303 Frameless Angiography-Based Gamma Knife Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations

Abstract

INTRODUCTION: Traditional GammaKnife radiosurgery (GKRS) of brain arteriovenous malformations (AVMs) using digital subtraction angiography requires head immobilization using a stereotactic frame. METHODS: This is a retrospective review of unruptured AVM patients who underwent frameless GKRS. Thin-cut magnetic resonance imaging and 3-dimensional DSA were obtained without a stereotactic frame for all patients. The imaging studies were merged for contouring of the AVM nidus. During GKRS treatment, patients were immobilized using an individually molded thermoplastic mask. RESULTS: Thirty-one patients were included in the analysis. The median age is 45.0 years (IQR 28.0-55.0). The median nidus size is 3.0 cm (IQR 2.0-3.4). One patient had a Spetzler-Martin grade I, 11 had a grade II, 11 had a grade III, 6 had a grade IV, and 2 had a grade IV AVM. Eleven patients underwent pre-radiosurgical embolization, two patients had previous microsurgical resection, and one patient had prior radiosurgery. The median administered dose was 20 Gy (IQR 18.0-21.0). Twenty-three patients were treated in a single fraction, 6 in 3 fractions, and two patients received 5 fractions. All patients completed their treatment with the planned radiation dose without complications. CONCLUSIONS: This is the first study that integrates digital subtraction angiography in the treatment planning of brain AVMs using GKRS without utilizing a stereotactic head frame. Frameless GKRS provides numerous advantages over frame-based techniques including improved patient experience, the capability of fractionation, thus, expanding the eligibility of more AVMs for radiosurgery, while maintaining high spatial resolution of the AVM using angiography data.