T2 and T2* mapping in patients after matrix-associated autologous chondrocyte transplantation: initial results on clinical use with 3.0-Tesla MRI.

Objectives: To use T2 and T2* mapping in patients after matrix-associated autologous chondrocyte transplantation (MACT) of the knee, and to compare and correlate both methodologies.

Methods: 3.0-Tesla MRI was performed on 30 patients (34.6 +/- 9.9 years) with a follow-up period of 28.1 +/- 18.8 months after MACT. Multi-echo, spin-echo-based T2 mapping using six echoes and gradient-echo-based T2* mapping using six echoes were prepared. T2 and T2* maps were obtained using a pixel-wise, mono-exponential, non-negative least-squares fit analysis. Region-of-interest analysis was performed for mean (full-thickness) as well as deep and superficial aspects of the cartilage repair tissue and control cartilage sites.

Results: Mean T2 values (ms) were comparable for the control cartilage (53.4 +/- 11.7) and the repair tissue (55.5 +/- 11.6) (p > 0.05). Mean T2* values (ms) for control cartilage (30.9 +/- 6.6) were significantly higher than those of the repair tissue (24.5 +/- 8.1) (p < 0.001). Zonal stratification was more pronounced for T2* than for T2. The correlation between T2 and T2* was highly significant (p < 0.001), with a Pearson coefficient between 0.276 and 0.433.

Conclusion: T2 and T2* relaxation time measurements in the evaluation of cartilage repair tissue and its zonal variation show promising results, although the properties visualised by T2 and T2* may differ.