Fractional Anisotropy as a Potential Marker of Blood–Brain Barrier Disruption in a Rat Model of Ischemia–Reperfusion Injury

While gadolinium-enhanced magnetic resonance imaging (MRI) enables assessment of blood–brain barrier (BBB) integrity post-stroke, it presents inherent risks and limitations. We evaluated diffusion tensor imaging (DTI) as a contrast-free method for monitoring BBB integrity during ischemia–reperfusion (I/R) in a rat stroke model. Seventeen Sprague–Dawley rats underwent one-hour transient middle cerebral artery occlusion (MCAO). Serial MRI sequences, including DTI, perfusion-weighted imaging, and T1 mapping, were performed to monitor BBB permeability (BBBP) dynamics in regions initially identified as ischemic penumbra (IP) and ischemic core (IC) during MCAO. The fractional anisotropy (FA) ratio (rFA) was compared with BBBP changes throughout the observation period. In the IC, rFA values exhibited a 13% increase during ischemia, followed by a 10% decrease post-recanalization, and a 36% decline at 120 h post-reperfusion. Although BBBP in the IC decreased during ischemia and normalized post-reperfusion, persistent leakage was observed. The IP maintained stable rFA and BBB integrity throughout I/R. Strong negative correlations between rFA and BBBP were found in ischemic regions (IC: r = − 0.90, p < 0.001; IP: r = − 0.78, p = 0.007), with FA reductions at 24 h post-reperfusion predicting BBB disruption at 120 h. These findings suggest that DTI metrics correlate significantly with BBB integrity during I/R, indicating potential utility as a contrast-free monitoring tool for early detection of BBB impairment following stroke.