Interobserver and test-retest reproducibility of T1ρ and T2 measurement of lumbar intervertebral disc by using 3T magnetic resonance imaging

Abstract

Objective: To investigate the interobserver and test-retest reproducibility of T1ρ and T2 measurements of lumbar intervertebral discs using 3T magnetic resonance imaging (MRI). Material and Methods: A total of 51 volunteers (female, 26; male, 25; mean age, 54 ± 16.3 years) underwent lumbar spine MRI with a 3.0 T scanner. Of these subjects, 40 underwent repeat T1ρ and T2 measurement acquisitions with identical image protocol. Two observers independently performed the region of interest (ROI) measurements in the nuclei pulposi of the discs from L1–2 through L5–S1 levels. The discs were then assigned to either non-degenerated (grades 1 and 2) or degenerated (grades 3 and 4) disc groups according to the Pfirrmann grading system, excluding grade 5 discs. The mean T1ρ and T2 measurements of the lumbar intervertebral discs were compared between the two groups. Statistical analysis was performed using the Student’s t-test and intraclass correlation coefficient (ICC). Statistical significance was defined at p-value < 0.05. Results: The ICCs of interobserver reproducibility were 0.951 and 0.672 for T1ρ and T2 mapping, respectively. The ICCs of test-retest reproducibility (40 subjects) for T1ρ and T2 measurements were 0.922 and 0.617 for observer A and 0.914 and 0.628 for observer B, respectively. The T1ρ and T2 values in the degenerated intervertebral disc group were significantly lower than those of the non-degenerated group (p < 0.001). Conclusions: The interobserver and test-retest reproducibility of T1ρ mapping were superior to those of T2 mapping for the quantitative assessment of nuclei pulposi of lumbar intervertebral discs.