Diffusion-Weighted Stimulated Echo Acquisition Mode (DW-STEAM) MR Spectroscopy to Measure Fat Unsaturation in Regions with Low Proton-Density Fat Fraction

作者：Ruschke Stefan^*; Kienberger Hermine; Baum Thomas; Kooijman Hendrik; Settles Marcus; Haase Axel; Rychlik Michael; Rummeny Ernst J; Karampinos Dimitrios C

来源：Magnetic Resonance in Medicine, 2016, 75(1): 32-41.

DOI：10.1002/mrm.25578

• fat unsaturation
• fat quantification
• triglycerides
• magnetic resonance spectroscopy (MRS)
• diffusion-weighted STEAM
• STEAM
• PRESS

Purpose: To propose and optimize diffusion-weighted stimulated echo acquisition mode (DW-STEAM) for measuring fat unsaturation in the presence of a strong water signal by suppressing the water signal based on a shorter T-2 and higher diffusivity of water relative to fat.
Methods: A parameter study for point-resolved spectroscopy (PRESS) and STEAM using oil phantoms was performed and correlated with gas chromatography (GC). Simulations of muscle tissue signal behavior using DW-STEAM and long-echo time (TE) PRESS and a parameter optimization for DW-STEAM were conducted. DW-STEAM and long-TE PRESS were applied in the gastrocnemius muscles of nine healthy subjects.
Results: STEAM with TE and mixing time (TM) up to 45 ms exhibited R-2 correlations above 0.98 with GC and little T-2-weighting and J-modulation for the quantified olefinic/methylene peak ratio. The optimal parameters for muscle tissue using DW-STEAM were b-value = 1800 s/mm(2), TE = 33 ms, TM = 30 ms, and repetition time-2300 ms. In vivo measured mean olefinic signal-to-noise ratios were 72 and 40, mean apparent olefinic water fractions were 0.19 and 0.11 for DW-STEAM and long-TE PRESS, respectively.
Conclusion: Optimized DW-STEAM MR spectroscopy is superior to long-TE PRESS for measuring fat unsaturation, if a strong water peak prevents the olefinic fat signal's quantification at shorter TEs and water's tissue specific ADC is substantially higher than fat.

• 出版日期2016-1
• 单位河北医科大学