MONITOR UNIT (MU) VALIDATION USING VARIOUS TYPES OF DOSIMETERS FOR COMMISSIONING SMALL FIELD IN ECLIPSE™ TREATMENT PLANNING SYSTEM

Abstract

The objective of this study was to investigate the differences of calculated MU between commissioning using corrected FOF from single detector and commissioning using average uncorrected FOF from three detectors. Measurements were carried out on 6 MV flattened photon beams from 1x1 cm2 to 10x10 cm2. Four detectors were utilized to measure depth doses and beam profiles: IBA CC01, IBA PFD, IBA EFD and Sun Nuclear EDGE. For FOF determination, Sun Nuclear EDGE was not used. The determination of FOF was classified into corrected FOF according to IAEA/AAPM TRS 483 and uncorrected FOF from three detectors. Commissioning was undertaken in Eclipse™, and Acuros XB was selected as the dose calculation algorithm. Four beam commissioning datasets were generated. The validation of calculated MU was made in 6 symmetric field sizes, 10 IMRT-SRS plans and 10 VMAT-SRS plans. It was observed that in depth dose curves and beam profiles, the outcomes among all detectors were relatively similar although broader penumbra from CC01 was noted. For FOF, corrected PFD showed higher outcome than the average uncorrected FOF in all field sizes while the corrected EFD and corrected CC01 were agreeable to 1.5x1.5 cm2 and 1x1 cm2, respectively. In symmetric fields, validation of MU yielded mean differences of 0.2%, -1.6% and 1.2% for commissioning using corrected CC01, corrected PFD and corrected EFD, respectively. For validation in IMRT-SRS plans, the mean differences were -1.3%, -3.4% and -1.5%, respectively. For validation in VMAT-SRS plans, the mean differences were 0.2%, 2.0% and -0.2%, respectively.