JPH04210049A - X-ray tomographic photographing method and apparatus therefor - Google Patents

Abstract

PURPOSE:To enable the heightening of a through put while obtaining a better quality of picture with limited exposure dose by synthesizing data in directions obtained with the scanning of a roughly sector X-ray beam along a section surface as being shifted by a value corresponding to the section surface to obtain image information of the section surface. CONSTITUTION:Radial X rays generated form an X-ray tube 2 pass through slits 3a, 3b, 3c, 3d and 3e to form five roughly sector beams. After being transmitted through an object M to be inspected, the roughly sector X-ray beams are detected with linear X-ray detectors 4a, 4b, 4c, 4d and 4e, respectively. Image information obtained with the X-ray detectors 4a, 4b, 4c and 4d is sent to an image information processing section 1b passing through a line provided at each of the X-ray detectors 4a, 4b, 4c, 4d and 4e. Parallel pitches of slits 3a, 3b, 3c, 3d and 3e and the X-ray detectors are set according to an angle of photographing. Thus, the object M to be inspected receives the irradiation of the five roughly sector X-ray beams alone intermittently, thereby eliminating the effect of a magnetic field otherwise received during the photographing with a significant drop in the exposure dose.

Description

[Detailed description of the invention]

[0001]

[Field of Industrial Application] The present invention relates to an X-ray tomography method and apparatus, and more particularly to an X-ray tomography method in which a substantially fan-shaped X-ray beam is detected by a substantially linear X-ray detection means. METHODS AND APPARATUS. [0002]

2. Description of the Related Art When an abnormal shape is detected in a plain chest X-ray examination, the subject is then subjected to an X-ray tomography examination. An X-ray tomography device is used at this time. [0003] The imaging principle of a conventional X-ray tomography device is shown in Figure 4.
The explanation will be based on. In a conventional X-ray tomography apparatus, the subject is positioned between the X-ray tube 2 and the X-ray film F, the X-ray tube 2 is moved in the direction of arrow a, and the X-ray film F is moved between the X-ray tube 2 and the X-ray film F. While moving in the opposite direction of the arrow, irradiate X-rays and take pictures. [0004] Considering an X-ray beam passing through a point A on the tomographic plane P directly below the X-ray tube 2, the X-ray beam passes through the subject and reaches a point B on the film P directly below the point A. irradiate. When the X-ray tube 2 moves in the direction of arrow a, the X-ray beam passing through point A irradiates point B1 on the film P, and the X-ray tube 2
As it moves further, point B2 on the film P is irradiated. Therefore, if the film F is moved at the same speed as the X-ray beam moving on the film P, the points Bl and B2
are multiple Xs that overlap point B and pass through point A in different directions
The line beam always illuminates the same point B on the film P. [0005] On the other hand, in FIG. 4, multiple Xs passing through a point vertically away from point A, for example point C, in different directions
The line beam is dispersed and irradiated over a wide area of the film F. Therefore, only the image information at point B is clearly recorded with high density on the film P, and the image information at other points is recorded in a blurred manner. [0006] The same applies to the X-ray beam passing through other points on the tomographic plane P, so if imaging is performed while moving the X-ray tube 2 and film F as described above,
An image of the tomographic plane P along the moving direction can be obtained. [00071 FIG. 5 schematically shows an image obtained by the above-mentioned conventional X-ray multistage tomography apparatus. Figure 5(a)(c)
) is a graph showing images taken by a continuous method of continuously irradiating X-rays and changes in image density. The central part ■mO, which shows the image information of a point on the tomographic plane P, has a high density and is clear, but the density decreases continuously as you move away from the central part ImO, and the point with the maximum distance from the tomographic plane P At both ends Im1 indicating image information, the image is blurred. [00081 When imaging is performed using the pulse method in which X-rays are irradiated in a pulsed manner, the images are shown in FIGS. 5(b) and 5(d). This case differs from the continuous method in that the image density decreases stepwise, but the rest is the same. In addition,
When photographing different tomographic planes, the moving speeds of the X-ray tube 2 and the X-ray film F may be adjusted as appropriate. [0009]

[Problem to be Solved by the Invention] When obtaining a plurality of tomographic images using the above conventional X-ray tomography apparatus, there is a limit to the sensitivity of the intensifying screen of the film F, and it is difficult to obtain the optimum density for all the necessary tomographic planes. Since it is difficult to do so, it is necessary to perform multiple imaging operations while changing imaging conditions such as X-ray intensity. For this reason, there is a problem that not only the radiation dose to the subject increases, but also the imaging takes a long time, making it impossible to increase the throughput. CR (Computed Radiography) using an imaging plate instead of film F
In this case, the above problem of changing the imaging conditions is solved, but there is still the problem that imaging is performed multiple times, and the influence of scattered X-rays becomes stronger, resulting in deterioration of image quality. [00101] Therefore, an object of the present invention is to provide an X-ray tomography apparatus that can obtain good image quality with a small exposure dose and can increase throughput. [00111

[Means for Solving the Problems] The X-ray tomography method of the present invention is configured to detect substantially fan-shaped X-ray beams in different directions using substantially linear X-ray detection means, and
A ray beam is scanned along the tomographic plane to obtain data in each direction using the X-ray detection means, and the obtained data in each direction is shifted by an amount corresponding to the tomographic plane and synthesized to create an image of that tomographic plane. Its structural feature is to obtain information. [0012] The X-ray tomography apparatus of the present invention includes an X-ray beam generating means for generating substantially fan-shaped X-ray beams in different directions, and a substantially linear X-ray detecting means for detecting the substantially fan-shaped X-ray beam. , an X-ray beam scanning means for scanning the substantially fan-shaped X-ray beam along the tomographic plane, and data for synthesizing data obtained in different directions by the X-ray detection means by shifting the data by an amount corresponding to the tomographic plane. Its structural feature is that it comprises a processing means and an image recording means for recording a tomographic image based on the image information obtained by the data processing means. [0013] [Operation] In the X-ray tomography method and apparatus of the present invention. A substantially linear X-ray detection means is configured to detect substantially fan-shaped X-ray beams in different directions, and these X-ray beams are scanned along a tomographic plane to obtain data in each direction. Therefore,
The dose to which the subject is exposed is lower than when a radial X-ray beam is used. Furthermore, if data in each direction is obtained, any tomographic image can be generated using the data, so it is possible to increase throughput. In addition, since a substantially fan-shaped X-ray beam is used, the radial
There are fewer scattered X-rays than in the case of a ray beam, and since detection is performed using a substantially linear X-ray detection means, the influence of scattered X-rays is less likely. Therefore, good image quality can be obtained. [0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that this invention is not limited to this. [00151 FIG. 1 is an explanatory diagram showing the configuration of an X-ray tomography apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of its image information processing section. [0016] The X-ray tomography apparatus 1 of the present invention includes an X-ray irradiation/detection section 1a, an image information processing section 1b, and an image memory IC.
and an image recording section 1d. [0017] The X-ray irradiation/detection section 1a includes an X-ray tube 2 and a
The multi-slit collimator 3 has five linear slits 3a, 3b, 3c, 3d, and 3e, and five linear X-ray detectors 4a, 4b, 4c, 4d, and 4e. The X-ray irradiation/detection section 1a can be moved up and down by a moving device (not shown). [0018] Slits 3a, 3b, 3c,
3d and 3e are both arranged horizontally and are vertically arranged in parallel at regular intervals. X-ray detectors 4a, 4b
, 4c, 4d, 4e also have slits 3a, 3b, 3
Similar to c, 3d, and 3e, they are arranged horizontally and vertically arranged at equal intervals. Each X-ray detector 4a, 4b, 4c
, 4d, and 4e are maintained in the same positional relationship even when moving. [0019] Radial X-rays generated from the X-ray tube 2 pass through each slit 3a, 3b, 3c, 3d, and 3e to form five substantially fan-shaped beams. These approximately fan-shaped X-ray beams are
After passing through the subject M, linear X-ray detectors 4a and 4b
, 4c, 4d, and 4e, respectively. Image information obtained by the X-ray detectors 4a, 4b, 4c, 4d, and 4e is sent to the image information processing section 1b through lines provided for each of the X-ray detectors 4a, 4b, 4c, 4d, and 4e. It will be done. [00203 The parallel pitch of the slits 3a, 3b, 3c, 3d, 3e and the X-ray detectors 4a, 4b, 4c, 4d, 4e is set according to the imaging angle. In this example,
Since tomography is to be performed at 30 degrees, the slit 3 should be positioned so that it falls within a 30 degree central angle above and below the X-ray tube 2.
a, 3b, 3c, 3d, 3e and X-ray detectors 4a, 4
b, 4c, 4d, and 4e are arranged. Accordingly, each x-ray beam, in order from the top x-ray beam downward, is +15 degrees relative to the horizontal plane, +7. 5 degrees, 0 degrees. The subject M is irradiated at an angle of 7.5 degrees and -15 degrees. [0021] The image information processing unit 1b includes five A/D converters 5a, 5b, 5c, 5d, and 5e, and five buffers 6.
a, 6b, 6c, 6d, 6e, five address shifters 7a, 7b, 7c, 7d, 7e, and address control device 8.
, a data synthesis device 9, and an image processing device 10. [0022] A/D converters 5a, 5b, 5c
, 5d, 5e are X-ray detectors 4a, 4b, 4c
, 4d, 4e are converted into digital data, buffers 6a, 6b, 6c, 6d, 6
Enter each in e. Buff y6a, 6b, 6c, 6
d and 6e store the digital data. [0023] When the subject M is scanned once with the five substantially fan-shaped X-ray beams, the buffers y6a, 6b, 6c,
Data in five different directions is digitized and stored in 6d and 6e. That is, the X-ray detector 4
Since a always detects the X-ray beam in the direction of +15 degrees, data in the direction of +15 degrees is stored in the buffer 6a. Since the X-ray detector 4b always detects the X-ray beam in the direction of +7.5 degrees, data in the direction of +7.5 degrees is stored in the buffer 6b. Similarly, other buffer 6
c, 6d, and 6e have 0 degrees, −7, 5 degrees, and −, respectively.
Data for the 15 degree direction is stored. [0024] The address control device 8 assigns an address value (for example, 1
．． 2. ......, input M). The address value entered at each time is the same, and the address value is incremented or decremented over time. [0025] Address shifters 7a, 7b, 7c
, 7d. 7e sends a control signal to each buffer 6a, 6b, and 7e to shift the address value by a preset shift amount when the address value is input from the address control device 8.
Send to 6c, 6d, 6e. Each buffer y6a, 6b,
6c, 6d. 6e shifts the address as appropriate in response to this control signal, and inputs the data stored at the shifted address to the data synthesis device 9. [0026] For example, each address shifter 7a, 7b
, 7c, 7d, and 7e shift amounts are Na and N, respectively.
b, Nc, Nd, Ne, and if the address value input from the address control device 8 is M, then the address values output by each address shifter 7a, 7b, 7c, 7d, and 7e are (M+Na), respectively. , (M+Nb),
(M+Nc), (M+Nd), (M+Ne)
becomes. Therefore, each buffer 6a, 6b, 6c, 6d,
6e reads data corresponding to these address values and inputs it to the data synthesis device 9. [0027] The data synthesis device 9 has buffers 6a and 6b.
, 6c, 6d, and 6e are combined and sent to the image processing device 10. [0028] The image processing device 10 generates image information of a desired tomogram based on the combined data. The image recording unit 1d records a tomographic image on the X-ray film based on the generated image information. The image memory 1c stores generated image information. [0029] Next, the operation of the X-ray tomography apparatus 1 having the above configuration will be explained with reference to FIG. In Figure 3,
Five approximately fan-shaped X-ray beams each have +
15 degrees, +7. 5 degrees, 0 degrees, -7, 5 degrees, -15
It is assumed that the tomographic plane to be imaged is a plane Q along the body axis of the subject M. [00301 FIG. 3(a) shows the timing at the start of imaging (time T=to
) shows the X-ray irradiation state. In this state, among the five substantially fan-shaped X-ray beams, the uppermost X-ray beam passes through a horizontal straight line within the tomographic plane Q. Therefore, at time T=tO, the X-ray detector 4a obtains image data in the +15 degree direction on the horizontal line. [00311 In FIG. 3(b), from the state in FIG. 3(a),
The state when the radiation irradiation/detection unit 1a is moved upward along the body axis of the subject M (time T=tl) is shown. The distance traveled is
It is equal to the distance on the tomographic plane Q between the highest X-ray beam and the second X-ray beam from the highest. In this state, the second X-ray beam from the top passes through the horizontal straight line, so at time T=tl, the X-ray detector 4b obtains image data in the +7.5 degree direction on the horizontal straight line. It will be done. [00321 FIG. 3(c) shows the state when the X-ray irradiation/detection section 1a is further moved upward from the state of FIG. 3(b) (time T=
t2). The distance traveled is the second from the top
It is equal to the distance on the tomographic plane Q between the ray beam and the central X-ray beam. In this state, the central X-ray beam passes along a horizontal straight line within the subject M, so at time T=t2, horizontal image data on the horizontal straight line is obtained by the X-ray detector 4C. [00331 FIG. 3(d) shows the state when moving further upward from the state of FIG. 3(C) (time T=t3). The moving distance is equal to the distance on the tomographic plane Q between the central X-ray beam and the second lowest X-ray beam. In this state,
Since the second X-ray beam from the bottom passes along the horizontal straight line, at time T=t3, the X-ray detector 4d obtains image data in a direction of -7.5 degrees above the horizontal straight line. [00341 FIG. 3(e) shows the state when the state is further moved upward from the state of FIG. 3(d) (time T=t4). The moving distance is equal to the distance on the tomographic plane Q between the second lowest X-ray beam and the lowest X-ray beam. In this state, the lowest X-ray beam passes along the horizontal line, so at time T=t4, the X-ray detector 4e obtains image data in a direction of 115 degrees on the horizontal line. [0035] Therefore, the image data of the X-ray detector 4a at time T=tO, the image data of the X-ray detector 4b at time T=tl, and the image data of the X-ray detector 4C at time T=t2, If the image data of the X-ray detector 4d at time T=t3 and the image data of the X-ray detector 4e at time T=t4 are synthesized by the data synthesis device 9, an image on a horizontal straight line can be obtained. . [0036] Such an image is processed by the image information processing section 1b.
To obtain the image data at time T=tO in the buffer 6a, from the address where the image data at time T=tO is stored in the buffer 6b,
From the address where the image data of t1 was stored, buffer 6
The image data is stored in C from the address where the image data at time T=t2 is stored, in the buffer 6d from the address where the image data at time T=t3 is stored, and in the buffer 6e from the address where the image data at time T=t4 is stored. To be read, each address shifter 7a, 7b
, 7c, 7d, and 7e may be set. [0037] Images on other horizontal straight lines in the tomographic plane Q are obtained in the same way as in the case of horizontal straight lines, so in the end, the image of the tomographic plane Q is obtained by the above-mentioned one scan. . Note that if it is desired to obtain an image of a tomographic plane other than the tomographic plane Q, the address value output by the address control device 8 or the address shift value of the address shifters 7a, 7b, 7c, 7d, and 7e may be changed. [0038] According to the X-ray tomography apparatus 1, the subject M is only intermittently irradiated with five approximately fan-shaped X-ray beams, so the exposure dose is significantly greater than in conventional continuous imaging methods. decreases to In addition, since X-rays are irradiated in a substantially fan-shaped beam, the signal strength relative to the exposure dose is greater compared to the conventional equipment described above, which has the advantage of being resistant to electrical system noise, as well as reducing the amount of scattered X-rays. I can do it. Furthermore, by using, for example, a semiconductor X-ray detector as the X-ray detector, it is possible to avoid being influenced by a magnetic field during imaging. [00391 In the embodiments described above, 5
A roughly fan-shaped X-ray beam is generated to obtain image information in five different directions in one scan, but one roughly fan-shaped X-ray beam is generated and the irradiation angle is changed to scan five times. You may also do so. [00401] [Effects of the Invention] According to the X-ray tomography method and apparatus of the present invention, it is possible to obtain good image quality with a small radiation dose and to increase throughput.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an X-ray irradiation/detection section of an X-ray tomography apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of an image information processing section of the X-ray tomography apparatus.

FIG. 3 is an explanatory diagram showing the imaging principle of the X-ray tomography apparatus.

FIG. 4 is a conceptual diagram showing the imaging principle of a conventional X-ray tomography apparatus.

[Fig. 5] Graphs showing images obtained with the conventional X-ray tomography device in Fig. 4 and their density changes. This is the case when the photo was taken with .

[Explanation of symbols]

I X-ray tomography device la X-ray irradiation/detection section ■b Image information processing section 1c Image memory 1d Image recording section 2 X-ray tube 3 Multi-slit collimator 3a, 3b, 3c, 3d, 3e Slit 4a, 4b, 4c , 4d, 4e X-ray detector 5
a, 5b, 5c, 5d, 5e A/D converter 6a, 6
b, 6c, 6d, 6e buffers 7a, 7b, 7c,
7d, 7e Address shifter 8 Address control device 9 Data synthesis device 10 Image processing device M Subject Q Tomographic plane

[Figure 3]

[Procedural amendment]

[Submission date] December 11, 1990

[Procedural amendment 1]

[Name of item to be corrected] Drawing

[Correction target item name] All diagrams

[Correction method] Change

[Correction details]

[Figure 3A]

Claims (2)

[Claims] 1. Approximately fan-shaped X-ray beams having different directions are detected by approximately linear X-ray detection means, and the approximately fan-shaped X-ray beam is scanned along a tomographic plane to detect the X-rays. An X-ray tomography method characterized in that data in each direction is obtained by a detection means, and the obtained data in each direction is shifted by an amount corresponding to the tomographic plane and synthesized to obtain image information of the tomographic plane. 2. X-ray beam generating means for generating substantially fan-shaped X-ray beams having different directions; substantially linear X-ray detecting means for detecting said substantially fan-shaped X-ray beam; and said substantially fan-shaped X-ray beam. X-ray beam scanning means for scanning a beam along a tomographic plane; data processing means for synthesizing data obtained in different directions by the X-ray detection means by shifting the data by an amount corresponding to the tomographic plane; and the data processing means. 1. An X-ray tomography apparatus comprising: an image recording means for recording a tomographic image based on image information obtained in the X-ray tomography apparatus.