title: Imaging of patellar cartilage with a 2D multiple-echo data image combination sequence.
abstract: OBJECTIVE
  We sought to evaluate the diagnostic value of a 2D multiple-echo data image combination (MEDIC) MRI sequence in the detection of patellar cartilage defects.
  
  
  METHODS
  Our study included 52 consecutive patients who had knee surgery within 4 months of undergoing an MRI examination including an axial 2D MEDIC (TR/TE, 884/26; flip angle, 30 degrees ) sequence. Cartilage was surgically graded on a 5-point scale: 0, normal; 1, softening or swelling; 2, partial thickness defect; 3, fissuring to the level of the subchondral bone; or 4, exposed subchondral bone. Cartilage was graded on MRI according to a scale that was almost identical to the surgical scale except that grade 1 lesions were defined as signal alteration or swelling of cartilage. Two blinded reviewers independently analyzed patellar cartilage. Sensitivity, specificity, accuracy, and weighted kappa values for interobserver variability were calculated.
  
  
  RESULTS
  Low-grade cartilage lesions predominated in our study group. When grade 2 or higher was considered the threshold for relevance, the sensitivity, specificity, and accuracy for the MEDIC sequence was as high as 79%, 82%, and 81%, respectively. Increasing the threshold of relevance to grade 3 increased the sensitivity, specificity, and accuracy to as high as 83%, 91%, and 90%, respectively. Interobserver agreement for the MEDIC sequence was good (weighted kappa = 0.68).
  
  
  CONCLUSIONS
  The 2D MEDIC sequence performs comparably to previously described sequences optimized for cartilage imaging such as the 3D double-echo steady-state or 3D spoiled gradient-recalled sequences with good interobserver agreement, high sensitivity, and excellent specificity for revealing low- to intermediate-degree cartilage defects.
authors.affiliation: Department of Radiology, University Hospital Balgrist, Forchstrasse 340, Zurich CH-8008, Switzerland.
authors.forename: Marius R
authors.initials: MR
authors.lastname: Schmid
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
authors.forename: Peter
authors.initials: P
authors.lastname: Koch
authors.forename: Marco
authors.initials: M
authors.lastname: Zanetti
authors.forename: Bernd
authors.initials: B
authors.lastname: Kuehn
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
mesh_terms: D000328:Adult; D001182:Arthroscopy; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010329:Patella / Q000473:pathology*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity