Optimization of digital volume correlation computation in SR-microCT images of trabecular bone and bone-biomaterial systems

A micromechanical characterisation of biomaterials for bone tissue engineering is essential to understand the quality of the newly regenerated bone, enabling the improvement of tissue regeneration strategies. A combination of micro-computed tomography (microCT) in conjunction with in situ mechanical testing and digital volume correlation (DVC) has become a powerful technique to investigate the internal deformation of bone structure at a range of dimensional scales. However, in order to obtain accurate three-dimensional (3D) strain measurement at tissue level, high-resolution images must be acquired, and displacement/strain measurement uncertainties evaluated. The aim of this study was to optimise imaging parameters, image post-processing and DVC settings to enhance computation based on ‘zero-strain’ repeated high-resolution synchrotron microCT (SR-microCT) scans of trabecular bone and bone-biomaterial systems. Low exposures to SR X-ray radiation were required to minimize irradiation-induced tissue damage, resulting in the need of advanced 3D filters on the reconstructed images to reduce DVC-measured strain errors. Furthermore, the computation of strain values only in the hard phase (i.e. bone, biomaterial) allowed the exclusion of large artifacts localised in the bone marrow. This study demonstrated the suitability of a local DVC approach based on SR-microCT images to investigate the micromechanics of trabecular bone and bone-biomaterial composites at tissue level with a standard deviation of the errors in the region of 100 microstrain after a thorough optimisation of DVC computation.