Study Design: An in-vivo serial magnetic resonance imaging study of diffusion characteristics in human lumbar discs over 24 hours in healthy volunteers and patients with low back pain. Objective: Nutrition to the disc is solely by diffusion but no firm data is available on diffusion pattern in humans. This study reports diffusion patterns in a human population studied and documents the 24-hour diffusion pattern.
Methods: T1-weighted images were obtained pre and post-contrast with Gadodiamide-0.3mmol/kg at 5, 10 minutes, 2, 4, 6, 12 and 24hours. Diffusion was calculated by measuring signal intensity values in seven regions of interest (anterior and posterior annulus, anterior, posterior, peripheral (PNP) and central (CNP) parts of nucleus pulposus (NP). Enhancement percentage (EP), Peak enhancement percentage (PEP) and time to achieve PEP (Tmax) were calculated.
Subjects: Of the 215 discs in 43 persons (10 volunteers and 33 patients) 96 discs were normal and considered for study.
Results: Diffusion occurred mainly from the endplate (rather than annulus). The mean EP of PNP and CNP at 5 minutes was 6.7, 3.9; 10minutes was 7.5, 4.0; 2 hours was 36.6, 17.9; 4hrs was 42.8, 29.8; 6hrs was 51.7, 40.5; 12hrs was 35.9, 27.8 and 24 hours was 33.3, 27.9. Though PEP was achieved at 6 hours in NP, the CNP lagged behind throughout. Univariate ANOVA showed that there was significant difference (p<
0.0001) in PEP of NP between the age groups of less than ten (72.4) and higher (37.9). The mean PEP at the NP of lower two discs (26.8) was less compared to upper two discs 41.0(p=0.059). Stepwise linear regression analysis showed that diffusion to the CNP was significantly influenced by age (R2 =0.324), followed by level of disc (R2=0.5).
Conclusion: This is the first study to document the normal 24-hour diffusion pattern across lumbar discs. The data can form the basis for comparison of diffusion changes in degeneration, Modic’s endplate changes and smoking.
