Past clinical and experimental evidence suggests that cerebral aneurysms can be successfully excluded from the circulation solely by the endovascular placement of a flow diverting device across the aneurysm neck. These devices promote intraaneurysmal flow stasis and concomitant thrombosis by redirecting flow away from the aneurysm. To comprehensively test the efficacy of such flow divertors, we are implanting devices with three different porosities in a large cohort of elastase-induced aneurysms in rabbits. Treatment efficacy is quantified by a mathematical model that is fit to aneurysmal angiographic contrast washout curves. Results from three animals implanted with different device porosities are presented here. The model competently captures the behavior of the aneurysmal washout curves and provides reliable indices of device efficacy. Preliminary analysis indicates that immediately after implantation, the device with medium porosity performs better than the devices with lower and higher porosities.