Department of Radiology, Ajou University Hospital, Ajou University School of Medicine, Suwon.
Department of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine.
Invest Radiol. 2019 Aug;54(8):517-523. doi: 10.1097/RLI.0000000000000561.
The aim of this study was to evaluate the agreement and reproducibility of proton density fat fraction (PDFF) measurements using commercial magnetic resonance (MR) sequences across different imagers, vendors, and field strengths via a phantom experiment.
Eleven fat-water emulsion phantoms of varying fat proportions (ie, 0-50 weight%) were constructed. Phantom PDFFs were estimated using commercial chemical shift-based MR imaging sequences with Siemens 1.5 T and 3.0 T, Philips 3.0 T, and GE 1.5 T and 3.0 T imagers, and MR spectroscopic sequences (HISTO) with Siemens 1.5 T and 3.0 T imagers. Agreement among the estimated PDFF values between commercial sequences was evaluated using Bland-Altman analysis. Reproducibility of the PDFF measurements across commercial sequences was evaluated using the reproducibility coefficient. The test-retest repeatability of the PDFF measurements was evaluated using the repeatability coefficient.
The repeatability coefficient of the PDFF measurements was 0.31% to 1.58% for the absolute PDFF value for commercial sequences. Statistically significant biases in the estimated PDFF were noted in 19 of 21 pairwise comparisons of commercial sequences (range of mean biases, -4.48% to 8.15% for the absolute PDFF value). The reproducibility coefficient of PDFF measurements was 9.0% for the absolute PDFF value over all commercial sequences and 10.6% for the absolute PDFF value over all chemical shift-based MR imaging sequences.
The measurement of the PDFF is highly repeatable with commercial MR sequences but is not reproducible across different sequences, imager vendors, and field strengths. The use of the same sequence and imager is therefore recommended for the longitudinal follow-up of hepatic steatosis using commercial MR sequences for PDFF measurements.
本研究旨在通过体模实验评估使用商业磁共振（MR）序列在不同成像仪、供应商和磁场强度下测量质子密度脂肪分数（PDFF）的一致性和可重复性。
构建了 11 个脂肪-水乳液体模，脂肪比例（即 0-50 重量%）各不相同。使用商业基于化学位移的 MR 成像序列（西门子 1.5 T 和 3.0 T、飞利浦 3.0 T 和通用电气 1.5 T 和 3.0 T 成像仪）和 MR 波谱序列（HISTO）（西门子 1.5 T 和 3.0 T 成像仪）来估计体模的 PDFF。使用 Bland-Altman 分析评估商业序列之间估计 PDFF 值的一致性。使用重现系数评估 PDFF 测量值在商业序列之间的可重复性。使用重复性系数评估 PDFF 测量值的测试-再测试可重复性。
商业序列的绝对 PDFF 值的 PDFF 测量重复性系数为 0.31%至 1.58%。在 21 对商业序列的估计 PDFF 中，有 19 对存在统计学显著的偏差（绝对 PDFF 值的平均偏差范围为-4.48%至 8.15%）。所有商业序列的绝对 PDFF 值的 PDFF 测量重复性系数为 9.0%，所有基于化学位移的 MR 成像序列的绝对 PDFF 值的 PDFF 测量重复性系数为 10.6%。
使用商业 MR 序列测量 PDFF 具有高度的可重复性，但在不同序列、成像仪供应商和磁场强度之间无法重现。因此，建议在使用商业 MR 序列进行 PDFF 测量时，为了对肝脂肪变性进行纵向随访，使用相同的序列和成像仪。
