The evaluation of MR localization for intracranial arteriovenous malformation treated with gamma knife

To evaluate the image quality, treatment effectiveness and complications of intracranial arteriovenous malformation (AVM) treated with gamma knife by MR localization. According to Spetzler-Martin grading system, 73 intracranial AVMs were classified and treated with gamma knife by MR localization. The follow-up period was 6 to 34 months. The quality of MR localization image, the changes of AVM nidi after treatment were analyzed. Using ANOV (analysis of variance) statistic methods, we explored the relationship among the edema surrounding the AVM nidus, the radiation dosage and the AVM volume after treatment. The margin of AVM nidus was clear in all images. In the 73 images, MR signal of the local cranial skin and bone on the fixed points of head frame disappeared in 11 (15%), high or low shallow curve signals in the cerebral border occurred in 5 (7%), the remaining 57 (78%) images had no artifacts. Based on the Spetzler-Martin grading score of AVM, the obliteration rates of AVM nidus were 100% in II, 88% in III, 57% in IV, 75% in V, 60% in VI during the 6-34 months follow-up after treatment. Edema around the AVM nidi occurred in 42 (57.5%) cases; among them, 27 were in slight degree, 10 in medium degree, and 5 in severe degree. Through ANOV statistic methods, we suggested that the degree of edema had no relation with the radiation dosage and AVM volume. Only one case had rebleeding 13 months after radiosurgery. MR localization for AVM treated with gamma knife is reliable and effective.