JP2015177964A - X-ray imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus which can improve the degree of freedom of setting in a focal surface in an imaging space, that is, setting in a locus of an X-ray path.SOLUTION: In a panoramic imaging apparatus 1, an X-ray tube arm includes a tube housing part housing an X-ray tube 23 and a tube supporting part supporting the tube housing part rotatably around a first axis in parallel to a center axis CA, the tube housing part is rotated around the first axis with respect to the tube supporting part, a detector arm includes a detector housing part housing a detector 24 and a detector supporting part supporting the detector housing part rotatably around a second axis in parallel to the center axis, the detector housing part is rotated around the second axis with respect to the detector supporting part, the X-ray tube arm and the detector arm are coaxially rotated independently of each other, and first, second and third pieces of drive means are controlled in accordance with the speed patterns for rotating independently of each other at the time of scan.

Description

  The present invention relates to an X-ray imaging apparatus using X-rays, and in particular, faces an X-ray tube and a detector that detects X-rays irradiated from the X-ray tube and transmitted through an imaging region of a subject. And an X-ray imaging apparatus having a structure for rotating the X-ray tube and the detector around a subject.

  In recent years, tomography of a subject based on the tomosynthesis method has been actively performed. Although the principle of this tomosynthesis method has been known for a long time (see, for example, Patent Document 1), in recent years, a tomographic method has also been proposed in which it is desired to enjoy the simplicity of image reconstruction based on the tomosynthesis method. (For example, see Patent Document 2 and Patent Document 3). In addition, many examples are seen for dental use (see, for example, Patent Document 4 and Patent Document 5).

  As one application of the tomosynthesis method to dentistry, a panoramic imaging apparatus that obtains a panoramic image in which a curved dentition is developed in a two-dimensional plane has been put into practical use. This panoramic imaging apparatus normally has a pair of an X-ray tube and a detector having vertically long two-dimensionally arranged pixels around the oral cavity of a subject along a dentition whose rotation center is assumed. A mechanism for rotating the center of rotation in a complicated manner so as to draw a trajectory is provided. A constant value is maintained between the X-ray tube and the detector. The above-described constant trajectory is a trajectory for focusing on a reference tomographic plane (a tomographic plane existing three-dimensionally) set in advance along a dentition regarded as a standard shape and size. During this rotation, X-rays emitted from the X-ray tube are transmitted through the subject at regular intervals, and detected as digital frame data by the detector. For this reason, frame data focused on the reference tomographic plane is collected at regular intervals. This frame data is reconstructed by the tomosynthesis method to obtain a panoramic image of the reference tomographic plane.

  Further, Patent Document 6 discloses an example of a panoramic imaging apparatus having an imaging system in which an X-ray tube and a detector can both rotate independently of each other so as to form a circular orbit around the same center point. . The jaw is positioned in the circular orbit. The speed pattern is controlled so that the X-rays emitted from the X-ray tube are always directed to the detection surface of the detector.

JP-A-57-203430 JP-A-6-88790 JP-A-10-295680 US Patent Publication US2006 / 0203959 A1 JP2007-136163A International Publication WO2012 / 008492

  However, in the case of the apparatus described in Patent Document 6 described above, the X-ray tube and the detector are scanned so as to always face each other at a position passing through the same rotation center, so that the tomographic focus is focused on the imaging space (object space). There were still restrictions on the plane (focal plane) setting. In other words, since the dentition of the subject varies from person to person, a higher degree of freedom is desired for setting the focal plane, but such a request has not been met.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an X-ray imaging apparatus capable of increasing the degree of freedom in setting a focal plane in an imaging space, that is, setting an X-ray path trajectory. And

  In order to achieve the above object, an X-ray imaging apparatus according to the present invention has a point-like focal point, an X-ray tube that irradiates X-rays having a spread from the focal point, and the X-ray tube. A detector that detects the X-ray and outputs data corresponding to the amount of the X-ray, and rotates the X-ray tube and the detector around a predetermined center axis passing through a predetermined rotation center. It is configured to be movable. The apparatus is configured such that the X-ray tube receives the X-ray so that the X-ray tube is accommodated, and the tube accommodating portion is rotatable around a first axis parallel to the central axis. An X-ray tube arm having a tube support portion to support, a first driving means for rotating the tube housing portion around the first axis with respect to the tube support portion, and the X-ray incident thereon A detector including a detector accommodating portion that accommodates the detector and a detector supporting portion that rotatably supports the detector accommodating portion around a second axis parallel to the central axis. An arm, second driving means for rotating the detector accommodating portion around the second axis with respect to the detector support portion, and the X-ray tube arm and the detector arm independently of each other. Third driving means that supports the same axis so as to be drivable and drives both arms to rotate around the central axis. The first and second in accordance with a speed pattern in which the X-ray tube arm, the detector arm, the tube housing portion, and the detector housing portion are rotated independently of each other for scanning by the X-ray. And control means for controlling the third driving means.

  According to the X-ray imaging apparatus of the present invention, the X-ray tube and the detector are rotated independently of each other around the same central axis passing through one rotation center. In addition, the X-ray tube and the detector can be rotated around first and second axes parallel to the rotational axis at their respective rotational positions. That is, since both the X-ray tube and the detector can rotate (attitude control), the two can always be kept facing each other. As a result, while the X-ray tube and the detector rotate on their respective circular orbits, the configuration is relatively simple and can be miniaturized. The X-ray path can be easily changed, so that the imaging space can be drawn from various angles. For this reason, various focal planes can be set in the imaging space.

In the accompanying drawings,
FIG. 1 is a perspective view showing a front side of an X-ray panoramic imaging apparatus as an X-ray imaging apparatus according to an embodiment. FIG. 2 is a perspective view showing the back of an X-ray panoramic imaging apparatus as an X-ray imaging apparatus according to an embodiment. FIG. 3 is a perspective view for explaining the positional relationship between the X-ray panoramic imaging apparatus and the dental treatment chair and the position of the subject at the time of imaging. FIG. 4 is a partial cross-sectional view illustrating a scattered radiation shielding plate built in the bottom surface. FIG. 5 is a perspective view for explaining the scattered radiation shielding cover. FIG. 6 is a diagram illustrating a four-surface shielding structure including a scattered radiation shielding cover that covers the upper surface and both side surfaces and a scattered radiation shielding plate that covers the bottom surface portion. FIG. 7 is a side view for explaining the 4-axis independent drive of the X-ray panoramic imaging apparatus. FIG. 8 is a front view for explaining the 4-axis independent drive of the X-ray panoramic imaging apparatus. FIG. 9 is a block diagram showing a part of the electrical configuration of the X-ray panoramic imaging apparatus. FIG. 10 is a diagram illustrating the relationship between a standard dentition, a 3D reference tomographic plane, and an X-ray path. FIG. 11 is a graph illustrating a speed pattern instructing partial revolutions of the X-ray tube and the detector related to two axes in the four-axis independent control. FIG. 12 is a graph illustrating a speed pattern instructing partial rotation of the X-ray tube and the detector relating to the remaining two axes of the four-axis independent control. FIG. 13 is a flowchart illustrating a procedure for panoramic shooting. FIG. 14 is a diagram for explaining a typical rotational position of the X-ray tube and the detector during panoramic imaging and a state of positioning by a laser beam. FIG. 15 is a perspective view of the internal structure of the apparatus main body mounted on the panoramic photographing apparatus according to the first modification as seen from the front. FIG. 15 is a perspective view of the internal structure of the apparatus main body according to the first modification when viewed from the rear. FIG. 17 is a perspective view illustrating a scattered radiation shielding cover according to the second modification.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 14, an embodiment of an X-ray panoramic imaging apparatus as an X-ray imaging apparatus according to the present invention will be described.

  The panoramic imaging apparatus 1 is configured as a dental diagnostic apparatus that captures a panoramic image of a subject's jaw (including a dentition).

  According to this panoramic imaging apparatus 1, a pseudo three-dimensional tomographic image of the subject's jaw (the image itself is a two-dimensional image, but three-dimensionally according to the shape of an imaging region such as a dentition). The displayed cross-sectional image) can be taken. Moreover, according to this apparatus 1, the precision imaging | photography which image | photographs the partial area | region of the dentition of a jaw part more precisely can also be performed.

  In the case of this panoramic photographing apparatus 1, the control of the rotational operation for precision photographing is based on an original control method called “4-axis independent control”. The “4-axis independent control” adopts a unique scattered radiation shielding structure because the apparatus is portable and can be used on the side of the dental treatment chair 2. For this reason, the overall configuration of the apparatus including the scattered radiation shielding structure will be described first, followed by the configuration of the 4-axis independent control.

  In this embodiment, the X-ray imaging apparatus according to the present invention is configured as a panoramic imaging apparatus, but the X-ray imaging apparatus is not necessarily limited to the dental field. This X-ray imaging apparatus may be configured to image various other parts such as otolaryngology imaging and bone / joint parts of limbs. Furthermore, this X-ray imaging apparatus may be implemented as an X-ray CT apparatus.

  FIG. 1 and FIG. 2 show the external appearance of the dental X-ray panoramic imaging apparatus 1 according to this embodiment from the front side and from the back side. FIG. 3 shows a state in which the panoramic photographing apparatus 1 is used while being positioned on the side of the dental treatment chair 2.

As can be seen from FIGS. 1 and 2, the panoramic photographing apparatus 1 includes a pedestal portion 12 on which four casters 11 (moving means) are mounted, a power supply box 13 mounted on the pedestal portion 12, and a pedestal portion 12. And a console 15 equipped with a computer for controlling and image processing. The console 15 is connected to the main body BD of the apparatus 1 via a cable or via wireless communication. Here, the main body BD means an apparatus portion excluding the console 15 and a floor fixing portion 53 (see FIG. 3) described later.
[Overview of overall system configuration]
First, an outline of the overall mechanical configuration of the panorama photographing apparatus 1 will be described.

  The casters 11 are provided at the four corners of the lower surface of the base 12. For this reason, the dentist or the operator can move by pushing the panoramic imaging apparatus 1 and can freely move from room to room or between the room place and the side of the dental treatment chair 2. . The caster 11 can be locked and unlocked by depressing or raising a pedal 11P (see FIG. 2).

  The elevator 14 includes an elevator mechanism (not shown) in its interior, and is electrically driven with respect to the pedestal 12 (that is, the floor surface, that is, the dental treatment chair 2) within a predetermined height range (for example, 10 to 15 cm). It is configured to be movable up and down at a height position. The power supply box 13 includes a power supply circuit that supplies necessary power to each part of the system. The elevator 14 provides an imaging space S having a substantially rectangular parallelepiped shape for performing X-ray scanning with the head H of the patient P positioned as shown in FIG.

  Assuming that the vertical movement direction of the elevator 14 is the Y axis, XYZ orthogonal coordinates as shown can be set. Since the head H of the patient P is positioned in the imaging space (object space) S as shown in FIG. 3 at the time of X-ray imaging, the direction of the Z axis is the direction from the top of the head H toward the toes (median) Line direction). For this reason, the direction of the Z axis coincides with the body axis direction. Furthermore, since the direction of the Z axis is also the front-rear direction of the device 1, it can also be called the front-rear direction. In the present embodiment, the side where the head H of the subject P is put into the imaging space S of the panoramic imaging apparatus 1 is referred to as the front surface (front surface), and the opposite surface is referred to as the rear surface (back surface).

  The elevator 14 includes a bottom surface portion 14A positioned on the lower side thereof, and a back surface portion 14B positioned in contact with the bottom surface portion 14A on the back surface side of the bottom surface portion 14A in the X-axis direction. Further, the elevator 14 further includes a scattered radiation shielding cover (part of the shielding body) which overlaps and overlaps both sides of the bottom surface portion 14A, that is, both sides in the X-axis direction and can be manually slid in the front-rear direction. ) 14C. The scattered radiation shielding cover 14C is supported by rails RL provided on both lateral sides of the bottom surface portion 14A, and is slidably engaged in the front-rear direction. In order to perform this slide manually, a handle 16 is attached to the upper side and the rear side of the scattered radiation shielding cover 14C.

  Although described later, the scattered radiation shielding cover 14C functions as a first shielding body that shields scattered X-ray radiation.

  The bottom surface portion 14A is formed of a member formed by folding a rectangular resin or metal plate and joining both ends thereof to have a certain height and bend toward the outside in the height direction, that is, the Y-axis direction. The The inside of this bending member is hollow. The reason for this curvature is that the imaging space S is secured as wide as possible and the design is taken into consideration.

  As shown in FIG. 4, a scattered radiation shielding plate (second shielding body) 20 made of a lead plate is attached to the upper side of the cavity inside the bottom surface portion 14A. A part of the edge in the horizontal direction (X-axis direction) of the scattered radiation shielding plate 20 is folded along the folding of the bottom surface portion 14A in the height direction (Y-axis direction). The lead plate has a thickness of 0.3 mm and functions as a second shielding body that shields scattered X-ray rays.

  A mechanism portion including a drive system including a motor, a power transmission mechanism, and the like and an encoder (rotational position sensor) for monitoring the operation of the drive system is incorporated in the back surface portion 14B of the elevator 14. As this mechanism portion, two arms 21 and 22 coupled to two electric motors that can rotate independently of each other project from the back surface portion 14B into the imaging space S. These arms 21 and 22 have an L-shaped X-ray tube arm 21 with an X-ray tube 23 for irradiating fan-shaped X-rays built in at the tip side and a detector 24 for detecting X-rays at the tip side. L-shaped detector arm 22. The other ends of the arms 21 and 22 are coaxially linked around the rotation center O and can rotate independently of each other (see arrows T and D in FIG. 1). Are combined separately. The motor is, for example, a stepping motor, and its rotational position is detected by an encoder (not shown). Note that a virtual straight line passing through the rotation center O and parallel to the Z axis is referred to as a central axis CA. The central axis CA is an axis that can also be called the rotation center axis of the arm, and is physically different from the rotation center O of the arm, but is present at the same position when observing along the Z-axis direction. .

  Further, each of the X-ray tube arm 21 and the detector arm 22 supports only the tip side portion, that is, the portion containing the X-ray tube 23 and the detector 24 on the support side, that is, the back surface portion 14B. The support portion can be independently rotated within a predetermined angle range with respect to the support portion side. Arrows T1 and D1 in FIG. 1 indicate this rotation. That is, the X-ray tube 23 and the detector 24 have a total of four degrees of freedom of independent rotation with respect to the back surface portion 14B.

  The X-ray tube 23 incorporates a collimator (not shown). This collimator collimates the X-rays irradiated by the X-ray tube 23 according to the shape of the X-ray incident window WD of the detector 24. The X-ray incident window WD has an elongated two-dimensional opening. For this reason, the X-rays irradiated from the X-ray tube 23 are narrowed down to a fan beam XB having a rectangular cross section in accordance with the size of the X-ray incident window WD.

  As will be described later, the detector 24 has a structure in which a plurality of modules in which semiconductor elements that directly convert X-rays into electric signals are arranged in two-dimensional pixels are arranged in a plurality of columns.

  At the time of imaging, the head H of the subject P is located in the imaging space S as will be described later. At this time, the X-ray tube 23 and the detector 24 are positioned substantially opposite to each other across the jaw. When the apparatus is activated, the X-ray tube 23 and the detector 24 rotate independently of each other over the head H over an angle range of, for example, 220 ° (see the arrow in FIG. 3). X-rays are emitted from the tube 23 continuously or in pulses. For this reason, the X-ray XB irradiated from the X-ray tube 23 passes through the jaw of the head H and is detected by the detector 24. The electric signal output from the detector 24 is sent as frame data to the image processor of the console 15 at a constant rate. The image processor performs a shift-and-add process based on the tomosynthesis method on the frame data, and reconstructs a panoramic image along a cross section in which, for example, the dentition of the jaw is curved along the dentition surface.

  As shown in FIGS. 1 and 3, one rotation center O is set in the imaging space S when viewed from the Z-axis direction. At the position of the rotation center O, an L-shaped teaching arm 25 is provided coaxially with the rotation shafts of the arms 21 and 22 on the apparatus main body side. The teaching arm 25 is used for designating a range of a part (target tooth) of a dentition that the dentist wants to examine particularly precisely. In other words, it has a position designation function that is performed in so-called partial photographing or precision photographing, which is performed in the photographing by the conventional intraoral photographing method. A laser beam can be irradiated from the tip of the teaching arm 25. Therefore, the dentist visually confirms the position where the laser beam hits the dentition while holding the tip of the teaching arm 25 and manually rotating the arm around the jaw. Through this visual confirmation work, the angle position of the target tooth in the circumferential direction and the angle of the transmitted X-ray that passes through the target tooth when actually performing X-ray imaging can be verified in advance. The teaching arm 25 is provided with an encoder and a switch (not shown). For this reason, when the angle position and the angle of the transmitted X-ray are determined, the dentist can store the setting information by pressing the switch. This stored information is used by the control unit of the console 15 at the time of actual imaging, and the X-ray irradiation operation and the rotation operation of the X-ray tube 23 and the detector 24 are controlled according to the information.

  Of course, in the present embodiment, a configuration in which this partial photographing (precision photographing) is not performed may be employed. That is, in that case, the teaching arm 25, a mechanism for driving the teaching arm, and software for partial photographing are not required, so that the configuration can be simplified and the calculation amount can be reduced accordingly.

  On the other hand, as shown in FIG. 5, the scattered radiation shielding cover 14 </ b> C serves to define the upper surface and the left and right side surfaces of the imaging space S and to shield X-rays. For this reason, the scattered radiation shielding cover 14 </ b> C has a shape obtained by bending a plate having an X-ray shielding function with a constant width into a generally inverted U shape. In other words, the scattered radiation shielding cover 14C has a flat upper surface portion (ceiling body) 14U and both side surface portions (wall bodies) 14L and 14R that are curved and integrally formed from the upper surface portion 14U.

  Furthermore, although the scattered radiation shielding cover 14C has an X-ray shielding function as a whole, the scattered radiation shielding cover 14C is formed by combining two kinds of members related to light transmission. Specifically, the scattered radiation shielding cover 14C includes a translucent portion 14TR having translucency and a non-translucent portion having non-translucency integrally coupled to the translucent portion 14TR. 14NT. Both the translucent portion 14TR and the non-translucent portion 14NT partially cover the upper surface portion 14U and the side surface portions 14L and 14R.

  The non-translucent portion 14NT is formed in an inverted L shape when viewed from the side so as to cover the upper surface portion 14U and the side surface portions 14L and 14R and to bear a part of the rear surface side and extend to the bottom surface side. ing. This non-translucent portion 14NT is formed as a laminated body in which, for example, a lead plate having a thickness of 0.3 mm is sandwiched between resin or metal plates.

  On the other hand, the translucent portion 14TR is generally formed in an inverted U shape so as to cover the front side of the non-translucent portion 14NT across the upper surface portion 14U and the side surface portions 14L, 14R. In particular, since the height of the left and right sides of the light-transmitting portion 14TR is shorter than that of the non-light-transmitting portion 14NT, the bottom end portion of the light-transmitting portion 14TR is supported by the non-light-transmitting portion 14NT. It is like that.

  In the present embodiment, the light transmitting body portion 14TR is formed of a transparent acrylic resin having a thickness of 8.5 mm containing a lead component, and thereby has an X-ray shielding ability of a lead equivalent of 0.3 mmPb. Therefore, the translucent portion 14TR has an X-ray shielding function, but also has light transparency. Although the acrylic resin itself is transparent, it contains a lead component, so it actually has a yellowish color but is translucent. For this reason, as will be described later, when the head H of the patient P enters the imaging space S, the patient can see the outside of the cover. Of course, the operator can also visually observe the inside of the imaging space S.

  The end portion of the lead-containing acrylic resin forming the light transmitting portion 14TR is inserted into the end portion of the non-light transmitting portion 14NT. For this reason, this acrylic resin and the lead plate sandwiched by the non-translucent portion 14NT are connected to each other without a gap. Therefore, the X-ray shielding function on the upper surface and both sides of the imaging space S is ensured in both the translucent portion 14TR and the non-translucent portion 14NT, that is, the scattered radiation shielding cover 14C. In the present embodiment, an X-ray shielding device is configured by the scattered radiation shielding cover 14C and the scattered radiation shielding plate 20 on the bottom surface portion 14C.

  If the view of the scattered radiation shielding cover 14C is changed, it can be said that a part of the scattered radiation shielding cover 14TR, that is, the translucent part 14TR has a light transmitting property while having a function of shielding the scattered radiation as a whole.

  As a result, as shown in FIG. 6, the X-ray shielding function is given to the four surfaces of the upper surface, both side surfaces, and the bottom surface that define the imaging space S.

  As shown in FIGS. 1 and 3, a cover portion 51 containing a fixing pin 50 is provided at the front end of the pedestal portion 12. The pin 50 moves up and down in conjunction with an operation lever 52 (see FIG. 2) provided on the upper edge of the back surface part 14 via a wire mechanism (not shown). On the other hand, a floor fixing portion 53 having a substantially triangular shape in a side view and having a hole into which the pin 50 can be inserted is fixed at a predetermined position on the rear surface of the dental treatment chair 2. . For this reason, the pin 50 can be pushed down by moving the apparatus main body BD and operating the operation lever 52 in a state where the tip end position thereof is aligned with the floor fixing portion 53. When the pin 50 enters the hole of the floor fixing portion 53, the apparatus main body BD is positioned with respect to the dental treatment chair 2 (see FIG. 3).

  Further, when the apparatus main body BD is moved to another location, the pin 50 is pulled up and released from the floor fixing portion 53 by operating the operation lever 52. Thereby, apparatus main body BD can be moved to another place.

  In order to move the apparatus main body BD, a moving handle 54 is fixed to the upper end portion of the back surface portion 14B on both sides of the operation lever 52. Therefore, the operator can easily move the apparatus main body BD along with the free rotation of the caster 11 by holding the moving handle 54. The position and shape of the moving handle 54 are not limited to the position and structure tightened in FIG. 2, and if the operator can manually push or move the apparatus main body BD, the number and the shape are included. Can be freely deformed. For example, the moving handle 54 may be formed as an L-shaped handle that is fixed to both corners of the upper end portion of the back surface portion 14B and has a horizontal portion and a vertical portion integrally.

  The back surface portion 14B is provided with an irradiation switch 56 for commanding X-ray irradiation and rotation of the X-ray tube / detector via a cord 55 having a length of 2 m, for example. This irradiation switch 56 is configured as a deadman switch. That is, X-ray irradiation is performed only while the push button of the irradiation switch 56 is being pressed. The switch signal of the irradiation switch 56 is sent to the console 15.

  Based on the above configuration, a portable panoramic photographing apparatus 1 having a height of about 100 to 115 cm, a width of about 80 to 95 cm, and a depth of about 75 to 90 cm is provided. In addition, since the X-ray shielding function is given to the four surfaces of the upper surface, both side surfaces, and the bottom surface that define the imaging space S, the imaging space S is regarded as a substantial X-ray shielding room. You can also. Therefore, in this embodiment, the X-ray shielding chamber (that is, the device 1) can be easily carried to an arbitrary place by the caster 11 by grasping and pushing the moving handle 54 and can be used there. .

[Configuration and control of 4-axis independent drive of imaging system]
Here, with reference to FIGS. 7-12, the structure and control for the 4-axis independent drive of the imaging system provided with the X-ray tube 23 and the detector 24 are further demonstrated.

  As described above, the panoramic imaging apparatus 1 includes the X-ray tube arm 21 and the detector arm 22 that extend in the lateral direction from the elevator section of the elevator 14. As shown in FIG. 7, the two arms 21 and 22 are both formed in an approximately L shape, and the ends of the support portions (tube support portions and detector support portions) 21L and 22L of the arms 21 and 22 respectively. The parts are superposed so as to overlap each other and are attached to the elevator 14. A rotary drive mechanism 83 that can rotate these two arms 21 and 22 independently of each other, that is, at different speeds, is provided inside the elevator 14. The above-described X-ray tube 23 and detector 24 are mounted on the opposing arm portions 21A and 22A on the distal ends of the two arms 21 and 22, respectively. On the front surface of the X-ray tube 23 on the X-ray irradiation side, a slit (aperture) 84 for forming X-rays into a fan shape is disposed. The opening area of the slit 84 is variable, and the size of the opening area is controlled by an opening driving unit 85 such as a motor described later. The rotation drive mechanism 83 and the arms 21 and 22 constitute support means for supporting the X-ray tube 23 and the detector 24 so that they can be driven independently of each other.

  The X-ray tube 23 is configured as a rotary anode type X-ray tube used for an appropriate anode material such as tungsten. The X-ray tube 23 has a point-like tube focus (X-ray focus) (for example, a diameter of 0.1 mm to 0.5 mm: 0.15 mm in this embodiment) FP. The X-ray tube 23 irradiates X-rays in response to driving power supplied from a high voltage generator described later. The X-rays irradiated from the X-ray tube 23 are narrowed by the slit 84 and formed into a fan-shaped X-ray beam. The X-ray beam then passes through the jaw JW of the subject P and attenuates, and transmitted X-rays reflecting the attenuated state enter the detector 24.

  At the time of imaging, as shown in FIG. 8, the jaw portion JW of the subject P is positioned at a predetermined position in the three-dimensional imaging space S defined between the X-ray tube 23 and the detector 24. For this reason, the X-ray tube 23 and the detector 24 face each other (face to face) with the jaw portion interposed therebetween. The irradiated X-ray beam passes through the slit 84 and then passes through the jaw portion JW (dentition etc.) and is detected by the detector 24. At the time of shooting, the two arms 21 and 22 are independently rotated by the rotation drive mechanism 83.

  When viewed from the Z-axis direction, that is, the front-rear direction, the X-ray tube 23 and the detector 24 have a circular trajectory Tx centered on a central axis CA (rotation center O) determined in advance on the system side, as shown in FIG. , Td, respectively. The radii Dx and Dd from the central axis CA to the circular trajectories Tx and Td are set to different values in consideration of X-ray exposure, detection accuracy, downsizing of the apparatus, mechanical interference with the patient, and the like. Yes. In the present embodiment, Dx ≠ Dd, and particularly Dx> Dd. The reason why the distance (radius Dd) from the central axis CA to the detector 24 is smaller than that (radius Dx) from the central axis CA to the X-ray tube 23 is that the position of the detector 24 is as much as possible and the jaw JW This is to reduce the attenuation of the incident intensity of X-rays. The distance (radius Dx) from the central axis CA to the X-ray tube 23 is set to a value that can ensure the distance between the X-ray tube and the skin defined by the standard. As a result, the X-ray tube 23 and the detector 24 rotate around the jaw portion along predetermined circular trajectories Tx and Td around the central axis CA. During the rotation, irradiation and detection of the X-ray beam are executed at predetermined intervals.

  Therefore, the X-ray tube 23 and the detector 24 are always opposed to each other (facing each other), and X-ray irradiation and detection along a plurality of predetermined desired X-ray paths with respect to the jaw JW (dentition) are performed. In order to perform the above, the X-ray tube 23 and the detector 24 are driven independently of each other at different angular velocities.

  Note that “opposing each other” described above is irradiated from the dotted tube focal point (focal position) FP of the X-ray tube 23 when viewed along the Z-axis direction, as shown in FIG. This refers to a state in which the irradiation range of the X-ray beam formed in a cone shape matches the X-ray detection surface 24A of the detector 24. In particular, the center line T in the direction along the XY plane of the X-ray beam intersects the detection center position C in the width direction of the X-ray detection surface (the width in the direction along the XY plane) at 90 °. This is referred to as a “facing state” (see FIG. 8). In FIG. 8, a linear position extending in the X-axis direction from the mechanical rotation center O is defined as a rotation angle θ = 0, and ± rotation directions are set clockwise and counterclockwise from this rotation position.

  For this reason, in order to realize the above-mentioned “always facing each other (or facing each other)”, of the arms 21 and 22, the facing arm portion (tube housing portion, detection) housing the X-ray tube 23 and the detector 24. The container housing portions 21A and 22A are independent of each other about the first axis (that is, the X-ray tube swing rotation center axis) AXs and the second axis (that is, the detector swing rotation center axis) AXd. Thus, rotation (spinning, that is, posture) is possible (see FIGS. 7 and 8). For this purpose, rotary drive mechanisms 21B and 22B such as motors are provided on the arms 21 and 22, respectively (see FIG. 7). The drive control of the rotation drive mechanisms 21B and 22B is executed by a controller provided in the power supply box 13 in accordance with a command from the console 15 described later.

  In this embodiment, the circular trajectories Tx and Td shown in FIG. 8 indicate the trajectories of the first and second axes AXs and AXd described above when viewed on the XY plane, respectively. In the present embodiment, biaxial rotational degrees of freedom are given to the arms 2 and 22 that are driven to rotate independently from each other by the rotary drive mechanism 83 described above, so that the X-ray tube 23 rotates (so-called swinging rotation) and is detected. Two-axis rotational freedom is given to the rotation (so-called swinging rotation) of the device 24. This gives a total of four axes of rotational freedom.

  The detector 24 has a plurality of detection modules in which X-ray imaging elements are two-dimensionally arranged. The plurality of detection modules are formed as blocks independent from each other, and are mounted on the substrate in a predetermined rectangular shape to form the entire detector 24.

  The structure of the detector 24 and the processing of the detection signal by the sub-pixel method are known, for example, from International Publication WO 2012 / 0886648A1.

  Each detection module is made of a semiconductor material that converts X-rays directly into electrical pulse signals. For this reason, the detector 24 is a photon counting X-ray detector of a direct conversion method using a semiconductor.

The number of pixels each detection module is 40 × 40 pixels, for example, the size of each pixel _{S n} is 200 [mu] m × 200 [mu] m, for example. This pixel size is set to a value that allows detection of incident X-rays as a collection of many photons. Each pixel responds to the incidence of each photon of the X-ray and outputs an electric pulse having an amplitude corresponding to the energy of each photon. That is, each pixel can directly convert X-rays incident on the pixel into an electrical signal.

  For this reason, the detector 24 counts the incident X-ray photons for each pixel constituting the detection surface of the detector 24, and outputs the electric quantity data reflecting the counted value, for example, a high frame of 300 fps. Output at the rate. This data is also called frame data.

As the semiconductor material of the semiconductor layer, that is, the semiconductor cell, cadmium telluride semiconductor (CdTe semiconductor), cadmium zinc telluride semiconductor (CdZnTe semiconductor (CZT semiconductor)), silicon semiconductor (Si semiconductor), thallium bromide (T1Br), Mercury iodide (HgI ₂ ) or the like is used. Note that a detector having a combination structure of a photodiode and a scintillator may be used instead of the detector using the semiconductor cell.

  On the other hand, in this panoramic photographing apparatus 1, the four laser beams are used as positioning means. Specifically, a midline laser 211 provided on the upper side of the imaging space S side of the back surface portion 14B, a horizontal laser 212 provided at each predetermined position on the side surface of the opposing arm portion 22B of the detector arm 22, and an occlusal plane laser 213 and the canine laser 214 (see FIG. 7). These lasers 211 to 214 project linear laser markers onto the head of the subject P during positioning, and their drive is controlled via the console 15. The median laser 211 aligns the midline of the head H of the subject P, the horizontal laser 212 aligns the Frankfurt plane, the occlusal plane laser 213 aligns the occlusal plane, and the canine laser 214 aligns the canines in the dentition. (See FIG. 14, (B ′)).

  Further, shock sensors 215 and 216 for detecting an impact are installed on the opposing arm portions 21B and 22B of the X-ray tube arm 21 and the detector arm 22 as fail-safe sensors (see FIG. 7). In this case, for example, when something hits the arms 21 and 22, the detection is made to stop the scanning, and the output signals of the shock sensors 215 and 216 are also sent to the console 15.

  As shown in FIG. 9, the console 15 includes an interface (I / F) 131 that performs input and output of signals, a controller 133 that is communicably connected to the interface 131 via a bus 132, and a first storage unit 134, a data processor (CPU) 135, a display device 136, an input device 137, a calibration calculator 138, a second storage unit 139, first to fourth ROMs 140A to 140D, and a threshold value assigner 140E.

  The controller 133 controls the driving of the panorama photographing apparatus 1 in accordance with a program given in advance to the first ROM 140A. For this control, a command value is sent to the high voltage generator 140F that supplies a high voltage to the X-ray tube 23, a command value is sent to the opening drive unit 85 to change the opening area of the slit 84, and calibration is performed. A drive command to the operation calculator 138 is also included. The first storage unit 134 stores frame data and image data that are count values sent from the detector 24 via the interface 131. Further, the controller 133 receives the switch signal of the irradiation switch 56 via the interface 131, and controls scanning as will be described later. Similarly, the controller 133 also receives the signals of the shock sensors 215 and 216 via the interface 131, and controls the continuation / stop of the scan described later. Further, the controller 133 is connected to the positioning lasers 151 to 154 via the interface 131, and is configured to drive the lasers 151 to 154 when a positioning command is issued.

  The data processor 135 operates based on a program given in advance to the second ROM 140B under the control of the controller 133. Further, during panoramic shooting, the data processor 135 operates to tomosynthesis the frame data stored in the first storage unit 134 based on a known arithmetic method called shift and add. Implement the law. Thereby, the panoramic image of the tomographic plane with the oral cavity of the subject P is obtained. The display device 136 is responsible for displaying images to be created, information indicating the operation status of the apparatus, and operator operation information provided via the input device 137. The input device 137 is used by an operator to give information necessary for imaging to the apparatus.

  In addition, the calibration calculator 138 operates under the control of the controller 133 under a program built in the third ROM 140C in advance, and is given to each energy discrimination circuit for each pixel in the data counting circuit. Calibrate digital quantity thresholds for energy discrimination.

  Under the control of the controller 133, the threshold value assigner 140E calls the digital amount threshold value stored in the second storage unit 139 for each pixel and for each discrimination circuit at the time of imaging, and uses the threshold value as a command value as an interface. The signal is transmitted to the photon counting circuit of the detector 24 via 131. In order to execute this process, the threshold value assigner 140E executes a program stored in advance in the fourth ROM 140D.

  The controller 133, the data processor 135, the calibration calculator 138, and the threshold value assigner 140E all include a CPU (central processing unit) that operates according to a given program. These programs are stored in advance in each of the first to fourth ROMs 140A to 140D.

  In this embodiment, as known from International Publication No. WO2011 / 142343 (International Application No. PCT / JP2011 / 060731), the structure of the imaging space S is analyzed using a phantom, and the collection channel of the detector 24 is calibrated. Is done. This calibration is executed at an appropriate timing such as before imaging or during maintenance inspection.

  FIG. 10 shows a standard dentition TR, a trajectory SS (referred to as a standard trajectory) of projection of the horseshoe-shaped 3D reference tomographic plane of the dentition TR onto the XY plane, the position of the cervical vertebra CS, and the subject P An X-ray beam path XB at each rotation angle θ in the circumferential direction CR of the jaw JW is illustrated. The path XB indicates a path connecting the X-ray focal point FP of the X-ray tube 23 and the center position C in the horizontal width direction (Y-axis direction) of the detection surface 24A (see FIG. 8) of the detector 24.

  As can be seen from FIGS. 7 and 8, the tube focal point FP of the X-ray tube 23 is located on the line of the first axis (that is, the central axis of swinging of the X-ray tube) AXs, and the detection surface of the detector 24 is detected. The center position C in the lateral width direction of 24A is located on the line of the second axis (that is, the center axis of rotation rotation of the detector) AXd. This simplifies the geometric positional relationship between the rotation (rotation) of the X-ray tube 23 and the detector 24 and the X-ray path, and makes it easier to design the attitude control of the X-ray tube 23 and the detector 24. Become.

  For this 3D reference tomographic plane trajectory SS (standard trajectory), for example, speed patterns for performing two types of imaging methods (both panoramic imaging) called standard imaging and orthogonal imaging can be set. The standard imaging is an imaging method in which X-rays are irradiated so as to avoid the left and right jaw bones as much as possible with respect to the locus SS. The orthogonal imaging is an imaging method in which X-rays are irradiated so that the path is always orthogonal to the locus SS. FIG. 10 schematically shows an X-ray path in a half of the scan range θ = 220 ° in standard imaging (a range of ± 110 ° if the predetermined folding position is θ = 0 °).

  Furthermore, even in the same standard imaging, the size of the trajectory SS (standard trajectory) of the 3D reference tomographic plane varies depending on differences between adults and children. The same applies to orthogonal shooting. For this reason, a plurality of types of velocity patterns for standard imaging and / or orthogonal imaging are preliminarily rotated in a partial range in the circumferential direction around the central axis CA of the X-ray tube 23 (here, partial revolution). , Rotation of a partial range around the axis AXs of the X-ray tube 23 (here, partial rotation), rotation of a partial range in the circumferential direction around the central axis CA of the detector 24 (partial rotation) Revolving) and a partial range of rotation about the axis AXd of the detector 24 (partial rotation).

  In this velocity pattern, the horizontal axis represents the scan time (for example, 12 seconds), and the vertical axis represents the revolution or rotation angle. In this embodiment, the revolution means that the X-ray tube 23 and the detector 24 rotate or rotate in the circumferential direction along each of the trajectories Tx and Td separated from the central axis CA by a predetermined distance. Means that the X-ray tube 23 and the detector 24 themselves rotate or rotate around the respective rotation axes AXs and AXd. Further, “partial” refers to rotating a partial range in the entire circumferential direction, and refers to a partial angular range in the 360 rotation range.

  FIG. 11 and FIG. 12 illustrate a speed pattern indicating the revolution and rotation of the X-ray tube 23 and a speed pattern indicating the rotation and rotation of the detector 24 when performing standard imaging and orthogonal imaging. For example, the curves A and B in FIGS. 11 and 12 are for an orthogonal radiograph for adults of the X-ray tube 23 and the detector 24 in the range of about 220 ° when the circumferential angle θ is set as shown in FIG. The revolving and rotation speed patterns are shown respectively. As can be seen from the speed patterns A and B, the rotation speed is increased in those portions so that the left and right jawbone portions are scanned as much as possible, and the speed is set so as to be dense in the portion of the dentition TR. . Similarly, curves A ′ and B ′ in FIGS. 11 and 12 respectively show the revolution and rotation speed patterns of the X-ray tube 23 and the detector 24 for standard imaging for adults in the range of about 220 °.

  Note that the rotation and rotation speed patterns for orthogonal shooting and standard shooting for children use portions in the horizontal axis 1 to 11 seconds in FIGS. 11 and 12. In other words, although the angular range of revolution and rotation is the same, a standard trajectory for children with a smaller collection range is secured by shortening the collection time. This is based on the statistics that the dentition between the child and the adult grows as the adult grows, but the size of the front teeth does not change much.

  Curves A and B in FIG. 12 show partial rotations of the X-ray tube 23 and the detector 24, that is, so-called swing patterns within a certain angle. As this constant angle, about ± 15 ° is set. This angle is set to 0 ° when the X-ray tube 23 and the detector 24 face each other. As shown in FIG. 11, the swinging of the X-ray tube 23 and the detector 24 itself is not constant, so the X-ray path XB does not always pass through the central axis CA. There are far more X-ray paths XB with the central axis CA removed. This is to increase the degree of freedom in designing the X-ray path XB as indicated by the arrow YJ in FIG. When the X-ray path XB does not pass through the central axis CA, if nothing is done, the X-ray tube 23 and the detector 24 are deviated from the facing state and the detection sensitivity is lowered. Therefore, when the X-ray path does not pass through the central axis CA, it is necessary to cooperatively swing the X-ray tube 23 and the detector 24 according to the amount of deviation of the X-ray path XB from the central axis CA. is there. Of course, it is possible to swing one of the detectors 24, but in this case, the degree of freedom in setting the X-ray path XB is lowered, so it is better to use both swings together. Such a speed pattern is installed in advance in the apparatus by the manufacturer.

That is, the types of speed patterns prepared in this embodiment are
・ Speed pattern for standard shooting for adults (speed pattern group consisting of curves A ′ and B ′ in FIG. 11 and curves A ′ and B ′ in FIG. 12),
-Speed pattern for orthogonal shooting for adults (speed pattern group consisting of curves A and B in FIG. 11 and curves A and B in FIG. 12),
Speed pattern for standard shooting for children (speed pattern group consisting of time-reduced curves A ′ and B ′ in FIG. 11 and time-reduced curves A ′ and B ′ in FIG. 12),
The speed pattern of the orthogonal photographing for adults (the speed pattern group consisting of the time shortened curves A and B in FIG. 11 and the time shortened curves A and B in FIG. 12),
It is.

  Furthermore, the velocity patterns of the X-ray tube 23 and the detector 24 are not necessarily those for the standard 3D reference tomographic plane as described above. This may be a velocity pattern for an arbitrarily shaped 3D reference tomographic plane. For example, the shape of the projection trajectory (standard trajectory) SS on the XY plane of the 3D reference tomographic plane shown in FIG. 10 described above may be a horseshoe shape in which the vicinity of the front teeth is narrower or wider. Conversely, the back teeth may form a narrower or wider horseshoe shape. It is also possible to set the above four types of velocity patterns for performing standard imaging and / or orthogonal imaging on a 3D reference tomographic plane having such a modified projection locus SS. The velocity pattern related to such a deformed shape can be prepared in advance on the system side, or can be calculated and stored in a computer at a medical site or a research site.

  A plurality of speed patterns set with a high degree of freedom is stored as a table in the first storage unit 134 (storage means: see FIG. 9). For this reason, the controller 133 reads out a desired speed pattern from the first storage unit 134 to the work area through interactive exchange with the operator. When the scan is started, the controller 133 controls the rotation drive mechanisms 83, 21B, and 22B shown in FIG. 9 according to the read speed pattern. As a result, X-rays irradiated from the X-ray tube 23 and incident on the detector 24 through the jaw JW of the subject P are designated by desired standard imaging or orthogonal imaging for each rotation angle θ in the circumferential direction. Pass the path XB. For this reason, the detector 24 always outputs the detected frame data while maintaining a posture facing the X-ray tube 23. This frame data is reconstructed into a panoramic image by the data processor 135.

  Next, an example of a panorama shooting procedure by the panorama shooting apparatus 1 according to the present embodiment will be described with reference to FIG.

  When using the panoramic photographing apparatus 1, first, the panoramic photographing apparatus 1 is positioned at a predetermined position on the back side of the dental treatment chair 2 and fixed to the floor surface. At this time, the operation lever 52 described above is operated to push the pin 50 down, and the pin 50 is engaged with the floor fixing portion 53. Thereby, positioning and fixation with respect to the dental treatment chair 2 of the main body BD of the panoramic imaging apparatus 1 are achieved. Thereby, when the backrest is tilted while sitting on the dental treatment chair 2, the positioning of the scan of the panoramic imaging device 1 with respect to the head H of the patient P is facilitated.

  When the panorama photographing apparatus 1 is positioned, the operator (or dentist) turns on the power of the apparatus. As a result, the controller 133 of the console 15 is activated and interactively executes the following processing. First, the controller 133 displays a login screen on the display 136, and thus performs login (FIG. 13, step S1). After this, the controller 133 causes the display 136 to display a panoramic shooting GUI (graphical user interface) (not shown). Therefore, the dentist inputs patient information (imaging date, patient ID, patient name, etc.) from the patient information input screen provided by this GUI (step S2).

  Next, in the same manner, a shooting type is selected on the GUI screen of the display 136 (step S3). In this embodiment, one of the four types of shooting, which is set by default, is standard shooting for adults, orthogonal shooting for adults, standard shooting for children, and orthogonal shooting for children. Selected. Of course, if an imaging method having a customized size trajectory is set, it may be selected. In response to this selection, the controller 133 reads a speed pattern for executing the selected imaging method from the table in the first storage unit 134 to the work area. For example, when standard shooting for adults is selected, four types of pattern data of speed patterns A ′ and B ′ illustrated in FIGS. 11 and 12 are read out.

  Next, shooting conditions are set (step S4). This setting is to set the tube voltage and tube current. When the shooting type is selected as described above, the controller 133 automatically sets the recommended shooting conditions. It is.

  When the imaging conditions are set, the controller 133 displays the screen so that the dentist positions the patient P, and waits during that time (step S5).

  Therefore, the dentist causes the patient P and the attendant to wear X-ray protective clothing, and causes the patient P to sit on the dental treatment chair 2. Next, the scattered radiation shielding cover 14 </ b> C is manually retracted to the rear side (see an imaginary line “retraction position” in FIG. 3). At this stage, the X-ray tube arm 21 and the detector arm 22 are positioned at the respective standby positions (see FIG. 14A).

  Further, with the head H of the patient P attached to the headrest HR of the treatment chair 2, the backrest is tilted and the head H is introduced into the imaging space S. At this time, as described above, the main body BD of the panoramic photographing apparatus 1 and the dental treatment chair 2 are fixed to each other via the floor surface. Therefore, the headrest HR (see FIG. 3) of the dental treatment chair 2 is located at the approximate center of the imaging space S. In other words, the head H of the patient P is also guided to a substantially intermediate portion between the X-ray tube arm 21 and the detector arm 22 waiting in the imaging space S.

  When this introduction is completed, the dentist presses the GUI laser irradiation button (not shown) of the display 136 and presses the positioning irradiation button. In response to this, the controller 133 rotates only the detector arm 22 and moves it to a positioning position, that is, a position directly beside the patient's head H (see FIG. 14B). Further, the controller 133 drives the midline laser 211, the horizontal laser 212, the occlusal plane laser 213, and the canine laser 214 (step S6). These four types of laser beams are projected onto the face of the patient P (see FIG. 14B ′).

  Next, the GUI of the display 136 instructs the dentist to position the face of the patient P (step S7). First, the dentist adjusts the height of the elevator 14 via the controller 133 so that the linear beam BM1 from the canine laser 214 matches the canine of the patient P. Next, the position of the patient's face is finely adjusted while viewing the beams from the remaining lasers 211 to 213. Specifically, the position of the patient in the body axis direction is adjusted so that the linear beam BM2 from the occlusal plane laser 213 matches the occlusal plane of the patient P. The midline sagittal plane of the head H is aligned with the linear beam BM3 from the midline laser 211. Further, the Frankfurt plane is aligned with the linear beam BM4 emitted from the horizontal laser 212.

  After positioning, the scattered radiation shielding cover 14 </ b> C is moved to the forward imaging position (see the solid line “imaging position” in FIG. 3). As a result, as shown by the solid line in FIG. 3, the head H of the subject P is positioned in the defined imaging space S. In order to more reliably perform X-ray shielding, the front surface of the scattered radiation shielding cover 14C may be covered with an X-ray protective cloth containing lead after this positioning. This can be easily performed by detachably attaching a hinge or the like formed on the edge of the upper front surface of the cover 14C.

  Then, since the GUI of the display 136 displays a completion of preparation, the setup button on the GUI is pushed (step S8). In response to this, the controller 133 rotates the X-ray tube arm 21 and the detector arm 22 to a predetermined setup position (see FIG. 14C). The dentist finally confirms this setup condition. At this time, the state inside the scattered radiation shielding cover 14C, such as the state of the patient P and the arm position, can be confirmed by observing through the window portion by the translucent portion 14TR.

  If there are no problems with this confirmation, the dentist performs a scan. This scan is executed when the dentist holds the irradiation switch 56 and presses and keeps pressing the switch 56 from a slightly distant place (step S9). Thereby, as described above, the X-ray tube arm 21 and the detector arm 22 revolve independently of each other along the velocity pattern according to the selected imaging type, and the opposing arm portions 21A and 22A, that is, X The rotational movements of the tube 23 and the detector 24 are controlled independently of each other. That is, the collection of frame data is performed by the scan based on the 4-axis independent control described above. Symbols Ks and Kd in FIG. 14D schematically show the trajectory of the movement of the X-ray tube 23 and the detector 24 due to the revolving motion of the X-ray tube arm 21 and the detector arm 22. As indicated by the symbols Ks and Kd, the X-ray tube 23 turns around the rear side of the head H, and the detector 24 turns around the front side of the head H. During this rotation, the postures of the X-ray tube 23 and the detector 24 are controlled so as to face each other, and an X-ray scan is performed.

  During this scan, the dentist observes the patient while looking inside from the translucent portion 14TR of the scattered radiation shielding cover 14C. Therefore, during the scan, the controller 133 monitors whether the irradiation switch 56 is turned off, that is, whether the dentist feels any inconvenience and releases the push button of the irradiation switch 56 (that is, switch OFF) (step S10). ). If there is no abnormality, the determination in step S10 is NO and the scan is continued as it is. However, in the case of YES determination, each drive unit is immediately instructed to stop scanning (step S11). This monitoring is the same for the shock sensor (steps S12 and S11). If there is no abnormality, the dentist continues to press the irradiation switch 56, and when the rotation angle reaches the end point of the predetermined angle range, the scanning is automatically ended (step S13). That is, the X-ray tube arm 21 and the detector arm 22 scan while moving the scan range θ (for example, about 220 °) commanded by the operation pattern for 12 seconds (for an adult), for example, and when the scan is completed. Then, it automatically returns to the initial standby position (see FIG. 14D).

  Thereafter, the scattered radiation shielding cover 14C is retracted rearward to release the patient (step S13).

  This completes a series of panoramic photography. The frame data collected by this scan is stored in the first storage unit 134. For this reason, the data processor 135 reconstructs a tomographic image of the dentition TR from this frame data using a predetermined profile curve (a curve defining the amount of overlap between the frame data) for the shift & add process. be able to. Specifically, for this reconstruction, for example, the technique described in US-2012-0230467 A1 can be adopted.

[First modification]
Here, the modification (1st modification) which concerns on embodiment mentioned above is demonstrated with reference to FIG.15 and FIG.16. Here, the same reference numerals are given to components that exhibit the same or equivalent functions as the components of the panoramic photographing apparatus 1 described above, and the description thereof is omitted.

  FIGS. 15 and 16 show an example of the internal structure of the main body BD that can be mounted on the panoramic photographing apparatus 1 in place of the drive mechanism described above, and shows a state in which a cover or the like covering the outside is removed. Yes.

  In the case of this example, the structure is extremely simplified, and a base part BS that is positioned on the dental treatment chair 2 via the floor surface, and a tower part TW that can be height-adjusted from the base part BS, The driving unit DV provided on the upper portion of the tower unit TW, and the arm unit AM which is attached to the tower unit TW at the upper position and is linked to the driving unit DV.

  Among these, the base part BS has a pedestal part 12 as in the above-described embodiment, and a telescopic elevator 141 is mounted thereon. The elevator 141 has the function of the elevator 14 described in the above-described embodiment. The elevator 141 is configured such that the outer movable strut 142 can move up and down with respect to the inner fixed strut with a stroke of, for example, 270 mm in the height direction. The elevator 141 incorporates a drive mechanism such as a DC motor and a height sensor.

  The movable support 142 is provided with a drive unit DV having a rotation mechanism similar to the rotation drive mechanism 83 described above. The drive unit DV includes support plates 143 and 144 projecting from both side surfaces of the upper portion of the movable column 142, and electric motors 145 and gearboxes with electromagnetic brakes disposed on the support plates 143 and 144, respectively. 146. In addition, the drive unit DV includes a rotation drive mechanism 147 provided through the upper portion of the movable column 142 in the front-rear direction (Z-axis direction) orthogonal to the projecting direction of the support plates 143 and 144. The end portion on the front side of the rotation drive mechanism 147 protrudes from the movable column 142, and the support portion 21L of the X-ray tube arm 21 and the support portion 22L of the detector arm 22 described above are provided on the protruding portion. It is attached coaxially. In addition, an end portion on the rear surface side of the rotation drive mechanism 147 also protrudes from the movable column 142, and two reducers 148 and 149 are coaxially attached to the protruding portion. Each of the motors 145 and 146 is a stepping motor, and includes gear boxes 145A and 146A on the output shaft side. These gear boxes 145A and 146A are linked to the speed reducers 148 and 149 via belts 150 and 151, respectively. Yes.

  For this reason, when the motor 145 for rotating the X-ray tube rotates, the rotational force is decelerated by the gearbox 145A and the speed reducer 148 and transmitted to the rotation drive mechanism 147. Similarly, when the detector rotation motor 146 rotates, the rotational force is reduced by the gear box 146A and the reduction gear 149 and transmitted to the rotation drive mechanism 147. The rotation drive mechanism 147 incorporates a known shaft mechanism that transmits rotation independently from each other inside and outside by a bearing or the like. For this reason, two shafts inside and outside the shaft mechanism are linked to the support portion 21L of the X-ray tube arm 21 and the support portion 22L of the detector arm 22, respectively. Accordingly, the rotation of the X-ray tube rotation motor 145 causes the X-ray tube arm 21 to rotate in the circumferential direction as described above, and the rotation of the detector rotation motor 146 similarly causes the detector arm 22 to move in the circumferential direction. Rotate. Their rotational direction, rotational speed, and rotational range can be controlled independently of each other by controlling the driving of the two motors 145 and 146 separately.

  In addition, an electric motor 152 with a gear box for causing the opposing arm portions 21A and 22A to rotate at the distal ends of the support portion 21L for the X-ray tube and the support portion 22L for the detector provided as the arm portion AM. , 153 are provided. These electric motors 152 and 153 are stepping motors, and their output shafts are linked to opposite arm portions 21A and 22A on the X-ray tube side and detector side, respectively. For this reason, the above-described rotational movements of the opposing arm portions 21A and 22A on the X-ray tube side and the detector side, that is, the X-ray tube 23 and the detector 24, can be controlled independently of each other by the rotation of the electric motors 152 and 153. It has become.

  As described above, the above-described four-axis rotation operation can also be independently controlled by the mechanism according to this modification, and the above-described scan control can be performed.

  As described above, according to the panoramic imaging apparatus 1 according to the above-described embodiment and the modification thereof, the X-ray tube 23 and the detector 24 are always facing each other while moving independently on different circular orbits. In addition, attitude control of four axes (that is, partial revolution and rotation of the X-ray tube 23 and partial revolution and rotation of the detector 24) is performed. For this reason, the apparatus can be miniaturized and the degree of freedom in designing the X-ray path is extremely high. Moreover, the trajectory of the X-ray path is arbitrarily determined so that a desired image can be taken.

  Specifically, the X-ray tube 23 and the detector are arranged around two identical orbits around the same central axis CA passing through one rotation center O and having different distances (diameters) from the central axis CA. 24 are rotated (revolved) independently of each other. In addition, the X-ray tube 23 and the detector 24 are rotated (rotated or swung) around the first and second axes AXs and AXd parallel to the rotation axis CA at the respective rotation positions. it can. That is, since both the X-ray tube 23 and the detector 24 can rotate (attitude control), they can always maintain a state of facing each other. Thus, the X-ray tube 23 and the detector 24 are relatively simple and can be reduced in size by rotating on their respective circular orbits. The fan beam-shaped X-ray path can be drawn from various angles in the imaging space S and can be easily changed. For this reason, various focal planes can be set in the imaging space S.

  In addition, the distances from the central axis CA to the X-ray tube 23 and the detector 24 are different. That is, the detector 24 can be rotated at a position as close as possible to the imaging region JW of the subject P. As a result, if the focal spot size (0.15 mm in this embodiment) of the X-ray tube 23 is the same, the magnification rate increases and the resolution increases as the detector 24 approaches the subject P. Detection accuracy is also improved.

  As described above, in the panoramic imaging apparatus 1, the X-ray XB emitted from the X-ray tube 23 is always limited to the size of the X-ray incident window WD of the detector 24. In addition, the X-ray tube 23 and the detector 24 are driven and controlled independently by the four axes, and both are always opposed to each other via the jaw of the subject P during scanning. For this reason, the X-ray XB irradiated from the X-ray tube enters the detector 24. Therefore, the amount of scattered radiation leaking from the imaging space S is small. In particular, since X-rays focused in a fan beam shape having a rectangular opening rotate around the central axis CA, the amount of scattered radiation leaking in the front-rear direction of the imaging space S is further reduced.

  In particular, in the case of the panoramic photographing apparatus provided with the rotation drive mechanism described with reference to FIGS. 15 and 16, two electric motors that make a tower portion TW stand up from the base portion BS and perform a revolving motion on the upper portion of the tower portion TW. Motors 145 and 146 were provided. For this reason, compared with the structure which arrange | positions these drive sources in base part BS, the routing of a rotation transmission belt is simplified.

  Furthermore, in this modification, a control board (not shown) on which the circuit of the console 15 shown in FIG. 9 is mounted is arranged in the space US on the upper surface of the tower unit TW. For this reason, the power supply box 13 that forms the base portion BS is equipped with only a converter that converts the voltage from AC 100V to DC 24V, and only a cable that sends the DC output to the control board or the electric motor is routed. For this reason, compared with the case where this control board is placed in the power supply box 13, wiring is also simplified.

  Further, when the X-ray tube arm 21 and the detector arm 22 are rotated around the central axis CA, no counterweight is provided on the opposite side of these arms, that is, on the back side of the rotation drive mechanism 147. The rotation of the arms 21 and 22 is controlled by precisely controlling along the speed pattern. Usually, when such an arm is rotated so that its rotational radial direction is the height direction, a counterweight is often provided to suppress rotational unevenness due to the gravity. However, since the counterweight is not provided in this modification, the structure is simplified and the weight is reduced accordingly.

[Second modification]
Furthermore, a modified example related to the scattered radiation shielding cover 14C that can be mounted on the panorama photographing apparatus 1 according to the above-described embodiment will be described.

  The translucent portion 14TR formed on the cover 14C may be an appropriate rectangular translucent window 14TR ′ provided on both side surfaces as shown in FIG. 17 instead of the shape of FIG. 5 described above. The translucent window 14TR ′ is formed of a resin material containing lead, and the other non-translucent portion 14NT is formed of a metallic plate material. Also by this, the effect of shielding the scattered radiation can be expected, and the entire weight can be reduced by reducing the lead-containing portion.

  This translucent window 14TR ′ is primarily capable of observing the state of the patient by the dentist during scanning, and it is better if the discomfort of the patient who is not good at closing can be reduced. For this reason, the shape of the translucent window 14TR ′ is not limited to a rectangle, but may be a slit, a circle, or a triangle. Further, the translucent window 14TR ′ may be provided only on one side surface of the cover 14C. The position in the height direction of the translucent window 14TR ′ is usually set so that a dentist who performs a scanning operation in a standing position can observe the head of the patient inside through the translucent window 14TR ′.

  As described above, according to the panoramic imaging apparatus 1 according to the above-described embodiment and the modification thereof, the X-ray tube 23 and the detector 24 are always facing each other while moving independently on different circular orbits. In addition, attitude control of four axes (that is, partial revolution and rotation of the X-ray tube 23 and partial revolution and rotation of the detector 24) is performed. For this reason, the apparatus can be miniaturized and the degree of freedom in designing the X-ray path is extremely high. Moreover, the trajectory of the X-ray path is arbitrarily determined so that a desired image can be taken.

  Specifically, the X-ray tube 23 and the detector are arranged around two identical orbits around the same central axis CA passing through one rotation center O and having different distances (diameters) from the central axis CA. 24 are rotated (revolved) independently of each other. In addition, the X-ray tube 23 and the detector 24 are rotated (rotated or swung) around the first and second axes AXs and AXd parallel to the rotation axis CA at the respective rotation positions. it can. That is, since both the X-ray tube 23 and the detector 24 can rotate (attitude control), they can always maintain a state of facing each other. Thus, the X-ray tube 23 and the detector 24 are relatively simple and can be reduced in size by rotating on their respective circular orbits. The fan beam-shaped X-ray path can be drawn from various angles in the imaging space S and can be easily changed. For this reason, various focal planes can be set in the imaging space S.

  In addition, the distances from the central axis CA to the X-ray tube 23 and the detector 24 are different. That is, the detector 24 can be rotated at a position as close as possible to the imaging region JW of the subject P. As a result, if the focal spot size (0.15 mm in this embodiment) of the X-ray tube 23 is the same, the magnification rate increases and the resolution increases as the detector 24 approaches the subject P. Detection accuracy is also improved.

  As described above, in the panoramic imaging apparatus 1, the X-ray XB emitted from the X-ray tube 23 is always limited to the size of the X-ray incident window WD of the detector 24. In addition, the X-ray tube 23 and the detector 24 are driven and controlled independently by the four axes, and both are always opposed to each other via the jaw of the subject P during scanning. For this reason, the X-ray XB irradiated from the X-ray tube enters the detector 24. Therefore, the amount of scattered radiation leaking from the imaging space S is small. In particular, since X-rays focused in a fan beam shape having a rectangular opening rotate around the central axis CA, the amount of scattered radiation leaking in the front-rear direction of the imaging space S is further reduced.

  In particular, in the case of the panoramic photographing apparatus provided with the rotation drive mechanism described with reference to FIGS. 15 and 16, two electric motors that make a tower portion TW stand up from the base portion BS and perform a revolving motion on the upper portion of the tower portion TW. Motors 145 and 146 were provided. For this reason, compared with the structure which arrange | positions these drive sources in base part BS, the routing of a rotation transmission belt is simplified.

  Furthermore, in this modification, a control board (not shown) on which the circuit of the console 15 shown in FIG. 9 is mounted is arranged in the space US on the upper surface of the tower unit TW. For this reason, the power supply box 13 that forms the base portion BS is equipped with only a converter that converts the voltage from AC 100V to DC 24V, and only a cable that sends the DC output to the control board or the electric motor is routed. For this reason, compared with the case where this control board is placed in the power supply box 13, wiring is also simplified.

  Further, when the X-ray tube arm 21 and the detector arm 22 are rotated around the central axis CA, no counterweight is provided on the opposite side of these arms, that is, on the back side of the rotation drive mechanism 147. The rotation of the arms 21 and 22 is controlled by precisely controlling along the speed pattern. Usually, when such an arm is rotated so that its rotational radial direction is the height direction, a counterweight is often provided to suppress rotational unevenness due to the gravity. However, since the counterweight is not provided in this modification, the structure is simplified and the weight is reduced accordingly.

  On the other hand, in the case of the present embodiment and the modified example, the upper surface, both side surfaces, and the bottom surface that define the imaging space S are surrounded by the scattered radiation shielding plate 20 of the scattered radiation shielding cover 14C and the bottom surface portion 14C described above. Thus, X-ray shielding is performed. For this reason, X-rays leaking outside from the imaging space S during panoramic imaging or partial imaging can be reliably reduced or shielded. Thereby, even when panoramic imaging or partial imaging driven by the X-ray tube 23 is performed, the influence of X-rays on the outside of the imaging space S can be almost ignored.

  This panorama photographing apparatus 1 is movable. Therefore, it is possible to provide a panoramic imaging apparatus having an X-ray shielded space that should be called a “portable dental X-ray shield room”. Thereby, X-ray imaging | photography of a jaw part can be performed with the patient lying in the dental treatment chair on its back. Leakage to the outside from a very localized small imaging space around the jaw during the imaging can be greatly reduced.

  For the subject, the head H is placed in the scattered radiation shielding cover 14C. The cover 14C is provided with a translucent portion 14TR. For this reason, the outside can always be seen, and patients who are not good at closing can cope with it.

  On the other hand, in the embodiment and the modification described above, the caster 11 is provided as a moving unit that moves the main body BD (except the console) of the apparatus 1. However, this moving means is not limited to casters. A gripping portion may be provided on the main body of the apparatus 1, and the gripping portion may be held and moved by hand. Moreover, you may provide the wheel which rotates electrically on the lower surface of the base part 12. FIG. Any means capable of freely moving the main body BD of the apparatus 1 according to the present application to the side of the dental treatment chair 2 may be used.

  The present invention is not limited to the configurations shown in the above-described embodiments and modifications, and can be implemented with various modifications without departing from the gist of the claims.

1 Dental panoramic radiography equipment (X-ray radiography equipment)
11 Casters (moving means)
12 Base 14 Elevator 14B Back 14C Scattered ray shielding cover 14L, 14R Side 14U Upper 17 17 Console (reading means, control means)
21 X-ray tube arm 21A Opposing arm portion 21L Support portion 22 Detector arm 22A Opposing arm portion 22L Support portion 23 X-ray tube 24 Detectors 21B, 22B, 83; 145, 146, 147, 148, 149, 150, 151, 155, 153 (rotation drive unit (drive means))
133 Controller 134 First storage unit 135 Data processor O Rotation center (arm rotation center)
CA central axis (arm rotation central axis)
AXs first axis (X-ray tube swing axis)
AXd second axis (center axis of rotation of detector swing)
C Center position in the width direction of the detector (detection center position)
FP X-ray tube X-ray focal point (X-ray focal point position)

Claims (7)

An X-ray tube having a point-like focus and irradiating X-rays extending from the focus;
A detector that detects the X-rays emitted from the X-ray tube and outputs data corresponding to the amount of the X-rays, and has a predetermined rotation center for the X-ray tube and the detector. In an X-ray imaging apparatus capable of rotating around a central axis passing through
A tube housing that houses the X-ray tube so that the X-ray tube emits X-rays, and a tube support that rotatably supports the tube housing around a first axis parallel to the central axis An X-ray tube arm with a portion;
First driving means for rotating the tube housing portion around the first axis with respect to the tube support portion;
A detector accommodating portion that accommodates the detector so as to make the X-ray incident thereon; and a detector supporting portion that rotatably supports the detector accommodating portion around a second axis parallel to the central axis. A detector arm with
Second driving means for rotating the detector housing portion around the second axis with respect to the detector support portion;
A third driving means for supporting the X-ray tube arm and the detector arm so that they can be driven coaxially independently of each other, and driving both arms to rotate around the central axis;
The X-ray tube arm, the detector arm, the tube housing portion, and the detector housing portion according to a speed pattern for rotating the X-ray tube arm independently of each other for scanning by the X-ray. And control means for controlling the third drive means;
An X-ray imaging apparatus comprising: A first distance from the central axis to the first axis is set to a value greater than a second distance from the central axis to the second axis;
The X-ray imaging apparatus according to claim 1, wherein the X-ray tube and the detector are rotatable along mutually different circular orbits.   The tube arm and the detector arm are arranged in an imaging space covered with a scattered radiation shielding body that shields the scattered radiation of the X-ray in a radial direction along a cross section orthogonal to the central axis. The X-ray imaging apparatus according to claim 1 or 2.   The speed pattern includes a first speed pattern for rotating the tube arm about the central axis, a second speed pattern for rotating the detector arm about the central axis, and the tube receiving portion. A third speed pattern for rotating the detector around the first axis, and a fourth speed pattern for rotating the detector housing portion about the second axis. The X-ray imaging apparatus according to any one of Items 1 to 3. The X-ray imaging apparatus is a dental X-ray panoramic imaging apparatus,
The first, second, third, and fourth speed patterns are speed patterns for scanning the X-rays so as to optimally focus on a reference tomographic plane that is set in advance for the dentition of the subject. The X-ray imaging apparatus according to claim 4, wherein: The X-ray imaging apparatus is a dental X-ray panoramic imaging apparatus,
The first, second, third, and fourth velocity patterns irradiate the X-ray beam so as to be orthogonal to a reference tomographic plane that is set in advance with respect to the dentition of the subject, and the reference The X-ray imaging apparatus according to claim 4, wherein the X-ray imaging apparatus is a speed pattern that scans the X-rays so that a tomographic plane is optimally focused. The speed pattern is a pattern in which the horizontal axis represents time when scanning a predetermined angle range around the central axis, and the vertical axis represents the angle of the predetermined angle range,
Storage means for presetting and storing the speed pattern;
The X-ray imaging apparatus according to claim 1, further comprising: a reading unit that reads information on the speed pattern from the storage unit and provides the information to the control unit during the scanning. .

Images