Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Quantitative T2 mapping seems to reflect differences in repair tissues formed after two surgical cartilage repair procedures. (c) RSNA, 2008.

Purpose:To use a 3D gradient-echo (GRE) sequence with two flip angles for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) to evaluate relative glycosaminoglycan content of repair tissue after matrix-associated autologous chondrocyte transplantation (MACT). Materials and Methods:In a phantom study, T1-mapping based on a 3D-GRE sequence with different flip angle combinations was compared with a standard inversion recovery (IR) sequence at 3.0T. Fifteen patients were examined after MACT in the knee at "3-13 months" (group I) and "19 -42 months" (group II). The ␦ relaxation rate (␦R1) calculated for repair tissue and normal hyaline cartilage was measured and mean values were compared in different postoperative intervals using analysis of variance. Results:The flip angle combination 35/10°provided the best agreement with IR sequence for short and long T1 values. The mean ␦R1 for repair tissue was 2.49 versus 1.04 at the intact control site in group I and 1.90 compared with 0.81 in group II. Differences from repair tissue to control sites showed statistically significance for both groups; no significant difference was found between groups. Conclusion:The 3D dual flip angle dGEMRIC technique optimized for cartilage imaging is comparable to standard T1 IR technique for T1 mapping. Furthermore, the preliminary in vivo study demonstrates the feasibility of the technique in the evaluation of MACT patients.

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