Changes in contrast dye washout due to stenting of sidewall and bifurcation aneurysms: A preliminary study

In vitro and in vivo experiments, along with preliminary clinical studies, have shown that stent placement across the ostium of an aneurysm can significantly reduce intraaneurysmal flow. This reduction in intraaneurysmal flow can lead to the formation of a stable thrombus within the aneurysmal sac. A minimally invasive, curative treatment is the exclusion of the aneurysm from the circulation and restoration of normal physiological flow within the parent artery. Therefore, bypass of aneurysms by stenting appears to be the ideal endovascular treatment for remodeling of cerebral arterial segments. This study examined the washout of contrast dye from both in vitro and in vivo aneurysms. The in vitro part of this study was performed utilizing a model of a sidewall aneurysm constructed from Sylgard 184 (Dow Coming Corp., Midland, MI). Venous pouch aneurysms were constructed bilaterally in mongrel dogs at the maxillary artery (MA)-sublingual artery (SLA) bifurcation to evaluate dye washout in vivo. Using digital subtraction angiography (DSA), soluble contrast media was injected in both the in vitro and in vivo aneurysm models before and after stent placement. Data analysis included the determination of the region of interest (ROI) that was limited to the aneurysm sac. Thereafter, average gray scale levels of the ROI were obtained in successive angiographic images. The transient changes of the average inverted gray scale value within the aneurysmal sac were subjected to mathematical modeling. The model attempts to capture the physical mechanisms by which contrast washes out of the aneurysm. The proposed technique establishes a methodology for obtaining quantitative dye transport information from angiographic data. The results show that the model enables the evaluation of changes in contrast washout from the aneurysm due to stenting.