226 H. Zeng
propagation. 3D (volume) information on the sample structure can be obtained by
using computer reconstruction algorithms. 3D renderings of obtained data after
reconstruction are then made by electronically stacking up the slices. Quantitative
architectural parameters from the tomographic images can then be extracted.
MicroCT has become a powerful tool for biomaterials research. It is a non-
destructive and noninvasive procedure and suitable for in vivo applications. For
example, a few recent studies have looked into the imaging and quantification of
scaffold-bone interactions in vivo.
5,8,9
Direct μCT-based image analysis allows to
accurately quantify scaffold porosity, surface area, and 3D measures such as pore
size, pore distribution, and strut thickness.
10
Furthermore, it allows for a precise
measurement of bone growth into the scaffold and onto its surface (Fig. 10.1).
4
This methodology is useful for quality control of scaffold fabrication processes, to
assess scaffold degradation kinetics, and to assess bone tissue response.
10.2.2 X-ray Microdiffraction Technique
X-ray diffraction is the most commonly used technique for studying the 3-D
structures of solid materials. Its spatial resolution is limited by the X-ray beam
cross-section. In X-ray microdiffraction technique, x-rays are focused to a spot
size of one micron or less to perform x-ray diffraction experiments with very
high spatial resolution. X-ray microdiffraction is providing new insights in the
fields of materials science.
4
Materials properties such as strength and fatigue
resistance are highly dependent on microstructure. X-ray microdiffraction can
measure local variations in stress, orientation, and plastic deformation between
grains and within individual grains, helping us understand mechanical properties
Figure 10.1. 3D microCT image of hydroxyapatite scaffold (Engipore) loaded with sheep
BMSC and implanted in an immunodeficient mouse, showing newly formed bone (green)
onto the inner surface of the scaffold (yellow and red); the organic phase is blue. With
permission from.
4
For color reference, see page 275.
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