Effect of DRR Resolution on Assessment of Patient Position for Head and Neck IMRT

Abstract

Purpose/Objective: To evaluate the effect of CT slice thickness and spacing on the spatial resolution of digitally reconstructed radiographs (DRRs) and on the ability to accurately assess patient positioning errors for IMRT treatment of head and neck cancers. For IMRT head and neck treatments, patient set-up accuracy is typically assessed by comparison of megavoltage treatment portals to DRRs. With the replacement of radiographic portal films by electronic portal imaging devices (EPIDs) and the introduction of multislice CT scanners capable of enhanced resolution images and DRRs for radiotherapy, there is the potential to visualize finer anatomic details, which may lead to more accurate assessment of shifts and rotations in patient position.