fMRI assessment of ischemic stroke in humans

Cerebral ischemia, or brain ischemia is a kind of stroke where the blood flow is insufficient to the metabolic demand of brain. The lack of oxygen supply will directly lead to the death of brain tissue. There are two major injury regions: the infarct and penumbra. Mostly, since the infarct regions became dead tissues rapidly after stroke, there is a tiny possibility to rescue them in time. But penumbra parts are different. Tissues there will be viable for hours after ischemia. Hence, both theoretically and practically, it is possible to salvage those cells in the penumbra region. Diffusion weighted image (DWI) is a widely used and robust tool to detect ischemia lesions. Unfortunately, DWI can only quickly and accurately detect the location of lesions, however, it cannot distinguish the infarct and penumbra, which is vital to act on further treatment. The main goal of this study is that the functional MRI data can be used to obtain both structural and functional information about lesions in stroke patients. It was hypothesized that the lack of oxygen supply might be directly caused by lower level rate of blood flow, which can be traced by blood-oxygen-level-dependent (BOLD) signal. Hence, through working on the functional MRI data, it is possible to find the difference between infarct and penumbra. Through different kinds of algorithms, the functional MRI data can find certain levels of difference between the ischemic lesions and normal tissues