Biomedical Engineering Reference
In-Depth Information
Fig. 12.3
Examples of spatial distributions of (
a
) WSS, (
b
) WSSG, (
c
)OSI,(
d
) min(AFI) and
(
e
) GON (
left
to
right
, respectively) for reconstructed healthy vessels without IAs. The
upper row
illustrates cases where a positive correlation between an index and the location an IA evolves
occurs whilst the
lower row
illustrates examples where no correlation is observed
to the known locations of aneurysm formation (LAF). Figure
12.3
illustrates ex-
amples of positive (upper row) and negative (lower row) correlations of the hemo-
dynamic indices WSS, WSSG, OSI, minimum(AFI) and GON with the LAF. We
observed that 19
/
22 IAs developed in regions that had locally elevated magnitudes
of WSS and GON. However, fewer positive correlations were observed for other
indices, i.e. 7
/
22 for elevated values of OSI, 7
/
22 for low values of min(AFI) and
8
/
22 for elevated values of WSSG.
Our study highlights that care should be taken when interpreting the conclusions
and findings of smaller CFD studies in the literature. For example, we observed
that low values of AFI were associated with 7
/
22 clinical cases whereas Mantha
et al. (
2006
) observed correlations in all cases (3
/
3). Singh et al. (
2010
) observed
a significant correlation with OSI (2
/
2) however we observed no such correlation.
Consistent with Baek et al. (
2009
) we observed a positive correlation with regions
subject to high WSS. Whilst we observed many positive correlations (19
/
22) with
elevated GON, as observed and remarked by Ford et al. (2009), this index is elevated
in many regions of the artery and thus the significance of this correlation is unclear
and may merit further investigation.
12.3 IA Enlargement
To further our understanding of the aetiology of IA we must further our understand-
ing of the physiological mechanisms that regulate the maintenance of arterial tis-
sue in physiological and pathophysiological conditions. The structure of the artery
is continually maintained by vascular cells. The morphology and functionality of
vascular cells is intimately linked to their mechanical environment. Hemodynamic
forces give rise to: cyclic stretching of the extra-cellular matrix (ECM); frictional
