Dosimetric comparison of flattening filter-free beams with the flattened beam of 6 mv and 10 mv photon for volumetric modulated arc therapy in cervix carcinoma plans

Aim: To dosimetrically compare Volumetric modulated arc therapy (VMAT) plan of attening lter-free beam (FFF) and attened beam (FB) for 6 MV and 10 MV photon beams planned for cervix carcinoma cases. A total number of t Materials and Methods: hirty three cervix carcinoma cases treated in 2021 and 2022 were selected retrospectively. The VMAT plans were prepared using Eclipse™ 13.6v Treatment Planning System. Prescription used for planning was 50 Gy in 25 Fraction. 16 patients planned with 6MV and 6MV-FFF beam. Remaining 17 patients were planned with 10MV and 10MV-FFF beam. Two full arcs with no avoidance sector were used in all plans. For inverse planning optimization Progressive Resolution Optimizer (PRO) with 2.5 mm grid size used and for dose calculation, Analytical Anisotropic Algorithm (AAA) was used. During optimization, dose objectives of PTV and OAR are kept constant between two plans. Priorities and NTO also maintained similar between two set of plans. Optimization and dose calculation steps are repeated sometimes to achieve clinically acceptable plan. The tools used to evaluate the plans are; Target Conformity Index (CI), Homogeneity Index (HI), dose to OARs, mean Normal tissue integral Dose (NTID), total monitor units (MUs) and Beam on Time (BOT) were analyzed. For statistical analysis, student t-test method was used. From the results it is observed that plans Result: created by FB and FFF beams are clinically acceptable. CI, HI in PTV coverage, normal tissue volume receiving low doses, MU and BOT are showing signicant results. Mean NTID is found to be signicant only in 10MV beams. FFF VMAT plans does not shows any signicant dosimetric differences over FB VMAT plans in terms of OAR mean dose in cervix carcinoma cases. However 10 MV-FB shows better rectum sparing than 10 MV-FFF. FB can be used for VMAT plans when conformity and homogeneity Conclusion: Index are concerned. FFF beams VMAT plan can be used for patient those who have chances of secondary malignancies since it reduces volume receiving low doses.