title: Multi-voxel MR spectroscopic imaging of the brain: utility in clinical setting-initial results.
abstract: OBJECTIVE
  Compared to single voxel methods, MR spectroscopic imaging (MRSI) of the brain provides metabolic information with improved anatomical coverage and spectral resolution, but may be difficult to perform in the clinical setting. We evaluate the factors influencing spectral quality in MRSI using a semi-automated method, focussing on lipid contamination, and phase correction errors related to magnetic field inhomogeneity.
  
  
  METHODS
  We retrospectively analysed MRSI studies planned by radiologists and radiographers. Two-dimensional MRSI studies using point-resolved spectroscopy (PRESS) localisation, at long echo time (135 or 144 ms) were acquired on a 1.5 T scanner. Studies that contained lipid contamination and abnormally inverted spectra were reviewed and the latter correlated with anatomic location at the base of skull, and with the area of the region of interest (ROI) studied.
  
  
  RESULTS
  Of 128 consecutive MRSI studies, six showed abnormal inverted spectra, of which four were acquired at the base of skull. Multivariate logistic regression analysis showed that study location at the base of skull, but not larger ROI, was a significant predictor for the risk of being affected by inverted spectra (RR for base of skull: 11.76, 95% CI: 1.86-74.18, P=0.009. RR for area of ROI: 3.68, 95% CI: 0.57-23.67, P=0.170). Seven studies showed lipid contamination; all were in close proximity to the overlying scalp.
  
  
  CONCLUSIONS
  Using a semi-automated acquisition and post-processing method, MRSI can be successfully applied in the clinical setting. However, care should be taken to avoid regions of high magnetic field inhomogeneity at the base of skull, and lipid contamination in voxels prescribed near the scalp.
authors.affiliation: Department of Neuroradiology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore. parurad@hotmail.com
authors.forename: Hemant
authors.initials: H
authors.lastname: Parmar
authors.forename: Tchoyoson C C
authors.initials: TC
authors.lastname: Lim
authors.forename: Hong
authors.initials: H
authors.lastname: Yin
authors.forename: Violet
authors.initials: V
authors.lastname: Chua
authors.forename: Lay-Wai
authors.initials: LW
authors.lastname: Khin
authors.forename: Tom
authors.initials: T
authors.lastname: Raidy
authors.forename: Francis
authors.initials: F
authors.lastname: Hui
mesh_terms: D001923:Brain Chemistry; D001927:Brain Diseases / Q000378:metabolism*; D016009:Chi-Square Distribution; D006801:Humans; D050356:Lipid Metabolism; D016015:Logistic Models; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012189:Retrospective Studies