(Sunday, 7/14/2019)
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% ± 10.9% (mean ± st.dev), 38.9% ± 11.5%, and 35.4% ± 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 GKI’s improved localization and greater dose gradients relative to VMAT.
Keywords
Gamma Knife, Stereotactic Radiosurgery, Treatment Planning
Taxonomy
TH- External beam- photons: gammaknife
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