Papers by Author: Shuo Zou

Abstract: Dense and porous HA and Si-HA discs and granules with varying percentages of silicon substitution have been produced and physically and chemically characterised using scanning electron microscopy, surface area analysis, porosimetry, density measurement, image analysis, Xray diffraction, X-ray fluorescence, FT-infrared spectroscopy and in-vitro and in-vivo testing. Results have shown that cell adhesion in-vitro and bone apposition in-vivo are enhanced by the presence of silicon substitution in the hydroxyapatite structure. The biological response to the materials appears to indicate an optimum outcome for levels of silicon substitution of 0.8wt%.

Abstract: Computerized X-ray microtomography (micro CT) is a powerful technique for imaging and quantification in biomedical materials research. Mapping of various tissue/implants in 3-dimension, which is not achievable with traditional histological slices, is particularly desirable in ex-vivo implant analysis. However, due to a variety of artifacts during image formation, especially the blurred interfaces due to the machine contrast transfer function and the partial volume effect, quantification based on traditional histograms is not accurate. In this work we propose a new 2-dimensional histogram and its application in the analysis of micro CT data of ex-vivo implants, which significantly improve the clarity of the definition of different phases and drastically reduced the artifacts of segmentation compared to conventional methods.

Abstract: Computerized X-ray micro tomography (micro CT) is a powerful technique for studying the structure and properties of porous scaffold. A variety of sample parameters can be studied using a single micro CT scan [1]. In general a segmented data set is a required for most quantitative analysis. However, segmentation of CT data can be difficult due to the artifacts in micro CT images such as blurred interfaces due to the machine contrast transfer function and the partial volume effect. Therefore the segmentation can be biased and prone to errors. Many methods have been developed to improve segmentation, however the interface problem has not been solved perfectly [2]. Porous scaffolds suffer from these effects because of their high surface to volume ratio and hence large interface. In this paper we discuss the interface problem in detail and demonstrate the effect of voxel size on the histograms of CT images of porous scaffold as well as a thresholding method based on 2 dimensional histogram is also presented. The potential of this method in more complicated scenarios such as 3-phase system is currently being investigated [3].

Abstract: Silicon-substituted hydroxyapatite (SiHA) attracts particular interest due its enhanced bioactivity compared with pure hydroxyapatite. In this study we seek to clarify the effects on the lattice parameters of both composition and sintering temperature in experimentally-produced HA and 0.8wt% SiHA, 1.5wt% SiHA and 2.0wt% SiHA sintered at 800oC and 1200oC. X ray diffraction was used to determine the phase purity and crystallographic structure. We found that while the c parameter increased with increasing silicon concentration, the a parameter decreased with initial silicon incorporation then recovered with further increases in silicon incorporation. The calcium (2) channel expanded with silicon incorporation while tetrahedron distortion index (TDI) and the radius of the P channel showed a similar dependence on silicon content as the a parameter.