Quality of Radiosurgical Plans by Leksell Gamma Knife Perfexion in the Treatment of Meningioma: Comparison between two isodose lines (۵۰% and ۷۵%)

Introduction: Radiosurgery is a well-established available technique for treating many diseases and indications. Planning quality assessment is a crucial step in the procedure itself and outcome probabilities; either control or complication probability. Several physical indices and methodology have been developed to describe any plan. Accordingly, plan quality and outcome could be compared with other plans. In current study, the aim was to compare two plans with different isodose line using radiobiological model, tumor control probability (TCP), normal tissue complication probability (NTCP) and plan’s physical indices.   Material and Methods: The cross-sectional study included ۲۰ patients (۵ male and ۱۵ female) with median age of ۴۴ years (۲۱-۶۶) and presented with radiologically diagnosed meningioma. Two radiosurgical forward plans were applied with same marginal dose of ۱۲Gy at two different isodose lines of ۵۰% and ۷۵% isodose alternatively using Leksell Gamma Plan of single session GKS. Dose-Volume Histogram (DVH) was imported to MATLAB to compute TCP, NTCP values at ۵ years for each plan, and physical indices such as coverage, selectivity, conformity, heterogeneity, and gradient indices.Results: Median target irradiated volume was ۷.۵ cm۳ (۰.۵۸۸ -۲۳.۷۲). TCP was significantly higher in the plan using ۵۰% isodose line for the marginal dose than that using ۷۵% isodose line (۹۵.۰۵%, ۴۹.۴۴%, p<۰.۰۵, Independent Samples t-Test). Brainstem and optic apparatus NTCPs were very low ۰.۰۱% (۰-۰.۰۴۵%) in the former plan and zero in the later one (p =۰.۰۰۱, Mann-Whitney test).Conclusion: Radiobiological models and physical indices could be used for the optimum plan selection of GKS

Keywords:

Gamma Knife radiosurgery , Tumor control probability , Normal tissue complication probability , Dose Volume Histogram , Treatment Planning Parameters