Relationship between NMR transverse relaxation, trabecular bone architecture, and strength

Area of Science:

• Biomedical Engineering
• Materials Science
• Radiology

Background:

• Cancellous bone's biomechanical competence is crucial for skeletal integrity.
• Assessing bone strength non-invasively is vital for managing conditions like osteoporosis.
• Nuclear Magnetic Resonance (NMR) line broadening (R'2) reflects water properties within bone's porous structure.

Purpose of the Study:

• To investigate the relationship between NMR line broadening (R'2) and the structural and biomechanical properties of human cancellous bone.
• To determine if trabecular microstructure influences R'2.
• To explore the potential of quantitative magnetic resonance for in vivo assessment of bone health.

Main Methods:

• Analysis of 22 human lumbar vertebral cancellous bone specimens using NMR microscopy and digital image processing.
• Measurement of Young's modulus of elasticity to assess biomechanical competence.
• Evaluation of NMR line broadening (R'2) and its correlation with structural parameters like trabecular plate density.

Main Results:

• A strong positive association was found between Young's modulus and R'2 (r = 0.91, P < 0.0001).
• NMR line broadening is influenced by the magnetic field inhomogeneity caused by mineralized bone and marrow water.
• Trabecular microstructure, especially mean trabecular plate density, significantly predicts R'2 (r = 0.74, P < 0.0001).

Conclusions:

• NMR transverse relaxation rate in human cancellous bone is significantly determined by biomechanically relevant structural parameters.
• Trabecular microstructure, particularly plate density, is a key determinant of R'2.
• Quantitative magnetic resonance shows promise for in vivo assessment of fracture risk in conditions like osteoporosis.