Bone step-wedge (center) made of 10 cortical bone steps of decreasing thickness (left to right) on a standardized hoof block and Al wedge (right), from a digital radiograph taken at 60 kV, 0.08 seconds, and 15 mA. ROIs (red) were selected for measuring Al BDI (right) and bone BDI (left) from the tenth and thickest step of the bone step-wedge.