X-ray computed tomography device

Abstract

X-ray CT scanner (1), which exhibits: a lifting arm (3) which is designed to be liftable along a vertical column (2), and a rotating arm (4) for rotating about a central axis of rotation (29), which is coupled to the lifting arm (3) and holds an X-ray generation section (15) for generating and emitting X-rays and an X-ray detection section (16) for detecting the X-rays emitted by the X-ray generation section (15), wherein the X-ray generation section (15) and the X-ray detection section (16) are arranged on opposite sides of the central axis of rotation (29) such that the X-rays from the X-ray generation section (15) are detected by the X-ray detection section (16), wherein the rotating arm (4) is designed to rotate the X-ray generating section (15) and the X-ray detection section (16) while an imaging object is arranged between the X-ray generating section (15) and the X-ray detection section (16) such that the X-ray detection section (16) detects the X-rays emitted by the X-ray generating section (15) and transmitted through the imaging object to obtain imaging data for creating a CT image or a panoramic image, the device comprises: (A) an imaging mode selection device (91, 92) which is configured, (a) a panoramic imaging mode in which, during imaging, the X-ray generating section (15) and the X-ray detection section (16) are rotatably driven while the rotating arm (4) is rotated about the central axis of rotation (29) to form the panoramic image of the imaging object; (b) an offset scanning / CT mode in which the CT image of the imaging object is constructed on the basis of X-ray CT data obtained by rotating the rotary arm (4) about the central axis of rotation (29), wherein the rotary arm (4) is set in a position such that part of an area of ​​interest of the imaging object is irradiated with a cone of radiation (104) emitted from the X-ray generating section (15) and detected in the X-ray detection section (16), and (c) a normal scanning / CT mode in which the CT image of the imaging object is constructed on the basis of X-ray CT data obtained by rotating the rotary arm (4) about the central axis of rotation (29), the rotary arm (4) being set in a position such that an entirety of the area of ​​interest of the imaging object is irradiated with a cone of radiation (104) emitted from the X-ray generating section (15) and detected in the X-ray detection section (16), to select, and (B) an XY motion mechanism (18) and a rotary motor (34) which are configured, (d) to move the pivot arm (4) in a horizontal direction relative to the lifting arm (3), (e) during panorama imaging mode to move the rotating arm (4), the X-ray generation section (15) and the X-ray detection section (16) along a locus curve for a panorama image, (f) during the offset scanning / CT mode, to move the rotating arm (4) so ​​that the cone of radiation (104) emitted from the X-ray generating section (15) to the X-ray detection section (16) irradiates the part of the area of ​​interest (105) of the imaging object, and (g) during normal scanning / CT mode, to move the rotating arm (4) so ​​that the cone of radiation (104) emitted from the X-ray generating section (15) to the X-ray detection section (16) irradiates the entirety of the area of ​​interest (105) of the imaging object; wherein the XY motion mechanism (18) is configured to move the rotary arm (4) during the offset scanning / CT mode such that the central axis of rotation (29) is positioned at the center of an imaging area (101) of the imaging object containing the area of ​​interest (105), that the rotary arm (4) has a fixed distance from the center of the imaging area (101) along a first direction, that the center of the imaging area (101) is located within the beam cone (104), and that the X-ray detection section (16) is brought closer to the area of ​​interest (105) than during the normal scanning / CT mode by moving the rotary arm (4) along a second direction perpendicular to the first direction and pointing from the X-ray generation section to the X-ray detection section, or the XY motion mechanism (18) is designed to move the rotary arm (4) during the offset scanning / CT mode such that the central axis of rotation (29) is positioned at the center of the imaging area (101), that the rotary arm (4) has a fixed distance from the center of the imaging area (101) along the first direction, that the center of the imaging area (101) is located within the beam cone, and that the X-ray generating section (15) is brought closer to the area of ​​interest (105) than during the normal scanning / CT mode by moving the rotary arm (4) along a second direction perpendicular to the first direction and pointing from the X-ray generating section to the X-ray detection section.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to an X-ray computed tomography (CT) device for dentistry or a maxillofacial area. More specifically, the present invention relates to an X-ray CT device capable of performing local X-ray CT on a specific tooth or the like as a region of interest in dentistry or a maxillofacial area, and performing panoramic X-ray imaging on a curved cross-section of a dental arch, a temporomandibular joint, and the like. Description of the state of the art

[0002] Japanese Patent Publication No. 10-225455 (A) discloses an X-ray CT apparatus for dental diagnosis. This X-ray CT apparatus is one that incorporates local X-ray computed tomography (hereinafter referred to as "CT") scanning along with a panoramic X-ray imaging mode. This X-ray CT apparatus is capable of selecting the X-ray CT mode and the panoramic X-ray imaging mode and is characterized as follows: When the X-ray CT mode is selected, a central rotation axis is fixed on a central axis of a region of interest, and when the panoramic X-ray imaging mode is selected, a rotary arm including an X-ray generator and an X-ray detector is rotated while the central rotation axis moves along a locus for panoramic X-ray imaging during imaging.

[0003] Japanese Patent No. 3540916 (B) discloses a three-dimensional X-ray CT scanner having, in a hollow rotating body, an X-ray generator and an X-ray detector which are opposed to each other with a horizontal central axis (rotation axis) therebetween.In this apparatus, while this X-ray generator and the X-ray detector are rotated with respect to an imaging object positioned inside the rotating body, X-rays radiated from the X-ray generator and transmitted through the imaging object are detected in the X-ray detector, and by means of the X-ray image detected in the X-ray detector, a three-dimensional tomographic image can be reconstructed, so that an offset scanning CT method by which a three-dimensional CT image is obtained in a wider range than a field of view of a two-dimensional X-ray detector is used in addition to a so-called normal scanning CT method by which a CT image is obtained by irradiating the entire imaging object with X-rays.

[0004] This offset scanning / CT method has the advantage of being able to perform X-ray CT in a wider range than the field of view angle of the two-dimensional X-ray detector, since a part of the region of interest of the imaging subject can be irradiated with X-rays at any time during imaging, as comparable to the normal scanning / CT method of constantly irradiating the entire region of interest of the imaging subject with X-rays at any time during imaging.

[0005] DE 197 54 670 B4 discloses an X-ray imaging device comprising: an X-ray source for generating X-ray radiation; an X-ray image recording device for capturing X-ray radiation passing through an object; a support device for holding the X-ray source and the X-ray image recording device in such a way that they face each other across the object; a device frame for holding the support device; an adjustment device for adjusting the support device with respect to the device frame; and a switching device for switching between a CT mode in which a partial CT image is recorded and a panorama mode in which a tomographic panoramic image is recorded.Here, the adjustment device is constructed such that when the CT mode is selected, it adjusts the X-ray source and the X-ray image recording device along a path for CT image recording during a partial CT image recording process, while when the panoramic mode is selected, it adjusts the X-ray source and the X-ray image recording device along a path for panoramic image recording during a panoramic image recording process.

[0006] In “Analysis of Novel Offset Cone-Beam Computed Mammotomography System Geometry for Accomodating Various Breast Sizes” by McKinley et al., an offset scanning method for a mammography device is described.

[0007] WO 2006 / 013325 A1 discloses an X-ray device comprising an X-ray source emitting a conical beam centered with respect to a beam axis, a collimator that limits the beam, and a two-dimensional detector mounted on a mount that can rotate about a rotation axis. The collimator has a first state in which the collimated beam is aligned with the rotation axis and a second state in which the collimated beam is offset from the rotation axis.

[0008] US 6,546,068 B1 discloses a movement mechanism that moves a radiation detector into different positions in which image data is recorded. The various image data are then combined into an overall image.

[0009] DE 196 11 451 discloses a digital X-ray imaging device comprising an X-ray generator for emitting X-rays onto an object; an X-ray image generating device for capturing an image of X-rays that have passed through the object; a device for displacing the X-ray generator and the X-ray image generating device, which are arranged opposite each other, relative to the object; a signal processing device for generating a tomographic image according to an image generation signal from the X-ray image generating device; and a device for displaying the tomographic image generated by the signal processing device. The X-ray image generating device includes a MOS sensor with a number of two-dimensionally arranged light-receiving pixels. Summary of the invention

[0010] There is a problem with conventional X-ray CT devices for jaw / facial imaging in dentistry and the like in that, while the normal scanning / CT method is a dominant method, in the case of performing CT by capturing an area not smaller than the field of view detectable by a two-dimensional X-ray sensor, an enlarged two-dimensional X-ray sensor is required, which causes an increase in cost.

[0011] In view of the above situation, it is an object of the present invention to provide a novel X-ray imaging apparatus capable of performing CT on a region of interest such as a jaw / face by an offset scanning / CT method using a relatively small two-dimensional X-ray sensor, and also capable of performing panoramic X-ray imaging, and to provide a novel X-ray imaging apparatus capable of switching the method to a normal scanning / CT method in the case where the region of interest is smaller than a field of view angle of the two-dimensional X-ray sensor.

[0012] This problem is solved by the subject matter of the independent claim. Further developments are specified in the dependent claims.

[0013] According to the X-ray imaging device of the present invention, a panoramic imaging mode or an offset scan / CT mode can be arbitrarily selected by the imaging mode selection means by selecting the panoramic imaging mode or the offset scan / CT mode. Thus, it is possible to perform panoramic imaging and an offset scan / CT using an inexpensive, small-sized two-dimensional X-ray sensor, and, when necessary or upon request, it is possible to continuously obtain a panoramic image and an offset scan / CT image that is optimal for treatment.Accordingly, when a corresponding position of a region of interest is obtained by panoramic imaging with a large imaging range and an imaging position is then adjusted to perform the offset scan / CT on the region of interest, it is possible to perform CT in a larger range than a conventional range, thus performing CT in a large range while keeping the cost low.

[0014] According to the X-ray imaging apparatus of the present invention, while the offset scan / CT mode and the normal scan / CT mode are selected as necessary, the convenience in the CT increases, and thus with the use of the CT, it is possible to obtain a CT image with even higher resolution.

[0015] According to the X-ray imaging apparatus of the present invention, a slit is selectively arranged corresponding to the panoramic imaging mode or the CT mode, and thus it is possible to obtain the optimal X-ray beam required for each imaging mode.

[0016] According to the X-ray imaging apparatus of the present invention, the first or second slit is set to use only an X-ray beam inclined at a certain angle from the central X-ray irradiation axis, and it is thus possible to efficiently obtain clean X-ray imaging data.

[0017] According to the X-ray imaging apparatus of the present invention, the driving means is provided which moves the central rotation axis of the central arm in accordance with the panoramic imaging mode or the CT mode selected by the imaging mode selecting means by selecting one of the two modes, and therefore it is possible to obtain an arbitrary locus of the rotating means which is optimal for imaging. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an X-ray imaging apparatus of a first example according to the present invention; Fig. 2 is a front view of the X-ray imaging apparatus of the first example according to the present invention; Fig. 3 is a right side view of the X-ray imaging apparatus of the first example according to the present invention; Fig. 4 is a left side view of the X-ray imaging apparatus of the first example according to the present invention; Fig. 5 is a perspective view illustrating the X-ray imaging apparatus of the first example according to the present invention and a test article positioned therein; Fig. Fig. 6 is a perspective view of a part cut from a rotary arm of the X-ray imaging apparatus of the first example shown in Fig. 1 is shown; Fig. 7 is a cross-sectional view illustrating an XY movement mechanism of the rotary arm of the first example; Fig. 8 is a view, viewed from below, of the XY movement mechanism of the rotary arm of the first example; Fig. 9 is a cross-sectional view illustrating an XY moving mechanism of an imaging subject of a second example according to the present invention; Fig. 10 is a cross-sectional view of an X-ray generating section; Fig. 11 is a perspective view illustrating a beam forming plate and the like installed in the X-ray generating section; Fig. 12 is a front view of a part cut out of the rotary arm; Fig. 13 is a perspective view of an X-ray detector; Fig. 14 is a control block diagram for the X-ray imaging device; Fig. 15 is a flowchart illustrating a control program for the X-ray imaging apparatus; Fig. 16 is a sample view explaining an initial setting process for a reduced CT mode; Fig. 17 is a pattern view illustrating an operation of the rotary arm in the reduced CT mode; Fig. 18 is a sample view explaining an initial setting process for an extended CT mode; and Fig. 19 is a sample view illustrating an operation of the rotary arm in an enhanced CT mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] With reference to the accompanying drawings, some embodiments of the X-ray imaging device according to the present invention will be described below. It should be noted that although terms denoting a specific direction or location (e.g., "upper," "lower," "left," "right," and other terms including those terms) are used in the following description, these terms are used for the purpose of facilitating visual understanding of the configurations illustrated in the drawings and should not be used to define a technical scope of the invention.

[0019] The Fig. 1 to 5 show the respective appearances of an X-ray CT apparatus according to an embodiment of the present invention. The X-ray CT apparatus is capable of performing three-dimensional X-ray computed tomography (computed tomography: hereinafter referred to as "CT") in addition to a variety of imaging techniques conventionally widely known in the field of dentistry (e.g., panoramic imaging, linear tomography, linear scanning imaging, scanogram imaging). It should be noted that, although the X-ray CT apparatus of the embodiment is an X-ray CT apparatus for dentistry, the application of the present invention is not limited to the X-ray CT apparatus for dentistry; rather, the present invention is equally applicable to an X-ray CT apparatus for other types of medical use.For example, although the X-ray CT apparatus shown in the figures is a vertical X-ray imaging apparatus and is used with a test object in a standing state, the present invention is also applicable to a so-called lateral X-ray imaging apparatus which is used with a test object held in a horizontally lying state.

[0020] As is apparent from the figures, an X-ray CT apparatus (hereinafter simply referred to as “imaging apparatus”) 1 generally comprises a vertical column 2 fixed on a floor surface; a lifting arm (first frame) 3 provided so as to be liftable along the vertical column 2; and a rotating arm (second frame) 4 rotatably connected to the lifting arm 3 with a vertical central rotating axis (will be described later with reference to the Fig. 6 to 8) is coupled to the center.

[0021] As it is in the Fig. 3 and Fig. 4, the lifting arm 3 as a whole has a substantially U-shape, and approximately comprises a vertical arm portion 5 liftably coupled to the vertical column 2, and an upper arm portion 6 and a lower arm portion 7 each extending forward (toward the left side of Fig. 3 and the right side of Fig. 4). As will be described later, the upper arm portion 6 rotatably supports the rotary arm 4, which is arranged between the upper arm portion 6 and the lower arm portion 7. As shown in Fig. As shown in Fig. 5, the lower arm portion 7 has thereon a positioning mechanism 8 that positions a person's head as an imaging subject. For example, the positioning mechanism 8 of the X-ray CT apparatus 1 of the embodiment includes a chin rest 9 that supports a jaw thereon, a pair of lateral direction control members 10 that support the head of the test subject as the imaging subject from the right and left sides thereof, and a pair of handles 11 that are held by the positioned person with his or her two hands so as to keep himself or herself motionless.

[0022] As it is in the Fig. 1 and Fig. 2, the rotary arm 4 as a whole has a substantially inverted U-shape, and approximately includes: a horizontal arm portion 12 rotatably suspended by the upper arm portion 6 through a coupling mechanism described later, in which it is suspended below the upper arm portion 6; and first and second suspension portions 13 and 14 extending downwardly from right and left ends of the horizontal arm portion 12, respectively. The first suspension portion 13, which is provided on a right side of Fig. 2, has an X-ray generating section 15, and the second suspension section 14, which is arranged on a left side of Fig. 2, includes an X-ray detection section 16. The X-ray generation section 15 and the X-ray detection section 16 oppose each other at a prescribed spacing. A horizontal direction in which the X-ray generation section 15 and the X-ray detection section 16 oppose each other is referred to as an "X direction," a horizontal direction perpendicular thereto is referred to as a "Y direction," and a height direction is referred to as a "Z direction."

[0023] The coupling mechanism (second coupling means) coupling the lifting arm and the rotating arm 4 is described with reference to the Fig. 6 to 8. The coupling mechanism includes an XY movement mechanism (first and second movement mechanisms) 18 housed in a rotary arm housing 17. The XY movement mechanism 18 includes a pair of Y-direction guide rails 19Y fixed to the rotary arm housing 17 and extending in the Y direction, a Y-direction movement arm 20Y capable of reciprocating in the Y direction along those Y-direction guide rails 19Y, a pair of X-direction guide rails 20X fixed to the Y-direction movement frames 20Y and extending in the X direction, and an X-direction movement frame 20X capable of reciprocating in the X direction along those X-direction guide rails 19X.The Y-direction moving frame 20Y is coupled to a Y-direction moving motor 23Y fixed to the rotary arm housing 17 through a corresponding drive transmission mechanism (for example, a mechanism including a screw 24Y drivingly coupled to the motor 23Y and a groove 25Y engaged therein and fixed to the frame 20Y), so that the Y-direction moving frame 20Y moves in the Y direction based on the drive of the Y-direction moving motor 23Y.Similarly, the X-direction moving frame 20X is coupled to the X-direction moving motor 23X, which is attached to the Y-direction moving frame 20Y through a corresponding drive transmission mechanism (for example, a mechanism including a screw 24X drivingly coupled to the motor 23X and a groove 25X engaged therein and fixed to the X-direction moving frame 20X), so that the X-direction moving frame 20X moves in the X direction based on the drive of the X-direction moving motor 23X.As described below, in the XY movement mechanism 18, the pair of Y-direction guide rails 19Y, the Y-direction movement frame 20Y, the Y-direction movement motor 23Y, and the drive transmission mechanism therefor (screw 24Y, groove 25Y) constitute the Y-direction movement mechanism, and the pair of X-direction guide rails 19X, the X-direction movement frame 20X, the X-direction movement motor 23X, and the drive transmission mechanism therefor (screw 24X, groove 25X) constitute the X-direction movement mechanism. Therefore, driving the movement motors 23X and 23Y can result in a corresponding movement of the central rotation axis of the rotary arm.

[0024] A central rotary shaft 29 in a cylindrical shape or a columnar shape, which couples the lifting arm 3 and the rotary arm 4, is fixed to the X-direction moving frame 20X at its upper end and rotatably supported by an axle bearing 31 (first coupling means) installed in the rotary arm 4. Further, a belt take-up portion 32 with a circular shape in its cross section is formed at a lower end of the central rotary shaft 29, and a belt 33 is wound around this belt take-up portion (pulley). The belt 33 is also drivingly coupled to another belt take-up portion 32, to which a rotary motor 34 installed in the rotary arm 4 is drivingly coupled, so that the central rotary shaft 29 and the rotary arm 4 attached thereto are rotated based on the drive of the rotary motor 34. These configurations are those basically used in the X-ray CT device for dentistry.

[0025] Furthermore, as stated in Fig. As shown in Figure 9, in a second example according to the present invention, the rotary arm 4 is supported by high-strength columns 2a, 2a, and an upper frame 2b. The rotary arm 4 is rotated uniaxially, and the central rotation axis 29 is fixed. A region of interest is positioned by the positioning mechanism 8 with the XY movement mechanism 18.

[0026] The XY movement mechanism 18 includes the pair of Y-direction guide rails 19Y fixed to a seat 8aa of a chair 8a and extending in the Y-direction, the Y-direction movement frame 20Y capable of reciprocating in the Y-direction along those Y-direction guide rails 19Y, the pair of X-direction guide rails 19X fixed to a leg 8ab of the chair 8a and extending in the X-direction, and the X-direction movement frame 20X capable of reciprocating in the X-direction along those X-direction guide rails 19X.The Y-direction movement frame 20Y is coupled to the Y-direction movement motor 23Y, which is fixed to the chair 8a through a corresponding drive transmission mechanism (for example, a mechanism including the screw 24Y drivingly coupled to the motor 23Y and the groove 25Y captured therein and fixed to the frame 20Y), so that the Y-direction movement frame 20Y moves in the Y direction based on the drive of the Y-direction movement motor 23Y.Similarly, the X-direction movement frame 20X is coupled to the X-direction movement motor 23X, which is fixed to the chair 8a through a corresponding drive transmission mechanism (for example, a mechanism including the screw 24X drivingly coupled to the motor 23X and the groove 25X captured therein and fixed to the X-direction movement frame 20X), so that the X-direction movement frame 20X moves in the X direction based on the drive of the X-direction movement motor 23X.As described herein, in the XY movement mechanism 18, the pair of Y-direction guide rails 19Y, the Y-direction movement frame 20Y, the Y-direction movement motor 23Y, and the drive transmission mechanism therefor (screw 24Y, groove 25Y) constitute the Y-direction movement mechanism, and the pair of X-direction guide rails 19X, the X-direction movement frame 20X, the X-direction movement motor 23X, and the drive transmission mechanism therefor (screw 24X, groove 25X) constitute the X-direction movement mechanism. Thus, driving the movement motors 23X and 23Y can result in a corresponding movement of the central rotation axis of the central axis.

[0027] Note that in the second example, the height (Z direction) can also be adjusted by the chair 8a. Similar to the X-direction movement mechanism and the Y-direction movement mechanism, a Z-direction movement mechanism is composed of a Z-direction movement motor 23Z and its drive transmission mechanism (slot 24Z, slot 25Z), and is capable of arbitrarily moving the height of the region of interest of the imaging subject.

[0028] Furthermore, the first example and the second example may be combined so as to provide corresponding XY movement mechanisms on the adjacent sides of the rotary arm 4 and the chair 8a.

[0029] As it is in Fig. As shown in Figure 10, the X-ray generating section 15 includes an X-ray generating section housing 35 with various configurations, which are described below. The X-ray generating section housing 35 is coupled to the rotating arm housing 17 through the X-ray generating section rotating mechanism 36.Specifically, in the X-ray imaging apparatus of the embodiment, an X-ray generating section rotating mechanism 36 includes an X-ray generating section rotating motor 37 fixed to the inside of the rotating arm housing 17, a vertical axis 38 rotatably mounted to the rotating arm housing 17, a gear mechanism 39 drivingly coupling the X-ray generating section rotating motor 37 and the vertical axis 38, and a fixed member 40 fixed to the X-ray generating section housing 35 and the vertical axis 38, so that the X-ray generating section housing 35 rotates with the vertical axis 38 as the center based on the drive of the X-ray generating section rotating motor 37.The X-ray generating section housing 35 is rotated horizontally to rotate the X-ray generating section toward a head fixing device for cephalometric imaging, not shown, in a cephalometric image.

[0030] An X-ray tube (X-ray generator) 41 as an X-ray generation source is housed within the X-ray generation section casing 35. The X-ray tube 41 is shielded by an X-ray shielding box 42 except for a portion (a portion on the left side of Fig. 9) opposite the X-ray detection section 16. The X-ray shielding box 42 has a beam formation plate 50 in the area opposite the X-ray detection section 16, and a beam formation mechanism 44 is arranged on this beam formation plate 50. As shown in Fig. 11, the beam forming mechanism 44 includes a support frame or block 47 which is liftably supported along a plurality of vertical guide rails 46 by the plurality of guide rollers 45. The block 47 includes an X-ray through-opening 48 (see Fig. 10) that guides X-rays emitted from the X-ray tube 41 toward the X-ray detection section 16, and is coupled to a block lifting motor 49 fixed to the X-ray generation section housing 35 by, for example, a spring mechanism, to enable up-and-down movement of an irradiation angle of the X-rays based on the drive of the block lifting motor 49, so that a variety of angles and locations can be imaged. It is therefore possible to move the irradiation angle of the X-rays up and down without moving the X-ray generation section 15 up and down.

[0031] At this time, the image can be magnified by an X-ray detection device 71 located in Fig. 13. Furthermore, although not shown, with the movement of a mechanism for moving the X-ray detection device 71 up and down within the X-ray detector 64, imaging can be performed even with a small X-ray detection device.

[0032] A beam formation plate 50 having a plurality of beam formation tips as beam formation means for forming an X-ray beam emitted from the X-ray tube 41 is arranged at the front of the block 47, specifically, on the outside of the X-ray through-hole 48. The beam formation plate 50 is supported by a slot moving means which is horizontally movable by a plurality of guide rollers 51 fixed to the front surface of the block 47. The slot moving means includes a coupling arm 52 coupled to the beam formation plate 50. A groove 53 fixed to the coupling arm 52 is engaged with a horizontal screw shaft 54 ​​rotatably supported by the block 47. Furthermore, the horizontal screw shaft 54 ​​is coupled to a beam formation plate moving motor 55 fixed to the block 47.Therefore, the beam formation plate 50 can move the front of the block 47 right and left to apply a desired X-ray beam.

[0033] In the exemplary embodiment, the beam formation plate 50 has three beam formation slots (primary formation slots). Specifically, these three beam formation slots include a beam formation transmission opening 56 (first slot) for CT in a rectangular or square shape (e.g., 120 mm long and 120 mm wide), a beam formation transmission opening 57 (second slot) for panoramic imaging, which is vertically oriented (e.g., 150 mm long and 6 mm wide), and a beam formation transmission opening 58 for cephalometric imaging, which is also vertically oriented (e.g., 22 mm long and 6 mm wide).Therefore, in a state where the beam formation transmission port 56 for CT is opposed to the X-ray tube 41 through the X-ray transmission port 48, an X-ray cone extending in a pyramidal shape is radiated from the X-ray generation section 15 toward the X-ray detection section 16. In the case of using such a beam cone for CT, it is possible to perform CT, for example, in an area with a diameter on the order of 60 mm and a height on the order of 60 mm as an imaging area.

[0034] In the present embodiment, since the length and width of the beam forming transmission aperture 56 for CT are the same, the cross section of the X-ray beam orthogonal to the scanning direction has a square shape. In a state where the beam forming transmission aperture 57 for panoramic imaging or the beam forming transmission aperture 58 for cephalometric imaging opposes the X-ray tube 41 through the X-ray transmission aperture 48, a narrow X-ray beam is radiated from the X-ray generating section 15 toward the X-ray detecting section 16 in a long, flat plate shape with a cross section having a longitudinal length greater than its lateral length, although strictly speaking, in a pyramid shape.

[0035] As it is in Fig. 12, the X-ray detection section 16 includes an X-ray detection section housing 59 which encloses a variety of configurations which will be described below,

[0036] Inside the X-ray detection section housing 59, a detector holder 65 is provided for accommodating an X-ray detector (X-ray detection section) 64 comprising a solid-state imaging device (CCD) formed by arranging a semiconductor imaging device in the longitudinal and lateral directions. The detector holder 65 is movably supported in the horizontal direction along a holder guide rail 66 and coupled to the X-ray detection section moving motor 67, which is attached to the X-ray detection section housing 59, so as to move in the horizontal direction based on the drive of the X-ray detection section moving motor 67. The CCD is not necessarily attached to the X-ray detection section, but a flat panel detector (FPD) such as a MOS sensor and a fluorescent X-ray amplifier tube (XII) may be attached.

[0037] As it is in Fig. 13, the detector holder 65 has a plurality of beam formation slits (secondary formation slit) 68, 69, 70 in shapes corresponding to the foregoing plurality of beam formation transmission openings 56, 57, 58 in the X-ray generation section 15, and based on the drive of the X-ray detection section moving motor 67 according to the imaging mode, the beam formation slit 68, 69 or 70 in the X-ray detection section 16 corresponding to the beam transmission opening in the X-ray generation section 15 is positioned in the extension of the X-ray tube 41 and the beam formation transmission openings 56, 57 or 58 in the X-ray generation section 15 in accordance with a selection signal of the imaging mode selecting means.The X-ray detector 64 includes an X-ray detection device 71 obtained by arranging image pickup devices in a nearly square shape corresponding to the beam formation slit 68; and an X-ray detection device 72 obtained by arranging image pickup devices in a shape vertically aligned corresponding to the vertically directed beam formation slits 69 and 70. The X-ray detector 64 is inserted into a slot 73 formed in the detector holder 65. The X-ray detection device 71 is arranged behind the beam formation slit 68 in X-ray CT, and the X-ray detection device 72 is arranged behind the beam formation slits 69 and 70 in panoramic imaging or cephalometric imaging.

[0038] Fig. Figure 14 is a control block diagram of a plurality of motors and the like included in the X-ray CT apparatus 1. As shown in the figure, the X-ray imaging apparatus includes a controller (CPU) 94. The CPU 94 is connected to the foregoing plurality of motors, namely, the Y-direction movement motor, the X-direction movement motor 26, the rotation motor 34, the X-ray generation section rotation motor 37, the block lifting motor 49, the beam formation plate movement motor 55, and the X-ray detection section movement motor 67. These motors are connected to respective rotation detecting sensors (e.g., encoders) 81 to 88 for the purpose of detecting the amount of rotation thereof and controlling the drive of the motors based on the detected amount of rotation, and outputs of these sensors 81 to 88 are connected to the CPU 94.

[0039] The CPU 94 is also connected to the X-ray tube 41 and a plurality of memory sections. The memory sections include motion locus data (Read Only Memory: ROM) 95 and an X-ray image storage section (Random Access Memory: RAM) 96.The ROM 95 stores the following information during imaging (including the operations before and after imaging) in accordance with each imaging mode described later: an amount of movement of the central rotation axis 29 in an XY direction, the rotation of the central rotation axis 29 (rotation angle of the rotary arm 4), the rotation angle of the X-ray generating section housing 35 and the X-ray detecting section housing 59 with respect to the rotary arm 4, an amount of movement in the up-and-down and horizontal directions of the block 47 and an amount of movement in the horizontal direction of the beam formation plate 50 in the X-ray generating section 15, and the amount of movements of the X-ray detector 64 and the detector holder 65 in the X-ray detecting section 16 in the horizontal direction.Specifically, the amount of movement of the central rotary axis 29 and the amount of movement of the rotary arm 4 are defined by data, where the parameters are time and a corresponding value of an XY coordinate system composed of axes in two orthogonal directions (for example, a back-and-forth direction in which the upper and lower arm sections 6 and 7 protrude into the lifting arm 3 and a horizontal direction orthogonal thereto) on the horizontal plane. The coordinate value can be given by a polar coordinate instead of the XY coordinate system.

[0040] The RAM 96 stores necessary information as needed. For example, as shown in the figure, the X-ray detector 64 is electrically connected to the CPU 94 while mounted on the detection section 16, and image data obtained in the X-ray detector 64 through X-ray imaging is stored in the RAM 96 as needed.

[0041] The CPU 94 is further provided with an imaging start switch 90 for starting X-ray imaging, an imaging mode selection switch 94 for switching to an imaging mode such as the normal scan / CT mode, the offset scan / CT mode, the panoramic X-ray imaging mode, and the cephalometric imaging mode, a switching switch 93 for switching between a reduced (wide area) imaging mode in which a wide area of ​​an imaging subject is imaged and an enlarged (narrow) imaging mode in which a narrow area of ​​the imaging subject is enlarged and imaged, and is connected to a communication section 97 for communicating with a computer, not shown.

[0042] A basic operation of the X-ray imaging apparatus having such a configuration will be described with reference to the block diagram of Fig. 14 and a flow chart of Fig. 15. First, as described in the Fig. 5 and Fig. 9, the imaging object is positioned in front of the image in the X-ray CT device 1 by the positioning mechanism 8. At this time, the imaging object is in the Fig. 5, in front of the lower arm portion 7 of the lifting arm 3, holds the handles 11 with both hands, and places his or her jaw on the chin rest 9, while a right and left movement of his or her head is restricted by the right and left lateral direction control element 10. Furthermore, the subject of the image sits in the position shown in Fig. 9, on the chair 8a while his or her head is in the state to be restricted so as to remain immobilized by a head locking device 8b.

[0043] An operator operates the imaging mode selection switch 91 to select an imaging mode (panoramic imaging, CT, or the like). Further, when the CT mode is selected, a normal scan / CT - offset scan / CT mode selection switch 92 is operated to select either the normal scan / CT mode or the offset scan / CT mode.It should be noted that the normal scanning / CT mode is a mode in which the rotary arm 4 is rotated with the central rotation axis 29 as the center, and X-rays radiated from the X-ray generation section 15 and transmitted through the entire region of interest 105 of the imaging subject are detected in the X-ray detection section 16, and based on the information contained in the X-rays transmitted through the entire region of interest 105 of the imaging subject and detected in the X-ray detection section 16, a tomographic image of an imaging subject disposed between the X-ray generation section 15 and the X-ray detection section 16 is constructed.Furthermore, the offset scan / CT mode is a mode in which the rotary arm 4 is rotated with the central rotation axis 29 as the center, and X-rays radiated from the X-ray generation section and transmitted through a part of the region of interest 105 of the imaging subject are detected in the X-ray detection section 16, and based on the information included in the X-rays transmitted through the part of the region of interest 105 of the imaging subject and detected in the X-ray detection section 16, a tomographic image of the imaging subject disposed between the X-ray generation section 15 and the X-ray detection section 16 is constructed.In the present embodiment, in the normal scan / CT mode, a CT image of the imaging subject is constructed based on the X-ray imaging data obtained by arranging a center 100 of the region of interest 105 of the imaging subject, which is irradiated by the X-ray generating section 15 and detected in the X-ray detecting section 16, on the same axis as the central rotation axis 29 and the rotating center.

[0044] In the normal scan / CT mode, while imaging is performed with the region of interest 105 constantly present in a cone beam 104 regardless of the rotation angle of the rotary arm 4, an image can be reconstructed based on the X-ray transmission information obtained during the 180° rotation of the rotary arm. Furthermore, the rotary arm is preferably rotated 360° for reconstructing a final image. Imaging can be performed over a wide range in the offset scan / CT mode compared to the normal scan / CT mode.

[0045] Moreover, for example, according to the offset scan / CT mode, when an FPD having a size of 120 mm × 120 mm of the present example is used, imaging can be performed in an area having a diameter on the order of 120 mm and a height on the order of 60 mm, whereas in the normal scan / CT mode, imaging can only be performed in an area having a diameter on the order of 60 mm and a height on the order of 60 mm.

[0046] When the panoramic imaging mode has been selected, the CPU 94 reads a program (not shown) corresponding to the panoramic imaging mode from the ROM 95 and, if necessary, drives one or more of the Y-direction moving motor 23Y, the X-direction moving motor 23X, and the rotary motor 34 simultaneously or sequentially based on the read program to move the rotary arm 4, the X-ray generating section 15, and the X-ray detecting section 16 to initial imaging positions (step #2). Furthermore, the CPU 94 drives the beam formation plate moving motor 55 to provide the beam formation transmission aperture 57 for panoramic imaging opposite the X-ray tube 41 in accordance with the selected panoramic imaging mode.

[0047] After completing the aforementioned preparation, when a command to start panoramic imaging is input by operating the imaging start switch 90 (step 3), the CPU 94 drives the Y-direction moving motor 23Y, the X-direction moving motor 23X, the rotary motor 34, and the like based on a program read from the ROM 95, and also activates the X-ray tube 41 to generate X-rays (step 5). As a result, while the rotary arm 4, the X-ray generating section 15, and the X-ray detecting section 16 move along loci indicated by the program, the X-rays emitted from the X-ray tube 41 are applied to the imaging subject through the X-ray transmission port 48 of the block 47 and the beam formation transmission port 57 for panoramic imaging of the beam formation plate 50.The X-rays transmitted through the imaging subject are detected by the X-ray detector 64 through the beam formation slit for panoramic imaging of the X-ray detector 64 in the X-ray detection section 16. The X-ray detection section 16 transfers data corresponding to the acquired X-ray image to the RAM 96 at regular time intervals or after completion of imaging. The imaging data stored in the RAM 96 is transferred to a computer through the communication section 97 and subjected to a process necessary therein to be displayed on a screen (not shown). A typical imaging method in panoramic X-ray imaging is a well-known method, namely, an imaging method in which frame images are superimposed with a predetermined shift.Furthermore, panoramic X-ray imaging can be performed before CT to define a region of interest to be subjected to CT.

[0048] When the CT mode has been selected by the imaging mode selection switch 91, the CPU 94 determines either the normal scan / CT mode (first imaging mode) or the offset scan / CT mode (second imaging mode) based on a signal from the normal scan / CT and offset scan / CT mode selection switch 93 (step #6).

[0049] When the normal scanning / CT mode has been selected, the CPU 94 drives the beam formation plate moving motor 55 to expose the beam formation transmission port 56 for CT in accordance with the selected CT mode to the X-ray tube 41. Next, the CPU 94 reads a program (not shown) in accordance with the selected normal scanning / CT mode from the ROM 95 and, if necessary, drives one or more of the Y-direction moving motor 23Y, the X-direction moving motor 23X, and the rotary motor 34 simultaneously or sequentially based on the read program to move the rotary arm 4 to the initial imaging position (step 7). Typically, in this state, the center of the drive axis 30 is placed on a line connecting the X-ray generating section 15 (center of the X-ray tube 41) and the X-ray detecting section 16 (center of the X-ray detecting device 71).

[0050] Next, when a command to start imaging is input by operating the imaging start switch 90 (step 8), the CPU 94 activates the X-ray tube 41 to generate X-rays and also drives a necessary motor in accordance with the above program (step 9). At this time, the rotation speed of each motor is detected by the corresponding sensors 81 to 88, and using this detection result, the rotation speed of each motor is controlled. The X-rays emitted from the X-ray tube 41 are applied to the imaging subject through the X-ray transmission port 48 of the block 47 and the CT beam formation transmission port 56 of the beam formation plate 50.The X-rays transmitted through the imaging subject are detected by the X-ray detector 64 through the beam formation slit for panoramic imaging of the X-ray detector 64 in the X-ray detection section 16. The X-ray detection section 16 stores data corresponding to the detected X-ray image in the RAM 96 at regular time intervals. The image data stored in the RAM 96 is transferred to the computer through the communication section 97 and subjected therein to a required process to be displayed on a screen, not shown. At this time, a required image is reconstructed using the image data obtained by detecting the X-rays transmitted through both side regions including the central rotation axis 29.

[0051] When the offset scan / CT mode has been selected, the CPU 94 drives the beam formation plate moving motor 55 to expose the beam formation transmission aperture 56 for CT in accordance with the selected CT mode opposite the X-ray tube 41. At this time, if necessary, the block 47 is moved in a rotational direction relative to the beam formation plate 50 in the X-ray generation section 15, and meanwhile, the detector holder 65 is moved in the rotational direction in the X-ray detection section 16.Further, the CPU 94 reads a program (not shown) in accordance with the selected offset scanning / CT mode from the ROM 95, and, if necessary, drives one or more of the Y-direction moving motor 23Y, the X-direction moving motor 23X, and the rotary motor 34 simultaneously or sequentially based on the read program to move the rotary arm 4 to the initial imaging position (step #10).

[0052] Next, when a command to start imaging is input by operating the imaging start switch 90 (step 11), the CPU 94 activates the X-ray tube 41 to generate X-rays and also drives a necessary motor in accordance with the preceding program (step 12). At this time, the rotation speed of each motor is detected by the corresponding sensors 81 to 88, and based on this detection result, the rotation speed of each motor is controlled. The X-rays emitted from the X-ray tube 41 are applied to the imaging subject through the X-ray transmission port 48 of the block 47 and the CT beam forming transmission port 56 of the beam forming plate 50.The X-rays transmitted through the imaging subject are detected by the X-ray detector 64 through the CT beam formation slit of the X-ray detector 64 in the X-ray detection section 16. The X-ray detection section 16 stores data corresponding to the acquired X-ray image in the RAM 96 at regular time intervals. The image data stored in the RAM 96 is transferred to the computer through the communication section 97 and subjected therein to a required process to be displayed on a screen (not shown). At this time, a required image is reconstructed using the image data obtained by detecting the X-rays transmitted through one or both side portions engaging the central rotation axis 29.

[0053] An initial setting process in the case where the offset scanning / CT mode has been selected will be described with reference to Fig. 15. It is assumed here that, in the state before the initial adjustment process, the central rotation axis 29 of the X-ray CT apparatus 1 is located at a center 100 of an imaging area 101 (area surrounded by an outer circle outside of double circles) of the imaging object positioned by the imaging object positioning mechanism.As shown in the figure, in this state, the imaging area 101 of the imaging subject is not completely included in an X-ray area (area surrounded by outer edges 102 and 103 indicated by double-dotted lines) 104 detected in the X-ray detecting section 16 by X-rays radiated from the X-ray generating section 15, and only an area of ​​interest (area surrounded by an inner circle outside the double circles) 105 within the imaging area 101 of the imaging subject can be imaged.

[0054] From this status where the position of the imaging subject is in a fixed state, the CPU 94 drives the X-direction moving motor 23X of the XY moving mechanism 18 to move the rotary arm 4 in the X-direction (rightward direction, direction of the arrow in the shown example) by a fixed distance from the position of Fig. 16A, while the central axis of rotation 29 is at the center of the imaging area 101 of the imaging object from the position of Fig. 16A (see Fig. 16B). Accordingly, while the central rotation axis 29 is held at the center of the imaging area 101 of the imaging object, the CPU 94 moves the rotary arm 4 in the Y direction (upward direction, direction of the arrow in the example shown) to bring the X-ray detecting section 16 closer to the imaging area 101 of the imaging object, so as to position the outer edge 102 or 103 of the beam cone 104 at the center of the imaging area 101 (see Fig. 16C). At this time, the outer edge 102 or 103 of the beam cone 104 is not necessarily located at the center of the imaging area 101 of the imaging subject, but at least the center of the imaging area 101 must be located within the beam cone 104. As shown in the figure, in this state, half of the imaging area 101 of the imaging subject is completely covered by the beam cone 104.

[0055] Afterwards, as in Fig. As shown in Figure 17, the CPU 94 drives the rotary motor 34 to rotate the rotary arm 4 in a clockwise direction, as indicated by the arrows. As a result, although the beam cone 104 covers only half of the imaging area 101 of the imaging subject at any one time during imaging, when the rotary arm 4 rotates completely (360°), the imaging area 101 of the imaging subject is completely scanned by the beam cone 104. This can result in subsequent reconstruction of the X-ray imaging data acquired in the X-ray acquisition section 16, thereby enabling reconstruction of a desired image of the entire imaging area 101 of the imaging subject. Such imaging is called offset scanning / CT, which can be performed in a wider area than the normal scanning / CT.

[0056] The initial setting process in a case where the extended (narrow) mode has been selected is described with reference to Fig. 18. Similar to what was described above, it is assumed that in the state before the initial adjustment process, the central rotation axis 29 of the X-ray CT apparatus 1 is located at the center of the imaging area 101 (area surrounded by an outer circle outside the double circles) of the imaging object positioned by the imaging object positioning mechanism 8.As shown in the figure, in this state, the imaging area 101 of the imaging subject is not completely enclosed in the X-ray irradiation area (area surrounded by the outer edges 102 and 103 indicated by the double-dotted lines) 104 detected in the X-ray detecting section 16 outside the X-rays radiated from the X-ray generating section 15, and only the area of ​​interest (area surrounded by an inner circle outside the double circles) 105 within the imaging area 101 of the imaging subject can be imaged.

[0057] From this state, the CPU 94 drives the X-direction moving motor 23X of the XY moving mechanism 18 to move the rotary arm 4 in the X-direction (rightward direction, arrow direction in the example shown) by a predetermined distance while locating the central rotary axis 29 at the center of the imaging area 101. Then, while keeping the central rotary axis 100 at the center of the imaging area 101 of the imaging subject, the CPU 94 moves the rotary arm 4 in the Y-direction (downward direction, arrow direction in the example shown) to bring the imaging area 101 of the imaging subject closer to the X-ray generating section 15, thereby positioning the outer edge 102 or 103 of the beam cone 104 at the center of the imaging area 101.At this time, the outer edge 102 or 103 of the beam cone 104 is not necessarily at the center of the imaging area 101 of the imaging subject, but at least the center of the imaging area 101 should be located within the beam cone 104. As shown in the figure, in this state, half of the imaging area 101 of the imaging subject is completely enclosed within the beam cone 104.

[0058] Then, as in Fig. As shown in Figure 19, the CPU 94 drives the rotary motor 34 to rotate the rotary arm 4 in a clockwise direction, as indicated by the arrows. As a result, although the beam cone 104 covers only half of the imaging area 101 of the imaging subject at any one time during imaging, when the rotary arm 4 rotates 360°, the imaging area 101 of the imaging subject is completely scanned by the beam cone 104. This can result in subsequent reconstruction of the X-ray imaging data acquired in the X-ray acquisition section 16, thereby enabling the reconstruction of a desired image of the entire imaging area 101 of the imaging subject.

[0059] By performing the imaging in such a way, a projected image can be expanded and imaged since the distance between the X-ray source and the imaging object is shorter than in the case of Fig. 16.

[0060] In this preferred embodiment, an imaging region in the normal scan / CT mode is defined as a region of interest as an example.

[0061] The imaging area in normal scan / CT mode is an area similar to the area of ​​circle 105 in Fig. 16A or Fig. 18A. And an imaging area in the offset scan / CT mode is, for example, an area that includes the imaging area in the normal scan / CT mode and the area around the imaging area in the normal scan / CT mode similar to the area of ​​the circle 101 in Fig. 16A or Fig. 18A includes.

[0062] Therefore, the maximum area of ​​the imaging field in offset scan / CT mode is defined by the outer edges 102 or 103 of the beam cone 104.

[0063] In Fig. 16A to C, Fig. For example, in Figs. 18A to C, the imaging area 101 is shown which is smaller than the above-mentioned maximum area of ​​the imaging area in consideration of the ease of understanding.

[0064] It should be noted that although the rotary arm 4 was first moved in the X direction and then in the Y direction in the above description, this order may be reversed, or the rotary arm 4 may be moved at once in an oblique direction obtained by superimposing these movements in the two directions.

[0065] The X-direction movement mechanism provided in the rotary arm 4 is particularly effective in the X-ray imaging apparatus using the offset scanning / CT mode as described above. For example, the beam cone must be moved in the direction orthogonal to the X-ray application direction in the offset scanning / CT method, but the amount of movement thereof can be adjusted within a wider range. Furthermore, the magnification ratio of an image formed in the limited-size X-ray acquisition section can be adjusted to a larger scale compared to a configuration where the rotary arm is simply moved in the Y-direction.

[0066] Additionally, the beam cone refers to an X-ray beam that narrows X-rays to apply X-rays within a specific area. In the above examples, the beam forming transmission aperture for CT was in a nearly square shape, and the pyramid-shaped beam cone was applied from the X-ray generation section toward the X-ray detection section. However, the shape of the beam forming transmission aperture for CT is not limited to this; a conical beam cone can be formed when the beam forming transmission aperture is circular or oval.

Claims

[1] X-ray CT device (1), which has: a lifting arm (3) which is provided so as to be liftable along a vertical column (2), and a rotating arm (4) for rotating about a central axis of rotation (29), which is coupled to the lifting arm (3) and supports an X-ray generating section (15) for generating and emitting X-rays and an X-ray detecting section (16) for detecting the X-rays emitted by the X-ray generating section (15), wherein the X-ray generating section (15) and the X-ray detecting section (16) are arranged on opposite sides of the central axis of rotation (29) such that the X-rays from the X-ray generating section (15) are detected by the X-ray detecting section (16), wherein the rotating arm (4) is designed to rotate the X-ray generating section (15) and the X-ray detecting section (16) while an imaging object is arranged between the X-ray generating section (15) and the X-ray detecting section (16) such that the X-ray detecting section (16) detects the X-rays emitted by the X-ray generating section (15) and transmitted through the imaging object to obtain imaging data for creating a CT image or a panoramic image, the device comprising: (A) an imaging mode selection device (91, 92) which is designed (a) a panoramic imaging mode in which, during imaging, the X-ray generating section (15) and the X-ray detecting section (16) are rotatably driven while the rotary arm (4) is rotated about the central rotary axis (29) to form the panoramic image of the imaging subject; (b) an offset scan / CT mode in which the CT image of the imaging subject is constructed on the basis of X-ray CT data obtained by rotating the rotary arm (4) about the central rotation axis (29), the rotary arm (4) being set in a position such that a part of a region of interest of the imaging subject is irradiated with a beam cone (104) emitted from the X-ray generating section (15) and detected in the X-ray detecting section (16), and (c) a normal scanning / CT mode in which the CT image of the imaging object is constructed on the basis of X-ray CT data obtained by rotating the rotary arm (4) about the central rotation axis (29), the rotary arm (4) being set in a position such that an entire region of interest of the imaging object is irradiated with a beam cone (104) emitted by the X-ray generating section (15) and detected in the X-ray detecting section (16), to select, and (B) an XY movement mechanism (18) and a rotary motor (34) which are designed (d) to move the rotating arm (4) horizontally relative to the lifting arm (3), (e) during the panoramic imaging mode, to move the rotary arm (4), the X-ray generating section (15) and the X-ray detecting section (16) along a locus for a panoramic image, (f) during the offset scan / CT mode, to move the rotary arm (4) so ​​that the beam cone (104) emitted from the X-ray generation section (15) toward the X-ray detection section (16) irradiates the part of the region of interest (105) of the object to be imaged, and (g) during the normal scanning / CT mode, to move the rotary arm (4) so ​​that the beam cone (104) emitted from the X-ray generation section (15) towards the X-ray detection section (16) irradiates the entire region of interest (105) of the object to be imaged; wherein the XY movement mechanism (18) is designed to move the rotary arm (4) during the offset scanning / CT mode such that the central axis of rotation (29) is positioned at a center of an imaging region (101) of the imaging object containing the region of interest (105), that the rotary arm (4) has a fixed distance from the center of the imaging region (101) along a first direction, that the center of the imaging region (101) is arranged within the beam cone (104), and that the X-ray detection section (16) is brought closer to the region of interest (105) than during the normal scanning / CT mode by moving the rotary arm (4) along a second direction perpendicular to the first direction, which points from the X-ray generation section to the X-ray detection section, or the XY movement mechanism (18) is designed to move the rotary arm (4) during the offset scan / CT mode such that the central rotation axis (29) is positioned at the center of the imaging area (101), that the rotary arm (4) has a fixed distance from the center of the imaging area (101) along the first direction, that the center of the imaging area (101) is arranged within the beam cone, and that the X-ray generation section (15) is brought closer to the region of interest (105) than during the normal scan / CT mode by moving the rotary arm (4) along a second direction perpendicular to the first direction, which points from the X-ray generation section to the X-ray acquisition section. [2] The X-ray CT apparatus (1) according to claim 1, wherein the X-ray generating section (15) comprises: a first slit (56) configured to form an X-ray beam radiated from the X-ray generating section (15) into a narrow stripe shape to form a narrow beam toward the imaging subject in accordance with the panoramic imaging mode; a second slit (57) configured to form an X-ray beam radiated from the X-ray generating section (15) toward the imaging object into the beam cone (104) in accordance with the offset scanning / CT mode and / or the normal scanning / CT mode; and a slit moving device (51, 52, 53) configured to selectively arrange the first slit (56) and the second slit (57) in the X-ray generating section (15). [3] The X-ray CT apparatus (1) according to claim 2, comprising means for moving the first slit (56) or the second slit (57) arranged in the X-ray generating section (15) to a direction orthogonal to the X-ray beam in accordance with a signal from the imaging mode selecting means (91, 92). [4] The X-ray CT apparatus (1) according to any one of claims 1 to 3, comprising drive means for moving the central rotation axis (29) of the rotary arm (4) relative to the rotary arm (4) to adjust the position such that a part or the whole of the region of interest (105) of the imaging subject is irradiated with the beam cone (104) in accordance with at least one of the offset scan / CT mode and / or the normal scan / CT mode.

Images