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. 2021 Dec 7:9:774954.
doi: 10.3389/fbioe.2021.774954. eCollection 2021.

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

Hojin Ha  1 , Hyung Kyu Huh  2 , Kyung Jin Park  3   4 , Petter Dyverfeldt  5   6 , Tino Ebbers  5   6 , Dae-Hee Kim  7 , Dong Hyun Yang  4
Affiliations

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

Hojin Ha et al. Front Bioeng Biotechnol. .

Abstract

Imaging hemodynamics play an important role in the diagnosis of abnormal blood flow due to vascular and valvular diseases as well as in monitoring the recovery of normal blood flow after surgical or interventional treatment. Recently, characterization of turbulent blood flow using 4D flow magnetic resonance imaging (MRI) has been demonstrated by utilizing the changes in signal magnitude depending on intravoxel spin distribution. The imaging sequence was extended with a six-directional icosahedral (ICOSA6) flow-encoding to characterize all elements of the Reynolds stress tensor (RST) in turbulent blood flow. In the present study, we aimed to demonstrate the feasibility of full RST analysis using ICOSA6 4D flow MRI under physiological conditions. First, the turbulence analysis was performed through in vitro experiments with a physiological pulsatile flow condition. Second, a total of 12 normal subjects and one patient with severe aortic stenosis were analyzed using the same sequence. The in-vitro study showed that total turbulent kinetic energy (TKE) was less affected by the signal-to-noise ratio (SNR), however, maximum principal turbulence shear 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 study showed that the subject-variability on turbulence quantification was relatively low for the consistent scan protocol. The in vivo demonstration of the stenosis patient showed that the turbulence analysis could clearly distinguish the difference in all turbulence parameters as they were at least an order of magnitude larger than those from the normal subjects.

Keywords: hemodynamics; magnetic resonace imaging; turbulence measurement; turbulence production; turbulent kinetic energy.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
A schematic for in-vitro experiments.
FIGURE 2
FIGURE 2
Representative velocity mapping of ICOSA6 4D flow MRI for in-vivo.
FIGURE 3
FIGURE 3
Illustration of Reynolds stress measurement and turbulence parameter analysis.
FIGURE 4
FIGURE 4
Temporal variation of (A) Velocity, (B) turbulent kinetic energy (TKE), (C) maximum principal turbulent shear stress (MPTSS), (D) turbulence production (TP) through the stenosis at Venc of 200 cm/s.
FIGURE 5
FIGURE 5
Temporal variation of (A) Flow rate, (B) total TKE, (C) Average MPTSS, (D) total TP, (E) Peak velocity, (F) nwTKE, (G) nwMPTSS, and (H) nwTP at different Venc parameters. Note that the flow rate and peak velocity are only measured at Venc of 350 cm/s.
FIGURE 6
FIGURE 6
Effect of Venc on (A) TKE, (B) MPTSS, (C) TP at peak systole.
FIGURE 7
FIGURE 7
Comparison hemodynamics in normal subjects and patient with severe aortic stenosis. Note that representative normal subject (case #1) was used for color mapping. Values for the normal subject are median (1st quartile, 3rd quartile) of the data. Velocity, TKE, MPTSS and TP for all normal subjects are also shown in the Supplementary Figures S2–S5.
FIGURE 8
FIGURE 8
Boxplot of peak systolic (A) velocity, (B) total TKE, (C) average MPTSS, (D) total TP and diastolic (E) velocity, (F) total TKE, (G) average MPTSS and (H) total TP.
See this image and copyright information in PMC

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