IBP Network Webinar: Prof Stuart Stock - Non-invasive, 3D x-ray diffraction mapping of mineralized tissue at scales from tens of centimeters to hundreds of nanometers
Date: 16 June 2021 Time: 15:00 - 16:00
Mineralized tissue achieves remarkable properties using a hierarchy of structures spanning centimeter to nanometer scales. Functional requirements and evolution produced various tissue types with very different hierarchies, and, although many of these nano- and microstructural levels have been described, critical quantitative information is often lacking within a single level and between adjacent scales. This presentation focuses on what position-resolved synchrotron x-ray diffraction mapping has told us about several tissues and their structures. In some cases, tissue could be sectioned for 2D mapping; in others, non-invasive 3D interrogation was performed due to the requirement that the specimen not be damaged.
The first example is CT-guided, 3D noninvasive diffraction analysis of the contents of an Egyptian mummy. At a smaller size scale, lattice parameter, crystallite size and small angle scattering analyses were performed on intact archeological human metacarpal bones; the emphasis here is not mapping but extraction of accurate quantities from specimens with very irregular cross-sections. In the third example, thick sections, diffraction mapping and Rietveld refinement provided an accurate assessment of lattice parameter variation across growth bands of the continuously growing whale teeth and beaver incisors. At the smallest size scale covered in this talk, the ordering of crystallites within tooth enamel rods are investigated with a sub-micrometer diameter x-ray beam and a one micrometer thick section.
Examples of x-ray diffraction mapping of every volume element (voxel) within a specimen’s cross-section conclude the presentation. The studies described above used monochromatic synchrotron x-rays, and tomographic reconstruction with diffraction of monochromatic x-rays revealed the variation of crystallographic texture between cortical and trabecular bone in vertebral bone. Energy dispersive diffraction mapping using polychromatic x-rays is an alternative approach, and 3D mapping of the mineralized cartilage of intact shark vertebrae brings us back to mapping nanoscale quantities such as lattice parameter and crystallographic texture over centimeter-sized specimens.
About the speaker:
Dr. Stock is Research Professor at Northwestern University’s Feinberg School of Medicine since 2001 and is a member of its Simpson Querrey Institute. Before that he was Professor of Material Sci. and Eng., Georgia Institute of Technology. He has used microComputed Tomography actively since 1985 and wrote MicroComputed Tomography: Methodology and Applications, 2nd Ed., Taylor and Francis, 2019. He has also employed x-ray diffraction since 1977 and coauthored Elements of X-ray Diffraction, 3rd Ed., Prentice-Hall, 2001. Since 2001, his research has focused on mineralized tissue of echinoderms and of many species of vertebrates, specifically the 3D organization of biomineralized tissue.
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- 30 – 45 minutes talk followed by 5-15 minutes Q&A.
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