SU-E-T-379: Assessment of the Dosimetric Significance of Isocenter Shift by Means of EPIDQA

Purpose : An EPID based tool for IMRT quality assurance was used to investigate the dosimestric significance of an isocenter shift. Methods : The MU‐EPID software was used to calculate the dose of the measured QA and compare this against the TPS dose calculation in the original CT patient anatomy. Once the dose has been calculated, the isocenter is shifted and a new dose calculation was obtained and compared against the original dose calculation...