Dillinger Hannes, Walheim Jonas, Kozerke Sebastian
Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
Magn Reson Med. 2020 Oct;84(4):1806-1816. doi: 10.1002/mrm.28236. Epub 2020 Mar 25.
To compare EPI and GRE readout in high-flow velocity regimes and evaluate their impact on measurement accuracy in silico and in vitro.
Phase-contrast sequences for EPI and GRE were simulated using CFD velocity data to assess displacement artifacts as well as effective spatial resolution. In silico findings were validated experimentally using a steady flow phantom.
For EPI factor 5 and simulated stenotic flow with peak velocity of 2.2 m , displacement artifacts resulted in misregistration of 7.3 mm at echo time and the effective resolution was locally reduced by factors 5 and 8 compared to GRE for flow along phase and frequency encoding directions, respectively. In vitro, a maximum velocity difference between EPI factor 5 and GRE of 0.97 m was found.
Four-dimensional flow MRI using EPI readout results not only in considerable velocity misregistration but also in spatially varying degradation of resolution. The proposed work indicates that EPI is inferior to standard GRE for 4D flow MRI.
比较高流速状态下的回波平面成像（EPI）和梯度回波（GRE）读出方式，并在计算机模拟和体外实验中评估它们对测量准确性的影响。
使用计算流体动力学（CFD）速度数据模拟EPI和GRE的相位对比序列，以评估位移伪影以及有效空间分辨率。使用稳定流模体对计算机模拟结果进行实验验证。
对于EPI因子为5且模拟峰值速度为2.2 m的狭窄血流，位移伪影在回波时间导致7.3 mm的配准错误，并且与GRE相比，沿相位编码和频率编码方向的血流有效分辨率分别局部降低了5倍和8倍。在体外实验中，发现EPI因子为5时与GRE的最大速度差异为0.97 m。
使用EPI读出的四维流动磁共振成像不仅会导致相当大的速度配准错误，还会导致分辨率在空间上的变化性下降。本研究表明，在四维流动磁共振成像中，EPI不如标准GRE。
