Gamma Knife Immobilization: Development of an Add-on Brace to Improve Head Stability during Radiosurgery
Abstract
Purpose
To improve immobilization of Gamma Knife patients' heads by limiting pronation motion through dental fixation, thereby enabling shorter treatment times, more accurate dose delivery, and enhanced patient comfort.
Methods
A 3D-printed resin add-on brace was developed to augment the existing thermoplastic mask and optical monitoring system used during Gamma Knife treatments. It provides gentle, tolerable pressure against the upper lip and teeth to restrict pronation. The assembly includes three components: a base, joint, and mouthpiece (together with a metal insert). The current design improves upon an earlier version by adapting it into a practical device that accounts for space constraints within the Gamma Knife hemispherical treatment volume. Continuous contact with the Elekta's existing rigid frame further enhances stability. A modular mouthpiece library provides more flexibility to adapt to variations in the geometry of patients' heads, optimizing dental fixation, with central mouthpiece section rotates to adjust the fixation angle.
Results
Preliminary evaluations indicate improved rotational stability. After intentional head movements, the head equipped with the brace returned to the reference position more consistently and with smaller residual offsets compared with tests performed without the brace. Exceeding the 1.5 mm threshold was also more difficult and required deliberately large movements.
Conclusion
This add-on brace shows promise as a simple, effective enhancement to current mask-based immobilization for the Gamma Knife Icon, with potential to reduce treatment interruptions and improve comfort. Future work includes metal fabrication for greater stability, quantitative evaluation across additional simulated sessions, and development of a workflow for clinical implementation.