 4. Quantitative computed tomography QCT allows for separate measurements in cortical and trabecular bone. Cortical bone will be evaluated at the proximal femur, and both BMD and geometry will be measured. In addition to parameters characterizing cortical bone, we will measure cancellous bone BMD and geometry. The methodology and the study parameters will vary according to the measurement site. When designing the investigation protocols, we sought the best trade-off between minimum radiation exposure and maximum image quality . 