title: Validation of high-resolution water-excitation magnetic resonance imaging for quantitative assessment of thin cartilage layers.
abstract: OBJECTIVE
  To employ a magnetic resonance (MR) imaging technique for quantitative assessment of thin cartilage layers, and to validate the cartilage volume and thickness measurements.
  
  
  METHODS
  We investigated 10 normal elbow joints (age 20 to 69 years) with a 3D gradient echo sequence with selective water excitation (TR 18 ms; TE 9 ms; FA 25 degrees, resolution 1x0.25x0.25 mm2, imaging time 19 min). After interpolating the image data to a 0.125x0.125 mm2 in-plane resolution, the cartilage plates were segmented, reconstructed in 3D, and the cartilage volume and thickness determined with a 3D Euclidean distance transformation algorithm, independent of the original section plane. The cartilage volume and thickness values were compared with CT arthrography and A-mode ultrasound.
  
  
  RESULTS
  The mean systematic difference between the elbow cartilage volume obtained from MR imaging and CT arthrography was -0.11% (-6.0 mm3) and the mean random difference 5.7% (314 mm3). Except for the fovea capitis radii, the deviations were not statistically significant (range -7.6 to +11.7%). In the humerus, the mean cartilage thickness (average = 1.35 mm) was overestimated relative to CT arthrography (+20.7%/+0.23 mm), and slightly underestimated relative to A-mode ultrasound (-6.0%/-0.05 mm). With few exceptions, there were no significant differences between MRI, CT arthrography and ultrasound in the other joint surfaces of the elbow (random deviations between 0.08 and 0.39 mm).
  
  
  CONCLUSIONS
  The technique presented can be applied for determining the cartilage volume and 3D thickness in joints with thin cartilage layers with a reasonable degree of accuracy.
authors.affiliation: Musculoskeletal Research Group, Institute of Anatomy, Ludwig-Maximilians-University Munich, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Graichen
authors.forename: V
authors.initials: V
authors.lastname: Springer
authors.forename: T
authors.initials: T
authors.lastname: Flaman
authors.forename: T
authors.initials: T
authors.lastname: Stammberger
authors.forename: C
authors.initials: C
authors.lastname: Glaser
authors.forename: K H
authors.initials: KH
authors.lastname: Englmeier
authors.forename: M
authors.initials: M
authors.lastname: Reiser
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000328:Adult; D000368:Aged; D002356:Cartilage / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity