An evaluation of the ICON® mask fixation: Curing characteristics of the thermoplastic fixation and implications for patient workflow.

Thermoplastic mask immobilization is used to perform hypo-fractionated treatments with the Gamma Knife ICON®. We evaluated the curing characteristics of the ICON® Nanor mask using force sensing resistors coupled with a data logging tool designed by us. For patients being treated with masks made the same day as the treatment, often in the same sitting with no removal and replacement of the patient from the treatment cradle, based on the curves 80% of the force of fixation is reached at 30 minutes. Allowing for curing over 10-15 minutes and the subsequent localizing and delivery CBCTs as well as the plan evaluation this is a reasonable time to start of therapy. For more exacting targets that are still requiring hypo-fractionation a cure period of 15 hours or greater will ensure that maximum rigidity of fixation is achieved.