X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2000-01-19
2003-04-08
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S098800, C378S098120
Reexamination Certificate
active
06546068
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photographed (radiographed) image data acquisition method and a photographed (radiographed) image data acquisition device which are applied to so-called CT (Computerized Tomography), which involves such operations as projecting cone-shaped radiation toward the subject from different directions of projection to acquire projected image data for each of the directions of projection, and on these projected image data, generating volume data for the subject.
2. Description of the Prior Art
Nowadays, in the field of medical video engineering, there is extensive research into technology for detecting three-dimensional radiation image information, and for example, the helical CT and the cone-beam CT have been proposed (“Cone-Beam CT—Present Status and Future Prospects” Image Information (M); January, 1988, p122 to p127. Refer to Japanese Unexamined Patent Publication No. 9 (1997)-253079).
Here, the “cone-beam CT” is the technology with which a radiation source and a two-dimensional radiation detector are disposed so that the subject is interposed between them; the radiation source and the radiation detector are turned around the subject relative to the subject while cone-shaped radiation is projected toward the subject from the radiation source; on the basis of the permeated radiation image data (precisely speaking, the projected image data) for the subject in the different angular positions, i.e., for the directions of projection which is obtained by detecting, with the radiation detector, the radiation which permeates the subject, the volume data for the subject is acquired; on the basis of the volume data, a three-dimensional image or a tomographic image is displayed on an image display device, or a three-dimensional image or the like is once stored in a memory device. Here, “the radiation detector” refers to a detector mainly consisting of a semiconductor which detects the radiation, and converts it into an electric signal.
Incidentally, with the above-stated conventional cone-beam CT, the region where a three-dimensional image or a tomographic image can be displayed is limited to within the inscribed circle for the region provided by the overlapping portion for all the directions of projection, specifically, for the projection region for all the radiant rays which is formed by the cone-shaped radiation in each direction of projection, when the radiation detector has an area large enough to detect all the cone-shaped radiant rays. Therefore, the region where an image can be displayed is determined by the projection angle for the radiation and the detection region for the radiation detector, and if the image region is to be enlarged, it is required to project a wider angle of cone-shaped radiation (hereafter called “wide-angle radiation”) on the subject, and, with the detector, to detect the wide-angle radiation which permeates the subject. In other words, it is required to use a large-area detector, and project radiation having a projecting angle wide enough to cover the entire surface of the detector.
However, it is difficult to manufacture a large-area radiation detector having a large detection region, and if it could be manufactured, the manufacturing cost would be high, resulting in an expensive device. Therefore, with the conventional CT, it has been difficult to display an image of a large region.
The first photographed image data acquisition method according to the present invention is a photographed image data acquisition method with which a radiation source and a radiation detector disposed so that the subject is interposed between them are turned around the subject relative to the subject while cone-shaped radiation is projected toward the subject from the radiation source, and the radiation which permeates the subject is detected with the radiation detector to obtain photographed image data for the subject,
in which the entire detection region for each of the direction of projections is divided into a plurality of partial regions; the partial radiation detector is moved to each of these partial regions formed by the division; and
by synthesizing the photographed image data for the partial regions which is obtained by detecting, with the partial radiation detector, the radiation which permeates the subject for each of the partial regions, the photographed image data for the entire detection region is obtained.
Here, “photographed image data for the subject” means permeated radiation image data and projected image data or volume data, further, image data for output which carries a projected image, a three-dimensional image, or a tomographic image. Here, “output” means outputting of image data to an image display device, a printing device, a memory device, or other device which can input image data. These definitions are also applicable hereinbelow.
“By synthesizing the photographed image data for the partial regions, the photographed image data for the entire detection region is obtained” refers to any processing which synthesizes the permeated radiation image data or the like for the partial regions to obtain the permeated radiation image data or the like for the entire detection region. For example, it refers to obtaining volume data for the entire detection region on the basis of the projected image data for the partial regions, obtaining image data for output carrying a tomographic image for the entire detection region on the basis of the volume data for the partial regions, or the like, as well as synthesizing the permeated radiation image data for the partial regions to obtain the permeated radiation image data for the entire detection region, synthesizing the projected image data for the partial regions to obtain the projected image data for the entire detection region or synthesizing the volume data for the partial regions to obtain the volume data for the entire detection region.
In moving the partial radiation detector to each of the partial regions formed by the division, it is moved so that each of the partial regions formed by the division is completely covered by the detection region, in other words, the detection region covers each of the partial regions. In this way, for each of the directions of projection, the partial radiation detector is moved in increments of the specified distance corresponding to the above-mentioned division, and in each of the changed-over photographing positions, the photographed image data for the partial regions which is obtained by detecting, with the partial radiation detector, the radiation which permeates the subject is synthesized to obtain the photographed image data for the entire detection region. The number of partial radiation detectors may be one or more than one.
With this first photographed image data acquiring method, it is, of course, preferable to make the above-mentioned division so that the plurality of partial regions are consecutive. In other words, it is preferable that the above-mentioned specified distance in increments of which the partial radiation detector is to be moved be such that the adjacent detection regions for the radiation detector in each of the photographing positions overlap each other.
The second photographed image data acquiring method according to the present invention is a photographed image data acquiring method with which a radiation source and a radiation detector disposed so that the subject is interposed between them are turned around the subject relative to the subject while cone-shaped radiation is projected toward the subject from the radiation source, and the radiation which permeates the subject is detected with the radiation detector to obtain photographed image data for the subject,
in which a plurality of partial radiation detectors disposed in such an arrangement that the entire detection region is covered constitute the radiation detector; and
by synthesizing the photographed image data which is obtained by detecting, with the plurality of partial radiation detectors, the radiation w
Dunn Drew A.
Fuji Photo Film Co. , Ltd.
Yun Jurie
LandOfFree
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