Christensen S, Calamante F, Hjort N, Wu O, Blankholm AD, Desmond P, Davis S, Ostergaard L. Inferring origin of vascular supply from tracer arrival timing patterns using bolus tracking MRI. J Magn Reson Imaging 2008;27(6):1371-81.Abstract
    PURPOSE: To investigate the potential of novel postprocessing and visualization techniques to distinguish presence of collateral flow using Bolus Tracking MRI. Collateral blood supply is believed to be of paramount importance in acute stroke, yet clinical evaluation is challenging as the gold standard digital subtraction angiography is often not feasible in the acute scenario. MATERIALS AND METHODS: In principle, bolus arrival delay data contains information about the route of blood supply into tissue and hereby presence of collateral flow patterns. We first examined the potential of current clinical bolus tracking protocols to accurately characterize bolus arrival delay. Using the simulation results, we analyzed bolus tracking data from one normal volunteer and one acute stroke patient. RESULTS: The bolus arrival patterns in the volunteer and in the normal hemisphere of the patient were found to be qualitatively similar and in good agreement with physiology. The bolus was seen to spread from the larger arteries toward the periphery. The stroke hemisphere in the patient indicated a retrograde direction of flow on the cortical mantle consistent with leptomeningeal vessels. CONCLUSION: Bolus tracking MRI can likely be used to distinguish collateral flow patterns from normal flow patterns.