INTRODUCTION: Lumbar vertebral disc degeneration is closely related to decreasing extracellular matrix (ECM) components (water, proteoglycan, and collagen) in both the nucleus pulposus (NP) and annulus fibrosus (AF) in earlier stages. Recently, several studies using delayed gadolinium‐enhanced magnetic resonance imaging of cartilage (dGEMRIC) in the relevant literature have shown that sulfated glycosaminoglycan (sGAG), reflecting proteoglycan contents, correlates with the difference of T1 values before and after penetration of Gd‐DTPA2‐ (ΔT1 value). Furthermore, water contents correlate with the T2 value using T2 mapping in MRI analysis. This study was undertaken to confirm the usefulness of the quantitative assessment of the lumbar vertebral disc degeneration using dGEMRIC and T2 mapping to compare biochemical measurements of the ECM component and the ΔT1 and T2 values.
METHODS: This study examined 20 Japanese white rabbits aged 6 months, 1, 2, 3 and 4 years. Their lumbar vertebral discs from L1‐2 to L5‐6 were imaged using 3.0 T MRI. We measured ΔT1 and T2 values using dGEMRIC and T2 mapping. Then, lumbar vertebral disc tissues from five consecutive levels were harvested; NP and AF were separated and analyzed biochemically. Statistical analyses were performed using Spearman's rank‐correlation coefficient.
RESULTS: A significant correlation was found between the ΔT1 value and sGAG (correlation coefficient of ‐0.327) for every aged rabbit. The T2 value showed a significant positive correlation with water content (correlation coefficient of 0.705) in every aged rabbit except the 6‐month‐old animal. No correlation was found between collagen type 1 and type 2 contents in any aged rabbit.
DISCUSSION: The ΔT1 and T2 values correlate significantly with biochemical measurements of ECM component in early degeneration of lumbar vertebral discs. Results suggest that these methods can predict early degenerative changes of ECM components.