title: Cartilage quality assessment by using glycosaminoglycan chemical exchange saturation transfer and (23)Na MR imaging at 7 T.
abstract: OBJECTIVE
  To compare a glycosaminoglycan chemical exchange saturation transfer (gagCEST) imaging method, which enables sampling of the water signal as a function of the presaturation offset (z-spectrum) at 13 points in clinically feasible imaging times, with sodium 23 ((23)Na) magnetic resonance (MR) imaging in patients after cartilage repair surgery (matrix-associated autologous chondrocyte transplantation and microfracture therapy).
  
  
  METHODS
  One female patient (67.3 years), and 11 male patients (median age, 28.8 years; interquartile range [IQR], 24.6-32.3 years) were examined with a 7-T whole-body system, with approval of the local ethics committee after written informed consent was obtained. A modified three-dimensional gradient-echo sequence and a 28-channel knee coil were used for gagCEST imaging. (23)Na imaging was performed with a circularly polarized knee coil by using a modified gradient-echo sequence. Statistical analysis of differences and Spearman correlation were applied.
  
  
  RESULTS
  The median of asymmetries in gagCEST z-spectra summed over all offsets from 0 to 1.3 ppm was 7.99% (IQR, 6.33%-8.79%) in native cartilage and 5.13% (IQR, 2.64%-6.34%) in repair tissue. A strong correlation (r = 0.701; 95% confidence interval: 0.21, 0.91) was found between ratios of signal intensity from native cartilage to signal intensity from repair tissue obtained with gagCEST or (23)Na imaging. The median of dimensionless ratios between native cartilage and repair tissue was 1.28 (IQR, 1.20-1.58) for gagCEST and 1.26 (IQR, 1.21-1.48) for (23)Na MR imaging.
  
  
  CONCLUSIONS
  The high correlation between the introduced gagCEST method and (23)Na imaging implies that gagCEST is a potentially useful biomarker for glycosaminoglycans.
authors: Division of Medical Physics in Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany. b.schmitt@dkfz-heidelberg.de
authors: Benjamin
authors: B
authors: Schmitt
authors: Stefan
authors: S
authors: Zbýn
authors: David
authors: D
authors: Stelzeneder
authors: Vladimir
authors: V
authors: Jellus
authors: Dominik
authors: D
authors: Paul
authors: Lars
authors: L
authors: Lauer
authors: Peter
authors: P
authors: Bachert
authors: Siegfried
authors: S
authors: Trattnig
mesh_terms: D000328:Adult; D054544:Arthroplasty, Subchondral; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology*; D003287:Contrast Media / Q000493:pharmacokinetics; D005260:Female; D006025:Glycosaminoglycans / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012975:Sodium Isotopes / Q000493:pharmacokinetics; D055815:Young Adult
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; D012975:Sodium Isotopes