We propose to evaluate and further develop a novel technique based on magnetic resonance (MR) for quantitative assessment of the structure of trabecular bone in normals and patients with clinically established osteoporosis. We intend to determine whether this index of trabecular structure predicts the presence of fractures in patients with osteoporosis and to compare and correlate the findings of this new parameter with bone mineral density measurements. The new technique is based on a measurement of MR T2* which is related to the intrinsic inhomogeneity of the magnetic field in the intertrabecular space, caused by the presence of two phases of different diamagnetic susceptibility: bone and bone marrow. In support of this hypothesis, our preliminary data show that T2* increases in the lumbar vertebrae with age and is markedly increased in patients with clinically evident osteoporosis with fractures. Moreover, we have found that T2* predicts the degree of trabeculation of die distal femur with T2* following the order: diaphysis>metaphysis>epiphysis. Both findings corroborate the expected inverse relationship between trabecular plate density and T2*. A technique, denoted MR interferometry, developed in the investigators' laboratory, permits measurement of T2* from a series of gradient-who images acquired with an array of echo delays, using ROI analysis and curve fitting techniques. We intend to establish a normal baseline by measuring T2* as well as the apparent fat/water ratio (a by-product of the analysis) in 75 normal women. To assess the sensitivity and specificity of this technique in osteoporosis, we compare MR indices of trabecular structure with those obtained from bone mineral density measurements in 75 patients with osteoporosis with and without vertebral compression fractures. Finally, we intend to determine the relationship of the trabecular plate density as predicted by T2* and bone strength by evaluating the relationship among trabecular microstructure, as evaluated by MR microscopy, T2* and mechanical load-bearing capacity on cadaver specimens of human vertebrae.
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