JPH08154925A - Radiation three-dimensional image camera - Google Patents

Abstract

PURPOSE: To enable the obtaining of a radiation three-dimensional image of a large object by dividing a visible light image on a fluorescent screen in two in the direction at right angles to the center axis of rotation of a rotating means to detect visible images on the fluorescent plate as divided in two individually by two sets of images detection means arranged side by side in the direction at right angles to the center axis of the rotation. CONSTITUTION: X rays radiated from an X-ray tube 201 and passing through an object 203 are absorbed by a fluorescent screen 100 as an X-ray transmission image of the object 203 and the energy of the X rays is converted to fluorescence 141 and 142 to be turned to a visible image. The visible image on the fluorescent screen 100 is formed on image detection surfaces of image pickup tubes of video cameras 111 and 112 by mirrors 131 and 132 and optical lenses 121 and 122 to be detected as an X-ray transmission image. The X-ray tube 201, the fluorescent screen 100, the mirrors 131 and 132, the optical lenses 121 and 122 and the video cameras 111 and 112 are fixed on a rotation method 205 and are turned in the direction of the arrow 206 by the rotation mechanism 205 with the object 203 as the center of rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation three-dimensional image capturing apparatus. The image detection unit of the radiation three-dimensional image capturing apparatus according to the present invention is an apparatus that converts a radiation image into a visible light image with a fluorescent plate and performs image detection with a high-sensitivity video camera. Image detection is possible. Therefore, it is possible to reconstruct a three-dimensional radiation image of a large subject, which has not been heretofore, by image processing on the basis of captured images in a large field of view from multiple directions. Therefore,
It is not only suitable for use in medical diagnostic equipment for the purpose of radiographic three-dimensional imaging of a large subject, but also suitable for use in a wide range of general industrial imaging devices.

[0002]

2. Description of the Related Art Conventional radiation three-dimensional image capturing devices include, for example, Medical Imaging Technology
A device using an X-ray image intensifier and an ordinary video camera as a two-dimensional X-ray image detector is known, such as the device described in Vol. 10 (1992), pp. 113-118. . With this device, in X-ray three-dimensional imaging,
By using a video camera, X-ray transmission images of the subject from multiple directions are captured in a short time in which movement of the subject can be ignored, and an X-ray three-dimensional image of the subject is processed by image processing based on these images. Reconstruct. Another conventional radiation three-dimensional image capturing apparatus is a radiology magazine, November 1992, volume 185 (RADIOLOGY, November 199).
2, Volume 185 (P), page 271, Development of 3DCT with large area detection system (Development of 3D CT with)
As a device described in a Large Area Detection System), a fluorescent screen and a CCD are used as an X-ray image detector.
There was a device that used a camera. This device uses a large-area fluorescent screen for the X-ray image detector, and it captures an X-ray transmission image of a large subject by detecting an X-ray image in a large field of view, and then X-rays the image of a large subject by image processing. A three-dimensional image can be reconstructed.

[0003]

The former of the above-mentioned prior art,
That is, in an apparatus using an X-ray image intensifier as a two-dimensional X-ray image detector and an ordinary video camera, an X-ray image intensifier is used to convert an X-ray image into a visible light image. Therefore, the size of the visual field for detecting the X-ray image is limited by the aperture of the X-ray image intensifier. Therefore, there is a problem that an X-ray three-dimensional image cannot be captured for a large subject. Further, in the latter of the above-mentioned conventional techniques, that is, in an apparatus using a fluorescent screen and a CCD camera as an X-ray image detector, the X-ray image detecting unit is provided with an X-ray image intensifier that constitutes the apparatus of the above-mentioned conventional example. Since there is no such amplified portion of the image signal, the luminance level of visible light, which is the input signal of the image detected by the CCD camera, is low, and the output signal level of the CCD camera itself is low. For this reason, the influence of the camera circuit noise of the CCD camera becomes large, so that the image quality of the X-ray transmission image of the detected object deteriorates, and the image quality of the X-ray three-dimensional image reconstructed by image processing is low. . Further, in the above-mentioned two conventional devices, there is only one video camera constituting the X-ray image detector, and the visual field and spatial resolution for X-rays as the X-ray image detector are the number of scanning lines of the video camera or the CCD. There was a problem that the number of pixels of the camera was limited. Further, in the above conventional device, X
The field of view and the spatial resolution of the line image detector are fixed, and there is a problem that an X-ray transmission image can be captured only with a constant field of view and spatial resolution regardless of the size of the subject. The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problems in the related art and to capture a radiation transmission image of a subject from multiple directions in a large visual field for radiation. However, it is another object of the present invention to provide a radiation three-dimensional image capturing apparatus capable of obtaining a radiation three-dimensional image of a large subject by image processing based on these images. Another object of the present invention is that the field of view size and spatial resolution as a radiation image detector are variable, and the optimum field of view size and spatial resolution can be set according to the size of the subject, and high quality radiation can be obtained. An object of the present invention is to provide a radiation three-dimensional image capturing apparatus capable of obtaining a three-dimensional image.

[0004]

The above object of the present invention is to provide a radiation generating means, a fluorescent plate for converting a radiation transmission image of the subject after the radiation generated by the means has passed through the subject into a visible light image, An image detecting means including a mirror for detecting a visible light image on the fluorescent plate, an optical lens and a video camera, a rotating means for rotating the radiation generating means, the fluorescent plate and the image detecting means around an object, and the video. An image collecting unit for converting the output image of the camera into a digital signal image and collecting it, an image processing unit for image-processing the digital signal image collected by the unit, and a display unit for displaying the image processed by the unit are provided. Then, a plurality of radiation transmission images of the subject from a plurality of directions are collected, the three-dimensional image of radiation is reconstructed by the image processing means, and the three-dimensional image is displayed on the image. A radiation three-dimensional image capturing apparatus for displaying by a step, wherein a size of the fluorescent plate is longer in a direction perpendicular to a rotation center axis of the rotating means with respect to a length in a rotation center axis direction of the rotating means. , The visible light image on the fluorescent plate is divided into two in the direction perpendicular to the rotation center axis of the rotating means, by two sets of image detection means arranged side by side in the direction perpendicular to the rotation center axis of the rotating means, A radiation three-dimensional image capturing device characterized by individually detecting visible light images on the fluorescent plate divided into two, or two sets of image detecting means for detecting a visible light image on the fluorescent plate, the fluorescent plate The position control means for controlling the position with respect to, the means for controlling the distance between the fluorescent plate and the image detecting means, the center position on the fluorescent plate as the center of the image detected by the image detecting means, any on the fluorescent plate Size The visible light image,
This is achieved by a radiation three-dimensional image capturing device characterized by detecting by the image detecting means.

[0005]

In the radiation three-dimensional image photographing apparatus according to the present invention, as a radiation image detector constituting the radiation three-dimensional image photographing apparatus, a video camera using a fluorescent screen and an avalanche multiplication type image pickup tube which is a high-sensitivity video camera. With a combination of
Furthermore, by dividing the visible radiation image on the fluorescent plate into a single fluorescent plate by two video cameras and detecting the divided image, a larger field of view is achieved. A radiation image detector having a large field of view can be used to capture radiation transmission images of a large subject from multiple directions, and a three-dimensional radiation image can be obtained by image processing based on these radiation transmission images. In a normal image pickup tube camera, the light incident on the image pickup tube is converted into a number of charges proportional to the amount of light in a photoconductive film for detecting the light, and these charges reach the electrodes and become a signal current. Further, since the CCD camera operates with low noise, it has higher sensitivity than a normal camera tube camera, but the basic principle of detecting light is the same as that of a normal camera tube camera.
On the other hand, in an avalanche multiplication tube camera, after the light incident on the tube is converted into a number of charges in the photoconductive film that is proportional to the amount of light, photoconductivity is reached while these charges reach the electrodes. Collisions with atoms in the film are repeated, and new charges are generated one after another to multiply the amount of charges. This is because the electric field applied to the photoconductive film of the avalanche multiplication type image pickup tube is stronger than that in the case of a normal image pickup tube, and the charge is strongly accelerated in the photoconductive film. Due to this avalanche multiplication effect, the maximum number of charges is 1
Since it is multiplied up to about 000 times, it can be used as a highly sensitive image detector. Therefore, by using the avalanche multiplication type imaging tube camera, it is possible to detect with high sensitivity even a visible light image of low brightness such as when a radiation image is made visible with a fluorescent plate. Further, the avalanche multiplication type imaging tube camera has a great feature that an image signal component which is an output signal of the camera is amplified due to an increase in signal charge due to avalanche multiplication, but a noise component hardly increases. When a low-luminance dark image is captured by a normal camera tube camera or CCD camera, the image luminance of the displayed image becomes dark. For this reason, it is necessary to increase the amplification factor in the amplification circuit of the camera for photographing. In this case, the circuit noise of the amplifier circuit is also amplified, the effect of the circuit noise appears strongly in the captured image, the signal-to-noise ratio decreases, and only an image with deteriorated image quality can be obtained. On the other hand, in the avalanche multiplication type camera, the increase in the noise component due to the avalanche multiplication is negligibly small, so that it is not only highly sensitive as an image pickup tube, but also has a very good signal-to-noise ratio. It is an image detector. The multiplication of the number of charges due to the avalanche multiplication effect, that is, the increase in sensitivity as a camera can be controlled by the image pickup tube target voltage applied to the photoconductive film of the image pickup tube. By controlling the target voltage of the image pickup tube, it is possible to obtain the optimum output signal current amount according to the amount of light incident on the image pickup tube. As a result, the optimum sensitivity can be set according to the amount of incident light. In order to capture a radiation three-dimensional image, it is necessary to capture a radiation transmission image of the entire subject from multiple directions and reconstruct a three-dimensional image by image processing. As shown in FIG. 1, in order to obtain a three-dimensional radiation image of a vertically long subject 203 such as a human body, it is necessary to capture a radiation transmission image of the entire target region including the side profile of the subject. Therefore, as the fluorescent plate, the dimension parallel to the rotation surface of the rotating mechanism 205, that is, the length in the direction perpendicular to the rotation center axis of the rotating mechanism is longer than the length of the fluorescent plate in the direction parallel to the rotation axis of the rotating mechanism. The rectangular fluorescent plate of is required. In order to detect a visible light image that is a radiation image visualized by such a rectangular fluorescent plate,
Two video cameras, which are image detectors, are arranged parallel to the rotating surface of the rotating mechanism, and the visible light image on the fluorescent screen is divided into two and detected by the two video cameras. Two divided images are obtained by two video cameras for one radiation transmission image. By performing a combining process of two images on the divided images by image processing, one captured image is generated for one radiation transmission image. This process
Apply to each two-divided image of the radiation transmission image from multiple directions of the subject obtained by shooting while rotating the rotating mechanism, and generate one radiation transmission image of each of the subjects from multiple directions To do. Then, image reconstruction processing is executed based on these images to generate a radiation three-dimensional image of the subject. Further, in the present invention, it is possible to adjust the distance between the fluorescent plate and the optical lens / video camera system that constitutes the image detection unit of the radiation image detector that constitutes the apparatus. This makes it possible to set the optimum field size and spatial resolution of the radiation image detector according to the size of the subject, and obtain a high-quality three-dimensional radiation image according to the size of the subject. When a visible radiation image on a fluorescent screen is formed on a video camera by an optical lens, the visible light on the fluorescent screen is fixed when the focal length of the optical lens is constant and the distance between the fluorescent screen and the video camera is constant. A video camera detects visible light image components of a certain area in the image. If the focal length of the optical lens is fixed and the distance between the fluorescent plate and the optical lens / video camera system is changed, the size of the area detected by the video camera in the visible light image on the fluorescent plate changes. As a result, it is possible to change the field size for radiation as the radiation image detector.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a perspective view showing the outline of a radiation image capturing apparatus according to an embodiment of the present invention. The apparatus according to this embodiment uses X-rays as radiation. In the figure,
X-rays emitted from the X-ray tube 201 pass through the subject 203. The X-ray transmitted through the subject 203 is
The X-ray transmission image is absorbed by the fluorescent plate 100, and the X-ray energy is converted into fluorescence 141 and 142, whereby the X-ray transmission image is converted into a visible light image. Fluorescent plate 10
The visible light image on 0 is formed on the image detection surfaces of the image pickup tubes of the video cameras 111 and 112 by the mirrors 131 and 132 and the optical lenses 121 and 122, respectively, and the X-ray transmission images of the subject are formed by the video cameras 111 and 112. Detected as. The X-ray tube 201, the fluorescent plate 100, and the mirror 131 described above.
And 132, the optical lenses 121 and 122, and the video cameras 111 and 112 are fixed to the rotating mechanism 205, and they rotate with the subject 203 as the center of rotation with the fluorescent screen 100 facing the X-ray tube 201. The mechanism 205 rotates in the direction of arrow 206. By the rotation of the rotating mechanism 205, X from the multiple directions of the subject 203 can be obtained.
A line-transmission image can be taken. An X-ray three-dimensional image of the subject 203 is reconstructed by image processing based on the captured X-ray transmission images of the subject 203 from multiple directions, and the target subject 203
X-ray three-dimensional image is obtained.

FIG. 3 is a view of the X-ray generator, the image detector, and the rotating mechanism shown in FIG. 1, as viewed from above. Hereinafter, the present embodiment will be described in detail with reference to FIG. In FIG. 3, the X-ray tube 201 radiates and the X-ray collimator 202
The X-rays 213 and 214, which are set so that the irradiation range includes the subject 203 and the entire fluorescent screen, are irradiated to the subject 203, partially absorbed in the subject 203, and partially transmitted through the subject 203 and transmitted. The X-ray component is incident on the fluorescent plate 100. Further, some X-rays pass through the side of the subject 203 and do not pass through the subject 203, but directly on the fluorescent screen 100.
Incident on. The X-rays incident on the fluorescent screen 100 are subject 2
The X-ray transmission image component 03 and the X-ray component directly incident from the side of the subject 203 are absorbed by the fluorescent screen 100. The energy of the X-ray is the fluorescence 141 and 14 here.
By being converted into 2, the X-ray image is converted into a visible light image. The fluorescent plate 100 is in the horizontal direction with respect to the subject 203.
It is a long rectangle in the left-right direction on the paper surface of FIG.
The visible light image on the screen 00 is divided into two in the horizontal direction of the fluorescent screen 100, and the divided image components are divided by the video camera 1.
11 and 112 detect individually. The two divided image components on the fluorescent screen 100 are reflected by the mirrors 131 and 132 and the optical lenses 121 and 122, respectively.
The images are formed on the image detection surfaces of the image pickup tubes 1 and 112, and are detected by the video cameras 111 and 112 as an X-ray transmission image of the subject 203.

FIG. 4 shows the division state when the visible light image on the fluorescent plate 100 is divided and detected by the two video cameras 111 and 112. FIG. 4 shows the fluorescent plate 10 in FIG.
0 corresponds to the view seen from the lower side on the paper surface. An X-ray image converted into visible light appears on the fluorescent plate 100, and it is separated into an image area 101 of a visible light image shown by a shaded square and an image area 102 of a visible light image shown by a white square. To detect. Areas 101 and 102 have a common image area 103 in which the respective image areas overlap. The image component shown in the image area 101 includes the mirror 131 and the optical lens 1.
21 and are detected by the video camera 111.
The image component shown in the image area 102 is detected by the video camera 112 via the mirror 132 and the optical lens 122. Here, in the case of a device in which an X-ray image is converted into a visible light image by a fluorescent plate and the visible light image is detected by a video camera by an optical lens, an optical system for forming the visible light image on the fluorescent plate on the video camera is used. High light collection efficiency is required. This is because, as described above, the fluorescent plate does not have a fluorescent brightness amplifying action unlike the X-ray image intensifier, and the energy of the X-ray is simply converted into fluorescent light, and the visible light image output is This is because the brightness is very low. In an X-ray image capturing apparatus in which a fluorescent screen and a video camera are combined, it is necessary to efficiently form the fluorescent light output from the fluorescent screen on the video camera.

Therefore, in the present embodiment, the fluorescent plate 100 has a dimension in the range of 50 to 100 cm in the direction parallel to the plane of rotation of the rotating mechanism 205 shown in FIG. The direction (perpendicular to the paper surface) is a rectangle with a range of 30 to 70 cm. Also, the focal length of the optical lens is 50
An optical lens having an F number of "1" or less is used. Therefore, the size of each of the divided image areas shown in FIG. 4 is in the range of a square or a rectangle with a size of 30 cm square to 70 cm square. In addition, an ordinary tube camera or C
Since a CD camera lacks sensitivity, an avalanche multiplication tube camera using an avalanche multiplication tube is used as a video camera for detecting a visible light image on a fluorescent plate with high sensitivity. As described above, in the avalanche multiplication tube camera, after the light incident on the tube is converted into a number of charges in the photoconductive film that is proportional to the amount of light, these charges are different from the normal tube camera. Has a function of repeatedly colliding with atoms in the photoconductive film while reaching the electrode, generating new charges one after another and multiplying the amount of charges. This is because the electric field applied to the photoconductive film of the avalanche multiplication type image pickup tube is stronger than that in the case of a normal image pickup tube, and the charge is strongly accelerated in the photoconductive film. Due to this avalanche multiplication action, the avalanche multiplication type imaging tube can be used as a highly sensitive image detector because the number of electric charges is multiplied up to about 1000 times.

Therefore, by using the avalanche multiplication type imaging tube camera, it is possible to detect with high sensitivity even a low-luminance visible light image such as when a radiation image is made visible with a fluorescent plate. In the avalanche multiplication type imaging tube camera, the signal charge increases due to the avalanche multiplication, so that the image signal component which is the output signal of the camera is amplified. Moreover, the avalanche multiplication type image pickup tube camera has a great feature that the image signal component is amplified but the noise component is hardly increased. For this reason, the avalanche multiplication type image pickup tube camera is an image detector which has a negligible increase in noise components due to avalanche multiplication, has high sensitivity as an image pickup tube, and has a very good signal-to-noise ratio. Is. The multiplication of the number of charges due to the avalanche multiplication effect, that is, the increase in sensitivity as a camera can be controlled by the image pickup tube target voltage applied to the photoconductive film of the image pickup tube. By controlling the target voltage of the image pickup tube, it is possible to obtain the optimum output signal current amount according to the amount of light incident on the image pickup tube. As a result, the optimum sensitivity can be set for the amount of fluorescent light that enters the video camera from the fluorescent plate.

A means for reconstructing an X-ray three-dimensional image by performing image processing on the image detected by the video camera will be described with reference to FIG. The image signals output from the two video cameras 111 and 112 are analog signals, and are input to the image collecting unit 172 arranged separately from the rotating mechanism 205 via the signal transmitting unit 171.
The signals output from the video cameras 111 and 112 are sent via signal cables 161 and 162. Since the video cameras 111 and 112 rotate about the subject 203 by the rotation mechanism 205, the signal cable is twisted. The signal transmission means 171 has a structure in which the cable is sufficiently long so that such a twist of the signal cable does not occur, and the signal cable is wound around the rotating mechanism in accordance with the rotation of the rotating mechanism 205 and has a function of suppressing the twist of the cable. Further, the signal transmission means 171 is constituted by the rotation mechanism 205.
And the output signals of the video cameras 111 and 112 are transmitted to the image collecting means 172 arranged separately by a sufficiently long signal cable.

The image collecting means 172 is composed of two analog / digital converters and a digital image memory (not shown). The image collecting unit 172 receives individual analog output signals from the two video cameras 111 and 112, and individually converts the analog output signals into digital signals by the two analog / digital converters. The converted individual digital signals are stored in the individual image memories. With respect to the two stored digital signal images, the image correction / combination means 173 performs a correction process for each image and a combination process of the two images. The flow of image processing by the image correction / combination means 173 is shown in FIG.
Is shown in the flowchart. The output signal of the video camera 111 is stored in the image memory of the image collecting unit 172 as the first divided image, and similarly, the output signal of the video camera 112 is stored as the second divided image. First, the uniformity correction processing of the image brightness level is performed on each divided image.

An X-ray image of X-rays emitted from the X-ray tube is absorbed by the fluorescent plate and converted into a visible light image. This visible light image is not uniform even when there is no object, and has a constant brightness. Have a distribution. This is due to the structure of the portion of the X-ray tube that emits X-rays, the non-uniformity of the thickness of the phosphor film of the phosphor plate, and the angle at which the X-rays are incident on the phosphor plate differ depending on the position of the phosphor. It is due to. The image brightness level uniformity correction is a process for correcting the brightness distribution of the visible light image. In this process, apart from the acquisition of X-ray images of the subject,
Collect images when there is no subject. This image is stored in the image memory of the image collecting means 172 as the first and second divided images when there is no subject. Then, the first divided image of the subject, which is the image when the subject is present, is divided by the first divided image when the subject is not present. Further, similar division processing is executed for the second divided image. As a result, the luminance distribution due to the structure of the X-ray tube or the fluorescent plate included in the divided image of the subject is corrected, and the image component included in the divided image is only the luminance distribution component that reflects only the structure of the subject.

Further, geometric distortion occurs in the image detected by the video camera due to the X-ray optical system, the distortion of the mirror, the aberration of the optical lens, the distortion of the electron beam scanning of the image pickup tube of the video camera, and the like. There is. For example, when a grating made of metal or the like that strongly absorbs X-rays is photographed as a subject, a grating having a linear structure is detected as a curvedly distorted grating. Therefore, next, the image correction / combination means performs image distortion correction. In this processing, in addition to the shooting of the target object, an image of a grid made of metal wires that strongly absorb X-rays as a subject is collected, and the first and second grids of the grid are collected. It is stored as a two-divided image. The image of the grid that is collected and stored is an image of a grid that is distorted in a curvilinear manner. A process of converting the collected distorted image into a distortion-corrected image is performed so that the distorted grid becomes a linear grid that is orthogonal to the image. Based on the distortion correction calculation method obtained as a result, distortion processing is performed on the target subject.

The positions of the intersections where the vertical and horizontal lines of the lattice, which is the subject, intersect are two-dimensionally arranged at equal intervals in the entire lattice as an intersection array. However, in the detected and collected image, the distortion causes the intersection arrays to be arranged at unequal intervals. There is a one-to-one correspondence between each intersection of the subject grid and each intersection of the collected images. If the coordinate system is set on the acquired image, the coordinate position of each intersection position of the grid on the acquired image is determined. Then, the position of each intersection of the subject grid can also be specified as the coordinate position in the coordinate system on the collected image,
A position correspondence table can be created between the intersections of the object grid and the collection images. In this process, based on this position correspondence table, the two-dimensional geometric distortion correction process is performed so that the intersection of the collected images returns to the corresponding intersection position of the subject grid in the coordinate system on the collected image.

The image is a digital image, and for example, the image is configured by an array of pixels such as 512 vertical pixels × 512 horizontal pixels. Therefore, in the coordinate system on the collected image, the coordinate position can be represented only by a finite number of discrete pixel center positions. In order to represent each intersection of the subject grid and each intersection of the collected image with a high accuracy in the coordinate system on the collected image, the unit is less than the scale in which only the central position of each pixel forming the image is used as a unit. , It is necessary to represent the coordinate point of the intermediate position. Therefore, the coordinate point at the intermediate position is calculated by interpolation and extrapolation. Specifically, the coordinates of the intersections of the grid are calculated from the coordinate points of the center positions of neighboring pixels,
Calculated by interpolation and extrapolation. For interpolation and extrapolation, nearest neighbor interpolation (zero-order interpolation) method, Lagrange interpolation method,
Any one of various known interpolation methods such as a sampling function interpolation method and a spline interpolation method is selected and used.

As a result, a position correspondence table can be created between the intersections of the object grid and the collection images in units of a scale below the center position of each pixel forming the image as a unit. In the two-dimensional geometric distortion correction process for the target subject, the image brightness level of each pixel of the collected image is based on the above-mentioned position correspondence table, and at the corresponding coordinate position, the center position of the pixel Is replaced with a new image brightness level in a unit equal to or less than the scale.
Next, the replacement position is returned to the discrete coordinate system of the digital image with the center position of each pixel as a unit. By calculating the image brightness level at the pixel center position, a distortion-corrected digital image can be generated. For this purpose, the coordinates of the intersections of the grid are calculated in the same manner as the above-described calculation method in which the coordinates of the center positions of neighboring pixels are obtained in units of a scale equal to or smaller than the center position of the pixels.
By this two-dimensional geometric distortion correction processing, geometric distortion is corrected and removed, and first and second divided images of the object without distortion that directly reflect the shape of the object are obtained.

Next, the respective divided images are combined to combine the X-ray transmission images of one subject. The first and second divided images are image regions 101 and 1 in FIG.
02, and these image areas include a common image area 103. As described above, even when a lattice is photographed as a subject, the first and second divided images of the subject lattice have common intersections among the intersections of the subject lattice. When the first and second divided images are combined, the two images are combined so that the common grid points overlap each other, so that the images can be combined without causing distortion. As a result of this,
An X-ray transmission image of a single subject that directly reflects the shape of the subject is generated. X-ray tube 201, fluorescent plate 100, mirror 1
31 and 132, optical lenses 121 and 122, and video cameras 111 and 112 are fixed to a rotating mechanism 205, and these rotate around a subject 203 in a state where the fluorescent screen 100 faces the X-ray tube 201. By 205, it rotates in the direction of arrow 206. By rotating the rotating mechanism 205, a large number of sets of first and second divided images as X-ray transmission images of the subject 203 from multiple directions can be obtained.

For example, the rotation mechanism makes one rotation (360 degrees rotation).
If images are taken at every 3 degree angle change during the above, 120 sets of first and second divided images as X-ray transmission images can be obtained. Image correction / combination processing is executed for these 120 sets of first and second divided images, and 120 object X-ray transmission images after image combination are obtained. Then, based on these subject X-ray transmission images, the image reconstruction means 1
At 74, an X-ray three-dimensional image is reconstructed by image processing. In the image reconstructing means 174, based on the X-ray transmission images of the subject 203 from multiple directions, the conventional X-ray transmission is performed.
A method in which a two-dimensional image (tomographic image) reproduction method using line CT is approximately applied to three-dimensional image reproduction is used. Alternatively, by collecting X-ray transmission image data in the three-dimensional Radon region or the three-dimensional Fourier region of the target three-dimensional image and applying the three-dimensional inverse Radon transform or the three-dimensional inverse Fourier transform to each. , X-ray three-dimensional image can be obtained. The X-ray three-dimensional image generated by the image processing is finally displayed on the video monitor or the like by the image display means 175.

Image processing methods in these image reconstructing means are known and are described in detail in the following documents (1) to (4). (1) Practical cone-beam algorithm; A. Feldkamp, Elle. C. Davis and Jay. Double. Cress; jay. Optical Society of America, A / Volume 1,
Number 6 / June 1984. (Practical Cone-Beam
Algorithm; LA Feldkamp, LC Davis and JWK
ress; J. Optical Society of America, A / Vol. 1, No.
6 / June 1984.) (2) General cone-beam reconstruction algorithm; Ji Wen, Teen-Sean Lin, Ping-Chin Chan and Douglas M. Shinozaki; I-E-E Transactions
On Medical Imaging, Volume 12, Number 3, September 1993. (A General Cone-Bea
m Reconstruction Algorithm; Ge Wang, Tein-Hsiang L
in, Ping-chin Cheng and Douglas M. Shinozaki; IEEE
Transactions on Medical Imaging, Vol. 12, No. 3, Se
ptember 1993.)

(3) Alconstruction Algorithm For Helical Cone-Beam Spect;
Won, Gee. El. Zen and G. tea. Galberg; IEE Transactions on Nuclear Science, Volume 40,
Number 4, August 1993. (A Reconstruction
Algorithm for Helical Cone-Beam SPECT; Y. Weng,
GLZeng and GT Gullberg; IEEE Transactions on
Nuclear Science, Vol. 40, No. 4, August 1993.) (4) Three-dimensional reconstruction
From Cone-Beam Data In O
Power of NLog N) Time; Caroline Aguselson and Per-Eric Danielson; Physics in Medicine and Biology, 39
(1994). (Three-dimensional reconstruction from
cone-beam data in O (N ・ N ・ N ・ logN) time; Caroline Ax
lsson and Per-Eric Danielsson; Physics in Medicine
andBiology, 39 (1994).)

According to the above-described embodiment, in order to obtain a three-dimensional radiation image of an arbitrary region in a vertically long subject such as a human body, a radiation transmission image of the entire target region including the contour of the side face of the subject is obtained. It is possible to detect and collect. Therefore, for example, even in a large part of the subject such as the chest or abdomen of the human body, a high-quality radiation three-dimensional image can be reconstructed from the collected image and displayed. FIG. 5 is a top view corresponding to FIG. 3, which is a top view of the X-ray generation unit, the image detection unit, and the rotation mechanism shown in FIG. 1. In the embodiment shown in FIG. 3, the X-ray tube 201 emits light, and the X-ray collimator 202 sets the irradiation range to include the subject 203 and the entire fluorescent screen 100. The X-rays are applied to the subject 203, and the fluorescent screen 10
The visible light image over the entire area above 0 was divided and detected by the two video cameras 111 and 112 as shown in FIG. However, in the case where the head of the human body is photographed as the subject 203 and an X-ray three-dimensional image of the head is obtained, a large field of view for X-rays is not required as shown in FIG. Therefore, in the embodiment shown in FIG.
The following is an example of the case of capturing an image and obtaining an X-ray three-dimensional image of this small subject 204.

As shown in FIG. 3, the mirrors 131 and 132, the optical lenses 121 and 122, and the video cameras 111 and 112, which constitute the image detecting section, are fixed on the moving mechanisms 151 and 152 as a set. The moving mechanism moves the guide rails 161 and 162. With such a position control means composed of the moving mechanism and the guide rail and having a function of adjusting the positional relationship between the image detecting section and the fluorescent plate, in the embodiment shown in FIG. 5, the image detecting section is moved by the moving mechanism. It shows a state in which the fluorescent plate 100 is moved close to the fluorescent plate 100. In this case, the field of view of the visible light image on the fluorescent plate detected by the video camera is narrowed. FIG. 6 is a diagram of the fluorescent plate 100 as viewed from below on the paper surface of FIG. Fluorescent plate 10
A visible X-ray image appears on the image 0 and is separated into an image region 105 of a visible light image indicated by a shaded square and an image region 106 of a visible light image indicated by a white square. And detect. Regions 105 and 106 have a common image region 107 overlapping each image region, similar to that shown in FIG.

The image component shown in the image area 105 is the mirror 13
1 via the optical lens 121 and the video camera 111
Detected in. The image component shown in the image area 106 is the mirror 1
Video camera 11 via 32 and optical lens 122
Detected in 2. In FIG. 5, the X-ray emitted from the X-ray tube 201 is set by the X-ray collimator so that the irradiation range is a part of the central portion of the fluorescent screen including the small subject 204. The X-ray collimator is an X-ray tube 20.
1 is composed of a plurality of plates made of a heavy metal or the like that strongly absorbs X-rays emitted from the X-rays. The X-ray collimator adjusts the X-ray irradiation range to the subject 204 by blocking a part of the X-rays emitted from the X-ray tube 201 by each plate. When the subject 204 is small, even if the X-ray irradiation area is narrow, it is possible to capture a radiation transmission image of the entire target region including the side contour of the subject 204. The distance between the image detection unit and the fluorescent plate is set so that the visual field (corresponding to the image regions 105 and 106 in FIG. 6) of the visible light image on the fluorescent plate 100 detected by the image detection unit and the X-ray irradiation region match. Adjust by moving mechanism. As a result, it is possible to collect an X-ray image of a small subject with a narrow X-ray irradiation area.

For the divided images corresponding to the detected and collected image areas, as in the case of the embodiment shown in FIG. 3, the means 171 to 175 shown in FIG. A three-dimensional image is obtained and the image is displayed. In the embodiment shown in FIG. 5, the guide rails 161 and 162 on which the moving mechanism moves move closer to each other as they approach the fluorescent plate 100. Then, the structure is such that the distance between the two image detecting units approaches as the image detecting unit approaches the fluorescent plate 100 by the moving mechanism. In addition, the generation point of the X-ray generated from the X-ray tube 201,
The moving mechanism moves the two sets of image detecting means so that the two sets of image detecting means maintain symmetrical positions with respect to an axis representing the center line connecting the center points of the fluorescent plates 100. Therefore, the entire image area including the image areas 105 and 106 in FIG. 6 is located at the center of the fluorescent screen.

In the present embodiment, even if the image detecting section approaches the fluorescent screen 100 by the moving mechanism and the size of the image area becomes small, the central part of the fluorescent screen 100 can always be the image detecting area. According to this embodiment, the X-ray irradiation area is adjusted by the X-ray collimator according to the size of the subject, and the visible light image on the fluorescent plate corresponding to the X-ray irradiation area can be detected by the video camera. For this reason, it is possible to detect an X-ray image of a subject having an arbitrary size by the optimum field size for X-rays, and to obtain a high-quality X-ray three-dimensional image under optimal conditions for the size of the subject. You can A perspective view of another embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 1, in an optical system for detecting a visible light image on the fluorescent plate 100 with a video camera,
Fluorescence emitted from the fluorescent screen is reflected by the mirrors 131 and 132 in FIG.
As shown in, in the direction parallel to the rotation surface of the rotation mechanism 205,
The optical axis of the optical system is bent at a substantially right angle. At this time, the respective fluorescences 141 and 142 are bent in the opposite directions by the mirrors 131 and 132, and detected by the video cameras 111 and 112 located in the directions facing each other.

On the other hand, in this embodiment, as shown in FIG. 2, the fluorescence emitted from the fluorescent plate 100 is reflected by the mirrors 131 and 13.
By 2 and, in the direction perpendicular to the rotation surface of the rotation mechanism 205,
The optical axis of the optical system is bent at a substantially right angle. At this time, the respective fluorescence is bent in the same direction by the mirrors 131 and 132 and detected by the two video cameras 111 and 112 facing the rotating mechanism 205. According to the present embodiment,
The size of the image detection unit, including the fluorescent screen and the video camera,
The size can be reduced as compared with the case of the first embodiment, and the image detection unit can be downsized.

It is needless to say that the above embodiment shows an example of the present invention, and the present invention should not be limited to this. For example, in each of the above-described embodiments, the present invention has been described by being limited to X-ray three-dimensional image capturing, but in addition to X-rays, various radioactive isotopes, accelerators, and nuclear reactors are used as radiation generating means. If used, α rays, β
It is possible to obtain a three-dimensional image of radiation by rays, γ rays and various particle rays. Moreover, when using an accelerator or a nuclear reactor as a radiation generating means, the generating means is very large,
The rotation mechanism makes it difficult to rotate the radiation generating means around the subject. However, also in this case, the object can be achieved by arranging the radiation generating means and the image detecting section in a fixed arrangement and rotating the subject itself.

[0029]

As described above in detail, according to the present invention, radiographic transmission images of a subject from multiple directions in a large field of view of radiation are photographed, and image processing is performed based on these images. Therefore, a remarkable effect that a radiation three-dimensional image capturing apparatus capable of obtaining a radiation three-dimensional image of a large subject can be realized is achieved. Further, the visual field size and spatial resolution of the radiation image detector are variable, and the optimal visual field size and spatial resolution can be set according to the size of the subject, and a high quality three-dimensional radiation image can be obtained. This is a remarkable effect that a radiation three-dimensional image capturing apparatus capable of achieving the above can be realized. More specifically, since the radiation image detection unit according to the present invention has a rectangular and large field of view for radiation, in order to obtain a radiation three-dimensional image of an arbitrary portion in a vertically long subject such as a human body, It is possible to detect and collect a radiation transmission image of the entire target region including the contour of Therefore, for example, even in a large part of a subject such as a chest or abdomen of a human body, a high-quality three-dimensional radiation image can be reconstructed from the collected image by image processing and displayed. Further, the radiation irradiation area can be adjusted by the radiation collimator according to the size of the subject, and the visible light image on the fluorescent plate corresponding to the radiation irradiation area can be detected by the video camera. For this reason, it is possible to detect a radiation image of a subject of any size by the optimum field size for radiation, from large parts such as the chest and abdomen of the human body to small parts such as the head and limbs. With a radiation image detecting field of view that is optimal for a dimensional region, image detection is performed and a high-quality radiation three-dimensional image is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a radiation image capturing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the configuration of a radiation image capturing apparatus according to another embodiment of the present invention.

FIG. 3 is a top view of the radiation image capturing apparatus according to the embodiment shown in FIG.

FIG. 4 is a diagram showing an image region of a visible light image to be detected on the fluorescent plate according to the example shown in FIG.

5 is a top view of the radiation image capturing apparatus according to the embodiment shown in FIG. 1, showing a case where the image capturing size is different from that in FIG.

FIG. 6 is a diagram showing an image region of a visible light image to be detected on the fluorescent plate according to the example shown in FIG.

FIG. 7 is a diagram showing an image detection unit and means for obtaining a radiation three-dimensional image in the apparatus according to the embodiment.

FIG. 8 is a flowchart showing the flow of image processing in the image correction / combination means in the apparatus according to the embodiment.

[Explanation of symbols]

 100 Fluorescent Plates 101 and 102, 105 and 106 Image Areas 103 and 107 Overlapping Image Areas 111 and 112 Video Cameras 121 and 122 Optical Lenses 131 and 132 Mirrors 141 and 142 Fluorescence 151 and 152 Moving Mechanisms 161 and 162 Guide Rails 171 Signal Transmission Means 172 Image collection means 173 Image correction / combination means 174 Image reconstruction means 175 Image display means 201 X-ray tube 202 X-ray collimators 203 and 204 Subject 205 Rotation mechanism

Front page continuation (72) Inventor Hironori Ueki 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Koichi Koike 1-1-14, Uchikanda, Chiyoda-ku, Tokyo Stock company Inside Hitachi Medical

Claims (20)

[Claims] 1. A radiation generating means, a fluorescent plate for converting a radiation transmission image of the subject after the radiation generated by the means has passed through the subject into a visible light image, and a mirror for detecting the visible light image on the fluorescent plate. And an image detecting means including an optical lens and a video camera, a rotating means for rotating the radiation generating means, the fluorescent plate and the image detecting means around a subject, and an output image of the video camera for converting into a digital signal image. A plurality of the subject from a plurality of directions, and image collection means for collecting the image data, image processing means for image-processing the digital signal images collected by the means, and display means for displaying the image processed by the means. Radiation three-dimensional image capturing for collecting the three-dimensional image of radiation by the image processing means, reconstructing the three-dimensional image of radiation by the image processing means, and displaying the three-dimensional image by the image display means. In the device, the size of the fluorescent plate is such that the length in the direction perpendicular to the rotation center axis of the rotating means is longer than the length in the rotation center axis direction of the rotating means, and the visible light image on the phosphor plate is formed. , The visible light on the fluorescent plate divided into two by two sets of image detecting means which are divided into two in a direction perpendicular to the rotation center axis of the rotating means and are arranged side by side in a direction perpendicular to the rotation center axis of the rotating means. A radiation three-dimensional image capturing apparatus characterized by individually detecting an image. 2. The image processing means comprises image correction / combination means and image reconstruction means, and the visible light image on the fluorescent screen is divided into two by the two sets of image detection means. To generate a radiation transmission image of one subject by combining the two images obtained by individually detecting and collecting the visible light images on the divided fluorescent plate by the image correction / combining means. The radiation three-dimensional image capturing device according to claim 1. 3. A plurality of two images of the subject from a plurality of directions are obtained by the radiation generating means, the fluorescent plate, the two sets of image detecting means, the rotating means and the image collecting means. A set of radiographic images is collected, and in each direction, the image correction / combining means combines the two images to form a set of images, and a radiographic image of one subject is formed in each direction. It is characterized in that a three-dimensional image of radiation is reconstructed by the image reconstructing means on the basis of a radiation transmission image of one subject generated in a plurality of directions in each direction with respect to the subject. The radiation three-dimensional image capturing apparatus according to claim 1. 4. In the image processing in which the two images are combined by the image correction / combination means to generate a radiation transmission image of one subject, the radiation generation means generates the radiation transmission image for each of the two images. Non-uniformity of the intensity distribution of the radiation to be, non-uniformity of the brightness distribution on the fluorescent plate when the fluorescent plate converts the radiation into fluorescence, the visible light image on the fluorescent plate using a mirror and an optical lens 2. The radiographic transmission image of one subject is generated by combining the two images after correcting the non-uniformity of the sensitivity distribution on the detection image detected by the video camera. The radiation three-dimensional image capturing apparatus according to 2. 5. In the image processing in which the two images are combined by the image correction / combining unit to generate a radiation transmission image of one subject, mirror distortion is caused for each of the two images. After correcting the distortion of the detected image, the distortion of the detected image due to the aberration of the optical lens, and the distortion of the detected image due to the non-linearity of the electron beam scanning of the image pickup tube that constitutes the video camera, The radiation three-dimensional image capturing apparatus according to claim 1, wherein the images are combined to generate a radiation transmission image of one subject. 6. The two sets of image detection means divide the visible light image on the fluorescent plate into two, and the visible light images on the fluorescent plate divided into two are individually detected and collected. Each of the two images includes a central image component on the fluorescent plate in common, and when the two images are combined by the image correcting / combining unit to generate a radiation transmission image of one subject, 3. The three-dimensional radiation image capturing apparatus according to claim 1, wherein the two images are combined so that the image parts of the image component regions that the two images include in common coincide with and overlap with each other. 7. The radiation three-dimensional image capturing apparatus according to claim 1, wherein the video camera forming the image detecting means is a video camera using an avalanche multiplication type image pickup tube. . 8. The radiation three-dimensional image capturing apparatus according to claim 1, wherein an F number of the optical lens is 1 or less. 9. The radiation three-dimensional image capturing apparatus according to claim 1, wherein the optical lens has a focal length of 50 mm or less. 10. The length range of the fluorescent plate in the direction of the rotation center axis of the rotating means is 30 cm or more and 70 cm or less,
10. The three-dimensional radiation image capturing apparatus according to claim 1, wherein the range of the length of the rotating means in the direction perpendicular to the central axis of rotation is 50 cm or more and 100 cm or less. 11. The fluorescent plate emits light when a visible light image converted by a fluorescent plate that converts a radiation transmission image of the subject into a visible light image is detected by an image detection unit including the mirror, an optical lens, and a video camera. The fluorescence three-dimensional image capturing apparatus according to any one of claims 1 to 10, wherein an optical axis of an optical path of the fluorescence emitted from the fluorescent plate and reaching the video camera is bent at a substantially right angle by the mirror. 12. The mirror in each of the two sets of image detecting means with respect to a rotation plane perpendicular to the rotation center axis of the rotation means, the optical axis of the optical path where the fluorescence is emitted from the fluorescent plate and reaches the video camera. The three-dimensional radiation image capturing apparatus according to claim 11, wherein the three-dimensional image capturing apparatus is bent in a direction parallel to the rotation surface and in an opposite direction substantially at right angles. 13. A mirror in each of the two sets of image detecting means with respect to a rotation plane perpendicular to an axis of rotation of the rotating means, the optical axis of the optical path where the fluorescent light is emitted from the fluorescent plate and reaches the video camera. 12. The radiation three-dimensional image capturing apparatus according to claim 11, wherein the three-dimensional image capturing apparatus is bent in a direction perpendicular to the rotation surface and in a substantially right angle. 14. Radiation generating means, a fluorescent plate for converting a radiation transmission image of the subject after the radiation generated by the means has passed through the subject into a visible light image, and a mirror for detecting the visible light image on the fluorescent plate. And an image detecting means including an optical lens and a video camera, a rotating means for rotating the radiation generating means, the fluorescent plate and the image detecting means around a subject, and an output image of the video camera for converting into a digital signal image. Image acquisition means for performing image processing on the digital signal images collected by the means, and display means for displaying the image processed by the means, A radiation three-dimensional image for collecting a plurality of radiation transmission images, reconstructing a three-dimensional image of the radiation by the image processing means, and displaying the three-dimensional image by the image display means. A means for controlling the distance between the fluorescent screen and the image detecting means by a position control means for controlling the position of the two sets of image detecting means for detecting a visible light image on the fluorescent screen with respect to the fluorescent screen. A radiation three-dimensional image capturing, characterized in that a visible light image of any size on the fluorescent plate is detected by the image detecting unit, with the center position on the fluorescent plate being the center of the image detected by the image detecting unit. apparatus. 15. The image processing means comprises image correction / combining means and image reconstructing means, and the visible light image on the fluorescent screen is divided into two by the two sets of image detecting means. To generate a radiation transmission image of one subject by combining the two images obtained by individually detecting and collecting the visible light images on the divided fluorescent plate by the image correction / combining means. 15. The radiation three-dimensional image capturing apparatus according to claim 14, wherein 16. One sheet generated by combining the two images by the image correcting / combining means with respect to the two images collected by individually detecting the visible light images on the fluorescent plate divided into two. 16. The radiation three-dimensional image capturing apparatus according to claim 14, wherein the center position of the radiation transmission image of the subject is substantially coincident with the center position of the fluorescent plate. 17. The radiation generating means, the fluorescent screen, the two sets of image detecting means, the rotating means, and the image collecting means form a plurality of two images of the subject from a plurality of directions. Collect a set of radiographic images,
For each direction, the image correction / combining means combines a set of images with the two images to generate a radiation transmission image of one subject in each direction. 17. A radiation three-dimensional image is reconstructed by the image reconstructing means based on a radiation transmission image of one subject in each direction. Radiation 3D imager. 18. The two sets of image detection means divide the visible light image on the fluorescent plate into two, and the visible light images on the fluorescent plate divided into two are individually detected and collected. Each of the two images includes a central image component on the fluorescent plate in common, and when the two images are combined by the image correcting / combining unit to generate a radiation transmission image of one subject, 2. The two images are combined so that the image parts of the image component areas that each of the two images includes in common coincide with and overlap with each other.
6. The radiation three-dimensional image capturing device according to any one of 6. 19. The control of the distance between the two sets of image detection means and the fluorescent plate by the position control means detects the two sets of image detection as the distance between the two sets of image detection means and the fluorescent plate becomes shorter. The radiation three-dimensional image capturing apparatus according to any one of claims 14 to 18, wherein position control is performed to shorten a distance between the means. 20. The control of the distance between the two sets of image detecting means and the fluorescent plate by the position control means is performed with respect to a center line connecting the radiation generating position of the radiation generating means and the center of the fluorescent plate. 2. The position control of the distance between the fluorescent plate and the image detection means is performed such that the two sets of image detection means maintain symmetrical positions, respectively.
The radiation three-dimensional image capturing apparatus according to any one of 4 to 18.