Advanced CT based in vivo methods for the assessment of bone density, structure, and strength.

Based on spiral 3D tomography a large variety of applications have been developed during the last decade to asses bone mineral density, bone macro and micro structure, and bone strength. Quantitative computed tomography (QCT) using clinical whole body scanners provides separate assessment of trabecular, cortical, and subcortical bone mineral density (BMD) and content (BMC) principally in the spine and hip, although the distal forearm can also be assessed. Further bone macrostructure, for example bone geometry or cortical thickness can be quantified. Special high resolution peripheral CT (hr-pQCT) devices have been introduced to measure bone microstructure for example the trabecular architecture or cortical porosity at the distal forearm or tibia. 3D CT is also the basis for finite element analysis (FEA) to determine bone strength. QCT, hr-pQCT, and FEM are increasingly used in research as well as in clinical trials to complement areal BMD measurements obtained by the standard densitometric technique of dual x-ray absorptiometry (DXA). This review explains technical developments and demonstrates how QCT based techniques advanced our understanding of bone biology.