MR diffusion is sensitive to mechanical loading in human intervertebral disks ex vivo

Area of Science:

• Biomedical Engineering
• Radiology
• Orthopedics

Background:

• Intervertebral disc degeneration is a major cause of low back pain.
• Accurate assessment of disc mechanical function is crucial for understanding degeneration.

Purpose of the Study:

• To investigate changes in human lumbar disc mechanical function using T2 and diffusion magnetic resonance (MR) imaging with increasing degeneration.
• To correlate MR parameters with dynamic and viscoelastic properties of the discs.

Main Methods:

• Five human cadaveric lumbar discs were subjected to compressive loads.
• Spatial changes in T2 and diffusion MR parameters were quantified.
• Regression models analyzed relationships between MR parameters and disc mechanical properties.

Main Results:

• Compressive loading significantly reduced disc diffusivity but minimally affected T2 values.
• Diffusivity and T2 correlated with dynamic and viscoelastic stiffness.
• Diffusivity, but not T2, correlated with viscoelastic dampening and instantaneous stiffness.
• MR-estimated hydration correlated with nucleus and annulus stiffness.

Conclusions:

• Strong correlations between diffusion MR parameters and disc mechanics suggest MR's potential for quantitative assessment.
• MR imaging may enable evaluation of disc functional status and structural integrity in degenerative states.