Network-Based Characterization of Blood Large-Scale Coherent Motion in
the Healthy Human Aorta with 4D Flow MRI
Abstract
Objective: The need for distilling the hemodynamic complexity
into clinically relevant quantities has imposed a reductionist approach
to investigate aortic flows, resulting in a lossy compression of the
information hidden in 4D aortic fluid structures. Aiming at reducing
information loss, this study proposes a network-based approach to
identify and characterize in vivo the large-scale coherent motion of
blood in the healthy human aorta using 4D Flow MRI. Methods:
Adopting the quantitative paradigm of the aortic flow as a “social
network”, 4D flow MRI acquisitions were performed on forty-one healthy
volunteers. Correlations between the aortic blood flow rate waveform at
the proximal ascending aorta (AAo), assumed as a main determinant of the
aortic flow, and the waveforms of the axial velocity (aligned with the
aortic centerline) in the whole aorta were used to build
“one-to-all” networks. The impact of the driving flow rate
waveform and of the main aortic geometric attributes on the transport of
large-scale coherent fluid structures was investigated.
Results: The anatomical length of persistence of large-scale
coherent motion was the 29.6% of the healthy thoracic aorta length
(median value, IQR 23.1%-33.9%). Moreover, it was positively
correlated with the average and peak-to-peak AAo blood flow rate values,
suggesting a remarkable inertial effect of the AAo flow rate on aortic
hemodynamic coherence. No association emerged between the anatomical
length of persistence and aortic geometric attributes.
Conclusion: The here proposed in vivo approach allowed to
quantitatively characterize the large-scale aortic blood motion,
strengthening the definition of coherent hemodynamic structures.
Significance: The findings on healthy aortas may be used as
reference values to investigate the impact of aortic disease or devices
implantation in disrupting/restoring the physiological spatiotemporal
coherence of large-scale aortic flow.