Goodbye face masks! Accurate head and neck radiotherapy using individual dorsal shells and surface guidance.

Abstract

Using surface guided radiotherapy (SGRT), head and neck (H&N) cancer patients may undergo radiotherapy without the discomfort and stress of a restricting face mask. In this study, the patient setup accuracy, number of necessary treatment interrupts, and intrafraction motion for H&N cancer patients positioned using an individual dorsal shell and monitored using SGRT was examined. Twenty-six H&N cancer patients were positioned in a dorsal shell using SGRT. A cone-beam CT (CBCT) was used for online setup correction. SGRT was also used for intrafraction motion monitoring, and repositioning of the patient when an intrafraction motion threshold of 2 mm or 2° (th₂) was exceeded. Based on post-treatment CBCT's, the intrafraction motion and resulting CTV-PTV margin were determined. For 1.1 % of fractions, the patient had to be repositioned because of motion during/after the CBCT, and for 4.4 % of fractions because of inaccurate patient posture. For 3.5 % of fractions, treatment had to be interrupted for repositioning because intrafraction motion exceeded th₂. The CTV-PTV margin for intrafraction motion is 1.1 mm in all directions. A total CTV-PTV margin of 3 mm can be applied. By replacing traditional face masks with SGRT and a dorsal shell, we can offer H&N cancer patients a more comfortable radiotherapy treatment experience without sacrificing the treatment accuracy.