In-vitro and In-Vivo Assessment of 4D Flow MRI Reynolds Stress Mapping for Pulsatile Blood Flow

Abstract

Imaging hemodynamics play an important role in the diagnosis of abnormal blood ?ow dueto vascular and valvular diseases as well as in monitoring the recovery of normal blood ?owafter surgical or interventional treatment. Recently, characterization of turbulent blood ?owusing 4D ?ow magnetic resonance imaging (MRI) has been demonstrated by utilizing thechanges in signal magnitude depending on intravoxel spin distribution. The imagingsequence was extended with a six-directional icosahedral (ICOSA6) ?ow-encoding tocharacterize all elements of the Reynolds stress tensor (RST) in turbulent blood ?ow. In thepresent study, we aimed to demonstrate the feasibility of full RST analysis using ICOSA64D ?ow MRI under physiological conditions. First, the turbulence analysis was performedthrough in vitro experiments with a physiological pulsatile ?ow condition. Second, a total of12 normal subjects and one patient with severe aortic stenosis were analyzed using thesame sequence. The in-vitro study showed that total turbulent kinetic energy (TKE) wasless affected by the signal-to-noise ratio (SNR), however, maximum principal turbulenceshear stress (MPTSS) and total turbulence production (TP) had a noise-induced bias.Smaller degree of the bias was observed for TP compared to MPTSS. In-vivo studyshowed that the subject-variability on turbulence quanti?cation was relatively low for theconsistent scan protocol. The in vivo demonstration of the stenosis patient showed thatthe turbulence analysis could clearly distinguish the difference in all turbulence parametersas they were at least an order of magnitude larger than those from the normal subjects.