基于 20 回波梯度回波采集的 PDFF 和 T* 映射同时区分锁骨上和臀区脂肪组织。
Differentiating supraclavicular from gluteal adipose tissue based on simultaneous PDFF and T * mapping using a 20-echo gradient-echo acquisition.
机构信息
Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.
Institute for Nutritional Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.
出版信息
J Magn Reson Imaging. 2019 Aug;50(2):424-434. doi: 10.1002/jmri.26661. Epub 2019 Jan 25.
BACKGROUND
Adipose tissue (AT) can be classified into white and brown/beige subtypes. Chemical shift encoding-based water-fat MRI-techniques allowing simultaneous mapping of proton density fat fraction (PDFF) and T * result in a lower PDFF and a shorter T * in brown compared with white AT. However, AT T * values vary widely in the literature and are primarily based on 6-echo data. Increasing the number of echoes in a multiecho gradient-echo acquisition is expected to increase the precision of AT T * mapping.
PURPOSE
- To mitigate issues of current T *-measurement techniques through experimental design, and 2) to investigate gluteal and supraclavicular AT T * and PDFF and their relationship using a 20-echo gradient-echo acquisition.
STUDY TYPE
Prospective.
SUBJECTS
Twenty-one healthy subjects.
FIELD STRENGTH/SEQUENCE ASSESSMENT: First, a ground truth signal evolution was simulated from a single-T * water-fat model. Second, a time-interleaved 20-echo gradient-echo sequence with monopolar gradients of neck and abdomen/pelvis at 3 T was performed in vivo to determine supraclavicular and gluteal PDFF and T *. Complex-based water-fat separation was performed for the first 6 echoes and the full 20 echoes. AT depots were segmented.
STATISTICAL TESTS
Mann-Whitney test, Wilcoxon signed-rank test and simple linear regression analysis.
RESULTS
Both PDFF and T * differed significantly between supraclavicular and gluteal AT with 6 and 20 echoes (PDFF: P < 0.0001 each, T *: P = 0.03 / P < 0.0001 for 6/20 echoes). 6-echo T * demonstrated higher standard deviations and broader ranges than 20-echo T *. Regression analyses revealed a strong relationship between PDFF and T * values per AT compartment (R = 0.63 supraclavicular, R = 0.86 gluteal, P < 0.0001 each).
DATA CONCLUSION
The present findings suggest that an increase in the number of sampled echoes beyond 6 does not affect AT PDFF quantification, whereas AT T * is considerably affected. Thus, a 20-echo gradient-echo acquisition enables a multiparametric analysis of both AT PDFF and T * and may therefore improve MR-based differentiation between white and brown fat.
LEVEL OF EVIDENCE
2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:424-434.
背景
脂肪组织（AT）可分为白色和棕色/米色亚型。基于化学位移编码的水脂 MRI 技术可同时对质子密度脂肪分数（PDFF）和 T进行映射，结果显示棕色 AT 的 PDFF 较低，T较短。然而，AT T* 值在文献中差异很大，主要基于 6 回波数据。在多回波梯度回波采集过程中增加回波数量有望提高 AT T* 映射的精度。
目的
1）通过实验设计减轻当前 T测量技术的问题，2）使用 20 回波梯度回波采集来研究臀上部和锁骨上 AT 的 T和 PDFF 及其关系。
研究类型
前瞻性。
受试者
21 名健康受试者。
磁场强度/序列评估：首先，从单 T水脂模型模拟真实信号演变。其次，在 3T 时进行了具有颈部和腹部/骨盆单极梯度的时间交错 20 回波梯度回波序列，以确定锁骨上和臀上部的 PDFF 和 T。对前 6 个回波和完整的 20 个回波进行基于复数的水脂分离。AT 隔室进行了分割。
统计学检验
Mann-Whitney 检验、Wilcoxon 符号秩检验和简单线性回归分析。
结果
锁骨上和臀上部 AT 的 PDFF 和 T* 均有显著差异（PDFF：均 P<0.0001，T*：6 回波 P=0.03/20 回波 P<0.0001）。6 回波 T* 的标准偏差和范围均高于 20 回波 T*。回归分析显示，每个 AT 隔室的 PDFF 和 T* 值之间存在很强的相关性（锁骨上 R=0.63，臀上部 R=0.86，均 P<0.0001）。
数据结论
本研究结果表明，增加采样回波数量超过 6 不会影响 AT PDFF 定量，而 AT T* 则受到较大影响。因此，20 回波梯度回波采集可对 AT PDFF 和 T* 进行多参数分析，从而提高基于 MRI 的白色和棕色脂肪的区分。
证据水平
2 技术功效：2 级。J. Magn. Reson. Imaging 2019；50：424-434.
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