Performing daily prostate targeting with a standard V-EPID and an automated radio-opaque marker detection algorithm.

Online prostate positioning using gold markers and a standard video-based electronic portal imaging device is reported. The average systematic (random) errors have been reduced from 2.1 mm (2.

Measurements of intrafraction motion and interfraction and intrafraction rotation of prostate by three-dimensional analysis of daily portal imaging with radiopaque markers.

Purpose: To measure the interfraction and intrafraction motion of the prostate during the course of external beam radiotherapy using a video electronic portal imaging device and three-dimensional analysis.

Methods And Materials: Eighteen patients underwent implantation with two or three gold markers in the prostate before five-angle/11-field conformal radiotherapy. Using CT data as the positional reference, multiple daily sets of portal images, and a three-dimensional reconstruction algorithm, intrafraction translations, as well as interfraction and intrafraction rotations, were analyzed along the three principal axes (left-right [LR], superoinferior [SI], and AP).