Angiographic analysis of blood flow modification in cerebral aneurysm models with a new asymmetric stent

Abstract

We have built new asymmetric stents for minimally invasive endovascular treatment of cerebral aneurysms. Each asymmetric stent consists of a commercial stent with a micro-welded circular mesh patch. The blood flow modification in aneurysm-vessel phantoms due to these stents was evaluated using x-ray angiographic analysis. However, the density difference between the radiographic contrast and the blood gives rise to a gravity effect, which was evaluated using an initial optical dye-dilution experiment. For the radiographic evaluations, curved-vessel phantoms instead of simple straight side-wall aneurysm phantoms were used in the characterization of meshes/stents. Six phantoms (one untreated, one treated with a commercial stent, and four treated with different asymmetric stents) with similar morphologies were used for comparison. We calculated time-density curves of the aneurysm region and then calculated the peak value (Pk) and washout rate (1/τ) after analytical curve fitting. Flow patterns in the angiograms showed reduction of vortex flow and slow washout in the dense mesh patch treated aneurysms. The meshes reduced Pk down to 21% and 1/τ down to 12% of the values for the untreated case. In summary, new asymmetric stents were constructed and their evaluation demonstrates that they may be useful in the endovascular treatment of aneurysms.

The Asymmetric Vascular Stent

“…We reported two orders of magnitude decrease in the velocity and vorticity, and reduced aneurysmal wall shear stress. Additionally, in-vitro angiographic studies using the AVS14, 18 demonstrated drastic reduction of iodine contrast in the aneurysm dome and prolonged contrast presence following injection, signifying decreased flow within the aneurysm.…”

“…Intracranial aneurysm (IA) treatment using flow alteration induced by stents is a subject studied intensely by a number of endovascular research groups 1-18. The primary hypothesis is that flow diversion can induce intra-aneurysmal thrombus formation thereby resulting in aneurysm exclusion from the circulation 19.…”

Treatment of Rabbit Elastase-Induced Aneurysm Models by Flow Diverters: Development of Quantifiable Indexes of Device Performance Using Digital Subtraction Angiography

“…Certain studies have suggested that, especially in intracranial aneurysms, the transport of contrast does not follow the transport of blood. Due to its higher density, contrast is said to settle out of the blood in the gravity direction within aneurysm sacs [22, 23]. This notion has not been borne out by experiments conducted to investigate the mixing of angiographic contrast with blood under conditions similar to most cerebral angiographic acquisitions [24].…”

Cerebral Endovascular Neurosurgery

“…This stent has a significant advantage over the Neuroform stent in that it is 80% resheathable into the delivery microcatheter. Asymmetric stents in which a portion of the stent is covered with a low-porosity, stainless steel patch may be useful in regions with high perforator densities (62,70,81,82,122,153). Telescoping stents or unique stent strut designs may also prove to be useful techniques for flow diversion without the need for coiling (74).…”