The relationship between the pixel value and exit dose was investigated for a new commercially available amorphous silicon electronic portal imaging device. The pixel to dose mapping function was established to be linear for detector distances between 116.5 cm to 150 cm from the source, radiation field sizes from 5 x 5 cm2 to 20 x 20 cm2 and beam energies of 6 to 18 MV. Coefficients in the mapp...

PURPOSE To quantify the ability of electronic portal imaging device (EPID) dosimetry used during treatment (in vivo) in detecting variations that can occur in the course of patient treatment. METHODS Images of transmitted radiation from in vivo EPID measurements were converted to a 2D planar dose at isocenter and compared to the treatment planning dose using a prototype software system. Using...

Previously we have shown that our routine portal imaging (PI) of the craniofacial region in pediatric brain tumor patients contributed an additional 2%-3% of the prescribed dose and up to 200 cGy to the planning target volume (PTV) and nearby organs at risk (OARs). The purpose of this study is to quantify the reduction in dose to PTV and OARs from portal imaging (PI) of the craniofacial region ...

This article presents an overview of pre-treatment verification of volumetric modulated arc therapy (VMAT) with electronic portal imaging devices (EPIDs). Challenges to VMAT verification with EPIDs are discussed including EPID sag/flex during rotation, acquisition using cine-mode imaging, image artefacts during VMAT and determining the gantry angle for each image. The major methods that have be...

PURPOSE To verify the accuracy of volumetric arc therapy (VMAT) using the RapidArc™ device when switching patients from one single linear accelerator (linac) to a paired energy and mechanics "twin" linac without reoptimization of the original treatment plan. PATIENTS AND METHODS Four centers using 8 linacs were involved in this study. Seventy-four patients previously treated with the 6MV phot...

Amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) are x-ray detectors frequently used in radiotherapy imaging and dosimetry applications. EPIDs employ a copper plate and gadolinium oxysulfide phosphor screen with an array of a-Si photodiodes to indirectly detect incident radiation. In this study, a previously developed Monte Carlo (MC) model of an aSi EPID has been extended for...

Sebastian Reif1*, Philipp Steiner2, and Ellen Hoffmann1 Department of Cardiology, Städtisches Klinikum München-Bogenhausen, Englschalkinger Str. 77, Munich 81925, Germany and Department of General Visceral, Vascular and Thorax Surgery, Städtisches Klinikum München–Bogenhausen, Englschalkinger Str. 77, Munich 81925, Germany * Corresponding author. Tel: +49 172 2497331; fax: +49 89 927

A commercially available amorphous Silicon Electronic Portal imaging device (aSi-EPID) installed onto Siemens Oncor Linear accelerator was evaluated with the objective to be implemented for IMRT quality assurance. EPID properties were investigated; these include reproducibility, dependences between the relative EPID responses and field size, dose rate were studied for both photon beams. To dete...