Mask-based immobilization in Gamma Knife stereotactic radiosurgery

Aaron Bush, Laura Vallow, Henry Ruiz-Garcia, Steven Herchko, Ronald Reimer, Stephen Ko, Byron May, Daniel M. Trifiletti, Jennifer Peterson

Research output: Contribution to journalArticlepeer-review


The Gamma Knife Icon (Elekta AB, Stockholm) is a cobalt-based stereotactic radiosurgery (SRS) unit to support the use of a thermoplastic mask in lieu of a rigid frame, using an onboard cone-beam CT (CBCT) and an intrafraction motion management system (IFMM). We retrospectively reviewed 124 patients treated with Gamma Knife SRS from January 2018 to December 2019 at our institution using a mask-based immobilization system. Patient and treatment characteristics were collected and summarized as well as interfraction shifts and treatment-related outcomes. This dataset includes 124 patients with an associated 358 intracranial tumors. Twenty-four patients presented with primary brain tumors, which included 14 meningiomas and 10 other histologies, with 100 patients having brain metastases. Sixty tumors were post-operative, while 298 were intact. The median dose for primary tumors was 25 Gy in 5 fractions. Median doses to metastases were 20 Gy in 1 fraction, 27 Gy in 3 fractions, and 25 Gy in 5 fractions. Median interfraction CBCT shifts were submillimeter. Median patient follow-up was 6.28 months. 91% of patients with metastases maintained local control. Our early clinical experience has demonstrated limited toxicity profiles and high patient tolerance, which suggests that mask-based Gamma Knife SRS provides a safe alternative option for frameless SRS. Patients with large target volumes where fractionation is preferred or with small target volumes in non-eloquent areas can be considered for this approach. Response rates are encouraging, and continued follow-up is necessary to investigate long-term control and survival.

Original languageEnglish (US)
Pages (from-to)37-42
Number of pages6
JournalJournal of Clinical Neuroscience
StatePublished - Jan 2021


  • Frameless
  • Gamma Knife
  • Immobilization
  • Stereotactic radiosurgery

ASJC Scopus subject areas

  • Surgery
  • Neurology
  • Clinical Neurology
  • Physiology (medical)


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