Magnetic resonance imaging temporarily alters blood-brain barrier permeability in the rat.

Exposure to a short (23.2 min) standard clinical magnetic resonance imaging (MRI) procedure elicits a temporary dysfunction of the blood-brain barrier in rats. Monitoring of the increased permeability of rat brain frontal cortex microvessels with the protein tracer horseradish peroxidase and freeze-fracture electron microscopy, revealed an amplified vesicle-mediated transport of tracer across the microvessel endothelium to the albuminal basal lamina and extracellular compartment of the brain parenchyma. Recovery of normal blood-brain function, as evidenced by exclusion of protein tracer from subendothelial basal lamina and neuropil extracellular milieu, was complete 15-30 min following cessation of the MRI exposure. These findings raise the possibility that exposure to clinical MRI procedures may also temporarily alter central blood-brain permeability in human subjects.