Stroke is the second leading cause of death in Taiwan. The morbidity and mortality of stroke is also very high worldwide. In the United States, about one third of 800,000 stoke patients became disabled; while in Taiwan, 13,000 out of 68,000 stroke patients died each year.~Diffusion tensor imaging (DTI) characterizes the three-dimensional distribution of water diffusion, which is highly anisotropic. Previous studies utilized DTI derived mean diffusivity (MD) and fractional anisotropy (FA) have found correlation between pathological changes of white matter and prognosis of stroke. However, the result was not specific due to the reason that any change at either axon or myelin sheath resulted in FA reduction. DTI, on the other hand, differentiate morphological change at axon and myelin sheath with axial and radial diffusivity, respectively. With this data, we hypothesized that the prognosis might be more relevant to pathological change with axon post-stroke when compare to Diffusion-Weighted imaging (DWI)/Apparent Diffusion Coefficient (ADC).~Susceptibility-weighted imaging (SWI) is a newer technique which use fully velocity compensation gradient echo sequence to receive magnitude and phase imaging. SWI can be used to detect early phase bleed, intra-arterial thrombus, cerebral venous thrombosis, thus evaluate the prognosis of patients by detect leptomeningeal collateral circulation and intravascular deoxygenation changes. We hypothesized that the prognosis is better in post-stroke patients with preserved leptomeningeal collateral circulation and venous circulation of large blood vessel. Therefore, we conduct the study to use DTI derived axial diffusivity and SWI to evaluate the severity and to predict the functional outcome in acute ischemic stroke patient.
The purpose of the study is to use diffusion tensor imaging (DTI) derived axial diffusivity and susceptibility weighted imaging (SWI) to evaluate the severity of acute ischemic stroke and to predict its functional outcome.