Liver Imaging Research Program, Department of Radiology, University of Wisconsin, 600 Highland Ave, E3/311 CSC, Madison, WI 53792-3252, USA.
Radiology. 2011 Mar;258(3):767-75. doi: 10.1148/radiol.10100708. Epub 2011 Jan 19.
To prospectively compare an investigational version of a complex-based chemical shift-based fat fraction magnetic resonance (MR) imaging method with MR spectroscopy for the quantification of hepatic steatosis.
This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained before all studies. Fifty-five patients (31 women, 24 men; age range, 24-71 years) were prospectively imaged at 1.5 T with quantitative MR imaging and single-voxel MR spectroscopy, each within a single breath hold. The effects of T2 correction, spectral modeling of fat, and magnitude fitting for eddy current correction on fat quantification with MR imaging were investigated by reconstructing fat fraction images from the same source data with different combinations of error correction. Single-voxel T2-corrected MR spectroscopy was used to measure fat fraction and served as the reference standard. All MR spectroscopy data were postprocessed at a separate institution by an MR physicist who was blinded to MR imaging results. Fat fractions measured with MR imaging and MR spectroscopy were compared statistically to determine the correlation (r(2)), and the slope and intercept as measures of agreement between MR imaging and MR spectroscopy fat fraction measurements, to determine whether MR imaging can help quantify fat, and examine the importance of T2 correction, spectral modeling of fat, and eddy current correction. Two-sided t tests (significance level, P = .05) were used to determine whether estimated slopes and intercepts were significantly different from 1.0 and 0.0, respectively. Sensitivity and specificity for the classification of clinically significant steatosis were evaluated.
Overall, there was excellent correlation between MR imaging and MR spectroscopy for all reconstruction combinations. However, agreement was only achieved when T2 correction, spectral modeling of fat, and magnitude fitting for eddy current correction were used (r(2) = 0.99; slope ± standard deviation = 1.00 ± 0.01, P = .77; intercept ± standard deviation = 0.2% ± 0.1, P = .19).
T1-independent chemical shift-based water-fat separation MR imaging methods can accurately quantify fat over the entire liver, by using MR spectroscopy as the reference standard, when T2 correction, spectral modeling of fat, and eddy current correction methods are used.
前瞻性比较基于化学位移的复杂基础脂肪分数磁共振（MR）成像方法的研究版本与 MR 光谱用于定量肝脂肪变性。
本研究经机构审查委员会批准并符合 HIPAA 规定。所有研究均获得书面知情同意。55 例患者（31 例女性，24 例男性；年龄 24-71 岁）在 1.5T 上进行前瞻性成像，包括定量 MR 成像和单体素 MR 光谱，每个均在单次屏气中完成。通过不同组合的误差校正，从相同源数据重建脂肪分数图像，研究 T2 校正、脂肪光谱建模和涡流校正的幅度拟合对 MR 成像中脂肪定量的影响。单体素 T2 校正的 MR 光谱用于测量脂肪分数，并作为参考标准。所有 MR 光谱数据均由一名对 MR 成像结果不知情的磁共振物理学家在另一个机构进行后处理。统计比较 MR 成像和 MR 光谱测量的脂肪分数，以确定相关性（r(2)），以及斜率和截距作为评估 MR 成像和 MR 光谱脂肪分数测量之间一致性的指标，以确定 MR 成像是否有助于定量脂肪，并研究 T2 校正、脂肪光谱建模和涡流校正的重要性。使用双侧 t 检验（显著性水平，P =.05）确定估计斜率和截距是否与 1.0 和 0.0 显著不同。还评估了对临床显著脂肪变性的分类的敏感性和特异性。
总体而言，对于所有重建组合，MR 成像和 MR 光谱之间均具有极好的相关性。然而，仅在使用 T2 校正、脂肪光谱建模和涡流校正幅度拟合时才达成一致（r(2) = 0.99；斜率±标准偏差 = 1.00 ± 0.01，P =.77；截距±标准偏差 = 0.2% ± 0.1，P =.19）。
当使用 MR 光谱作为参考标准时，通过 T2 校正、脂肪光谱建模和涡流校正方法，基于化学位移的 T1 独立水脂分离磁共振成像方法可以准确量化整个肝脏的脂肪。
