Sensitivity of Radiographic Screens to Scattered Radiation and Its Relationship to Image Contrast

For incident X-ray beams of greater than 60 kVp, intensifying screens of rare earth phosphors produced higher radiographic image contrast in the presence of scattered radiation than did screens of calcium tungstate. This was attributed to fundamental energy absorption interaction differences. X-ray absorption is a function of the position of the k-absorption edge of the screen phosphor relative to the X-ray energy spectra of the primary and scattered X-rays. Spectral measurements of X-ray absorption showed that the ratio of primary absorption to scattered absorption is higher for the rare earth screens, causing lower relative sensitivity to the non-information-containing scattered radiation from the radiographic object.