A new system for patient fixation in radiotherapy.

A new system for patient fixation in radiation treatment is described. The system consists of an airtight plastic bag with a contents of polysterol microspheres. A valve allows evacuation which results in a rigid close fitting cast. The system was compared with conventional foam cast fixation in 29 patients who were treated for carcinoma of the breast. The patients received radiation treatment over 22 fractions, and portal X-ray pictures were obtained at every second treatment. The portal films were compared with the stimulator radiographs and the variation in the position of the centre cross were measured in cranio-caudal and transversal direction as well as the rotation of the centre cross. The results showed that the daily reproducibility of the patient set-up was considerably improved by the new system, the centre cross deviation of the position of the actual radiation field to the centre cross of the intended field being less than 1 mm in 50% of the cases. The system is time-saving and cheap compared to conventional fixation systems.