Hydrodynamic Resistance of Intracranial Flow-Diverter Stents: Measurement Description and Data Evaluation

Abstract

Purpose Intracranial aneurysms are malformations forming bulges on the walls of brain arteries. A flow diverter device is a fine braided wire structure used for the endovascular treatment of brain aneurysms. This work presents a rig and a protocol for the measurement of the hydrodynamic resistance of flow diverter stents. Hydrodynamic resistance is interpreted here as the pressure loss versus volumetric flow rate function through the mesh structure. The difficulty of the measurement is the very low flow rate range and the extreme sensitivity to contamination and disturbances. Methods Rigorous attention was paid to reproducibility, hence a strict protocol was designed to ensure controlled circumstances and accuracy. Somewhat unusually, the history of the development of the rig, including the pitfalls was included in the paper. In addition to the hydrodynamic resistance measurements, the geometrical properties—metallic surface area, pore density, deployed and unconstrained length and diameter—of the stent deployment were measured. Results Based on our evaluation method a confidence band can be determined for a given deployment scenario. Collectively analysing the hydrodynamic resistance and the geometric indices, a deeper understanding of an implantation can be obtained. Our results suggest that to correctly interpret the hydrodynamic resistance of a scenario, the deployment length has to be considered. To demonstrate the applicability of the measurement, as a pilot study the results of four intracranial flow diverter stents of two types and sizes have been reported in this work. The results of these measurements even on this small sample size provide valuable information on differences between stent types and deployment scenarios.

Impact of Design and Deployment Technique on the Hydrodynamic Resistance of Flow Diverters

“…found that although the porosity is a key factor in determining the flow reduction capability of the device, it is solely not sufficient [ 8 ]. We argue, as in our previous paper that the really decisive factor is the HR [ 21 ], of which the porosity is only one element. In this sense our findings complement those of Augsburger et al.…”

“…The geometrical data of the deployed devices were obtained using image processing techniques described in detail in Csippa et al. [ 21 ]. The deployed stents at the elliptical hole of the holder tube were photographed using a USB microscope (Dino-Lite, Torrance, CA, USA).…”

A novel virtual flow diverter implantation method with realistic deployment mechanics and validated force response

“…Our aim is to reproduce the flow diverter surface accurately, since this virtual stenting method is integrated with our CFD solution, 41 which uses a porous material description of the FD surface. The last component, the porous flow resistance of various flow diverter types is measured and discussed in Reference [42].…”

Molecular Mechanisms in Early Diabetic Kidney Disease: Glomerular Endothelial Cell Dysfunction

“…The apical surface of the endothelial cells is covered by the negatively charged endothelial glycocalyx and endothelial surface layer (ESL), which cover and floats into the lumen of the capillary vessels, and is a key player in the integrity of the glomerular filtration barrier. The endothelial glycocalyx and ESL consist of glycoproteins and proteoglycans covalently linked to the glucosaminoglycans heparan sulfate, chondroitin sulfate and hyaluronic acid [ 25 ]. The importance of the glycocalyx in homeostasis has progressively been recognized, due in part to its high charge selectivity restricting the passage of negatively charged molecules such as albumin [ 23 ].…”