Comparison of octavius phantom with EpiQA portal dosimetry software for patient based quality control of vat

Volumetric Arc Therapy ( VAT ) is a treatment technique which rely on modulated photon flux. The aim of the study is comparison patient based quality control results of octavius phantom with EpiQA system. Octavius phantom system includes PTW 729 ion chamber array and verisoft software. EpiQA system, that use electronic portal imaging device ( EPID ) and EpiQA software. Quality assurance plans are generated from 32 patient plans for 62 arcs then irradiated on measurement systems. Measured dose intensity maps are compared with calculated dose intensity maps with gamma analysis method with 3 mm distance to agreement ( DTA ) and %3 dose difference ( %DD ) criteria. Gamma analysis results evaluated and compared with low dose suppress, low dose unsuppress, local and global options and finally two systems results are compared each other. The differences observed between results related on software differences and angular response of Octavius phantom. As a result both measurement systems can be used for patient based verification.