As a mechanism of external radiation delivery has been advanced by implementation of sophisticated techniques, such as intensity modulated radiation therapy (IMRT) or volumetric intensity modulated arc therapy (VMAT), verification of delivered dose into a patient has been gaining more importance. As a result, continuous efforts have been made in the developments of dose verification techniques using online measurement devices. In these efforts, the use of an onboard imager, electronic portal imaging device (EPID), has been receiving wide interests as it offers dosimetric measurement with superior spatial resolution as well as portal imaging performance. This study has developed a density-scaled layer model of EPID and applied it to transit dosimetry and dose reconstruction using our previous algorithm of dose reconstruction. The developed model with our algorithm of dose reconstruction may find its use with the ongoing utilization of EPID and Monte Carlo methods for treatment planning.
