X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-03-01
2001-02-20
Church, Craig E. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Absorption
Reexamination Certificate
active
06192102
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and a system for forming a radiographic image such as a mammographic image or radiographic image of bones of the limbs.
BACKGROUND OF THE INVENTION
A system has been ordinary used as a system for forming a radiograph for medical diagnosis, in which a silver halide photographic light-sensitive material is contacted with an intensifying screen, and imagewise exposed to X-ray, and developed, fixed and washed by an automatic processor. It has been known in such the system that a sharpness of image is considerably lowered by diffusion of light at the time of exposing the light-sensitive material to light-image converted from X-ray image by the intensifying screen.
On the other hand, recently a system becomes to be used, in which a stimulus phosphor plate is imagewise exposed to X-ray and the stimulus phosphor plate is scanned by a laser light beam to readout the image information accumulated in the stimulus phosphor, as a light signal, the light signal is converted to an electric signal and reconverted to a light signal, and the light signal is recorded on a silver halide photographic light-sensitive material by scanning, and the light-sensitive material is developed, fixed, washed and dried by an automatic processor.
Such the system has an advantage such as that an image processing such as gradation controlling, edge stressing and masking can be applied since the image signal is once converted to the electric signal capable of being electrically processed, compared to the phosphor intensifying screen/film system. However, the sharpness of the image is insufficient for a mammographic image or radiographic image of bones of limbs.
It is theoretically expected that a high sharpness can be obtained by the method by directly reading out the image signal from the flat panel detector difficultly reproduced by an usual laser recording system. A system using a laser thermal diffusion transfer process has been also known as the laser recording system other than that using a silver halide photographic light-sensitive material. In the thermal transfer method, an image receiving sheet and a thermally fusible colorant sheet are superposed and an image is thermally transferred. Such the method has problems such as that the sharpness is insufficient, the apparatus is expensive and the image formation speed is low.
SUMMARY OF THE INVENTION
This invention is made based on the above-mentioned background, and the object of the invention is to provide a method by which a radiographic image can be formed rapidly and stably by means of a low cost apparatus.
The object of the invention can be attained by a method for forming radiographic image comprising the steps of capturing a radiographic image by a flat-panel detector, reading out the radiographic image from the flat-panel detector as an image signal, modulating intensity of a laser light beam by the image signal, exposing a silver halide photographic light-sensitive material to the modulated laser light beam by scanning, and processing the silver halide photographic light-sensitive material having a silver halide emulsion layer by a roller transportation automatic processor, in which a photographic characteristic curve of the silver halide photographic light-sensitive material processed by the processor has a gamma value of a straight line connecting a density point of fog+0.5 and a density point of fog+2.5 of from 2.7 to 3.5 and a gamma value of a straight line connecting a density point of fog+0.05 and a density point of fog+0.5 of from 0.8 to 1.3.
REFERENCES:
patent: 5290655 (1994-03-01), Iwasaki
patent: 0 212 968 A2 (1987-03-01), None
patent: 0 933 673 A1 (1999-08-01), None
Amitani Kouji
Ono Koji
Church Craig E.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Konica Corporation
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