Kilovoltage imaging systems on linear accelerators are used for patient localization in many
clinics. The purpose of this work is to assess on-board imaging (OBI) detection of systematic
setup errors and in particular, the dosimetric consequences of undetected head roll in head-
and-neck intensity modulated radiation therapy (IMRT) plans when using these systems.
The system used in this study was the Trilogy linear accelerator and associated software
(Varian Medical Systems, Palo Alto, CA). Accuracy of OBI localization was evaluated using …