rotation further proceeds, the projection position starts to move to the + x side, and when the rotation angle reaches 360 degrees, the projection position returns to the + x side end of the entire incident range RA1.

  The point E12 can also be easily understood from the explanation about the point E11. As indicated by the curve CL12, the projection position of the point E12 starts from the −x side end of the total incident range RA1, and gradually moves to the −x side. The projection position is located at the + x side end of the entire incident range RA1 when the rotation angle is 180 + α degrees. When the rotation further proceeds, the projection position starts to move to the −x side, and when the rotation angle reaches 360 degrees, the projection position returns to the −x side end of the entire incident range RA1.

  As described in FIG. 6, while the rotation angle changes from 180−α degrees to 180 + α degrees, the energy conversion unit 23 moves in the + x direction, so that X-rays transmitted through the filter 233 start to be detected. For this reason, on the sinogram shown in FIG. 7, the first area AR11 (shown by diagonal lines) corresponding to the first projection image data of the total projection image data and the second projection image of the total projection image data. There is a second area AR12 corresponding to the data. On the sinogram, a straight line L1 connecting the position of the −x side end at 180−α degrees to the position of the + x side end at 180 + α degrees is a boundary line between the first area AR11 and the second area AR12.

  Here, attention is focused on the projection positions of the points E11 and E12 of the CT imaging region RR1. On the sinogram, as indicated by the curves CL11 and CL12, the projection positions of the points E11 and E12 move to the + x side or −x side after the start of rotation, and then turn back points (points SP1 and SP1 on the straight line L1). Moves in the reverse direction (−x side or + x side) through SP2) and returns to the initial position. Although not shown, the projection position of another specific point (hereinafter referred to as “specific point”) of the CT imaging region RR1 is also narrower on the sinogram than the movement width of the points E11 and E12. However, as the rotation angle increases, the process proceeds in the + x direction or the −x direction, turns back at a specific rotation angle on the straight line L1, proceeds in the reverse direction, and returns to the initial projection position.

  As described above, for a specific point, when the projection position starts to move and reaches the turning point on the straight line L1 (for example, the turning points SP1 and SP2 for the point E11 and the point E12), the portion passing through the filter 231 is obtained. The X-ray irradiation of just 180 degrees will be completed. Further, the projection position returns from the turning point on the straight line L1 to the initial projection position, so that the X-ray irradiation of exactly 180 degrees is completed for the passage through the filter 233. Since the straight line L1 is a boundary line between the first area AR11 and the second area AR12, each of the first area AR11 and the second area AR12 includes projection image data of exactly 180 degrees for each specific point. Become.

  As described above, according to this CT imaging example, a so-called dual energy scan that acquires first projection image data and second projection image data having different energy distributions for the same CT imaging region RR1 can be realized. By dual energy scanning, two types of CT images (tomographic images) corresponding to the energy distribution characteristics of the X-rays that have passed through the filters 231 and 233 are obtained from two types of projection image data having different energy distribution characteristics for the same tomographic plane. be able to. Such multiple types of X-ray images (CT images) are generated by image processing by the information processing apparatus 8. About each CT image, you may make it acquire the image which the specific site | part showed clearly, for example by performing a difference calculation process and acquiring the image of a difference.

  Further, when the X-ray cone beam BX1 rotates 360 degrees around the center C1 of the CT imaging region RR1, X-rays can be irradiated from 180 degrees in each point included in the CT imaging region RR1. That is, since two projection image data with different energy distributions can be acquired by one CT imaging over the entire CT imaging region RR1, dual energy scanning can be realized in a relatively short time.

  Further, since the energy conversion unit 23 is moved during CT imaging, the boundary portion 235 of the filters 231 and 233 is moved during CT imaging. Accordingly, it is possible to reduce the concentration of X-rays incident and scattered near the boundary portion 235 and entering the specific position of the two-dimensional X-ray detector 21. For this reason, the influence of the scattered X-ray on the CT image can be reduced. As a result, the effect of scattered X-rays can be reduced and the X-ray energy discrimination ability can be improved. In the above description, in order to facilitate understanding in principle, the angle is set to 180 degrees (half rotation) or 360 degrees (one rotation). However, in practice, a CT image can be obtained even if there is some increase or decrease in the rotation angle, so the setting may be approximately (substantially) 180 degrees or approximately 360 degrees. Hereinafter, the same applies to any of the embodiments.

  FIG. 8 is a schematic plan view showing a modification of the first CT imaging example shown in FIG. The CT imaging shown in FIG. 8 is an imaging of a CT imaging region RR2 smaller than the CT imaging region RR1 shown in FIG. In FIG. 8, the fan angle of the X-ray cone beam BX2 is β. 8A is a state where the rotation angle of the X-ray generator 11 is 0 degree, FIG. 8B is a state where the rotation angle is 180-β degrees, FIG. 8C is a state where the rotation angle is 180 degrees, FIG. 8D shows a state where the rotation angle is 180 + β degrees, and FIG. 8E shows a state where the rotation angle is 360 degrees.

  The fan angle β of the X-ray cone beam BX2 irradiated to the CT imaging region RR2 is smaller than the fan angle α of the X-ray cone beam BX1 irradiated to the CT imaging region RR1.

  Even when the CT imaging region RR2 is narrow, movement control of the energy conversion unit 23 is performed in the same manner as in the CT imaging region RR1 during CT imaging. That is, in the state where the rotation angle of the X-ray generator 11 is 0 degree (the state shown in FIG. 8A), the energy conversion unit 23 is arranged so that the X-ray cone beam BX1 passes only through the filter 231, for example. The two-dimensional X-ray detector 21 detects the X-ray cone beam BX1 transmitted only through the filter 231 until the rotation angle reaches a state of 180-α degrees (the state shown in FIG. 8B). To do.

  Then, while the rotation angle changes from 180−β degrees to 180 + β degrees, the energy conversion unit 23 is moved in the + x direction, and the filter 231 is gradually switched to the filter 233. Then, the X-ray generator 11 is rotated until the rotation angle reaches 360 degrees, and CT imaging is completed.

  As described above, even when the CT imaging region is small, it is possible to realize the dual energy scan by moving the filters 231 and 233 during the CT imaging.

<Second CT imaging example>
FIG. 9 is a schematic plan view for explaining a second CT imaging example in the X-ray imaging apparatus 100 according to the first embodiment. 9A is a state where the rotation angle is 0 degree, FIG. 9B is a state where the rotation angle is 180-α degrees, FIG. 9C is a state where the rotation angle is 180 degrees, and FIG. FIG. 9E shows a state where the rotation angle is 180 + α degrees, FIG. 9E shows a state where the rotation angle is 180 degrees−α, and FIG. 9F shows a state where the rotation angle is 0 degrees.

  In this CT imaging example, as shown in FIGS. 9A to 9D, the X-ray generator 11, the two-dimensional X-ray detector 21, and the rotation angle are between 0 ° and 180 + α degrees. The energy conversion unit 23 rotates in the same manner as in the first CT imaging example shown in FIG. 6, and the energy conversion unit 23 relatively moves in the + x direction. However, as shown in FIG. 9D, when the rotation angle reaches 180 + α degrees, the rotation of the X-ray generator 11 and the two-dimensional X-ray detector 21 is stopped, and in the reverse direction (here, counterclockwise). Rotate. Then, as shown in FIGS. 9E and 9F, the X-ray generator 11 is reversely rotated until the rotation angle becomes 0 degree. From the state shown in FIG. 9D to the state shown in FIG. 9F, the relative positions of the energy conversion unit 23 with respect to the X-ray generator 11 and the two-dimensional X-ray detector 21 are fixed.

  FIG. 10 is a diagram schematically showing a sinogram obtained in the second CT imaging example shown in FIG. A curve CL21 shows the movement locus of the projection position of the point E11, and a curve CL22 shows the movement locus of the projection position of the point E12. Further, the first area AR21 indicated by hatching is a portion corresponding to the first projection image data in the total projection image data, and the second area AR22 corresponds to the second projection image data in the total projection image data. It is a part to do.

  In the sinogram according to this CT imaging example, the movement trajectory of the projection position of each point in the CT imaging region RR1 coincides with that of the sinogram shown in FIG. 7 when the rotation angle is 0 degree to 180 + α degrees. However, in this CT imaging example, the rotation is reversed when the rotation angle is 180 + α degrees. The projection position of each point in the CT imaging region RR1 until the rotation angle is changed from 180 + α degrees to 0 degree reverses the movement locus of the projection position until the rotation angle is changed from 0 degrees to 180 + α degrees. That is, on the sinogram, the projection positions of the respective points in the CT imaging region RR1 are contrasted with a straight line passing through 180 + α degrees as axes such as the curves CL21 and CL22 typically shown in FIG.

  Here, for the point E12, when the rotation angle changes from 0 degree to 180 + α degrees, projection of just 180 degrees through the filter 231 is performed, and when the rotation angle changes from 180 + α degrees to 0 degree, A projection of exactly 180 degrees through the filter 233 is performed. That is, for the point E12, the first projection image data and the second projection image data can be acquired without excess or deficiency. However, for the other points in the CT imaging region RR1, the second projection image data obtained through the filter 233 is acquired up to 180 degrees. For example, paying attention to the point E11, while the rotation angle changes from 0 degrees to 180-α degrees, projection image data of just 180 degrees through the filter 231 is obtained, and then the rotation angle starts from 180-α degrees. While changing to 0 degree, projection image data of exactly 180 degrees through the filter 233 is obtained. While the rotation angle changes from 180-α to 180 degrees + α and from 180 + α degrees to 180-α degrees, the same projection image data is acquired in duplicate.

  Thus, in the second CT imaging example, projection image data with partially overlapping projection angles is acquired. Overlapping projection image data can also be excluded during the CT image reconstruction calculation. In this case, the reconstruction calculation can be reduced as compared with the case of using all projection image data. Of course, overlapping projection image data may be taken into the reconstruction calculation. In this case, a CT image with higher reliability can be obtained as compared with a CT image reconstructed with a minimum amount of projection image data.

  The energy conversion unit moving mechanism 25 may move the energy conversion unit 23 to a position where it is retracted from the incident position of the cone beam that has passed through the CT imaging region RR1. Thereby, in the same X-ray imaging apparatus 100, X-ray imaging using the filters 231 and 233 and X-ray imaging without using a filter are possible. In the case of this modification, in CT imaging in which the X-ray generator 11 and the two-dimensional X-ray detector 21 are rotated once, either the filter 231 or the filter 233 is moved by appropriately moving the energy conversion unit 23. It is possible to acquire the projection image data via and the projection image data not via the filter, respectively.

  In the first CT imaging and the second CT imaging, the energy conversion unit 23 is moved in the same direction as the movement direction (+ x direction) of the two-dimensional X-ray detector 21. You may move to the direction (-x direction) which opposes a moving direction. In this case, X-ray detection through the filter 233 is performed first, and then the energy conversion unit 23 is moved in the −x direction to perform X-ray detection through the filter 231.

<2. Second Embodiment>
Next, a second embodiment will be described. In the following description, the same elements as those already described or elements having a similar function may be denoted by the same reference numerals or characters added, and detailed description may be omitted.

<Third CT imaging example>
11 and 12 are schematic plan views for explaining a third CT imaging example in the X-ray imaging apparatus 100a according to the second embodiment. 11A is a state where the rotation angle is 0 degree, FIG. 11B is a state where the rotation angle is 90 degrees, FIG. 11C is a state where the rotation angle is 180 degrees, and FIG. FIG. 11E shows a state where the angle is 270 degrees, and FIG. 11E shows a state where the rotation angle is 360 degrees. 12A shows a state where the rotation angle is 360 degrees, FIG. 12B shows a state where the rotation angle is 450 degrees, FIG. 12C shows a state where the rotation angle is 540 degrees, and FIG. Shows a state where the rotation angle is 630 degrees, and FIG. 12E shows a state where the rotation angle is 720 degrees.

In the X-ray imaging apparatus 100 according to this embodiment, the energy conversion unit 23a has two filters 231a (first part) and two filters 233a (second part) arranged alternately in a striped pattern in the x-axis direction. ing. For this reason, the energy conversion part 23a has four conversion parts. In the following description, each filter 231a, the x-axis direction width of 233a and _{W 2.} In the following description, of the two filters 231a and 231a, the filter 231a on the + x side is referred to as a + x side filter 231a, and the other filter 231a is referred to as a −x side filter 231a. Of the two filters 233a and 233a, the filter 233a sandwiched between the + x side filter 231a and the -x side filter 233a is referred to as a + x side filter 233a, and the other filter 233a is referred to as a -x side filter 233a. Called.

  In this CT imaging example, a CT image is acquired by executing a dual energy scan using the striped energy conversion unit 23a. For this reason, as shown in FIGS. 11 and 12, CT imaging is rotated by 720 degrees (that is, two rotations) while the energy conversion unit 23 is moved in the x-axis direction.

More specifically, as shown in FIG. 11A, in the state where the rotation angle is 0 degree, the + x side half of the X-ray cone beam BX1 is incident on the + x side filter 231a and the -x side half is + x. The energy conversion unit 23a is disposed so as to enter the filter 233a on the side. In this embodiment, each filter 231a, x-axis direction width of the X-ray cone beam BX1 incident on each of 233a, the filter 231a, coincides with the width _{W 2} of 233a. Then, the X-ray generator 11 and the two-dimensional X-ray detector 21 are rotated about the center C1 of the CT imaging region RR1 as the rotation axis, and the energy conversion unit 23a is moved to the + x side. The amount of movement of the energy conversion unit 23a is an amount proportional to the amount of change in the rotation angle. More particularly, the moving amount of the energy conversion unit 23a is a _W 2/360 per rotation angle of one degree.

For example, as shown in FIG. 11 (c), the rotational angle is 180 degrees state, the amount of movement is _W 2/2. For this reason, the energy conversion unit 23a is located at a position where the X-ray passing through the center C1 of the CT imaging region RR1 passes through the center of the filter 233a on the + x side. Further, as shown in FIG. 11 (e), the rotational angle is 360 degrees state, the movement amount _{W 2} becomes, of X-ray cone beam BX1, + x side of the portion is incident in the + x side of the filter 233a, The portion on the -x side is incident on the filter 231a on the -x side.

  FIG. 13 is a diagram schematically showing a sinogram obtained by the third CT imaging example shown in FIGS. 11 and 12. In the sinogram shown in FIG. 13, the first area part AR31a, indicated by hatching, is a part corresponding to the first projection image data obtained through the 231a on the + x side in the entire projection image data. The first area portions AR31b and AR31c are portions corresponding to the first projection image data obtained through the −x side 231a among all the projection image data. The second area portions AR32a and AR32b are portions corresponding to the second projection image data obtained via the + x side filter 233a among all the projection image data. The second area part AR32c is a part corresponding to the second projection image data obtained through the filter 233a on the -x side in the entire projection image data.

  A curve L31 illustrated in FIG. 13 indicates the movement locus of the projection position of the point E11. A curve L32 shows the movement locus of the projection position of the point E12. Of the curves L31 and L32, the curve portion included in the first area part AR31c (the rotation angle is in the range from 360 degrees to 720 degrees) is the second area part AR32a (the rotation angle is in the range from 0 degrees to 360 degrees). The shape is the same as the curved part included in. That is, the curved portions of these area portions can be exchanged.

  FIG. 14 is a diagram schematically showing a sinogram obtained by modifying the sinogram shown in FIG. According to the sinogram shown in FIG. 14, first projection image data of just 360 degrees is acquired for each point in the CT imaging region RR1 in the range of 0 degrees to 360 degrees, and 360 degrees to 720 degrees. In this range, the second projection image data of the CT imaging region of 360 degrees is acquired.

  In the present embodiment, in a simple expression, data that is insufficient in the range of the rotation angle of 0 to 360 degrees is supplemented in the range of the next rotation angle of 360 to 720 degrees. For this reason, it is good also considering the moving direction of the energy conversion part 23 as a direction opposite to what is shown in FIG.11 and FIG.12.

That is, in the examples of FIGS. 11 and 12, the + x end of the + side filter 231a is in contact with the + x side of the X-ray cone beam BX1 at a rotation angle of 0 degree. Then, the energy conversion unit 23 is moved in the + x direction by 2 W ₂ until the rotation angle is 720 degrees. This is so that the -x end of the -x side filter 233a is in contact with the -x side of the X-ray cone beam BX1 at a rotation angle of 0 degree. Then, the energy conversion unit 23 may be moved in the −x direction by 2W ₂ until the rotation angle is 720 degrees. Even in this case, the energy conversion unit 23 moves along the direction in which the two-dimensional X-ray detector 21 moves.

  As described above, according to the CT imaging shown in FIGS. 11 and 12, the first projection image data for 360 degrees obtained through the two filters 231a and 231a and the 360 obtained through the two filters 233a and 233a. Second projection image data corresponding to the degree is obtained. Therefore, dual energy scanning can be performed by appropriately moving the energy conversion unit 23a.

<4th CT imaging example>
FIG. 15 is a diagram schematically showing a sinogram for explaining a fourth CT imaging example in the X-ray imaging apparatus 100 according to the second embodiment. As shown in FIG. 14, in this CT imaging example, the rotation of the X-ray generator 11 and the two-dimensional X-ray detector 21 and the movement of the energy conversion unit 23a in the x-axis direction have been described with reference to FIGS. This is performed in the same manner as in the third CT imaging example. However, X-ray shielding or the like is performed so that X-ray irradiation does not irradiate the CT imaging region RR1 in the range of rotation angles from 180 + α degrees to 360 degrees and from 540 + α degrees to 720 degrees.

  On the sinogram shown in FIG. 15, the projection image data farmland obtained in the range of 0 to 180 + α degrees, the first area portions AR41a and AR41b shown by diagonal lines correspond to the first projection image data portion, and the second area portion AR42a. Corresponds to the second projection image data. In addition, among the projection image data obtained in the range of 360 degrees to 540 + α degrees, the first area portion AR41c indicated by hatching corresponds to the first projection image data portion, and the second area portions AR42b and AR42c are the second projection image. Corresponds to data.

  Here, the movement trajectory of the projection position of each point included in the CT imaging region RR1 coincides with the range from 0 degrees to 180 + α degrees and the range from 360 degrees to 540 + α degrees. That is, the movement trajectory of the projection position of each point in the first area AR41c and the movement trajectory of the projection position of each point in the second area AR42a coincide with each other. For this reason, these areas can be alternately replaced. Then, 1st area part AR41a, AR41b, AR41c is corresponded to the 1st projection image data for 180 degree | times through the two filters 231a and 231a. The second area portions AR42a, 42b, and 42c correspond to second projection image data for 180 degrees through the two filters 233a and 233a. Thus, also in this CT imaging example, it is possible to acquire projection image data for 180 degrees having different energy distribution characteristics.

<Fifth CT imaging example>
16 and 17 are schematic plan views illustrating fifth CT imaging examples in the X-ray imaging apparatus 100a according to the second embodiment. In the present CT imaging, the X-ray generator 11 and the two-dimensional X-ray detector 21 are rotated by 180 + α degrees, and then rotated in the reverse direction to the original position, and the energy conversion unit 23a is moved to the + x side. For this reason, in this CT imaging, the ratio of the portion incident on the two filters 231 in the X-ray cone beam BX1 and the portion incident on the second energy distribution by the filter 233a changes every moment according to the rotation angle. To do.

  FIG. 16 shows each state when the X-ray generator 11 is rotated forward from 0 degree to 180 + α degrees. 16A is a state where the rotation angle is 0 degree, FIG. 16B is a state where the rotation angle is 90 degrees, FIG. 16C is a state where the rotation angle is 180-α degrees, and FIG. Each shows a state in which the rotation angle is 180 + α degrees. FIG. 17 shows each state when the X-ray generator 11 is rotated backward from 180 + α degrees to 0 degrees. 17A is a state where the rotation angle is 180 + α, FIG. 16B is a state where the rotation angle is 180-α degrees, FIG. 16C is a state where the rotation angle is 90 degrees, and FIG. The angle is 0 degree.

As shown in FIGS. 16 and 17, the amount of movement of the energy conversion unit 23a is an amount proportional to the amount of change in the rotation angle. More specifically, the movement amount is W ₂ / (180 + α) with respect to the rotation angle of 1 degree. That is, as shown in FIG. 16 (d), in the state of the rotation angle is 180 + alpha degrees, 0 degrees the energy conversion unit 23a from the state of, and relatively moved by the width W ₂ in the + x side, the + x side filter The X-ray cone beam BX1 is incident on the filter 231a on the 233a and -x side. Then, also, as shown in FIG. 17 (d), when the rotation angle by the reverse rotation becomes 0 degrees, move relative to the energy conversion unit 23a further + x side by a width W _2, the -x side filter The X-ray cone beam BX1 is incident on 231a and 233a.

  FIG. 18 is a diagram schematically showing a sinogram obtained in the fifth CT imaging example shown in FIGS. 16 and 17. In the sinogram shown in FIG. 18, the first area portions AR51a, AR51b, AR51c indicated by diagonal lines are portions corresponding to the first projection image data, and the second area portions AR52a, AR52b, AR52c correspond to the second projection image data. Part. A curve CL41 shows the movement locus of the projection position of the point E11, and a curve CL42 shows the movement locus of the projection position of the point E12.

  In the present CT imaging, the rotation is reversed after the rotation angle reaches 180 + α degrees. For this reason, the movement locus of the projection position of each point in the CT imaging region RR1 is symmetric with respect to a line passing through the rotation angle 180 + α degrees on the sinogram shown in FIG. Therefore, when the first area AR51c and the second area AR52a are reversed about the line passing through the rotation angle 180 + α degrees, the first projection image data for 180 degrees is included in the range from 0 degrees to 180 + α degrees. The second projection image data for 180 degrees is included in the range from 180 + α degrees to 0. Thus, the dual energy scan can also be realized by the fifth CT imaging example.

<3. Third Embodiment>
<Sixth CT imaging example>
FIG. 19 is a schematic plan view for explaining a sixth CT imaging example in the X-ray imaging apparatus 100b according to the third embodiment. The X-ray imaging apparatus 100b according to the present embodiment includes an energy conversion unit 23b. The energy conversion unit 23b is a filter structure in which two types of filters 231b and 233b having different energy conversion characteristics are alternately arranged in the vertical direction (z-axis direction). In other words, the energy conversion unit 23b is configured by sequentially arranging the filter 231b, the filter 233b, the filter 231b, and the filter 233b sequentially from the −z side to the + z side. In order to distinguish each filter, it is assumed that the filter 231b1, the filter 233b1, the filter 231b2, and the filter 233b2 are in this order. Each filter 231b, the vertical width of 233b are unified by _{W 3.}

  19A shows a state where the rotation angle is 0 degree, FIG. 19B shows a state where the rotation angle is 180 + α degrees, and FIG. 19C shows a state where the rotation angle is 360 + 2α degrees.

In the present CT imaging, the X-ray generator 11 and the two-dimensional X-ray detector 21 are rotated 360 + 2α degrees around the center C1 of the CT imaging region RR1, and the energy conversion unit 23b is moved in the vertical direction (z-axis direction). . Specifically, as shown in the lower part of each of FIGS. 19A to 19C, the energy conversion unit 23 b is moved by the two-dimensional X-ray detector 21 in accordance with the rotation of the X-ray generator 11. It is lowered in the −z direction orthogonal to the direction (here, the −x direction. Although the rotational movement of the two-dimensional X-ray detector 21 is strictly an arc movement, it is considered to be a movement in the −x direction in general). The frame line FL1 indicates the range of the region where the X-ray cone beam BX1 is incident on the energy conversion unit 23b at each rotation angle. The amount of movement of the energy conversion unit 23b is proportional to the amount of change in the rotation angle. More specifically, in the present CT imaging, the amount of movement of the energy conversion unit 23b per degree of rotation angle is W ₃ / (180 + α). Therefore, the frame line FL1 at the positions of the filters 231b1 and 233b1 at the time of 0 degrees is relatively displaced to the positions of the filters 233b1 and 231b2 at the time of 180 + α degrees (FIG. 19B). reference). The amount of displacement is _{W 3.} Further, the frame line FL1 is relatively displaced to the positions of the filters 231b2 and 233b2 at the time of 360 + 2α degrees (see FIG. 19C).

Here, attention is paid to the movement of the filter 233b1. Filter 233b1 between the rotation angle of 0 degrees 180 degrees to the displacement of the displacement amount _{W 3,} further displacement of the displacement amount _{W 3} between 360 degrees rotation angle of 180 degrees. In the meantime, that is, between the rotation angles of 0 degrees and 180 degrees, the filter 233b1 or the filter 233b2 moves so as to occupy the remaining portion of the frame line FL1.

  The energy conversion unit 23b is also disposed in the housing 210 in the same manner as the energy conversion unit 23 in FIG. Since only the difference between the displacement drive configuration in the x direction and the displacement drive configuration in the z direction is omitted, the illustration is omitted.

  Attention is paid to points E11a, E11b, and E11m as representatives of the respective points in the CT imaging region RR1. Points E11a and E11b are points on the contour line that defines the CT imaging region RR1, and are contact points that are in contact with the outer edge on the −x side of the X-ray cone beam BX1 while the rotation angle advances from 0 degrees to 360 + 2α degrees. Therefore, the points E11a and E11b are points that move on the outer circle of the CT imaging region RR1 while the rotation angle proceeds from 0 degree to 360 + 2α degrees as seen from the Z-axis direction, and are not fixed points. The point E11a is a point at the −z side end (bottom) of the CT imaging region RR1, and the point E11b is a point at the + z side end (top) of the CT imaging region RR1. E11m is an intermediate point between the points E11a and E11b.

  The X-rays passing through the point E11a enter the point IE11a at the −x side end and the −z side end of the frame line FL1 in the lower part of each of FIGS. 19 (a) to 19 (c). Further, the X-ray passing through the point E11b is incident on the point IE11b at the −x side end and the + z side end of the frame line FL1. The X-ray passing through the point E11m is incident on an intermediate point IE11m between the point IE11a and the point IE11b on the frame line FL1.

  As is clear from FIG. 19, the point IE11a is included in the filter 231b1 between 0 degree and 180 + α degrees, and is included in the filter 233b1 between 180 + α degrees and 360 + 2α degrees. That is, X-rays passing through the point E11a are incident on the filter 231b from 0 degrees to 180 + α degrees, and are incident on the filter 233b between 180 + α degrees and 360 + 2α degrees. Accordingly, for the point E11a in the CT imaging region RR1, between 0 degrees and 180 + α degrees, 180 degrees (about another point at the same height in the z direction as the point E11a shown in FIG. 19A). Is obtained for the first projection image data of an angle exceeding 180 degrees, that is, at least 180 degrees, and between 180 + α degrees and 360 + 2α degrees, 180 degrees (more precisely, an angle exceeding 180 degrees, that is, Second projection image data of at least 180 degrees is acquired.

  The point IE11m is included in the filter 233b1 from 0 degree to 180 + α degrees, and is included in the filter 231b2 from 180 + α degree to 360 + 2α degrees. That is, X-rays passing through E11m are incident on the filter 233b from 0 degrees to 180 + α degrees, and are incident on the filter 231b between 180 + α degrees and 360 + 2α degrees. Therefore, for the point E11m in the CT imaging region RR1, between 0 degrees and 180 + α degrees, 180 degrees (about another point at the same height in the z direction as the point E11m shown in FIG. 19A). Can obtain second projection image data of an angle exceeding 180 degrees, that is, at least 180 degrees, and 180 degrees between 180 + α degrees and 360 + 2α degrees (more precisely, an angle exceeding 180 degrees) Min, ie, at least 180 degrees) of first projection image data can be acquired.

  For X-rays that pass through the point E11b and enter the point IE11b, the course of incidence on the filter 233b is followed by the filter 231b in the same order as the point E11a. The first projection image data (accurately, the angle exceeding 180 degrees) is acquired, and the second projection image data for 180 degrees is acquired between 180 + α degrees and 360 + 2α degrees. Detailed description is omitted.

  The X-ray cone beam BX1 transmitted through the energy conversion unit 23b is enlarged and received by the detection surface because the two-dimensional X-ray detector 21 is further away from the X-ray generator 11 than the energy conversion unit 23b. Here, the enlargement ratio is set to a ratio MG1. Further, an area RA1b where the X-ray cone beam BX1 is incident on the detection surface of the two-dimensional X-ray detector 21 is assumed. That is, the region RA1b is a region obtained by enlarging the frame line FL1 at a ratio of the ratio MG1.

  The regions of X-rays that pass through the regions of the filters 231b1, 233b1, 231b2, and 233b2 and are received on the detection surface of the two-dimensional X-ray detector 21 are defined as regions RA1b1, RA1b2, RA1b3, and RA1b4. Then, each of the regions RA1b1, RA1b2, RA1b3, and RA1b4 is obtained by enlarging each region of the filters 231b1, 233b1, 231b2, and 233b2 moving within the frame line FL1 at a ratio of MG1, and within the frame line FL1. It is similar to each region of the filters 231b1, 233b1, 231b2, and 233b2.

  Thus, the dual energy scan is also possible in this CT imaging example. Also in this CT imaging example, the boundary portions of the filters 231b, 233b, 231b, and 233b move during CT imaging. For this reason, the scattered X-rays of X-rays generated at the boundary portion can be reduced from being concentrated on a specific position of the two-dimensional X-ray detector 21. For this reason, the influence of the scattered X-ray on the CT image can be reduced.

<4. Fourth Embodiment>
FIG. 20 is a schematic perspective view showing an X-ray imaging apparatus 100c according to the fourth embodiment. In FIG. 20, in order to explain the internal structure of the X-ray imaging apparatus 100c, a part of the housing is cut away. Although not shown, the X-ray imaging apparatus 100c is supported while the subject is in a supine position (or prone position) on the table and is transported into the annular gantry 91 of the X-ray imaging apparatus 100c. Take a line.

  More specifically, an annular rotator 92 is rotatably provided in the gantry 91. An X-ray generator 11a, a two-dimensional X-ray detector 21a, and an energy conversion unit 23c are provided inside the rotating body 92. The detection surface 21Sa of the two-dimensional X-ray detector 21a is a curved surface that matches the curvature of the rotating body 92. The energy conversion unit 23c is a filter structure in which filters 231c and 233c having different energy conversion efficiencies are arranged adjacent to each other along the rotation direction of the rotating body 92. Moreover, the energy conversion part 23c is comprised so that a movement along the rotation direction of the rotary body 92 is possible by the energy conversion part moving mechanism 25a. The energy conversion unit moving mechanism 25a includes, for example, a motor 251a as a drive source that moves the energy conversion unit 23a, and a conduction unit 252a that transmits the rotational motion of the motor 251a to the energy conversion unit 23a. The conduction part 252a is configured by a roller body that contacts the energy conversion part 23a.

  Further, the energy conversion unit moving mechanism 25 a may include a rotation axis direction moving mechanism that allows the energy conversion unit 23 c to move along the rotation axis Q orthogonal to the rotation direction of the rotating body 92. The rotation axis direction moving mechanism is constituted by, for example, a ball screw 95 and a motor 96 that rotates the ball screw. In addition, you may employ | adopt a linear motor etc. for the moving mechanism of the energy conversion part 23a.

  Also in the X-ray imaging apparatus 100c, the rotating body 92 rotates around the rotation axis Q during X-ray imaging, as in the first to fifth CT imaging examples described in the first or second embodiment. Thus, CT imaging is performed by rotating the X-ray generator 11a, the two-dimensional X-ray detector 21a, and the energy conversion unit 23c. Further, the energy conversion unit moving mechanism 25a traverses the energy conversion unit 23c across the X-ray cone beam emitted from the X-ray generator 11a and in a direction along the detection surface 21S of the two-dimensional X-ray detector 21a. Move appropriately. Thereby, the first projection image data for 180 degrees through the filter 231c and the second projection image data for 180 degrees through the filter 231c can be acquired for the CT imaging region. Also, during CT imaging, the X-ray diffused at the boundary between the filters 231c and 233c is moved to a specific position of the two-dimensional X-ray detector 21a by moving the energy conversion unit 23c so as to cross the X-ray cone beam. Concentrated incidents can be reduced. For this reason, the influence of the scattered X-ray on the CT image can be reduced.

  In the present embodiment, the filter configuration of the energy conversion unit 23c may be a plurality of filters arranged in a striped pattern like the energy conversion units 23a and 23b illustrated in FIG. 11 or FIG.

<5. Modification>
Although the embodiment has been described above, the present invention is not limited to the above, and various modifications are possible.

  FIG. 21 is a schematic front view showing an energy conversion unit 23d according to a modification. The energy conversion unit 23d includes a first portion and a second portion that have different conversion characteristics of the X-ray energy distribution. More specifically, the first portion is provided with a filter 231d, and the second portion is provided with a filter 233d.

  As shown in an enlarged manner in FIG. 21, in the filter 231d, two filter portions 2311 and 2313 having different X-ray energy distribution conversion characteristics are arranged in a checkered pattern. In other words, in the filter 231d, a large number of filter parts 2311 and 2313 are alternately arranged without gaps in the x-axis direction and the z-axis direction.

  When projection image data is collected using such an energy conversion unit 23d, the X-rays transmitted through the filter 231d are classified into those obtained by converting the energy distribution by the filter unit 2311 and those converted by the filter unit 2313. Will be included. For each of the X-rays transmitted through the filter unit 2311 and the X-rays transmitted through the filter unit 2313, the incident positions in the two-dimensional X-ray detector are the X-ray generator 11, the filter 231d, and the two-dimensional X-ray detector. It can be identified from the positional relationship. Therefore, the projection image data based on the X-rays incident on all the filter units 2311 and the projection image data based on the X-rays transmitted through all the filter units 2313 can be obtained separately. Therefore, two types of CT images can be acquired for the same tomographic plane based on these two types of projection image data having different energy distribution characteristics.

  The energy conversion unit according to the above embodiment has a filter configuration having two parts with different conversion characteristics. However, a filter configuration having three or more portions with different conversion characteristics may be used. In this case, during CT imaging, the energy conversion unit is moved, and X-rays transmitted through the CT imaging region are detected by a two-dimensional X-ray detector through three or more parts, thereby obtaining an energy distribution. A multi-energy scan that acquires three or more projection image data having different characteristics from each other can be performed.

  The X-ray imaging apparatus 100 according to the above-described embodiment has been described with respect to the case where CT imaging is performed on the head (particularly the jaw) of the subject M1. Even in this case, the present invention is effective. In the X-ray imaging apparatus 100 and the like according to the above embodiment, the X-ray generator 11 and the two-dimensional X-ray detector 21 have a constant height with respect to the subject M1 (specifically, the body of the subject M1) during CT imaging. It rotates in a state where the position in the axial direction (Z-axis direction) is constant. However, in the X-ray imaging apparatus according to the present invention, the X-ray generator and the two-dimensional X-ray detector rotate in a relatively spiral shape by rotating while relatively changing the position of the subject M1 in the body axis direction. It may be configured to rotate.

  Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention. In addition, the configurations described in the above embodiments and modifications can be appropriately combined or omitted as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 100,100a, 100b, 100c X-ray imaging apparatus 1 Main-body part 10 X-ray generation part 11, 11a X-ray generator 12 Irradiation field control part (X-ray control part)
12a Slit plate 20 X-ray detector 210 Case 21, 21a Two-dimensional X-ray detector 21S, 21Sa Detection surface 23, 23a, 23b, 23c, 23d Energy conversion unit 231, 231a, 231b, 231c, 231d Filter 233, 233a , 233b, 233c, 233d Filter 2311, 2313 Filter part 235 Boundary part 25, 25a Energy conversion part moving mechanism 251, 251a Motor 252, 252a Transmission part 30 Support arm 300 Support part 31 Rotating shaft 43 Cefarostat 60 Main body control part 601 CPU
601a X-ray generation unit control unit 601b X-ray detection unit control unit 65 turning mechanism 8 information processing apparatus (image processing apparatus)
801b Image generation unit 91 Gantry 92 Rotating body BX1, BX2 X-ray cone beam C1 Center DA Tooth group M1 Subject PG1, PG2 Program Q, RA Rotation axis RR1, RR2 CT imaging region

Claims (19)

An X-ray generator comprising an X-ray generator for generating an X-ray beam;
An X-ray detector comprising a two-dimensional X-ray detector that receives and detects the X-ray beam irradiated from the X-ray generator and transmitted through the subject;
A support unit that supports the X-ray generation unit and the X-ray detection unit while maintaining an opposing state;
A moving mechanism for turning the support unit with respect to the subject in a state where the X-ray generation unit and the X-ray detection unit sandwich the subject.
A first part and a second part, which are interposed between the object in the path of the X-ray beam and the two-dimensional X-ray detector and have different conversion characteristics of the energy distribution of the X-ray beam, are two-dimensionally arranged. An energy conversion unit,
In X-ray imaging, during said pivoting of the supporting portion, wherein the energy conversion unit and Tsu along the detection surface of the two-dimensional X-ray detector so as to cross the X-ray beam, the two-dimensional X-ray An energy conversion unit moving mechanism for moving the detector in the moving direction or in the opposite direction;
An X-ray imaging apparatus comprising:   An X-ray generator comprising an X-ray generator for generating an X-ray beam;
  An X-ray detector comprising a two-dimensional X-ray detector that receives and detects the X-ray beam irradiated from the X-ray generator and transmitted through the subject;
  A support unit that supports the X-ray generation unit and the X-ray detection unit while maintaining an opposing state;
  A moving mechanism for turning the support unit with respect to the subject in a state where the X-ray generation unit and the X-ray detection unit sandwich the subject.
  A first part and a second part, which are interposed between the object in the path of the X-ray beam and the two-dimensional X-ray detector and have different conversion characteristics of the energy distribution of the X-ray beam, are two-dimensionally arranged. An energy conversion unit,
  In X-ray imaging, the two-dimensional X-ray detection is performed along the detection surface of the two-dimensional X-ray detector so that the energy conversion unit traverses the X-ray beam while the support unit is turning. An energy conversion unit moving mechanism that moves in a direction crossing the moving direction of the vessel;
An X-ray imaging apparatus comprising: The X-ray imaging apparatus according to claim 1 or 2 ,
The X-ray imaging apparatus, wherein the energy conversion unit includes a first filter structure having a filter in the first part and no filter in the second part. The X-ray imaging apparatus according to claim 1 or 2 ,
The energy conversion unit includes a second filter structure including a first filter in the first part and a second filter having a conversion characteristic different from that of the first filter in the second part. X-ray imaging device. The X-ray imaging apparatus according to any one of claims 1 to 4 ,
The energy conversion unit moving mechanism is
A motor as a drive source for moving the energy conversion unit;
A transmission for transmitting the movement of the motor;
An X-ray imaging apparatus. The X-ray imaging apparatus according to claim 1 ,
The direction parallel to the axial direction of the turning axis around which the support part turns is defined as the z direction, the direction orthogonal to the z direction, and the direction in which the X-ray generation part and the X-ray detection part face each other is defined as the y direction. When the direction orthogonal to the y direction is the x direction,
The energy conversion unit moving mechanism is
An X-ray imaging apparatus that moves the energy conversion unit in the x direction at a position between the two-dimensional X-ray detector and the subject. The X-ray imaging apparatus according to claim 6 ,
The X-ray imaging performed by the X-ray imaging apparatus is CT imaging,
An X-ray imaging apparatus in which the first part and the second part are arranged in a striped pattern. The X-ray imaging apparatus according to claim 6 ,
The X-ray imaging performed by the X-ray imaging apparatus is CT imaging,
An X-ray imaging apparatus, wherein the first part and the second part are arranged in a checkered pattern. The X-ray imaging apparatus according to claim 7 or 8 ,
An X-ray imaging apparatus, wherein the energy conversion unit moving mechanism is disposed in a housing of the X-ray detection unit. The X-ray imaging apparatus according to claim 8,
The energy conversion unit, to the dynamic shift Te the housing smell of the X-ray detector, X-ray imaging apparatus. The X-ray imaging apparatus according to any one of claims 1 to 10,
An X-ray restricting section for restricting X-rays emitted from the X-ray generator;
Further comprising
An X-ray imaging apparatus in which the X-ray is formed into an X-ray cone beam by the X-ray restricting unit. The X-ray imaging apparatus according to claim 11,
The X-ray imaging performed by the X-ray imaging apparatus is CT imaging,
The X-ray imaging apparatus, wherein the energy conversion unit moving mechanism retracts the energy conversion unit from a position where the X-ray cone beam transmitted through a CT imaging region is incident. The X-ray imaging apparatus according to claim 11 or 12,
An X-ray imaging apparatus that performs panoramic X-ray imaging or cephalometric imaging using an X-ray slit beam formed by the X-ray restricting unit. The X-ray imaging apparatus according to claim 2 ,
During CT imaging, the energy conversion unit moving mechanism moves the energy conversion unit,
While the support portion performs a rotation in which the fan angle of the X-ray beam is added to the half rotation, at least one of the first portion and the second portion is displaced by the width of the one in the intersecting direction. And while the support portion further performs a turn by adding a fan angle of the X-ray beam to a half rotation, the one portion is further displaced by the width in the intersecting direction, and the first portion and the second portion An X-ray imaging apparatus in which the other of the X-rays receives the X-rays of the remaining part excluding the part incident on the one of the X-ray beams. The X-ray imaging apparatus according to claim 10,
During CT imaging, the energy conversion unit moving mechanism moves the energy conversion unit,
During rotation of the support part,
The first portion is displaced by the width in the moving direction of the X-ray detection unit,
The X-ray imaging apparatus, wherein the second portion is displaced by a displacement amount that coincides with a displacement amount of the first portion in a direction in which the first portion is displaced simultaneously with the displacement of the first portion. An image processing apparatus for processing image data acquired by the X-ray imaging apparatus according to any one of claims 1 to 15,
The image data obtained by transmitting or passing through each of the first part and the second part of the energy conversion unit and detecting the X-ray beam by the two-dimensional X-ray detector is subjected to image processing, and each energy distribution An image processing unit for generating an X-ray image corresponding to the characteristics;
An image processing apparatus comprising: The image processing apparatus according to claim 16.
The image processing device, wherein the image processing unit acquires a difference image of the image data corresponding to each energy distribution characteristic by calculation. X-ray imaging method,
A rotation step of rotating an X-ray generator for generating an X-ray beam and a two-dimensional X-ray detector for detecting the X-ray beam transmitted through the subject around the subject in an opposed state;
During the rotation step, the first part and the second part are interposed between the subject in the X-ray beam path and the two-dimensional X-ray detector, and have different conversion characteristics of the energy distribution of the X-ray beam. portion of the energy conversion unit in which a two-dimensionally arrayed, and Tsu along the detection surface of the two-dimensional X-ray detector so as to cross the X-ray beam, the moving direction of the two-dimensional X-ray detector Or an energy conversion unit moving step for moving in the opposite direction;
An X-ray imaging method including:   The X-ray imaging apparatus according to any one of claims 1 to 15,
  The energy conversion unit moving mechanism moves the energy conversion unit so that the amount of movement of the energy conversion unit is proportional to the amount of change in the rotation angle of the support unit rotated by the movement mechanism. .

Images