Can magnetic resonance imaging alone accurately define the arteriovenous nidus for gamma knife radiosurgery?

Current radiosurgical treatment of arteriovenous malformations (AVMs) relies on planning protocols that integrate data from both magnetic resonance (MR) imaging and stereotactic angiography studies. Angiography, however, is invasive and associated with a small but well-defined risk of neurological and systemic complications. Magnetic resonance imaging, on the other hand, is noninvasive with multiplanar capability, demonstrates good anatomical detail, and has been shown to be superior to angiography in the delineation of selected AVMs.In this study, MR imaging-related accuracy of defining the AVM nidus in gamma knife radiosurgery is investigated using only T1- and T2-weighted sequences.Little interobserver variability was observed and AVM nidi, as demonstrated on T1- and T2-weighted MR images, were well correlated in terms of size. The displacement of the new target, however, from the original nidus, was not predictable and occasionally was significant, thus precluding safe radiosurgical planning.