A study on amorphous silicon electronic portal imaging device (a-si epid) response to delivered radiation doses

Abstract

The use of amorphous silicon flat panel-type electronic portal imaging device (a-Si EPID) as dosimeters in radiotherapy has seen gradual increase in recent times. This research study has assessed dosimetric response of a-Si EPID (Elekta iViewGT) with respect to photon beam qualities on Elekta Synergy Platform linac. Images acquired under reference conditions of 10×10 cm² open field with the a-Si EPID at source to EPID distance (SED) of 159 cm and varying dose of 1-3 Gy in polymethyl methacrylate (PMMA) solid water phantom slabs were used. The experiment was repeated with Farmer-type PTW ionization chamber (IBA 30010) in position and measurement taken at 10 cm in the solid water phantom. Set up conditions for EPID and IC remained same throughout the study. The study observed similar and proportional increases in EPID and IC signals with increasing dose. Maximum deviation of 7.2 % was recorded between EPID and IC measurements. Outcome of the study demonstrates that the a-Si EPID is appropriate for dosimetric verification purposes on the Elekta linac. Comprehensive evaluation of dosimetric properties of EPIDs is thus necessary to ensure reliability in dose measurements on different linac systems