Room: ePoster Forums
Purpose: To determine if the Gamma Knife Icon (GKI) can provide superior fractionated stereotactic radiotherapy (SRT) dose distributions for meningioma and post-resection tumor bed treatments relative to Volumetric Modulated Arc Therapy (VMAT).
Methods: Four patients with meningiomas that did not contain major blood vessels and six patients with post-operative tumor cavities were selected retrospectively. Planning target volumes (PTVs) were generated for GKI and VMAT by adding 1 mm and 3 mm margins, respectively, to the gross tumor volumes (GTVs). Identical PTV dose-volume coverage was obtained for the GKI and VMAT plans for each patient. Meningioma and tumor bed prescription doses were 52.7 - 54.0 Gy in 1.7 - 1.8 Gy fractions and 25 Gy in 5 Gy fractions, respectively. GKI dose rate was 3.735 Gy/min for 16 mm collimators.
Results: PTV dose homogeneity was 2.62 - 3.46 (mean 3.00) for GKI and 1.06 - 1.79 (mean 1.28) for VMAT. The minimum dose to the hottest 1%, 5% and 10% of normal brain was lower for GKI than VMAT by 45.8% Â± 10.9% (mean Â± st.dev), 38.9% Â± 11.5%, and 35.4% Â± 16.5% respectively. The maximum organs at risk (OAR) doses were below tolerance for all plans. Ten of the 11 OARs considered received lower mean doses for GKI than VMAT.
Conclusion: Patients requiring tumor bed irradiation and appropriately selected meningioma patients may benefit from GKI-based fractionated stereotactic radiotherapy due to the decreased OAR doses afforded by the GKIâ€™s improved localization and greater dose gradients relative to VMAT.