Estimation of bone-mineral density from OCT images

Previously we have demonstrated by an integrating-sphere technique a useful correlation between bone mineral density (BMD) and the optical scattering coefficient (μs). We have used OCT to study this relationship, with a view to assessing its viability as an in vivo measure of BMD. We used an OCT system operating at 1.3 microns to image various bone samples and to make images in different directions. To investigate the accuracy of OCT measurements we collected averaged images taken at different sites along the shaft of a bone sample. A small (about 3%) variation in measured coefficients, justifies the possibility of using the OCT technique for this kind of measurement. Measurements of bone both with and without periosteum, showed essentially the same optical properties. Applying the incident light beam perpendicular and parallel to the main direction of the collagen fibers gave differences in scattering coefficient of about 40% that confirms our previous suggestion about anisotropy of bone matter. Images of bone samples for different demineralisation time were collected. They allowed following changes in calcium distribution in cortical part of bone with the increasing time of acid activity.