A study on the efficacy of digital enhancement of on-line portal images.

A novel method for evaluation of observer performance with portal images has been developed, in which the observer is required to identify and localize predefined anatomical landmarks in digital portal images. The method was employed to compare the spatial accuracy and decision time for landmark localization in unenhanced on-line portal images and images enhanced digitally by selective adaptive histogram modification. The results indicate that anatomical landmarks were more readily identified in the enhanced images, leading to significantly higher accuracy in landmark localization.