JP4806433B2 - X-ray imaging apparatus and signal processing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus capable of generating high resolution images at low cost. <P>SOLUTION: A digital panorama imaging apparatus 1 includes a revolving driving means 5 for removing an X-ray imaging means 3 having pixels receiving the X-ray passing through an object in an direction perpendicular to an X-ray incident direction, a large capacity processing image storing means 8 having a plurality of memory regions corresponding to divisions thinner than the width of the pixels for respective pixels, and an image signal processing means 10 proportionally dividing the output signal value of the first pixel according to the position of the first pixel during moving, integrating the same in the respective memories for the first pixel, proportionally dividing the output signal value of the second pixel according to the position of the second pixel receiving the X-ray next to the first image, during moving, integrating the output signal value of the second pixel in the respective memory regions for the first image to generate a processed image within a time when the first pixel of the X-ray imaging means 3 moves only a pixel width, wherein the X-ray imaging means 3 is arranged such that the lateral and longitudinal arranging direction of the plurality of pixels are inclined from the moving direction of the X-ray imaging means 3 respectively. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an X-ray imaging apparatus and a signal processing method thereof, and more particularly, to an X-ray imaging apparatus and a signal processing method thereof for improving the resolution of tomographic images taken for general medical use and dental use.

2. Description of the Related Art Conventionally, as a dental X-ray tomography apparatus, a panorama imaging apparatus in which a rotation operation and a slide operation are combined is known (see, for example, Patent Document 1 and Patent Document 2). The devices disclosed in Patent Document 1 and Patent Document 2 acquire a tomographic image in the vertical plane direction (Z direction) of the dentition at the position of the dentition aligned on the horizontal plane (XY plane).
JP-A-10-2111200 (0033-0040, FIG. 4) Japanese Utility Model Publication No. 4-48169 (pages 3 to 4 and FIG. 4)

  A tomographic image (panoramic tomographic image) is an image generated by superimposing frame images corresponding to a plurality of simple X-ray images captured while the X-ray imaging unit rotates and slides. The resolution of the tomographic image is determined by the pixel size of the captured frame image. That is, the resolution decreases as the pixel size of the frame image increases. In general, since the pixel size of a digital image recording system is larger than that of an analog system, a digital panoramic tomographic image tends to be unclear. Therefore, it is desired to generate a clearer image. In order to realize high resolution, X-ray imaging means having a pixel size as small as an analog system is necessary. However, it is technically difficult to develop an X-ray imaging unit having such a small pixel size at present, and even if it is developed, it is expensive.

  Accordingly, an object of the present invention is to provide an X-ray imaging apparatus and a signal processing method thereof that can solve the above-described problems and can generate a high-resolution image at low cost.

In order to solve the above problem, an X-ray imaging apparatus according to claim 1, wherein an X-ray source that irradiates a subject with X-rays and a plurality of pixels that receive X-rays that have passed through a predetermined point of the subject are light receiving surfaces. X-ray imaging means arranged two-dimensionally along one axis and the other axis orthogonal to each other above, driving means for moving the X-ray imaging means in a direction perpendicular to the X-ray incident direction, and the X-ray An X-ray imaging apparatus comprising: an image signal processing unit that generates a processed image by processing a signal output from an imaging unit; and a processed image storage unit that stores a processed image generated as the signal processing result. The X-ray imaging means is disposed on the light receiving surface by inclining the arrangement direction of the plurality of pixels along the one axis and the other axis from the moving direction of the X-ray imaging means, The processed image storage means is A plurality of memory areas corresponding to areas obtained by dividing an element finer than a pixel width for each of the pixels, and the image signal processing unit is configured to perform predetermined pixels of the X-ray imaging unit as the X-ray imaging unit moves. In the time during which the pixel moves along the one axis by the pixel width, the value of the signal output from the predetermined pixel is prorated according to the position of the predetermined pixel that is moving along the one axis. The X-rays passing through the predetermined point of the subject along the one axis and the second pixel receiving the next to the predetermined pixel along the one axis. the value of the signal output from the adjacent pixels along the one axis prorated according to the position in the movement along said one axis of the adjacent pixels adjacent to the memory area for the given pixel Te integrated with, and movement of the X-ray imaging means Along with the other axis of the predetermined pixel, the value of the signal output from the predetermined pixel within the time during which the predetermined pixel of the X-ray imaging means moves along the other axis by the pixel width. The X-ray passing through a predetermined point of the subject is received next to the predetermined pixel along the other axis while being apportioned according to the moving position and accumulated in each memory area for the predetermined pixel. A value of a signal output from an adjacent pixel along the other axis in proportion to a position of the adjacent pixel adjacent to the predetermined pixel along the other axis during movement along the other axis Is accumulated in each memory area for the predetermined pixel to generate the processed image.

According to a fourth aspect of the present invention, there is provided a signal processing method in which an X-ray source that irradiates a subject with X-rays and a plurality of pixels that receive X-rays that have passed through a predetermined point of the subject are orthogonal to each other on a light receiving surface. Output from the X-ray imaging means, an X-ray imaging means arranged two-dimensionally along the other axis, a driving means for moving the X-ray imaging means in a direction orthogonal to the X-ray incident direction, and the X-ray imaging means A signal processing method in an X-ray imaging apparatus, comprising: an image signal processing unit that generates a processed image by processing a signal; and a processed image storage unit that stores a processed image generated as the signal processing result, X-ray imaging means is disposed on the light receiving surface by inclining the arrangement direction of the plurality of pixels along the one axis and the other axis from the moving direction of the X-ray imaging means, The image storage means is Each of the pixels has a plurality of memory areas corresponding to areas obtained by dividing the pixels more finely than the pixel width, and the predetermined signal of the X-ray imaging unit is moved by the image signal processing unit according to the movement of the X-ray imaging unit. In the time during which the pixel moves along the one axis by the pixel width, the value of the signal output from the predetermined pixel is prorated according to the position of the predetermined pixel that is moving along the one axis. The X-rays passing through the predetermined point of the subject along the one axis and the second pixel receiving the next to the predetermined pixel along the one axis. the value of the signal output from the adjacent pixels along the one axis prorated according to the position in the movement along said one axis of the adjacent pixels adjacent to the memory area for the given pixel Te integrated with, and the X-ray imaging hands The value of the signal output from the predetermined pixel is converted to the other axis of the predetermined pixel within a time during which the predetermined pixel of the X-ray imaging unit moves along the other axis by the pixel width as the movement of the predetermined pixel. According to the moving position along the line, and accumulating in each memory area for the predetermined pixel, and the X-ray passing through the predetermined point of the subject is next to the predetermined pixel along the other axis. The adjacent pixel that is adjacent to the predetermined pixel that receives light at the other axis along the other axis is divided according to the moving position along the other axis, and is output from the adjacent pixel along the other axis. The processed image is generated by integrating signal values in each memory area for the predetermined pixel .

  According to the X-ray imaging apparatus having such a configuration and the signal processing method thereof, the X-ray imaging apparatus has a plurality of memories corresponding to a region obtained by dividing the pixels included in the X-ray imaging unit finer than the pixel width in the processed image storage unit. Each pixel has a region, and the image signal processing means outputs a value of a signal output from a predetermined pixel that receives X-rays passing through a predetermined point of the subject and a signal output from an adjacent pixel that receives light next Are proportionally distributed according to the position of each pixel and integrated in each memory area for a predetermined pixel. After a predetermined pixel has moved by a predetermined pixel width, the adjacent pixel moves as a new predetermined pixel while receiving X-rays passing through a predetermined point of the subject in the same manner as the original predetermined pixel. It will be. However, the value of the signal output from the new predetermined pixel and the value of the signal output from the new adjacent pixel are accumulated in each memory area for the new predetermined pixel. The same applies hereinafter.

  Therefore, in the X-ray imaging apparatus and the signal processing method thereof configured as described above, in the processed image storage means, the signal accumulated in each memory area for each pixel has an X-ray intensity signal waveform obtained from a predetermined point of the subject as a triangular wave. It becomes. The length of the base of the sawtooth waveform obtained by cutting this triangular wave along a line-symmetric axis is the pixel width. On the other hand, if the X-ray intensity signal is not accumulated in each memory area, the X-ray intensity signal obtained from a predetermined point of the subject has a rectangular waveform for the output signal of each pixel or the signal accumulated according to the elapsed time. . The length of this rectangle is the pixel width. Since the resolving power is obtained from the reciprocal of the waveform period, the spatial frequency of the sawtooth waveform is twice the spatial frequency of the rectangular waveform. In general, when the LSF is a triangular wave, the cutoff frequency value is higher in the spectral region than when the LSF (Line Spread Function) is a rectangular wave. That is, it is known that the resolution is increased. Here, in the X-ray imaging apparatus, if the X-ray imaging unit matches the arrangement direction of the pixels with the movement direction on the light receiving surface, the horizontal direction (one axial direction) or the vertical direction indicating the movement direction. The resolution in the other axial direction will be improved. However, in the present invention, the X-ray imaging means is disposed on the light receiving surface by inclining the arrangement direction of the plurality of pixels along one axis and the other axis from the moving direction of the X-ray imaging means. Therefore, the direction in which the resolution is improved is two directions of the horizontal direction (one axial direction) and the vertical direction (the other axial direction). Therefore, according to the X-ray imaging apparatus and the signal processing method having such a configuration, it is possible to generate a high-resolution image in the horizontal direction and the vertical direction without changing the X-ray imaging unit to a high-resolution one.

  The X-ray imaging apparatus according to claim 2 is the X-ray imaging apparatus according to claim 1, wherein the subject is placed on the X-ray imaging unit side and the X-ray source side with the subject interposed therebetween. Each of the slits for narrowing X-rays to be irradiated is provided, and at least the direction of the slit on the X-ray imaging unit side among the slit on the X-ray imaging unit side and the slit on the X-ray source side is light reception of the X-ray imaging unit. It is the same as any one of the arrangement directions of the pixels on the surface.

  According to this configuration, the X-ray imaging apparatus is incident on the light receiving surface of the X-ray imaging unit because at least the direction of the slit on the X-ray imaging unit side is the same as one of the pixel arrangement directions of the X-ray imaging unit. The area of the pixel range irradiated with the slit-shaped X-rays can be increased. Therefore, the number of pixels that receive X-rays passing through the subject is relatively increased, and more pixels can be used effectively for signal processing. In this way, if the direction of the slit on the X-ray imaging unit side is tilted and the direction of the slit on the X-ray source side is also tilted in the same manner as the direction of the slit on the X-ray imaging unit side, X-rays emitted from the radiation source can be used effectively.

  The X-ray imaging apparatus according to claim 3 is the X-ray imaging apparatus according to claim 1 or 2, wherein the X-ray imaging unit determines the arrangement direction of the pixels by the X-ray imaging unit. It is arranged to be inclined by 45 degrees from the moving direction.

  According to such a configuration, the X-ray imaging apparatus has an inclination angle of 45 degrees with respect to the moving direction of the arranged pixels, so that the resolution is improved evenly in the two directions of the horizontal direction and the vertical direction. Further, since the X-ray imaging apparatus only needs to perform the same processing in the two directions of the horizontal direction and the vertical direction by the image signal processing means, the processing load can be reduced as compared with the case where the X-ray imaging apparatus is disposed at other inclination angles. .

  According to the present invention, the X-ray imaging apparatus can generate a high-resolution tomographic image at a low cost.

  Hereinafter, the best mode for carrying out the X-ray imaging apparatus of the present invention (hereinafter referred to as “embodiment”) will be described in detail with reference to the drawings.

[Configuration of Digital Panorama Camera]
FIG. 1 is a configuration diagram schematically showing a digital panorama photographing apparatus according to an embodiment of the present invention. The digital panoramic imaging apparatus (X-ray imaging apparatus) 1 uses a panoramic X-ray tomography method to photograph an X-ray image on a predetermined tomographic plane along the dentition of the maxilla / mandible of a subject (person) K for dental use. As shown in FIG. 1, an X-ray source 2, an X-ray imaging unit 3, an arm 4, a turning drive unit 5, an A / D conversion unit 6, and a large capacity are generated. A frame image storage means 7, a large-capacity processed image storage means 8, an all-image display storage means 9, an image signal processing means (frame image processing) 10, and an output means 11 are provided.

  The digital panoramic imaging apparatus 1 is roughly divided in that the X-ray imaging unit 3 is arranged with the arrangement direction of the pixels on the light receiving surface inclined from the moving direction of the X-ray imaging unit 3 (see FIG. 6). It is characterized by a method of signal processing of captured image data. Therefore, for convenience of explanation, first, an outline of structural features of the digital panorama photographing apparatus 1 will be described first with reference to FIGS. 2 to 4, and after describing each component, a specific example will be described. The signal processing method will be described while passing through.

  FIG. 2 is an explanatory view showing the moving direction of the X-ray imaging means shown in FIG. 1, and FIG. 3 is an explanatory view of the X-ray imaging means and slits inclined from the moving direction of the X-ray imaging means. The digital panorama imaging apparatus 1 moves the X-ray imaging unit 3 in a direction orthogonal to the X-ray incident direction for signal processing to be described later. FIG. 2 shows a configuration corresponding to the principle of the signal processing method. Here, in order to simplify the explanation of the principle, it is assumed that the X-ray source 2 is fixed as an example. X-rays emitted from the X-ray source 2 pass through the subject K and are received by the X-ray imaging means 3. The X-ray imaging unit 3 is housed in the sensor housing 101. The sensor housing 101 has a slit (not shown in FIG. 2, refer to the secondary slit 22a in FIG. 3) on the surface on the X-ray source 2 side, and is supported by the support means 102. It moves in the left-right direction in FIG. 2 on the rotating shaft 104 that rotates by driving the motor 103. That is, the X-ray imaging means 3 moves in a direction orthogonal to the X-ray incident direction (depth direction in FIG. 2).

  In addition, the arrangement direction of the pixels of the X-ray imaging unit 3 housed in the sensor casing 101 is inclined with respect to the moving direction of the X-ray imaging unit 3, and the primary slit 21a on the X-ray source 2 side is also X. It is inclined at the same angle as the line imaging means 3. FIG. 3A and FIG. 3B respectively show the arrangement of the conventional apparatus and the arrangement of the apparatus of this embodiment in comparison. 2 and 3, the side direction of the rectangular X-ray imaging unit 3 and the pixel arrangement direction are the same. That is, in FIGS. 2 and 3, the inclination in the pixel arrangement direction is represented by the inclination of the X-ray imaging unit 3 itself.

  As shown in FIG. 3A, normally (conventional), X-rays irradiated from the X-ray source 112 pass through a primary slit 121a formed in the X-ray shielding member 121 in order to control the beam diameter. To do. The X-ray beam that has passed through the primary slit 121a passes through the subject K, and is drilled in the X-ray shielding member 122 on the X-ray imaging means 113 side in order to reduce the diameter in order to match the X-ray beam to the element size and the like. The light is received after passing through the secondary slit 122a. For example, in the case of dental use, it is not necessary to incline the X-ray imaging means 113 or the slit, and the direction of the slit is maintained in the vertical direction.

  On the other hand, in this embodiment, as shown in FIG. 3B, X-rays irradiated from the X-ray source 2 pass through an inclined primary slit 21 a formed in the X-ray shielding member 21. The X-ray beam that has passed through the primary slit 21a passes through the subject K, and is inclined after passing through the inclined secondary slit 22a formed in the X-ray shielding member 22 on the X-ray imaging means 3 side. Light is received by the X-ray imaging means 3.

  Here, FIG. 3C shows a state in which the pixel range 32 irradiated with X-rays that have passed through the secondary slit 22a and entered the light receiving surface 31 of the X-ray imaging means 3 is viewed from the X-ray source 2 side. . In FIG. 3C, the X-ray imaging unit 3 is moved to the left. When the X-ray imaging unit 3 moves to the left, the pixel range 32 relatively moves to the right. Although the shape and size of the pixel range 32 change every moment as the X-ray imaging unit 3 moves, it can be considered that the pixel range 32 moves in the p direction and the q direction shown in FIG. Even if the shape and size change in this manner, the pixel range 32 can be considered to be uniform in the p direction and the q direction. Thus, as the X-ray imaging means 3 moves, it is uniform in the p direction and q direction corresponding to the pixel arrangement, so that the pixels included in the pixel range 32 are effectively used for signal processing to be described later. Can do.

  If only the X-ray imaging unit 3 is tilted and the secondary slit 22a is not tilted, the secondary slit 22a passes through the secondary slit 22a to the light receiving surface 31 of the X-ray imaging unit 3 in FIG. A state in which the pixel range 32 irradiated with incident X-rays is viewed from the X-ray source 2 side is shown. Also in FIG. 3D, if the X-ray imaging means 3 moves to the left, similarly, the pixel range 33 changes in shape and size every moment, but the uniform region in the p direction and the q direction is It can be considered that it is only near the center of the pixel range 33. Therefore, even if only the X-ray imaging means 3 is tilted, there are pixels that can be used effectively for signal processing to be described later, but the pixel area that can be used effectively becomes narrow.

  In the above description, the X-ray source 2 is fixed and the X-ray imaging unit 3 is moved. At this time, when viewed from the subject K, only the X-ray imaging means 3 is moving. Therefore, X-rays continuously irradiated from the X-ray source 2 and passed through one point of the subject K are received by a plurality of pixels adjacent in the moving direction of the X-ray imaging means 3.

  On the other hand, the digital panoramic imaging apparatus 1 includes an arm 4 and a turning drive unit 5. For example, the X-ray source 2 and the X-ray imaging unit 3 are fixed to the arm 4 as shown in FIG. Can move. The arm 4 shown in FIG. 4 is provided on the upper part of the support column 42 provided on the base 41. The arm 4 includes a support portion 43 extending in a horizontal direction from the support column 42, and a turning portion configured to be rotatable with respect to a rotation center at a lower end on the distal end side of the support portion 43 and to be able to slide on the rotation center. 44. The X-ray source 2 and the X-ray imaging unit 3 are suspended from the turning unit 44 at a predetermined interval so that the subject K can be placed therebetween.

  Therefore, in the configuration shown in FIG. 4, when viewed from the subject K, both the X-ray source 2 and the X-ray imaging means 3 are moving. Therefore, X-rays that are irradiated from the X-ray source 2 at a certain moment and pass through a plurality of points aligned in the horizontal direction of the subject K are received by a plurality of pixels adjacent in the moving direction of the X-ray imaging means 3. It will be. In other words, X-rays continuously irradiated from the X-ray source 2 and passed through one point of the subject K are received by a plurality of pixels adjacent in the moving direction of the X-ray imaging means 3. Become. That is, the configuration of FIGS. 2 and 3 (configuration for explaining the principle of signal processing) and the configuration of FIG. 4 (configuration of the present embodiment) are different in position, but use the same signal processing principle. Can do.

Returning to FIG. 1, each component of the digital panorama photographing apparatus 1 will be described.
The X-ray source 2 has a primary slit 21a, and irradiates the subject K with a slit-like beam (X-ray beam) generated by irradiating X-rays through the primary slit 21a at a predetermined timing. Is. The direction of the primary slit 21 a is inclined in the same manner as the inclination angle from the moving direction of the X-ray imaging unit 3 to the arrangement direction of the pixels on the X-ray imaging unit 3. Thereby, the X-rays irradiated from the X-ray source 2 can be used effectively.

  The X-ray imaging means 3 receives X-rays emitted from the X-ray source 2 and transmitted through the subject K, and images a portion of the subject K where X-rays are transmitted at a predetermined frame rate. In the X-ray imaging unit 3, pixels are two-dimensionally arranged along one axis and the other axis that are orthogonal to each other on the light receiving surface. In other words, on the light receiving surface of the X-ray imaging means 3, the pixels are arranged in a grid pattern in the horizontal direction (one axial direction) and the vertical direction (the other axial direction). The X-ray imaging means 3 is an X-ray image sensor, an X-ray detector, or a combination thereof. Here, the image sensor is, for example, a CCD (Charge Coupled Device) image sensor, a CMOS image sensor, a TFT (Thin Film Transistor) sensor, a CdTe sensor, or the like. The X-ray detector is an X-ray image intensifier (I.I.), a flat panel detector (FPD), or the like. In the present embodiment, the X-ray imaging unit 3 will be described as a CCD image sensor including a general commercially available scintillator. In this case, the X-ray imaging means 3 can be configured with one pixel size of, for example, 100 μm × 100 μm and arranged in 1000 pixels × 1000 pixels.

  The arm 4 holds the X-ray source 2 and the X-ray imaging means 3 at a predetermined interval. This interval is set to, for example, 30 cm to 1 m so that the subject K is accommodated between the X-ray source 2 and the X-ray imaging means 3. In addition, the irradiation part of the X-ray source 2 and the light-receiving surface of the X-ray imaging means 3 are arranged to face each other. Further, the arm 4 is configured to be capable of rotating and sliding around the rotation center O. Accordingly, the X-ray imaging unit 3 can capture a tomographic image in an arbitrary direction around the subject K while maintaining a predetermined distance between the X-ray source 2 and the X-ray imaging unit 3.

The turning drive means (drive means) 5 moves the X-ray imaging means 3 in a direction orthogonal to the X-ray incident direction. The turning drive means 5 includes a motor, an actuator, and the like, and turns the arm 4 so as to rotate at a predetermined angular velocity. The turning drive means 5, the X-ray source 2 and the X-ray imaging means 3 are controlled by a controller (not shown), and the X-ray source 2 emits X-rays while the turning drive means 5 turns the arm 4. The imaging is repeated, and the X-ray imaging unit 3 captures an X-ray image (simple X-ray imaging image) of the subject K in synchronization with the X-ray irradiation timing and outputs it to the A / D conversion unit 6.
The A / D conversion means 6 acquires the output signal (frame image) of the X-ray imaging means 3, performs A / D conversion, and outputs the output signal (frame image) of the X-ray imaging means 3 that has been A / D converted to a large value. It is stored in the capacity frame image storage means 7. The image signal processing means 10 reads out the frame image from the large-capacity frame image storage means 7 and stores the result of integration processing using the frame image as a processed image in the large-capacity processing image storage means 8. That is, the image signal processing unit 10 acquires the frame image converted and output by the A / D conversion unit 6 and processes it.

  The large-capacity frame image storage means 7, the large-capacity processing image storage means 8, the all-image display storage means 9, and the image signal processing means 10 can be realized by a general computer (computer), for example. A CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), and an input / output interface are included.

The large-capacity frame image storage means 7 stores an output signal (frame image) of the X-ray imaging means 3 subjected to A / D conversion, and includes a general image memory, a hard disk, and the like.
The large-capacity processed image storage unit 8 stores a plurality of processed images generated as a result of the integration process by the image signal processing unit 10 and includes a general image memory, a hard disk, and the like. The large-capacity processed image storage means 8 has a plurality of memory areas corresponding to areas obtained by dividing the pixels of the X-ray imaging means 3 more finely than the pixel width. Specific examples will be described later. The large-capacity processed image storage unit 8 is used for processing such as image synthesis by the image signal processing unit 10.

  The all-image display storage unit 9 stores a tomographic image (a tomographic image corresponding to a tomographic plane to be displayed) generated as a result of the synthesis processing by the image signal processing unit 10 and displayed on the output unit 11. A typical image memory. This tomographic image is represented by a luminance value, for example. Note that the output unit 11 includes, for example, a CRT (Cathode Ray Tube), a liquid crystal display (LCD), a PDP (Plasma Display Panel), an EL (Electronic Luminescence), and the like.

[Tomographic image]
Here, the tomographic image stored in the all-image display storage unit 9 will be described with reference to FIG. FIG. 5 is a plan view of the dentition. In the state shown in FIG. 5, the X-ray source 2 emits X-rays from the front teeth P side of the dentition of the person who is the subject K (see FIG. 1). Although the imaging unit 3 receives light, the X-ray source 2 and the X-ray imaging unit 3 rotate and slide during imaging. Here, the tomographic plane F is taken at the center in the front-rear direction of the dentition.

  The tomographic image (panoramic tomographic image) on the tomographic plane F shown in FIG. 5 is formed by superimposing a plurality of processed images at a predetermined interval. An actual panoramic tomographic image is constructed by synthesizing hundreds to thousands of processed images. Further, all processed images may be formed by being overlapped at equal intervals, or may be overlapped by changing a shift width.

Returning to FIG. 1, the description of the configuration of the digital panorama photographing apparatus 1 will be continued.
The image signal processing means 10 acquires an output signal (frame image) of the A / D conversion means 6, generates a processed image from the frame image of the subject K, and synthesizes a tomographic image using a plurality of processed images. It is. The image signal processing means 10 includes control means including a CPU that executes various processes described later by developing a predetermined program stored in a ROM, an HDD, or the like in a RAM.

The image signal processing means 10 has a function as a signal integration means and a function as an image composition means.
The image signal processing means 10 is output from a predetermined pixel as a function of the signal integrating means within a time during which the predetermined pixel of the X-ray imaging means 3 moves by a predetermined pixel width as the X-ray imaging means 3 moves. The signal value is prorated according to the moving position of the predetermined pixel, integrated in each memory area for the predetermined pixel, and the X-ray passing through the predetermined point of the subject is received by the predetermined pixel after the predetermined pixel. A processed image is generated by distributing the values of signals output from the adjacent pixels in accordance with the moving positions of the adjacent pixels, and integrating the values in the memory areas for the predetermined pixels. Specific examples will be described later.

  The image signal processing means 10 acquires, as a function of the image composition means, a plurality of processed images for a predetermined tomographic surface of the signal-processed dentition, and superimposes the acquired plurality of processed images with a predetermined shift width. By combining them, an image (panoramic tomographic image) corresponding to a tomographic plane to be displayed is synthesized. The tomographic plane to be displayed may be determined in advance, or may be specified by information from an input device (not shown). The combined tomographic image is output to the output unit 11.

だけ移動すると、Ｘ線撮像手段３は、受光面上の縦方向（ＯＸ方向）と、横方向（ＯＹ方向）にそれぞれ（ｄ／１０）だけ移動することとなる。この間に旋回駆動手段５がアーム４を旋回しながらＸ線源２がＸ線を照射することができる。なお、図６において、Ｘ線は、紙面に垂直な方向手前の位置から被写体に照射され、Ｘ線撮像手段３は、紙面に垂直な方向で被写体よりも奥の位置で左方に移動する。また、図６では、二次スリット２２ａ（図３参照）の図示を省略した。 [Concrete example]
Hereinafter, a signal processing method in the digital panorama photographing apparatus 1 will be described. First, the function of the signal integration means for the image signal processing means 10 will be specifically described. In the digital panorama photographing apparatus 1, the X-ray imaging means 3 moved by the turning drive means 5 has an arrangement direction (vertical direction and horizontal direction) in which a plurality of pixels G are arranged on the light receiving surface as shown in FIG. The X-ray imaging unit 3 is disposed so as to be inclined from the moving direction. In the present embodiment, the X-ray imaging unit 3 is disposed with the arrangement direction (vertical direction and horizontal direction) of the plurality of pixels G on the light receiving surface inclined by 45 degrees from the moving direction of the X-ray imaging unit 3. ing. That is, the horizontal direction (OX direction) and the vertical direction (OY direction) on the light receiving surface of the X-ray imaging means 3 are inclined 45 degrees with respect to the moving direction (left in FIG. 6). Here, in each pixel G, an area divided more finely than the pixel width d is assumed. In the example shown in FIG. 6, it is assumed that each pixel G is virtually divided into 10 equal parts in the vertical and horizontal directions. For example, the X-ray imaging means 3

The X-ray imaging means 3 moves only (d / 10) in the vertical direction (OX direction) and the horizontal direction (OY direction) on the light receiving surface. During this time, the X-ray source 2 can irradiate X-rays while the turning drive means 5 turns the arm 4. In FIG. 6, X-rays are irradiated onto the subject from a position in front of the direction perpendicular to the paper surface, and the X-ray imaging unit 3 moves to the left at a position deeper than the subject in the direction perpendicular to the paper surface. In FIG. 6, the secondary slit 22a (see FIG. 3) is not shown.

  A signal indicating the result of light reception by the X-ray imaging unit 3 is output from the X-ray imaging unit 3 to the large-capacity frame image storage unit 7 via the A / D conversion unit 6. The image signal processing unit 10 reads out the frame image from the large-capacity frame image storage unit 7 and stores the result of integration processing using the frame image in the large-capacity processing image storage unit 8 as a processed image. In this process, the image signal processing unit 10 integrates the signal read from the large-capacity frame image storage unit 7 in the memory area of the large-capacity processing image storage unit 8. The large-capacity processed image storage unit 8 includes, for example, a memory area of a virtual division number (for example, 10 × 10) of the pixels G for each 1000 × 1000 pixels. In order to avoid complicated description of the memory area corresponding to a large number of pixels arranged two-dimensionally on the X-ray imaging means 3, here, X-ray imaging means comprising twelve pixels arranged one-dimensionally on the light receiving surface Assuming In order to give priority to the description of the function of the signal integration means of the image signal processing means 10, the description will be made assuming that the pixel arrangement direction in the assumed X-ray imaging means coincides with the movement direction.

Here, the memory area will be described with reference to FIG. FIG. 7 is an explanatory diagram of the large-capacity frame image storage means shown in FIG. 1. FIG. 7A is a schematic diagram illustrating an example of a method for obtaining an LSF of a recording system that is convolved with a predetermined point of a subject. (B) shows a memory area for each pixel. Here, the assumed X-ray imaging means is referred to as X-ray imaging means 3a. The X-ray imaging means 3a is assumed to be a one-line CCD image sensor of 1 vertical pixel (pixel) × 12 horizontal pixels (pixel). This one-line CCD image sensor has pixels (pixels) G ₁ ,..., G ₁₂ , and each pixel width is d.

At a certain point in time, as shown on the upper side in FIG. 7A, the pixel G ₁ is arranged inside (left side) the edge E of the subject, and the pixel G ₂ is arranged outside (right side) the edge E. In FIG. 7, the X-ray imaging unit 3 a moves in a direction approaching or moving away from the edge E. In this example, it is assumed that the X-ray imaging unit 3a moves in a direction approaching the edge E. The large-capacity processed image storage means 8 has a plurality of memory areas corresponding to areas obtained by dividing each pixel finer than the pixel width d for each pixel. This is called an address group. For example, the address group A ₁ corresponding to the pixels G _1, address group A ₂ or the like corresponding to the pixel G ₂ is provided. In this example, each pixel is virtually divided into ten in the moving direction of X-ray imaging means 3a (the direction from right to left in FIG. 7). Then, corresponding to the divided area where the pixel is virtually divided, the memory area (address group) for the pixel is divided into 10 storage areas (addresses). 7, the identification information of the address of each pixel corresponding to the nearest divided regions to the edge E when outside (right) of an object edge E (area ID) as R _1, or less, in order R _2, ... , R ₁₀ . Hereinafter, a predetermined pixel is referred to as a first pixel, and an adjacent pixel adjacent to a predetermined pixel that receives X-rays passing through a predetermined point of the subject next to the predetermined pixel is referred to as a second pixel. In this case, the large-capacity processed image storage means 8 has 10 memory areas corresponding to the areas IDR ₁ ,..., R ₁₀ for every 12 pixels, as shown in FIG. In FIG. 7B, the numbers described in the address group A ₁ to the address group A ₃ indicate an example of signal strength.

  The image signal processing means 10 sets the value (for example, luminance value) of the signal output from the first pixel to the position during movement of the first pixel according to the elapsed time until the first pixel moves by the pixel width. Accordingly, the value is accumulated in each memory area for the first pixel, and the value of the signal output from the second pixel is accumulated in each memory area for the first pixel according to the moving position of the second pixel. Here, the image signal processing means 10 may add and average the values of the signals output from the first pixel and the second pixel in each memory area for the first pixel. For example, when signals output from the first pixel and the second pixel are added 10 times in total, a value obtained by dividing the added value (integrated value) by 10 may be stored. By the processing of the image signal processing means 10, the above-described processed image is formed based on the value of the signal accumulated in each memory area for each pixel for each frame image. The image signal processing means 10 outputs a processed image for a predetermined tomographic plane of the dentition as a processing result to the large-capacity processed image storage means 8.

  The function of the image signal processing means 10 is realized by the CPU developing and executing a predetermined program stored in the ROM or the like on the RAM. Therefore, the image signal processing means 10 can also be realized by executing a signal processing program that causes a general computer to execute the functions of the image signal processing means 10 described above. This program can be distributed via a communication line, or can be written on a recording medium such as a CD-ROM for distribution.

[Operation of Digital Panorama Camera]
The operation of the image signal processing means 10 will be described mainly with reference to FIG. 8 (refer to FIG. 1 as appropriate) as the operation of the digital panorama photographing apparatus shown in FIG. FIG. 8 is a flowchart showing the operation of the digital panorama photographing apparatus shown in FIG. First, the digital panoramic imaging apparatus 1 performs A / D conversion on a signal that is imaged by the X-ray imaging unit 3 on a predetermined tomographic surface of the dentition and output from each pixel by the A / D conversion unit 6 (step S1). ). The A / D converted output signal (frame image) of the X-ray imaging means 3 is stored in the large-capacity frame image storage means 7. Then, the digital panorama photographing apparatus 1 reads out the frame image from the large-capacity frame image storage unit 7 by the image signal processing unit 10 and determines the first pixel according to the position of the moving pixel of the X-ray imaging unit 3. The output signal and the output signal of the second pixel are integrated in the memory area for the first pixel of the large-capacity processed image storage means 8 (step S2). Then, the digital panorama photographing apparatus 1 stores, in the large-capacity processed image storage unit 8, a signal integrated in each memory area for each pixel by frame image by the image signal processing unit 10. Here, the signals accumulated while the pixels of the X-ray imaging means 3 move by a predetermined width of the pixels are stored. Then, the digital panorama photographing apparatus 1 acquires a plurality of processed images corresponding to the plurality of frame images from the large-capacity processed image storage unit 8 by the image signal processing unit 10 (step S3). The combined tomographic image is stored in the all-image display storage unit 9 by being developed in the capacity processed image storage unit 8 and superposed with a predetermined shift width (step S4). The digital panorama photographing apparatus 1 reads the synthesized tomographic image from the all-image display storage unit 9 and outputs it to the output unit 11 (step S5).

[Specific example of operation of digital panorama camera]
Here, in order to simplify the description, it is assumed that the X-ray imaging means 3a includes 12 pixels arranged one-dimensionally on the light receiving surface. FIG. 9 is a diagram illustrating an example of signal strength in the vicinity of an edge. FIG. 9 shows the time when each pixel moves in the direction approaching the edge E (the left side in FIG. 9) in 10 stages in the vertical direction in the figure. Here, the pixel G ₁ inside the edge E (left side in FIG. 9) is defined as a first pixel, and the pixel G ₂ adjacent thereto is defined as a second pixel. Further, the intensity of the signal received by the pixel G ₁ on the inner side from the edge E (left side in FIG. 9) is set to “0”. Therefore, in this case, the signal output from the first pixel (pixel G ₁ ) is “0”, and this value is integrated. Further, the intensity of the signal received by each of the pixels G ₂ and G ₃ outside the edge E (right side in FIG. 9) is set to “100”. When the region corresponding to 10% of the pixel width d of the pixel G ₂ moves inward (left side in FIG. 9) from the edge E, the intensity of the signal received by the pixel is “90”. Become. Similarly, when the region corresponding to the length of α% of the pixel width d of the pixel G ₂ moves inward (left side in FIG. 9) from the edge E, the intensity of the signal received by the pixel G ₂ is “100-α”.

For example, when the intensity of the signal received by the pixel G ₂ is “90”, the image signal processing means 10, that is, a region corresponding to a length of 10% of the pixel width d of the pixel G ₂ is inside the edge E ( In the case of moving to the left in FIG. 9, the signal strength “9 (= 90/90) is assigned to the address of the area ID“ R ₁₀ ”in the ₁₀ memory areas of the address group A ₁ of the large-capacity processed image storage means 8. 10) "is added. Further, the image signal processing means 10 has, for example, a region corresponding to a length of 20% of the pixel width d of the pixel G ₂ from the edge E when the intensity of the signal received by the pixel G ₂ is “80”. When moving inward (left side in FIG. 9), the signal strength is assigned to the addresses of the area IDs “R ₁₀ ” and “R ₉ ” in the ₁₀ memory areas of the address group A ₁ of the large-capacity processing image storage unit 8. As a result, only “8 (= 80/10)” is added. The same applies hereinafter.

Further, the image signal processing means 10 performs the same processing using the pixel G ₂ as the first pixel and the adjacent pixel G ₃ as the second pixel. More specifically, the image signal processing unit 10 determines that the address group when an area corresponding to, for example, 20% of the pixel width d of the pixel G ₂ moves to the inside (left side in FIG. 9) from the edge E. Of the ten memory areas of A ₂ , “8” is added as the signal strength to the addresses of the area IDs “R ₁ ” to “R ₈ ”. In the section example shown in FIG. 9, the intensity of the signal received by the pixel G ₃ remains unchanged at “100”. Therefore, for example, when the area corresponding to 20% of the pixel width d of the pixel G ₃ has moved to the left side in FIG. 9, the image signal processing means 10 has 10 memory areas in the address group A _2. Among them, “10” is added to the addresses of the region IDs “R ₁₀ ” and “R ₉ ” as the signal strength.

The image signal processing means 10 is proportionally divided into the output signal of the pixel G ₁ and the region of the pixel G ₂ that has moved inward (left side in FIG. 9) from the edge E out of the change in signal intensity shown in FIG. The output signal of the pixel G ₂ is integrated in each memory area of the address group A ₁ of the large-capacity processed image storage means 8. Further, the image signal processing means 10 out of the change in signal intensity shown in FIG. 9, the pixel G ₂ that is prorated to the area arranged outside the edge E (right side in FIG. 9) of the pixel G _2. Output signal of the pixel G ₃ and the output signal of the pixel G ₃ divided into the region arranged in the range up to the pixel width d outside the edge E (right side in FIG. 9) of the pixel G _3. It accumulates in each memory area of the address group A ₂ of the image storage means 8. Further, the image signal processing unit 10, among the changes in the signal intensity shown in FIG. 9 are arranged in a range of outward (in Fig. 9 right) the edge E of the pixel G ₃ from the pixel width d to 2d the output signal of the pixel G ₃ is prorated to the region, is arranged in the range of pixel width d on the outer (in FIG. 9 right) the edge E of the pixel G ₄ (not shown) adjacent to the pixel G ₃ to 2d The output signal of the pixel G ₄ that is allocated to the area that is allocated is added to each memory area of the address group A ₃ of the large-capacity processed image storage means 8. The same applies hereinafter. FIG. 10 shows changes in signal strength stored in the address group A ₁ , the address group A _2, and the address group A ₃ at this time. In FIG. 10, the ten stages of the time series shown in FIG. 9 are t = 1 to 10.

  In the above, for the sake of simple explanation, the X-ray imaging means 3a, which is a one-dimensional CCD image sensor, and a memory area corresponding to the X-ray imaging means 3a have been described. 3, a specific example of an address group corresponding to an area obtained by dividing one pixel vertically and horizontally into three will be described with reference to FIGS. 11 and 12 (see FIGS. 6 and 10 as appropriate). 11 is an explanatory diagram for explaining the signal intensity accumulated in the memory area corresponding to the X-ray imaging unit shown in FIG. 6, and FIG. 12 is a diagram illustrating the accumulated signal intensity and the pixel intensity shown in FIG. It is a figure which shows the correspondence with an arrangement | sequence.

The memory structure shown in FIG. 11 includes 100 blocks that intersect 10 rows × 10 columns. Rows M _{1 to} M ₁₀ each have three stages of data, and each address corresponding to an area obtained by dividing one pixel vertically into 10 equal parts. Further, columns N _{1 to} N ₁₀ shown in FIG. 11 indicate addresses corresponding to a region obtained by dividing one pixel into 10 equal parts. The bottom leftmost block (row M ₁₀ , column N ₁ ) shown in FIG. 11 is viewed as being the left end of the first pixel in the moving direction of the X-ray imaging means 3 inclined 45 degrees shown in FIG. When the entire storage structure shown in FIG. 11 is rotated about 70 degrees clockwise, the storage structure shown in FIG. 11 is made to correspond to the first pixel in the moving direction of the X-ray imaging means 3 shown in FIG. be able to. Hereinafter, the meaning of each of the three stages of data in each block will be described sequentially.

<First stage of each block>
For example, the numerical values of the first stage in the bottom row M ₁₀ in FIG. 11, 10 of the virtual corresponding to the side directed from the leftmost pixel in the moving direction the head of the X-ray imaging means 3 shown in FIG. 6 to the lower end It corresponds to each subpixel data. The numerical values in the first row of the row M ₁₀ shown in FIG. 11 are the signals of the addresses of the area IDs “R ₁ ” to “R ₁₀ ” accumulated until time t = 10 in the address group A ₂ shown in FIG. The strength is shown respectively. This is the same as the result when the one-dimensional CCD line sensor is virtually divided into 10 parts (laterally). The numerical values of the first stage of the other rows M _{1 to} M ₉ are the same as the numerical values of the first stage of the row M ₁₀ .

<Second stage of each block>
For example, the numerical values arranged in the second row of each block in the leftmost column N ₁ in FIG. 11 from the row M ₁₀ (from the bottom) toward the row M ₁ (from the top) are shown in FIG. It corresponds to each data of 10 virtual sub-pixels corresponding to the side from the left end to the upper end of the first pixel in the moving direction of the X-ray imaging means 3 shown. The numerical values arranged from the bottom in the second stage of each block of the column N ₁ shown in FIG. 11 are the area IDs “R ₁ ” to “# ₁ ” accumulated until the time t = 10 of the address group A ₂ shown in FIG. The signal strength of the address “R ₁₀ ” is shown. This is the same as the result when the one-dimensional CCD line sensor is virtually (vertically) divided into 10 equal parts. The other values in the second row of the columns N _{2 to} N ₁₀ are the same as the values in the second row of the column N ₁ .

<3rd stage of each block>
In each block, the numerical value in the third stage is the total value of the numerical value in the first stage and the numerical value in the second stage. In other words, the numerical values in the third stage indicate the signal intensity integrated up to time t = 10 at each address corresponding to the area obtained by dividing one pixel into 100 for the two-dimensionally arranged X-ray imaging means 3. Yes. In FIG. 12, the numerical values in the third stage of the blocks (M ₁ , N ₁ ) to (M ₁₀ , N ₁₀ ) shown in FIG. 11 are set to the inclination angles in the pixel array direction of the X-ray imaging means 3 shown in FIG. Together, it is inclined 45 degrees clockwise. Note that the numerical values shown in each block in FIG. 12 are signal values accumulated in each memory area corresponding to one pixel in the large-capacity processing image storage unit 8. The leftmost block in FIG. 12 corresponds to the leftmost region obtained by virtually dividing the pixel G shown in FIG. 6 and has the lowest signal value because it is the head in the movement direction. On the other hand, the rightmost block in FIG. 12 corresponds to the rightmost region obtained by virtually dividing the pixel G shown in FIG. 6 and has the highest signal value because it is the last in the movement direction. In FIG. 12, rows L _{1 to} L ₁₇ indicate signal intensities accumulated in successive memory areas corresponding to the moving direction of the X-ray imaging unit 3 shown in FIG. For example, in row L ₉ , the numerical values arranged from the left to the right are “110, 128, 144, 158, 170, 180, 188, 194, 198, 200”, so the difference between adjacent numerical values is “18, 16, 14, 12, 10, 8, 6, 4, 2 ". Here, in order to simplify the description, ESF (Edge Spread Function) and LSF will be described again assuming the X-ray imaging means 3a, which is a one-dimensional CCD image sensor, and a memory area corresponding thereto.

The signal strength of each of the ten memory areas of the address group A ₁ shown in FIG. 10 at time t = 10 and the signal strength of each of the ten memory areas of the address group A ₂ when time t = 10. FIG. 13 shows the intensity as a graph. The horizontal axis of the graph of FIG. 13 is obtained by normalizing the distance from the edge E corresponding to the region ID to d = 10. Specifically, the signal strengths of the distances “−9” to “0” from the edge E indicate the signal strengths of the addresses of the area IDs “R ₁ ” to “R ₁₀ ” of the address group A ₁ , respectively. The signal strengths at the distances “1” to “10” from the edge E indicate the signal strengths of the addresses of the area IDs “R ₁ ” to “R ₁₀ ” of the address group A ₂ , respectively. The signal strength at the distance “11” from the edge E indicates the signal strength of the address of the area ID “R ₁ ” of the address group A ₃ . FIG. 13 is a graph showing the ESF for the signal strength example shown in FIG. For example, the signal intensity from “1 to 10” from the edge is “55, 64, 72, 79, 85, 90, 94, 97, 99, 100”.

  14 is obtained when a difference is obtained with respect to the symmetrical signal intensity around the “distance“ 0 ”from the edge” shown in FIG. 13. This FIG. 14 differentiates the ESF shown in FIG. 14 is a graph showing the LSF that can be obtained by dividing the distance from the edge E. Here, Δ = 10 corresponds to the pixel width d. −10 indicates a difference between the signal intensity at the distance “−10” from the edge E and the signal intensity at the distance “−9” from the edge E. Δ = −9 indicates the difference between the signal intensity at the distance “−9” from the edge E and the signal intensity at the distance “−8” from the edge E. Δ = −8 indicates the difference between the signal intensity at the distance “−8” from the edge E and the signal intensity at the distance “−7” from the edge E. The same applies hereinafter. The signal intensity at the distance “−10” from the edge E was set to “0”. As shown in FIG. 14, the X-ray intensity signal obtained from the difference in the signal intensity symmetrical about the distance “0” from the edge has a triangular waveform. According to the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 of the present embodiment, the shape of the X-ray intensity signal obtained from the edge E is a triangular wave. This means that the shape of the X-ray intensity signal obtained from the difference in the signal intensity in one direction away from the edge becomes a sawtooth waveform. Note that the length of the base of the sawtooth waveform is the pixel width d.

[Resolution of generated image]
Here, the resolution of an image generated by the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 of the present embodiment will be described with reference to FIGS. 15 to 18. 15 is an explanatory diagram of the LSF shown in FIG. 14, where (a) shows a triangular wave, (b) shows a function obtained by Fourier transform of (a), and FIG. 16 shows the function shown in FIG. It is explanatory drawing of LSF, (a) is a rectangular wave, (b) has each shown the function which carried out the Fourier transform of (a). FIG. 17 is an explanatory diagram of the spatial frequency, where (a) shows a stationary state, and (b) and (c) show a signal processing time. FIG. 18 is a graph showing the MTF obtained from the LSF shown in FIG.

  First, a triangular wave corresponding to the LSF generated by the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 of the present embodiment will be described with reference to FIG. When the triangular wave A (x) shown in FIG. 15A at the edge E is LSF, the MTF (Modulation Transfer Function) is obtained by the calculation represented by the equation (1) in the real space region (x space). . “*” In the equation (1) indicates an operation symbol of convolution integration. In addition, the triangular wave A (x) in Formula (1) is shown by Formula (2). Further, the function f (x) indicating the edge E is expressed by Expression (3).

  In order to perform the calculation of the above-described formula (1) in the frequency domain, the formula (4) is obtained by performing Fourier transform on the triangular wave A (x) shown in FIG. In the equation (4), ω represents a spatial frequency (ω space). If the complex part shown by the right side of this Formula (4) is performed and the real part is calculated | required, Formula (5) will be obtained. The waveform shown by Formula (5) is shown in FIG.15 (b). Thereby, when the calculation of the above-described equation (1) is performed in the frequency domain, the equation (6) is obtained.

  Next, a comparative example with the LSF generated by the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 of the present embodiment will be described with reference to FIG. At the edge E, the MTF having the rectangular wave C (x) shown in FIG. 16A as an input is obtained in the real space region by the calculation represented by the equation (7). In addition, the rectangular wave C (x) in Formula (7) is shown by Formula (8). The function f (x) indicating the edge E is expressed by the above-described equation (3).

  In order to perform the calculation of Equation (7) in the frequency domain, when the rectangular wave C (x) shown in FIG. 16A is Fourier-transformed, Equation (9) is obtained. If the complex part shown by the right side of this Formula (9) is performed and the real part is calculated | required, Formula (10) will be obtained. The waveform shown by Formula (10) is shown in FIG.16 (b). As a result, when the calculation (calculation in x space) of the above-described formula (7) is performed in the frequency domain (calculation in the ω space), formula (11) is obtained.

  Here, the spatial frequency ω will be described with reference to FIG. When the X-ray imaging means 3 (see FIG. 7) of the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 is still, the LSF of the recording system that is convolved with a predetermined point of the subject is shown in FIG. As shown to a), it becomes a rectangular wave. In the area 201 shown in FIG. 17A, the width of the rectangle is the same as the pixel width d (see FIG. 7). When forming a light and dark line pair having the same width (line pair) using two consecutive pixels of the displayed image, the region 201 and the region 202 having the same width as the region 201 are combined. The portion corresponds to one period (2d) of the rectangular wave. In this case, the spatial frequency ω is expressed by Expression (12). For example, if the pixel width d is 0.1 [mm] = 100 [μm], the spatial frequency ω is 5 [cycles / mm].

Further, when the graph is created using the transition of the signal strength illustrated in FIG. 10, when the time t = 10, instead of using the signal strength of all the memory areas of the address group A ₁ and the address group A ₂ for the pixel signal intensity of address of the area ID "R _10" in the address group a _1, based on the signal strength of all the memory area of the address group a _2, the outside (in Fig. 9 right) the edge E A graph can also be created using signal intensities in the range up to width d. In this case, in the graph showing the ESF shown in FIG. 13, it is possible to create a graph only in the right range from the position of the distance “0” from the edge E. According to this, the LSF graph can create a sawtooth waveform graph only in the right range from the position of the distance difference “0” from the edge E in the LSF graph shown in FIG. The graph created at this time is shown in FIG. The waveform shown in FIG. 17B corresponds to a single pixel of the displayed image. Including the broken line portion corresponds to the LSF shown in FIG.

  A waveform formed by connecting waveforms indicated by solid lines in FIG. 17B corresponds to continuous pixels in a displayed image. The graph created at this time is shown in FIG. Regions 211, 212, and 213 shown in FIG. 17C correspond to three consecutive pixels in the displayed image. Regions 211, 212, and 213 correspond to one period (d) of the sawtooth wave. In this case, the spatial frequency ω is expressed by Expression (13). For example, when the width d of the sawtooth wave is 0.1 [mm] = 100 [μm], the spatial frequency ω is 10 [cycles / mm].

Next, the MTF of an image generated by the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 of the present embodiment will be described with reference to FIG.
In the above equation (6), when the amplitude at the origin of ω = 0 is normalized to 1, an MTF is obtained. As indicated by a solid line in FIG. 18, the value of ω when the MTF value is “0” is “1 / d”. On the other hand, the MTF obtained by normalizing the amplitude at the origin of ω = 0 to 1 in the above equation (11) is ω when the MTF value is “0” as shown by the broken line in FIG. The value of is 1 / (2d). That is, an image generated by the digital panoramic imaging apparatus (X-ray imaging apparatus) 1 according to the present embodiment is compared with a case where such signal processing is not performed at all in a spectral region as shown in FIG. The cut-off frequency value becomes high. That is, the image generated by the image signal processing means 10 is a high resolution image. In the waveform after the Fourier transform of the sawtooth wave shown in FIG. 17B, the position of the intersection with the ω axis (horizontal axis) is the same position as in FIG. 15B. Therefore, also in this case, the value of the cut-off frequency is higher in the spectral region than in the case of the rectangular wave, so that the resolution of the image can be improved.

As described above, for the sake of simple explanation, the ESF and LSF have been described on the assumption that the X-ray imaging means 3a, which is a one-dimensional CCD image sensor, and a memory area corresponding to the X-ray imaging means 3a. Of course, the resolution of the means 3 is improved as well. For example, the signal values “110, 128, 144, 158, 170, 180, 188, 194, 198, 200” in the row L ₉ in FIG. 12 have distances from the edges shown in FIG. Is the same as double the signal intensity of each. Therefore, it is possible to obtain an ESF similar to that shown in FIG. In the digital panorama photographing apparatus 1 according to the present embodiment, the arrangement direction of the pixels arranged on the light receiving surface of the X-ray imaging unit 3 is inclined 45 degrees with respect to the moving direction of the X-ray imaging unit 3. The resolution is improved evenly in two directions (horizontal direction) and vertical direction (vertical direction).

  According to the present embodiment, the digital panorama imaging apparatus (X-ray imaging apparatus) 1 does not change the X-ray imaging means 3 to a high-resolution one, and performs signal processing to the horizontal direction (one axial direction) and the vertical direction. A high-resolution image can be generated in two directions (direction of the other axis). Therefore, a high-resolution tomographic image can be generated at low cost.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can implement in the range which does not change the meaning. For example, in the present embodiment, the arrangement direction of the pixels arranged on the light receiving surface of the X-ray imaging unit 3 has been described as being inclined by 45 degrees with respect to the moving direction of the X-ray imaging unit 3, but the inclination angle is It is not limited to this. However, when the inclination angle is 45 degrees, the image signal processing means 10 can similarly perform integration processing in two directions of the horizontal direction (one axial direction) and the vertical direction (the other axial direction). Since it is good, it can calculate easily compared with the case where it arrange | positions with another inclination angle, and can reduce a processing load.

  In the present embodiment, as illustrated in FIG. 6, in the rectangular X-ray imaging unit 3, each pixel is two-dimensionally arranged along an axis parallel to each side of the outer periphery. It is not limited to this. For example, each pixel provided in the X-ray imaging unit 3 is two-dimensionally arranged along an axis inclined by, for example, 45 degrees from each side of the outer periphery of the rectangular X-ray imaging unit 3, that is, a rhombus pixel An array of X-ray imaging means may be used. In this case, a high-resolution image can be generated in two vertical and horizontal directions by moving the X-ray imaging unit itself having a rhombus pixel arrangement without tilting. In this embodiment, as illustrated in FIG. 6, each pixel in the X-ray imaging unit 3 has a square shape. However, the present invention is not limited to this, and the shape of the pixel is, for example, , Rectangles, hexagons and other polygons, circles, ellipses, etc. In the present embodiment, the X-ray imaging unit 3 is described as moving in the horizontal direction (horizontal direction) in panoramic imaging, but may be continuously moved in the vertical direction (vertical direction).

  Further, in the present embodiment, the best mode in which the pixel arrangement direction of the X-ray imaging unit 3, the primary slit 21 a, and the secondary slit 22 a are all inclined from the moving direction of the X-ray imaging unit 3. However, the present invention is not limited to this. If the arrangement direction of the pixels of the X-ray imaging unit 3 is inclined with respect to the moving direction of the X-ray imaging unit, two-dimensional signal processing is performed. The resolution can be improved. Further, in addition to the X-ray imaging unit 3, when the secondary slit 22 a is similarly inclined, the X-ray imaging unit 3 uses the X-ray imaging unit 3 as compared with the case where the slit direction is different from the pixel arrangement direction. The area of the region that can receive the line can be increased. Therefore, the number of pixels that receive X-rays passing through the subject is relatively increased, and more pixels can be used effectively for signal processing. In the best mode, the X-rays emitted from the X-ray source 2 can be used effectively, which is more preferable.

Further, in the present embodiment, each pixel is described as being virtually divided into 10 pixels, but may be 2 or more. For example, when it is equally divided into n (n ≧ 2), that is, when the pixel width d is “n (n ≧ 2)”, it is as follows. In this case, identification information (area ID) of a plurality of memory areas corresponding to the divided area of each pixel is set to R ₁ ,..., R _{n in} order from the edge E. The large-capacity processed image storage means 8 has n memory areas corresponding to the areas R ₁ ,..., R _n for each pixel (for each address group). Then, in the memory area of the address group corresponding to the predetermined pixel, the intensity of the signal integrated to the i (1 ≦ i ≦ n) th address from the side closer to the edge E is expressed by the equations (14) and (15). ). Here, for example, assuming that n = 10 and i = 1, 2, the result when the value of the horizontal axis in FIG. 13 is “1” and the result when “2” are obtained, respectively.

  Further, in the present embodiment, each pixel is virtually equally divided, but if the waveform of the triangular wave shown in FIG. 14 or the waveform similar to the sawtooth wave shown in FIG. 17B can be generated, It is not always necessary to divide equally. In this case, since it is not necessary to make the moving speed of the X-ray imaging unit 3 constant, various images can be obtained by moving the X-ray imaging unit 3 with a complicated movement.

  In the present embodiment, the image signal processing means 10 synthesizes a tomographic image on a predetermined tomographic plane as a function of the image synthesizing means. However, the present invention is not limited to this. You may make it synthesize | combine the multi-tomographic image which shows the image in a some tomographic plane. This multi-tomographic image can be generated, for example, by a method disclosed in Japanese Patent Laid-Open No. 2006-180944. Note that the function as the image synthesizing unit may be separated from the image signal processing unit 10 and provided separately.

  In the present embodiment, the dental digital panoramic imaging apparatus 1 has been described. However, the present invention is not limited to panoramic imaging, and is not limited to dental X-ray imaging. If an X-ray imaging unit that can move in a direction orthogonal to the incident direction of X-rays that have passed through a predetermined point of the subject is provided, it can be used for general medical purposes. For example, it may be applied to a chest X-ray imaging apparatus for internal medicine. In the present invention, the subject is not limited to the human body, and may be, for example, a naturally occurring object such as a mineral or a product of various industries. In this case, various types of analysis and inspection for damage can be performed.

1 is a configuration diagram schematically illustrating a digital panorama photographing apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the moving direction of the X-ray imaging means shown in FIG. It is explanatory drawing of the X-ray imaging means and the slit which inclined from the moving direction of the X-ray imaging means. It is explanatory drawing which shows an example of the turning drive means shown in FIG. It is a top view of a dentition. It is explanatory drawing which shows typically an example of the X-ray imaging means shown in FIG. FIGS. 2A and 2B are explanatory diagrams of the large-capacity processed image storage unit illustrated in FIG. 1, in which FIG. 1A illustrates the correspondence between the X-ray imaging unit and the memory area, and FIG. 2 is a flowchart showing the operation of the image signal processing means shown in FIG. It is explanatory drawing in order to demonstrate the signal strength received for every time in each pixel. It is a figure which shows a mode that the signal strength shown in FIG. 9 is integrated | accumulated to a memory area in time series. It is explanatory drawing for demonstrating the signal strength integrated | accumulated in a memory area corresponding to the X-ray imaging means shown in FIG. It is a figure which shows the correspondence of the integrated signal intensity | strength shown in FIG. 11, and the arrangement | sequence of a pixel. It is a graph which shows ESF about the integrated signal strength shown in FIG. It is a graph which shows LSF calculated | required from ESF shown in FIG. It is explanatory drawing of LSF shown in FIG. 14, Comprising: (a) is a triangular wave, (b) has each shown the function which carried out the Fourier transform of (a). It is explanatory drawing of LSF shown in FIG. 14, Comprising: (a) is a rectangular wave, (b) has each shown the function which carried out the Fourier transform of (a). It is explanatory drawing of a spatial frequency, Comprising: (a) at the time of a stillness, (b) and (c) have each shown at the time of signal processing. It is a graph which shows MTF calculated | required from LSF shown in FIG.

Explanation of symbols

1 Digital panoramic radiography equipment (X-ray radiography equipment)
2 X-ray source 3 (3a) X-ray imaging means 4 Arm 5 Rotation drive means (drive means)
7 Large-capacity frame image storage means 8 Large-capacity processed image storage means (processed image storage means)
9 All image display storage means 10 Image signal processing means 11 Output means 21a Primary slit 22a Secondary slit

Claims (4)

An X-ray source that irradiates an object with X-rays and a plurality of pixels that receive X-rays that have passed through a predetermined point of the object are two-dimensionally arranged along one axis and the other axis that are orthogonal to each other on the light receiving surface. X-ray imaging means, driving means for moving the X-ray imaging means in a direction orthogonal to the X-ray incident direction, and image signals that generate processed images by processing signals output from the X-ray imaging means An X-ray imaging apparatus comprising processing means and processed image storage means for storing a processed image generated as the signal processing result,
The X-ray imaging means is disposed on the light receiving surface by inclining the arrangement direction of the plurality of pixels along the one axis and the other axis from the moving direction of the X-ray imaging means,
The processed image storage means has a plurality of memory areas corresponding to areas obtained by dividing the pixels finer than the pixel width for each pixel.
The image signal processing means is output from the predetermined pixel within a time during which the predetermined pixel of the X-ray imaging means moves by the pixel width along the one axis as the X-ray imaging means moves. The value of the signal is apportioned according to the moving position of the predetermined pixel along the one axis , integrated in each memory area for the predetermined pixel, and X-rays passing through the predetermined point of the subject said prorated according to the position in the movement along said one axis of the adjacent pixels adjacent along said one shaft to said predetermined pixels that receive the next of the predetermined pixels along said one shaft The value of a signal output from an adjacent pixel along one axis is accumulated in each memory area for the predetermined pixel, and the predetermined pixel of the X-ray imaging unit is moved along with the movement of the X-ray imaging unit. Within the time to move by the pixel width along the other axis Then, the value of the signal output from the predetermined pixel is apportioned according to the moving position of the predetermined pixel along the other axis, and is integrated into each memory area for the predetermined pixel. The X-ray passing through a predetermined point of the subject is moving along the other axis along the other axis and adjacent pixels adjacent to the predetermined pixel receiving the next pixel after the predetermined pixel along the other axis. The processed image is generated by accumulating the values of signals output from adjacent pixels along the other axis in accordance with the positions of the predetermined pixels in each memory area for the predetermined pixels. X-ray imaging device. Each of the X-ray imaging unit side and the X-ray source side sandwiching the subject includes a slit for narrowing the X-rays irradiated to the subject,
Of the slits on the X-ray imaging unit side and the slits on the X-ray source side, at least the direction of the slit on the X-ray imaging unit side is one of the arrangement directions of the pixels on the light receiving surface of the X-ray imaging unit The X-ray imaging apparatus according to claim 1, wherein:   3. The X-ray imaging according to claim 1, wherein the X-ray imaging unit is disposed with an arrangement direction of the pixels inclined by 45 degrees from a moving direction of the X-ray imaging unit. apparatus. An X-ray source that irradiates an object with X-rays and a plurality of pixels that receive X-rays that have passed through a predetermined point of the object are two-dimensionally arranged along one axis and the other axis that are orthogonal to each other on the light receiving surface. X-ray imaging means, driving means for moving the X-ray imaging means in a direction orthogonal to the X-ray incident direction, and image signals that generate processed images by processing signals output from the X-ray imaging means A signal processing method in an X-ray imaging apparatus comprising processing means and processed image storage means for storing a processed image generated as a result of the signal processing,
The X-ray imaging means is disposed on the light receiving surface by inclining the arrangement direction of the plurality of pixels along the one axis and the other axis from the moving direction of the X-ray imaging means,
The processed image storage means has a plurality of memory areas corresponding to areas obtained by dividing the pixels finer than the pixel width for each pixel.
The image signal processing means outputs the predetermined pixel of the X-ray imaging means from the predetermined pixel within a time during which the predetermined pixel of the X-ray imaging means moves along the one axis by the pixel width as the X-ray imaging means moves. The value of the signal is apportioned according to the moving position of the predetermined pixel along the one axis , integrated in each memory area for the predetermined pixel, and X-rays passing through the predetermined point of the subject said prorated according to the position in the movement along said one axis of the adjacent pixels adjacent along said one shaft to said predetermined pixels that receive the next of the predetermined pixels along said one shaft The value of a signal output from an adjacent pixel along one axis is accumulated in each memory area for the predetermined pixel, and the predetermined pixel of the X-ray imaging unit is moved along with the movement of the X-ray imaging unit. Move by the pixel width along the other axis In the meantime, the value of the signal output from the predetermined pixel is apportioned according to the moving position of the predetermined pixel along the other axis, and accumulated in each memory area for the predetermined pixel. Movement along the other axis of the adjacent pixel adjacent to the predetermined pixel that receives the X-ray passing through the predetermined point of the subject along the other axis next to the predetermined pixel along the other axis The processed image is generated by integrating the value of a signal output from an adjacent pixel along the other axis in accordance with a position in the middle, and adding the value to each memory area for the predetermined pixel. Signal processing method.

Images