Sofue Keitaro, Mileto Achille, Dale Brian M, Zhong Xiaodong, Bashir Mustafa R
Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA.
Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Japan.
J Magn Reson Imaging. 2015 Nov;42(5):1281-90. doi: 10.1002/jmri.24922. Epub 2015 Apr 27.
To assess the interexamination repeatability and spatial heterogeneity of liver iron and fat measurements using a magnetic resonance imaging (MRI)-based multistep adaptive fitting algorithm.
This prospective observational study was Institutional Review Board-approved and Health Insurance Portability and Accountability Act-compliant. Written informed consent was waived. In all, 150 subjects were imaged on 3T MRI systems. A whole-liver volume acquisition was performed twice using a six-echo 3D spoiled gradient echo sequence during two immediately adjacent examinations. Colocalized regions of interest (ROIs) in three different hepatic segments were placed for R2 * and proton density fat fraction (PDFF) measurements by two readers independently. Mean R2 * and PDFF values between readers and acquisitions were compared using the Wilcoxon signed-rank test, intraclass correlation coefficients (ICCs), linear regression, Bland-Altman analysis, and analysis of variance (ANOVA).
The mean R2 * and PDFF values across all ROIs and measurements were 51.2 ± 25.2 s(-1) and 6.9 ± 6.4%, respectively. Mean R2 * and PDFF values showed no significant differences between the two acquisitions (P = 0.05-0.87). Between the two acquisitions, R2 * and PDFF values demonstrated almost perfect agreement (ICCs = 0.979-0.994) and excellent correlation (R(2) = 0.958-0.989). Bland-Altman analysis also demonstrated excellent agreement. In the ANOVA, the individual patient and ROI location were significant effects for both R2 * and PDFF values (P < 0.05).
MRI-based R2 * and PDFF measurements are repeatable between examinations. Between-measurement changes in R2 * of more than 10.1 s(-1) and in PDFF of more than 1.7% are likely due to actual tissue changes. Liver iron and fat content are variable between hepatic segments.
使用基于磁共振成像（MRI）的多步自适应拟合算法评估肝脏铁和脂肪测量的检查间重复性及空间异质性。
本前瞻性观察性研究经机构审查委员会批准且符合《健康保险流通与责任法案》。无需书面知情同意书。总共150名受试者在3T MRI系统上进行成像。在两次紧邻的检查期间，使用六回波3D扰相梯度回波序列对全肝体积进行两次采集。由两名阅片者独立在三个不同肝段放置共定位的感兴趣区（ROI），用于测量R2 *和质子密度脂肪分数（PDFF）。使用Wilcoxon符号秩检验、组内相关系数（ICC）、线性回归、Bland-Altman分析和方差分析（ANOVA）比较阅片者之间以及采集之间的平均R2 *和PDFF值。
所有ROI和测量的平均R2 *和PDFF值分别为51.2±25.2 s(-1)和6.9±6.4%。两次采集之间的平均R2 *和PDFF值无显著差异（P = 0.05 - 0.87）。两次采集之间，R2 *和PDFF值显示出几乎完美的一致性（ICC = 0.979 - 0.994）和极好的相关性（R(2) = 0.958 - 0.989）。Bland-Altman分析也显示出极好的一致性。在方差分析中，个体患者和ROI位置对R2 *和PDFF值均有显著影响（P < 0.05）。
基于MRI的R2 *和PDFF测量在检查之间具有可重复性。R2 *测量值变化超过10.1 s(-1)以及PDFF测量值变化超过1.7%可能是由于实际组织变化所致。肝脏铁和脂肪含量在肝段之间存在差异。
