title: In vivo sodium imaging of human patellar cartilage with a 3D cones sequence at 3 T and 7 T.
abstract: OBJECTIVE
  To compare signal-to-noise ratios (SNRs) and T*(2) maps at 3 T and 7 T using 3D cones from in vivo sodium images of the human knee.
  
  
  METHODS
  Sodium concentration has been shown to correlate with glycosaminoglycan content of cartilage and is a possible biomarker of osteoarthritis. Using a 3D cones trajectory, 17 subjects were scanned at 3 T and 12 at 7 T using custom-made sodium-only and dual-tuned sodium/proton surface coils, at a standard resolution (1.3 x 1.3 x 4.0 mm(3)) and a high resolution (1.0 x 1.0 x 2.0 mm(3)). We measured the SNR of the images and the T*(2) of cartilage at both 3 T and 7 T.
  
  
  RESULTS
  The average normalized SNR values of standard-resolution images were 27.1 and 11.3 at 7 T and 3 T. At high resolution, these average SNR values were 16.5 and 7.3. Image quality was sufficient to show spatial variations of sodium content. The average T*(2) of cartilage was measured as 13.2 +/- 1.5 msec at 7 T and 15.5 +/- 1.3 msec at 3 T.
  
  
  CONCLUSIONS
  We acquired sodium images of patellar cartilage at 3 T and 7 T in under 26 minutes using 3D cones with high resolution and acceptable SNR. The SNR improvement at 7 T over 3 T was within the expected range based on the increase in field strength. The measured T*(2) values were also consistent with previously published values.
authors.affiliation: Department of Radiology, Stanford University, Lucas Center for MRS/I, Stanford, California 94305, USA. ernestos@stanford.edu
authors.forename: Ernesto
authors.initials: E
authors.lastname: Staroswiecki
authors.forename: Neal K
authors.initials: NK
authors.lastname: Bangerter
authors.forename: Paul T
authors.initials: PT
authors.lastname: Gurney
authors.forename: Thomas
authors.initials: T
authors.lastname: Grafendorfer
authors.forename: Garry E
authors.initials: GE
authors.lastname: Gold
authors.forename: Brian A
authors.initials: BA
authors.lastname: Hargreaves
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D002356:Cartilage / Q000473:pathology; D005260:Female; D006025:Glycosaminoglycans / Q000737:chemistry; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010003:Osteoarthritis / Q000175:diagnosis / Q000473:pathology*; D010329:Patella / Q000473:pathology*; D015203:Reproducibility of Results; D012964:Sodium / Q000737:chemistry*; D013997:Time Factors
chemical_list: D015415:Biomarkers; D006025:Glycosaminoglycans; D012964:Sodium