A system for quality assurance in radiosurgery

A quality assurance system has been developed for stereotactic radiosurgery and radiotherapy, to fulfill three goals: first to evaluate the geometrical error within imaging, second to simulate the complete chain of a treatment beginning with the imaging and ending with the application of dose, and third to verify calculated dose distributions in three dimensions with high spatial resolution and accuracy. A water-filled cylindrical imaging phantom has been manufactured in which equally spaced rods are placed. It can be mounted to a stereotactic frame in different orientations to be imaged using CT and MRI. The distances of the rod positions are analyzed and a reference grid can be positioned to calculate displacement vectors according to which e.g. the head coil can be adjusted. The spectral emission of the light and the filters together with the efficiency of the red CCD channel were matched and balanced with the absorption spectra of the radiochromic film used with the adapted drum scanner. Standardized software has been designed for evaluating the film data, for calibration, for correction of temperature and darkening and for test routines. A spherical phantom with shells and inserts of different tissue equivalent materials has been developed to simulate complex treatment situations within the human skull. Copyright (C) 2004 S. Karger AG, Basel.