Mask-based immobilization in Gamma Knife stereotactic radiosurgery.

Area of Science:

• Neurosurgery
• Radiation Oncology
• Medical Physics

Background:

• The Gamma Knife Icon system enables frameless stereotactic radiosurgery (SRS) using a thermoplastic mask, onboard cone-beam CT (CBCT), and intrafraction motion management (IFMM).
• This technology aims to provide a more comfortable immobilization alternative to rigid stereotactic frames.

Purpose of the Study:

• To evaluate the safety, efficacy, and patient tolerance of mask-based Gamma Knife SRS for intracranial tumors.
• To analyze interfraction shifts and treatment outcomes in patients treated with this frameless approach.

Main Methods:

• Retrospective review of 124 patients treated with Gamma Knife SRS using a mask-based system between January 2018 and December 2019.
• Data collected included patient and treatment characteristics, interfraction shifts measured by CBCT, and treatment-related outcomes for 358 intracranial tumors (primary brain tumors and metastases).

Main Results:

• 91% local control rate was observed in patients with brain metastases.
• Median interfraction shifts were submillimeter, indicating high positional accuracy.
• The treatment demonstrated limited toxicity profiles and high patient tolerance.

Conclusions:

• Mask-based Gamma Knife SRS is a safe and well-tolerated alternative for frameless radiosurgery.
• This approach is suitable for patients with large target volumes requiring fractionation or small targets in non-eloquent areas.
• Encouraging response rates warrant further investigation into long-term control and survival.