Assessment of bone mineral content from 3-D synchrotron radiation microtomography images

Synchrotron radiation mu CT (SR mu CT) may provide three-dimensional (3-D) images with spatial resolution as high as I pm. The SR mu CT system develop ed at the European Synchrotron Radiation Facility was already used to quant ify trabecular bone architecture in bone samples. In this paper, we propose for the first time to use SR mu CT to assess the mineral content in bones. This quantification is possible thanks to the monochromaticity and high ph oton flux of the X-ray beam extracted from synchrotron radiation. For this purpose, we relate the reconstructed gray levels of the images to a degree of mineralization in bone. We propose a calibration method to estimate the 3-D distribution of Hydroxy Apatite concentrations within the sample. This method is compared to a reference microradiography technique. Finally, we i llustrate the possibilities of the method on 3-D images of human biopsies f rom osteoporotic patients before and after a treatment with bisphosphonates .