Biomedical Engineering Reference
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varying throughout the main cycle. Given that only one dominant vortex has been
visualised for the time segment of the cardiac cycle, it appears that the presence of
the weaker, clockwise vortex can be attributed to the peaking of IVC in-flow during
atrial diastole. The potential extensive datasets from the CFD simulations and phase
contrast MRI can allow further insight into the vortex structures present in the right
atrium flow.
The Reynolds numbers are typically lower towards end-systole and early diastole
due to the slower motion of blood. The blood flow is transitionally turbulent during
the onset of systole. The blood inflow velocities at the superior and inferior vena
cava tends to increase during the period of systole and causes a collision within the
atrium, which generates a turbulent flow that comprise of two large-scale vortices.
The range of Reynolds numbers in the atrial flow throughout one cardiac cycle is
both laminar and turbulent. The simulation results are largely in agreement with the
MRI results. In terms of the flow features, the velocity vectors implied that the flow
is moving primarily in the anti-clockwise direction. Partly as a consequence, there
is a dominant vortex core-like structure that remained throughout the cardiac cycle.
That this dominant vortex showed a positional dependence on the TV outlet.
In terms of clinical applications, medical imaging modalities such as multislice
CT and MRI have been increasingly used to diagnose cardiovascular disease owing
to rapid technical developments. Despite the improvements in CT, its application
in cardiovascular disease is limited for evaluating the morphological changes of
cardiac chambers. However, functional MR imaging, especially phase-contrast-
MRI allows for both anatomic and functional assessment of cardiovascular disease,
and demonstrates huge potential in the clinical practice. Analysis of haemodynamic
flow through the heart will assist clinicians to better understand the formation of
thrombosis, and the effect of flow on arterial branches arising from the heart, which
helps to avoid atherogenicity (Friedman et al. 1993). Therefore, future studies
involving CFD analysis of bilateral heart chambers that include both venous inflow
and arterial outflow will be clinically meaningful.
7.5.5
Closure
In this case study, the flow pattern development in a chamber of the heart based on
phase contrast magnetic resonance imaging and numerical simulation was com-
pared. For the computational study, a static geometry was assumed and dynamic
flow boundary conditions in a series of surface geometries pertaining to different
times of a cardiac cycle was applied. Although the fluid structure interaction of
the blood-wall region is neglected, the generated flow fields did not deviate sig-
nificantly from the true physiological flow. Experimental study is based on in-vivo
magnetic resonance-based flow imaging.
The flow visualization tools using streamline tracing and vorticity field enabled
the presentation of our results effectively. Vortices exist in three spatial dimensions,
but we have simplified our analysis to present two dimensional results for clarity in
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