In vivo quantification of T1ρ in lumbar spine disk spaces at 3 T using parallel transmission MRI.

OBJECTIVE: T1ρ MRI is an emerging, quantitative imaging modality that has been shown to correlate with proteoglycan content of disk material in vitro at 1.5 T. The purpose of this study is to quantify T1ρ values at all lumbar spine disk space levels at 3 T with parallel-transmission MRI in healthy adult volunteers. SUBJECTS AND METHODS: Thirty-four subjects (15 men, ages 21-60 years [mean age, 38.4 years]; and 19 women, ages 20-56 years [mean age, 36.5 years]) with no history of back pain or surgery underwent T1ρ MRI of the lumbar spine at 3 T with parallel transmission and sagittal T2-weighted imaging. Mean T1ρ values of all lumbar spine disk space levels were quantified. Linear regression analysis and Spearman rank correlation were performed on age, sex, degenerative grade (Pfirrmann scores), and T1ρ with significance set at p < 0.05 and correlations considered strong for r > 0.7 and moderate for r = 0.5-0.7. RESULTS: There was a statistically significant moderate negative correlation between T1ρ and subject age at disk space levels L1-2 through L4-5 (inclusive) (p < 0.001) and L5-S1 (p < 0.01). There was a statistically significant difference in T1ρ between all age groups sampled (p < 0.01) and a significant difference between T1ρ and Pfirrmann grades 1-3 (p < 0.01). CONCLUSION: T1ρ MRI in the lumbar spine with parallel transmission shows signifi-cant negative correlations with age at all disk space levels, which lends support to a potential role for T1ρ as a quantitative, in vivo biomarker of disk degeneration.