Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.
Magn Reson Med. 2017 Aug;78(2):730-738. doi: 10.1002/mrm.26461. Epub 2016 Sep 21.
The purpose of this work was to characterize the effects of concomitant gradients (CGs) on chemical shift encoded (CSE)-based estimation of B field map, proton density fat fraction (PDFF), and R2*.
A theoretical framework was used to determine the effects of CG-induced phase errors on CSE-MRI data.
Simulations, phantom experiments, and in vivo experiments were conducted at 3 Tesla to assess the effects of CGs on quantitative CSE-MRI techniques. Correction of phase errors attributable to CGs was also investigated to determine whether these effects could be removed.
Phase errors attributed to CGs introduce errors in the estimation of B field map, PDFF, and R2*. Phantom and in vivo experiments demonstrated that CGs can introduce estimation errors greater than 30 Hz in the B field map, 10% in PDFF, and 16 s in R2*, 16 cm off isocenter. However, CG phase correction before parameter estimation was able to reduce estimation errors to less than 10 Hz in the B field map, 1% in PDFF, and 2 s in R2*.
CG effects can impact CSE-MRI, leading to inaccurate estimation of B field map, PDFF, and R2*. However, correction for phase errors caused by CGs improve the accuracy of quantitative parameters estimated from CSE-MRI acquisitions. Magn Reson Med 78:730-738, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
本研究旨在探讨伴随梯度（CGs）对基于化学位移编码（CSE）的 B 场图、质子密度脂肪分数（PDFF）和 R2*估计的影响。
采用理论框架来确定 CG 引起的相位误差对 CSE-MRI 数据的影响。
在 3T 进行模拟、体模实验和体内实验，以评估 CG 对定量 CSE-MRI 技术的影响。还研究了校正 CG 引起的相位误差，以确定是否可以消除这些影响。
CG 引起的相位误差会导致 B 场图、PDFF 和 R2的估计出现误差。体模和体内实验表明，CG 可导致 B 场图的估计误差超过 30Hz、PDFF 为 10%、R2为 16s，CG 距等中心 16cm。然而，在参数估计之前进行 CG 相位校正可以将 B 场图的估计误差降低至 10Hz 以下、PDFF 为 1%、R2*为 2s。
CG 效应会影响 CSE-MRI，导致 B 场图、PDFF 和 R2*的估计不准确。然而，校正 CG 引起的相位误差可以提高从 CSE-MRI 采集估计的定量参数的准确性。磁共振医学 78:730-738,2017。©2016 国际磁共振学会。
