Bone is an active organ that adapts its shape to the (mechanical) environment. The general mechanisms behind bone adaptation remain largely unknown. In this thesis a new imaging modality for bone research is introduced and used to investigate various aspects of bone adaptation. The topics in this thesis can be separated into two main themes. The first has a methodological nature wherein we developed a novel segmentation algorithm to separate bone from non-bone in micro-CT scans. Especially for in-vivo scanning this method outperforms traditional segmentation methods. Further, we investigated the use of image registration algorithms to superpose scan images of the same animal taken at different time points. Using these algorithms we were able to detect and track local changes in bone at the trabecular level. In the second part of this thesis we applied the above methodology to investigate the dynamics of bone loss that occur during aging and after ovariectomy in a rat model of post-menopausal bone loss. We concluded that the changes in bone after estrogen withdrawal are very dynamic and should not be characterized as mere bone loss. Further, the bone loss process after estrogen withdrawal resembled age related bone loss. Finally, we combined in-vivo micro-CT with finite element analysis and computer simulations of the remodeling process to investigate the relation between ovariectomy induced bone loss and mechanical signaling. We concluded that although mechanical loading of the bone appeared to drive adaptations of the trabecular structure, general bone loss was not related to mechanical loading.

bone adaptation, bone loss, estrogen, image registration, in-vivo micro-CT, osteoporosis, ovariectomy, rat, segmentation
H.H. Weinans (Harrie) , J.A.N. Verhaar (Jan)
Erasmus MC: University Medical Center Rotterdam
EU, NWO, N.V. Organon, Skyscan, Stichting Anna Fonds
978-90-6464-039-1
hdl.handle.net/1765/17333
Erasmus MC: University Medical Center Rotterdam

Waarsing, J.H. (2006, November 16). Exploring bone dynamics using in-vivo micro-CT imaging. Erasmus MC: University Medical Center Rotterdam. Retrieved from http://hdl.handle.net/1765/17333