Evaluating the Effectiveness of Coil Embolization Endovascular Therapy in Reducing Wall Stresses in Patient Specific Intracranial Aneurysms: A Nonlinear Computational Sensitivity Study
Abstract (Summary)Endovascular coiling therapy has gained widespread acceptance as a safe and efficacious method of intracranial aneurysm repair. However, aneurysm recurrence rates (15% -30%) associated with this therapy is very high. One possible reason for the high recurrence rates could be due to the treatment only aiming at reducing blood flow to the aneurysmal sac; the effectiveness of the procedure in unloading the aneurysm wall from the internal pressures that induce biaxial stresses in the wall of the aneurysm has not been considered while designing these endovascular devices. Our hypothesis is that the morphology of the fill-state achieved at the time of treatment and mechanical properties of the coil and thrombus complex have a significant effect on the therapy being able to reduce aneurysmal wall stress. A method for reconstructing 3D patient-specific CAD models form 2D CT angiography images is presented here. Various fill-states (fully-filled, half-filled and dog-eared fill states) were tested and a wide range of mechanical properties (moduli varying from E=0.005-1MPa) of the clot-thrombus complex were used in the nonlinear computational finite sensitivity study. An exponential material model, which is equivalent to the more prevalent Fung type material model, is used to model the aneurysm wall. An approximate neo-Hookean model was used for the coil-thrombus complex, due to lack of available data on clot-thrombus mechanical properties. Results showed that the fully-filled state was superior to the other fill-states in reducing aneurysmal wall stress and they were more effective when moduli of the coil-thrombus composite was 0.1 MPa or greater. Future research should be aimed at characterizing the coil-thrombus complex, in order to obtain a more accurate material model, which would in turn predict aneurysmal wall stresses more accurately. The first step taken to this end in our laboratory, was an ex vivo study conducted to study the mechanical properties of plain thrombus.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/2008