title: Comparison of load responsiveness of cartilage T1rho and T2 in porcine knee joints: an experimental loading MRI study.
abstract: OBJECTIVE
  To compare changes in T1rho and T2 values of the femoral cartilage in porcine knee joints under staged loading and unloading conditions.
  
  
  METHODS
  Sixteen porcine knee joints with intact capsules and surrounding muscle were imaged using a custom-made pressure device and 3.0 T magnetic resonance imaging. Sagittal T1rho and T2 images were obtained for the lateral and medial condyles under the following compression loads: none (Load 0), 140 N (Load 140), 300 N (Load 300), and no compression after decompression (Post-load). The percentage changes of cartilage T1rho and T2 values under each loading condition from those at Load 0 were calculated for weight-bearing overall and eight subdivided regions of interest (ROIs) in both femoral condyles. The actual contact pressure under Load 140 and Load 300 was measured using pressure-sensitive film.
  
  
  RESULTS
  For the overall ROI, the mean decreases of T1rho and T2 values were 4.4% and 5.1% under Load 140% and 10.9% and 10.6% under Load 300 in the medial condyle and were 5.2% and 4.0% under Load 140% and 10.6% and 6.0% under Load 300 in the lateral condyle. In the medial condyle, the actual contact pressure correlated highly with percentage changes in T1rho (r = -0.84, P < 0.01) and T2 (r = -0.79, P < 0.01), but those correlations were relatively low in the lateral condyle.
  
  
  CONCLUSIONS
  Although there were side-dependent variations in the correlations with actual pressure, cartilage T1rho and T2 showed similarly sensitive responses to applied load.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hamada
authors.affiliation: Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, Osaka, Japan. Electronic address: nishii@rf7.so-net.ne.jp.
authors.forename: T
authors.initials: T
authors.lastname: Nishii
authors.affiliation: Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tamura
authors.affiliation: Department of Diagnostic and Interventional Radiology, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: GE Healthcare Applied Science Laboratory, Asia Pacific, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Wakayama
authors.affiliation: Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Sugano
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000502:physiology*; D005269:Femur / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011312:Pressure; D013552:Swine; D016474:Weight-Bearing / Q000502:physiology*
keywords: Cartilage T1rho; Cartilage T2; MRI; Staged loading