Department of Mechanical and Biomedical Engineering, Kangwon National University, Chuncheon, South Korea.
Department of Electrical and Electronic Engineering, Yonsei Univeristy, Seoul, South Korea; Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
Magn Reson Imaging. 2020 Oct;72:49-60. doi: 10.1016/j.mri.2020.06.020. Epub 2020 Jun 30.
To perform comprehensive in vitro experiments using six-directional icosahedral flow encoding (ICOSA6) 4D flow magnetic resonance imaging (MRI) under various scan conditions to analyze the robustness of velocity and turbulence quantification.
In vitro flow phantoms with steady flow rates of 10 and 20 L/min were scanned using both conventional 4D flow MRI and ICOSA6. Experiments focused on comparisons between ICOSA6 and conventional four point (4P) methods, and the effects of contrast agents, velocity encoding range (Venc), and scan direction on velocity and turbulence quantification.
The results demonstrated that 1) ICOSA6 improves the velocity-to-noise ratio (VNR) of velocity estimation by 33% (on average) and results in similar turbulent kinetic energy (TKE) estimation as the 4P method. 2) Measurements with a contrast agent resulted in more than a 2.5 fold increase in average VNR. However, the improvement of total TKE quantification was not obvious. 3) TKE estimation was less affected by Venc and the scan direction, whereas turbulence production (TP) estimation was largely affected by these measurement conditions. The effects of Venc and scan direction accounted for less than 11.63% of TKE estimation, but up to 33.89% of TP estimation.
The ICOSA6 scheme is compatible with conventional 4D flow MRI for velocity and TKE measurement. Contrast agents are effective at increasing VNR, but not signal-to-noise ratio for TKE quantification. The effects of Venc and scan direction influence total TP more than total TKE.
在各种扫描条件下使用六向二十面体流编码（ICOSA6）4D 流磁共振成像（MRI）进行全面的体外实验，以分析速度和湍流量化的稳健性。
使用传统的 4D 流 MRI 和 ICOS A6 对流速分别为 10 和 20 L/min 的体外流动体模进行扫描。实验重点比较了 ICOS A6 和传统四点（4P）方法之间的差异，以及对比剂、流速编码范围（Venc）和扫描方向对速度和湍流量化的影响。
结果表明，1）ICOS A6 可将速度估计的速度噪声比（VNR）提高 33%（平均），并产生与 4P 方法相似的湍流动能（TKE）估计。2）使用对比剂的测量结果导致平均 VNR 增加了 2.5 倍以上。然而，总 TKE 量化的改善并不明显。3）TKE 估计受 Venc 和扫描方向的影响较小，而湍流产生（TP）估计受这些测量条件的影响较大。Venc 和扫描方向的影响仅占 TKE 估计的 11.63%以下，但占 TP 估计的 33.89%。
ICOSA6 方案与传统的 4D 流 MRI 兼容，可用于速度和 TKE 测量。对比剂可有效提高 VNR，但对 TKE 量化的信噪比影响不大。Venc 和扫描方向的影响对总 TP 的影响大于对总 TKE 的影响。
