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Effect of the Flow Diverter Resistance On the Aneurysm Angiographic Time Density Curves

C Ionita

C Ionita*, D Bednarek, S Rudin, Univ. at Buffalo (SUNY) School of Med., Buffalo, NY

TU-A-218-3 Tuesday 8:00:00 AM - 9:55:00 AM Room: 218

Purpose: Flow diverters (FD) are new stent like devices used for selected intracranial aneurysms treatment. The devices are in their initial clinical use and the relation between device parameters, physiological implications and treatment outcome needs to be further investigated. Flow resistance is a parameter which could be used to characterize the device flow induced modifications. The purpose of this study is to investigate the relation between FD flow resistance and physiological aneurysmal blood flow modification using time density curves (TDC's) derived from high speed angiograms.
Material and Methods: Six bifurcation aneurysm phantoms were treated with stainless steel wire meshes to simulate various FD's. The FD resistance was calculated using a semi-empirical model dependent on the device porosity, flow conditions and device strut diameter. Contrast time density curves (TDC's) were measured in a region-of-interest which included the entire aneurysm volume, using high-speed x-ray angiographic image sequences. In each TDC we measured bolus peak, input flow slope (IFS), the mean transit time (MTT), and time to peak (TTP). The treated aneurysm TDC's parameters were normalized to the untreated case. The flow model assumes that the ratio of the pressure drop and velocity square is proportional with the resistance. The model validity was demonstrated by verifying the linear dependence of TDC parameters of the inverse square root of the device flow resistance.
Results: The observed flow changes correlated linearly with the FD flow resistance. For flow resistances larger than 20 the contrast entering the aneurysm was negligible. The linear fit results yielded R^2 values of 0.99 for the peak, 0.93 for the IFS, 0.93 for TTP and 0.94 for the MTT.
Conclusions: The FD flow resistance correlates strongly with all TDC parameters, indicating that it could be used to predict blood flow physiological changes in aneurysms treated with FD's.

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