Investigation of the Boundary Layer Blood Flow and the Initial Factors of Atherosclerosis by the Magnetic Resonance Imaging

Aim: study the blood flow and vessel wall viscoelastic alterations at the boundary layer and initial
factors of atherosclerosis.
Study Design: Magnetic resonance angiography with the follow up flow quantification was carried out
voluntary on the healthy persons.
Place and Duration of Study: MRI department of the Institute of Clinical Medicine in Tbilisi Rep.
Georgia, between September 2012 and July 2017.
Methodology: In 12 healthy men (18-52 years of age) at the different sites of the aorta peak velocity,
net flow, flow acceleration has been investigated by Magnetic Resonance Angiography. Blood
radiodensity (HU) were studied (CT) in different sites of the aorta and vena cava.
Results: In the aortic arch in the end systole blood flow separates into the opposite directed streams
resulting in the wave superposition. At the outer curvature of the isthmus, flow acceleration in the
initial diastole is 6.26 times higher than that in systole. Net flow from systole to diastole increases
2.5±0.5 folds. From the end systole to the initial diastole there is a plateau on the net flow graph. At
the outer curvature of isthmus, group wave at the boundary reflection, changes in phase at 180°. At
the same time flow wave oscillation frequency at the outer curvature is two times higher (1.6Hz.) than
that at the inner (0.8Hz).
Conclusion: During the heart cycle, blood motion at the boundary layer, forms the surface wave and
facilitates the blood structural rearrangement and flow. At the end systole, at the outer curvature of the
isthmus, pulse pressure at the reflection is in the resonance with the end systolic pressure drop.
Amplitude of the wall stress increases. Forming standing wave leads to the dissipation of the wall’s
mechanical energy. Here, at the initial diastole, group wave, due to the wave reflection, and frequency
dispersion, facilitates to the structural rearrangement/denudation of the vessel wall.