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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 CH3 ) and non-omega-3 (CH3 ) 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 CH3 resonances was used for the optimal detection of the n-3 CH3 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: T2 relaxation times in oils were assessed as follows: CH2 , 65 ± 22 msec; CH3 , 325 ± 7 msec; and n-3 CH3 , 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 CH3 signal in vivo at 7 T.Level Of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:71-82. [ABSTRACT FROM AUTHOR]

In this study, we present a method for the detection of n-3 fatty acid (n-3 FA) signals using MRS in adipose tissue in vivo. This method (called oMEGA-PRESS) is based on the selective detection of the CH3 signal of n-3 FA using the MEGA-PRESS (MEshcher-GArwood Point-RESolved Spectroscopy) J-difference editing technique. We optimized the envelope shape and frequency of spectral editing pulses to minimize the spurious co-editing and incomplete subtraction of the CH3 signal of other FAs, which normally obscure the n-3 FA CH3 signal in MR spectra acquired using standard PRESS techniques. The post-processing of the individual data scans with the phase and frequency correction before data subtraction and averaging was implemented to further improve the quality of in vivo spectra. The technique was optimized in vitro on lipid phantoms using various concentrations of n-3 FA and examined in vivo at 3 T on 15 healthy volunteers. The proportion of n-3 FA estimated by the oMEGA-PRESS method in phantoms showed a highly significant linear correlation with the n-3 FA content determined by gas chromatography. The signal attributed to n-3 FA was observed in all subjects. Comparisons with the standard PRESS technique revealed an enhanced identification of the n-3 FA signal using oMEGA-PRESS. The presented method may be useful for the non-invasive quantification of n-3 FA in adipose tissue, and could aid in obtaining a better understanding of various aspects of n-3 FA metabolism. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose To introduce a method of independent determination of CH2 and CH3 components of intramyocellular lipids (IMCLs) by using long TE for spectra measurement and LCModel for spectra evaluation, to test this technique in controls and insulin-resistant subjects, and to compare results at 1.5 and 3 T. Materials and Methods Eight healthy volunteers and 11 patients with type 2 diabetes mellitus underwent measurement using a 1.5-T MR scanner; six healthy volunteers were measured using a 3-T MR scanner. Spectra from the tibialis anterior muscle were acquired by using a point resolved spectroscopy (PRESS) sequence with the following parameters: TR/TE/ACQ = 2000 msec/270 msec/256. Spectra were processed by LCModel 6.1 software with two types of adopted basis-set. Results Spectra with good separation of both CH2 and CH3 components of IMCL and extramyocellular lipids (EMCLs) were obtained and the LCModel routine was successfully applied. The reproducibility comparison ( N= 7 at 1.5 T vs. N = 5 at 3 T) showed that better results can be obtained at higher B0 values. The comparison of the healthy and insulin-resistant subjects proved that both IMCL_CH2/Cr and IMCL_CH3/Cr ratios significantly differ. Conclusion Long TE spectroscopy of the human muscle with IMCL quantification using the LCModel technique can detect changes in IMCL levels as well as help in the study of fatty acyl chain composition. Using a higher field strength increased the intra-individual reproducibility by approximately 150% J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]