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  • 1
    Publication Date: 2010-09-25
    Description: X-ray tomography is an invaluable tool in biomedical imaging. It can deliver the three-dimensional internal structure of entire organisms as well as that of single cells, and even gives access to quantitative information, crucially important both for medical applications and for basic research. Most frequently such information is based on X-ray attenuation. Phase contrast is sometimes used for improved visibility but remains significantly harder to quantify. Here we describe an X-ray computed tomography technique that generates quantitative high-contrast three-dimensional electron density maps from phase contrast information without reverting to assumptions of a weak phase object or negligible absorption. This method uses a ptychographic coherent imaging approach to record tomographic data sets, exploiting both the high penetration power of hard X-rays and the high sensitivity of lensless imaging. As an example, we present images of a bone sample in which structures on the 100 nm length scale such as the osteocyte lacunae and the interconnective canalicular network are clearly resolved. The recovered electron density map provides a contrast high enough to estimate nanoscale bone density variations of less than one per cent. We expect this high-resolution tomography technique to provide invaluable information for both the life and materials sciences.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dierolf, Martin -- Menzel, Andreas -- Thibault, Pierre -- Schneider, Philipp -- Kewish, Cameron M -- Wepf, Roger -- Bunk, Oliver -- Pfeiffer, Franz -- England -- Nature. 2010 Sep 23;467(7314):436-9. doi: 10.1038/nature09419.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics (E17), Technische Universitat Munchen, 85748 Garching, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20864997" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bone Density ; Bone and Bones/*cytology/*radiography ; Femur/cytology/radiography ; Imaging, Three-Dimensional/methods ; Mice ; Mice, Inbred C57BL ; Microscopy/*methods ; Nanotechnology/*methods ; Tomography, X-Ray Computed/*methods
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2015-11-20
    Description: The mechanical properties of many materials are based on the macroscopic arrangement and orientation of their nanostructure. This nanostructure can be ordered over a range of length scales. In biology, the principle of hierarchical ordering is often used to maximize functionality, such as strength and robustness of the material, while minimizing weight and energy cost. Methods for nanoscale imaging provide direct visual access to the ultrastructure (nanoscale structure that is too small to be imaged using light microscopy), but the field of view is limited and does not easily allow a full correlative study of changes in the ultrastructure over a macroscopic sample. Other methods of probing ultrastructure ordering, such as small-angle scattering of X-rays or neutrons, can be applied to macroscopic samples; however, these scattering methods remain constrained to two-dimensional specimens or to isotropically oriented ultrastructures. These constraints limit the use of these methods for studying nanostructures with more complex orientation patterns, which are abundant in nature and materials science. Here, we introduce an imaging method that combines small-angle scattering with tensor tomography to probe nanoscale structures in three-dimensional macroscopic samples in a non-destructive way. We demonstrate the method by measuring the main orientation and the degree of orientation of nanoscale mineralized collagen fibrils in a human trabecula bone sample with a spatial resolution of 25 micrometres. Symmetries within the sample, such as the cylindrical symmetry commonly observed for mineralized collagen fibrils in bone, allow for tractable sampling requirements and numerical efficiency. Small-angle scattering tensor tomography is applicable to both biological and materials science specimens, and may be useful for understanding and characterizing smart or bio-inspired materials. Moreover, because the method is non-destructive, it is appropriate for in situ measurements and allows, for example, the role of ultrastructure in the mechanical response of a biological tissue or manufactured material to be studied.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liebi, Marianne -- Georgiadis, Marios -- Menzel, Andreas -- Schneider, Philipp -- Kohlbrecher, Joachim -- Bunk, Oliver -- Guizar-Sicairos, Manuel -- England -- Nature. 2015 Nov 19;527(7578):349-52. doi: 10.1038/nature16056.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Paul Scherrer Institut, 5232 Villigen PSI, Switzerland. ; Institute for Biomechanics, ETH Zurich, 8093 Zurich, Switzerland. ; Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26581291" target="_blank"〉PubMed〈/a〉
    Keywords: Aged ; Collagen/ultrastructure ; Humans ; Imaging, Three-Dimensional/methods ; Male ; Nanostructures/*ultrastructure ; *Scattering, Small Angle ; Spine/ultrastructure ; Tomography/*methods ; X-Ray Diffraction
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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