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

Dose deviation between the actual accumulated and initial plan is not negligible, but most indicators difference is less than 5%, NPC patients treated by HT with MVCT correction setup errors every other day did not need adaptive radiotherapy model unless got rapid tumor shrinkage or weight loss. Moreover, to minimize the dose deviation, more attention should be paid to the reduction of pitch, roll, and residual error of cervical vertebrae during body positioning.