title: Magnetic resonance imaging of the knee at 3 and 7 tesla: a comparison using dedicated multi-channel coils and optimised 2D and 3D protocols.
abstract: OBJECTIVE
  To show the feasibility and possible superiority of two 7 Tesla knee protocols ("7 T high resolution" and "7 T quick") using a new 28-channel knee coil compared to an optimised 3 T knee protocol using an 8-channel knee coil.
  
  
  METHODS
  The study was approved by the ethics committee. Both 3 T and 7 T MRI of the knee were performed in 10 healthy volunteers (29.6 ± 7.9 years), with two 2D sequences (PD-TSE and T1-SE) and three isotropic 3D sequences (TRUFI, FLASH and PD-TSE SPACE). Quantitative contrast-to-noise ratio (CNR) and qualitative evaluations were performed by different readers, and intra- and inter-rater agreement was assessed.
  
  
  RESULTS
  The signal-to-noise ratio (SNR) as well as the CNR values for cartilage-bone, cartilage-fluid, cartilage-menisci and menisci-fluid were, in most cases, higher at 7 T compared to 3 T, and the 7 T quick measurement was slightly superior compared to the 7 T high-resolution measurement. The results of the subjective qualitative analysis were higher for the 7 T measurements compared to the 3 T measurements. Inter- and intra-observer reliability was high (0.884-0.999).
  
  
  CONCLUSIONS
  Through higher field strength and an optimal coil, resolution at 7 T can be increased and acquisition time can be reduced, with superior quantitative and comparable qualitative results compared to 3 T.
authors.affiliation: MR Center, Department of Radiology, Medical University of Vienna, Lazarettgasse 14, 1090 Vienna, Austria. welsch@bwh.harvard.edu
authors.forename: Goetz H
authors.initials: GH
authors.lastname: Welsch
authors.forename: Vladimir
authors.initials: V
authors.lastname: Juras
authors.forename: Pavol
authors.initials: P
authors.lastname: Szomolanyi
authors.forename: Tallal C
authors.initials: TC
authors.lastname: Mamisch
authors.forename: Peter
authors.initials: P
authors.lastname: Baer
authors.forename: Claudia
authors.initials: C
authors.lastname: Kronnerwetter
authors.forename: Matthias
authors.initials: M
authors.lastname: Blanke
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fujita
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
mesh_terms: D000328:Adult; D000465:Algorithms; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000379:methods*; D066298:In Vitro Techniques; D007719:Knee Joint / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity