Andrea Para MSc, Presenter: Nothing to Disclose

Julien Poublanc MSc, Abstract Co-Author: Nothing to Disclose

Joseph A. Fisher MD, Abstract Co-Author: Stockholder, Thornhill Research Inc

David John Mikulis MD, Abstract Co-Author: Stockholder, Thornhill Research Inc Research Grant, General Electric Company

Activated neurons in the brain send a vasodilatory stimulus to surrounding blood vessels to increase supply of oxygen and glucose to meet metabolic demands. Functional magnetic resonance imaging (fMRI) uses blood oxygen level dependent (BOLD) contrast to detect changes in blood flow based on differences in the magnetic properties of oxygenated versus deoxygenated hemoglobin, and then infer neuronal activity from the observed changes in blood flow. Cerebrovascular reactivity (CVR) is the ability of arterioles to increase blood flow in response to a global vasodilatory stimulus. CVR can be reduced or exhausted in steno-occlusive cerebrovascular disease resulting in blunted increases in blood flow, or even decreased blood flow due to steal physiology. We hypothesize that in areas with exhausted vascular reserve and steal physiology there will be diminished blood flow response following neuronal activation, and that these areas would appear as false negatives on traditional BOLD fMRI.

Patients with unilateral steno-occlusive disease received a vasodilatory stimulus during BOLD MRI to generate CVR maps. These were compared to traditional BOLD fMRI maps of neuronal activation in the motor cortex in response to a motor task. Neuronal activation from the motor task was found to be linearly correlated with CVR (n=11 patients, R= 0.82). Patients with positive (normal) CVR showed positive activation on BOLD fMRI, while patients with negative CVR had decreased or absent neuronal activation on BOLD fMRI.

Activated neurons send a vasodilatory stimulus to surrounding blood vessels, and the corresponding increase in oxyhemoglobin levels is the basis of the BOLD signal. In areas with cerebrovascular disease where CVR is impaired there is uncoupling of neuronal activation and blood flow that results in false negative errors on BOLD fMRI.

BOLD MRI CVR mapping can provide spatial information about the vascular reactivity of the brain that is essential to interpreting traditional BOLD fMRI studies in the setting of cerebrovascular steno-occlusive disease.

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Para, A, Poublanc, J, Fisher, J, Mikulis, D, Reliability of fMRI Experiments in the Setting of Neurovascular Uncoupling.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018023.html