title: 23Na MR imaging at 7 T after knee matrix-associated autologous chondrocyte transplantation preliminary results.
abstract: OBJECTIVE
  To evaluate the feasibility of sodium 7-T magnetic resonance (MR) imaging in repaired tissue and native cartilage of patients after matrix-associated autologous chondrocyte transplantation (MACT) and compare results with delayed gadolinium-enhanced MR imaging of cartilage (dGEMRIC) at 3 T.
  
  
  METHODS
  Ethical approval was provided by the local ethics committee; written informed consent was obtained from all patients. Six women and six men (mean age, 32.8 year ± 8.2 [standard deviation] and 32.3 years ± 12.7, respectively) were included. Mean time between MACT and MR was 56 months ± 28. A variable three-dimensional (3D) gradient-echo (GRE) dual-flip-angle technique was used for T1 mapping before and after contrast agent administration at 3 T. All patients were also examined at 7 T (mean delay, 70.5 days ± 80.1). A sodium 23-only transmit-receive knee coil was used with the 3D GRE sequence. A statistical analysis of variance and Pearson correlation were applied.
  
  
  RESULTS
  Mean signal-to-noise ratio (SNR) was 24 in native cartilage and was 16 in transplants (P < .001). Mean sodium signal intensities normalized with the reference sample were 174 ± 53 and 267 ± 42 for repaired tissue in the cartilage transplant and healthy cartilage, respectively (P < .001). Mean postcontrast T1 values were 510 msec ± 195 and 756 msec ± 188 for repaired tissue and healthy cartilage, respectively (P = .005). Mean score of MR observation of cartilage repair tissue was 75 ± 14. Association between postcontrast T1 and normalized sodium signal values showed a high Pearson correlation coefficient (R) of 0.706 (P = .001). A high correlation of R = 0.836 (P = .001) was found between ratios of normalized sodium values and ratios of T1 postcontrast values.
  
  
  CONCLUSIONS
  With the modified 3D GRE sequence at 7 T, a sufficiently high SNR in sodium images was achieved, allowing for differentiation of repaired tissue from native cartilage after MACT. A strong correlation was found between sodium imaging and dGEMRIC in patients after MACT.
authors: Department of Radiology, MR Centre-High Field MR, Medical University of Vienna, Lazarettgasse 14, Vienna, Austria. siegfried.trattnig@meduniwien.ac.at
authors: Siegfried
authors: S
authors: Trattnig
authors: Goetz H
authors: GH
authors: Welsch
authors: Vladimir
authors: V
authors: Juras
authors: Pavol
authors: P
authors: Szomolanyi
authors: Marius E
authors: ME
authors: Mayerhoefer
authors: David
authors: D
authors: Stelzeneder
authors: Tallal C
authors: TC
authors: Mamisch
authors: Oliver
authors: O
authors: Bieri
authors: Klaus
authors: K
authors: Scheffler
authors: Stefan
authors: S
authors: Zbýn
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002358:Cartilage, Articular / Q000473:pathology* / Q000601:surgery*; D019902:Chondrocytes / Q000637:transplantation*; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012975:Sodium Isotopes; D014182:Transplantation, Autologous; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D012975:Sodium Isotopes