Validation of Dosimetric Comissioning Accuracy of IMRT for Versa HD Linear Accelerator with AAPM TG-119 protocol

Abstract

Purpose: Verification of the IMRT prior to the introduction the new Versa HD (Elekta) Linac into operation using test examples given in the AAPM TG-119 report. Materials and methods: The verification of plans created both on the basis of the dose prescriptions given in the AAPMTG-119 report and on the basis of the constraints used in the NMRRC was made. The plans were verified using a matrix of ionization chambers (MatriXX Evolution) placed in a mini Phantom (IBA Dosimetry), using gamma criteria of 3 %/3 mm and 3 %/2 mm at a dose threshold of 10 %. In addition to checking the coincidence of the calculated and measured dose distribution in the plane, a comparison of the dose at the point calculated in the Monaco planning system (Elekta) and measured by the CC13 ionization chamber (0.13 cm3 , Iba Dosimetry) inside the PTV and in the organ at risk was carried out. Results: The difference in the dose measured by the ionization chamber and calculated in the planning system was less than 2 %, and correlates well with the results of accredited clinics. The measured dose distribution in the plane well (97-100 % of the points) coincided with the calculated one for all localizations. An exception was the test case with several targets, in which the assessment was carried out according to the 3 %/2 mm gamma criterion. Conclusions: The results obtained when testing IMRT according to the protocol described in the AAPM TG-119 report, can be used to compare their results with the results of other accredited clinics.