Three- tier rare-earth imaging system.

The increased efficiency of gadolinium oxysulfide intensifying screens as compared to calcium tungstate screens depends primarily on increased absorption of x-ray photons coupled with a twofold increase in light output. Whether this increased efficiency can be effectively used in a routine diagnostic department to significantly decrease radiation dose was the subject of this study. Consecutive radiographic examinations (5,806) were conducted using these "rare earth" screens. Each radiographic room used three individual rare earth screen/orthochromatic film combinations in order to obtain different speeds. These were labeled A, B, and C and ranged from "par" speed high detail to "ultra high" speed with less detail but correspondingly less patient radiation exposure. The system selected for a particular examination was based on the radiologists' requirements for imaging of anatomic detail. Those examinations requiring less detailed resolution (such as bone alignment through a wet plaster cast) were assigned the fastest speed available. The use of a rare earth/3-tier system resulted in an overall reduction in radiation exposure of about 80%.