Utility of T2 mapping and dGEMRIC for evaluation of cartilage repair after allograft chondrocyte implantation in a rabbit model.

Summary Objective To investigate the effectiveness of quantitative Magnetic resonance imaging (MRI) for evaluating the quality of cartilage repair over time following allograft chondrocyte implantation using a three-dimensional scaffold for osteochondral lesions. Design Thirty knees from 15 rabbits were analyzed. An osteochondral defect (diameter, 4 mm; depth, 1 mm) was created on the patellar groove of the femur in both legs. The defects were filled with a chondrocyte-seeded scaffold in the right knee and an empty scaffold in the left knee. Five rabbits each were euthanized at 4, 8, and 12 weeks and their knees were examined via macroscopic inspection, histological and biochemical analysis, and quantitative MRI (T2 mapping and dGEMRIC) to assess the state of tissue repair following allograft chondrocyte implantation with a three-dimensional scaffold for osteochondral lesions. Results Comparatively good regenerative cartilage was observed both macroscopically and histologically. In both chondrocyte-seeded and control knees, the T2 values of repair tissues were highest at 4 weeks and showed a tendency to decrease with time. ΔR1 values of dGEMRIC also tended to decrease with time in both groups, and the mean ΔR1 was significantly lower in the CS-scaffold group than in the control group at all time points. ΔR1 = 1/r (R1post − R1pre), where r is the relaxivity of Gd-DTPA 2− , R1 = 1/T1 (longitudinal relaxation time). Conclusion T2 mapping and dGEMRIC were both effective for evaluating tissue repair after allograft chondrocyte implantation. ΔR1 values of dGEMRIC represented good correlation with histologically and biochemically even at early stages after the implantation.