BONE QUALITY SEMINARS: ULTRASTRUCTURE Investigation of bone with synchrotron radiation imaging: from micro to nano F. Peyrin Published online: 2 April 2009 # International Osteoporosis Foundation and National Osteoporosis Foundation 2009 Introduction Bone achieves several functions in the organism and exhibits different levels of organization. At the micro- structural scale, it is possible to distinguish cortical and cancellous bone being, respectively, a dense external shell and a porous inner material made of thin trabeculae (hundred of micrometers). If the general organization of these microstructures is well described in an anatomy handbook, their particular organization for a given bone may vary with aging, disease, or therapy. At the ultra- structural scale, bone tissue can be seen as an arrangement of bone modeling units (BMU) with different degrees of mineralization, including micrometric or submicrometric porosities such as micro-cracks, osteocyte lacunae, and canalicules. The composition of bone tissue itself is a mixture of collagen (mainly collagen type I), water and mineral (carbonated hydroxyapatite (HA)). The collagen and mineral phases are complementary in the sense that they respectively provide toughness and stiffness. The possible molecular composition of mineral may differ from stochiometric HA with the substitution of some ions. At the nanometric scale, the mineral particles are supposed to be platelets oriented along the main direction of the collagen fibrils. The main particularity of bone as a material is to be able to adapt itself to mechanical constraints. This adaptation is the result of complex biological processes which are not fully elucidated but which results in modifications at all levels, from the arrangement of mineralized particles to that of its micro and macro structure. Among the different means of investigating bone, imaging techniques may provide various types of informa- tion at different scales. While spatial resolutions between 5–10μm are appropriate to study bone microstructure, a submicrometric resolution is necessary to examine the ultra-structural level and a nanometric resolution is required to get information about the crystalline structure. For this purpose, synchrotron radiation which provides a source of light with brilliance several orders of magnitude higher than conventional sources possesses attractive properties to implement various imaging or mapping techniques at different scales. In this paper, we shall review applications of synchrotron radiation techniques for the investigation of bone tissue. After briefly recalling the principle of synchrotron radia- tion, we describe X-ray computerized microtomography (micro-CT), X-ray or infrared (IR) spectrometric techniques and diffraction-based techniques. Although it will not be possible to make an exhaustive review on this broad topic, we will highlight the interest of using synchrotron radiation and some recent applications. Osteoporos Int (2009) 20:1057–1063 DOI 10.1007/s00198-009-0855-8 Data presented at the Third Meeting on Bone Quality, France, 24–25 June 2008: Bone Ultrastructure. F. Peyrin INSERM U630, CREATIS-LRMN; CNRS UMR 5220; INSA-Lyon, F-69621 Lyon, Villeurbanne, France F. Peyrin (*) Université de Lyon, F-69622 Lyon, Villeurbanne, France e-mail: peyrin@esrf.fr F. Peyrin ESRF, BP 220, 38043 Grenoble Cedex, France