PURPOSE Portal dose images acquired with an amorphous silicon electronic portal imaging device (EPID) suffer from artifacts related to backscattered radiation. The backscatter signal varies as a function of field size (FS) and location on the EPID. Most current portal dosimetry algorithms fail to account for the FS dependence. The ramifications of this omission are investigated and solutions fo...

By comparing predicted dose images with physically acquired images, radiotherapy fields may be verified. A good portal dose verification chain should be accurate and unrestricted in terms of gantry angle and patient-imager air gap distance. We present latest enhancements and rigorous tests of a portal dose prediction framework based on Monte Carlo (MC) radiation transport. We also present initi...

INTRODUCTION The magnitude of intra- and inter-fractional variation in the set up of breast cancer patients treated with tangential megavoltage photon beams was investigated using an electronic portal imaging device (EPID). METHODS Daily cine-EPID images were captured during delivery of the tangential fields for ten breast cancer patients treated in the supine position. Measurements collected...

The aim of this study was to assess the performance of a gantry-mounted detector system and a couch set detector system using a systematic multileaf collimator positional error manually introduced for volumetric-modulated arc therapy. Four head and neck and esophagus VMAT plans were evaluated by measurement using an electronic portal imaging device and an ion chamber array. Each plan was copied...

Portal dosimetry (PD) was performed for 181 fields from 14 IMRT plans of various clinical sites at gantry zero and source-to-detector distance (SDD) of 100 cm. PD was realized using aSi1000 electronic portal imaging device (EPID) and portal dose prediction (PDP) algorithm implemented in Eclipse treatment planning system (TPS). Agreement of PDP predicted and EPID measured photon fluence/dose dis...

BACKGROUND AND PURPOSE MR imaging of the self-diffusion of water has become increasingly popular for the early detection of cerebral infarction in adults. The purpose of this study was to evaluate MR line scan diffusion imaging (LSDI) of the brain in children. METHODS LSDI was performed in four volunteers and 12 patients by using an effective TR/TE of 2736/89.4 and a maximum b value of 450 to...