Imaging Beyond Bone Mineral Density

Bone is a composite tissue comprised of organic and inorganic phases. It adapts itself to mechanical strains with an aim to maintain its mechanical competence via modelling and remodeling. Such adaptation of bone can result in alteration of material and structural properties including bone mineral density (BMD), microarchitecture, mineralization, and morphology. Quantitative bone imaging enables the evaluation of bone status in relation to diseases, mechanical and other interventions. However, bone quantity measurement of BMD using dual-energy X-Ray absorptiometry is limited because of its projection imaging approach and provides only a scalar measurement. As an anisotropic material, other bone quality including the architecture and spatial distribution of bone have to be considered in the evaluation of bone status. Also collagen fiber orientation and degree of mineralization in this composite tissue are important determinants of bone adaptation in response to treatment interventions. Thus, synergized use of multi-imaging modalities may decipher the interplay of material and structural properties in bone adaptation. Current imaging techniques using peripheral quantitative computed tomography, microcomputed tomography, magnetic resonance imaging, quantitative ultrasound and circularly polarized light microscopic imaging have gone beyond the measurement of bone quantity and to provide significant information of bone quality in the understanding of bone status. The present chapter aims to discuss the contribution of different imaging modalities in the evaluation of bone status.

Keywords: Bone Quantity, Bone Quality, Bone Strength, Imaging.