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

Synchrotron radiation μCT (SR μCT) may provide three-dimensional (3-D) images with spatial resolution as high as 1 μm. The SR μCT system developed at the European Synchrotron Radiation Facility was already used to quantify trabecular bone architecture in bone samples. Here, the authors propose for the first time to use SR μCT to assess the mineral content in bones. This quantification is possible thanks to the monochromaticity and high photon flux of the X-ray beam extracted from synchrotron radiation. For this purpose, the authors relate the reconstructed gray levels of the images to a degree of mineralization in bone. They propose a calibration method to estimate the 3-D distribution of hydroxyapatite concentrations within the sample. This method is compared to a reference microradiography technique. Finally, the authors illustrate the possibilities of the method on 3-D images of human biopsies from osteoporotic patients before and after a treatment with bisphosphonates