Title:
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The Effects of Elastic Compression on the Lower 'Limb Venous System
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Deep vein thrombosis is a common disease with potentially serious outcomes, including death from
pUlmonary embolism. One of the most widely used forms of prophylaxis is the compression stocking.
However, the source of its beneficial effect is poorly understood, hindering improvements in design
and application. In this study, a novel approach of subject specific computational modelling, based on
magnetic resonance (MR) images, is used to quantify the effects of a grade 1 compression stocking
on the venous system of the calf. The focus is the development of methodologies which allow the
quantification of biomechar)ical parameters implicated in biological models of the disease.
pathophysiology.
MR images were acquired from the calves of eight healthy subjects, before and after application of
the stocking. The geometry of major deep and superficial veins was then reconstructed in order to
quantify the deformations induced by the stocking. Following this, computational fluid dynamics was
used to determine the changes to haemodynaniic wall shear stress (WSS), based on observed
changes to vessel geometry and sUbject specific velocity waveforms, acquired using Doppler
ultrasound. It was found that the stocking was effective at raising WSS in both deep and superficialveins
but the effect was more pronounced in the deep veins. Changes to the velocity waveforms due
to stocking application were also obserVed which limited the time during which the veins experienced
very low WSS.
. 11\ finite element (FE) based non-rigid registration algorithm was then developed to calculate the
stresses induced in the skeletal muscle by the stocking. The method was used to compare calculated
values of hydrostatic pressure with the observed reduction in cross sectional area. The results
suggest the method possesses some predictive ability but with low sensitivity. Finally the ability of a
basic model of the vein wall to predict the observed deformations is examined.
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