Effect of secondary radiations on the performance of digital radiographic detectors

摘要

Abstract: Blur and noise in radiographs are caused in part by the transport of fluorescent radiation in imaging detectors. We have studied this effect using a Monte Carlo radiation transport analysis which tracks radiations associated with K, L, and M shell transitions. Energy deposition distributions are accumulated which permit computation of the large area energy absorption and noise characteristics. Additionally, the spatial distribution of deposited energy is evaluated in a manner which permits determination of the line spread function and the auto-correlation function. The frequency dependent detective quantum efficiency, D$-QE$/(E,f), is subsequently determined by Fourier analysis. This novel method is illustrated by considering the response of a selenium direct digital detector to 120 keV x-rays. It is shown that fluorescent radiations associated with the composition of glass substrates cause a frequency dependent drop in D$- QE$/(E,f)/D$-QE$/(E,O) of 10% to 22%. !24