Application of Micro-CT and MRI in Clinical and Preclinical Studies of Osteoporosis and Related Disorders

Advanced imaging techniques, which are noninvasive and nondestructive, can provide structural information about bone beyond simple bone densitometry. As the mechanical competence of trabecular bone is a function of its apparent density and 3D distribution, assessment of 3D trabecular structural characteristics may improve our ability to understand the pathophysiology of osteoporosis, to test the efficacy of pharmaceutical intervention, and to estimate bone biomechanical properties. We studied ovariectomy-induced osteopenia in rats with various treatments. Micro-CT is also useful for studying osteoporosis in mice and phenotypes of mice with gene manipulation. Micro-CT can quantify osteogenesis in mouse Ilizarov leg-lengthening procedures, osteoconduction in rat cranial defect models, and structural changes in arthritic rabbits, rats, and mice. Micro-CT can reproducibly quantify 3D microarchitecture of new bone formation inside the pores of titanium prosthesis implants is rabbits. In clinical studies, we evaluated longitudinal changes in iliac crests in premenopausal and postmenopausal women. Paired bone biopsies from post-menopausal women with osteoporotic fracture shows that 3D trabecular microstructure deteriorates in the iliac crest of postmenopausal osteoporotic women without active treatment. Three-dimensional microstructural parameters can predict fracture. Treatment of PTH in postmenopausal women with osteoporosis significantly improved trabecular morphology with a shift toward a more plate-like structure, increased trabecular connectivity, and increased cortical thickness. Paired bone biopsy specimens from the iliac crest in postmenopausal women with osteoporosis before and after beginning estrogen replacement therapy demonstrated in post-treatment biopsies a significant change in the ratio of plates to rods. High-resolution MR and µMR have received considerable attention both as research tools and potential clinical tools for assessment of osteoporosis. It has been used in studying human specimens or animal models of osteoporosis with various treatment strategies.