Currently, nonpulsatile selective cerebral perfusion for cerebroprotection against thoracic aortic aneurysm is used in clinical settings. We performed synchrotron radiation microangiography to determine the effects on selective cerebral perfusion modulation by pulsatile flow. We established cerebral perfusion at normothermia and severe hypothermia in anesthetized rats, during which cerebral angiography was performed. NG-nitro-L-arginine-methyl ester hydrochloride (L-NAME) was administered to determine the effect of pulsatile flow with nitric oxide synthesis. In comparison with nonpulsatile flow, the relative diameters of small internal carotid artery were 132.11 +/- 5.49 and 114.96 +/- 4.60 during pulsatile flow at normothermia and severe hypothermia (p <0.05). The angiographic scores, an indicator of vessel count, for nonpulsatile and pulsatile flow at normothermia were 0.198 +/- 0.013 vs. 0.258 +/- 0.010 (p <0.001) and those at severe hypothermia were 0.158 +/- 0.017 vs. 0.214 +/- 0.015 (p <0.01), respectively. In comparison with nonpulsatile flow, the relative internal carotid artery diameters during pulsatile flow with and without L-NAME were 98.50 +/- 1.7 vs. 114.96 +/- 4.6 , respectively, during severe hypothermia. These results show that pulsatile flow is effective in increasing blood vessel diameter, number of vessels, and perfusion distribution range in the rat model and that it was more effective at normothermia during nitric oxide production.