Measuring the Integrity of the Human BloodBrain Barrier Using Magnetic Resonance Imaging

The evaluation of blood–brain barrier (BBB) integrity with contrast-enhanced magnetic resonance imaging (MRI) may prove valuable in the setting of certain brain pathologies, such as brain tumors and acute ischemic stroke. Various MRI protocols have been developed to explore the integrity of the BBB by monitoring the leakage of intravenously administered contrast medium into the brain parenchyma. In its simplest form, BBB integrity is assessed qualitatively, by determining the presence or absence of contrast-enhancement on a structural MR image. When a dynamic contrast-enhanced (DCE) MRI protocol is combined with a suitable pharmacokinetic model, DCE-MRI can map the spatial distribution of BBB integrity throughout the brain and assist with evaluating the effects of therapy. Several model-free surrogate measures of BBB permeability have been recently proposed, all of which can be readily computed from standard dynamic susceptibility contrast MRI perfusion scans. Contrast-enhanced MRI offers multiple strategies for evaluating BBB integrity.