Submitted on April 29, 2005
Accepted on August 29, 2005
Monochromatic synchrotron radiation µCT reveals disuse-mediated canal network rarefaction in cortical bone of growing rat tibiae
Takeshi Matsumoto1*, Masayuki Yoshino1, Takahisa Asano2, Kentaro Uesugi3, Masahiro Todoh4, and Masao Tanaka1
1 Division of Bioengineering, Osaka University Graduate School of Engineering Science, Toyonaka, Osaka, Japan
2 Department of Nuclear Medicine, Kawasaki Medical School, Kurashiki, Okayama, Japan
3 Japan Synchrotron Radiation Research Institute, Kouto, Hyogo, Japan
4 Division of Mechanical Science, Hokkaido University Graduate School of Engineering, Sapporo, Hokkaido, Japan
* To whom correspondence should be addressed. E-mail: matsu{at}me.es.osaka-u.ac.jp.
The purpose of this study was to demonstrate the ability of computed microtomography based on monochromatic synchrotron radiation (SRµCT) in microstructural analysis of cortical bone. Tibial diaphyses of growing rats (14 weeks, n=8) undergoing unilateral sciatic neurectomy 8 weeks prior to study were imaged with spatial volume resolution of 5.83x5.83x5.83 µm3 by SRµCT (20 keV) at the synchrotron radiation facility (SPring-8). Reconstructed image data were translated into local mineral densities using a calibrated linear relationship between linear absorption coefficients and concentrations of homogeneous K2HPO4 solution. Pure bone 3D images, produced by simple thresholding at a bone mineral density of 0.82 g/cm3, were analyzed for macro- and microscopic structural properties. In neurectomized legs, cortical canal network rarefaction as well as bone atrophy were found. The former was characterized representatively by 30% smaller porosity, 11% smaller canal density in transverse section, and 38% smaller canal connectivity density than those in contralateral bone. On the other hand, no difference was found in bone mineral density between neurectomized and intact legs (1.37 vs. 1.36 g/cm3). In conclusion, SRµCT is a promising method for 3D analysis of cortical microstructure and the degree of mineralization in small animals.
