Abstract:
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Purpose: Determination of intramyocellular lipids (IMCL) by proton magnetic resonance spectroscopy (1H MRS) has become of increasing interest, as IMCL are involved in the pathogenesis of skeletal muscle insulin resistance and type 2 diabetes mellitus. At a magnetic field strength of 1.5 T differentiation between IMCL and EMCL is aggravated by overlapping signals. The aim of the study was to examine whether the higher magnetic field strength of 3 T might lead to an improved separation of the mentioned lipid compartments. Characteristics of further metabolites as creatine and TMA/Tau and signal-to-noise ratios were assessed as well.
Methods and Materials: Comparative measurements have been performed at 1.5 T (Magnetom Sonata, Siemens, Erlangen, Germany) and 3 T (Magnetom Trio, Siemens/Bruker, Germany) in the tibialis anterior muscle (TA) and the soleus muscle (SOL). For volume selection a standard single voxel STEAM technique with TE=10ms, TR=2s, 40 acquisitions was applied. Voxel size was chosen to 11x11x20mm3 on both units. At 3 T, additional spectra were recorded with smaller voxel sizes of 7x7x15mm3 and 5x5x10mm3. Spectra were systematically compared for typical signal characteristics.
Results: Distinct differences in the spectral patterns were observed for the two magnetic field strengths: In TA, the well-known TMA/Tau resonances are split in four signal components at 3 T, but this effect does not occur in SOL. Both methylene signals of Cr show minor spectral separation at 3 T compared to 1.5 T in TA. Line widths (in ppm) are generally smaller at 3 T compared to 1.5 T, except the EMCL signals which remain with a broad and asymmetrical line shape. Spectra from smaller voxels with careful positioning are shown to provide a clearly decreasing EMCL signal contamination, resulting in improved visibility of IMCL in SOL at 3 T.
Conclusion: Spectral patterns of human skeletal muscles at 3 T are influenced by different effects. Natural line widths (in ppm) are smaller compared to 1.5 T, resulting in an improved spectral resolution. On the other hand, susceptibility effects get more pronounced, leading to remaining broad lines for EMCL. In conclusion, the higher field strength provides higher sensitivity and/or smaller voxel sizes, and will thus lead to a more precise study of skeletal muscle lipid metabolism as separate depiction of IMCL improves quantification of this important lipid compartment. Supported by a grant from the Federal Ministry of Education and Research (Foe. 01KS9602) and the Interdisciplinary Center of Clinical Research Tuebingen (IZKF)
Questions about this event email: juergen.machann@med.uni-tuebingen.de
Machann MD, J,
Magnetic Resonance Spectroscopy at High Field Strength: Improved Examination of Skeletal Muscle Lipid Metabolism in the Field of Diabetes Research. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3100509.html
