X-ray CT imaging apparatus

An X-ray CT imaging apparatus includes: a supporter that is supported such that an X-ray generator and an X-ray detector are opposed to each other; a turning motor that turns the supporter about a shaft; a crosswise drive motor that moves the shaft in a crosswise direction; and a circuit that performs processing of controlling the turning motor and the crosswise drive motor and processing of setting the physique of a subject. When X-ray CT imaging is performed, the crosswise drive motor moves the shaft in synchronization with turning of the supporter about the shaft, and the supporter is caused to perform combined motion, which allows the X-ray generator and the X-ray detector to turn about a center of an X-ray CT imaging region, and position control of the shaft is performed according to the size of the physique of the subject.

TECHNICAL FIELD

The present disclosure relates to an X-ray CT imaging apparatus that performs X-ray imaging by rotating an X-ray generator and an X-ray detector around a subject.

BACKGROUND ART

Japanese Patent Application Laid-Open No. 2007-029168 discloses an X-ray CT imaging apparatus including a turning mechanism and a moving mechanism. The turning mechanism turns turning means, in which the X-ray generator and the X-ray detector are disposed opposite to each other while the subject is sandwiched therebetween, around a turning axis. The moving mechanism moves the turning axis and/or the subject in a plane perpendicular to the turning axis. In the X-ray CT imaging apparatus, the turning means is turned by combined motion of the turning of the turning unit and the turning axis and/or the movement of the subject while a center of a region of interest of the subject is always set to a rotation center on the imaging different from the turning axis of the turning mechanism. Consequently, a magnification ratio can be changed by relatively changing a distance between the X-ray generator and the rotation center and/or a distance between the X-ray detector and the rotation center.

BRIEF SUMMARY

The subject of X-ray imaging has various sizes.

In Japanese Patent Application Laid-Open No. 2007-029168, because the size of the subject is not taken into consideration, there is a possibility that the X-ray generator and the X-ray detector turning around the subject contact with the subject.

An object of the present disclosure is to prevent the X-ray generator and the X-ray detector that turn around the subject from contacting with the subject.

An X-ray CT imaging apparatus according to one aspect includes: a supporter that is supported such that an X-ray generator and an X-ray detector are opposed to each other with a subject sandwiched between the X-ray generator and the X-ray detector; a turning motor that turns the supporter about a shaft located between the X-ray generator and the X-ray detector; a crosswise drive motor that moves the shaft in a crosswise direction, a direction parallel to an axial direction of the shaft being set to a longitudinal direction, a direction intersecting with the longitudinal direction being set to the crosswise direction; and a circuit that performs processing of controlling the turning motor and the crosswise drive motor and processing of setting a physique of the subject from physique data of the subject. When X-ray CT imaging is performed by irradiating the subject with an X-ray generated from the X-ray generator, the crosswise drive motor moves the shaft in synchronization with turning of the supporter about the shaft using the turning motor, and the supporter is caused to perform combined motion, which allows the X-ray generator and the X-ray detector to turn about a center of an X-ray CT imaging region, and position control of the shaft is performed according to a size of the physique of the subject.

DETAILED DESCRIPTION

First Embodiment

A medical X-ray CT imaging apparatus according to a first embodiment will be described below.FIG. 1is a schematic diagram illustrating an X-ray CT imaging apparatus10.

The X-ray CT imaging apparatus10is an apparatus that performs X-ray computed tomography (CT) imaging of a subject P, and includes a turning support20, a turning drive mechanism30, a subject physique setting unit40, and a turning controller60.

The turning support20supports an X-ray generator22and an X-ray detector24such that the X-ray generator22and the X-ray detector24are opposed to each other with a subject P sandwiched therebetween. The turning support20can be called a supporter that supports the X-ray generator22and the X-ray detector24. The X-ray generator22generates an X-ray (X-ray beam). The X-ray detector24detects the X-ray emitted from the X-ray generator22. The X-ray generator22and the X-ray detector24are supported by the turning support20while a space where the subject P is disposed between the X-ray generator22and the X-ray detector24is provided. The X-ray emitted from the X-ray generator22is incident on the X-ray detector24through the subject P. The X-ray incident on the X-ray detector24is converted into an electric signal corresponding to intensity of the X-ray in each unit pixel. The X-ray CT image or the like is generated based on each electric signal.

The turning drive mechanism30includes a turning mechanism32and a turning axis moving mechanism38.

The turning mechanism32turns the turning support20about a mechanical turning axis X1located between the X-ray generator22and the X-ray detector24. An example of the mechanical turning axis X1is an axis of a shaft about which the turning support20turns. In this case, it can be said that the turning mechanism32turns about the shaft. For example, the turning mechanism32includes an electric motor, and includes an acceleration and deceleration mechanism such as a gear as necessary. The turning mechanism32rotatably supports a shaft33protruding from the turning support20at a position between the X-ray generator22and the X-ray detector24. The shaft33is an example of the shaft. A center axis of the shaft33constitutes the mechanical turning axis X1. The turning support20turns about the mechanical turning axis X1by driving the turning mechanism32. The turning mechanism32can have any configuration as long as the turning mechanism32turns the turning support20about the mechanical turning axis X1.

The turning axis moving mechanism38moves the mechanical turning axis X1in a direction intersecting with the mechanical turning axis X1. For example, the turning axis moving mechanism38is constructed with an XY-stage mechanism and the like. The XY-stage mechanism is a combination of two sets of linear actuators with moving directions of the linear actuators intersecting with each other. A linear moving mechanism in which a linear guide and a ball screw feed mechanism are combined, a linear motor, and a linear motor such as an air cylinder can be used as the linear actuator. The moving direction of each of the two sets of linear actuators of the XY-stage mechanism is set to intersect with the mechanical turning axis X1, and the turning mechanism32is supported so as to be able to be moved in the moving direction of each of the two sets of linear actuators. Consequently, the turning mechanism32can be moved along a plane intersecting with the mechanical turning axis X1, and therefore the mechanical turning axis X1can be moved along the plane intersecting with the mechanical turning axis X1.

The turning axis moving mechanism38is not limited to the above example, but any turning axis moving mechanism that moves the mechanical turning axis X1in the direction intersecting with the mechanical turning axis X1can be used.

In the X-ray CT imaging apparatus10, in performing the X-ray CT imaging in which the subject P is irradiated with the X-rays generated from the X-ray generator22, the turning axis moving mechanism38moves the mechanical turning axis X1in synchronization with the turning of the turning support20about the mechanical turning axis X1using the turning mechanism32, and the turning support20is caused to perform combined motion, which allows the X-ray generator22and the X-ray detector24to be turned around the center of an X-ray CT imaging region R. The case that the X-ray generator22and the X-ray detector24are turned around a center A of the imaging region R includes the case that the X-ray generator22and the X-ray detector24are turned while drawing a circular trajectory around the center A and the case that the X-ray generator22and the X-ray detector24are turned while drawing a trajectory other than a circle.

The subject physique setting unit40is configured to be able to set the size of the physique of the subject P. The size of the physique of the subject P is set to the turning controller60. Information that becomes a base in setting the size of the physique of the subject P using the subject physique setting unit40can be obtained by receiving an input operation performed by an operator of the X-ray CT imaging apparatus10. Alternatively, the information can be transmission X-ray image data obtained by previously imaging the subject P using the X-ray generator22and the X-ray detector24. Alternatively, the information can be visible light image data obtained by imaging the subject P using an imager such as a CCD camera. Alternatively, the information can be data based on a signal output from a sensor or the like provided in the subject holder holding the subject P. That is, information input after a judgment by a person, data based on output signals of various sensors that output signals according to the physique of the subject P, and the like can be used as the above information, and the subject physique setting unit40sets the size of the physique of the subject P based on the information.

The turning controller60controls the turning mechanism32and the turning axis moving mechanism38. In particular, the turning controller60performs position control of the turning axis X1according to a size of the physique of the subject P set by the subject physique setting unit40.

The turning controller60includes at least one processor. For example, the turning controller60is constructed with a computer including at least one processor, a Random Access Memory (RAM), a storage, and an input and output unit. The storage is constructed with a flash memory or a nonvolatile storage device such as a hard disk drive, and stores a turning control program in controlling the turning mechanism32and the turning axis moving mechanism38. The RAM serves as a work area when at least one processor performs predetermined processing. The input and output unit is connected to the turning mechanism32, the turning axis moving mechanism38, the subject physique setting unit40, and the like. Then, at least one processor performs predetermined arithmetic processing according to the turning control program stored in the storage, and controls the turning mechanism32and the turning axis moving mechanism38according to the set physique of the subject P. Because the processor and the RAM include a circuit or are connected to each other by a circuit, the turning controller60is an element mechanically constructed with a circuit. The turning controller60is a circuit that mechanically processes the turning control according to a program. Similarly, the subject physique setting unit40is a circuit that performs processing of setting the physique of the subject from physique data of the subject according to the program.

FIG. 2is a flowchart illustrating processing performed by the turning controller60.

That is, in step S1, the physique of the subject P is set in performing the X-ray CT imaging.

In step S2, a turning control content according to the size of the physique of the subject P is decided.

The turning control content includes information about position control such as how to control the position of the mechanical turning axis X1in turning the X-ray generator22and the X-ray detector24around the center of the X-ray CT imaging region R. The following example can be considered as an example of the position control of the mechanical turning axis X1. In the first position control example, the turning axis moving mechanism38moves the mechanical turning axis X1in synchronization with the turning of the turning support20about the mechanical turning axis X1using the turning mechanism32. In this case, the turning axis moving mechanism38can turn the mechanical turning axis X1around the X-ray CT imaging region R in synchronization with the turning of the turning support20about the mechanical turning axis X1using the turning mechanism32. At this point, the turning axis moving mechanism38can rotate the mechanical turning axis X1with the center A of the X-ray CT imaging region R as the rotation center. In the second position control example, the mechanical turning axis X1is fixed to the center A of the X-ray CT imaging region R when the turning mechanism32turns the turning support20about the mechanical turning axis X1.

By switching the position control of the mechanical turning axis X1between the first position control example and the second position control example, the trajectory along which the X-ray generator22and the X-ray detector24turn can be changed so as to be moved away from or brought close to the X-ray CT imaging region R. Alternatively, by changing the position (distance) of the mechanical turning axis X1to the center A of the X-ray CT imaging region R, the trajectory along which the X-ray generator22and the X-ray detector24turn can be changed so as to be moved away from or brought close to the X-ray CT imaging region R. These position control examples are more specifically described in a second embodiment.

By combining the position control examples, the trajectory along which the X-ray generator22and the X-ray detector24turn can be changed in multiple stages so as to be moved away from or brought close to the X-ray CT imaging region R.

The X-ray CT imaging region R is a region that is set as a target of the X-ray CT imaging in the subject P. The X-ray CT imaging region R can be a whole or a part of the subject P. The X-ray CT imaging region R can be a previously-defined region as a predetermined region of the subject P, or a region set by the operator or the like each time the CT imaging is performed. Hereinafter, sometimes the X-ray CT imaging region R is simply referred to as an imaging region R.

As described above, when the X-ray generator22and the X-ray detector24are turned around the center A of the imaging region R, the turning axis moving mechanism38controls the position of the mechanical turning axis X1with respect to the center A of the imaging region R according to the size of the physique.

As an example, it is assumed that D1is a distance between the center A of the imaging region R and the X-ray generator22, that D2is a distance between the center A of the imaging region R and the X-ray detector24, and that a separation distance D is a smaller one of the two distances D1, D2. The case that the physique of the subject P set by the subject physique setting unit40is a first physique P(L) and the case that the physique of the subject P is a second physique P(M) smaller than the first physical constitution P(L) are assumed. The position of the mechanical turning axis X1is controlled such that the separation distance D when the set physique of the subject P is the relatively large first physique P(L) is greater than the separation distance D when the set physique of the subject P is the relatively small second physique P(M) according to the size of the physique of the subject P set by the subject physique setting unit40.

When the size inFIG. 1is described as an example, because the center A of the imaging region R is located closer to the X-ray detector24than the X-ray generator22, the separation distance D is the distance D2between the center A of the imaging region R and the X-ray detector24. Assuming that the position control of the mechanical turning axis X1is performed according to the size of the physique, the separation distance for the relatively large first physique P(L) is set to D(L), and the relatively small second physique P(M) is set to D(M). In this case, the separation distance D(L) for the relatively large first physique is increased larger than the separation distance D(M). When the separation distance D(L) is increased, the X-ray generator22approaches the center A of the imaging region R, but it is assumed that the separation distance D(L) is set to a range less than or equal to D1of the adjusted distance, namely, a range in which the X-ray generator22is not brought closer to the center A of the imaging region R than the X-ray detector24.

For the relatively small second physique P(M), the X-ray detector24is turned with a radius corresponding to the relatively small separation distance D(M). For this reason, the X-ray detector24can be turned while brought as close as possible to the second physique P(M). The X-ray generator22turns a position farther from the center A of the imaging region R than the X-ray detector24, namely, the X-ray generator22turns such that a degree of separation with respect to the center A is larger than a degree of separation with respect to the center A of the X-ray detector24.

For the relatively large first physique P(L), the X-ray detector24is turned with a radius corresponding to the relatively large separation distance D(L). Consequently, the X-ray detector24can be turned without interfering with the first physique P(L). The X-ray generator22turns a position farther from the center A of the imaging region R than the X-ray detector24, namely, the X-ray generator22turns such that a degree of separation with respect to the center A is larger than a degree of separation with respect to the center A of the X-ray detector24.

For example, the turning control content of the mechanical turning axis X1according to the size of the physique can be decided by referring to the reference table previously stored in the storage according to the set sizes of a plurality of physiques. For example, the reference table can be set to a table in which the turning control content of the turning axis X1is associated with each of the plurality of physiques.

When the second position control example is assumed, the turning control content is defined as fixing of the mechanical turning axis X1to a fixed position. When the first position control example is assumed, the turning control content is defined as a pattern moving the mechanical turning axis X1around the center A of the imaging region R. A more specific example is a pattern in which the mechanical turning axis X1is rotated with a predetermined axis turning radius as the center A of the imaging region R as a rotation center. The predetermined axis turning radius can be a value previously set according to the size of the physique. The turning control content (for example, the predetermined axis turning radius) can be obtained each time by calculation using a previously-set arithmetic expression or the like according to the value representing the set sizes of the plurality of physiques. Consequently, the turning control content including the position control of the turning axis X1is decided.

In step S3, the turning controller60controls the turning mechanism32and the turning axis moving mechanism38based on the decided turning control content, and the X-ray generator22and the X-ray detector24are turned around the center A of the imaging region R of the subject P. At this point, the X-rays emitted from the X-ray generator22is incident on the X-ray detector24through the subject P, and data used to generate the X-ray CT image is obtained. The X-ray CT image is generated based on this data.

In the X-ray CT imaging apparatus10configured as described above, the position control of the turning axis X1is performed according to the size of the physique of the subject P set by the subject physique setting unit40, so that the X-ray generator22and the X-ray detector24that turn around the subject P can be prevented from contacting with the subject P by changing the turning orbits of the X-ray generator22and the X-ray detector24.

The position control of the turning axis X1is performed according to the size of the physique of the subject P to change the turning orbits of the X-ray generator22and the X-ray detector24, so that the X-ray CT imaging can be performed by bringing the X-ray detector24as close as possible to the subject P while the contact of the X-ray detector24with the subject P is prevented. Consequently, the clear X-ray image can be generated.

Second Embodiment

An X-ray CT imaging apparatus according to a second embodiment will be described.

FIG. 3is a schematic diagram illustrating an entire configuration of an X-ray CT imaging apparatus110. An example in which the X-ray CT imaging apparatus110can perform not only the X-ray CT imaging but also panoramic imaging, cephalogram imaging, and the like will be described. An example in which the subject of the X-ray CT imaging apparatus110is the head P of a human body will be described.

The X-ray CT imaging apparatus110includes an imaging main body120and an X-ray image processing apparatus180. The imaging main body120is an apparatus that performs the X-ray imaging such as the X-ray CT imaging to collect projection data. The X-ray image processing apparatus180is an apparatus that processes the projection data collected by the imaging main body120and generates various images.

The imaging main body120includes a turning support124and a turning drive mechanism130. The turning support124supports an X-ray generator126and an X-ray detector128such that the X-ray generator126and the X-ray detector128are opposed to each other with the head P sandwiched therebetween. The turning support124can be called a supporter that supports the X-ray generator126and the X-ray detector128. The turning drive mechanism130includes a turning mechanism132and a turning axis moving mechanism134. The turning mechanism132is a mechanism that turns the turning support124about the mechanical turning axis X1between the X-ray generator126and the X-ray detector128. The turning axis moving mechanism134is a mechanism that moves the mechanical turning axis X1in a direction intersecting with the mechanical turning axis X1. An example of the mechanical turning axis X1is an axis of a shaft about which the turning support20turns. In this case, it can be said that the turning mechanism32turns about the shaft.

More specifically, a post121is supported in a perpendicular posture on a base120B. A lifting unit122is liftably provided on the post121. A lifting drive mechanism moves the lifting unit122up and down. A moving mechanism including a ball screw mechanism and a motor and a linear actuator such as a linear motor are used as the lifting drive mechanism, and the lifting drive mechanism moves the lifting unit122up and down while being incorporated in the post121. A horizontal arm123is supported by the lifting unit122so as to extend in a horizontal direction. A turning drive mechanism130is incorporated at a leading end of the horizontal arm123. A head fixing apparatus arm141(to be described later) extends from the post121in the same direction as the horizontal arm123. A head fixing apparatus142is provided at the leading end of the head fixing apparatus arm141, and the head P is held by the head fixing apparatus142. InFIG. 3, a base end of the lifting unit122moves up and down behind the post121. Assuming that the side on which the base end of the lifting unit122moves up and down is a back face and that a reverse of the back face is a front face, the horizontal arm123extends from the lifting unit122to the right of the post121in front view ofFIG. 3. The head P is held in the head fixing apparatus142with the right inFIG. 3as the rear and with the left as the front.

At this point, the direction is defined for convenience.

An XYZ-orthogonal coordinate system is an orthogonal coordinate system defined in a three-dimensional space in which the imaging main body120is installed. A direction parallel to the axial direction of the mechanical turning axis X1is set to a Z-axis direction. In the second embodiment, the direction parallel to the axial direction of the mechanical turning axis X1and the lifting direction of the lifting unit122are matched with each other as the Z-axis direction. A direction orthogonal to the Z-axis direction is set to a Y-axis direction, and a direction orthogonal to the Z-axis direction and the Y-axis direction is set to an X-axis direction. A front-rear direction of the head P fixed to the head fixing apparatus142is set to the Y-axis direction, and a right and left direction of the head P is set to the X-axis direction.

In the present disclosure, sometimes the Z-axis direction is referred to as a Z-direction, the Y-axis direction is referred to as a Y-direction, and the X-axis direction is referred to as an X-direction. The Z-axis direction can be considered as a longitudinal direction, and the X-direction and the Y-direction can also be considered as a crosswise direction. The longitudinal direction can be a vertical direction, and the Y-direction can be a horizontal direction.

The direction from the head P toward the base120B, namely, a lower side is set to a −Z-side, and the direction away from the base120B from the head P, namely, an upper side is set to a +Z-side. The front side of the head P is set to a +Y-side, and the rear side is set to a −Y-side. The right side of the head P is set to an +X-side, and the left side is set to an −X-side. Each axial direction, “+”, and “−” are illustrated inFIG. 3.

An xyz-orthogonal coordinate system is an orthogonal coordinate system defined in the turning support124constituting an imaging system that performs the X-ray generation and the X-ray detection, the imaging system rotating around the mechanical turning axis X1. At this point, the axial direction of the mechanical turning axis X1is set to a z-axis direction, and the z-axis direction is matched with the Z-axis direction of the XYZ-orthogonal coordinate system. A direction in which the X-ray generator126and the X-ray detector128are opposed to each other is set to a y-axis direction, and a direction orthogonal to the y-axis direction and the z-axis direction is set to an x-axis direction. The turning support124rotates with the mechanical turning axis X1as the rotation axis, which allows the xyz-orthogonal coordinate system to rotate around the Z-axis (=z-axis) with respect to the XYZ-orthogonal coordinate system. In the present disclosure, sometimes the z-axis direction is referred to as a z-direction, the y-axis direction is referred to as a y-direction, and the x-axis direction is referred to as an x-direction.

In the y-axis direction, the side of the X-ray detector128is set to a +y-side, and the side of the X-ray generator126is set to a −y-side. In the x-axis direction, the right side from the −y-side toward the +y-side is set to a +x-side, and the left side is set to a −x-side. In the z-axis direction, the upper side in the vertical direction is set to a +z-side, and the lower side is set to a −z-side.

FIG. 4is a schematic bottom view illustrating the turning drive mechanism130. As illustrated inFIGS. 3 and 4, the turning drive mechanism130includes a turning axis moving mechanism134supported by the horizontal arm123as a kind of bracket and a turning mechanism132supported movably by the turning axis moving mechanism134.

The turning axis moving mechanism134is a mechanism that moves the mechanical turning axis X1in the direction intersecting with the mechanical turning axis X1, in this case, the direction orthogonal to the mechanical turning axis X1. The turning axis moving mechanism134is constructed with an XY-table mechanism, and the mechanical turning axis X1is moved in the direction intersecting with the mechanical turning axis X1by moving the turning mechanism132to which the mechanical turning axis X1is connected in the direction intersecting withe the mechanical turning axis X1. More specifically, the turning axis moving mechanism134includes a fixed table134B, an X-direction movable support135, an X-direction drive unit136, a Y-direction movable support137, a Y-direction drive unit138, and a movable table139.

The X-direction movable support135includes a pair of linear guides135aextending in the X-direction, the linear guides135abeing supported on the fixed table134B in a spaced and parallel state. The Y-direction movable support137includes a pair of linear guides137aextending in the Y-direction. The pair of linear guides137aare movably supported on the pair of linear guides135aalong the X-direction that is the extending direction while having a posture intersecting with the pair of linear guides135a(in this case, a posture orthogonal to the pair of linear guides135a) in the spaced and parallel state. The movable table139is supported on the pair of linear guides137aso as to be movable along the Y-direction that is the extending direction. The Y-direction movable support137moves along the X-direction on the X-direction movable support135, which allows the movable table139to move in the X-direction. The movable table139moves along the Y-direction on the Y-direction movable support137, which allows the movable table139to move in the Y-direction. Consequently, the movable table139can move freely in a plane orthogonal to the mechanical turning axis X1.

The X-direction drive unit136is a mechanism that reciprocally drives the Y-direction movable support137along the X-direction. For example, a ball screw mechanism in which a nut136cfixed to the Y-direction movable support137is screwed to a ball screw136brotationally driven in both forward and reverse directions by a motor136acan be used as the X-direction drive unit136.

The Y-direction drive unit138is a mechanism that reciprocally drive the movable table139along the Y-direction. For example, a ball screw mechanism in which a nut138cfixed to the movable table139is screwed to a ball screw138brotationally driven in both the forward and reverse directions by a motor138acan be used as the Y-direction drive unit138.

The turning mechanism132includes a motor132a,and is supported in a suspended state by the movable table139. A shaft124cprotruding upward from an intermediate portion in the extending direction of the turning support124is supported in the suspended state by the turning mechanism132. The shaft124cis an example of the shaft. The rotating movement of the motor132ais transmitted to the shaft124c,and the turning support124is turned about the shaft124cby driving the motor132a.The central axis of the shaft124cis the mechanical turning axis X1located between the X-ray generator126and the X-ray detector128. The rotating movement of the motor132ais transmitted to the shaft124cthrough a transmission mechanism such as a gear and a pulley as necessary. The shaft124cis disposed along the vertical direction along a direction of gravity. Thus, the mechanical turning axis X1is also disposed along the vertical direction.

The turning mechanism132supported by the movable table139can be moved along the plane orthogonal to the mechanical turning axis X1by driving the X-direction drive unit136and the Y-direction drive unit138. In particular, by combining the drive in the X-direction by the X-direction drive unit136and the drive in the Y-direction by the Y-direction drive unit138, the turning mechanism132can be rotationally moved so as to draw an arc-shaped orbit.

The mechanism that moves the movable table139in the X-direction and the mechanism that moves the movable table139in the Y-direction are not limited to the above examples, but a configuration using a linear actuator such as a linear motor can be adopted. The turning axis moving mechanism134does not necessarily have the above configuration. The turning axis moving mechanism can be a mechanism that moves the turning mechanism only along one linear direction intersecting with the mechanical turning axis X1. The turning axis moving mechanism can be a mechanism, such as a robot arm including a plurality of joints, which turns an arm supporting the turning mechanism, thereby turning the turning mechanism in the direction intersecting with the mechanical turning axis X1. The turning axis moving mechanism134can move the mechanical turning axis X1in a two-dimensional direction intersecting with the axial direction of the mechanical turning axis X1. The intersection can be orthogonal intersection.

The motor132ais a turning motor. When the axis of the shaft is assumed as the mechanical turning axis X1, the motor136aand the motor138aare a crosswise drive motor that laterally moves the shaft by laterally moving the turning mechanism132. The shaft in which the axis is the mechanical turning axis X1is fixed to the turning support124, and the motor132aturns the shaft to turn the turning support124. A drive source that moves the mechanical turning axis X1in the lateral two-dimensional direction can be considered as a lateral drive actuator, and can be referred to as a lateral drive driver. The set of the motor136aand the motor138acan be considered as an example of a lateral drive actuator. When the lateral direction is the horizontal direction, the lateral drive actuator can be referred to as a horizontal drive actuator. The horizontal drive actuator can be restated for a horizontal driver.

The turning mechanism can be provided in the turning support. For example, the turning axis moving mechanism can directly move the mechanical turning axis X1with no use of the turning mechanism. As a more specific example, a shaft corresponding to the mechanical turning axis X1is fixed to the movable table139so as not to be turnable and so as to be movable in the direction intersecting with the mechanical turning axis X1, and the turning support124is turnably connected to the shaft. The turning mechanism132is provided in the turning support124, and the turning mechanism132generates turning force with respect to the shaft, whereby the turning support124can be turned with respect to the shaft. Even in this structure, the turning mechanism132is a mechanism that turns the turning support124about the mechanical turning axis X1between the X-ray generator126and the X-ray detector128.

When the X-ray CT imaging is performed by irradiating the head P that is the subject with the X-ray generated from the X-ray generator126, the turning axis moving mechanism134moves the mechanical turning axis X1in synchronization with the turning of the turning support124about the mechanical turning axis X1using the turning mechanism132, and the turning support124is caused to perform the combined motion, which allows the X-ray generator126and the X-ray detector128to be turned around the center of an X-ray CT imaging region R.

As illustrated inFIG. 3, the turning support124has a shape in which suspending supports124bare provided at both ends of the elongated arm body124a,namely, a U-shape that is open downward. The shaft124cprotruding upward is provided in the intermediate portion in the extending direction of the arm body124a,and the shaft124cis supported in the suspended state by the turning mechanism132.

The X-ray generator126is provided in one suspending support124b.The X-ray generator126includes an X-ray tube, and is configured to be capable of outputting the X-ray emitted from the X-ray tube toward the X-ray detector128.

An X-ray regulating unit129that adjusts a regulation amount of the X-ray generated from the X-ray generator126is provided on the side irradiated with the X-ray with respect to the X-ray detector128. The X-ray regulating unit129is a member in which an X-ray regulating hole is made. The X-ray regulating unit129permits passage of part of the X-ray generated from the X-ray generator126according to the shape and size of the X-ray regulating hole, and shields an outside of a passage range of the X-ray. The X-ray regulating unit129is also a shield that regulates the X-ray. Consequently, the range of the X-ray beam traveling to the X-ray detector128is regulated. In the X-ray regulating unit129, a plurality of types of X-ray regulating holes are made to switch the X-ray regulating holes regulating X-rays, or a member in which the X-ray regulating hole is made is moved to adjust an opening width of the X-ray regulating hole, thereby adjusting a shielded amount of the X-ray generated from the X-ray generator126, namely, the regulation amount.

The X-ray detector128is provided in one suspending support124b.The X-ray detector128includes an X-ray detector including a planar detection surface, and is configured to be able to detect the X-ray (X-ray beam), which is emitted from the X-ray generator126and transmitted through the head P. Projection data of the X-ray imaging can be obtained by the X-ray detector128.

A space in which the head P can be disposed is provided between the X-ray generator126and the X-ray detector128.

In the second embodiment, the X-ray generator126and the X-ray detector128are attached to both ends of the U-shaped turning support. Alternatively, the X-ray generator and the X-ray detector can be supported by an annular member while opposed to each other. A shaft can be provided on a support member traversing a part in a circumferential direction or an inside of the annular member such that the annular member can turnably be supported. In the second embodiment, the X-ray generator126and the X-ray detector128are supported so as to be rotatable around the vertical axis. Alternatively, the X-ray generator126and the X-ray detector128can be supported so as to be rotatable around an axis oblique to the vertical direction.

The turning support124can move up and down by the lifting unit122according to a height of the head P. The turning support124can be turned by the turning drive mechanism130such that the X-ray generator126and the X-ray detector128turn about the head P.

The head fixing apparatus arm141extending in the horizontal direction is provided in a portion of the post121below the horizontal arm123. The horizontal arm123and the head fixing apparatus arm141extend in the same direction with the side of the post121as the base end. The head fixing apparatus arm141extends toward the lower side of the horizontal arm123, and the head fixing apparatus142is provided at a leading end of the head fixing apparatus arm141. The head fixing apparatus142is located between the X-ray generator126and the X-ray detector128. The head fixing apparatus142includes a chin rest142aon which a chin of the head P that is the subject can be placed and supported and a head holder142bthat holds the head P that is the subject while sandwiching the head P from both outsides. The chin of the head P is supported on the chin rest142a,and the head P is sandwiched by the head holder142b,whereby the head P is held at a fixed position between the X-ray generator126and the X-ray detector128. The head fixing apparatus142can be constructed with at least one of the chin rest142aand the head holder142b.A cephalogram imaging head fixing apparatus suspending arm143is provided so as to extend in the horizontal direction on the side opposite to the side on which the horizontal arm123extends from the post121, and a cephalogram imaging head fixing apparatus144is supported in the suspended state by the cephalogram imaging head fixing apparatus suspending arm143. A cephalogram imaging X-ray detector128bis incorporated in the cephalogram imaging head fixing apparatus144.

A main body controller150including an operation panel apparatus158is provided in an intermediate portion in the extending direction of the head fixing apparatus arm141. InFIG. 3, the operation panel apparatus158of the main body controller150is enlarged and drawn in a balloon.

The X-ray imaging is performed in the state in which the head P that is the subject is fixed by the head fixing apparatus142, and in the state in which the turning support124is stopped or rotated according to a desired imaging mode. Consequently, the X-ray image data necessary for the generation of the image of the X-ray CT imaging, panoramic imaging, and the like can be obtained. For example, the X-ray imaging is performed while the turning support124is turned, which allows the obtainment of the X-ray CT image data necessary for the generation of the X-ray CT image. In addition, panoramic photographed images can be obtained by carrying out the X-ray imaging while the turning support124is rotated within a certain range, which allows the obtainment of a panoramic image. Additionally, the X-ray CT imaging apparatus110can also perform the X-ray imaging in order to obtain the cephalogram image and a pseudo-oral image. For example, the head P is fixed to the cephalogram imaging head fixing apparatus144supported by the cephalogram head fixing apparatus suspending arm143extending horizontally from the post121while the turning support124is stopped, and the X-ray is emitted from the X-ray generator126to perform the X-ray imaging, which allows the cephalogram image to be obtained. A function of imaging the panoramic image and a function of imaging the cephalometric image are sometimes omitted.

The main body controller150is configured to be able to receive each instruction to the imaging main body120, and is configured to be able to control each action of the imaging main body120. The main body controller150is fixed to the head fixing apparatus arm141extending in the horizontal direction from the post121. The operation panel apparatus158is provided in the main body controller150, the operation panel apparatus158displaying various kinds of information from the main body controller150while receiving various commands to the main body controller150. The operation panel apparatus158is a touch panel including a display apparatus such as a liquid crystal display panel and a touch detector disposed on a display screen of the display apparatus. A touch operation of the user on the display screen is detected with the touch detector, which allows the reception of the operation performed on the X-ray CT imaging apparatus110. The operation panel apparatus158functions as a display apparatus, namely, a display as well as an operation unit that receives the operation of the operator. A push button can be provided near the operation panel apparatus158. The display apparatus and an input apparatus (operation unit) that receives the operation of the user can separately be provided. A user interface can be used as the input apparatus that receives the operation of the operator. More specifically, a physical user interface or a speech input user interface can be used as the input apparatus.

Each unit of the imaging main body120is accommodated in an X-ray protection chamber146. A push button switch called a deadman switch that issues an instruction of the X-ray irradiation to the main body controller150is provided on an outside of a wall of the X-ray protection chamber146.

The X-ray image processing apparatus180includes an information processing main body182constructed with a computer or a work station, and is connected to the imaging main body120through a communication cable so as to be able to transmit and receive various data. However, the transmission and reception of the data can be performed by wireless communication between the imaging main body120and the X-ray image processing apparatus180. The information processing main body182can perform various pieces of image processing based on the data transmitted from the imaging main body120.

A display (display apparatus)188constructed with a display apparatus such as a liquid crystal monitor and an operation unit (input apparatus)189constructed with a keyboard or a mouse are connected to the X-ray image processing apparatus180. The operator can issue various instructions to the information processing main body182by operating a pointer through the mouse on characters or images displayed on the display188. The display188can be constructed with a touch panel.

Part or whole of the processing of the X-ray image processing apparatus180can be performed by the main body controller150. Alternatively, part or whole of the processing of the main body controller150can be performed by the X-ray image processing apparatus180.

FIG. 5is a block diagram illustrating an electric configuration of the X-ray CT imaging apparatus110.

The main body controller150of the imaging main body120controls an X-ray imaging action of the imaging main body120, and is constructed with a computer in which a Central Processing Unit (CPU)151that is at least one processor, a Random Access Memory (RAM)152, a storage153, input and output units154a,154b,an operation input unit155, and an image output unit156are interconnected to one another through a bus line157. The storage153includes a flash memory or a nonvolatile storage device such as a hard disk drive. An imaging program153a,which receives various instructions relating to the X-ray imaging while controlling the X-ray imaging action by controlling the turning drive mechanism130, the X-ray generator126, the X-ray regulating unit129, and the like according to the instructions, is stored in the storage153. When the physique of the head P that is the subject is set, a reference table153bthat is referred to in deciding the turning control content of the turning drive mechanism130according to the set physique of the head P is stored in the storage153. The reference table153bis a table in which the turning control contents of the turning drive mechanism130and the like are correlated with the sizes of a plurality of physiques of the heads P. In consideration of the size of the physique of the head P, the distance of the X-ray generator126and the X-ray detector128to the mechanical turning axis X1, and the like, the turning control content of the turning drive mechanism130is theoretically and experimentally decided such that the X-ray generator126and the X-ray detector128do not contact with the head P during the turning of the X-ray generator126and the X-ray detector128. An example of the turning control content according to the size of the physique of the head P will be described later. The RAM152serves as a work area when the CPU151performs predetermined processing. The input and output unit154ais connected to a motor of the turning mechanism132that turns the turning support124of the imaging main body120, a motor of the turning axis moving mechanism134that moves the turning support124, the X-ray generator126, the X-ray detectors128,128b,and the X-ray regulating unit129, and the input and output unit154bis communicably connected to the X-ray image processing apparatus180. The operation input unit155is connected to the touch detector158bof the operation panel apparatus158, and the image output unit156is connected to the display158aof the operation panel apparatus158.

In the main body controller150, the CPU151performs arithmetic processing according to a procedure described in the imaging program153aand the instruction received through the touch detector158b,thereby functioning as a physique setting unit (subject physique setting unit)151athat can set the size of the physique of the head P and a turning controller151bthat controls the turning mechanism132and the turning axis moving mechanism134in performing the X-ray imaging such as the X-ray CT imaging. The physique setting unit151acan be called a head size setting unit. The CPU151controls the turning mechanism132and the turning axis moving mechanism134to turn the X-ray generator126and the X-ray detector128around the head P, and can obtain detection results of the X-rays detected by the X-ray detectors128,128bthrough the head P. The CPU151also functions as an imaging region setting unit151cthat sets the imaging region. For example, the setting of the spatial position of the imaging region or the setting of expansion of the imaging region can be performed as the setting of the imaging region.

The imaging program153aand the reference table153bare previously stored in the storage153. Alternatively, the imaging program153aand the reference table153bcan be provided to the existing X-ray CT imaging apparatus or the information processing main body that controls the X-ray CT imaging apparatus in the form of being recorded on a recording medium such as a CD-ROM, a DVD-ROM, or an external flash memory, or by download from an external server through a network. Because the CPU151and the RAM152include circuits, and many of the other elements also include circuits or configurations connected by circuits, the body controller150is an element that is mechanically constructed with circuits. The turning controller151bis a circuit that mechanically processes the turning control according to the program. Similarly, the physique setting unit151ais a circuit that performs processing of setting the physique of the subject from physique data of the subject according to the program, and the imaging region setting unit151cis a circuit that performs processing of setting the imaging region.

The X-ray image processing apparatus180generates X-ray image data185bbased on the imaging data from the imaging main body120. The information processing main body182is constructed with a computer in which a CPU183that is at least one processor, a RAM184, a storage185, an input and output unit186, an operation input unit189a,and an image output unit188aare mutually connected through a bus line182a.The storage185is constructed with a flash memory or a nonvolatile storage device such as a hard disk drive, and an image processing program185awith which the information processing main body182generates the X-ray image data185bbased on the imaging data from the imaging main body120and X-ray image data185bare stored in the storage185. Management data in which the X-ray image data185bis correlated with specific information about the head P (specific information about a patient) can be stored in the storage185. The X-ray image processing apparatus180receives data relating to an imaging condition from the main body controller150, and can store the data relating to an imaging condition in the storage185while correlating the data relating to an imaging condition with the generated X-ray image data185b.The RAM184serves as a work area when the CPU183performs predetermined processing. The input and output unit186is connected to the imaging main body120, and the X-ray imaging data obtained by the imaging main body120is input to the input and output unit186through the input and output unit186. The operation input unit189ais connected to the operation unit189, and the image output unit188bis connected to the display188.

In the information processing main body182, the CPU183performs the arithmetic processing according to the image processing program185a,thereby performing the processing as the image processor that generates the desired X-ray image data based on the X-ray imaging data obtained by the imaging main body120. That is, data such as the CT image, the panoramic image, and the cephalogram image is generated in response to an instruction received through the main body controller150. The storage185stores the generated X-ray image data185b.

A part or whole of the function implemented in each of the above units can be implemented in a hardware manner using a dedicated logic circuit or the like. A part or whole of the function implemented in each of the above units can be processed by a single processor in an integrated manner, or appropriately processed by a plurality of processors in a distributed manner.

<Setting of physique and turning processing during imaging>

With reference to a flowchart inFIG. 6, the imaging program153awill be described centered on the setting of the physique and the turning processing during the imaging.

When the performance of the CT imaging is set, an operation to input the physique is received in step S11.

An example of the reception of the operation to input the physique will be described.FIG. 7is a view illustrating a display example in the operation panel apparatus158. A panorama selection image191a(see characters “Pan”), a cephalogram selection image191b(see characters “Ceph”), and a CT selection image191c(see characters “CT”) are displayed on the display158aof the operation panel apparatus158as the image used to select the imaging mode. A physique setting image193and an imaging region setting image194are displayed on the display158aas the image used to set the imaging condition. In this case, the physique setting image193and the imaging region setting image194are displayed on the right side of the display158a.An illustration image195is displayed on the display158a.The illustration image195is displayed on the lower sides of the panorama selection image191a,the cephalogram selection image191b,and the CT selection image191cin the display158a.The illustration image195is an image representing the imaging region, and a dental arch is displayed as the illustration image.

The touch detector158bis provided on the display158aas a two-dimensional position detector that detects the touch position with respect to the display region.

When the operator touches any one of the panorama selection image191a,the cephalogram selection image191b,and the CT selection image191c,the touch operation is detected by the touch detector158b.Consequently, the main body controller150receives whether to perform the panoramic imaging, the cephalogram imaging, or the X-ray CT imaging.

As illustrated inFIG. 8, when the operator touches one of the physique setting image193and the imaging region setting image194, a selection image corresponding to the physique setting image193or the imaging region setting image194is displayed according to the touch operation. In the example ofFIG. 8, for convenience, the selection images corresponding to all the physique setting image193and the imaging region setting image194are displayed. However, actually the selection image corresponding to the touched one of the physique setting image193and the imaging region setting image194is displayed.

When the operator touches the physique setting image193, a normal-size selection image193a(M size) and a large-size selection image193b(L size) are displayed as a plurality of physique selection images. The operation to input the physique of the head P is received when the user selectively touches the normal-size selection image193aor the large-size selection image193b.

A plurality of imaging region selection images194a,194b,194c,194d,and194eare displayed when the operator touches the imaging region setting image194.

The plurality of imaging region selection images194a,194b,194c,194d,194eindicate regions in which sizes (a diameter and a height) are different from one another. The operation to set the imaging region is received when the user selectively touches any one of the plurality of imaging region selection images194a,194b,194c,194d,194e.

With reference toFIG. 7, the imaging region195a(or the imaging region195b) is displayed while superimposed on the illustration image195. A circle having a size corresponding to the imaging region set through the imaging region setting image194is displayed as the imaging regions195a,195b.The imaging region195ais an image that is displayed when the imaging region where the whole of the dental arch is set to the target is selected, and the imaging region195bis an image that is displayed when the imaging region where a part of the dental arch is set to the target is selected. In particular, when the imaging region195bis selected, the operator touches any position of the illustration image195to move the imaging region195bto a position where a part of the dental arch is designated. Consequently, the imaging region can be designated at any position of the dental arch (for example, a front tooth region, a right molar region, a left molar region). In the drawing, in order to clearly illustrate a difference, the difference between the imaging regions195a,195bis illustrated with some emphasis. At this point, the description will be made on the assumption that the X-ray CT imaging is performed with the whole dental arch that is the jaw region of the head P as the X-ray CT imaging region R.

In the above example, the designation of the imaging mode, the setting of the physique, the designation of the imaging region, and the like are performed using the touch panel. Alternatively, various settings can be received through a switch (push button) that physically receives the operation.

With reference toFIG. 6, in step S12, when the physique setting unit151areceives the operation to input the physique of the head P through the operation panel apparatus158, the setting of the physique of the head P is performed according to the received content. The physique setting unit151areceives the input operation to select one of the normal-size selection image193aand the large-size selection image193b,which are physique sizes of a plurality of selection candidates, through the operation panel apparatus158, thereby setting the physique of the head P.

In step S13, the turning control content and the regulation amount are determined according to the set physique. The turning control content indicates how to turn the X-ray generator126and the X-ray detector128around the head P with what kind of trajectory. The turning control content is expressed by the trajectory of at least one of the X-ray generator126and the X-ray detector128, the fixed position or movement trajectory of the mechanical turning axis X1during the turning, or the position coordinates or movement coordinates of the X-direction drive unit136and the Y-direction drive unit138with respect to a turning speed of the turning mechanism132.

When the turning control content is decided, the separation distance D is decided on the assumption that the separation distance is the distance that is smaller one of the distance between the center A of the imaging region R and the X-ray generator126and the distance between the center A of the imaging region R and the X-ray detector128in turning the X-ray generator126and the X-ray detector128around the center A of the imaging region R. In this case, because the turning axis X1is located closer to the X-ray detector128in the turning support124, the separation distance D is the distance between the center A of the imaging region R and the X-ray detector128. The position of the imaging region R in the X-ray CT imaging apparatus110is known because the head P is held at a fixed position by the head fixing apparatus142and the imaging region is set as described above.

Because the distance of the X-ray generator126to the center A of the imaging region R is also decided, magnification is also decided when the X-ray emitted from the X-ray generator126is incident on the X-ray detector128through the head P. Assuming that DA is the distance between the X-ray generator126and the X-ray detector128, and that D1is the distance between the X-ray generator126and the center A of the imaging region R, magnification m becomes m=DA/D1.

Because a minimum width of the X-ray is decided in order to transmit the X-ray generated from the X-ray generator126through the whole imaging region R when the turning control content is decided, an X-ray regulating width (X-ray regulating hole) that should be regulated by the X-ray detector128can also be set in a range larger than the minimum width and in a range that prevents surroundings of the range larger than the minimum width from being excessively irradiated with the X-ray.

For example, the decision of the turning control content and the regulation amount according to the set size of physique can be performed by referring to the reference table inFIG. 9. That is, the reference table in which the turning control content, the separation distance D (magnification m), and the regulating width W are correlated with the physique of the head P is previously registered. In the example ofFIG. 9, for the normal physical shape P(M), the mechanical turning axis X1is turned while matched with the center A of the imaging region R, the separation distance D(M) (magnification m(M)), and the regulating width W(M) are correlated with one another as the turning control content. For the physique P(L) larger than the normal physique P(M), the mechanical turning axis X1is turned with a radius r about the center A of the imaging region R, the separation distance D(L) (magnification factor m(L)), and a regulating width W(L) are correlated with one another as the turning control content. The separation distance D(M), the magnification m(M), the regulating width W(M), the separation distance D(L), the magnification m(L), the regulating width W(L), and the radius r are defined by a specific numerical value, and the physique P(L) is larger than the physique P(M), separation distance D(M)<separation distance D(L), magnification m(M)<magnification m(L), and regulating width W(M)<regulating width W(L) hold.

In step S14, the X-ray regulating unit129is controlled according to the regulating widths W(M), W(L) that are the decided regulation amount such that the X-ray having the width corresponding to the imaging region R is emitted from the X-ray generator126.

In step S15, the CT imaging is performed by performing the turning control based on the decided turning control content. That is, when the X-ray CT imaging is performed by irradiating the head P with the X-ray generated from the X-ray generator126, the position control of the turning axis X1is performed according to the size of the physique of the head P that is the subject set by the physique setting unit151a.

An example in which the drive control causing the turning mechanism32to perform the above combined motion and the drive control turning the turning support124in the state in which the mechanical turning axis X1is fixed to the position of the center A of the imaging region R are switched according to the size of the physique of the head P which is the subject set by the physique setting unit151awill be described below.

In this case, when the X-ray generator126and the X-ray detector128are turned around the center A of the imaging region R, the position of the mechanical turning axis X1with respect to the center A of the imaging region R can be controlled according to the physique P(M) or the physique P(L) of the head P set by the physique setting unit151asuch that the separation distance D (L) when the set physique is the first physique P(L) is larger than the separation distance D(M) when the set physique is the second physique P(M) small than the first physique P(L).

An example in which, according to the physique of the head P set by the physique setting unit151a,the drive control causing the turning support124to perform the combined motion is performed when the set physique of the head P is the first physique P(L), and the drive control turning the turning support124in the state in which the mechanical turning axis X1is fixed to the center position of imaging region R when the set physique of the head P is the second physique P(M) smaller than the first physique P(L) will be described below.

Switching of the drive control with respect to the size of the physique can be reversed depending on the position of the turning axis X1with respect to the X-ray generator126and the X-ray detector128. For example, when the turning axis X1is located at a position close to a middle between the X-ray generator126and the X-ray detector128, the drive control turning the turning support124can be performed on the first physique P(L) having the set relatively large physique of the head P while the mechanical turning axis X1is fixed to the center position of the imaging region R, and the physique of the set head P is relatively small the drive control causing the turning support124to perform the combined motion can be performed on the second physique P(M) having the set relatively small physique of the head P.

An example of the turning action will be described in more detail with reference toFIGS. 10 and 11.FIG. 10is an explanatory view illustrating turning action when the physique is the relatively small second physique P(M), andFIG. 11is an explanatory view illustrating turning action when the physique is the relatively large first physique P(L).FIGS. 10 and 11are principle explanatory views when the turning action is viewed from the Z-axis direction. AlthoughFIGS. 10 and 11illustrate the state in which the turning support124is turned 180 degrees, the CT imaging can be performed by turning the turning support124by 360 degrees according to the setting.

In the example ofFIGS. 10 and 11, the position of the mechanical turning axis X1is located closer to the X-ray detector128than the intermediate point between the X-ray generator126and the X-ray detector128on the turning support124.

For the relatively small second physique P(M), as illustrated inFIG. 10, the turning support124is turned while the mechanical turning axis X1is matched with the center A of the imaging region R. In this case, the X-ray generator126and the X-ray detector128turn about the mechanical turning axis X1matched with the center A of the imaging region R. The X-ray regulating unit129forms the X-ray into an X-ray cone beam CB. The turning support124is driven by the turning drive mechanism130, the X-ray detector128is located close to the +Y-direction inFIGS. 10 and 11, and both ends of the spread in the x-direction of the X-ray cone beam CB contact with both ends of the spread in the x-direction of the imaging region R when viewed from a focal point of an X-ray tube of the X-ray generator126at the position where the X-ray generator126is located close to the −Y-direction, a center beam CTB that equally divided a spread angle in the x-direction of the X-ray cone beam CB has a positional relationship in which the center beam CTB passes through the center A of the imaging region R, and the positional relationship is maintained during the imaging and the turning of the turning support124. During the turning, the distance between the center A of the imaging region R and the X-ray generator126is maintained at D1, and the distance between the center A of the imaging region R and the X-ray detector128is maintained at D2. Because the X-ray detector128is located closer to the center of the imaging region R than the X-ray generator126on the orbits of the X-ray generator126and the X-ray detector128, which are set for the imaging region R, during the X-ray imaging, the separation distance D(M) becomes the distance D2between the center A of the imaging region R and the X-ray detector128. The separation distance D(M) is set larger than the maximum distance between the center A of the imaging region R and a surface of the head P(P2) having the smaller physique P(M) in the direction orthogonal to the turning axis X1. For this reason, the X-ray detector128can turn around the head P(P2) without contacting with the head P(P2) having the smaller physique P(M). The X-ray generator126turns at a position farther from the center A of the imaging region R than the X-ray detector128, so that the X-ray generator126can turn around the head P(P2) without contacting with the head P(P2). The separation distance D (not illustrated) becomes the distance between the center A of the imaging region R and the X-ray generator126when the X-ray generator126is closer to the imaging center A than the X-ray detector128on the orbits of the X-ray generator126and the X-ray detector128, which set for the imaging region R, during the X-ray imaging.

Because the chin rest142ais commonly used for the head P1and the head P2, the imaging region R becomes the same position in the front of the head in the head P1and the head P2, and an occipital region of the head P1occupies a larger region than an occipital region of the head P2on the −Y-side. For the relatively large first physique P(L) (head P1), when the X-ray detector128turns in the same manner as described above, there is a possibility that the X-ray detector128abuts on the head P(P1) having the first physique P(L).

For this reason, for the relatively large first physique P(L), as illustrated inFIG. 11, the turning support124is turned about the mechanical turning axis X1while the mechanical turning axis X1is turned with the radius r about the center A of the imaging region R. That is, the mechanical turning axis X1moves on a circular orbit CLa having the radius r. That is, the position of the mechanical turning axis X1with respect to the center A of the imaging region R is controlled such that the mechanical turning axis X1is moved away from the center A of the imaging region R. More specifically, the mechanical turning axis X1is turned with the radius r about the center A of the imaging region R by the turning axis moving mechanism134in synchronization with the turning of the turning support124about the mechanical turning axis X1using the turning mechanism132. In order to move the X-ray detector128away from the center A of the imaging region R, the mechanical turning axis X1is moved away from the center A of the imaging region R toward the side of the X-ray detector128. That is, the mechanical turning axis X1turns around the center A of the imaging region R while maintaining the positional relationship provided between the center A of the imaging region R and the X-ray detector128.

The mechanical turning axis X1is located at a position LC1shifted onto the +Y-side from the center A of the imaging region R in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, the mechanical turning axis X1is located at a position LC2shifted onto the +X-side from the center A of the imaging region R in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side, and the mechanical turning axis X1is located at a position LC3shifted onto the −Y-side from the center A of the imaging region R in timing when the X-ray generator126is located on the +Y-side while the X-ray detector128is located on the −Y-side.

Although not illustrated, assuming that the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is shifted onto the −X-side from the center A of the imaging region R.

The synchronization between the turning of the turning support124about the mechanical turning axis X1and the turning of the mechanical turning axis X1about the center A of the imaging region R will further be described with reference toFIG. 11. The mechanical turning axis X1is located at the position LC1deviating from the center A, and the whole imaging region R is irradiated from the −Y-direction toward the +Y-direction with the X-ray cone beam CB in the illustrated example. It is assumed that an orientation COR1is an orientation in which the center beam CTB travels toward the imaging region R, namely, the orientation toward the center A in the illustrated example, and that an orientation XOR1is an orientation from the mechanical turning axis X1toward the center A. In the illustrated example, the whole imaging region R is irradiated from the −X-direction to the +X-direction with the X-ray cone beam CB at a point of time the mechanical turning axis X1turns about the center A to the position LC2deviating from the center A along the circular orbit CLa having the radius r while the turning support124turns about the mechanical turning axis X1. It is assumed that an orientation COR2is the orientation in which the center beam CTB travels toward the imaging region R, namely, the orientation toward the center A in the illustrated example, and that an orientation XOR2is the orientation from the mechanical turning axis X1toward the center A. It is assumed that AGC1is a displacement angle amount from the orientation COR1to the orientation COR2, and that AGX1is a displacement angle amount from the orientation XOR1to the orientation XOR2. The displacement from the orientation COR1to the orientation COR2and the displacement from the orientation XOR1to the orientation XOR2are identical to each other as a turning direction in which the center A is set to the turning center, and the displacement angle amount AGC1and the displacement angle amount AGX1are equal to each other. The turning movement of the turning support124is performed by the turning drive mechanism130. In the illustrated example, the turning of the turning support124is performed by the turning mechanism132, and the movement of the mechanical turning axis X1is performed by the turning axis moving mechanism134. The above synchronization is performed while this relationship is kept.

At this point, the coordinate of the mechanical turning axis X1is temporarily considered while leavingFIG. 11. For example, assuming that (X(a),Y(a)) is the coordinates of X and Y in the XYZ-coordinate system of the center A of the imaging region R, and that θ (an angle rotating counterclockwise from the direction in which the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side) is the turning angle of the turning support124by the turning mechanism132, the turning mechanism132and the turning axis moving mechanism134are controlled such that an X-coordinate of the mechanical turning axis X1becomes “X(a)-rcosθ” by the X-direction drive unit136, and such that a Y-coordinate of the mechanical turning axis X1becomes “Y(a)-rsinθ” by the Y-direction drive unit138. The control content can similarly be applied to the following modifications in which the mechanical turning axis X1is turned.

In this case, the X-ray generator126and the X-ray detector128turn about the mechanical turning axis X1. With reference toFIG. 11, based on the distance D1between the center A of the imaging region R and the X-ray generator126in the case ofFIG. 10(in the case ofFIG. 10, the distance D1is the same as the distance between the mechanical turning axis X1and the X-ray generator126), the distance between the center A of the imaging region R and the X-ray generator126during the turning is distance D1−radius r, and is kept constant. Based on the distance D2in the case ofFIG. 10(in the case ofFIG. 10, the distance D2is the same as the distance between the mechanical turning axis X1and the X-ray detector128), the distance between the center A of the imaging region R and the X-ray detector128during the turning is distance D2+radius r, and is kept constant. The smaller one becomes the separation distance D(L). At this point, it is assumed that the radius r is decided within the range of (distance D1−radius r)≥(distance D2+radius r). For this reason, the separation distance D(L) is distance D2+radius r. The separation distance D(L) is set larger than the maximum distance between the center A of the imaging region R and the surface of the head P(P1) having the larger physique P(L) in the direction orthogonal to the turning axis X1. Consequently, the X-ray detector128can turn around the head P(P1) having the larger physique P(L) without contacting with the head P(P1). The X-ray generator126turns at a position as far as or far away from the X-ray detector128with respect to the center A of the imaging region R, so that the X-ray generator126can turn around the head P(P1) without contacting with the head P(P1). The maximum distance to the surface of the head P(P1) can be set to the maximum distance in the range where the X-ray generator126or the X-ray detector128relating to the smaller separation distance D(L) turns. For example, for the turning angle of the turning support124less than 360° such as the turning angle of 180°, the maximum distance in the range of the movement orbit of the X-ray generator126or the X-ray detector128relating to the smaller separation distance D(L) can be targeted except for the occipital region when the X-ray generator126or the X-ray detector128relating to the smaller separation distance D(L) does not turn to the occipital region.

In the embodiment ofFIG. 11, during the X-ray CT imaging, a bias of the mechanical turning axis X1with respect to the center A is generated on the side of the X-ray detector128. The direction from the center A toward the mechanical turning axis X1and the direction from the X-ray generator126toward the X-ray detector128are maintained in parallel.

Hereinafter, the turning center of the X-ray generator126and the X-ray detector128is referred to as an imaging turning center IC.

When the mechanical turning axis X1is subjected to the control inFIG. 11, the X-ray generator126and the X-ray detector128turn with the center A of the imaging region R as the imaging turning center IC. As described above, the imaging turning center IC can be generated when the mechanical turning axis X1is subjected to two-dimensional movement control.

When the relatively small second physique P(M) inFIG. 10is compared to the relatively large first physique P(L) inFIG. 11, the relatively small second physique P(M) is smaller than the relatively large first physique P(L) in the distance between the center A of the imaging region R and the X-ray generator126. For this reason, in order to transmit the X-rays emitted from the X-ray generator126through the whole imaging region R, the regulating width W(M) of the X-ray by the X-ray regulating unit129for the second physique P (M) can be set smaller (the passage allowable width is widened) than the regulating width W(L) of the X-ray by the X-ray regulating unit129for the first physique P(L). Consequently, the X-ray can be emitted in the range corresponding to the imaging region R. That is, the regulating widths W(L), W(M) are set according to the distance between the center A of the imaging region R and the X-ray generator126when the X-ray generator126and the X-ray detector128are turned around the center A of the imaging region R, and the X-ray regulating unit129adjusts the regulation amount of the X-ray generated from the X-ray generator126according to the distance between the center A of the imaging region R and the X-ray generator126. The regulation amount of the main X-ray can similarly be adjusted in each modification.

In the regulating width W of the X-ray by the X-ray regulating unit129, only a regulating width Wx in the x-direction can be adjusted, and a regulating width Wz in the z-direction (vertical direction) can also be adjusted.

By turning the X-ray generator126and the X-ray detector128around the imaging region R of the head P, the X-ray image data necessary for the generation of the X-ray CT image of the imaging region R is obtained, and the X-ray CT image is generated based on the obtained data.

In the X-ray CT imaging apparatus110configured as described above, the position control of the turning axis X1is performed according to the size of the physique of the head P that is the subject set by the physique setting unit151a,so that the X-ray generator126and the X-ray detector128turning around the head P can be prevented from contacting with the head P.

In this case, when the X-ray generator126and the X-ray detector128are turned around the center A of the imaging region R, assuming that the separation distance is the smaller one of the distance between the center A of the imaging region R and the X-ray generator126and the distance between the center A of X and the X-ray detector128, the position control of the mechanical turning axis X1with respect to the center A of the imaging region R is performed according to the physiques P(L), P(M) of the head P set by the physique setting unit151asuch that the separation distance for the large physique P (L) of the head P is larger than the separation distance for the small physique P (M) of the head P, so that the X-ray generator126and the X-ray detector128turning around the head P can be prevented from contacting with the head P.

The turning trajectory of the X-ray detector128is changed according to the size of the physiques P(L), P (M) of the head P, so that the X-ray CT imaging can be performed by bringing the X-ray detector128as close as possible to the head P while the contact between the X-ray detector128and the head P is suppressed. Consequently, the clear X-ray image can be generated.

The turning axis moving mechanism134is provided on not the side of the turning support124, but the side of the horizontal arm123with respect to the turning mechanism132. Consequently, a weight of the turning support124can be reduced, and a load turning the turning support124can be reduced as much as possible.

When the X-ray CT imaging is performed by irradiating the head P with the X-ray generated from the X-ray generator126, for the head P1of a relatively large first physique P (L), the turning axis moving mechanism134rotates the mechanical turning axis X1about the center A of the imaging region R in synchronization with the turning of the turning support124about the mechanical turning axis X1using the mechanism132, whereby the separation distance can be adjusted while the X-ray generator126and the X-ray detector128are turned along the orbit as close as possible to the circle. The magnification ratio can be kept constant as much as possible by turning the X-ray generator126and the X-ray detector128along the orbit as close as possible to the circle.

For the head P2of the relatively small second physique P(M), the X-ray generator126and the X-ray detector128are turned around the turning axis X1while the turning center of the mechanical turning axis X1is fixed to the position of the center A of the imaging region R, so that accuracy of the turning of the imaging system constructed with the X-ray generator126and the X-ray detector128can be enhanced to obtain the clearer X-ray CT image.

In the example ofFIGS. 10 and 11, the mechanical turning axis X1is located closer to the X-ray detector128than the intermediate point between the X-ray generator126and the X-ray detector128on the turning support124. For this reason, for the head P2of the relatively small second physique P(M), the magnification ratio of the image can be reduced when the X-ray generator126and the X-ray detector128are turned around the turning axis X1while the turning center of the mechanical turning axis X1is fixed to the position of the center A of the imaging region R. Typically, a focal point of an X-ray tube of the X-ray generator126is not a perfect point light source, but has a small constant area, so that a degree of contour blurring can be decreased by reducing the magnification ratio.

When the X-ray generator126and the X-ray detector128are turned as described above, the X-ray regulating unit129adjusts the regulation amount of the X-ray generated from the X-ray generator126according to the distance of the X-ray generator126to the center A of the imaging region R, which allows the X-ray having a proper width to be incident on the imaging region R of the head P according to the separation distance.

The mechanical turning axis X1is along the vertical direction, so that the X-ray generator126and the X-ray detector128can be turned around the axis along the vertical direction. Consequently, the X-ray CT imaging is suitably performed with the head P of a standing or sitting human body as the subject.

The X-ray CT imaging is performed with the jaw region of the head P that is the subject as the imaging region R, so that the X-ray generator126and X-ray detector128can be prevented from contacting with the head P according to the physique of the head P when the CT imaging is performed on the jaw region.

The distance of the X-ray generator126to the center A of the imaging region R and the distance of the X-ray detector128to the center A of the imaging region R are kept constant while the CT imaging is performed, so that the X-ray CT imaging can be performed while the magnification ratio is kept constant.

For the head P having the relatively small second physique P(M), the mechanical turning axis X1is matched with the center A of the imaging region R, so that the CT imaging can be performed while a driving load on the apparatus is reduced. On the other hand, for the head P having the relatively large first physique P(L), the position of the mechanical turning axis X1with respect to the center A of the imaging region R is controlled such that the position of the mechanical turning axis X1is moved away from the center A of the imaging region R, so that the separation distance can be increased to prevent the contact of the X-ray generator126and the X-ray detector128with the head P.

In the X-ray CT imaging apparatus110, the operator or the like of the X-ray CT imaging apparatus110performs the input operation through the operation panel apparatus158, which allows the setting of the physique of the head P.

In particular, the operator or the like can easily perform the input operation by selecting one of the normal-size selection image193aand the large-size selection image193bthat are the physiques of the plurality of selection candidates through the operation panel apparatus158.

However, the size of the physique can be input when the operator or the like inputs the size of the physique using a ten key or the like.

MODIFICATIONS

Various modifications will be described below based on the first embodiment or the second embodiment.

First Modification

In the second embodiment, by way of example, the drive control that causes the turning support124to perform the combined motion and the drive control that causes the turning support124to turn while fixing the mechanical turning axis X1to the position of the center A of the imaging region R are switched according to the size of the physique of the head P that is the subject set by the physique setting unit151a.

An example, in which the distance of the mechanical turning axis X1with respect to the center A of the imaging region R according to the size of the physique of the head P that is the subject set by the physique setting unit151awhen the turning support124performs the combined motion, will be described in a first modification ofFIGS. 12 and 13. That is, an example, in which the position control of the mechanical turning axis X1with respect to the center A of the imaging region R is performed such that the position of the mechanical turning axis X1is moved away from the center A of the imaging region R in both the relatively small second physique P(M) and the relatively large first physique P(L), will be described in the first modification.

FIG. 12is an explanatory view illustrating the turning action for the relatively small second physique P(M), andFIG. 13is an explanatory view illustrating the turning action for the relatively large first physique P(L). In the first modification, the mechanical turning axis X1is located at the central position between the X-ray generator126and the X-ray detector128. For this reason, the distance of the X-ray generator126to the mechanical turning axis X1and the distance of the X-ray detector128to the turning axis X1are equal to each other. AlthoughFIGS. 12 and 13illustrate the state in which the turning support124is turned by 180 degrees, the CT imaging can be performed by turning the turning support124by360degrees according to the setting.

For the relatively small second physique P (M), as illustrated inFIG. 12, the turning support124is turned about the mechanical turning axis X1while the mechanical turning axis X1is turned with a radius r(M) about the center A of the imaging region R. More specifically, the mechanical turning axis X1is turned with the radius r(M) about the center A of the imaging region R by the turning axis moving mechanism134in synchronization with the turning of the turning support124about the mechanical turning axis X1using the turning mechanism132. That is, the mechanical turning axis X1moves on a circular orbit CLb having the radius r(M). In order to bring the X-ray detector128close to the center A of the imaging region R, the mechanical turning axis X1is moved away from the center A of the imaging region R toward the side of the X-ray generator126. That is, the mechanical turning axis X1turns around the center A of the imaging region R while maintaining the positional relationship provided between the center A of the imaging region R and the X-ray generator126.

The mechanical turning axis X1is located at a position LC11shifted onto the −Y-side from the center A of the imaging region R in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, the mechanical turning axis X1is located at a position LC12shifted onto the −X-side from the center A of the imaging region R in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side, and the mechanical turning axis X1is located at a position LC13shifted onto the +Y-side from the center A of the imaging region R in timing when the X-ray generator126is located on the +Y-side while the X-ray detector128is located on the −Y-side.

Although not illustrated, assuming that the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is shifted onto the +X-side from the center A of the imaging region R.

When the CT imaging is performed by turning the X-ray generator126and the X-ray detector128while the mechanical turning axis X1is matched with the center A of the imaging region R, a degree to which the X-ray detector128is moved away from the imaging region R is excessively large, so that the orbit inFIG. 12is preferably used in the case that the X-ray detector128is brought as close as possible to the imaging region R while the contact with the head P2is avoided.

In this case, assuming that DP is the distance of the X-ray generator126to the mechanical turning axis X1and the distance of the X-ray detector128to the turning axis X1, the distance between the center A of the imaging region R and the X-ray generator126during the turning is distance DP+radius r(M), and is kept constant. The distance between the center A of the imaging region R and the X-ray detector128during the turning is distance DP−radius r(M), and is kept constant. Distance DP−radius r(M), which is the smaller one, becomes the separation distance D(M). This separation distance D(M) is set larger than the maximum distance between the center A of the imaging region R and the surface of the head P(P2) having the smaller physique P(M) in the direction orthogonal to the turning axis X1. For this reason, the X-ray detector128can turn around the head P(P2) without contacting with the head P(P2) having the smaller physique P(M). The X-ray generator126turns at a position farther from the X-ray detector128with respect to the center A of the imaging region R, so that the X-ray generator126can turn around the head P(P2) without contacting with the head P that is the subject.

For the relatively large first physique P(L), when the X-ray detector128turns in the same manner as described above, there is a possibility that the X-ray detector128abuts on the head P(P1) having the first physique P(L).

For this reason, in the example ofFIG. 13, the turning support124is turned about the mechanical turning axis X1while the mechanical turning axis X1is turned with a radius r(L) about the center A of the imaging region R. More specifically, the mechanical turning axis X1is turned with the radius r(L) about the center A of the imaging region R by the turning axis moving mechanism134in synchronization with the turning of the turning support124about the mechanical turning axis X1using the turning mechanism132. At this point, radius r(L)<radius r(M) holds. That is, the mechanical turning axis X1moves on a circular orbit CLc having the radius r(L).

That is, also in the first physique P(L), the X-ray detector128is desired to be brought as close as possible to the imaging region R. As in the case ofFIG. 12, in order to bring the X-ray detector128close to the center A of the imaging region R as compared with the case that the turning axis X1is matched with the center A of the imaging region R, the mechanical turning axis X1is moved away from the center A of the imaging region R toward the side of X-ray generator126. In this case, the mechanical turning axis X1turns around the center A of the imaging region R while maintaining the positional relationship provided between the center A of the imaging region R and the X-ray generator126. However, as compared with the case ofFIG. 12, the X-ray detector128is desired to be moved away from the center A of the imaging region R because of the large physique. For this reason, the turning axis X1is turned with the radius r(L) smaller than the radius r(M).

The X-ray generator126and the X-ray detector128turn around the imaging turning center IC while the imaging turning center IC is placed on the position of the center A.

The mechanical turning axis X1is located at a position LC21shifted onto the −Y-side from the center A of the imaging region R in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, the mechanical turning axis X1is located at a position LC22shifted onto the −X-side from the center A of the imaging region R in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side, and the mechanical turning axis X1is located at a position LC23shifted onto the +Y-side from the center A of the imaging region R in timing when the X-ray generator126is located on the +Y-side while the X-ray detector128is located on the −Y-side.

Although not illustrated, assuming that the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is shifted onto the +X-side from the center A of the imaging region R.

When the X-ray detector128is brought as close as possible to the imaging region R to perform the imaging while the contact with the head P1is avoided, the orbit inFIG. 13is preferably used.

In this case, the distance between the center A of the imaging region R and the X-ray generator126during the turning is distance DP+radius r(L), and is kept constant. The distance between the center A of the imaging region R and the X-ray detector128during the turning is distance DP−radius r(L), and is kept constant. Distance DP−radius r(L), which is the smaller one, becomes the separation distance D(L). Because of radius r(L)<radius r(M), the separation distance D(L) is larger than the separation distance D(M). The separation distance D(L) is set larger than the maximum distance between the center A of the imaging region R and the surface of the head P(P1) having the larger physique P(L) in the direction orthogonal to the turning axis X1. Consequently, the X-ray detector128can turn around the head P(P1) that is the subject having the larger physique P(L) without contacting with the head P(P1). The X-ray generator126turns at a position farther from the X-ray detector128with respect to the center A of the imaging region R, so that the X-ray generator126can turn around the head P(P1) without contacting with the head P(P1) that is the subject.

As described above, the mechanical turning axis X1can be moved away from the center A of the imaging region R for any one of the relatively large physique P(L) and the relatively small physique P(M). In this case, the orbit on which the X-ray generator126and the X-ray detector128turn can be changed according to the size of the physique by changing the distance of the mechanical turning axis X1to the center A of the imaging region R according to the size of the physique, and therefore the X-ray generator126and the X-ray detector128can be prevented from contacting with the head P.

When the turning axis X1is located at a position biased to the X-ray generator126or the X-ray detector128(in particular, a largely biased position), the turning axis X1is turned while located between the center A of the imaging region R and the X-ray generator126or the X-ray detector128on the side on which the turning axis X1is biased, the turning radius of the X-ray generator126or the X-ray detector128on the side on which the turning axis X1is biased with respect to the center A of the imaging region R can be increased by the turning radius of the turning axis X1. In this case, radius r(L)>radius r(M) can hold for the turning radius r(L) (the turning radius when the physique is large) of the X-ray generator126or X-ray detector128on the side on which the turning axis X1is biased and the radius r(M) (the turning radius when the physique is small).

As described in the second embodiment, the turning support124can be turned about the mechanical turning axis X1while the mechanical turning axis X1is turned with the radius r about the center A of the imaging region R for the relatively small second physique P(M), and the turning support124can be turned while the mechanical turning axis X1is matched with the center A of the imaging region R for the relatively large first physique P(L).

For example, when the mechanical turning axis X1is located at or near the central position between the X-ray generator126and the X-ray detector128as in the first modification, for the relatively large first physique P(L), the turning support124can be turned while the mechanical turning axis X1is fixed to the position of the center A of the imaging region R. In this case, although the degree of separation from the imaging region R of the X-ray detector128is larger than that inFIG. 13, the control can be performed when the magnification ratio falls within an allowable range. For the relatively small second physique P(M), the turning axis X1is shifted to the X-ray generator side in order to bring the X-ray detector128closer to the imaging region R, and the turning axis X1can be turned as described above while the state in which the turning axis X1is disposed between the center A of the imaging region R and the X-ray generator126is maintained.

Second Modification

In a second modification, an example in which offset scan is performed will be described with reference toFIGS. 14 and 15. In the offset scan, a part of the imaging region R is irradiated with the X-ray while a horizontally symmetrical axes X2of the spread of the X-ray generated from the X-ray generator126passes through a position deviating from the center A of the imaging region R in the imaging region R, and the X-ray generator126and the X-ray detector128turn around the imaging region R to perform the CT imaging. The X-ray irradiation range is set so as to be greater than or equal to a half of the imaging region R, and so as to be less than the whole imaging region R.

In the example ofFIGS. 14 and 15, the position of the mechanical turning axis X1is located closer to the X-ray detector128than the intermediate point between the X-ray generator126and the X-ray detector128on the turning support124.

The X-ray emitted from the X-ray generator126is formed into the X-ray cone beam so as to spread evenly in the width direction of the center line connecting the center of the X-ray generator126and the center in the width direction of the X-ray detector128by the X-ray regulating unit129.

For the relatively small second physique P(M), as illustrated inFIG. 14, the mechanical turning axis X1is disposed at a position shifted in the −x-direction with respect to the center A of the imaging region R when viewed in the xyz-orthogonal coordinate system. When viewed in the XYZ-orthogonal coordinate system, the mechanical turning axis X1is disposed at a position shifted in the X-direction (in this case, in the −X-direction) in the initial state inFIG. 14(the state in which the extending direction of the turning support124is along the X-direction). The turning support124is synchronously turned about the mechanical turning axis X1while the mechanical turning axis X1is turned with the radius r(M) about the center A of the imaging region R. That is, the mechanical turning axis X1moves on a circular orbit CLd having the radius r(M).

In this case, when the distance of the X-ray generator126to the center A of the imaging region R and the distance of the X-ray detector128to the turning axis X1are compared to each other, the latter is smaller, and becomes the separation distance DP(M).

The X-ray generator126and the X-ray detector128turn around the imaging turning center IC while the imaging turning center IC is placed on the position of the center A.

The mechanical turning axis X1is located at a position LC31shifted to the direction in which the component in the −X-direction and the component in the ±Y-direction (in the example ofFIG. 14, almost zero) are combined from the center A of the imaging region R in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, the mechanical turning axis X1is located at a position LC32shifted to the direction in which the component in the +Y-direction and the component in the ±X-direction (in the example ofFIG. 14, almost zero) are combined from the center A of the imaging region R in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side, and the mechanical turning axis X1is located at a position LC33shifted to the direction in which the component in the +X-direction and the component in the ±Y-direction (in the example ofFIG. 14, almost zero) are combined from the center A of the imaging region R in timing when the X-ray generator126is located on the +Y-side while the X-ray detector128is located on the −Y-side.

Although the X-ray generator126and the X-ray detector128are not illustrated, in timing when the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is located at a position LC34shifted from the direction in which the component in the −Y-direction and the component in the ±X-direction (in the example inFIG. 14, almost zero) are combined from the center A of the imaging region R.

For the relatively large first physique P(L), as illustrated inFIG. 15, the mechanical turning axis X1is disposed at a position shifted in the −x-direction and the +y-direction with respect to the center A of the imaging region R when viewed in the xyz-orthogonal coordinate system. When viewed in the XYZ-orthogonal coordinate system, the mechanical turning axis X1is disposed at a position shifted in the X-direction (in this case, in the −X-direction) and the Y-direction (in this case, in the +Y-direction) in the initial state inFIG. 15(the state in which the extending direction of the turning support124is along the X-direction). The turning support124is synchronously turned about the mechanical turning axis X1while the mechanical turning axis X1is turned with the radius r(L) (however, r(L)>r(M)) about the center A of the imaging region R. That is, the mechanical turning axis X1moves on a circular orbit CLe having the radius r(L).

The X-ray generator126and the X-ray detector128turn around the imaging turning center IC while the imaging turning center IC is placed on the position of the center A.

The mechanical turning axis X1is located at a position LC41shifted to the direction in which the component in the −X-direction and the component in the +Y-direction are combined from the center A of the imaging region R in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, the mechanical turning axis X1is located at a position LC42shifted to the direction in which the component in the +Y-direction and the component in the +X-direction are combined from the center A of the imaging region R in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side, and the mechanical turning axis X1is located at a position LC43shifted to the direction in which the component in the +X-direction and the component in the −Y-direction are combined from the center A of the imaging region R in timing when the X-ray generator126is located on the +Y-side while the X-ray detector128is located on the −Y-side.

Although the X-ray generator126and the X-ray detector128are not illustrated, in timing when the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is located at a position LC44shifted to the direction in which the component in the −Y-direction and the component in the −X-direction are combined from the center A of the imaging region R.

In this case, when the distance of the X-ray generator126to the center A of the imaging region R and the distance of the X-ray detector128to the turning axis X1are compared to each other, the latter is smaller, and becomes the separation distance DP(L).

Because of r(L)>r(M), DP(L)>DP(M) is obtained. For the relatively large first physique P(L), the X-ray generator126turns at a position farther from the center A of the imaging region R as compared with the relatively small second physique P(M). For this reason, the X-ray generator126and the X-ray detector128hardly contact with the head P(P1) for the relatively large first physique P(L).

Consequently, the X-ray CT imaging of the imaging region R as wide as possible can be performed by the offset scan.

Although the mechanical turning axis X1is shifted in the −x-direction in the example ofFIGS. 14 and 15, the offset scan can be performed by shifting the mechanical turning axis X1in the +x-direction.

Unlike the second modification, the X-ray regulating unit129restricts the X-ray emitted from the X-ray generator126such that the X-ray is biased onto one side with respect to the center line connecting the center of the X-ray generator126and the center in the width direction of the X-ray detector128, whereby the offset scan can be performed by the same turning action as that described in the second embodiment when the horizontal symmetry axe of the X-ray cone beam deviates from the center line and the center A of the imaging region R.

A geometrical configuration of the offset scan will be described below.

The offset scan that can be considered as an embodiment in the present application is any one of the following (A) and (B).

(A) The irradiation range of the X-ray beam is biased in the direction including the component in the +x-direction with respect to the center A of the imaging region R. The irradiation range includes the center A. A region that is not irradiated with the X-ray is generated in the −x-direction. At this point, the irradiation range is irradiated with the X-ray beam while the X-ray beam is turned by at least 360°. As a result, the whole imaging region R is irradiated with the X-ray by at least 180°, and projection data corresponding to the turning of 180° is obtained.

(B) The irradiation range of the X-ray beam is biased in the direction including the component in the −x-direction with respect to the center A of the imaging region R. The irradiation range includes the center A. A region not irradiated with the X-ray is generated in the +x-direction. At this point, the irradiation range is irradiated with the X-ray beam while the X-ray beam is turned by at least 360°. As a result, the whole imaging region R is irradiated with the X-ray by at least 180°, and projection data corresponding to the turning of 180° is obtained.

In the example ofFIGS. 16 and 17, the position of the mechanical turning axis X1is shifted onto the side of the X-ray detector128from the intermediate point between the X-ray generator126and the X-ray detector128on the turning support124.

Third Modification

In a third modification, an example in which panoramic X-ray imaging is performed will be described. In the panoramic X-ray imaging, as illustrated inFIG. 16, the turning support124is turned about the mechanical turning axis X1under the control of the turning drive mechanism130. Consequently, the X-ray generator126and the X-ray detector128move to perform X-ray imaging while forming a panoramic imaging orbit Rp. For example, the panoramic imaging orbit Rp is an arc-shaped trajectory along a dental arch Ar, and the X-ray generator126and the X-ray detector128move in the arc shape outside the dental arch Ar. Consequently, the X-ray panoramic image of the whole dental arch Ar can be generated.

InFIG. 16, a panoramic imaging orbit Rpa in which the relatively small second physique P(M) is assumed is set. When the panoramic imaging is performed on the relatively large first physique P(L) with the panoramic imaging orbit Rp, there is a risk that the X-ray detector128contacts with the head P having the physique P(L) on the outside of the molar region.

For this reason, according to the physiques P(M), P(L) of the subject set by the physique setting unit151a,a passage route of the X-ray detector128is change at least in timing of irradiating a molar region Ara of the dental arch Ar with the X-ray. As this example, when the set physique of the subject is the relatively large first physique P(L), at least in timing of irradiating the molar region Ara of the dental arch Ar with the X-ray, the passage rout of the X-ray detector128can be set outside as compared with the case that the physique of the subject is the relatively smaller second physique P(M). Because the head P that is the subject is fixed by the head fixing apparatus142with the jaw as the reference, the fixed position of the front of the dental arch Ar is kept constant regardless of the physique.

As illustrated inFIG. 16, for the relatively small second physique P(M), the X-ray detector128is turned in the arc shape while the mechanical turning axis X1is moved, thereby performing the panoramic X imaging.

The mechanical turning axis X1is located at a position LC51shifted onto the +X-side from an exact middle in the substantially same Y-coordinate as molars at right and left ends of a dental arch ArM in timing when the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is located at a position LC52shifted onto the +Y-side from the Y-coordinate of the position LC51on the exact middle in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, and the mechanical turning axis X1is located at a position LC53shifted onto the −X-side from the exact middle in the substantially same Y-coordinate as the molars at the right and left ends of the dental arch ArM in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side.

On the other hand, as illustrated inFIG. 17, for the relatively large first physique P(L), the X-ray detector128is turned in the arc shape with a diameter larger than that in the above case while the mechanical turning axis X1is moved, thereby performing the panoramic X imaging. Consequently, at least in timing of irradiating the molar region Ara of the dental arch Ar with the X-ray, the panoramic imaging orbit Rpb is set such that the passage route of the X-ray detector128is set to the outside of that inFIG. 16.

The mechanical turning axis X1is located at a position LC61shifted onto the −X-side from an exact middle in the substantially same Y-coordinate as molars at right and left ends of a dental arch ArL in timing when the X-ray generator126is located on the +X-side while the X-ray detector128is located on the −X-side, the mechanical turning axis X1is located at a position LC62shifted onto the +Y-side from the Y-coordinate of the position LC61on the exact middle in timing when the X-ray generator126is located on the −Y-side while the X-ray detector128is located on the +Y-side, and the mechanical turning axis X1is located at a position LC63shifted onto the +X-side from the exact middle in the substantially same Y-coordinate as the molars at the right and left ends of the dental arch ArL in timing when the X-ray generator126is located on the −X-side while the X-ray detector128is located on the +X-side.

Because the dental arch ArL is larger than the dental arch ArM, the Y-coordinates of the positions LC61, LC63are shifted onto the −Y-side than the Y-coordinates of the positions LC51, LC53.

Consequently, in performing the panoramic X-ray imaging, the X-ray detector128can be prevented from contacting with the head while brought as close as possible to the dental arch Ar according to the size of the physique.

The above configuration is applicable to an X-ray imaging apparatus that performs the panoramic X-ray imaging without assuming the above embodiment.

Fourth Modification

An example in which the subject physique setting unit automatically recognizes the physique of the subject to set the physique of the subject will be described in fourth and fifth modifications. The term “automatically recognize the physique of the subject” means that the physique is recognized based on the output of a detector such as an X-ray detector, another sensor, or the like without receiving the direct designation operation of the size of the physique. Thus, the physique of the subject can be automatically detected and set without receiving the designation operation by the operator or the like.

In the fourth modification, as illustrated inFIG. 18, a physique setting unit210recognizes the physique of the head P based on the captured image of the head P that is the subject, strictly the captured image data, and sets the physique based on the recognition result.

In the fourth modification, the X-ray image, more specifically a cephalographic image inFIG. 19is used as the captured image of the head P. The cephalographic image is an image previously obtained before the X-ray CT imaging is performed using the X-ray detector128band the like of a cephalographic head fixing apparatus144.

The physique setting unit210includes a skeleton image extractor212and a physique decision unit214that decides the size of the physique based on an extracted skeleton image.

The skeleton image extractor212performs binarization processing and the like based on the X-ray image and the like to extract a skeleton region of the head or a boundary region of a skeleton.

The physique decision unit214decides a size L of the skeleton in a predetermined operation line or the like based on the extracted skeleton region, the skeleton boundary region, or the like. The size of the physique is decided based on the decided size L of the skeleton. For example, a table in which the range of the size of the skeleton is correlated with each of the first physique P(L) or the second physique P(M) is previously stored, and whether the size L corresponds to the first physique P(L) or the second physique P(M) is decided based on the decided size L of the skeleton and the table, and the physique is set according to the decision content.

Consequently, even if the size of the physique is not particularly set, the turning control based on the size of the physique as described in the above embodiments in the X-ray generator126and the X-ray detector128can be performed based on the captured image.

Although the example in which the captured image is the cephalometric image including the entire head is described, the captured image can be the panoramic X-ray image or the X-ray image of a part of the teeth. The captured image can be an image obtained by a visible light imaging apparatus such as a typical CCD camera. The captured image can be an image captured by another X-ray imaging apparatus or a camera. Both the recognition of the X-ray image data and the recognition of the visible light captured image can be performed. In this case, one of results of the recognition of the X-ray image data and the recognition of the visible light captured image can be used to adjust the other result.

Fifth Modification

In the fifth modification, as illustrated inFIG. 20, the head fixing apparatus142is an example of the subject holder that holds the subject, and includes the chin rest142aon which the jaw of the head P that is the subject can be placed and supported and the head holder142bthat holds the head P that is the subject from both outer sides of the head P. The head holder142bis provided with a measurement unit142cthat measures the physique of the head P held by the head holder142b.More specifically, a pair of head holders142bis openably and closably provided so as to sandwich the left and right portions of the head P. Since the pair of head holders142bis open and closed according to the horizontal width of the head P, an opening degree of the pair of head holders142bbecomes a size corresponding to the physique of the head P. The measurement unit142cmeasures the opening degree of the pair of head holders142b.It is assumed that the measurement unit142cis a variable resistor in which a resistance value changes according to the opening degree of the pair of head holders142b,an optical sensor that measures a dimension between the pair of head holders142b,or the like. The measurement unit142ccan be called a physique measure.

The physique setting unit251aincludes the measurement unit142cand a physique decision unit251b.When a signal indicating the measurement result is input from the measurement unit142cto the physique decision unit251b,the physique decision unit251bdecides the size of the physique based on the measurement signal corresponding to the opening degree. For example, a table in which the range of the opening degree is correlated with each of the first physique P(L) or the second physique P(M) is previously stored, and whether the opening degree corresponds to the first physique P(L) or the second physique P(M) is decided based on the decided opening degree and the table, and the physique is set according to the decision content.

Consequently, the turning control based on the size of the physique as described in the above embodiments in the X-ray generator126and the X-ray detector128can be performed when the head P is fixed to the head fixing apparatus142even if the size of the physique is not particularly set.

Sixth Modification

As illustrated in a sixth modification ofFIG. 21, a turning support324can include an X-ray detector moving mechanism326that moves the X-ray detector128along the X-ray irradiation direction. The X-ray detector moving mechanism326is constructed with a moving mechanism including a ball screw mechanism and a motor and a linear actuator such as a linear motor. The X-ray detector moving mechanism326is incorporated in the turning support324to move the X-ray detector128along the extending direction of the extending direction of324, and is displaced between a position DT1and a position DT2. In the position DT1, the distance in the y-axis direction to the X-ray generator126is larger than that in the position DT2. As described above, the magnification ratio can be adjusted by moving the X-ray detector128along the X-ray irradiation direction. When a motor is used as a drive source of the X-ray detector moving mechanism, the motor is an X-ray detector drive motor.

FIGS. 22A and 22Billustrate an application example of the X-ray detector moving mechanism326inFIG. 21.

InFIG. 22A, similarly toFIG. 10, with respect to the head P2having the second physique P (M), CT imaging is performed with the position of the mechanical turning axis X1aligned with the position of the center A of the imaging region R. The X-ray detector128is disposed at the position DT2, and does not touch with the head P2. When the turning inFIG. 22Ais applied to the head P1having the first physique P(L), there is a possibility that the X-ray detector128contacts with the head P1similarly toFIG. 10.

As illustrated inFIG. 22B, with respect to the head P1, the X-ray detector128is displaced to the position DT1while the mechanical turning axis X1is fixed to the position of the center A of the imaging region R, and the turning support324is turned while the separation distance to the center A of the imaging region R is increased larger than the position DT2, whereby the contact of the X-ray detector128with the head P1is avoided.

For this reason, even if the X-ray detector128is turned while the mechanical turning axis X1is fixed to the position of the center A of the imaging region R, the X-ray detector128can be moved in a far and near direction with respect to the turning axis X1according to the size of the physique. In this case, for the relatively small physique, the X-ray detector128is turned while located at the position DT1relatively close to the turning axis X1, whereby the X-ray detector128can pass through the imaging region R as close as possible to obtain the clear image. For the relatively large physique, the X-ray detector128is turned while located at the position DT2relatively far from the turning axis X1, whereby the touching of the X-ray detector128with the head P is avoided.

Common Modification

In each of the above embodiments and each of modifications, the X-ray generator and the X-ray detector have the circular turning orbit. Alternatively, the X-ray generator and the X-ray detector can turn while drawing an elliptical trajectory or a trajectory in which the circle and the ellipse are combined.

In each of the above embodiments and each of modifications, the turning trajectories of the X-ray generator and the X-ray detector are changed when the CT imaging is performed on the first physique and the second physique smaller than the first physique. However, the turning trajectories of the X-ray generator and the X-ray detector can be changed according to the sizes of at least three physiques. Alternatively, the turning trajectories of the X-ray generator and the X-ray detector can continuously be changed according to the setting of the continuous size of the physique. In any case, the turning trajectories of the X-ray generator and the X-ray detector can be controlled as in each of the above examples when the sizes of two physiques are assumed.

The configurations described in the above embodiments and the modifications can appropriately be combined as long as they are not inconsistent with each other.

This description also discloses the following aspects.

A first aspect is an X-ray CT imaging apparatus including: a supporter that is supported such that an X-ray generator and an X-ray detector are opposed to each other with a subject sandwiched between the X-ray generator and the X-ray detector; a turning motor that turns the supporter about a shaft located between the X-ray generator and the X-ray detector; a crosswise drive motor that moves the shaft in a crosswise direction, an axial direction of the shaft being set to a longitudinal direction, a direction intersecting with the longitudinal direction being set to the crosswise direction; and a circuit that performs processing of controlling the turning motor and the crosswise drive motor and processing of setting a physique of the subject from physique data of the subject. When X-ray CT imaging is performed by irradiating the subject with an X-ray generated from the X-ray generator, the crosswise drive motor moves the shaft in synchronization with turning of the supporter about the shaft using the turning motor, and the supporter is caused to perform combined motion, which allows the X-ray generator and the X-ray detector to turn about a center of an X-ray CT imaging region, and position control of the shaft is performed according to a size of the physique of the subject.

A second aspect that is the first aspect is the X-ray CT imaging apparatus in which the circuit switches between drive control in which the supporter is caused to perform the combined motion and drive control in which the supporter is turned while the shaft is fixed to a position of the center of the X-ray CT imaging region, according to the size of the physique of the subject.

A third aspect that is the first or second aspect is the X-ray CT imaging apparatus in which, according to the size of the physique of the subject set, the circuit performs the drive control in which the supporter is caused to perform the combined motion when the set physique of the subject is a first physique, and the circuit performs the drive control in which the supporter is turned while the shaft is fixed to a position of the center of the X-ray CT imaging region when the set physique of the subject is a second physique smaller than the first physique.

A fourth aspect that is any one of the first to third aspects is the X-ray CT imaging apparatus in which a distance of the shaft to the center of the X-ray CT imaging region is changed according to the set size of the physique of the subject when the combined motion is performed by the supporter.

A fifth aspect that is any one of the first to fourth aspects is the X-ray CT imaging apparatus in which, when the X-ray generator and the X-ray detector are turned around the center of the X-ray CT imaging region, assuming that a separation distance is smaller one of a distance between the center of the X-ray CT imaging region and the X-ray generator and a distance between the center of the X-ray CT imaging region and the X-ray detector, a position of the shaft with respect to the center of the X-ray CT imaging region is controlled such that the separation distance when the physique of the subject is the first physique is larger than the separation distance when the physique of the subject is the second physique smaller than the first physique according to the size of the physique of the subject.

A sixth aspect that is any one of the first to fifth aspects is the X-ray CT imaging apparatus in which, when the supporter is caused to perform the combined motion, the crosswise drive motor rotates the shaft about the center of the X-ray CT imaging region in synchronization with the turning of the supporter about the shaft using the turning motor.

A seventh aspect that is any one of the first to sixth aspects is the X-ray CT imaging apparatus in which the circuit controls adjustment of a regulation amount of the X-ray generated from the X-ray generator according to a distance of the X-ray generator to the center of the X-ray CT imaging region when the X-ray generator and the X-ray detector are turned about the center of the X-ray CT imaging region.

An eighth aspect that is any one of the first to seventh aspects is the X-ray CT imaging apparatus in which the shaft is disposed along a vertical direction.

A ninth aspect that is any one of the first to eighth aspects is the X-ray CT imaging apparatus in which the X-ray CT imaging is performed with a jaw region of a head of the subject as the X-ray CT imaging region.

A tenth aspect that is the ninth aspect is the X-ray CT imaging apparatus in which the X-ray CT imaging is performed with a part of a dental arch on the head of the subject as the X-ray CT imaging region.

An eleventh aspect that is any one of the first to tenth aspects is the X-ray CT imaging apparatus in which the X-ray generator and the X-ray detector turn around the X-ray CT imaging region to perform the X-ray CT imaging by offset scan while a part of the X-ray CT imaging region is irradiated with the X-ray generated from the X-ray generator at a position where a symmetrical axis of spread of the X-ray deviates from the center of the X-ray CT imaging region.

A twelfth aspect that is any one of the first to eleventh aspects is the X-ray CT imaging apparatus in which the circuit performs the control in which a distance of the X-ray generator to the center of the X-ray CT imaging region and a distance of the X-ray detector to the center of the X-ray CT imaging region are kept constant while the X-ray CT imaging is performed by irradiating the subject with the X-ray generated from the X-ray generator.

A thirteenth aspect that is any one of the first to twelfth aspects is the X-ray CT imaging apparatus in which the circuit sets the physique of the subject through reception of an input operation of the physique of the subject.

A fourteenth aspect that is the thirteenth aspect is the X-ray CT imaging apparatus in which the circuit sets the physique by receiving an input operation to select one of physique sizes of a plurality of selection candidates.

A fifteenth aspect that is any one of the first to the twelfth aspects is the X-ray CT imaging apparatus in which the circuit automatically recognizes the physique of the subject from at least one of data of a captured image obtained by performing X-ray imaging of the subject or data of a captured image obtained by performing visible light imaging of the subject, and sets the physique of the subject.

A sixteenth aspect that is any one of the first to twelfth aspects is the X-ray CT imaging apparatus including a subject holder that holds the subject and a physique measure that is provided in the subject holder to measure the physique of the subject held by the subject holder. The physique of the subject is set based on a measurement result of the physical measure.

A seventeenth aspect that is any one of the first to sixteenth aspects is the X-ray CT imaging apparatus in which the supporter includes an X-ray detector drive motor that moves the X-ray detector along an X-ray irradiation direction.

An eighteenth aspect that is any one of the first to seventeenth aspects is the X-ray CT imaging apparatus in which the crosswise drive motor is controlled such that the X-ray generator and the X-ray detector form a panoramic imaging orbit to perform panoramic X-ray imaging of a dental arch of the subject, and a passage route of the X-ray detector is changed at least in timing of irradiating to a molar region of the dental arch with the X-ray according to the size of the physique of the subject set by the circuit.

Further, this application discloses the following aspects. According to a first aspect of the present disclosure, an X-ray CT imaging apparatus includes: a turning support that supports an X-ray generator and an X-ray detector so that the X-ray generator and the X-ray detector are opposed to each other with a subject sandwiched therebetween; a turning drive mechanism including a turning mechanism that turns the turning support about a mechanical turning axis located between the X-ray generator and the X-ray detector and a turning axis moving mechanism that moves the mechanical turning axis in a direction intersecting with an axial direction of the mechanical turning axis; a subject physique setting unit that can set a size of a physique of the subject; and a turning controller that controls the turning mechanism and the turning axis moving mechanism. When X-ray CT imaging is performed by irradiating the subject with an X-ray generated from the X-ray generator, the turning axis moving mechanism moves the mechanical turning axis in synchronization with turning of the turning support about the mechanical turning axis using the turning mechanism, and the turning support is caused to perform combined motion, which allows the X-ray generator and the X-ray detector to turn about a center of an X-ray CT imaging region, and position control of the turning axis is performed according to a size of the physique of the subject set by the subject physique setting unit.

In a second aspect that is the X-ray CT imaging apparatus of the first aspect, drive control in which the turning support is caused to perform the combined motion and drive control in which the turning support is turned while the mechanical turning axis is fixed to a position of the center of the X-ray CT imaging region are switched according to the size of the physique of the subject set by the subject physique setting unit.

In a third aspect that is the X-ray CT imaging apparatus of the second aspect, according to the size of the physique of the subject set by the subject physique setting unit, the drive control in which the turning support is caused to perform the combined motion is performed when the set physique of the subject is a first physique, and the drive control in which the turning support is turned while the mechanical turning axis is fixed to a position of the center of the X-ray CT imaging region is performed when the set physique of the subject is a second physique smaller than the first physique.

In a fourth aspect that is the X-ray CT imaging apparatus of any one of the first to third aspects, a distance of the mechanical turning axis to the center of the X-ray CT imaging region is changed according to the size of the physique of the subject set by the subject physique setting unit when the turning support is caused to perform the combined motion.

In a fifth aspect that is the X-ray CT imaging apparatus of any one of the first to fourth aspects, when the X-ray generator and the X-ray detector are turned about the center of the X-ray CT imaging region, assuming that a separation distance is smaller one of a distance between the center of the X-ray CT imaging region and the X-ray generator and a distance between the center of the X-ray CT imaging region and the X-ray detector, a position of the mechanical turning axis with respect to the center of the X-ray CT imaging region is controlled such that the separation distance when the set physique of the subject is the first physique is larger than the separation distance when the set physique of the subject is the second physique smaller than the first physique according to the size of the physique of the subject set by the subject physique setting unit.

In a sixth aspect that is the X-ray CT imaging apparatus of any one of the first to fifth aspects, when the turning support is caused to perform the combined motion, the turning axis moving mechanism rotates the mechanical turning axis about the center of the X-ray CT imaging region in synchronization with the turning of the turning support about the mechanical turning axis using the turning mechanism.

A seventh aspect that is the X-ray CT imaging apparatus of any one of the first to sixth aspects further includes an X-ray regulating unit that adjusts a regulation amount of the X-ray generated from the X-ray generator according to a distance of the X-ray generator to the center of the X-ray CT imaging region when the X-ray generator and the X-ray detector are turned about the center of the X-ray CT imaging region.

In an eighth aspect that is the X-ray CT imaging apparatus of any one of the first to seventh aspects, the mechanical turning axis is disposed along a vertical direction.

In a ninth aspect that is the X-ray CT imaging apparatus of any one of the first to eighth aspects, the X-ray CT imaging is performed with a jaw region of a head of the subject as the X-ray CT imaging region.

In a tenth aspect that is the X-ray CT imaging apparatus of the ninth aspect, the X-ray CT imaging is performed with a part of a dental arch of the head of the subject as the X-ray CT imaging region.

In an eleventh aspect that is the X-ray CT imaging apparatus of any one of the first to tenth aspects, the X-ray generator and the X-ray detector turn around the X-ray CT imaging region to perform the X-ray CT imaging by offset scan while a part of the X-ray CT imaging region is irradiated with the X-ray generated from the X-ray generator at a position where a symmetrical axis of spread of the X-ray deviates from the center of the X-ray CT imaging region.

In a twelfth aspect that is the X-ray CT imaging apparatus of any one of the first to eleventh aspects, a distance of the X-ray generator to the center of the X-ray CT imaging region and a distance of the X-ray detector to the center of the X-ray CT imaging region are kept constant while the X-ray CT imaging is performed by irradiating the subject with the X-ray generated from the X-ray generator.

In a thirteenth aspect that is the X-ray CT imaging apparatus of any one of the first to twelfth aspects, the subject physique setting unit sets the physique of the subject by receiving an input operation of the physique of the subject.

In a fourteenth aspect that is the X-ray CT imaging apparatus of the thirteenth aspect, the subject physique setting unit sets the physique by receiving an input operation to select one of physique sizes of a plurality of selection candidates.

In a fifteenth aspect that is the X-ray CT imaging apparatus of any one of the first to the twelfth aspects, the subject physique setting unit sets the physique of the subject by automatically recognizing the physique of the subject.

In a sixteenth aspect that is the X-ray CT imaging apparatus of the fifteenth aspect, the subject physique setting unit recognizes the physique of the subject based on a captured image of the subject, and sets the physique based on a recognition result.

In a seventeenth aspect that is the X-ray CT imaging apparatus of the fifteenth aspect, the subject physique setting unit includes a measurement unit that is provided in a holder that holds the subject, and measures the physique of the subject held by the holder, and the subject physique setting unit sets the physique of the subject based on a measurement result of the measurement unit.

In an eighteenth aspect that is the X-ray CT imaging apparatus of the seventeenth aspect, the measurement unit measures an opening degree of a plurality of members that hold the subject.

In a nineteenth aspect that is the X-ray CT imaging apparatus of any one of the first to eighteenth aspects, the turning support includes an X-ray detector moving mechanism that moves the X-ray detector along an X-ray irradiation direction.

In a twentieth aspect that is the X-ray CT imaging apparatus of any one of the first to nineteenth aspects, the turning drive mechanism is controlled such that the X-ray generator and the X-ray detector form a panoramic imaging orbit to perform panoramic X-ray imaging of a dental arch of the subject, and a passage route of the X-ray detector is changed at least in timing of irradiating to a molar region of the dental arch with the X-ray according to the size of the physique of the subject.

In the X-ray CT imaging apparatus of the first aspect, the position control of the turning axis is performed according to the size of the physique of the subject set by the subject physique setting unit. Consequently, the orbits on which the X-ray generator and the X-ray detector turn can be changed to prevent the X-ray generator and the X-ray detector that turn around the subject from contacting with the subject.

In the second aspect, the orbit on which the X-ray generator and the X-ray detector turn can be changed according to the size of the physique of the subject by switching the drive control in which the turning support is caused to perform the combined motion and the drive control in which the turning support is turned while the mechanical turning axis is fixed to a position of the center of the X-ray CT imaging region according to the size of the physique of the subject set by the subject physique setting unit.

In the third aspect, when the set physique of the subject is the relatively small second physique, the turning support is turned while the mechanical turning axis is fixed to the center position of the X-ray CT imaging region, so that the position of the mechanical turning axis is stabilized to easily obtain a clear X-ray CT image. When the set physique of the subject is the relatively large first physique, the turning support is caused to perform combined motion, the X-ray generator and the X-ray detector that turn around the subject can be prevented from contacting with the subject by causing the turning support to perform the combined motion.

In the fourth aspect, when the turning support is caused to perform the combined motion, the distance of the mechanical turning axis to the center of the X-ray CT imaging region is changed according to the size of the physique of the subject set by the subject physique setting unit, which allows the orbit on which the X-ray generator and the X-ray detector turn to be changed according to the size of the physique of the subject

In the fifth aspect, when the X-ray generator and the X-ray detector are turned about the center of the X-ray CT imaging region, assuming that a separation distance is smaller one of a distance between the center of the X-ray CT imaging region and the X-ray generator and a distance between the center of the X-ray CT imaging region and the X-ray detector, the position of the mechanical turning axis with respect to the center of the X-ray CT imaging region is controlled such that the separation distance when the set physique of the subject is the first physique is larger than the separation distance when the set physique of the subject is the second physique smaller than the first physique according to the size of the physique of the subject set by the subject physique setting unit, which allows the X-ray generator and the X-ray detector turn around the subject to be prevented from contacting with the subject.

In the sixth aspect, when the turning support is caused to perform the combined motion, the turning axis moving mechanism rotates the mechanical turning axis about the center of the X-ray CT imaging region in synchronization with the turning of the turning support about the mechanical turning axis using the turning mechanism, which allows the X-ray generator and the X-ray detector to turn along the orbit as close as to the circle.

In the seventh aspect, the adjustment can be performed according to the distance of the X-ray generator to the center of the X-ray CT imaging region such that an appropriate amount of X-ray is incident on the X-ray CT imaging region.

In the eighth aspect, the X-ray generator and the X-ray detector can be turned around the axis along the vertical direction.

In the ninth aspect, when the X-ray CT imaging is performed on the jaw region, the X-ray generator and the X-ray detector can be prevented from contacting with the head according to the physique of the head of the subject.

In the tenth aspect, when the X-ray CT imaging is performed on a part of the dental arch, the X-ray generator and the X-ray detector can be prevented from contacting with the head according to the physique of the head of the subject.

In the eleventh aspect, the X-ray CT imaging of the X-ray CT imaging region as wide as possible can be performed by offset scan.

In the twelfth aspect, the X-ray CT imaging can be performed while the magnification ratio is kept constant.

In the thirteenth aspect, when the operator or the like of the apparatus performs the input operation, which allows the setting of the physique of the subject.

In the fourteenth aspect, the operator or the like of the apparatus can easily perform the input operation by selecting one of the physique sizes of the plurality of selection candidates.

In the fifteenth aspect, the physique of the subject can be automatically detected and set.

In the sixteenth aspect, the physique of the subject can be automatically detected and set based on the captured image.

In the seventeenth aspect, the physique of the subject can automatically be set when the subject is held by the holder.

In the eighteenth aspect, the physique of the subject can be set based on the opening degrees of the plurality of members that hold the subject.

In the nineteenth aspect, the magnification ratio can be adjusted by moving the X-ray detector along the X-ray irradiation direction.

In the twentieth aspect, the X-ray generator can be prevented from contacting with the head when the panoramic imaging is performed.

Although the present disclosure is described in detail, the above description is illustrative in all aspects, but the disclosure is not limited thereto.

Innumerable modifications not illustrated can be envisaged without departing from the scope of the present disclosure.

EXPLANATION OF REFERENCE SIGNS

20,124,324: turning support

30,130: turning drive mechanism

38,134: turning axis moving mechanism

40: subject physique setting unit

142: head fixing apparatus

150: main body controller

151a:physique setting unit

158: operation panel apparatus

193: physique setting image

193a:normal-size selection image

193b:large-size selection image

210,251a:physique setting unit

212: skeleton image extractor

214,251b:physique decision unit

A: center of imaging region

P(L): first physique

R: imaging region

Rp: panoramic imaging orbit

X1: mechanical turning axis