Dynamic stereotactic radiosurgery in arteriovenous malformation. Preliminary treatment results

From December 1986 through August 1988, 25 patients with intracranial arteriovenous malformations underwent radiosurgery with the dynamic stereotactic irradiation technique. The prescribed dose at isocenter ranged from 50 Gy to 55 Gy, given as a single fraction in 92% of the patients. Field sizes, defined at the 90% isodose surface, varied from 5 mm to 25 mm and were chosen in order to deliver 20 to 25 Gy at the periphery of the malformation. To date, 14 angiographic studies were repeated at 1 year posttreatment. In six patients (43%) a complete obliteration of the lesion was achieved. Late side effects were observed in three patients. Our initial analysis, at 1 year posttreatment, suggests that our results are comparable with those previously reported for other radiosurgical techniques. The linac-based dynamic stereotactic technique appears to be a valid alternative to radiosurgery with the Gamma unit or with heavy-charged particle beams.