This project, still in its early stages, measures the vasoreactivity of the vasculature in the brain. This is a multi-modality project using magnetic resonance imaging (MRI) and transcranial Doppler (TCD) ultrasound to investigate autoregulation properties of the brain. Future progress will include computed tomography (CT) imaging to try to predict the outcome of patients presenting with stroke in the emergency room. To measure reactivity, all of these modalities will use either a chemical challenge such as Diamox (a vasodialator), a physical blood pressure challenge using cuffs, or a carbon dioxide (CO2) challenge from either breathing a mixed gas or breath holding. Using any of these imaging techniques, it is possible to measure the perfusion or velocity changes in order to determine how well the vasculature is able to handle the challenge (Figure 1). The goal is to eventually be able to predict a patient’s outcome based on their vasoreactivity.
One can also measure changes related to the introduction of chemicals such as caffeine to investigate their physiologic impact.
Figure 1: The vasoreactivity index as calculated by TCD, using blood pressure cuffs, is plotted over time relative to the ingestion of 200 mg of caffeine. Note that the velocities decrease but that the vasoreactivity index increases. This means that the vasculature is able to respond more quickly and strongly to a vascular challenge.
Figure 2: The velocity in the middle cerebral artery as measured by TCD following ingestion of 200 mg of caffeine. Note the large decrease in velocity about 30 minutes after taking the caffeine.
Northwestern University and Srico, Inc. are collaborating to investigate a new method of collecting electroencephalogram (EEG) signals using a fully optical device. This optical electrode, an optrode, is used primarily in many high-speed data transmission applications.