Impact of motion induced artifacts on automatic registration of lung tumors in Tomotherapy

•We aimed to validate a tumor-based registration of lung tumors in Tomotherapy.•We explored the effect of motion-induced MV-CT artifacts on automatic registration.•Registration errors were acceptable (within 1.3 ± 1.2 mm).•Only breathing period of 5 s induced more significant registration errors.•This period should be avoided by applying audio guidance during MV-CT acquisition.