Measurements of the signal-to-noise ratio with "ePID QC phantom®" and "epidSoft 2.0" from PTW

Abstract

Electronic portal imaging device (EPID) are used for patient setup during radiotherapy sessions. The purpose of this study was to evaluate the EPID QC Phantom® developed by PTW for quality assurance (QA) and quality control (QC). We used the Software epidSoft 2.0 provided with the phantom for analyzing the images from the EPID. Measurements were performed using the Elekta iViewGT™ on a linear accelerator with 6 MV x-ray beam. The parameters linearity, signal-to-noise ratio (SNR), modulation-transfer-function (MTF) and the low contrast resolution are detected by different areas in the phantom. Analyzing images exported from the EPID Software and imported to epidSoft as various image formats we found inconsistencies. For examining the cause, calculations with Matlab® were performed. © 2009 Springer-Verlag.