COMPARISON OF VARIOUS DISTRIBUTONS USED FOR COLLAGEN FIBRE ORIENTATIONS IN ARTERIAL LAYERS

To consider tissue anisotropy in computational models of arterial wall, information on directions of collagen fibres and their dispersion in the individual layers of the wall is needed. Many papers introduce the assumption of two fibre families although its experimental substantiation is poor. In this paper we analyse data on direction distribution of collagen fibres published in several papers, in contrast to their authors, without any anticipatory assumptions. Histograms and their different mathematical representations are compared by means of coefficient of determination R-2 to obtain the best representation of the experimental data. The results show that in most of the analysed cases other distributions give better representation of the experimental data; specifically, the presented bimodal fit was surpassed with uni-, tri- or quadri-modal distributions or even with isotropic distribution with a large noise. This effect could be even enhanced when information criteria were applied. Finally, the best mathematical representations of the data (the best fits) are transformed into parameters used by anisotropic constitutive models in FEM analyses.