Based on those studies, the investigators hypothesized that intensive rosuvastatin may also improve the symptoms of AICAS not only through enhancing the stability of atherosclerotic plaques, but also its pleiotropic effects. So it can change the hemodynamic status around the plaque and increase cerebral flow in the downstream territory. So in this study the investigators try to analysis statin's impact on the hemodynamic changes as well as the downstream perfusion which is determined by CTP.