Implementation of a stereotactic radiotherapy system

The tests carried out on a recently-installed stereotactic radiotherapy system capable of fully frameless stereotaxy are outlined. The two principle investigations carried out on the planning system were a dosimetry test, and a test to verify the accuracy of localisation from CT examination through to patient treatment. The method employed in frameless relocation for fractionated stereotactic radiotherapy--position detection using stereoscopic infra-red cameras and a set of fiducials attached to a bite-block--was tested for reproducibility. The results of these tests suggest a mean accuracy in treatment localisation of 1.23 mm (maximum 2.72 mm) for single fraction techniques, and 1.77 mm (maximum 4.53 mm) for treatments involving repeated (frameless) localisation. The implications of these accuracies for treatment with single, multiple-fraction and multi-isocentre techniques are discussed.