In vivo imaging of bone micro-architecture in mice with 3D synchrotron radiation micro-tomography

Micro-tomographic imaging of bone micro-architecture is increasingly used on wild and transgenic mice to follow effects of diseases or therapeutics. Synchrotron radiation micro-tomography (SR micro-CT) provides quantitative images at very high spatial resolution but has mainly been used in vitro. The aim of this work was to show the feasibility of SR micro-CT for assessing bone mineral density and micro-architecture in vivo in mice. Imaging with a pixel size of 10 μm was performed on beam line ID19 at the ESRF using a special mouse holder. Two strains of mice (C3H/HeJ and C57BL/6J) were used for the experiment. First tests were performed in order to optimize the imaging conditions with respect to dose. Then, six mice of each group were imaged at doses of 7 and 13 Gy (total scan time <5 min). A similar volume of interest was selected in each image to perform quantitative analysis. The first results on bone volume and mineralization revealed significant differences between the strains as expected. Although there was no apparent damage, the imaged femurs will be further investigated by histology to evaluate the effect of irradiation on bone cells. In conclusion, SR micro-CT provides in vivo images with high signal-to-noise ratio (SNR), very short scan time and may be used in longitudinal studies.