Development and assessment of a haemodynamic based numerical model for stenosis growth in the carotid artery

Abstract

A model for stenosis development in the carotid artery, employing the lattice Boltzmann method, is presented and its suitability is investigated and demonstrated. The development of a stenosis is modelled based on the blood flow; and the subsequent changes in the flow are examined. The model is applied to investigate the role of different haemodynamic markers on stenosis development and also the importance of modelling the non-Newtonian nature of the blood.
A stenosis growth model based on the time-averaged velocity magnitude at the wall is considered. The wall position where this marker has a minimum value is determined and the stenosis is allowed to develop at this point. The extent to which the stenosis develops is controlled by two parameters which are introduced. Simulations are then run based on the new geometry and a new position selected for stenosis development. The stenosis developed in this way was seen to be compatible with observations from the literature.
Simulations of stenosis development are presented to investigate the effect of the introduced model parameters to determine suitable ranges for their application. A range of parameters are determined over which the stenosis develops in an independent manner.
These parameters relate the extent to which the stenosis can grow in each development phase with no physical significance. It is important to find a variable which will describe the evolution in a manner which is independent of the model parameters.
As well as the time-averaged velocity magnitude, a selection of alternative markers were applied to the model. The results show that a number of markers involving near-wall velocity, wall shear stress, residential time, stagnation index and second invariant of the strain rate tensor, all resulted in a realistic stenosis. The oscillatory shear index, which gives a measure of the oscillatory nature of the shear, was found to not be a suitable marker, unless it was combined with the wall shear stress in the form of a ratio.
The effect of the non-Newtonian nature of blood on the stenosis development model is also considered. Here the non-Newtonian simulation showed noticeable differences compared to Newtonian; however both produced a realistic stenosis.

Date of Award	Jan 2016
Original language	English
Awarding Institution	University of Portsmouth
Supervisor	James Buick (Supervisor)