1. Field of the Invention
The present invention relates to an improved cassette for receiving a photoreceptor plate adapted for use in an automated x-ray image processing system.
2. Description of the Prior Art
Automated x-ray image processing systems have been developed and used heretofore. Such systems generally utilize a photoreceptor plate formed of a layer of photoconductive material, e.g., selenium, on a conductive relatively x-ray transparent support member. The photoconductive material has electrical characteristics such that it is capable of holding a uniform electrostatic charge whereby upon being exposed to x-ray irradiation, the x-ray image produced can be transferred to a reproduction suitable for visual examination by an automated processing system.
A cassette for containing the photoreceptor plate in a light-impenetrable environment and adapted for movement through the automated processing system is utilized so that the photoreceptor plate can be manually positioned with respect to those portions of a patient's body being examined and an x-ray source outside the automated processing system by a radiologist. An automated x-ray image processing system of this type is described in U.S. Pat. No. 3,650,620 dated Mar. 21, 1972, and a cassette for use in such a system is described in U.S. Pat. No. 3,827,072 dated July 30, 1974.
In order to minimize image smear caused by ion undercutting, i.e., ionization of air near the surface of the photoreceptor plate, an electrode or capacitor formed of a thin layer of dielectric material sandwiched between x-ray transparent electrically conductive layers has heretofore been included in the cassette. When the charged electrode and photoreceptor plate are exposed to x-rays, image smear due to ion undercutting is minimized. Such an electrode is described in U.S. Pat. No. 3,898,722 dated Aug. 12, 1975.
Heretofore, cassettes of the type described above have been formed of materials which, while being relatively x-ray transparent, still cause x-ray scatter which increases patient x-ray exposure and reduces image quality. In addition, the electric contact means for charging the electrode of heretofore utilized cassettes have been exposed in a manner such that accidental discharge of the electrode and injury to the patient or radiologist is possible.
By the present invention, an improved cassette of the type described above is provided which includes an x-ray window of extremely high x-ray transparency whereby x-ray scatter and patient x-ray exposure are substantially reduced, and which includes electric contact means for charging the electrode which are totally enclosed within the closed cassette.