X-ray or gamma ray systems or devices – Specific application – Tomography
Reexamination Certificate
2002-03-14
2003-04-22
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Tomography
Reexamination Certificate
active
06553093
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The invention relates to a non-CT type radiation tomography device for carrying out a radiation tomography for a subject or object to be examined (hereinafter referred to simply as “subject”).
A system for examining the subject without destruction by using X-rays has a relatively long history, and there are a simple X-ray photographing system wherein X-rays are irradiated to the subject and at the same time a transmitted X-ray image is detected by an X-ray film, imaging plate or image intensifier, i.e. I.I. Tube, to thereby take an image; and an X-ray tomography system wherein an image of a specific section of the subject is taken. In regard to the latter X-ray tomography system, there is a non-CT type tomography system which has been developed from the simple X-ray photographing system prior to an X-ray CT type, not the tomography system of the X-ray CT, i.e. X-ray computerized tomography type which has been developed remarkably.
FIG. 17
is a diagram showing a structure of a photographing system in a conventional non-CT type X-ray tomography (hereinafter, referred to as “X-ray tomography”).
In the conventional non-CT type X-ray tomography system, a subject M is rotated around a rotation axis ra, which has an intersection Ma with an X-ray irradiation axis, i.e. radiation irradiating axis Xa, of an X-ray tube R in the subject M. A detecting surface Da of a sheet-type X-ray detector D for detecting a transmitted or passed X-ray image of the subject M is held perpendicular to the rotation axis ra of the subject. An X-ray fault picture image (hereinafter referred to as “fault picture image”) can be obtained by integration of the transmitted X-ray picture images sequentially obtained based on detected data outputted from the sheet-type X-ray detector D as X-rays are irradiated to the subject M and the subject M is rotated. The reason why the fault picture image can be obtained by integrating the transmitted X-ray picture images is specifically explained hereunder.
As shown in
FIG. 17
, the subject M has a section MA parallel to the detecting surface Da of the sheet-type X-ray detector D including an intersection Ma, and a section MB parallel to the detecting surface Da of the sheet-type X-ray detector D without including the intersection Ma in the subject M. Here, as shown in FIG.
18
(
a
), the section MA has an X-ray shielding area with an A-character shape, and as shown in FIG.
18
(
b
), the section MB has an X-ray shielding area with a B-character shape. Therefore, in the respective transmitted X-ray picture images sequentially obtained based on the detected data outputted from the sheet-type X-ray detector D, for example, as shown in FIG.
18
(
c
), an A-character shape image and a B-character shape image coexist. However, a position of the A-character shape image is always fixed at the center of the picture image, and a position of the B-character shape is moved in a clockwise direction around the A-character shape image as the subject M is rotated. As a result, as shown in FIG.
18
(
d
), in an integrated picture image of all the transmitted X-ray picture images, although the A-character shape image becomes clear due to overlapping of all the images, the B-character shape images become unclear, obscure, by being scattered in all directions. Thus, the picture image of FIG.
18
(
d
) becomes an X-ray fault picture image emphasizing the section MA.
As described above, the non-CT type X-ray tomography system has almost the same structure as that of the simple X-ray photographing system to photograph a specific section in the subject M, so that a fault picture image can be obtained.
However, in the above conventional X-ray tomography system, it has been difficult to set an accurate photographing mode according to a photographing state. According to an object for photographing, a subject or a state of the subject M, even if an emphasizing degree of the section MA is weak, i.e. a resolving power or resolution ability in a depth direction of the fault picture image is low, there may be a case where a photographing mode having a wide photographing area is desired; or even if a photographing area is narrow, there may be a case where a photographing mode having a strong emphasizing degree, i.e. a high resolving power in a depth direction of the fault picture image, of the section MA is desired. However, in the conventional X-ray tomography system, since the range of the photographing mode which can be set is very narrow, it is difficult to set a suitable photographing mode according to a photographing condition.
In view of the above defects, the present invention has been made, and an object of the invention is to provide a radiation tomography device having various photographing modes capable of freely setting a suitable photographing mode according to a photographing situation, and a subject examination apparatus using the same.
Further objects and advantages of the invention will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
In order to attain the above objects, according to a first aspect of the invention, a radiation tomography device comprises an irradiation device for irradiating radiations to a subject; a radiation detector for detecting a transmitted or passed radiation image of the subject; a subject holding and rotating device for rotating the subject around a rotation axis intersecting a radiation irradiating axis in the subject; a Laminographic angle variation device for varying an angle, i.e. Laminographic angle, formed by the radiation irradiating axis and the rotation axis; a picture image processing device for obtaining a radiation fault picture image by storing and calculating the transmitted or passed radiation picture images sequentially obtained based on detected data outputted from the radiation detector as the radiations are irradiated to the subject by the irradiation device and the subject is rotated by the subject holding and rotating device; and a picture image display device for displaying a fault picture image obtained by the picture image processing device.
According to a second aspect of the invention, in the radiation tomography device of the first aspect, the Laminographic angle variation device is structured such that the Laminographic angle is varied by changing an inclination angle of the radiation irradiating axis with respect to the rotation axis of the subject.
According to a third aspect of the invention, in the radiation tomography device of the first aspect, the Laminographic angle variable device is structured such that the Laminographic angle is varied by changing an inclination angle of the rotation axis of the subject with respect to the radiation irradiating axis.
According to a fourth aspect of the invention, the radiation tomography device of the first aspect includes a posture holding device for holding the detecting surface of the radiation detector perpendicular to the rotation axis of the subject.
According to a fifth aspect of the invention, the radiation tomography device of the fourth aspect includes a synchronous rotation device for rotating the detecting surface in synchronism with rotation of the subject around an axis perpendicular to the detecting surface and passing through an intersection of the radiation irradiating axis and the detecting surface, in a state where the detecting surface of the radiation detector is held perpendicular to the rotation axis of the subject.
According to a sixth aspect of the invention, the radiation tomography device of any one of the first to fifth aspects includes a position changing device for changing a position of the subject with respect to the intersection of the radiation irradiating axis and the rotation axis.
According to a seventh aspect of the invention, the radiation tomography device of any one of the first to sixth aspects includes a distance varying device for varying a distance between the subject and the radiation irradiating device in a direction of the radiation irradiating axi
Dunn Drew A.
Kanesaka & Takeuchi
Shimadzu Corporation
Yun Jurie
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