Depth-of-interaction effects in columnar phosphors for exponential X-ray absorption

The depth-dependent blur of phosphor screens have been studied using analytical and numerical methods by a number of investigators. We present an analysis of the effect of depth-of-interaction on the modulation transfer function of columnar phosphor screens. We extend our previously reported results of single X-ray interactions to the study of X-ray beams that exponentially deposit energy in the phosphor. We show that depth, dependence of the signal is significant also in columnar phosphors. However, the modulation of high frequencies remains high due to the sharpness of the line-spread function caused by waveguiding of light within the columns.