Reproducibility of in vivo magnetic resonance imaging T 1 rho and T 2 relaxation time measurements of hip cartilage at 3.0T in healthy volunteers.

PURPOSE: To assess the T1 ρ and T2 values in the hip cartilage of healthy volunteers and to evaluate the reproducibility of these measurements.

MATERIALS AND METHODS: The right hip joint of 30 asymptomatic volunteers was explored with 3T magnetic resonance imaging (MRI). Quantitative 3D T1 ρ- and T2 -maps sequences were repeated twice with a 30-minute delay (immediate reproducibility). The same protocol was repeated 14 days later (short-term reproducibility). Immediate and short-term reproducibility were estimated using coefficients of variation and correlation concordance coefficients (CCC). The precisions of the measurements were estimated by the ratio of the standard deviations. A mixed linear model was used to analyze the effect of patient's characteristics on T1 ρ and T2 values.

RESULTS: Immediate reproducibility was significantly better than short-term reproducibility for T1 ρ (CCC of 0.75 versus 0.55; P = 0.007) and T2 (CCC 0.65 versus 0.32; P < 0.001). The precisions of the measurements were estimated between 5.5% and 9.1%. Median T1 ρ values were 6.0 msec higher in women than in men (P = 0.006), with no significant influence of age, body mass index (BMI), or sports activity. Median T2 values were not significantly different between men and women (0.4 msec lower in women; P = 0.76). There was no significant influence of age, BMI, or sports activity. T1 ρ and T2 values were lower in lateral regions than in medial regions (4.9 msec and 2.5 msec lower respectively; P < 0.0001).

CONCLUSION: Immediate reproducibility of T1 ρ and T2 values is better than short-term, with limited effect of 30 minutes decubitus. T1 ρ values are significantly higher in women.

LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1022-1033.