Document Type : Original Paper
Gamma knife unit ,Neurosurgery department,faculty of Medicine AL-Azhar university,Damietta,Egypt.
Gamma knife Damietta Center, Department of Neurosurgery, faculty of medicine, Damietta Azhar university Hospital. Cairo, Egypt.
Biophysics Branch, Physics Department, Faculty of Science, Cairo Azhar University. Cairo, Egypt.
M.D of Neurosurgery ,Stereotaxy and Functional Neurosurgery Unit, Neurological Surgery Department, Tanta University, Egypt. Marseille, Aix Marseille, 264 Rue Saint Pierre, Marseille-13006, Marseille-France
Biophysics Branch, Physics Department, Faculty of Science, Cairo Azhar University. Cairo, Egypt
Department of Radiotherapy and Nuclear Medicine, National Cancer Institute, Cairo;University, Cairo, Egypt
Background: 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.
Materials and Methods: The cross-sectional study included 20 patients (5 male and 15 female) with median age of 44 years (21-66) and presented with radiologically diagnosed meningioma. Two radiosurgical forward plans were applied with same marginal dose of 12Gy at two different isodose lines of 50% and 75% isodose alternatively using Leksell Gamma Plan of single session GKS. Dose-Volume Histogram (DVH) was imported to MATLAB to compute TCP, NTCP values at 5 years for each plan, and physical indices such as coverage, selectivity, conformity, heterogeneity, and gradient indices.
Results: Median target irradiated volume was 7.5 cm3 (0.588 -23.72). TCP was significantly higher in the plan using 50% isodose line for the marginal dose than that using 75% isodose line (95.05%, 49.44%, p=<0.05, Independent Samples t-Test). Brainstem and optic apparatus NTCPs were very low 0.01% (0-0.045%) in the former plan and zero in the later one (p =0.001, Mann-Whitney test).
Conclusion: Radiobiological models and physical indices could be used for the optimum plan selection of GKS.