Comparison of T1rho and T2 Mapping of Knee Articular Cartilage in an Asymptomatic Population

Objective: To analyze subregional differences in T1rho (T1 rho) and T2 values and their correlation in asymptomatic knee cartilage, and to evaluate angular dependence with magic angles. Materials and Methods: Six asymptomatic volunteers underwent knee MRI with T1 rho and T2 mapping. T1 rho and T2 values were measured by two radiologists independently, at nine subregions in the medial femoral condyle (MFC) cartilage, at angles of +/- 0 degrees, 15 degrees, 35 degrees, 55 degrees, 75 degrees respective to a vertical line (B0) bisecting the width of the distal femur, and at two locations in the patella. Subregional values of T1 rho and T2 were analyzed and significant differences in three divided portions of the MFC (anterior, central, and posterior) were statistically evaluated. Correlation between T1 rho and T2 and angular dependence with magic angles were also assessed for statistical significance. Results: T1 rho values were lowest at +15 degrees and highest at -55 degrees. T2 values were lowest at +75 degrees and highest at +35 degrees Both T1 rho and T2 were higher in superior patella than inferior patella. T1 rho showed significant differences in the three divided portions of the MFC, while T2 showed significant differences only between central and posterior portions. There was a weak correlation between T1 rho and T2 (r = 0.217, p = 0.127). T1 rho showed more angular dependence than T2. Conclusion: T1 rho and T2 showed different subregional values and angular dependence in asymptomatic knee cartilage with a weak correlation. Awareness of these differences will aid in assessment of cartilage in a specific subregion of the knee.