1. Method of detecting the non-uniformity of radiation detectors participating in a detector inventory test comprising the steps of subjecting each of said detectors to a substantially identical flat field exposure to generate a radiation image in each of said detectors, generating for each of said detectors a number of ROI signals representing said radiation image at a predefined number of regions of interest (ROIs), generating ROI signal ratios by expressing the ROI signals relative to a reference ROI signal detected in one of said regions of interest taken as reference region of interest for each of said detectors, averaging the corresponding ROI signal ratios over the detectors participating in said inventory test to extract the non-uniform characteristics of the radiation exposure, calculating the local deviations of the ROI signal ratios expressed relative to said corresponding inventory average ROI signal ratios for the detectors participating in said detector inventory test, calculating the absolute value of the largest of said deviations from said average ROI signal ratios for each detector.