Epid Dosimetry

Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging

“…Although film dosimetry has conventionally been used for quality assurance of treatment plans, application of electronic portal imaging devices (EPIDs) as an alternative has become an interesting subject due to their ease of setup and ability to provide a large two-dimensional array of real-time data. [2][3][4] During arc delivery the gantry does not follow a perfect trajectory during rotation as a result of the presence of several heavy components in its head, and mechanical imperfections in the bearing system and junctions. [5][6][7] In addition, the EPID which is mounted on the linac by a retractable robotic supporting arm, rotates with the gantry during arc deliveries to acquire dosimetry images.…”

The influence of acquisition mode on the dosimetric performance of an amorphous silicon electronic portal imaging device

“…The a-Si EPID captures a single image consisting of the average number of frames acquired during radiation delivery where a frame is a single scan of all rows. [ 2 ] An alternative acquisition mode is cine mode, which is attractive for the assessment of dynamic procedures. In cine acquisition mode, a sequence of multiple images are captured during radiation delivery instead of a single integrated image.…”

“…In cine acquisition mode, a sequence of multiple images are captured during radiation delivery instead of a single integrated image. [ 2 ] Since cine mode is synchronized to beam pulses, the frame acquisition rate depends on dose rate. [ 3 ]…”

Dose‐to‐water conversion for the backscatter‐shielded EPID: A frame‐based method to correct for EPID energy response to MLC transmitted radiation

“…Electronic Portal Imaging Devices (EPIDs) were initially introduced in radiation therapy to assist in patient alignment and position verification, but have more recently been shown to possess desirable properties for dosimetry. [1][2][3] Despite the benefits of using EPIDs for dosimetry, such as high spatial resolution and real-time capabilities, the clinical implementation of these devices is not as widespread as could be expected. This is mostly due to complications which arise from the EPID's non-water-equivalent dosimetric response caused by the high Z material in the phosphor layer of the detector, which results in a higher sensitivity to lower energy photons.…”