Assessment of contrast flow modification in aneurysms treated with closed-cell self-deploying asymmetric vascular stents (SAVS).

The Asymmetric Vascular Stent (AVS) for intracranial aneurysm (IA) treatment is an experimental device, specially designed for intra-aneurysmal blood flow diversion and thrombosis promotion. The stent has a low-porous patch to cover only the aneurysm neck while the rest of the stent is very porous to avoid blockage of adjacent branches. The latest AVS design is similar to state-of-art, closed-cell, self-expanding, neurovascular stent. The stents were used to treat sixteen rabbit-elastase aneurysm models. The treatment effect was analyzed using normalized-time-density-curves (NTDC) measured by pixel-value integration over a region-of-interest containing the aneurysm. Normalization constant was the total bolus injection determined angiographically. Based on NTDC measurement, five quantities were derived to describe the contrast flow. Two are related to the amount of contrast entering the aneurysm: NTDC peak and NTDC input slope. The other three are related to contrast presence in the aneurysmal dome: time-to-peak (TTP), wash-out-time (WOT) and mean-transit-time (MTT). Flow modification descriptions using the contrast related quantities were expressed as a pre-/post-stented NTDC parameter ratio, while the time related quantities were expressed as a post-/pre-stented ratio, so that ratios smaller than one indicate a desired effect. Thirteen aneurysms were treated successfully and achieved significant aneurysm occlusion. For these cases, the resulting average parameters were: peak-ratio=0.17±0.21; input-slope-ratio=0.19±0.24, TTP-ratio=0.17±0.21, WOT-ratio=0.58±0.73 and MTT-ratio=0.65±0.97). All the quantities revealed decreased aneurysmal flow due to blood flow diversion using the new self-expanding asymmetrical vascular stent (SAVS). Treatment outcome results and angiographic analysis indicate that the new self-deploying stent design has great potential for clinical implementation.