Accumulated Dose Deviation of Rotational and Residual Setup Errors on Nasopharyngeal Carcinoma Using MIM Treated by Helical Tomotherapy

Abstract

Background: To analyze the relationship between the rotational and residual setup errors and the dose deviation on nasopharyngeal carcinoma (NPC) treated by helical tomotherapy (HT). Methods: From 25 July 2017 to 20 August 2019, 16 treated NPC patients were enrolled in the study. These patients were scanned with full target range megavoltage computed tomography (MVCT) every other day. Adaptive radiotherapy function application software MIM7.1.3 were used to accumulate the actual dose. The dose deviation with the initial plan dose of the patients’ target and organs at risk (OAR) were compared, and the correlation between the dose change and the setup errors (rotational setup errors and neck residual setup error) was analyzed. Results: Translational setup errors increased farther away from the head. Statistically significant difference among 3 groups was achieved in the directions of left-right (P