JP2013085667A - Dental x-ray imaging equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily provide focused images with less blur at least even when a dental arch is off a reference object plane.SOLUTION: A dental X-ray imaging equipment includes: an X-ray irradiation part 110 for irradiating a subject O with X-rays; an X-ray detection part 120 for outputting electric signals of a digital amount according to incident X-rays at a fixed frame rate; a turning arm 3 for moving the pair of the X-ray irradiation part 110 and the X-ray detection part 120 around the subject while the X-ray irradiation part 110 and the X-ray detection part 120 are opposite to each other with the subject O interposed between them ; a storage means 22 for successively storing, as frame data, photographic image signals for tomosynthesis output by the detection part 120 as the turning arm 3 moves the X-ray irradiation part 110 and the X-ray detection part 120 around the subject O; and an image processing means 20 for performing image reconstruction arithmetic operation based on the frame data stored in the storage means 22 and obtaining panoramic images.

Description

  The present invention relates to a dental X-ray imaging apparatus for imaging a specific part of a subject, for example, an X-ray panoramic CT apparatus or a head and neck X-ray CT apparatus for imaging a panoramic image such as a dental arch. The present invention relates to an apparatus for performing tomosynthesis for reconstructing a tomographic image having an arbitrary cutting height by one tomography.

  Tomosynthesis is known as an X-ray tomographic imaging method. In tomosynthesis, X-rays are emitted from a X-ray source to a subject at a plurality of different angles, X-rays transmitted through the subject are detected by an X-ray detector, and a plurality of captured images (for tomosynthesis are used). Take a picture. Then, the plurality of tomosynthesis captured images are reconstructed to obtain a tomographic image (reconstructed tomographic image) at an arbitrary tomographic position (cutting height).

  Conventionally, a dental panoramic X-ray imaging apparatus has a tomographic plane (referred to as a reference tomographic plane) along a trajectory mechanically set in an imaging space, and this reference tomographic plane is focused. . For this reason, when the dental arch is positioned along the reference tomographic plane, the reconstructed image is not blurred. However, when the dental arch is displaced from the reference tomographic plane, the image is blurred. Therefore, if you want to see the unclear part with high accuracy, reposition the subject so that the blurred part can be seen clearly and re-collect the data, or perform intraoral photography of the blurred part to make it clearer. I got a good picture.

  As an example of the prior art intended to solve such a problem, as in Patent Document 1, a detector capable of collecting images at high speed (for example, 300 FPS) is used to capture all of the detected data into a computer, and a tomosynthesis method An X-ray panoramic imaging apparatus has been developed that can freely change the tomographic plane using software. In the case of this apparatus, information (gain) of distances of a plurality of tomographic planes parallel to the detection surface (X-ray incident surface) of the detector is obtained in advance using a phantom. At the time of imaging, data is collected while rotating a pair of an X-ray tube and a detector around the jaw of the subject. The position of the rotation center at this time approaches or leaves the dentition. The collected data is processed by the tomosynthesis method using the above-described distance information, thereby creating an image with less blur. In this Patent Document 1, the step of designating the region of interest on the maxillofacial surface and the region of interest by designating the region of interest based on dental arch orthographic information regarding the direction in which the dental arch is viewed from the buccal side toward the tongue side An X-ray panoramic image display method has been proposed, comprising: an X-ray panoramic image in which a region is viewed normally by an image processing unit; and an X-ray CT image in which the region of interest is viewed in a display unit. .

JP 2007-136163 A

  In the case of the panoramic imaging apparatus described in Patent Document 1 described above, a panoramic image is created on the assumption that a plurality of tomographic planes to be subjected to the tomosynthesis method are parallel to the detection plane of the detector. After the image is digitized, at least when the dentition is accurately positioned on the reference tomographic plane, it is possible to create an image having no distortion in both the vertical and horizontal directions only at the center of the front tooth. However, if the positioning condition is not met, the image will always be distorted. In addition, when the dentition is not located along the reference tomographic plane, the reconstructed panoramic image is also blurred in the horizontal direction.

  The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to easily provide an in-focus image with little blur even when the dental arch is out of the reference tomographic plane. And

  The dental X-ray imaging apparatus according to the present invention includes an X-ray irradiation unit that irradiates a subject with X-rays, and an X-ray detection unit that outputs a digital electric signal corresponding to the incident X-rays at a constant frame rate. And a turning means for moving the pair of the X-ray irradiation unit and the X-ray detection unit around the subject in a state of facing each other across the subject, and the turning means is the X-ray irradiation unit And storage means for sequentially storing tomosynthesis tomographic image signals output by the detection section as the X-ray detection section moves around the subject as frame data; and frame data stored in the storage means And image processing means for obtaining a panoramic image by performing image reconstruction calculation based on the above.

  The image processing unit may be configured to reconstruct a plurality of panoramic images in the depth direction across the reference cross section.

  Furthermore, the image processing means can be configured to adjust the focal point by sliding the reference cross section in the depth direction.

  The image processing means can be configured to generate a partial cross-sectional image having an optimum focus corresponding to the position of a specified partial region of the panoramic image of the desired tomographic plane from the panoramic image data.

  The image processing means can reconstruct a tomosynthesis tomographic image using a filtered back projection method (FBP method).

  The image processing means reconstructs a tomosynthesis tomographic image using a shift addition method, and the image processing means reconstructs a tomosynthesis tomographic image using a filter back projection method (FBP method). And a shift addition image or an FBP image can be displayed on the display unit.

  In the present invention, the tomosynthesis method (tomosynthesis) is used to obtain an image of the tomographic plane, so that no artifacts are generated around the implant body, and the condition of the bone is known. Moreover, an image suitable for diagnosis can be obtained by switching the reconstruction by the shift addition method and the FBP method.

It is a block diagram explaining the basic composition of the dental head and neck X-ray CT imaging apparatus by this invention. 1 is a front view of a sitting-type dental head and neck X-ray CT imaging apparatus according to the present invention. FIG. 1 is a side view of a sitting-type dental head and neck X-ray CT imaging apparatus according to the present invention. 1 is a top view of a dental head and neck X-ray CT imaging apparatus of a sitting position according to the present invention. It is a functional block diagram for demonstrating the image process part of the X-ray panoramic image and CT image display apparatus by this invention. It is a block diagram for demonstrating other embodiment of the X-ray panoramic image and X-ray CT image display apparatus by this invention. It is a figure which shows the orbit figure of panoramic imaging. It is a schematic diagram which shows the state of the panoramic imaging by this invention. It is a schematic diagram which shows an example of the display screen by this invention. It is a schematic diagram which shows an example of the display screen by this invention. It is a flowchart which shows the image processing operation | movement of this invention. It is a flowchart which shows the processing operation of the FBP method of this invention. It is a flowchart which shows the image processing operation | movement of this invention. It is a flowchart which shows the image processing operation | movement of this invention.

  Hereinafter, an embodiment in the case of performing tomosynthesis imaging of a dental panoramic imaging apparatus for a dental region of a subject (patient) or a dental X-ray imaging apparatus for imaging a head and neck region will be described in detail with reference to the drawings. To do. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated in order to avoid duplication of description.

  FIG. 1 is a block diagram illustrating a basic configuration of a dental head and neck X-ray CT imaging apparatus as a dental X-ray imaging apparatus. Using this apparatus, dental panoramic X-ray imaging or head and neck X-ray CT imaging can be performed. The dental head and neck X-ray CT imaging apparatus includes an X-ray imaging apparatus main body 1 and an X-ray panoramic CT image display apparatus 2 and is configured to transmit and receive data via a communication cable or the like.

  The X-ray imaging apparatus body 1 includes an X-ray irradiation unit 110 that irradiates a subject (patient) with X-rays, an X-ray detection unit 120 that detects X-rays transmitted through the subject O, and an X-ray irradiation unit. 110 and the swivel arm 3 which has the X-ray detection part 120 facing each other.

  The panoramic imaging function performs tomographic imaging while the swivel arm is horizontally moved and swiveled so that the X-ray irradiation unit 110 and the X-ray detection unit 120 draw a predetermined locus along the shape of the dental arch.

  The X-ray imaging apparatus main body 1 includes a swivel arm 3 that supports an X-ray irradiation unit 110 and an X-ray detection unit 120 facing each other, and a subject holding means that holds the maxillofacial surface of the subject O (head fixing). Part) 4, a drive unit 160 for driving the swivel arm 3, and a photographing apparatus main body controller 170. An operation panel 71 a is added to the photographing apparatus main body control unit 170.

  The X-ray irradiation unit 110 includes an X-ray generator 112 including an X-ray tube that irradiates X-rays, and a collimator 111 including a slit or the like that controls the spread of the X-ray beam B, and detects X-rays. The unit 120 includes a cassette 122 provided with an X-ray detector 121 composed of a CCD sensor spread in two dimensions, an X-ray indirect conversion method (FPD: flat panel detector) sensor, or the like. The cassette 122 is detachable from the X-ray detection unit 120, but the X-ray detector 121 may be fixedly provided on the X-ray detection unit 120 without using the cassette 122. In addition, since this embodiment employs the tomosynthesis method, the X-ray detector 121 includes a plurality of X-ray detection elements also in the lateral (width) direction. The X-ray detector 121 collects incident X-rays as digital electric quantity image data corresponding to the amount of X-rays, for example, at a frame rate of 300 fps (one frame is, for example, 64 × 1500 pixels). Can do. Hereinafter, this collected data is referred to as “frame data”.

  The drive unit 160 aligns the pivot axis 3c of the pivot arm 3 with the center of the target imaging area (image reconstruction range) during CT imaging, or rotates the pivot axis along the dental arch during panoramic X-ray CT imaging. In order to move it, a turning axis position setting means 161 having an XY table for moving the turning axis in the XY direction (horizontal direction) is provided. The turning axis position setting means 161 includes an X-axis motor and a Y-axis motor for horizontally moving the turning axis 3c of the turning arm 3, and a turning motor for the turning axis rotating means 162 provided on the XY table for rotating the turning arm 3. And. First, the turning shaft 3c is set to coincide with the midline of the subject O.

  Further, the X-ray imaging apparatus main body 1 includes a turning arm position setting means 31 for moving the turning arm 3 straight in the horizontal direction. The revolving arm 3 is moved straight by the revolving arm position setting means 31 to change the distance between the X-ray irradiating unit 110 and the subject O and the distance between the X-ray detecting unit 120 and the subject O to obtain an image. The imaging area in one imaging can be increased in a state where the target image area (image reconstruction range) is enlarged and the X-ray detection unit 120 is brought close to the subject O greatly.

  At the time of imaging, the pair of the X-ray irradiation unit 110 and the X-ray detection unit 120 are positioned so as to face each other with the oral cavity of the subject O interposed therebetween, and each pair is rotated integrally around the oral cavity. Driven by. However, this rotation is not a rotation that draws a simple circle. That is, the pair of the X-ray generator 112 and the X-ray detector 121 has a mountain shape in which the rotation center RC of the pair is formed by connecting two arcs inside the substantially horseshoe-shaped dentition as shown in FIG. It is driven to rotate so as to draw a fixed trajectory. This fixed trajectory is pre-designed to focus on the X-ray focus and follow the 3D reference tomographic plane along the dentition of the standard shape and size of the oral cavity (hereinafter referred to as the 3D reference tomographic plane). Orbit. When making the X-ray focal point follow the 3D reference tomographic plane SS, the X-ray irradiation unit 110 and the X-ray detection unit 120 do not necessarily rotate at the same angular velocity when viewed from the 3D reference tomographic plane. That is, this rotation can be referred to as “movement along the dentition”, and is rotated while appropriately changing the angular velocity.

  The imaging apparatus main body control unit 170 includes a CPU 171 that executes various control programs including a control program that controls the drive unit unit 160, an X-ray generation unit control unit 172 that controls the X-ray irradiation unit 110, and an X-ray detection unit. X-ray detection unit control means 173 for controlling 120. The operation panel 71a is composed of a small liquid crystal panel and a plurality of operation buttons. In addition to the operation buttons, input means such as a keyboard, a mouse, and a touch panel can also be used. In addition, the operation panel 71a may include display means including a display such as a liquid crystal monitor.

  For example, information such as characters and images necessary for operating the X-ray imaging apparatus main body 1 may be displayed on the display means provided on the operation panel 71a. Further, the display content displayed on the display means 26 of the X-ray CT image display device 2 is also displayed on the display means when connected to the X-ray CT image display device 2 for displaying X-ray panoramic images and X-ray CT images. Alternatively, various commands may be issued to the X-ray imaging apparatus main body 1 through a pointer operation with a mouse or the like on characters or images displayed on the display means 26.

  The X-ray imaging apparatus main body 1 executes panoramic imaging of the dental arch in accordance with a command from the operation panel 71a or the X-ray CT image display apparatus 2. In addition, various commands, coordinate data, and the like are received from the X-ray CT image display device 2, while captured image data is sent to the X-ray CT image display device 2. Further, the base of the imaging region (imaging target region) rr is based on the lower edge line of the cone beam emitted from the X-ray irradiation unit 110.

  The X-ray CT image display device 2 connected to the X-ray imaging apparatus main body 1 is constituted by, for example, a personal computer or a workstation, and the display apparatus main body 20 is a display composed of a display device such as a liquid crystal monitor. Means 26 and operation means 25 constituted by a keyboard, a mouse and the like are added. A CT image or the like is displayed on the display means 26. Various commands can be given through a pointer operation with a mouse on characters or images displayed on the display means 26. Since the display means 26 can be constituted by a touch panel, the display means 26 also serves as the operation means 25 in this case.

  The operation unit 25 functions as a unit for designating a region of interest that is a dental cut-out region and a reference tomographic plane. The image display device main body 20 includes a control device (CPU) 21 that executes various programs, a hard disk, and the like, a storage unit 22 that stores various types of shooting data and images, and an image generation unit 23 that performs image reconstruction. It has. Here, the control device (CPU) 21, the storage means 22, and the image generation means 23 form an image processing means. The storage means 22 also stores dental arch orthographic information, which will be described later. The control device (CPU 21) controls various operations by the program stored in the storage unit 22, and operates to fulfill the function of the image generation unit 23 according to the program.

  The storage unit 22 can store panoramic imaging data obtained from panoramic imaging, a tomogram for tomosynthesis, and a tomographic image (reconstructed tomographic image) at an arbitrary tomographic position.

  Here, the display means 26 displays an image including characters and symbols. The display unit 26 displays a panoramic image representing a dental arch as a region of interest designating unit, and receives an operation for designating a region of interest that is a dental clipping region on the panoramic image, while also from a tomographic image (reconstructed tomographic image). A partial cross-sectional CT image (dental image) or the like of the region of interest that is a dental cutout region is displayed.

  FIG. 2 is a more specific front view of a sitting-type dental head and neck X-ray CT imaging apparatus, FIG. 3 is a side view, and FIG. 4 is a top view.

  The sitting-type X-ray imaging apparatus main body 1 is provided with upright columns 6 on both the left and right sides. The support 6 is supported by a base 5 installed on the floor. A support frame 7 is supported on the upper portion of the column 6, and a rotation drive unit 160 is provided in the central portion 70 of the support frame 7.

  Under the rotation drive unit 160, the turning arm 3 is supported so as to be able to turn, and an X-ray detection unit 120 and an X-ray irradiation unit 110 are provided on both sides of the turning arm 3. The X-ray imaging apparatus main body 1 includes a chair portion 40 for placing the subject O in a sitting position. Furthermore, the X-ray imaging apparatus main body 1 is provided with an electric actuator 40a for moving the chair portion 40 up and down. The chair portion 40 is moved up and down by the operation of the electric actuator 40a, and is positioned at the height of the imaging target region according to the individual difference of the subject O.

  The X-ray imaging apparatus main body 1 is provided with a frame 40b extending in the lateral direction at the lower portion of the chair portion 40, and an electric actuator 40c that can be expanded and contracted in the vertical direction is attached to the frame 40b. The X-ray imaging apparatus main body 1 has a head support unit 71 on the electric actuator 40c. The head support unit 71 can be turned in the horizontal direction and can be positioned and locked at the reference position so that the subject can easily go in and out of the chair portion 40. The head support unit 71 includes a head fixing portion 4 for fixing the subject's head and a pair of handles 71b for the subject O to grip.

  The head fixing unit 4 fixes the chin rest 4a for placing the chin of the subject O and the temporal region or the ear canal in order to stably fix the head of the subject O during imaging. Based on a three-point fixing system composed of a side head press or ear rod 4b that opens and closes symmetrically and a front head press (not shown) for supporting the front head, the back head is further moved to the front The belt is fixed to the part using a belt.

  Further, the X-ray imaging apparatus main body 1 includes an interference prevention mechanism 41 so that the bottom surface of the turning arm 3 and the upper part of the head fixing portion 4 do not interfere with each other. The interference prevention mechanism 41 includes a reflective beam sensor 41 a provided in the head support unit 71. Further, the interference prevention mechanism 41 includes a reflection plate 41 b at a predetermined height position of the support column 6. The reflection plate 41b is provided at a position facing the beam sensor 41a, and the beam emitted from the beam sensor 41a is reflected by the reflection plate 41b, and the beam sensor 41a detects that the electric actuators 40a and 40c are raised. It comes to stop. Thus, the head of the subject O is configured safely without interfering with the turning arm 3.

  The support frame 7 is provided with operation display means 42d and position beam means 42c. The operation display means 42d displays what operation is being performed by the operating device. The position beam means 42c irradiates the subject O with a weak laser beam to determine the range of the imaging target region (image reconstruction range) in the selected mode, and positions the subject O within the range. The electric actuators 40a and 40c can be operated.

  Further, the support frame 7 includes a midline laser beam 42a for confirming the midline position of the subject O. In addition, positioning laser beams 42 b are provided on both sides of the swing arm 3. The positioning laser beam 42b is directed in a single line on a straight line connecting the X-ray focal point 111a and a preset reference position 121b of the input surface 121a of the two-dimensional X-ray detector 121. . Further, a vertical axis that is orthogonal to a horizontal straight line connecting the X-ray focal point 111a and the reference position 121b set in advance on the input surface 121a of the two-dimensional X-ray detector 121 and passes through the center of the turning shaft 3c. Has come to be oriented. As a result, the positioning laser beam 42b indicates the center position of the subject imaging region (image reconstruction range) of the subject O and can be easily set.

  The rotary drive unit 160 includes a turning axis position setting means 161 and a turning axis rotation means 162, and is a hollow type high-accuracy positioning function by a direct drive system in which a load is directly connected to a motor without using a speed reducer. A motor having The turning shaft 3c is rotated by the rotation of the motor.

  The turning axis position setting unit 161 includes a Y table that moves in the Y direction and an X table that moves in the X direction on the Y table.

  The turning arm 3 includes turning arm position setting means 31. The turning arm position setting means 31 includes a turning table that can turn and a slide table that can move directly on the turning table. An interference prevention sensor (not shown) is provided on the bottom surface of the swivel arm 3 so that the bottom surface of the swivel arm 3 and the upper part of the head fixing portion 4 do not interfere with each other. When the upper part of the head fixing part 4 hits the interference prevention sensor, the electric actuators 40a and 40c are stopped from rising.

  The range shown by the two-dot chain line in FIG. 4 shows an example of the maximum turning radius when the center position of the turning shaft 3c of the turning arm 3 moves in a range that can move horizontally in the XY direction.

  The X-ray imaging apparatus main body 1 includes a collimator (mask) 111 for focusing X-rays emitted from the X-ray irradiation unit 2.

  In FIG. 2, the storage means 22 describes an external storage device, but the device main body 20 also includes a storage device. In the present invention, the storage means 22 is configured by an internal storage device and an external storage device, but the present invention is not limited to this, and any storage device can be used as long as it can store the various data described above.

  In the X-ray irradiation unit 110, the collimator 111 provided in front of the X-ray irradiation unit 110 is configured by a mask in which a plurality of slits having different shapes are formed, and one of the slits is selected and selected. The slit restricts the spread of the X-ray beam NB irradiated from the X-ray generator 112. In panoramic imaging, an opening for panorama is selected, and an X-ray slit beam corresponding to the shape is irradiated toward the X-ray detector 121 of the X-ray detector 120. Then, the swivel arm 3 is swung in this state, and the transmitted image projected on the detection surface of the X-ray detector 121 is accumulated as panoramic imaging data while scanning the maxillofacial surface with the X-ray slit beam. Shooting is executed.

  FIG. 5 shows a block diagram for control and processing of this X-ray panoramic CT imaging apparatus. As shown in the figure, data from the X-ray imaging apparatus main body 1 is given to the X-ray CT image display apparatus 2 via a communication line.

  The X-ray CT image display device 2 is configured by, for example, a personal computer or a workstation capable of storing a large amount of image data in order to handle a large amount of image data. That is, the main body of the X-ray image display apparatus 20 includes, as main components, interfaces 27 and 24, a storage unit 22, a control device 21, and an image generation unit 23 that are connected to each other via an internal bus 28. Is provided. The control device 21 includes a CPU 21a and a ROM 21b that stores a control program such as an OS. The storage unit 22 includes a buffer memory 22a, an image memory 22b, and a frame memory 22c. An operation unit 25 and a display unit 26 are connected to the control device 21 via an interface 24.

  The interface 27 is connected to the X-ray imaging apparatus main body 1 and mediates communication of control information and collected data exchanged between the control device 21 and the X-ray irradiation unit 110 and the X-ray detection unit 120. Accordingly, the control device 21 can transmit a panoramic image taken by the X-ray imaging apparatus main body 1 to an external server according to, for example, DICOM (Digital Imaging and Communications in Medicine) standard.

  The buffer memory 22 a temporarily stores the digital frame data received from the X-ray detection unit 120 via the interface 27.

  The image generation unit 23 is placed under the control of the control device 21 and performs processing for creating a panoramic image of a predetermined 3D reference tomographic plane provided by the device side and for subsequent use of the panoramic image with the operator. It has a function to execute interactively. A program for realizing this function is stored in advance in the ROM 21b. Therefore, the ROM 21b functions as a recording medium that stores the program according to the present invention. This program may be stored in the ROM 21b in advance. However, in some cases, the program may be installed on a recording medium such as a RAM (not shown) via a communication line or a portable memory from an external system. .

  In the present embodiment, the 3D reference tomographic plane SS described above is prepared in advance on the apparatus side, and can be calibrated before imaging or during maintenance inspection. Note that the 3D reference tomographic plane SS may be selected from a plurality of tomographic planes. With this selection operation, the position of the 3D reference tomographic plane can be changed within a certain range in the depth (front-rear) direction of the dentition.

  Frame data and image data processed by the image generating means 23 or being processed are stored in the image memory 22b so as to be readable and writable. For the image memory 22b, a large-capacity recording medium (nonvolatile and readable / writable) such as a hard disk is used. The frame memory 22c is used for displaying reconstructed panoramic image data, post-processed panoramic image data, and the like. The image data stored in the frame memory 22 c is given to the display means 26 via the interface 24 and displayed on the screen of the display means 26.

  The CPU 21a of the control device 21 controls the overall operation of the components of the device in accordance with a program responsible for overall control and processing stored in the ROM 21b. Such a program is set so as to interactively receive operation information for each control item from the operator. Therefore, the CPU 21a is configured to be able to execute collection (scanning) of frame data and the like, as will be described later.

  Therefore, as shown in FIGS. 2 and 3, the subject O places his / her chin at the position of the chin rest 4a in the sitting position and presses the forehead against the headrest. As a result, the position of the patient's head (jaw) is fixed at substantially the center of the rotation space of the swivel arm 3. In this state, the turning arm 3 rotates around the head of the subject O along the XY plane. 2 and 3 exemplify the case of the sitting position, but it is needless to say that a standing apparatus is naturally possible although not shown.

  During this rotation, pulsed X-rays are emitted from the X-ray irradiation unit 110 at a predetermined cycle. The X-rays pass through the jaw (dentation portion) of the subject O located at the imaging position and enter the X-ray detection unit 120. As described above, the X-ray detection unit 120 detects incident X-rays at a very high frame rate (for example, 300 fps), and frames corresponding two-dimensional digital data (for example, 64 × 1500 pixels). Output sequentially in units. This frame data is temporarily stored in the buffer memory 22a via the interface 27 of the X-ray CT image display device 2 via the communication line. The temporarily stored frame data is then transferred and stored in the image memory 22b.

  Therefore, the image generation unit 23 reconstructs (creates) a tomographic image focused on the 3D reference tomographic plane SS as a panoramic image (reference panoramic image) using the frame data stored in the image memory 22b. That is, this reference panoramic image is defined as “a panoramic image when it is assumed that a dentition is present along the 3D reference tomographic plane SS”. Further, the image generation unit 23 performs processing such as creating a three-dimensional (3D) image using the reference panoramic image. When the reference panoramic image is deviated from the actual dental arch, the corrected reference plane image is obtained by shifting the reference plane back and forth. The corrected reference plane image is a surface image in which the dentition is optimally focused using frame data or reference panoramic image data from the 3D reference image. That is, the corrected reference plane image shifted by the user using the operation means 25 before and after this is an optimally focused image that is less blurred and accurately represents the actual position and actual size of the dentition.

  In particular, the corrected reference plane image is an image that takes into account the fact that it is mostly different for each subject. As a practical matter, the dentition of each subject is not along the 3D reference tomographic plane SS, and may be partially or entirely offset from the 3D reference tomographic plane SS.

  X-rays irradiated from the X-ray irradiation unit 110 pass through the oral cavity of the subject O and are detected by the vertically long X-ray detection unit 120 having a certain length in the Z-axis direction. The distance between the X-ray irradiation unit 110 and the X-ray detection unit 120 is kept constant, and the distance from the rotation center to the X-ray irradiation unit 110 and the X-ray detection unit 120 is also kept constant. On the other hand, in order to perform a scan focused on the 3D reference tomographic plane SS, during one scan (data collection), the trajectory at the position of the rotation center RC changes to a dentition curved in a horseshoe shape. On the other hand, it is designed to change to a mountain shape as described above as an example.

  A conventional panoramic image is created without considering the actual shift of the dentition. For this reason, quantitative structural analysis from conventional panoramic images is extremely difficult, and a panoramic imaging device capable of capturing images with high accuracy regardless of the dentitions in various shapes and positions for each subject is desired. It was.

  In this embodiment, a tomosynthesis method (tomosynthesis) is used to obtain an image of a tomographic plane. In the tomosynthesis method, X-rays are irradiated from the X-ray irradiation unit 110 to the subject O at a plurality of different angles, and the X-rays that have passed through the subject are detected by the X-ray detection unit 120. Take an image of (tomosynthesis image). The plurality of tomosynthesis captured images are reconstructed to obtain captured images (reconstructed tomographic images) at arbitrary tomographic positions.

  As a reconstruction method of a plurality of tomosynthesis tomographic image data, there are a shift addition method and a filtered back projection method (FBP method, FBP: Filtered Back Projection). Since the shift addition method and the FBP method have different reconstruction principles, the resolution and contrast in the tomographic direction are different. For this reason, each reconstruction method has the following advantages.

  First, the advantages of the shift addition method will be described. When the shift addition method is used, metal artifacts do not occur, and it becomes easy to diagnose how the bone is attached to the implant body. In addition, caries near the inlay and crown can be easily diagnosed. Furthermore, reconstruction calculation is fast, and it is possible to quickly display an image after diagnosis and make a diagnosis. In addition, there is little noise, and it becomes easy to make a diagnosis even in a portion where the dose is slightly short, such as a median portion or a temporomandibular joint portion.

  The advantages of the FBP method will be described. When the FBP method is used, a high-contrast image can be created, and it becomes easy to diagnose the apex, root canal, periodontal ligament and the like. Furthermore, when a dental image is cut out from a panoramic image, tooth overlap can be eliminated mainly at the molar portion, and it becomes easy to diagnose caries and the like. Further, by creating a plurality of panoramic images in the depth direction and creating volume data, it is possible to create a dentition crossing image.

  Thus, the shift addition method and the FBP method have their respective advantages, and it cannot be said that any reconstruction method is absolutely superior. Therefore, a reconstruction method that satisfies each requirement may be used, but a shift addition method is generally used in the tomosynthesis imaging method of a dental panoramic X-ray apparatus.

  In this embodiment, a tomosynthesis method (tomosynthesis) is used to obtain an image of a tomographic plane. The shift addition method as a reconstruction method is a plurality of frame data determined for each position of a locus projected on the XY plane of a three-dimensional 3D reference tomographic plane out of frame data (pixel data) collected at a constant rate by scanning. For example, a process of mutually shifting and shifting each other by an amount corresponding to the position is used.

  In the FBP method as a reconstruction method, a group of frame data (image data) is individually subjected to a predetermined first weighting process, and then each image data after the first weighting process is subjected to a predetermined weighting process. Perform convolution processing. Next, a predetermined second weighting process is performed on each projection data after the convolution process. Next, the image data after the second weighting process is individually subjected to a predetermined back projection (back projection: BP) process to generate a BP image (three-dimensional volume data).

  The “optimal focus” in the present embodiment means “the focus is best, and there is little out-of-focus blur”, and the resolution of the part of interest is better than other parts, or the entire image Say that the resolution is higher.

  When the reference panoramic image is created, the data is stored in the image memory 22b and displayed on the display means 26 in an appropriate manner. Among these, the user's intention given from the operation means 25 is reflected in the display mode and the like.

  In the present embodiment, a plurality of depth direction panoramic images are created. That is, as shown in FIG. 8, a plurality of panoramic images are stored in the image memory 22b according to tomographic information in the D direction, for example, 27 mm, back and forth along the trajectory of the 3D reference cross section.

  On the display screen 26a of the display means 26, a panoramic image along the trajectory of the 3D reference cross section is displayed. If the user determines that the image is not in focus by looking at the image of the cutout panoramic image display unit 261 on the displayed display screen 26a, the slice position 276 is slid left and right to correct the reference plane. Adjustments are made. As described above, since a plurality of panoramic images in the depth direction are stored in the image memory 22b, the correction reference plane is set when the panoramic image is sequentially changed according to the slice position 276 and the focus is best. .

  As described above, the tomographic information of D can flexibly cope with individual differences and misalignment of the dentition.

  As shown in FIGS. 9 and 10, the panoramic image with the best focus is displayed on the display screen 26 a. When the save button 273 is clicked, the panoramic image is stored as DICM data in the image memory 22b or the like. FIG. 9 shows a screen for the dental cut-out operation, and FIG. 10 shows an image storage screen. In the image storage screen, a frame 275 indicating a shooting mode, a frame 277 indicating image editing, and a slice position 276 for changing the depth direction of the reference plane are provided.

  By the way, in this embodiment, the partial cross-sectional image (dental image) of the optimal focus of each of the some partial area | region of the image is produced | generated from the data of the panoramic image of the desired cross section of a target object. For this reason, as shown in FIG. 9, a desired partial region (dental) is designated from a panoramic image of a desired cross section so that dental clipping can be performed.

  The cutout panoramic image display unit 261 displays a dental cutout image frame 263 that is a partial area (region of interest). The image frame 263 is moved to a desired area of the dental image. That is, the display frame 263 can be moved by dragging the image frame 263 and moving it. The image displayed in the image frame 263 is displayed in the cut-out dental image display unit 264. Since the image displayed in the dental cutout image frame 263 serves as a reference for the cutout position, the state edited by the cutout dental image display unit 264 is not reflected on this screen.

  By dropping the image display frame 263, the image at that position is cut out and re-displayed on the dental image display unit 264. At that time, all the states edited by the cut-out dental image display unit 264 are returned to the initial state.

  Further, by displaying a cross cursor in the dental cutout image frame 263 and rotating the cursor while dragging, the image displayed in the cutout dental image display unit 264 is also rotated around the center of the frame and displayed. Configured as follows.

  In the present embodiment, the size of the dental cutout image frame 263 is 4 cm long and 3 cm short.

  The up / down / left / right rotation angle change button / angle reset button 265 changes and resets the angle of the extracted dental image. Click the up / down / left / right buttons to adjust the angle of the extracted dental image. The image of the rotation angle changed for each click is recreated and displayed on the cut-out dental image display unit 264. Clicking the reset button returns the display to the initial display up / down / left / right rotation. The depth adjustment button and the depth reset button 262 are for adjusting and resetting the cut-out dental image in the depth direction.

  The template display unit 268 displays a registration template. When the frame in the template display portion 268 is selected, right-clicking on the image displays deletion in the right-click menu. When the dental cutout image frame 263 is selected, the right-click menu is not displayed.

  The cutout position change button 266 changes the dental cutout position, and the width of movement is changed depending on the selected template. The order of movement is the order of upper right 8th, upper left 8th, lower right 8th, lower left 8th.

  The depth adjustment button 262 adjusts the depth of the tomographic position, and is adjusted forward and backward by clicking the upper and lower buttons. The image of the rotation angle changed for each click is displayed on the cut-out dental image display unit 264. Click the reset button to return to the initial displayed fault position.

  The dental image switching button 267 switches an image registered in one frame on the template.

  When switched, the angle of the dental cutout image frame 263 is displayed again in a state corresponding to the image. It is invalidated when creating a new image.

  A template selection button 269 selects a template desired by the user from the 10-sheet method, the 14-sheet method, and three individual patterns. The selected template is displayed on the template display unit 268.

  The tooth number change button 270 changes the registered tooth number. The image processing unit 271 clicks each icon when changing the image processing to the currently displayed dental image. Image processing is held for each cut out dental image. The save button 272 saves the image currently recorded in the template in the image memory 22b or an external storage device. In the case of the 10-sheet method or the 14-sheet method, the image displayed on the template is registered in the album. In the case of individual, album registration is not performed.

  The close button 273 ends the dental cut-out mode by clicking this button. When at least one image has been registered in the template, a confirmation message asking whether to discard the image is displayed. When yes is selected, everything is discarded, and when no is selected, the screen is returned to the dental cutout screen.

(Image processing)
Processing executed by the control device 21 and the image generation unit 23 will be described with reference to the flowchart of FIG. As described above, this processing includes data collection by scanning, reconstruction of a reference panorama image as pre-processing, display according to various aspects using the reference panorama image, and the like.

(Data collection and reconstruction of standard panoramic images)
First, when the preparation for imaging such as positioning of the subject O is completed, the control device 21 responds to the operator's instruction given through the operation means 25 and commands a scan for data collection (step S1). . Thereby, the turning arm 3 and the X-ray irradiation unit 110 are instructed to be driven along a preset control sequence. Therefore, while rotating the pair of the X-ray irradiation unit 110 and the X-ray detection unit 120 around the jaw of the subject O, the pulsed or continuous wave of the X-ray irradiation unit 110 is rotated during the rotation operation. X-rays are exposed at a predetermined cycle or continuously. At this time, the pair of the X-ray irradiation unit 110 and the X-ray detection unit 120 is rotationally driven based on a driving condition set in advance so as to focus the 3D reference tomographic plane SS (see FIG. 7). As a result, the X-rays exposed from the X-ray detection unit 110 pass through the subject O and are detected by the X-ray detection unit 120. Therefore, as described above, digital amount frame data (pixel data) reflecting the amount of X-ray transmission is output from the X-ray detector 121 at a rate of, for example, 300 fps. This frame data is temporarily stored in the buffer memory 22a.

  When this scan command is completed, the processing instruction is transferred to the image generation means 23. Based on the tomosynthesis method corresponding to the spatial position of the 3D reference tomographic plane SS, the image generation means 23 uses the shift conversion method or the FBP method to obtain a depth of front and rear D around the 3D reference tomographic plane SS as shown in FIG. A plurality of panoramic images are created in the direction, and each pixel value of the reconstructed image is stored (step S2). In this reconstruction process, a process of multiplying a coefficient so that the ratio of the vertical and horizontal enlargement ratios is the same at the center of the front tooth portion is also executed.

  Next, the image generation means 23 displays this reference panoramic image on the display screen 26a of the display means 26 (step S3). Examples of this reference panoramic image are schematically shown in FIGS.

(Identification of optimal focus cross-sectional position)
On the other hand, when it is determined that the process of obtaining the corrected reference plane image by shifting the reference plane back and forth (YES in step S4), the reference panoramic image is shifted from the actual dental arch in step S5. First, a corrected reference plane image is obtained by shifting the reference plane back and forth.

  The image generating unit 23 displays the reference image moved before and after the image on the display unit 26 for reference by the operator.

  Thereafter, the image generation means 23 gives the operator an opportunity to observe the corrected reference plane image in another manner. That is, the image generation means 23 determines whether or not to display the corrected reference plane image in another manner based on operation information from the operator.

  As an example, the image generation unit 23 determines whether or not to observe a dental cutout image (partial region) of the corrected reference plane image (three-dimensional panoramic image) (step S6). If the determination in step S6 is YES, the image generation means 23 determines whether or not to set a dental clipping frame in the correction reference screen image based on the operation information of the operator (step S7). Next, when the determination in step S7 is YES, the image generation unit 23 cuts out the partial image of the partial area set based on the operation information of the operator (step S8), and displays the partial image in an enlarged manner, for example. (Step S9). For example, as shown in FIG. 9, this partial image is displayed on the cut-out dental image display unit 264.

  Thereafter, the image generation unit 23 determines whether or not to end the series of processes from the operation information (step S10). If this determination is YES, the process ends. On the other hand, if NO, the process returns to step S6 and the above-described process is repeated.

  As described above, according to the present embodiment, the projection direction can be expressed three-dimensionally by grasping the panoramic imaging space three-dimensionally. Therefore, as long as the panoramic image is in focus, the three-dimensionally expressed image is not distorted and an accurate panoramic image can be constructed. As a result, the panoramic image can be displayed more stably regardless of whether the positioning is good or not, and a clear image can be created with the entire panoramic image.

  In this embodiment, a tomosynthesis method (tomosynthesis) is used to obtain an image of a tomographic plane. As the reconstruction method, the shift addition method or the FBP method is used. As described above, since the shift addition method and the FBP method have different reconstruction principles, the resolution and contrast in the tomographic direction are different. For this reason, there are reconstruction methods suitable for the purpose of diagnosis. First, a preferred example will be described in which either the shift addition method or the FBP method is used by using a tomosynthesis method (tomosynthesis) to obtain an image of a tomographic plane.

  When CT imaging is performed, artifacts are generated around the implant body, which makes it difficult to understand how bones are attached. Therefore, CT imaging by the tomosynthesis method is performed, and a tomographic image of the implant body part is created by using the shift addition method or the FBP method for a desired dental region using a part of the projection data of the CT imaging, thereby artifacts around the implant body. Will not occur, and you can see how the bones are attached.

  Next, an example of panorama reconstruction formation by the FBP method will be described with reference to the flowchart of FIG.

  First, the defect registration data is read and a defect table is created (step S21). Then, the selected trajectory data is read (step S22).

  Next, a black and white inversion lookup table is created (step S23). Subsequently, the density correction image is read and density correction data is created (step S24).

  Then, panorama shooting is performed (step S25), and a panorama projection image is read (step S26). The projection image is read and defect correction, density bridge correction, and black / white reversal are performed on the projection image (step S27).

  Subsequently, in order to shorten the calculation time, a dentition direction calculation range table that specifies a range of voxels through which X-rays incident on the X-ray detector 121 pass in each trajectory is created (step S28).

  Thereafter, a table used for correcting the dentition position of each slice in step S39 described later is created. That is, a table for determining a ratio of height to a table for designating a voxel through which X-rays incident on the center of the X-ray detector 121 are transmitted in each trajectory is created (step S29).

  Next, the actual position coordinates of each voxel vertex occupying the reconstruction area are calculated (step S30).

  The trajectory data (arm angle and suspension axis position) and the projection data after processing are read (step S31). Convolution integration is performed on the projection data (step S32).

  In order to simplify the calculation, the rotational movement and the parallel movement are performed so that the X-ray source is the origin and the center position of the X-ray detector 121 is in the + y direction on the y-axis (step S33).

  Then, a detector pixel on which X-rays that pass through each voxel enter is calculated (step S34). The product of the contribution of each detector pixel to the voxel and the pixel value is calculated and returned to the voxel to perform reconstruction calculation, FBP method, and sum (step S34). It is determined whether or not the trajectory data is finished (step S35). If it is not finished, the process returns to step S31 and the above-described operation is repeated.

  On the other hand, since the number (n) of transmission of X-rays through each voxel varies depending on the trajectory, the number is calculated in the calculation process, and the final result is divided by n (steps S36 and S37).

  In the image after the reconstruction calculation, the dentition of the inner slice is enlarged / reduced in the left / right and up / down directions, and is corrected (step S39). Thereafter, the reconstructed image is displayed on the display means 26.

  As described above, when the shift addition method is used, metal artifacts do not occur, so that it is easy to diagnose how the bone is attached to the implant body. In addition, caries near the inlay and crown can be easily diagnosed. Furthermore, reconstruction calculation is fast, and it is possible to quickly display an image after diagnosis and make a diagnosis. In addition, there is little noise, and it becomes easy to make a diagnosis even in a portion where the dose is slightly short, such as a median portion or a temporomandibular joint portion. On the other hand, when the FBP method is used, a high-contrast image can be created, and it becomes easy to diagnose the apex, root canal, periodontal ligament and the like. Furthermore, when a dental image is cut out from a panoramic image, tooth overlap can be eliminated mainly at the molar portion, and it becomes easy to diagnose caries and the like.

  In view of the above circumstances, FIG. 6 shows an embodiment in which the user can select whether to perform reconstruction by the shift addition method or the FBP method at the time of tomosynthesis imaging. The image processing unit 20 a performs predetermined processing on the data of the tomosynthesis captured image and outputs the processed data to the display unit 26. The image processing unit 20a includes a first memory 22d, a second memory 22e, a shift addition processing unit 23a, a third memory 22f, an FBP processing unit 23b, and a display control unit 23c.

  The first memory 22d stores data of a tomosynthesis captured image obtained by tomosynthesis imaging. The shift addition processing unit 23a reconstructs the data of the tomosynthesis captured image by the shift addition method, and outputs the data of the shift addition image. The second memory 22e stores the data of the shift addition image output from the shift addition processing unit 23a. The FBP processing unit 23b reconstructs the tomosynthesis captured image data by the FBP method, and outputs the FBP image data. The third memory 22f stores FBP image data output from the FBP processing unit 23b. The display control unit 23c processes the shift addition image data stored in the second memory 22e and the FBP image data stored in the third memory 22f, and performs display control of the shift addition image or the FBP image. .

  Next, a method for performing tomosynthesis imaging using this embodiment will be described. FIG. 13 shows a flowchart of the method.

  In step S51, it is determined whether there is a request for tomosynthesis imaging from the user to the input unit 22. If there is no request for tomosynthesis imaging (S51: No), the imaging control unit continues the process of step S51. When there is a request for tomosynthesis imaging (S51: Yes), in step S52, the imaging control unit starts tomosynthesis imaging. The swivel arm 3 is operated to rotate the X-ray irradiation unit 110 and the X-ray detection unit 120 with the subject O interposed therebetween, and output X-rays from the X-ray irradiation unit 110 and pass through the subject O. The detected X-rays are detected by the X-ray detection unit 120 and converted into X-ray image information (tomosynthesis captured image data).

  When the tomosynthesis imaging is completed, in step S3, the image processing unit 20a of the control device 20 displays at least one of the shift addition image or the FBP image on the display unit 26 according to the display setting set in advance.

  FIG. 14 shows a flowchart of processing in the image processing unit 20a in the present embodiment. In the present embodiment, display settings include display image type, display format, display magnification, display target area, and image correction processing. These display settings can be selected before tomosynthesis imaging and can be changed during tomosynthesis imaging or after tomosynthesis imaging.

  In step S61, the image processing unit 20a specifies the display image type. The display image type indicates an image displayed on the screen of the display unit 26, and at least one of the shift addition image and the FBP image is selected as the display image type. That is, any one or all of the shift addition image and the FBP image are selected. As a specific process, an image corresponding to the setting of the display image type is output to the display control unit 23c. That is, when the shift addition image is selected, the shift addition processing unit 23a reads the data of the tomosynthesis captured image from the first memory 22d and reconstructs the data to obtain the data of the shift addition image. The data of the shift addition image is temporarily stored in the second memory 22e and then output to the display control unit 23c. When the FBP image is selected, the FBP processing unit 23b reads the data of the tomosynthesis captured image from the first memory 22d, and reconstructs the data to obtain the FBP image data. The FBP image data is temporarily stored in the third memory 22f and then output to the display control unit 23c.

  In step S62, the image processing unit 20a specifies the display format. As the display format, parallel image display and frame display can be selected. The parallel image display is a display format in which two images are displayed in parallel. In the case of parallel image display in which two images are displayed in parallel, it is possible to select which image is to be displayed and its position.

  In step S63, the display control unit 62 specifies the display magnification. The display magnification indicates which range of each image is displayed in the image display area, that is, the display magnification of each image on the screen of the display means 26. The display magnification is defined by defining the vertical and horizontal lengths (dots) of each image displayed in the image display area of the display means 26.

  In step S64, the display control unit 23c specifies a display target area. The display target area is set, for example, which area to display among all the areas of each image. The display target area is defined by the coordinates of each pixel included in the display target area or the coordinates of specific pixels (for example, pixels at the four corners of the display target area).

  In step S65, the display control unit 23c performs image correction processing. Image correction processing includes processing such as gain adjustment (sensitivity correction), offset adjustment (gradation correction), edge enhancement (frequency enhancement), and inversion (reversal of light and shade). When data of a plurality of images is input to the display control unit 23c, the display control unit 23c performs image correction processing for each image. For example, it is possible to perform gain adjustment on a simple X-ray image and edge enhancement on an FBP image.

  In step S66, the display control unit 62 outputs a signal (image signal Si) indicating the image (image display area) generated as a result of the processing in steps S61 to S65 to the display unit 26. The display means 26 that has received this image signal displays an image corresponding to the image signal i.

  As described above, in this embodiment, a shift addition image or an FBP image can be displayed. Thereby, since the user can see both the shift addition image and the FBP image, the diagnosis can be performed efficiently.

  In the above-described embodiment, a configuration capable of displaying three images, that is, a simple X-ray image, a shift addition image, and an FBP image is shown. However, the present invention is not limited to this, and the present invention can be applied to a configuration capable of displaying only two of them. is there. Further, the present invention may be applied to a configuration that displays an image other than the three images.

  In the above embodiment, three memories (the first memory 22d, the second memory 22e, and the third memory 22f) are shown. However, they need not be separate memories, and may be separate memory areas in one memory. Good.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The above-described embodiment shows an example in which panoramic imaging is performed by a tomosynthesis method using a dental X-ray imaging apparatus. Alternatively, the tomosynthesis method can also be used. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

DESCRIPTION OF SYMBOLS 1 X-ray imaging apparatus main body 2 X-ray CT image display apparatus 3 Turning arm 110 X-ray irradiation part 120 X-ray detection part 20 Image display apparatus main body 21 CPU
22 storage means 25 operation means 26 display means

Claims (7)

An X-ray irradiation unit for irradiating the subject with X-rays;
An X-ray detector that outputs a digital amount of an electrical signal corresponding to incident X-rays at a constant frame rate;
Swiveling means for moving the pair of the X-ray irradiation unit and the X-ray detection unit around the subject in a state of facing each other across the subject;
Storage means for sequentially storing tomosynthesis tomographic image signals output by the detection unit as frame data as the turning unit moves the X-ray irradiation unit and the X-ray detection unit around the subject;
A dental X-ray imaging apparatus comprising: image processing means for obtaining a panoramic image by performing image reconstruction calculation based on the frame data stored in the storage means.   The dental X-ray imaging apparatus is a dental panoramic X-ray imaging apparatus or a dental head and neck X-ray CT imaging apparatus.   The dental X-ray imaging apparatus according to claim 1, wherein the image processing unit reconstructs a plurality of panoramic images in a depth direction across a reference cross section.   The dental X-ray imaging apparatus according to claim 3, wherein the image processing unit adjusts a focal point by sliding a reference cross section in a depth direction.   5. The image processing unit generates a partial cross-sectional image having an optimum focus corresponding to a position of a specified partial region in the panoramic image of the desired tomographic plane from the panoramic image data. The dental X-ray imaging apparatus described in 1.   The dental X-ray imaging according to any one of claims 1 to 5, wherein the image processing means reconstructs a tomosynthesis tomographic image using a filtered back projection method (FBP method). apparatus.   The image processing means reconstructs a tomosynthesis tomographic image using a shift addition method, and the image processing means reconstructs a tomosynthesis tomographic image using a filter back projection method (FBP method). The dental X-ray imaging apparatus according to claim 1, further comprising: an FBP processing unit configured to display a shift addition image or an FBP image on the display unit.

Images