Impact of the Lok-bar for High-precision Radiotherapy with Tomotherapy

Background/Aim: Patient immobilization systems are used to establish a reproducible patient position relative to the couch. In this study, the impact of conventional lokbars for CT-simulation (CIVCO-bar) and treatment (iBEAMbar) were compared with a novel lok-bar (mHM-bar) in tomotherapy. Materials and Methods: Verification was obtained as follows: i. artifacts in CT images; ii. dose attenuation rate of lok-bar, compared to without lok-bar; and iii. dose differences between the calculated and measured absorbed doses. Results: With the CIVCO-bar, there were obvious metal artifacts, while there were nearly no artifacts with the mHM-bar. The mean dose attenuation rates with the mHM-bar and iBEAM-bar were 1.31% and 2.28%, and the mean dose difference was 1.55% and 1.66% for mHM-bar and iBEAM-bar. Conclusion: Using the mHM-bar reduced artifacts on the CT image and improved dose attenuation are obtained. The lok-bar needs to be inserted as a structure set in treatment planning with tomotherapy.