Grant: Project Grant

Stroke is a leading cause of brain impairment, affecting more than 7% of Canadians over 65. Stroke occurs when blood stops flowing to a region of the brain, such as when a clot blocks a vessel, preventing oxygen and nutrients from reaching the region, and resulting in the death of brain cells. In some cases, physicians can intervene early to remove the blockage, minimizing the effects of the stroke and maximizing opportunities for recovery. Yet, many patients still have sensory, motor, or cognitive impairments, requiring significant long-term support. The cause of these lasting disabilities is likely that the blood flow does not fully return to normal in the network of small vessels that supply the brain tissue. However, we have not hitherto had a technology to observe how the small vessel flow is affected by the blockage and removal of occlusion. To meet this need, we are developing micro-ultrasound imaging tools that can visualise the tissue in and around the stroke region while also measuring blood velocity in individual larger and smaller vessels. Our method uses injected ultrasound contrast agents that are made to vibrate at low frequency , with much higher vibration harmonics detected by another transducer. With this method, not only is resolution dramatically improved compared to clinical ultrasound imaging, but "background" signal from tissue is virtually eliminated, resulting in high contrast images of the small vessels. We will optimise the ultrasound probes and imaging techniques for imaging the brain vessels in a rodent model of stroke, then investigate the changes in blood flow patterns across the network of blood vessels as stroke progresses. Through this work, we will establish the first model of the vascular network response to stroke and provide an imaging platform that can be used in future studies to assess effectiveness of new stroke treatments in re-establishing flow through smallest brain vessels.