H. Chung et al., RELATIONSHIP BETWEEN NMR TRANSVERSE RELAXATION, TRABECULAR BONE ARCHITECTURE, AND STRENGTH, Proceedings of the National Academy of Sciences of the United Statesof America, 90(21), 1993, pp. 10250-10254
Structure, biomechanical competence, and incremental NMR line broadeni
ng (R2') of water in the inter-trabecular spaces of cancellous bone we
re examined on 22 cylindrical specimens from the lumbar vertebral bodi
es of 16 human subjects 24-86 years old (mean, 60 years old). A strong
association (r = 0.91; P < 0.0001) was found between Young's modulus
of elasticity and R2' for a wide range of values corresponding to canc
ellous bone of very different morphologic composition. NMR line broade
ning is caused by the inhomogeneity of the magnetic field induced as a
consequence of the coexistence of two adjacent phases of different di
amagnetic susceptibility-i.e., mineralized bone and water in the marro
w spaces. Structural analyses performed by means of NMR microscopy and
digital image processing indicated that the variation in R2' is close
ly related to the trabecular microstructure. Mean trabecular plate den
sity measured along the direction of the magnetic field was found to p
lay a major role in predicting R2' (r = 0.74; P < 0.0001). This behavi
or was confirmed when the plate density was varied in individual speci
mens, which was achieved by rotating the specimen, making use of the b
one's structural anisotropy. It is concluded that the NMR transverse r
elaxation rate in human cancellous bone of the spine is significantly
determined by trabecular structural parameters relevant to biomechanic
al strength. The results further underscore the important role played
by the transverse trabeculae in contributing to cancellous bone streng
th. The work has implications on possible in vivo use of quantitative
magnetic resonance for the assessment of fracture risk in osteoporotic
patients.