Intrafraction Motion Management in Cyberknife SRS with 6D-Skull Tracking

Datasets of five patients with intracranial targets treated with CyberKnife VSI using customized, non-invasive frameless thermoplastic cast based immobilization were analyzed. Standard CyberKnife couch for correcting positional offsets and 6D-skull tracking for detecting and correcting intrafraction shifts was used. For each sequential pair of images, the correction to the target position (position “offset”) was determined in six-degrees of motion (3 translations and 3 rotations). In all, 175 intrafraction positional offsets were analyzed to calculate the intrafraction shifts. Mean shifts, standard deviations, and range of shifts were estimated.