Analysis of morphological and hemodynamical indexes in abdominal aortic aneurysms as preliminary indicators of intraluminal thrombus deposition.

Abstract

In this paper, we study the correlation between the wall shear stress, a hemodynamical index derived from numerical simulations, and an new index MFA-ILT for the characterization of intraluminal thrombus (ILT) in the presence of abdominal aortic aneurysms. Based on the processing of medical images, we define our index MFA-ILT by projecting onto lumen surface a measure of the ILT thickness. From the physical point of view, hemodynamical indexes describe the mechanical stimuli at which the luminal surface of the vessel wall is subject to, due to blood flow. Specifically, we consider the time-averaged wall shear stress and the oscillatory shear index. The first index provides a measurement of the averaged magnitude of the shear stress; the second index measures the rate of change of shear stress. To reconstruct the hemodynamical indexes, we build in silico three-dimensional models. We use the same physical parameters and boundary conditions for all the aneurysms in the sample. The computer simulations do not require any additional invasive patient examination. We consider eleven cases of abdominal aortic aneurysms spanning a wide range of different morphological features. All the cases are characterized by a thin intraluminal thrombus. We can, therefore, assume that the lumen we currently observe does not significantly differ from the one before the thrombus deposition. Our results suggest that the value of wall shear stresses and intraluminal thrombus deposition are correlated. Moreover, we conclude that in six cases time-averaged wall shear stress provides a preliminary indication of the area at risk of thrombus deposition.