High-resolution echo-planar spectroscopic imaging of the human calf

• Published in: PloS one Vol. 9; no. 1; p. e87533
• Main Authors: Weis, Jan, Bruvold, Morten, Ortiz-Nieto, Francisco, Ahlström, Håkan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 30.01.2014; Public Library of Science (PLoS)
• Subjects: Adult; Biology; Bone marrow; Cattle; Contamination; Diabetes; Echo surveys; Echo-Planar Imaging - methods; Engineering; Feasibility studies; High resolution; Humans; Image resolution; Line spectra; Lipids; Lipids - chemistry; Localization; Magnetic fields; Magnetic permeability; Magnetic resonance; Magnetic Resonance Spectroscopy - methods; Magnetic susceptibility; Male; Medicine; Middle Aged; Muscle, Skeletal - metabolism; Muscles; Musculoskeletal system; Physics; Prostate; Scanners; Signal-To-Noise Ratio; Skeletal muscle; Soleus muscle; Spatial discrimination; Spatial resolution; Spectroscopy; Spectrum analysis; Splitting; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0087533

This study exploits the speed benefits of echo-planar spectroscopic imaging (EPSI) to acquire lipid spectra of skeletal muscle. The main purpose was to develop a high-resolution EPSI technique for clinical MR scanner, to visualise the bulk magnetic susceptibility (BMS) shifts of extra-myocellular lipid (EMCL) spectral lines, and to investigate the feasibility of this method for the assessment of intra-myocellular (IMCL) lipids. The study group consisted of six healthy volunteers. A two dimensional EPSI sequence with point-resolved spectroscopy (PRESS) spatial localization was implemented on a 3T clinical MR scanner. Measurements were performed by means of 64×64 spatial matrix and nominal voxel size 3×3×15 mm(3). The total net measurement time was 3 min 12 sec for non-water-suppressed (1 acquisition) and 12 min 48 sec for water-suppressed scans (4 acquisitions). Spectra of the human calf had a very good signal-to-noise ratio and linewidths sufficient to differentiate IMCL resonances from EMCL. The use of a large spatial matrix reduces inter-voxel signal contamination of the strong EMCL signals. Small voxels enabled visualisation of the methylene EMCL spectral line splitting and their BMS shifts up to 0.5 ppm relative to the correspondent IMCL line. The mean soleus muscle IMCL content of our six volunteers was 0.30±0.10 vol% (range 0.18-0.46) or 3.6±1.2 mmol/kg wet weight (range: 2.1-5.4). This study demonstrates that high-spatial resolution PRESS EPSI of the muscle lipids is feasible on standard clinical scanners.