ESTRO 36 Abstract Book

S793 ESTRO 36 2017 _______________________________________________________________________________________________

calculation.

Flattening filter free). Prescription and planning goals were as kept as per TG119. For point dose measurement CC01 (0.01cc) ion chamber was used and measurements were carried out as per TG119 specified points in high and low dose gradient regions. Point dose difference was calculated as ratio of difference between measured and planned dose with prescription dose. Similarly for planar dose measurement I'matriXX (IBA, Scanditronix Wellhofer, Germany) along with multicube-lite phantom was used and measurement plane was kept at 11cm depth. Planned and measured dose planes were compared using gamma index criteria (dose difference/distance to agreement) of 3%/3mm and 2%/2mm. All measurements were performed by keeping phantom on couch at gantry angle zero. Confidence limit calculation was done as specified in All planning goals have been achieved as per TG119 report shown in figure-1. At high dose point measurement mean dose differences averaged over different techniques (IMRT/VMAT) planned with different energies for all test cases was 0.002±0.020, and corresponding confidence limit (mean + 1.96σ i.e. σ stand for standard deviation) was 0.041. At low dose point measurement mean dose averaged over different techniques planned with different energies for all test cases was -0.004±0.021, and corresponding confidence limit was 0.045. For planar dose measurement gamma passing rate averaged over all test cases was 99.40%±0.40 for 3%/3mm criteria and 97.82%±0.13 for 2%/2mm criteria respectively. Present work overall confidence limit (100-mean + 1.96σ i.e. σ stand for standard deviation) for composite planar dose measurement was 1.38(i.e., 98.62% passing) for 3%/3mm and 2.45(i.e., 97.55% passing) for 2%/2mm criteria. Gamma analysis results for a representative measurement are shown in figure-2. TG119. Results

Conclusion It has been shown that the attenuation varies with gantry angle. The inclusion of Fraxion in Monaco improves the calculation from 7% difference to 1% in the worst case (150º, 5x5 open field), furthermore, the skin dose increment and the dose in the build-up region are correctly calculated. EP-1498 IMRT and VMAT commissioning for Versa HD linear accelerator using AAPM TG-119 S. Sharma 1 , V. Subramani 1 , P. Kumar 1 , S. Bhaskar 1 , S. Pathy 1 , S. Thulkar 1 , M. Sairem 1 , A. Binjola 1 , P. Agarwal 1 , N. Dhayanethi 1 , P. Kumar 1 , S. Chander 1 1 All India Institute of Medical Sciences, Radiation Oncology, New Delhi, India Purpose or Objective The purpose of the study is to evaluate the end to end commissioning accuracy of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for Versa HD linear accelerator using AAPM TG-119 protocol. Material and Methods Phantom with contoured structure set was downloaded from AAPM website provided with the TG119 report and above structure sets were used as the patient for all plans created in the study. IMRT [step and shoot (SMLC) and dynamic (DMLC)] and VMAT plans were created for TG119 test cases. All the plans were generated using Monaco 5.1 treatment planning system (TPS) for Elekta Versa HD (Crawley UK) linear accelerator. All plans were created using 7-9 beams for IMRT (as per TG119) and single arc for VMAT for energy 6MV, 6MV-FFF & 10MV-FFF (FFF-