title: Implementation and validation of localized constant-time correlated spectroscopy (LCT-COSY) on a clinical 3T MRI scanner for investigation of muscle metabolism.
abstract: OBJECTIVE
  To implement and evaluate a novel single-volume two-dimensional localized constant-time-based correlated spectroscopy (2D LCT-COSY) sequence on a clinical 3T MR scanner. This sequence exhibits homonuclear decoupling along the F1 dimension, leading to improved spectral resolution compared to that of non-constant-time localized correlated spectroscopy (L-COSY).
  
  
  METHODS
  A GE 3T MR scanner equipped with a quadrature transmit and receive extremity coil was used in this study. The 2D LCT-COSY sequence was programmed using General Electric's EPIC compiler. Simulations for a two-spin 1/2 system were performed using GAMMA libraries to evaluate the theoretical performance of the sequences, and were also compared with corresponding phantom experiments using trans-cinnamic acid. Finally, spectra were acquired from the soleus muscle of healthy volunteers in order to evaluate performance in vivo.
  
  
  RESULTS
  Simulations and experimental results confirmed the improved spectral resolution of LCT-COSY over L-COSY, as well as its homonuclear decoupling performance. The behavior of resonance amplitudes as a function of evolution time in the experiment also was appropriately reflected by the simulation. Corresponding results were obtained for the in vivo muscle spectra, in which separation of overlapping olefinic and allylic methylene protons from the intra- and extramyocellular lipids (IMCL and EMCL, respectively) was achieved.
  
  
  CONCLUSIONS
  Simulations and experimental results in vitro and in vivo demonstrate the strengths of LCT-COSY. This technique can be implemented on systems of any field strength, and has the potential to separate overlapping metabolites in tissue when employed on high-field clinical MRI scanners equipped for proton spectroscopy.
authors.affiliation: Center for Advanced Imaging and Radiology, West Virginia University, Morgantown, West Virginia 265-6, USA. svelan@hsc.wvu.edu
authors.forename: S Sendhil
authors.initials: SS
authors.lastname: Velan
authors.forename: Senthil
authors.initials: S
authors.lastname: Ramamurthy
authors.forename: Srilatha
authors.initials: S
authors.lastname: Ainala
authors.forename: Christopher
authors.initials: C
authors.lastname: Durst
authors.forename: Susan K
authors.initials: SK
authors.lastname: Lemieux
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Raylman
authors.forename: Richard G
authors.initials: RG
authors.lastname: Spencer
authors.forename: M Albert
authors.initials: MA
authors.lastname: Thomas
mesh_terms: D000328:Adult; D002934:Cinnamates / Q000494:pharmacology; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement; D008055:Lipids / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D018482:Muscle, Skeletal / Q000473:pathology; D009132:Muscles / Q000378:metabolism / Q000473:pathology*; D019047:Phantoms, Imaging; D011522:Protons; D015203:Reproducibility of Results; D015398:Signal Transduction; D013053:Spectrophotometry / Q000379:methods*
chemical_list: D002934:Cinnamates; D008055:Lipids; D011522:Protons; C029010:cinnamic acid