Adjacent cartilage tissue structure after successful transplantation: a quantitative MRI study using T mapping and texture analysis.

OBJECTIVES

The aim of this study was to assess the texture of repair tissue and tissue adjacent to the repair site after matrix-associated chondrocyte transplantation (MACT) of the knee using gray-level co-occurrence matrix (GLCM) texture analysis of T quantitative maps.

METHODS

Twenty patients derived from the MRI sub-study of multicenter, single-arm phase III study underwent examination on a 3 T MR scanner, including a T mapping sequence 12 and 24 months after MACT. Changes between the time points in mean T values and 20 GLCM features were assessed for repair tissue, adjacent tissue, and reference cartilage. Differences in T values and selected GLCM features between the three cartilage sites at two time points were analyzed using linear mixed-effect models.

RESULTS

A significant decrease in T values after MACT, between time points, was observed only in repair cartilage (p < 0.001). Models showed significant differences in GLCM features between repair tissue and reference cartilage, namely, autocorrelation (p < 0.001), correlation (p = 0.015), homogeneity (p = 0.002), contrast (p < 0.001), and difference entropy (p = 0.047). The effect of time was significant in a majority of models with regard to GLCM features (except autocorrelation) (p ≤ 0.001). Values in repair and adjacent tissue became similar to reference tissue over time.

CONCLUSIONS

GLCM is a useful add-on to T mapping in the evaluation of knee cartilage after MACT by increasing the sensitivity to changes in cartilage structure. The results suggest that cartilage tissue adjacent to the repair site heals along with the cartilage implant.

KEY POINTS

• GLCM is a useful add-on to T mapping in the evaluation of knee cartilage after MACT by increasing the sensitivity to changes in cartilage structure. • Repair and adjacent tissue became similar to reference tissue over time. • The results suggest that cartilage tissue adjacent to the repair site heals along with the cartilage implant.