Ultralong TE In Vivo 1 H MR Spectroscopy of Omega-3 Fatty Acids in Subcutaneous Adipose Tissue at 7 T.

Background: Omega-3 (n-3) fatty acids (FA) play and important role in neural development and other metabolic diseases such as obesity and diabetes. The knowledge about the in vivo content and distribution of n-3 FA in human body tissues is not well established and the standard quantification of FA is invasive and costly.
Purpose: To detect omega-3 (n-3 CH ₃ ) and non-omega-3 (CH ₃ ) methyl group resonance lines with echo times up to 1200 msec, in oils, for the assessment of n-3 FA content, and the n-3 FA fraction in adipose tissue in vivo.
Study Type: Prospective technical development.
Population: Three oils with different n-3 FA content and 24 healthy subjects.
Field Strength/sequence: Single-voxel MR spectroscopy (SVS) with a point-resolved spectroscopy (PRESS) sequence with an echo time (TE) of 1000 msec at 7 T.
Assessment: Knowledge about the J-coupling evolution of both CH ₃ resonances was used for the optimal detection of the n-3 CH ₃ resonance line at a TE of 1000 msec. The accuracy of the method in oils and in vivo was validated from a biopsy sample with gas chromatography analysis.
Statistical Tests: SVS data were compared to gas chromatography with the Pearson correlation coefficient.
Results: T ₂ relaxation times in oils were assessed as follows: CH ₂ , 65 ± 22 msec; CH ₃ , 325 ± 7 msec; and n-3 CH ₃ , 628 ± 34 msec. The n-3 FA fractions from oil phantom experiments (n = 3) were in agreement with chromatography analysis and the comparison of in vivo obtained data with the results of chromatography analysis (n = 5) yielded a significant correlation (P = 0.029).
Data Conclusion: PRESS with ultralong-TE can detect and quantify the n-3 CH ₃ signal in vivo at 7 T.
Level of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:71-82.
(© 2018 The Authors. Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.)