Comprehensive Evaluation of Cerebral AVMs with 4D Flow and Perfusion MRI

Cerebral arteriovenous malformations (AVMs) are abnormal direct connections between arteries and veins without an intervening capillary bed. Patients with cerebral AVMs have much higher risk for hemorrhagic stroke due to rupture of the weakened blood vessels. AVMs are often treated by more than one treatment modality, typically with staged embolization followed by surgical resection or radiosurgery. However, it is often unclear which feeding artery should be targeted for embolization and how this will affect hemodynamic outcome. There is also no quantitative way to assess aggressive embolization that may cause post-operative bleeding. In addition, cerebral hemodynamic changes due to AVMs seem to play a key role in their pathophysiology. DSA as the standard tool for the evaluation of AVMs is highly invasive and includes substantial exposure to ionizing radiation, particularly during repeated monitoring or embolization. In addition, despite excellent AVM vascular imaging by DSA, quantitative information on the individual AVM hemodynamics and its impact on the microperfusion in the surrounding brain tissue is lacking. To address these limitations this proposal will develop a comprehensive MRI and analysis protocol for the improved characterization of 3D AVM hemodynamics and quantitative brain tissue perfusion. Our groups has shown that 4D flow MRI based on time-resolved 3D phase-contrast MRI can measure the three-directional velocity field with full volumetric coverage mapping of large cerebral arteries and veins. Quantitative hemodynamic information, such as blood flow, peak velocity, or 3D visualization of intracranial flow patterns, can be obtained from the 4D flow data. To gain additional information on the impact of AVMs on cerebral tissue perfusion, spin echo DSC perfusion has been developed to quantify biomarkers of absolute microvascular perfusion. The ultimate goal of this proposal is to better understand the impact of AVM treatment on both changes of large vessel hemodynamics and regional alternations in markers of tissue perfusion to guide treatment planning. The preliminary results have demonstrated the potential of the combined 4D flow-perfusion MRI method for evaluating the effects of staged embolization on hemodynamic changes of AVMs. Changes in arterial feeding and venous draining patterns as well as perinidal tissue perfusion demonstrated the ability of our method to assess complex hemodynamic changes for the individual AVM.