Evaluation of cartilage degradation in arthritis using T1q magnetic resonance imaging mapping

T1q magnetic resonance imaging (MRI) can be used to map proteoglycan (PG) loss in cartilage. Here, we used T1q MRI to map cartilage degradation in osteoarthritis (OA) and rheumatoid arthritis (RA). Tissue samples were obtained from five RA patients and 14 OA patients following total knee arthroplasty (TKA). Three parameters were measured: First, macroscopic grading of cartilage sample tissues was performed on a 5-grade scale (G0: normal, G1: swelling, G2: superficial fibrillation, G3: deep fibrillation, G4: subchondral bone exposure). Second, semi-quantitative values of PG were assessed by measuring the optical density of Safranin-O-stained paraffin sections that had been digitally photographed. Third, cartilage was divided into superficial and deep layers and the T1q values were quantified. T1q values of OA and RA in the superficial layers showed significant differences between groups (G0/1 and G0/2 for OA; G0/2 and G1/2 for RA). In the deep layers, T1q values of OA and RA also differed significantly between groups. In both the superficial and deep layers, there was a significant correlation between the mean T1q values and macroscopic grading (P\0.01 for OA, P\0.001 for RA). We found a negative correlation between the score of Safranin-O staining and T1q values (r = -0.61 for OA, r = -0.79 for RA). In addition, RA subjects had significantly higher T1q values than OA subjects of similar morphologic grade. In conclusion, T1q MRI is able to detect and map the early stages of cartilage degradation in OA and RA. This method is reliable and useful for the evaluation of macromolecular changes in arthritic cartilage.