Interobserver and Test-Retest Reproducibility of T1ρ and T2 Measurements of Lumbar Intervertebral Discs by 3T Magnetic Resonance Imaging.

Objective: To investigate the interobserver and test-retest reproducibility of T1 rho and T2 measurements of lumbar intervertebral discs using 3T magnetic resonance imaging (MRI).Materials and Methods: This study included a total of 51 volunteers (female, 26; male, 25; mean age, 54 +/- 16.3 years) who underwent lumbar spine MRI with a 3.0 T scanner. Amongst these subjects, 40 underwent repeat T1 rho and T2 measurement acquisitions with identical image protocol. Two observers independently performed the region of interest measurements in the nuclei pulposi of the discs from L1-2 through L5-S1 levels. Statistical analysis was performed using intraclass correlation coefficient (ICC) with a two-way random model of absolute agreement. Comparison of the ICC values was done after acquisition of ICC values using Z test. Statistical significance was defined as p value < 0.05.Results: The ICCs of interobserver reproducibility were 0.951 and 0.672 for T1 rho and T2 mapping, respectively. The ICCs of test-retest reproducibility (40 subjects) for T1 rho and T2 measurements were 0.922 and 0.617 for observer A and 0.914 and 0.628 for observer B, respectively. In the comparison of the aforementioned ICCs, ICCs of interobserver and test-retest reproducibility for T1 rho mapping were significantly higher than T2 mapping (p < 0.001).Conclusion: The interobserver and test-retest reproducibility of T1 rho mapping were significantly higher than those of T2 mapping for the quantitative assessment of nuclei pulposi of lumbar intervertebral discs.