title: MR pharmacokinetic modeling of the patellar cartilage differentiates normal from pathological conditions.
abstract: OBJECTIVE
  To study the pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of the patellar cartilage under normal and pathological conditions.
  
  
  METHODS
  DCE-MRI was obtained in 22 cases. There were 17 patients with degenerative patellar conditions (eight with chondromalacia and nine with osteoarthritis) and five normal subjects. The cartilage pharmacokinetic parameters of K(trans) (vascular permeability), k(ep) (extraction ratio), upsilon(e) (extravascular extracellular space [EES] volume fraction), and upsilon(p) (intravascular space volume fraction) were extracted.
  
  
  RESULTS
  Statistically significant differences were observed between the different groups (normal cartilage, chondromalacia and osteoarthritis) for K(trans) and upsilon(e). K(trans) values were (mean +/- SD) 1.06 +/- 0.62, 11.97 +/- 8.91, and 21.21 +/- 16.03 mL x minute(-1) x 100 mL(-1) (P < 0.02), respectively; and upsilon(e) values were 0.71 +/- 0.69, 3.59 +/- 2.21, and 10.51 +/- 8.20% (P < 0.002). Reproducibility of the pharmacokinetic calculations was assessed with a second set of analyses of 10 random cases one week after the first analysis, showing a test-retest root mean square (RMS) coefficient of variation of 9.78% for K(trans) and 14.72% for upsilon(e).
  
  
  CONCLUSIONS
  The vascular permeability and EES fraction of cartilage increases with the severity of the degeneration. Pharmacokinetic models allow to study the vascular properties of the cartilage and may have applications as a surrogate index in longitudinal studies to quantify the evolution of drug trials.
authors.affiliation: Radiology Department, Hospital Quirón, Valencia, Spain. rsanz.val@quiron.es
authors.forename: Roberto
authors.initials: R
authors.lastname: Sanz
authors.forename: Luis
authors.initials: L
authors.lastname: Martí-Bonmatí
authors.forename: José Luis
authors.initials: JL
authors.lastname: Rodrigo
authors.forename: David
authors.initials: D
authors.lastname: Moratal
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002358:Cartilage, Articular / Q000473:pathology*; D046789:Chondromalacia Patellae / Q000473:pathology*; D003287:Contrast Media / Q000493:pharmacokinetics*; D005260:Female; D019786:Gadolinium DTPA / Q000493:pharmacokinetics*; D006801:Humans; D007592:Joint Diseases / Q000473:pathology*; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D020370:Osteoarthritis, Knee / Q000473:pathology*; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA