<title>Sensitivity of radiographic screens to scattered radiation</title>

Abstract

This study compares the relative response of various screen-film and computed radiography (CR) systems to diagnostic radiation exposure. An analytic model was developed to calculate the total energy deposition within the depth of screen and the readout signal generated from this energy for the x-ray detection system. The model was used to predict the relative sensitivity of several screen-film and CR systems to scattered radiation as a function of selected parameters, such as x-ray spectra, phantom thickness, phosphor composition, screen thickness, screen configuration (single front screen, single back screen, screen pair), and readout conditions. Measurements of scatter degradation factor (SDF) for different screen systems were made by using the beam stop technique with water phantoms. Calculated results were found to be consistent with experimental observations, namely, both the BaFBr screen used in a CR system and the CaWO<SUB>4</SUB> screen pair have higher scatter sensitivity than the rare earth Gd<SUB>2</SUB>O<SUB>2</SUB>S screen pair; the BaFBr screen in the CR front-screen configuration is less sensitive to scatter radiation than in the normal back-screen configuration; and these screens have higher scatter sensitivity as x-ray tube voltage increases.