Voxel-based density registration of trabecular bone: a longitudinal HR-pQCT study of postmenopausal women

Bone mineral density (BMD) is one of the important parameters used to characterise bone quality. Clinically, the only recommended method - dual X-ray absorptiometry - can only evaluate a two-dimensional areal BMD. Currently, three-dimensional localised BMD information is absent. HR-pQCT enables the assessments of 3D microstructure down to trabecular bone. Therefore, in this study, a voxel-based density registration (VDR) method is proposed to analyse the longitudinal changes of trabecular-bone density distribution. The VDR techniques were evaluated based on a six-month longitudinal study of five postmenopausal women. The time effect on localised changes of trabecular-bone mineral density was visualized and variations between different anatomical regions were quantified for the first time. Different distributions between anatomical regions were found in bone mineral density of trabecular bone (vBMD_trab), with a change of vBMD_trab at medial region (-0.56%) significantly higher than anterior (-1.58%) (p = 0.032). This study indicates that localised density changes might be used as a prior indicator for the effect of aging or other interventions.