Reciprocity-Law Failure in Radiographic Image-Forming Systems

概要

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The Reciprocity-law failure characteristics of three brands of medical blue-sensitive X-ray films exposed with intensifying screens are studied. The variation in X-ray intensity for different points on a reciprocity failure curve is obtained by varying the focus-film distance (FFD), since it is confirmed that the X-ray intensity varies approximately as FFD to the minus 2.15th power, for FFDs from 0.40 to 5.68 meters. All of the films investigated show no high-intensity reciprocity failure effects for exposure times of 1/120 to 5 seconds. However, they show remarkably low-intensity reciprocity failure effects for exposure time longer than about 0.3 sec. It is considered that the existence of this low-intensity reciprocity failure must be taken into consideration, since it would affect the patient dose significantly according to the selection of the exposure conditions.
1979-03-05