Experimental validation of a MCNP-based model to predict portal dose images from MLC beams

Abstract

[EN] This work presents a technique to perform an electronic portal imaging device (EPID) signal planar calibration into dose terms using Monte Carlo simulations. To that, a complete Monte Carlo (MC) simulation of a radiotherapy treatment linear accelerator including a multi-leaf collimator system (MLC) and an EPID has been developed. Several solid water blocks were used to obtain calibration measurements and simulations with a large dose range in order to study the relation between the squared EPID response and the MC calculated dose. The calibrated EPID has also been used as a dosimetric tool to validate the MC MLC Linac model. Simulation and measurement comparisons are below 5% root mean square of percentage dose difference. This technique could potentially provide a more accurate verification of dose delivery to heterogeneous anatomical regions in patients receiving complex multi-field conformal radiation therapy treatments.