MRI Tool Helps Spot Damage to Blood-Brain Barrier in Stroke

A software tool that applies an arrival time correction (ATC) to dynamic susceptibility contrast (DSC) magnetic resonance permeability imaging may provide a more accurate picture of damage to the blood-brain barrier (BBB) in patients with acute ischemic stroke, researchers say.

More precise information on the extent of damage to the BBB may help predict and reduce the risk for complications, particularly intracranial hemorrhage, from thrombolytic therapy, ultimately leading to better outcomes, they say.

Better characterization of BBB damage also "opens the door to new approaches to treating stroke patients," Richard Leigh, MD, assistant professor of neurology and radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, who led the research, said in a statement.

Their report was published online December 20 in PLOS One.

BBB Disruption

For this study, the researchers adapted standard DSC MRI to incorporate a correction for delayed contrast delivery due to perfusion deficits seen in patients with stroke.

They applied the technique to the MRI examinations of 9 patients with stroke known to have BBB disruption on the basis of T1 postcontrast imaging. They compared regions of BBB damage with normal tissue from the contralateral hemisphere and performed receiver-operating characteristic (ROC) analysis to compare the detection of BBB damage before and after ATC.

The researchers report that the area under the curve (AUC) of the ROC for the uncorrected method was 0.53. Applying ATC improved the ability to detect BBB disruption to an AUC of 0.70.

With ATC, sensitivity improved from 0.51 to 0.67 and specificity improved from 0.57 to 0.66.

The ROC analysis also suggests that in the absence of ATC, DSC MRI "can be worse than random guess at identifying damage to the BBB," the researchers say.

However, this is "not unexpected," they note, "since perfusion deficits, when not corrected for, can be erroneously identified as permeability derangements due to assumptions of the model."

"Specifically," they explain, "the model assumes that the shape of the curve of the recorded signal will be the same throughout the brain, even in hypoperfused tissue. In reality, the recorded curve in hypoperfused tissue has a different morphology. Thus, ATC of the recorded curve adjusts its morphology and improves the performance of the model."

Dr. Leigh and colleagues point out that their study does not investigate the role of BBB in patients with stroke and was not designed to validate the use of DSC MRI to detect damage to the BBB. The study also does not provide any information on how DSC MRI permeability measures might be used in patients with acute stroke. "These are all important questions that will need to be addressed in future studies," the researchers say.

"Despite its limitations, this study serves to describe a technique for ATC of DSC MRI permeability imaging which can be further tested in subsequent studies," they conclude. The researchers are now testing their software tool on a larger group of patients with stroke.

The study had no funding, and the authors have disclosed no relevant financial relationships.

PLOS One. Published online December 20, 2012. Abstract