Cartilage evaluation with biochemical MR imaging using in vivo Knee compression at 3T-comparison of patients after cartilage repair with healthy volunteers.

Magnetic resonance (MR) transverse relaxation time (T2) mapping has been frequently used to evaluate collagen content and its organization. In this study, MR T2 mapping, using the multi-slice, multi-echo Carr-Purcell-Meiboom-Gill technique, was performed in volunteers and patients after matrix-associated autologous chondrocyte transplantation (MACT) under unloading and loading conditions with an MR-compatible compression device. In the volunteer study, a statistically significant decrease in the cartilage MR T2 values was observed during the loading phase when compared to the initial load-free measurement. During the recovery period, a statistically significant increase in the T2 values was found in the central superficial layer (p=0.001), the central deep layer (p=0.005), the posterior deep layer (p=0.001), and in the tibia superficial layer (p=0.01) when compared to measurements under loading. In patients after MACT, during unloading or loading conditions, statistically significant changes in T2 values were observed in the transplant deep zone (p=0.005), in the posterior deep zone (p=0.004), and in the tibia superficial zone (p=0.012). The results of this study show that MR T2 mapping under loading conditions may provide additional information about cartilage repair tissue composition and organization during the postoperative follow-up, and may help to evaluate the efficacy of cartilage-repair surgery techniques.