Room: AAPM ePoster Library
Purpose: evaluate the end-to-end commissioning accuracy of FF-IMRT and RapidArc for Halcyon linear accelerator based on test cases developed by AAPM Task Group 119 protocol.
Methods: and RapidArc plans were created for TG119 test cases using phantom with contour structure downloaded from AAPM website. All the plans were generated using Eclipse(version 15.5) TPS for halcyon linear accelerator. All plans were designed using 7-9 beams for IMRT and 2-4 arcs for RapidArc with beam energy of 6MV-FFF. The prescription and planning goals were as kept as per TG119. For point-dose measurement CC13(0.13cc) IC and Mobius Verification Phantom were used and were carried out at points in high gradient regions. Similarly for composite planar dose measurement Arccheck was used. The per-field relative gamma was measured using EPID in a way similar to the routine pretreatment patient-specific quality assurance.Planned and measured dose planes were compared compared based on ?-criteria of 3%/3mm-G (global normalization), and a more stringent 2%/2mm-L (local normalization). Confidence limit calculation was done as specified in TG119.
Results: high dose point measurement mean dose differences averaged and corresponding confidence limit were -0.003±0.011 and 0.025 for the IMRT plans, -0.012±0.006 and 0.024 for the RapidArc plans .Planar dose measurement using Arccheck,gamma passing rate averaged was 99.72%±0.24 for 3%/3mm criteria and 96.80%±1.17 for 2%/2mm criteria for IMRT plans, 99.70%±0.45 for 3%/3mm criteria and 95.24%±2.83 for 2%/2mm criteria for RapidArc plans.Confidence limit were 0.75 and 1.19 for 3%/3mm and 5.49 and 10.31 for 2%/2mm criteria for IMRT and RapidArc plans.The Confidence limit using 2%/2 mm gamma criteria using EPID were 98.80%±0.01 and 96.60%±0.02 for IMRT and RapidArc plans.
Conclusion: Confidence limit value of the study could be used as baseline for future patient specific quality assurance.The commissioning of IMRT and VMAT delivery were found within the limits of TG-119.