THREE DIMENSIONAL DOSE VERIFICATION FOR IMRT USING AMORPHOUS SILICON EPIDS

摘要

A 3D method for IMRT verification has been recently developed that acquires an EPID image for each field that will represent the mid-plane dose in a cylindrical virtual phantom. The image is convolved with a kernel to convert the EPID image to the dose at the radial depth of the virtual phantom, and contour corrections applied. A 3D dose matrix within the phantom is then reconstructed using attenuation and divergence corrections to compare to the planned dose distribution. This will provide a faster and more accurate method for verification. The aim of this project is to implement and further develop this method by modifying the kernel correction and by also studying the effect of detector sag with gantry angle. Initial measurements were made to benchmark the accuracy of the method against conventional dosimeters.