Abstract
BACKGROUND AND OBJECTIVES: The gold standard for the evaluation of brain arteriovenous malformation (AVM) nidus occlusion after stereotactic radiosurgery is digital subtraction angiography (DSA), which is an invasive technique. We evaluated the role of MRI, especially arterial spin labeling (ASL) in the assessment of nidus occlusion after radiosurgery. DSA was used as the gold standard for comparison. METHODS: Fifty radiosurgically treated brain AVMs were included in this prospective single-center study. All patients underwent a standardized MRI protocol including following sequences: 2-dimensional T2w (TSE) in 3 planes, T1-weighted Magnetization Prepared Rapid Gradient Echo (MPRAGE), axial resolve diffusion-weighted imaging, ASL, time of flight, and time-resolved angiography with interleaved stochastic trajectories. Nidus obliteration according to the standardized MRI protocol was evaluated by an experienced neuroradiologist within 3 days after image acquisition and before DSA was subsequently performed as the reference standard. A second observer retrospectively rated MRI images of all 50 cases blinded to clinical and DSA data after the prospective study was concluded. RESULTS: All cases rated as obliterated by the MRI protocol were confirmed by DSA. However, 26 and 28 AVMs were rated as patent by the observers, which was verified in 22 (85/79%) cases by DSA. ASL had the highest sensitivity among all MRI sequences. In 3 patients, ASL was the only sequence that correctly revealed a residual nidus according to 1 observer. Overall, the sensitivity and specificity of the standardized MRI protocol for detection of a residual nidus were 100/100% and 86/79%, respectively. The interobserver agreement was excellent (κ = 0.92, 0.81-1.00). At last follow-up of this prospective study, 70% of AVMs were completely obliterated. CONCLUSION: MRI evaluation of nidus occlusion including ASL is highly sensitive for residual nidus detection and has a high potential to replace invasive DSA examinations for patients who underwent radiosurgery of brain AVMs.