title: Quantification of muscle choline concentrations by proton MR spectroscopy at 3 T: technical feasibility.
abstract: OBJECTIVE
  The quantification of choline in musculoskeletal tissues has several potential uses, including characterizing malignancy, but has not been previously achievable. We present a method of measuring the absolute concentration of choline by proton MR spectroscopy (MRS) in skeletal muscle at 3 T.
  
  
  METHODS
  At 3 T, choline measurements were performed in phantoms and healthy volunteers using proton MRS (point-resolved spectroscopy sequence [PRESS]; TR/TE, 2,000/135). In vitro choline concentrations were measured in three phantom solutions (10, 5, 1.25 mmol). Choline T1 and T2 relaxation times were measured in the muscles of five healthy subjects. In vivo choline concentrations were measured using water as an internal reference and average T1 and T2 relaxation times in 20 muscle locations (quadriceps, hamstring, adductor) of seven healthy subjects (four men, three women). Descriptive statistics are reported.
  
  
  RESULTS
  In vitro, the average measured choline concentrations of the 10-, 5-, and 1.25-mmol solutions were 9.91, 5.03, and 1.22 mmol, respectively. In vivo, the average T1 and T2 relaxation times of choline were 1,372+/-57 (SD) and 134+/-11 milliseconds, respectively. The average choline concentrations in the quadriceps and hamstring muscles were 10.0+/-0.4 (SD) and 8.0+/-2.9 mmol/kg. Interindividual variation existed in the choline concentrations (quadriceps range, 6.7-13 mmol/kg), but there was little variation by patient sex.
  
  
  CONCLUSIONS
  In the musculoskeletal system, the measurement of choline concentration by proton MRS at 3 T is feasible using water as an internal reference. These data provide a quantitative basis for future investigations of metabolite concentrations in normal and diseased musculoskeletal tissues.
authors.affiliation: The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, 601 N Wolfe St., MRI 143C, Baltimore, MD 21287, USA. lfayad1@jhmi.edu
authors.forename: Laura M
authors.initials: LM
authors.lastname: Fayad
authors.forename: Nouha
authors.initials: N
authors.lastname: Salibi
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Machado
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jacobs
authors.forename: David A
authors.initials: DA
authors.lastname: Bluemke
authors.forename: Peter B
authors.initials: PB
authors.lastname: Barker
mesh_terms: D000328:Adult; D002794:Choline / Q000032:analysis*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000737:chemistry*; D019047:Phantoms, Imaging
chemical_list: D002794:Choline