title: Improved assessment of cartilage repair tissue using fluid-suppressed ²³Na inversion recovery MRI at 7 Tesla: preliminary results.
abstract: OBJECTIVE
  To evaluate cartilage repair and native tissue using a three-dimensional (3D), radial, ultra-short echo time (UTE) (23)Na MR sequence without and with an inversion recovery (IR) preparation pulse for fluid suppression at 7 Tesla (T).
  
  
  METHODS
  This study had institutional review board approval. We recruited 11 consecutive patients (41.5 ± 11.8 years) from an orthopaedic surgery practice who had undergone a knee cartilage restoration procedure. The subjects were examined postoperatively (median = 26 weeks) with 7-T MRI using: proton-T2 (TR/TE = 3,000 ms/60 ms); sodium UTE (TR/TE = 100 ms/0.4 ms); fluid-suppressed, sodium UTE adiabatic IR. Cartilage sodium concentrations in repair tissue ([Na(+)](R)), adjacent native cartilage ([Na(+)](N)), and native cartilage within the opposite, non-surgical compartment ([Na(+)](N2)) were calculated using external NaCl phantoms.
  
  
  RESULTS
  For conventional sodium imaging, mean [Na(+)](R), [Na(+)](N), [Na(+)](N2) were 177.8 ± 54.1 mM, 170.1 ± 40.7 mM, 172.2 ± 30 mM respectively. Differences in [Na(+)](R) versus [Na(+)](N) (P = 0.59) and [Na(+)](N) versus [Na(+)](N2) (P = 0.89) were not significant. For sodium IR imaging, mean [Na(+)](R), [Na(+)](N), [Na(+)](N2) were 108.9 ± 29.8 mM, 204.6 ± 34.7 mM, 249.9 ± 44.6 mM respectively. Decreases in [Na(+)](R) versus [Na(+)](N) (P = 0.0.0000035) and [Na(+)](N) versus [Na(+)](N2) (P = 0.015) were significant.
  
  
  CONCLUSIONS
  Sodium IR imaging at 7 T can suppress the signal from free sodium within synovial fluid. This may allow improved assessment of [Na(+)] within cartilage repair and native tissue.
  
  
  CONCLUSIONS
  • NaIR magnetic resonance imaging can suppress signal from sodium within synovial fluid. • NaIR MRI thus allows assessment of sodium concentration within cartilage tissue alone. • This may facilitate more accurate assessment of repair tissue composition and quality.
authors.affiliation: Quantitative Multinuclear Musculoskeletal Imaging Group, Center for Biomedical Imaging, Department of Radiology, NYU Langone Medical Center, 660 First Avenue, New York, NY 10016, USA. gregory.chang@nyumc.org
authors.forename: Gregory
authors.initials: G
authors.lastname: Chang
authors.forename: Guillaume
authors.initials: G
authors.lastname: Madelin
authors.forename: Orrin H
authors.initials: OH
authors.lastname: Sherman
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Strauss
authors.forename: Ding
authors.initials: D
authors.lastname: Xia
authors.forename: Michael P
authors.initials: MP
authors.lastname: Recht
authors.forename: Alexej
authors.initials: A
authors.lastname: Jerschow
authors.forename: Ravinder R
authors.initials: RR
authors.lastname: Regatte
mesh_terms: D000328:Adult; D000465:Algorithms; D001826:Body Fluids; D002358:Cartilage, Articular / Q000293:injuries* / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019651:Plastic Surgery Procedures; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium; D016896:Treatment Outcome
chemical_list: D012964:Sodium