Figure 1. The thermoplastic mask system.

(a) A resin-filled cushion and (b) thermoplastic mask was customized for each patient, with the portion of the mask covering the patient’s nose removed. (c) During treatment, an optical marker was placed on the patient’s nose to monitor intra-fraction motion. (d) Representative image of patient setup, immobilized on the thermoplastic mask system. The coordinates of the reflective marker on the patient’s nose were stereoscopically acquired by the camera, and are used by the software to continuously track and calculate the 3D position of the marker. Displacements between the markers on the patient’s nose and the reference tool were used to determine intra-fraction motion. (e) The mask system on the Perfexion Icon™ platform.