title: Comparison of Routine Knee Magnetic Resonance Imaging at 3 T and 7 T.
abstract: OBJECTIVE
  The aim of this study was to compare quantitative and semiquantitative parameters (signal-to-noise ratio [SNR] and diagnostic confidence) from a standard knee magnetic resonance imaging (MRI) examination with comparable sequence protocols and acquisition times at 3 T and at 7 T.
  
  
  METHODS
  Forty patients experiencing knee pain of unknown etiology underwent comparable MR protocols with standard turbo-spin echo and short tau inversion recovery sequences of the knee joint (5 sequences) at 3 T and 7 T. For quantitative analysis, SNR was determined using these 5 sequences and 3 additional morphological sequences. For a semiquantitative assessment of diagnostic confidence, a diagnostic confidence score (DCS) was assigned, using a 10-point scale. Two experienced radiologists who specialized in musculoskeletal imaging and who were blinded to the field-strength independently assessed 22 potential pathological findings, in total, in 4 anatomically defined areas in the knee joint and rated their diagnostic confidence.
  
  
  RESULTS
  In quantitative analysis, all sequences provided higher voxel-volume-adjusted SNR values at 7 T compared with that at 3 T. In semiquantitative analysis, summed DCS values for potential pathological findings in each of the 4 anatomically defined areas were higher at 7 T compared with that at 3 T. There was a statistically significant improvement in the DCS for both readers at 7 T for the diagnosis and exclusion of focal or diffuse grade I or II cartilage defects in the patellar cartilage. For 8 potential pathological findings, a statistically significant difference between the 2 field-strengths could be observed for 1 reader only. For the residual 13 potential pathological findings, there was no statistically significant difference observed. The percentage of concordant ratings was 84.6% at 3 T and 85.4% at 7 T.
  
  
  CONCLUSIONS
  Ultra-high-field MRI at 7 T improved the overall diagnostic confidence in routine MRI of the knee joint compared with that at 3 T. This is especially true for small joint structures and subtle lesions. Higher spatial resolution was identified as the main reason for this improvement.
authors.affiliation: From the *High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, and †Department of Orthopaedics, Medical University of Vienna, Vienna, Austria; ‡Siemens Healthcare Pty Ltd Australia, Imaging & Therapy Systems, Magnetic Resonance, Macquarie Park, New South Wales, Australia; §Siemens Healthcare, Erlangen, Germany; and ∥CD Laboratory for Molecular Clinical MR Imaging, Vienna, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Springer
authors.forename: Klaus
authors.initials: K
authors.lastname: Bohndorf
authors.forename: Vladimir
authors.initials: V
authors.lastname: Juras
authors.forename: Pavol
authors.initials: P
authors.lastname: Szomolanyi
authors.forename: Štefan
authors.initials: Š
authors.lastname: Zbýň
authors.forename: Markus M
authors.initials: MM
authors.lastname: Schreiner
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schmitt
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007592:Joint Diseases / Q000000981:diagnostic imaging / Q000473:pathology; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D059629:Signal-To-Noise Ratio; D055815:Young Adult