JP2010178822A - Dental panoramic radiographic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a panoramic image photographed by a CT scanner lacks in clearness as compared with an image photographed by panoramic radiography equipment. <P>SOLUTION: The dental panoramic radiography equipment comprises an X-ray irradiation section 1, an X-ray breaking slit 2, an X-ray receiving section 3 for receiving X-rays coming from the X-ray irradiation instrument and sending strip image data, a rotary arm 4 holding the X-ray irradiation instrument and the X-ray receiving section face to face, a rotation control section 5 for rotating the rotary arm, a strip image processing and holding section 6 performing image processing for the strip image data sequentially sent from the X-ray receiving section and holding it, and a panoramic image generation section 7 for superimposing a plurality of strip images held by the strip image processing and holding section one on top of the other and generating the panoramic image. In the strip image processing and holding section 6, the dental panoramic radiographic equipment can uniformize density differences in the entire strip image by multiplying the longitudinal direction of the strip image by a coefficient, and can prepare a panoramic image in which a dental portion image is clear by image processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to the technical field of a dental panoramic imaging apparatus.

Conventionally, diagnosis using an image taken by an X-ray imaging apparatus has been performed in dental practice. Among them, panoramic photography for photographing the entire tooth is widely performed in order to examine the entire state including the diseased part. This is a method of performing X-ray imaging while rotating an arm that is held so that the X-ray irradiation unit (device) and the light receiving unit are integrally held with the subject interposed therebetween. In this panoramic photography method, a film has been conventionally used, but recently, a filmless / digital photography method using a device sensor such as a CCD is becoming widespread. In this filmless / digital photography, a method called TDI (Time Delay Integration) method is used (see, for example, Patent Document 1). This uses a strip-shaped sensor, and accumulates pixel data of the tooth portion in the sensor width direction by matching the charge transfer speed in the sensor width direction with the arm rotation speed. As a result, only the tooth part image becomes clear and other parts can be blurred. Generally, an X-ray panoramic image is taken using this TDI method.

  On the other hand, using a device sensor with a large area X-ray light receiving surface called FPD (Flat Panel Detector), frame images are obtained by continuously shooting at high speed while the arm rotates around the subject as in panoramic shooting. CT imaging apparatuses that are used for diagnosis as three-dimensional data by performing image processing on a plurality of frame image data are becoming widespread. With this photographing apparatus, it is possible to acquire accurate tooth image data in the depth-height direction, which could not be achieved only by panoramic photographing, and it has contributed greatly to dental practice that has been difficult in the past, such as implants.

  However, there are many points inadequately diagnosing three-dimensional data with a CT imaging apparatus, and diagnosis with panoramic images is still required. However, since both the panoramic imaging apparatus and the CT imaging apparatus are expensive and occupy a large area, an attempt has been made to acquire a panoramic image taken by the panoramic imaging apparatus in the CT imaging apparatus. (For example, see Patent Document 2).

  However, a sensor device used in CT imaging is usually a CMOS type device. A CMOS type device sensor does not have a function of charge transfer, and acquires a frame image by acquiring the charge amount of each pixel at high speed. Therefore, it is not possible to perform photographing by the TDI method used in the panoramic photographing apparatus. Therefore, only a part of the frame image of the FPD is used, and a plurality of strip-like frame images that are read out continuously at high speeds are made to correspond to the rotational speed of the arm and joined while being overlapped by a predetermined distance. In addition, a method of acquiring a panoramic image similar to the TDI method is used.

By the way, in panoramic photography, a shielding material that shields X-rays is provided immediately after the X-ray irradiating unit in order to avoid unnecessary exposure to other than the sensor light receiving unit, and a slit is provided only in a portion that requires X-ray irradiation. Yes. In panoramic photography, there are many parts where X-rays are transmitted from the upper part to the central part of the subject, and when the X-ray irradiation is performed uniformly from the upper part to the lower part of the sensor light receiving part, The ratio of the line distribution is deteriorated, and when image processing is performed as post-processing, the sharpness of the tooth part of the heart becomes insufficient. Therefore, the shape of the slit described above is changed to a shape such as an inverted triangle, and the amount of X-rays received by the lower part is reduced compared to the upper middle part so that the ratio of the X-ray distribution between the tooth part and the lower part is the same. ing. In panoramic photography using the TDI method, images are smoothly connected in the width direction by continuously adding in the width direction even if the width of the sensor light receiving portion is small only in the lower part.
JP-A-8-215191 JP 2008-23241 A

  However, when an inverted triangular slit is provided immediately after the X-ray irradiating unit as in the conventional configuration and panoramic imaging is performed with a CT imaging apparatus, the strip-shaped frame image has X-rays in the area inside the slit. Irradiated and X-rays are not irradiated outside the slit, so an inverted triangular image is taken. In order to combine this strip-shaped image into a panoramic image, if they are joined while being overlapped by a predetermined distance, the timing of shooting and the timing of feeding are constant even though the inverted triangular shape exists smoothly and continuously. Since it is not an interval, the pixel data is superimposed by discontinuous processing, and in the generated panoramic image, the boundary line of the slit is emphasized in some places and appears as vertical stripe noise in the image.

  Therefore, in the CT imaging apparatus, the slit at the time of panoramic imaging is not an inverted triangular shape but a normal rectangular shape. For this reason, the entire sensor light-receiving surface receives transmitted X-rays uniformly, and compared with a panoramic image using the TDI method, the difference in luminance between the tooth part and the lower part is large, and the essential tooth part is subjected to image processing. However, it is difficult to obtain a clear image. As a result, it was lacking in clarity compared with the panoramic image by the TDI method.

  The present application solves the above problem, and even in panoramic imaging with a CT imaging device, the luminance difference of the image data on the light receiving side with respect to the irradiation X-ray dose equivalent to the panoramic image by the conventional TDI method is the entire light receiving surface. In order to obtain an image that is as uniform and clear as possible, that is, in the generated panoramic image, the boundary lines of the slits do not appear as vertical stripe noise in the image, and the entire sensor light receiving surface is evenly transmitted X-rays Accordingly, an object of the present invention is to provide a panoramic photographing apparatus capable of preventing a luminance difference between the tooth part and the lower part from becoming large and obtaining a clear image regarding the essential tooth part.

  In order to solve the conventional problems, a dental panoramic imaging apparatus of the present invention has an X-ray irradiation unit, a strip-shaped light receiving surface including a plurality of pixels, and X-rays from the X-ray irradiation unit. Receives X-rays that are transmitted through the irradiation target and transmits image data of the strip-shaped light receiving surface, and holds the X-ray irradiation unit and the X-ray light receiving unit so as to face each other. A rotation arm, a rotation control unit that rotates the rotation arm according to a predetermined speed pattern, and strip-shaped image data that are sequentially sent out from the X-ray light receiving unit while rotating the rotation arm by the rotation control unit. A panoramic image processing unit that performs image processing on the image and a plurality of strip-shaped images held by the strip-shaped image processing holding unit are shifted by a predetermined distance and overlapped and joined to form a single panorama. Panorama to generate image It is obtained by a image generation unit.

  According to this configuration, even if the slit is not an inverted triangle shape, the density difference (brightness difference) of the entire panoramic image obtained can be made close to the tooth part and the lower part evenly, and the tooth part image is sharpened by image processing. Can be made.

  Furthermore, in the dental panoramic imaging apparatus of the present invention, the strip-shaped image processing unit performs brightness correction processing in the longitudinal direction of the strip-shaped image for uniform X-ray irradiation.

  Further, in the dental panoramic imaging apparatus of the present invention, the strip-shaped image processing unit performs processing by multiplying at least two different coefficients for each pixel.

  Furthermore, in the dental panoramic imaging apparatus of the present invention, in the strip-shaped image processing unit, processing is performed by multiplying the longitudinal direction of the strip-shaped image by the same or a coefficient that changes based on a predetermined rule from one end to the opposite end. .

  Furthermore, in the dental panoramic imaging apparatus of the present invention, in the strip-shaped image processing unit, processing is performed by multiplying the longitudinal direction of the strip-shaped image by a coefficient having a characteristic that changes monotonically with a linear function from one end to the opposite end. Then, a strip-like image is held.

  As described above, according to the present invention, a clear panoramic image similar to that of a conventional panorama apparatus can be obtained in a CT imaging apparatus.

In the following, an embodiment of a dental panoramic imaging apparatus that performs luminance correction in the longitudinal direction of a strip image obtained for uniform X-ray irradiation according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a functional block diagram showing the configuration of a dental panoramic imaging apparatus according to the first embodiment of the present invention.

  Example 1 has an X-ray irradiation unit 1, an X-ray dose adjustment slit 2, and a strip-shaped light receiving surface composed of a plurality of pixels, and X-rays from the X-ray irradiation unit are incident through the irradiation target. An X-ray light receiving unit 3 that receives a line and transmits image data of the strip-shaped light receiving surface, a rotating arm 4 that holds the X-ray irradiating unit and the X-ray receiving unit to face each other, and the rotating arm A rotation control unit 5 that rotates according to a predetermined speed pattern, and a strip-shaped image data that is sequentially sent out from the X-ray light receiving unit while rotating the rotation arm by the rotation control unit, performs image processing and holds it. Panoramic image generation for generating a single panoramic image by superimposing a plurality of strip-shaped images held by the strip-shaped image processing unit 6 by a predetermined distance in a predetermined direction and joining them Part 7.

  FIG. 2 shows an example of the shape of the X-ray dose adjustment slit 2 for adjusting the X-ray dose in the CT panoramic imaging apparatus. In the panoramic radiography apparatus, the X-ray adjustment slit 2 has an inverted triangular shape as shown in FIG. 2 (a). To go. On the other hand, FIG. 2B also shows the X-ray dose adjustment slit 2 used in the CT panoramic imaging apparatus. As in the conventional problem, since the slit boundary portion appears as vertical stripe noise in the superimposed image in the inverted triangular slit, the rectangular slit is used for uniform irradiation. In this embodiment, the slits are provided and the uniform irradiation is performed. However, of course, there is a case where the slits are not provided and the uniform X-ray irradiation is performed.

  FIG. 3 shows an X-ray light receiving unit 3 for sending image data of a strip-shaped light receiving surface. As shown in FIG. 3, an image can be acquired at high speed by acquiring a strip-shaped image using only the central region of the FPD as a light receiving surface. A panoramic image is reconstructed by superimposing the read strip-shaped images.

  FIG. 4 shows the image processing by reducing the luminance difference between the tooth portion and the other portions by performing the luminance correction processing in the strip image processing unit 6 in the longitudinal direction of the strip image (vertical direction in FIG. 1). The flowchart of the operation | movement which produces a panoramic image with a clear tooth part image by is shown.

  First, in step 1, a method of acquiring images at each point on the trajectory by controlling the rotating arm 4 in FIG. The rotation control unit 5 turns the rotary arm 4 on a predetermined track. The subject 9 is irradiated with uniform X-rays from the X-ray irradiation unit 1 through the X-ray dose adjustment slit 2 at each position on the orbit.

  Upon receiving the X-ray transmitted through the subject 9, the X-ray light receiving unit 3 sends strip-shaped image data. FIG. 5A is a simulation diagram of a strip image sent from the X-ray light receiving unit 3 in this embodiment. Since the obtained strip image is uniformly irradiated with X-rays, the transmitted X-ray dose is different between the tooth region in the upper part of the image and the region other than the tooth in the lower part of the image.

  Next, in step 2, the luminance value is corrected by a correction coefficient for the strip image stored in the strip image processing unit 6.

  FIG. 6 shows a change in luminance value when the luminance value of the strip image is multiplied by a correction coefficient, and the right direction of the longitudinal coordinate axis is the lower direction of the strip image. For a strip image in which the luminance value at the lower part of the image is higher than that at the upper and middle part as shown in FIG. 6A, for example, the gain is gradually changed to be smaller in the lower direction of the image as shown in FIG. By setting a simple correction coefficient (for example, a correction coefficient having a characteristic that changes monotonically with a linear function), the luminance value of the strip image is substantially uniform as shown in FIG. Become. FIG. 5B shows a simulation diagram of a strip image subjected to luminance correction in this embodiment. Compared to the strip image before correction (FIG. 5A), the luminance at the bottom of the image is close to the luminance at the top of the image.

  The correction coefficients are at least two types of correction coefficients corresponding to the tooth area in the upper part of the image with little transmitted X-ray and low brightness and the area other than the tooth in the lower part of the image with much transmitted X-ray and high brightness. May be registered and stored in advance, and different correction coefficients may be applied to the tooth region and the region other than the tooth to correct the difference in luminance between the two.

  In step 3, a plurality of strip images subjected to luminance correction are superposed according to the speed at the time of orbit to create one panoramic image. FIG. 7 shows a method for reconstructing a panoramic image. The rotating arm 4 turns on a predetermined trajectory and superimposes strip images photographed at predetermined individual positions in order of photographing time. The amount of shift in the horizontal direction is adjusted in accordance with the turning speed of the rotary arm 4 so that the images of the tooth portions overlap each other without being misaligned.

  In step 4, image processing as post-processing is performed on the created panoramic image. For example, noise removal and contrast enhancement. The panorama image after the image processing is displayed on the image display 8. FIG. 8 shows a panoramic image in the present embodiment. FIG. 9 is a panoramic image taken by a conventional CT panorama apparatus shown for comparison. Since there is an excessive dose area at the lower part of the image, the contrast of the tooth area is insufficient in the image after image processing. On the other hand, FIG. 8 is an image reconstructed in the present embodiment. Since the excessive dose area at the bottom of the image is corrected by the correction coefficient, post-processing image processing is effectively performed, and the tooth area is displayed. Sufficient contrast is obtained.

  As described above, in the panoramic imaging device of the present invention, in the generated panoramic image, the boundary line of the slit does not appear in the image as vertical stripe noise, and the entire sensor light receiving surface receives the transmitted X-rays uniformly. Thus, it is possible to prevent the brightness difference between the tooth part and the lower part from increasing, and to obtain a clear image regarding the essential tooth part.

  Although the present embodiment has been described with the characteristic that the correction coefficient is reduced by a linear function at the time of luminance correction, it is not specific to it.

  The dental panoramic imaging apparatus according to the present invention is useful in the technical field of a dental panoramic imaging apparatus and the like because a CT panoramic apparatus can obtain a clear panoramic imaging image similar to a conventional panoramic apparatus.

Functional block diagram of the dental panoramic imaging apparatus according to Embodiment 1 of the present invention. (A) Embodiment 1 of the present invention and a diagram showing an inverted triangular slit for X-ray dose adjustment in the prior art (b) A diagram showing a rectangular slit The figure which shows the sensor use area | region in Embodiment 1 of this invention. Flowchart of panoramic image creation method according to Embodiment 1 of the present invention (A) Simulation diagram of an acquired strip image before luminance correction in Embodiment 1 of the present invention (b) Simulation diagram of an acquired strip image after luminance correction (A) A figure of a strip image in which the luminance value at the lower part of the image is higher than that at the upper middle part (b) A figure showing a correction coefficient for correcting the gain to be smaller in the lower part of the image (c) After the luminance correction, Explanatory drawing showing that the luminance value is almost uniform The figure which showed the reconstruction method of the panoramic image in Embodiment 1 of this invention Explanatory drawing of reconstructed panoramic image in Embodiment 1 of the present invention Explanatory diagram of a configured panoramic image taken with a conventional CT panoramic device

DESCRIPTION OF SYMBOLS 1 X-ray irradiation part 2 X-ray dose adjustment slit 3 X-ray light-receiving part 4 Rotating arm 5 Rotation control part 6 Strip image processing part 7 Panorama image generation part 8 Image display display 9 Subject

Claims (5)

An X-ray irradiation unit;
It has a strip-shaped light receiving surface composed of a plurality of pixels, and X-rays from the X-ray irradiator receive X-rays that pass through the irradiation target and receive image data of the strip-shaped light receiving surface. An X-ray detector;
A rotating arm that holds the X-ray irradiation unit and the X-ray light receiving unit so as to face each other;
A rotation control unit that rotates the rotating arm according to a predetermined speed pattern;
A strip-shaped image processing unit that performs image processing on and holds strip-shaped image data sequentially sent from the X-ray light receiving unit while rotating the rotating arm by the rotation control unit;
A panoramic image generating unit that generates a single panoramic image by shifting and joining a plurality of strip-shaped images held by the strip-shaped image processing holding unit by a predetermined distance;
Panoramic imaging device for dental use.   The dental panoramic imaging apparatus according to claim 1, wherein the strip-shaped image processing unit performs brightness correction processing in a longitudinal direction of the strip-shaped image with respect to uniform X-ray irradiation.   The dental panoramic imaging apparatus according to claim 2, wherein the strip-shaped image processing unit performs processing by multiplying at least two different coefficients for each pixel.   4. The strip-shaped image processing unit performs processing by multiplying a coefficient that changes based on the same or predetermined rule from one end portion in the longitudinal direction of the strip-shaped image to the opposite end portion. Dental panoramic radiography equipment. The strip-shaped image processing holding unit performs a process of multiplying a coefficient having a characteristic that changes monotonically with a linear function from one end in the longitudinal direction to the opposite end of the strip-shaped image. 4. Dental panoramic imaging apparatus according to 4.