Driving the field of micro computed tomography toward more quantitative, rather than qualitative, approaches, we here present a new evaluation method, which uses the unique linear relationship between gray values and x-ray attenuation coefficients, together with the energy-dependence of the latter, to identify (i) the average x-ray energy used in the CT device, (ii) the x-ray attenuation coefficients, and (iii), via the x-ray attenuation average rule, the intravoxel composition, i.e., the microporosity, which, amongst others, governs the voxel-specific mechanical properties, such as stiffness and strength. The method is realized for six 3D tricalcium phosphate scaffolds, seeded with pre-osteoblastic cells and differentiated for 3, 6, and 8 weeks, respectively. The corresponding voxel-specific microporosities turn out to increase during the culturing period (resulting in reduced elastic properties, as determined from micromechanical considerations), while the overall macroporosity remains constant. The new methods are expected to further foster the development of a rationally based and computer-aided design of biomaterials and tissue engineering scaffolds.