Purpose: To demonstrate the feasibility of estimating the relative intra- and extramyocellular lipid (IMCL and EMCL) pool magnitudes and calculating the degree of lipid unsaturation within soleus muscle using single-voxel localized one- and two-dimensional (1D and 2D) MR spectroscopy (MRS).
Materials and methods: Localized 1D point resolved spectroscopy (PRESS) and 2D correlation spectroscopy (L-COSY) were performed in identical locations in the soleus muscle of 10 healthy subjects. A GE 3-T MRI/MRS scanner and a quadrature extremity transmit/receive coil was used.
Results: The 1D and 2D MR spectra were used to compute IMCL/creatine (Cr) and EMCL/Cr ratios. In addition to cross peaks between the methyl and methylene protons in the high-field region, the 2D spectra showed cross peaks due to J-coupling between allylic, diallylic methylene pro- tons, and olefinic protons. The cross-peak volume ratios also provided a measure of double bonds, suggesting that this ratio can be used to assess unsaturation within IMCL and EMCL lipid pools.
Conclusion: We have demonstrated the feasibility of detecting 2D cross peaks between different groups of IMCL and EMCL, including the unsaturated protons within these two lipids pools. This protocol may be easily extended to study the lipids present in other tissues.