An αvβ3-specific Fe3O4-RGD nanoprobe was prepared for MR imaging of the collaterals during AIC. The MCAO rat models were constructed for imaging studies on 7.0-T MRI. To show the binding specificity to the collaterals, the imaging results acquired with the Fe3O4-RGD nanoprobe, Fe3O4 mother nanoparticles and RGD blocking experiment. Cerebral ischemia-reperfusion studies were also performed to show the collateral dynamics upon reperfusion. The studies have the first-time enabled the direct observation of collaterals in a quasi-real time fashion and further disclosed that the antegrade flow upon reperfusion dominates the blood supply of primary ischemic tissue during early stage of infarction.