JP2005326260A - X-ray imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fluoroscopic image of high resolving power without changing the distance between an X-ray source and a specimen or the distance between the X-ray source and an X-ray detector. <P>SOLUTION: This X-ray imaging apparatus is equipped with the X-ray source 21 for irradiating the specimen S with X-rays, the X-ray detector 3 for acquiring the fluoroscopic image of the specimen S due to X-rays emitted from the X-ray source 21, a control part 4 which performs control for shifting the X-ray detector 3 at a pitch smaller than one pixel quantity of the X-ray detector 3 to acquire a plurality of fluoroscopic images and an image processing part 5 for using the pixel data of a plurality of the fluoroscopic images taken in by the X-ray detector 3 by the control of the control part 4 to form pixel data at a pitch smaller than one pixel quantity of the X-ray detector 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an X-ray imaging apparatus that acquires a transmission image of a subject by irradiating the subject with X-rays.

  In a conventional X-ray CT (Computerized Tomography) imaging apparatus, in order to obtain a high-resolution fluoroscopic image and cross-sectional image, the fluoroscopic image is taken at an increased magnification. In order to increase the enlargement factor, it is necessary to shorten the distance between the X-ray source and the subject when the distance between the X-ray source and the X-ray detector is constant. On the other hand, if the distance between the X-ray source and the subject is constant, it is necessary to increase the distance between the X-ray source and the X-ray detector (see Patent Document 1 and Patent Document 2).

JP 2003-202303 A JP 2003-240733 A

  However, in the method for obtaining a high-resolution fluoroscopic image by adjusting the distance between the X-ray source and the subject and the distance between the X-ray source and the X-ray detector as described above, for example, if the subject is large, the subject There is a physical limit to approaching the X-ray source. Furthermore, moving the X-ray detector away from the X-ray source requires an increase in the outer shape of the apparatus and increases the distance from the X-ray source to the X-ray detector, so that the image quality of the same transmission image can be obtained with the same exposure time. There arises a problem that the line intensity for obtaining the value must be the square of the increased ratio. Alternatively, if such an X-ray intensity cannot be obtained, the exposure time must be increased.

  For example, in order to photograph the solder state on the board for confirmation, the X-ray intensity must be increased due to the characteristics of the solder. At this time, taking a long distance between the X-ray detector and the X-ray source in order to increase the resolution leads to insufficient X-ray intensity, and a desired transmission image cannot be obtained. Therefore, this is dealt with by increasing the exposure time, but in this case, the influence of noise may be increased accordingly.

  In addition, in order to obtain a cross-sectional image by X-rays, it is necessary to take in a plurality of fluoroscopic images, which is very time consuming. That is, if the X-ray intensity is the same when the distance is doubled, the imaging takes four times longer. For example, if the number of multi-directional shots is 360, it takes 6 minutes to shoot in 1 second per frame, and if the distance is doubled as described above, it takes 4 times 24 minutes. Since a lot of time is required in this way, there arises a problem that it is not possible to take a picture with a desired resolution in a limited time.

  The present invention has been made to solve such problems. That is, the present invention relates to an X-ray source that irradiates an X-ray toward the subject, an X-ray detection unit that acquires a fluoroscopic image on the subject by the X-rays emitted from the X-ray source, and an X-ray detection unit Control means for performing control to acquire a plurality of fluoroscopic images by shifting at a pitch smaller than one pixel, and X-ray detection means using pixel data of a plurality of fluoroscopic images captured by the X-ray detection means under the control of the control means And an image processing means for generating pixel data at a pitch smaller than one pixel.

  In the present invention as described above, a plurality of fluoroscopic images are acquired by shifting at a pitch smaller than one pixel of the X-ray detection unit, and pixels having a pitch smaller than one pixel of the X-ray detection unit are obtained using the plurality of image data. Since data is generated, a high-resolution fluoroscopic image can be obtained even if the distance between the X-ray source and the subject or the distance between the X-ray source and the X-ray detector is constant.

  Therefore, according to the present invention, it is possible to increase the resolution of the fluoroscopic image even if there are restrictions due to the X-ray intensity, the X-ray detector, and the position of the subject. Further, even if the X-ray intensity is constant, a fluoroscopic image and a cross-sectional image can be obtained in half the theoretical time. In addition, since the distance between the X-ray source and the X-ray detector can be halved with the same resolution, the outer shape of the apparatus can theoretically be halved to capture an image with the same resolution. In addition, it is not necessary to reduce the size of the subject itself in order to increase the magnification. In addition, the influence of noise can be suppressed, and a high-quality, high-resolution fluoroscopic image and cross-sectional image can be obtained efficiently and in a short time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for explaining an X-ray imaging apparatus according to the present embodiment. That is, the X-ray imaging apparatus 1 of the present embodiment includes an X-ray generation apparatus 2 including an X-ray source 21 that irradiates an X-ray toward the subject S, and an X-ray subject irradiated from the X-ray source 21. An X-ray detector 3 for acquiring a fluoroscopic image at S, a control unit 4 for controlling the position of the X-ray generator 2 and the subject S, the X-ray detector 3 and image processing, and the X-ray detector 3 The image processing unit 5 that performs predetermined image processing using the image data of the fluoroscopic image acquired in step 1 and the monitor 6 that outputs the result of the image processing are provided.

  The X-ray generator 2, the subject S, and the X-ray detector 3 are mounted on slide tables ST1, ST2, and ST3, respectively, and are movable along the X-ray emission direction. The magnification of the fluoroscopic image can be changed by changing these arrangements under the control of the control unit 4. Further, the subject S is arranged via a rotary table RT provided on the slide table ST2, and the subject S can be rotated when performing CT (Computerized Tomography) imaging together with linear movement on the slide table ST2. ing. The subject S can be rotated at a multi-division pitch by the control unit 4 controlling the rotary table RT.

  Further, the X-ray detector 3 is attached via an XY moving table 31 provided on the slide table ST3. Thereby, the X-ray detector 3 can perform movement along the X-ray irradiation direction by the slide table ST3 and movement in a plane (XY plane) orthogonal to the X-ray irradiation direction by the XY movement table 31. The XY plane movement of the X-ray detector 3 is also performed by the control unit 4 controlling the XY movement table 31.

  FIG. 2 is a schematic diagram for explaining the enlargement ratio of the fluoroscopic image by the X-ray imaging apparatus. Here, when the distance between the X-ray source 21 and the subject S is FOD and the distance between the X-ray source 21 and the X-ray detector 3 is FDD, the enlargement ratio is determined by FDD / FOD. Therefore, when making the FDD constant, the enlargement ratio can be increased by reducing the FOD by bringing the subject S closer to the X-ray source 21. On the other hand, when the FOD is made constant, the enlargement ratio can be increased by increasing the FDD by moving the X-ray detector 3 away from the X-ray source 21.

FIG. 3 is a schematic diagram for explaining the relationship between the distance from the X-ray source and the X-ray intensity. Here, the X-ray intensities IA and IB at the positions A and B with respect to the position O of the X-ray source are shown. In this case, the X-ray intensity is inversely proportional to the square of the distance from the X-ray source. That is, the distance from the X-ray source position O to the A position is OA, the distance from the X-ray source position O to the B position is OB, and the X-ray intensity at the A position is IA and B positions. When the X-ray intensity is IB, IA / IB = (OB / OA) ² is established.

  Therefore, conventionally, if the distance between the X-ray source 21 and the X-ray detector 3 is increased in order to increase the resolution, the X-ray intensity becomes insufficient and a desired transmission image cannot be obtained. Therefore, the exposure time is increased to cope with this, but in that case, the influence of noise is considered to be increased accordingly. The present embodiment is characterized in that a high-resolution fluoroscopic image can be obtained without taking a long distance between the X-ray source 21 and the X-ray detector 3.

  As described above, in order to obtain a high-resolution fluoroscopic image without increasing the distance between the X-ray source 21 and the X-ray detector 3, the fluoroscopic image of the subject S is smaller than one pixel of the X-ray detector 3. A plurality of fluoroscopic images shifted by the pitch are acquired, and image data having a pitch smaller than one pixel is synthesized by the image processing unit 5 from the plurality of fluoroscopic images.

  Specifically, X-rays are irradiated from the X-ray source 21 of the X-ray generator 2 toward the subject S, a fluoroscopic image is acquired by the X-ray detector 3, and is sent to the image processing unit 5. The image processing unit 5 stores the fluoroscopic image (referred to here as fluoroscopic image (1)). Next, the X-ray detector 3 is moved by a pitch (for example, 1/2 pixel) smaller than one pixel in each of the XY directions by the XY movement table 31, and a fluoroscopic image of the subject S is acquired in this state to obtain an image. The data is sent to the processing unit 5. The image processing unit 5 stores the fluoroscopic image (referred to here as fluoroscopic image (2)).

  Next, the image processing unit 5 receives pixel data in a pixel area of a portion where pixels at corresponding positions of the perspective image (1) and the perspective image (2) overlap each other, and a plurality of pixels constituting the pixel region of the overlapping portion. It calculates | requires by calculation using the pixel data of a pixel.

  FIG. 4 is a schematic diagram for explaining calculation of pixel data. Here, 5 × 5 25 pixels are taken as an example for the perspective image (1) and the perspective image (2), and the perspective image (2) is half of one pixel in each of the X direction and the Y direction with respect to the perspective image (1). Assume that (1/2 pixel) is shifted. In this case, for example, the second pixel A along the X direction from the upper left of the perspective image (1) and the second pixel A along the Y direction overlap with the corresponding pixel B of the perspective image (2). The pixel data I3 of the pixel area C to be obtained can be obtained by interpolation between the pixel data I1 of the pixel A and the pixel data I2 of the pixel B. For example, when linear interpolation is used, it is obtained from I3 = (I1 + I2) / 2. If such an operation is obtained from the pixel data of the two corresponding pixels in the perspective images (1) and (2), pixel data having twice the resolution in each of the XY directions with respect to the resolution of the X-ray detector is obtained. Can be obtained.

  Next, the difference in photographing between this embodiment and the prior art will be specifically described. When the FOD shown in FIG. 2 is 10 mm, the FDD is 1000 mm, the magnification is 100 times, and the distance of the FDD from the size of the subject S cannot be further reduced. An imaging method for obtaining double resolution in the vertical and horizontal directions (XY direction) from the condition where the exposure time is T is as follows.

(Conventional technology)
Change the FDD from 1000mm to 2000mm and take a picture. In this case, the intensity of the X-ray reaching the X-ray detector is I / 4 from the inverse square law. Therefore, the exposure time is set to 4T. The shooting time is quadrupled.

(This embodiment)
The conditions such as FDD, FOD, X-ray intensity I, and exposure time T are all the same. Two images are taken, one with the X and Y directions of the X-ray detector shifted by half a pixel, and the other with the image taken without shifting. Therefore, the shooting time is doubled. From the above, a high-resolution cross-sectional image can be obtained efficiently and in half the time compared to the prior art. Further, FDD greatly affects the external shape of the apparatus, and when the FDD cannot be increased any longer, the subject cannot be made smaller and the resolution cannot be increased except by shortening the FOD. Absent.

  In the above example, the fluoroscopic image (1) and the fluoroscopic image (2) are photographed with a half pixel shift, but the pitch (for example, 1/3) smaller than the one pixel of the X-ray detector 3 is taken. If a plurality of images are taken while being shifted by a pixel or a ¼ pixel and the same calculation is performed, it becomes possible to obtain pixel data with higher resolution.

  In addition, in order to capture a CT image with the X-ray imaging apparatus 1 of the present embodiment, a plurality of rotary tables RT on which the subject S is mounted are rotated in multiple divisions and the pixels as described above are shifted at each angle. The calculation is performed by fetching one image. This makes it possible to construct a high-resolution CT image.

It is a schematic diagram explaining the X-ray imaging device which concerns on this embodiment. It is a schematic diagram explaining the magnification rate of the fluoroscopic image by an X-ray imaging device. It is a schematic diagram explaining the relationship between the distance from an X-ray source, and X-ray intensity. It is a schematic diagram explaining the calculation of pixel data.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... X-ray imaging device, 2 ... X-ray generator, 3 ... X-ray detector, 4 ... Control part, 5 ... Image processing part, 6 ... Monitor, 21 ... X-ray source, 31 ... XY movement table

Claims (6)

An X-ray source that irradiates the subject with X-rays;
X-ray detection means for acquiring a fluoroscopic image of the subject by X-rays emitted from the X-ray source;
Control means for performing control to obtain a plurality of fluoroscopic images by shifting at a pitch smaller than one pixel of the X-ray detection means;
Image processing means for generating pixel data at a pitch smaller than one pixel of the X-ray detection means using pixel data of a plurality of fluoroscopic images captured by the X-ray detection means under the control of the control means. A featured X-ray imaging apparatus. The X-ray imaging apparatus according to claim 1, further comprising a moving unit that moves the X-ray detection unit on a plane orthogonal to the X-ray irradiation direction. The X-ray imaging apparatus according to claim 1, further comprising a rotary table that rotates the subject. The image processing means obtains the pixel data in a pixel area of a portion where pixels corresponding to the plurality of fluoroscopic images overlap with each other by an interpolation operation using pixel data of a plurality of pixels constituting the pixel area of the overlapping portion. The X-ray imaging apparatus according to claim 1. The X-ray imaging apparatus according to claim 3, wherein the control unit performs control so that the rotary table is set for each predetermined angle and a fluoroscopic image of the subject is acquired from different angles. The control means controls the acquisition of the fluoroscopic image of the subject from different angles by setting the rotary table for each predetermined angle,
The X-ray imaging apparatus according to claim 3, wherein the image processing unit performs a process of generating a cross-sectional image of the subject from a perspective image of the subject acquired from a different angle under the control of the control unit. .

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