Differentiating supraclavicular from gluteal adipose tissue based on simultaneous PDFF and T2* mapping using a 20‐echo gradient‐echo acquisition. Issue 2 (25th January 2019)

• Record Type: Journal Article
• Authors: Franz, Daniela; Diefenbach, Maximilian N.; Treibel, Franziska; Weidlich, Dominik; Syväri, Jan; Ruschke, Stefan; Wu, Mingming; Holzapfel, Christina; Drabsch, Theresa; Baum, Thomas; Eggers, Holger; Rummeny, Ernst J.; Hauner, Hans; Karampinos, Dimitrios C.
• Is Part Of: Journal of magnetic resonance imaging. Volume 50:Issue 2(2019)
• Page Start: 424
• Page End: 434
• Publication Date: 2019-01-25
• Subjects: magnetic resonance imaging -- MRI -- T2* mapping -- PDFF mapping -- brown fat -- white fat -- fat spectrum; Magnetic resonance imaging -- Periodicals; 616
• DOI: 10.1002/jmri.26661
• Languages: English
• ISSNs: 1053-1807

Abstract

Abstract : 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 T2 * result in a lower PDFF and a shorter T2 * in brown compared with white AT. However, AT T2 * 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 T2 * mapping. Purpose: 1) To mitigate issues of current T2 *‐measurement techniques through experimental design, and 2) to investigate gluteal and supraclavicular AT T2 * 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‐T2 * 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 T2 *. 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 T2 * differed significantly between supraclavicular and gluteal AT with 6 and 20 echoes (PDFF: P < 0.0001 each, T2 *: P = 0.03 / P < 0.0001 for 6/20 echoes). 6‐echo T2 * demonstrated higher standard deviations and broader ranges than 20‐echo T2 *. Regression analyses revealed a strong relationship between PDFF and T2 * values per AT compartment (R 2 = 0.63 supraclavicular, R 2 = 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 T2 * is considerably affected. Thus, a 20‐echo gradient‐echo acquisition enables a multiparametric analysis of both AT PDFF and T2 * 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.