Visualization and Quantification of Helical Flow in the Aorta using 4D Flow MRI

Sammanfattning: Due to the complex anatomy of the heart, heart valves and aorta, blood flow in the aorta is known to be complex and can exhibit a swirling, or helical, flow pattern. The purpose of this thesis is to implement methods to quantify and visualize both the speed of helicity, referred to as the helicity density, and the direction of helicity, which is measured by the localized normalized helicity. Furthermore, the relationship between helicity and geometrical aorta parameters were studied in young and old healthy volunteers. Helicity and geometrical parameters were quantified for 22 healthy volunteers (12 old, 10 young) that were examined using 4D Flow MRI. The relation between helicity and the geometry of the aorta was explored, and the results showed that the tortuosity and the diameter of the aorta are related to the helicity, but the jet angle and flow displacement do not appear to play an important role. This suggests that in healthy volunteers the helical flow is primarily affected by the geometry of the aorta, although further trials should be performed to fully characterize the effects of aortic geometry. The results also show that the helicity changes with age between the two age groups and some of the geometrical parameters also has a significant difference between the age groups.