Comparative analysis for dose verification of volumetric modulated arc therapy by Varian EPID and PTW Detector 729

The data of dose verification between Varian EPID and PTW Detector 729 is compared to discuss whether the statistics difference of gamma passing rates between the two methods exists. The RapidArc plans for different body sites of 30 patients undergoing radiation treatment with RapidArc technique were used for the generation of the two verification plans, with one for using the electronic portal imaging device (EPID) of Varian RapidArc systems (Varian medical systems), and the other for using the chamber array detector from PTW(PTW Detector 729). Seven comparative experiments were performed for each pair of the plans, which were measurements inside the target, inside the effective detection area, and the target with expansions of 5 mm,10 mm, 20 mm, 30 mm, and 50 mm, respectively. The gamma passing rate of 3%/3 mm and F-test were used in the quantitative analysis. No statistical difference between the two methods was found for the measurement of the area of target with 30 mm expansion (F = 0.395, p > 0.05), while statistical difference existed (p < 0.05) for all the other measurements. The comparative analysis showed that both verification methods have advantages and disadvantages and the countercheck of each other will provide value for comprehensive verification of intensity modulated radiotherapy(IMRT) plans. (authors)