In vivo trabecular thickness measurement in cancellous bones: longitudinal rat imaging studies

Using cross-sectional x-ray images taken with zoom-in micro computed tomography (micro-CT), we have measured trabecular thickness in the femoral bones of live rats. Since zoom-in micro-CT is capable of high-resolution imaging of a small local region inside a large subject, we were able to measure trabecular thickness in femoral bones without sacrificing the rats. To longitudinally observe the trabecular thickness change caused by ovariectomy-induced osteoporosis, we have taken zoom-in micro-CT images of 15 live Sprague-Dawley rats (group A: 5 ovariectomized rats fed with regular food; group B: 5 ovariectomized rats fed with calcium-deficient food; group C: 5 controls) every other week for 10 weeks. We have observed that the mean trabecular thickness in the femoral bones of groups A and B decreased monotonically down to about 10.7% and 15.5%, respectively, as compared to that of group C, within 12 weeks after the ovariectomy, while the mean trabecular thickness of group C increased about 12.7%. We expect that zoom-in micro-CT can be successfully used in osteoporosis studies in which longitudinal imaging studies are required.