MR3T Bydder Laboratory, Liver Imaging Group, Department of Radiology, University of California, San Diego, 408 Dickinson Street, MC 8226, San Diego, CA, 92103-8226, USA.
Department of Diagnostic and Interventional Radiology, Rochester General Hospital, Rochester, NY, USA.
Abdom Radiol (NY). 2017 Apr;42(4):1189-1198. doi: 10.1007/s00261-016-0992-4.
The aim of the study was to determine in patients undergoing gadoxetate disodium (Gx)-enhanced MR exams whether proton density fat fraction (PDFF) estimation accuracy of magnitude-based multi-gradient-echo MRI (MRI-M) could be improved by using high flip angle (FA) on post-contrast images.
Thirty-one adults with known or suspected hepatic steatosis undergoing 3T clinical Gx-enhanced liver MRI were enrolled prospectively. MR spectroscopy (MRS), the reference standard, was performed before Gx to measure MRS-PDFF. Low (10°)- and high (50°)-flip angle (FA) MRI-M sequences were acquired before and during the hepatobiliary phase after Gx administration; MRI-PDFF was estimated in the MRS-PDFF voxel location. Linear regression parameters (slope, intercept, average bias, R ) were calculated for MRS-PDFF as a function of MRI-PDFF for each MRI-M sequence (pre-Gx low-FA, pre-Gx high-FA, post-Gx low-FA, post-Gx high-FA) for all patients and for patients with MRS-PDFF <10%. Regression parameters were compared (Bonferroni-adjusted bootstrap-based tests).
Three of the four MRI-M sequences (pre-Gx low-FA, post-Gx low-FA, post-Gx high-FA) provided relatively unbiased PDFF estimates overall and in the low-PDFF range, with regression slopes close to 1 and intercepts and biases close to zero. Pre-Gx high-FA MRI overestimated PDFF in proportion to MRS-PDFF, with slopes of 0.72 (overall) and 0.63 (low-PDFF range). Based on regression bias closest to 0, the post-Gx high-FA sequence was the most accurate overall and in the low-PDFF range. This sequence provided statistically significant improvements in at least two regression parameters compared to every other sequence.
In patients undergoing Gx-enhanced MR exams, PDFF estimation accuracy of MRI-M can be improved by using high-FA on post-contrast images.
本研究旨在探讨在接受钆塞酸二钠（Gd）增强磁共振（MR）检查的患者中，基于多梯度回波（MRI-M）的质子密度脂肪分数（PDFF）估计准确性是否可以通过在对比后图像中使用高翻转角（FA）来提高。
前瞻性纳入 31 例已知或疑似存在肝脂肪变性的成人患者，行 3T 临床 Gd 增强肝脏 MR 检查。在 Gd 给药前进行磁共振波谱（MRS）检查，作为参考标准，以测量 MRS-PDFF。在 Gd 给药后肝胆期前和期间采集低（10°）和高（50°）FA 的 MRI-M 序列；在 MRS-PDFF 所在的位置进行 MRI-PDFF 估计。对于所有患者和 MRS-PDFF＜10%的患者，计算每个 MRI-M 序列（Gd 给药前低 FA、Gd 给药前高 FA、Gd 给药后低 FA、Gd 给药后高 FA）的 MRS-PDFF 作为 MRI-PDFF 的线性回归参数（斜率、截距、平均偏差、R）。比较回归参数（经 Bonferroni 调整的 bootstrap 检验）。
四个 MRI-M 序列中的三个（Gd 给药前低 FA、Gd 给药后低 FA、Gd 给药后高 FA）总体上以及在低 PDFF 范围内提供了相对无偏的 PDFF 估计，回归斜率接近 1，截距和偏差接近 0。Gd 给药前高 FA MRI 与 MRS-PDFF 呈比例性高估，斜率为 0.72（总体）和 0.63（低 PDFF 范围）。基于最接近 0 的回归偏差，Gd 给药后高 FA 序列总体上和在低 PDFF 范围内最为准确。与其他序列相比，该序列至少在两个回归参数上提供了统计学上的显著改善。
在接受 Gd 增强 MR 检查的患者中，通过在对比后图像中使用高 FA，可以提高 MRI-M 的 PDFF 估计准确性。
