title: MRI pyschophysics: an experimental framework relating image quality to diagnostic performance metrics.
abstract: OBJECTIVE
  To determine the minimal image quality needed to preserve diagnostic performance relative to arthroscopy in the knee.
  
  
  METHODS
  Synthetic noise was added to images from clinical MRI scans (three-dimensional SPACE pulse sequence; Siemens) from five patients who had undergone knee MRI with arthroscopic follow-up, resulting in 25 simulated sets of images with standardized signal-to-noise ratios (SNRs) of 1, 2, 5, 10, or 20. All cases were scored by four musculoskeletal radiologists progressing from low to high SNR and grading all cartilage surfaces, major ligaments and menisci on a 5-point scale. Receiver operator characteristic (ROC) curves were constructed for the detection of meniscal tears and cartilage abnormalities. The area under the ROC curve (AUC) was determined for each structure at each SNR level. In addition, reader confidence was measured and pairwise comparisons across SNR levels were performed. Results were compared with arthroscopy as the reference standard.
  
  
  RESULTS
  ROC AUC was maximized for meniscal tears at SNR = 5 (structure specific CNR = 3.2) and for cartilage abnormalities at SNR = 10 (CNR = 4.2). Observer confidence was maximized for menisci at SNR = 5 (CNR = 8.0), for ligaments at SNR = 10 (CNR = 13.6) and cartilage at SNR = 10 (CNR = 8.2).
  
  
  CONCLUSIONS
  For 3D isotropic imaging in the knee, images with SNR < 10 or CNR < 10 should be rejected as nondiagnostic.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Durand
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
authors.forename: Laura M
authors.initials: LM
authors.lastname: Fayad
authors.forename: Thierry A G M
authors.initials: TA
authors.lastname: Huisman
authors.forename: Abdel-Monem M
authors.initials: AM
authors.lastname: El-Sharkawy
authors.forename: William A
authors.initials: WA
authors.lastname: Edelstein
mesh_terms: D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000523:psychology*; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014796:Visual Perception