X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-12-27
2001-11-20
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S004000
Reexamination Certificate
active
06320930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a method and an apparatus for radiation computed tomography employing a conical radiation beam, and more particularly to improvements in radiation tomography for photographing a moving part of a subject.
2. Description of the Related Art
Radiation tomography for a living organism such as a human body is known and uses a conical radiation (X-ray) beam emitted from a source of radiation. As an example, an X-ray tomograph that collects projection data over the entire circumference of the heart is disclosed in Japanese Unexamined Patent Publication No. 9(1997)-253079. In the X-ray tomograph, the projection data are recorded in synchronization with heartbeats by an electrocardiograph. Because the obtained projection data are not photographed when the states of the heart are all the same, only data for cases where position of the cardiac vein is considered to be the same are sampled and reconstituted.
In the aforementioned conventional example, all projection data are sampled and then only projection data for cases where the position of the cardiac vein is considered to be the same are sampled, so it will take time to sample data and it will be a waste of time. In addition, the influence of radiation on a living organism becomes greater with the lapse of time.
Furthermore, no problem will occur in photographing a part of a living organism that does not move, but there are cases where in photographing a part (such as a heart) that moves periodically, an object to be photographed moves while being irradiated with radiation. When the motion is small, it does not matter. When the motion is large, however, the outline of the image will become obscured, and consequently, there is a problem that a tomogram and a three-dimensional image of high resolution cannot be obtained.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned drawbacks. Accordingly, it is an object of the present invention to provide a method and an apparatus for radiation tomography which are capable of efficiently sampling data, shortening photographing time, and reducing the influence of radiation on a living organism. Another object of the present invention is to provide radiation tomography which is capable of photographing a part of a subject that moves periodically, without obscuring the outline of the tomogram of the moving part.
To achieve the aforementioned objects and in accordance with one aspect of the present invention, there is provided radiation tomography for photographing a radiation projected image of a subject by relatively rotating a radiation source which emits a conical radiation beam and a detector which detects the cone radiation beam transmitted through the subject, with respect to the subject. The radiation tomography comprises the steps of: detecting a periodic motion of a part of the subject to be photographed; and controlling the radiation source so that in synchronism with the detection, a timing of emitting the conical radiation beam is synchronized with constant timing at which the detected part moves.
In this way, the periodic motion of a moving part of the subject that is photographed is detected and the radiation source is controlled so that in synchronism with the detection, a timing of emitting the cone radiation beam is synchronized with constant timing at which the detected part moves. Therefore, only a specific position on a subject, where image data is desired, can be photographed. As a result, data can be sampled efficiently in a short time and the influence of radiation on a living organism can be reduced.
In accordance with another aspect of the present invention, there is provided a radiation tomography apparatus for photographing a radiation projected image of a subject by relatively rotating a radiation source which emits a conical radiation beam and a detector which detects the conical radiation beam transmitted through the subject, with respect to the subject. The radiation tomography apparatus comprises detection means which detects a periodic motion of a part of the subject to be photographed and control means which controls the radiation source so that in synchronism with the detection, a timing of emitting the conical radiation beam is synchronized with constant timing at which the detected part moves.
In this way, the control means can control the radiation source so that in synchronism with the detection, a timing of emitting the cone radiation beam is synchronized with constant timing at which the detected part moves. Therefore, only a specific position on a subject, where image data is desired, can be photographed. As a result, data can be sampled efficiently in a short time and the influence of radiation on a living organism can be reduced.
A part of the subject that is photographed by the radiation tomograph is, for example, the heart of a living organism, and in that case, the constant timing at which the part moves may be the dilation period of the heart. In the case of the dilation period of the heart, the motion of the heart is least over a comparatively longer period and therefore a tomogram and a three-dimensional image of high resolution are obtained without obscuring the outline of the tomogram.
The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which a preferred embodiment incorporating the principle of the present invention is shown by way of illustrative example.
REFERENCES:
patent: 5612985 (1997-03-01), Toki et al.
patent: 5832051 (1998-11-01), Lutz
patent: 5848114 (1998-12-01), Kawai et al.
patent: 5978439 (1999-11-01), Koppe et al.
patent: 5999587 (1999-12-01), Ning et al.
patent: 6243439 (2001-06-01), Arai et al.
patent: 9-253079 (1997-09-01), None
Bruce David V.
Fuji Photo Film Co. , Ltd.
Kiknadze Irakli
Sughrue Mion Zinn Macpeak & Seas, PLLC
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