title: Effect of PRESS and STEAM sequences on magnetic resonance spectroscopic liver fat quantification.
abstract: OBJECTIVE
  To compare PRESS and STEAM MR spectroscopy for assessment of liver fat in human subjects.
  
  
  METHODS
  Single-voxel (20 x 20 x 20 mm) PRESS and STEAM spectra were obtained at 1.5T in 49 human subjects with known or suspected fatty liver disease. PRESS and STEAM sequences were obtained with fixed TR (1500 msec) and different TE (five PRESS spectra between TE 30-70 msec, five STEAM spectra between TE 20-60 msec). Spectra were quantified and T2 and T2-corrected peak area were calculated by different techniques. The values were compared for PRESS and STEAM.
  
  
  RESULTS
  Water T2 values from PRESS and STEAM were not significantly different (P = 0.33). Fat peak T2s were 25%-50% shorter on PRESS than on STEAM (P < 0.02 for all comparisons) and there was no correlation between T2s of individual peaks. PRESS systematically overestimated the relative fat peak areas (by 7%-263%) compared to STEAM (P < 0.005 for all comparisons). The peak area given by PRESS was more dependent on the T2-correction technique than STEAM.
  
  
  CONCLUSIONS
  Measured liver fat depends on the MRS sequence used. Compared to STEAM, PRESS underestimates T2 values of fat, overestimates fat fraction, and provides a less consistent fat fraction estimate, probably due to J coupling effects.
authors: Department of Radiology, University of California, San Diego, San Diego, California 92103-8226, USA.
authors: Gavin
authors: G
authors: Hamilton
authors: Michael S
authors: MS
authors: Middleton
authors: Mark
authors: M
authors: Bydder
authors: Takeshi
authors: T
authors: Yokoo
authors: Jeffrey B
authors: JB
authors: Schwimmer
authors: Yuko
authors: Y
authors: Kono
authors: Heather M
authors: HM
authors: Patton
authors: Joel E
authors: JE
authors: Lavine
authors: Claude B
authors: CB
authors: Sirlin
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry*; D000293:Adolescent; D000328:Adult; D000818:Animals; D005234:Fatty Liver / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000737:chemistry* / Q000473:pathology*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D011446:Prospective Studies