MR spectroscopy and micro-CT in evaluation of osteoporosis model in rabbits: comparison with histopathology.

ABSTRACT

PURPOSE: To explore the evidence of regular alteration of bone quality in osteoporosis dynamically examined by MRS and micro-CT, comparing with histopathology. METHODS: Forty rabbits were allocated into two groups. Group A were used as sham. Group B underwent bilateral ovariectomy (OVX) combined with daily intramuscular methylprednisolone, underwent MR spectroscopy, micro-CT, and histopathology of L5 at 2, 4, 8, and 10 weeks after operation. RESULTS: Fat fraction as shown by MRS in Group B was significantly increased over the time course of osteoporosis development with significant difference between two groups at 4, 8, and 10 weeks after OVX. Continuous deterioration of cancellous bone architecture in Group B, was first detected at week 4. FF value in group B correlated with micro-CT parameters. Marrow fat as measured by MR and CT was positively correlated with both the mean density and diameter of adipocytes (both of which increased over time). CONCLUSIONS: Marrow adipogenesis occurs in synchrony with deterioration of trabecular microarchitecture.MRS may be valuable to assess the pathophysiological changes of bone marrow in osteoporosis in early stage. KEY POINTS MRS revealed gradually increasing bone marrow fat in rabbits rendered osteoporotic. Marrow adipogenesis occurs in synchrony with deterioration of trabecular microarchitecture. Pathology revealed an early increase in number of marrow adipocytes in osteoporosis. MRS may help assess early pathophysiological bone marrow changes in osteoporosis.