A comparison between micro-CT and histology for the investigation of the cortical bone microstructure

In the last years there has been a great interest in cortical bone investigation. In fact cortical bone porosity is considered one of the main parameters which determines bone strength [3, 8]. Even if histology has been the gold standard for the morphometric examination of bone specimens, in the last ten years a new method arose: X-ray microtomography (micro-CT). It permits the non-destructive analyses of specimens in a faster way preserving the integrity of the samples [5] and the calculation of the morphometric parameters over the whole sample’s volume. Many studies showed the differences between these two techniques and tried to validate micro-CT system, but mostly for trabecular bone tissue [10]. Only few works showed comparisons between microtomographic images and histological sections of cortical bone specimens [1, 2, 3, 10]; but they lacked in a standardized binarization method and in a good spatial resolution (too close to the dimensions of Haversian canals). The key point in the analysis of micro-CT datasets is the binarization procedure, discriminating bone from non-bone and using an external method as a reference (histology) [7]. Moreover, it is not clear what effect the surrounding medium (air, saline solution, PMMA) has on the threshold value. Since the conventional histological examination requires an embedding treatment in PMMA, a study of the effect of this surrounding medium on structural parameters has to be performed also for the cortical bone tissue. For this reason, porosity derived from bone samples acquisitions in air and embedded in PMMA was compared. The aim of this work was to make a comparison between micro-CT scans of cortical bone specimens micro-CT scanned in air, and then scanned embedded in PMMA, using histological sections as reference. Then, once found the appropriate threshold value, structural parameters obtained from specimens acquired at the same micro-CT settings but surrounded by different media (air, PMMA) were compared.