A room-based diagnostic imaging system for measurement of patient setup

A room-based diagnostic x-ray imaging system for routine measurement of rad iotherapy patient orientation has been developed. The system consists of a pair of room-mounted x-ray tubes and a portable imager consisting of an ort hogonal pair of phosphor screens, a mirror/lens system, a CCD camera, and c omputer software for comparing images of the patient to reference images. O rthogonal pairs of images can be acquired quickly and with relatively littl e exposure, allowing correction of patient setup on a daily basis. This cou ld limit patient setup error to the uncertainty in the measurement and repo sitioning processes, a potentially significant improvement over the present standard. (C) 1998 American Association of Physicists in Medicine. [S0094- 2405(98)00612-9].