Comparison of dose verification systems used for IMRT QA

Purpose: The purpose of this study is to compare various dose verification systems used in Intensity Modulated Radiotherapy (IMRT) in terms of their reliability, applicability, application time and with treatment planning system (TPS) on dosimetric aspects.Material and Methods: The accuracy of the IMRT plans, which were prepared using Eclipse (Varian Medical Systems) TPS, for ten prostate cancer patients was checked before treatment by using different various dose verification systems. The absolute dose verification was achieved using ion chamber (PTW). The IMRT plans were checked with MapCheck, ArcCheck (Sun Nuclear) diode detectors and EPID (Varian Medical Systems) systems using gamma index. Dose difference was 3%, whereas distance to agreement was 3 mm. Total time was defined as sum of time required for the preparation of verification plan, calculation, sending the plan to linear accelarator, setting up of the device, irradiation and dosimetric evaluation.Results: The difference between ion chamber and TPS was observed as 1,81% (0,64-2,52) in measurements and agreement of MapCheck and ArcCheck with TPS was observed as 99,3% (98,4-100), 96,4% (94,7-98,3), respectively. Gamma field value of the agreement between EPID and TPS was determined as 0,175 (0,051-0,286). Average application time for ion chamber, MapCheck, ArcCheck and EPID was 51,2 (±4,73), 41,2 (±3,91), 36,4 (±2,50), 27,4 (±2,54) minutes, respectively.Conclusion: Obtained results for each system used in this study were found within acceptable limits. Different systems for quality assurance in IMRT could substitue each other. According to our experience, the EPID system is seen to be more useful and less time consuming in daily applications.Keywords: IMRT, quality assurance, EPID, diode detectors, ion chamber, gamma index.