title: Reproducibility of total choline/water ratios in mouse U87MG xenograft tumors by 1H-MRS.
abstract: OBJECTIVE
  To evaluate the reproducibility of the measurement of the total choline-to-water ratio, and the effect of repositioning the subject between scans, using (1) H-magnetic resonance spectroscopy in a mouse U87MG xenograft model.
  
  
  METHODS
  In vivo single-voxel MR spectra at 7T from xenograft tumors were obtained using both a water-suppressed and a nonwater-suppressed point-resolved spectroscopy (PRESS) sequence. Reproducibility of the total choline/water ratio was evaluated under the conditions of immediate rescan with no change in position of the animal or voxel, immediate reposition, and reposition after 1 or 7 days.
  
  
  RESULTS
  Total choline-to-water ratios in U87MG tumor xenografts averaged ≈0.018 across all of the groups. The average percent difference between the two scans in each condition was always less than ≈3.0%, and the coefficient of variation was always less than ≈12%. Bias was unrelated to the testing condition and relatively negligible in magnitude (<3%). Due to heteroscedasticity in the ratios, the limits of agreement were calculated after log transformation of the data and ranged from ≈12% when animals were maintained in the same position and immediately rescanned to ≈52% when the two scans were 7 days apart.
  
  
  CONCLUSIONS
  The total choline-to-water ratio provides a reproducible measure of choline-containing metabolites in subcutaneous U87MG xenograft tumors in mice.
authors.affiliation: Department of Molecular and Anatomical Imaging, Covance Laboratories, Inc., Greenfield, IN 46140, USA. mingming.zhu@covance.com
authors.forename: Mingming
authors.initials: M
authors.lastname: Zhu
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Fischl
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Trowbridge
authors.forename: Harlan E
authors.initials: HE
authors.lastname: Shannon
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis*; D001834:Body Water / Q000737:chemistry*; D045744:Cell Line, Tumor; D002794:Choline / Q000032:analysis*; D005909:Glioblastoma / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014867:Water / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; D011522:Protons; D014867:Water; D002794:Choline