High resolution x-ray: a reliable approach for quantifying osteoporosis in a rodent model

Osteoporosis is the most common metabolic disease of bone, resulting in significant worldwide morbidity. Currently, there are insufficient imaging modalities available to evaluate osteoporotic bones in small animal models. Here, we demonstrate the feasibility of using high resolution X-ray imaging as a comparable measure of bone degeneration to dual-energy X-ray absorptiometry (DXA) in an osteoporosis rodent model. At week 0, animals underwent either an ovariectomy (OVX) or sham procedure (SHAM). DXA analysis was performed weekly to confirm and compare the bone degenerative changes induced by OVX. A comparison using high resolution X-ray imaging (Faxitron(®)) was then performed postmortem due to need of soft tissue removal. Two regions of interest (ROIs) were utilized: the distal third of the femur and the lumbar spine (L4/L5). It was observed that SHAM animals maintained a relatively constant bone mineral density (BMD), in comparison to OVX animals, whereby a significant decrease in BMD was appreciated. Post mortem X-ray scans were performed and converted to 8-bit color and quantified. A high level of agreement with DXA quantifications was observed with X-ray quantifications, and a significant correlation between the radiopacity, visualized by color distributions, and the DXA BMD values between animal groups was evident. Our study demonstrates the applicability of high resolution X-ray imaging both qualitatively and quantitatively as a reliable approach for quantifying osteoporosis in rodent osteoporotic models. With DXA being a highly user dependent modality, our technique is a unique secondary methodology to verify DXA findings and minimize inter-observer variability.