T. Gevaert MD, PhD, D. Verellen PhD, B. Engels MD, PhD, J. D’Haens MD, PhD, M. De Ridder MD, PhD
Stereotactic radiosurgery is a treatment technique that uses a single high ablative dose of radiation to benign and malignant laesions while sparing healthy brain tissue. Several systems have been developed to perform this technique, and these differed in the way the irradiation was performed. An accurate positioning, immobilisation of the patient and a precise localisation of the laesion are essential. Traditionally, this was performed with a headring screwed onto the patient’s skull (frame-based technique). The positioning is achieved using a localiserbox, mounted on the invasive headring and stereotactic coordinates, obtained through the planning system. With recent developments in radiotherapy, this high precision positioning can nowadays also be performed without the invasive headring. This non-invasive approach, called frameless, improves patient comfort and uses a mask system to immobilise the patient and image-guidance to accurately position the patient on the basis of anatomy. The Novalis system (Brainlab AG) at the UZ Brussel can use both a frame-based and frameless approach. Frameless radiosurgery is carried out with a mask device and two stereoscopic x-ray images. This innovative frameless positioning technique showed equivalent positioning accuracy and immobilisation characteristics to the invasive frame-based technique.