SU‐E‐T‐336: Transition From Frame Based SRS to Frameless SRS Procedures: A Community Based Hospital Experience

Purpose:The project intent is to transit from frame based SRS to frameless SRS procedure and workflow in a community hospital setting.Methods:The clinic has strong experience in a wide verity of frame based SRS procedures using Novalis 600N linac equipped with BrainLab Micro‐MLC and ExacTrac systems. The addition of new Novalis TX system has opened an opportunity to explore and implement frameless SRS treatment procedure. Phantom End to End studies were performed for this purpose. A calibrated Ionization Chamber was inserted into the phantom and the phantom was positioned on the CT scan couch and SRS immobilization mask was made. A CT scan of the Immobilized phantom was generated with the localization box in place. The CT scan was localized and the ionization Chamber active volume was contoured as a target on the IPlan planning system. A 5 Dynamic Conformal Arcs plan was generated on the Iplan planning system. The Phantom was positioned on the treatment Couch with the SRS Mask and frameless array system in place, and the initial target treatment ISO position was achieved. The chamber was then connected to an electrometer. The two Orthogonal KV images were taken and the final treatment position was achieved within 1mm and 1 degree using ExacTrac. The Five arcs were delivered and the electrometer reading was noted. In addition, RPC SRS head phantom study was performed following RPC procedure.Results:The average absolute dose delivered to the in‐house phantom target was in agreement within 1.5% of the planning dose. The RPC SRS phantom results were within the criteria set by RPC.Conclusion:This work gave the confidence to our clinic to move from invasive frame based to non invasive and efficient frameless SRS and SRT treatments. The clinic has now frameless SRS and SRT treatment procedures and workflow.