Room: ePoster Forums
Purpose: Brainlab Elements is to generate Stereotactic Radiosurgery (SRS) plan to treat Multiple brain Metastases with single isocenter. The goal of this work is to propose the Elements Quality Assurance (QA) method by using Mapcheck2 to verify dose delivery accuracy and assessing dose distribution by the average of conformity Index (CI).
Methods: 32 Elements SRS plans were created with the Elements (Version 1.0). Each plan with 3~15 lesions was mapped to a CT scan of our Mapcheck2 (Sun Nuclear) inside of the MapPhan2 water equivalent phantom as the QA plan. The isocenter of the plan was aligned to the central diode of the Mapcheck2. The 2D dose distribution of coronal plane at the detector depth was exported as calculation QA plan. A Varian linear accelerator True Beam STX system was used for the delivery of Elements QA plan with the Mapcheck2 aligned to isocenter. The measured and planned dose were analyzed with Mapcheck2 commercially available software (SNC Patient Version6.7), comparisons are based on the relative and absolute dose percent difference using the Gamma Index. We selected five different criteria: 1mm/3%, 1mm/5%, 2mm/3%, 2mm/5%, 3mm/3%, compared with different tumor sizes and the average of CI for each plan.
Results: From 9/2018 to 2/2019, there are total 32 Elements cases. The range of the smallest tumors size is 0.05~0.286CC, average is 0.167CC, based on this size, we select 1mm/5% as the criteria to calculate Elements QA pass rate. The range of average CI for 32 cases is 1.11~3.19, total average is 1.45, standard deviation is 0.49.
Conclusion: Mapcheck2 is an effective tool to evaluate the agreement between measured and calculated dose of the Elements plan with 1mm/5% criteria; The average of CI can indicate the planâ€™s dose conformity. These can be used in clinic for Elements QA.