Linear Accelerator Configurations for Radiosurgery

The dramatic proliferation of radiosurgery in the 1980s and 1990s has resulted in the development of a plethora of hardware systems and an exponential increase in clinical use. This article summarizes the initial, now mostly historical, developments and emphasizes that most linear accelerator radiosurgery systems are based on three early prototypical systems from Buenos Aires, Heidelberg, and Montréal. These systems have more recently been tailored to permit fractionated radiosurgery, blurring the distinction between radiosurgery and radiotherapy. The commonly used fractionated systems are described. Clinical outcome data for arteriovenous are described. Clinical outcome data for arteriovenous malformations, acoustic neuroma, and meningioma, are mostly preliminary but substantial data are available for the radiosurgical management of metastases. With the recent emphasis on cost containment, cost-effectiveness issues have become significant and at least for metastases some preliminary data suggest a potential "cost benefit" with radiosurgery. The recent publication of data from a prospective randomized trial has established the superiority of boost therapy for malignant glioma and in this article, we present preliminary evidence supporting the use of radiosurgery. Finally, some of the new and exciting developments such as the robot-mounted linear accelerator, the use of shaped fields, and tomotherapy are described.