Radiosurgery with Linac Based Photon Knife in Cerebral Arteriovenous Malformation

Kim, Jin Hee; Choi, Tae Jin

Abstract

PURPOSE: The purpose of this study was to analyze the effect of a Linear accelerator based Photon Knife Radiosurgery System developed by the staff of Keimyung University Dongsan Medical Center for the treatment of cerebral arteriovenous malformation. Material and Methods:Between December 1993 and October 2000, 30 patients with cerebral arteriovenous malformation (AVM) were treated with the Linac based Photon Knife Radiosurgery System in the Department of Therapeutic Radiology at Keimyung University Dongsan Medical Center. The median age was 34, ranging from 7 to 63 years, with a 2:1 male to female ratio. The locations of the AVM nidi were the frontal lobe (motor cortex), parietal lobe, and the thalamus, in that order. The diameters of the AVM nidi ranged 1.2 to 5.5 cm with a mean of 2.9 cm, and target volumes of between 0.5 and 20.6 cc, with a mean of 6.8 cc. The majority of patients received radiation doses of between 1,500 and 2,500 cGy, with a mean of 2,000 cGy, at 80% the isodose line. Twenty-five patients were treated with one isocenter, 4 with two, and 1 with four. The follow-up radiological evaluations were performed with cranial computed tomogram (CT) or MRI between 6 month and one year interval, and if the AVM nidus had completely disappeared in the CT or MRI, we confirmed this was a complete obliteration, with a cerebral or magnetic resonance angiogram (MRA). The median follow-up period was 39 months with a range of 10 to 103 months.
RESULTS
Twenty patients were radiologically followed up for over 20 months, with complete obliteration observed in 14 (70%). According to the maximal diameter, all four of the small AVM (<2 cm) completely obliterated, 8 of the 10 patients with a medium AVM (2~3 cm) showed a complete obliteration, and two showed partial obliteration. Among the patients with a large AVM (>3 cm), only one showed complete obliteration, and 5 showed partial obliteration, but 3 of these underwent further radiosurgery 3 years later. One who followed up for 20 months following further radiosurgery eventually showed complete obliteration. Ten patients with seizure symptoms had no recurrent seizure due to radiosurgery and medication. One of the eleven patients who suffered intracranial bleeding developed further bleeding at 9 and 61 months following the radiosurgery although complete obliteration was evevtually observed and the patient was managed in hospital then recovered. No patient suffered severe complications following the radiosurgery.
CONCLUSION
The radiosurgery with Linac-based Photon Knife radiosurgery system, developed by the staff at our hospital, is a safe and effective treatment for AVM patients having diameters or volumes of less than 3 cm or 10 cm3, respectively, located in inoperable areas or who refused neurosurgery. We suggest that staged AVM radiosurgery may initially be considered, if the AVM target volume is above 10 cm3.