Prediction of fibre architecture and adaptation in diseased carotid bifurcations

Abstract

Many studies have used patient-specific finite element models to estimate the stress environment in atherosclerotic plaques, attempting to correlate the magnitude of stress to plaque vulnerability. In complex geometries, few studies have incorporated the anisotropic material response of arterial tissue. This paper presents a fibre remodelling algorithm to predict the fibre architecture, and thus anisotropic material response in four patient-specific models of the carotid bifurcation. The change in fibre architecture during disease progression and its affect on the stress environment in the plaque were predicted. The mean fibre directions were assumed to lie at an angle between the two positive principal strain directions. The angle and the degree of dispersion were assumed to depend on the ratio of principal strain values. Results were compared with experimental observations and other numerical studies. In non-branching regions of each model, the typical double helix arterial fibre pattern was predicted while at the bifurcation and in regions of plaque burden, more complex fibre architectures were found. The predicted change in fibre architecture in the arterial tissue during plaque progression was found to alter the stress environment in the plaque. This suggests that the specimen-specific anisotropic response of the tissue should be taken into account to accurately predict stresses in the plaque. Since determination of the fibre architecture in vivo is a difficult task, the system presented here provides a useful method of estimating the fibre architecture in complex arterial geometries.

A remodelling metric for angular fibre distributions and its application to diseased carotid bifurcations

“…In a previous study (Creane et al 2010b), the fibre architecture in four patient-specific models of the carotid bifurcation was predicted using the same remodelling algorithm as described in Sect. 2.3.…”

“…An optimum H f am_i H O P f am_i for each family of fibres is calculated at every iteration of a remodelling step using a strainbased remodelling algorithm. The existing value of H f am_i is then remodelled towards H O P f am_i using a rate equation discussed in Creane et al (2010b).…”

“…The remodelling algorithm used has been described previously in Creane et al (2010b) and is summarised here briefly. Remodelling of each family of fibres is facilitated by updating the structural tensor H f am_i for each family of fibres.…”

“…In this paper, its utility is demonstrated by considering the change in fibre architecture during a period of plaque growth in finite element models of sixteen patient-specific carotid bifurcations. The fibre architecture is predicted using a strain-based remodelling algorithm recently proposed in Creane et al (2010b). We investigate its potential as a clinical indicator of plaque vulnerability by comparing results between eight symptomatic and eight asymptomatic carotid bifurcations.…”

Vascular Stent Design Optimisation Using Numerical Modelling Techniques

“…The real power of these models will only be fully realised when inter-patient variability can be incorporated into the models, thereby generating similar data to clinical trials where the probability of stent success in a large population is determined rather than simply one clinical outcome. This can be achieved using patient-specific geometry and material properties in numerical models of stents and such data can currently be obtained from non-invasive medical imaging techniques (Creane et al, 2010). Variations in patient growth responses, and even genetic information can be used to inform such stochastic models (Nowlan & Prendergast, 2005) with advances in computational techniques possibly enabling lesion and patient-specific stents to be designed and manufactured for such patients on the basis of the model results.…”