Adiabatic rotating frame relaxation of MRI reveals early cartilage degeneration in a rabbit model of anterior cruciate ligament transection

Objective: To investigate the sensitivity of seven quantitative magnetic resonance imaging (MRI) parameters (adiabatic T-1 rho, adiabatic T-2 rho, continuous wave (CW) T-1 rho, relaxation along a fictitious field (RAFF), T-2 measured with adiabatic double echo (DE) and Carr-Purcell-Meiboom-Gill (CPMG) sequence, and T-1 during off-resonance saturation [magnetization transfer (MT)]) to detect early osteoarthritic changes in a rabbit model of anterior cruciate ligament transection (ACLT). Methods: ACLT was unilaterally induced in the knees of New Zealand White rabbits (n = 8) while contralateral joints served as controls. Femoral condyles of the joints were harvested 4 weeks post-ACLT. MRI was performed at 9.4 T. For reference, quantitative histology, Mankin grading and biomechanical measurements were conducted. Results: Reference methods demonstrated early, superficial cartilage degeneration in the ACLT group, including significant loss of proteoglycans in both medial and lateral compartments, increased collagen fibril anisotropy in the lateral condyle and decreased biomechanical properties at both medial and lateral compartments. CW-T-1 rho was prolonged in the lateral compartment of ACLT joints while adiabatic T-1 rho and T-2 rho detected degenerative changes in tissue in both lateral and medial condyles (P < 0.05). DE-T-2 was significantly (P < 0.05) elevated only in the lateral compartment while CPMG-T-2, MT or RAFF did not show a statistically significant difference between the groups. Conclusions: Adiabatic T-1 rho and T-2 rho relaxation times detected most sensitively early degenerative changes in cartilage 4 weeks post-ACLT in a rabbit model. (C) 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.