November 16, 2010

MRI Images Provide Insight Into Strokes in Mice, Humans

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With their work based on different campuses, two University researchers are teaming up to revolutionize the use of  Magnetic Resonance Imaging (MRI) in stroke research. Prof. Henning Voss, physics in radiology, of Weill Cornell Medical College and Prof. Chris Schaffer, biomedical engineering (BME), are developing the first functional, noninvasive MRI technique for studying small-scale strokes in mice, which could eventually be used for clinical research in humans.

The research will be funded with a $1 million grant through the Samuel C. and Nancy M. Fleming Research Scholar Award in Intercampus Collaborations. ­While most MRIs provide a snapshot of the brain at one particular moment, functional MRIs provide a view of brain function over time, with an image for every second over that period of time.

Voss and Schaffer want to investigate both the immediate and long-term effects of two types of strokes: hemorrhagic strokes — micro-strokes that occur when a blood vessel bursts, leaking blood — and ischemic strokes, during which a blocked blood vessel deprives surrounding tissue of blood.

After inducing small strokes by using optical imaging and lasers to create precise lesions in single blood vessels — a technique Schaffer developed — Voss’ lab will perform functional MRI scans before and after to see how the brain responds overall.

Initial functional scans of the brains of mice have been effective and informative. Anesthetized mice stimulated on the left hind limb have been shown to have a brain response in the right somatosensory cortex and in other subcortical regions, according to Voss.

“Optical imaging techniques are not good at looking at how larger-scale changes occur, how activity patterns in other parts of the brain change, but functional MRIs can look at how more global functions of the brain are affected,” Schaffer said.

Voss and Schaffer will also investigate whether each type of induced stroke leaves a “fingerprint” on the rodents’ brain function to see if this fingerprint has an immediate effect or one that becomes evident during recovery.

The researchers want to look at how small-scale strokes are related to cognitive decline. “As MRI scanners become more sensitive,” Voss explained, “the signatures of micro-vascular lesions can now frequently be seen as incidental findings in cognitively normal people. As long as the density of these lesions is small, the brain can cope, but as their density goes up, there could be some direct or indirect cognitive effect.”

According to Voss, successfully using this method on mice will mean that clinical research on humans is possible in the near future. “Such a method will teach us what to expect in clinical applications of functional MRI in small-scale strokes,” Voss said, “and thus provide a first step toward the translation of these new stroke models into clinical research on humans.”

Original Author: Maria Minsker