Synchrotron Radiation Micro-CT Imaging of Bone Tissue

Abstract

The evaluation of bone fragility remains an open question that is all the more important given that the prevalence of osteoporosis is increasing in industrial countries with the ageing of the population and its greater sedentarity. This disease, which affects one in three menopausal women, is responsible of fractures and vertebral compression that can lead to invalidity. Osteoporosis is a “silent disease”: 40% of women and 13% of men after 50 years old are concerned with and 24% of aged patients die one year after a hip fracture. Thus this disease represents a major cost for public health. The diagnosis of bone fragility and the associated therapeutic decision are currently based on the measurement of bone mineral density (BMD) using dual X-ray absorptiometry (DXA) techniques. However, although BMD is an important determinant of bone fragility, it doesn’t provide a sufficient prediction of fracture risk (estimated between 60% and 70%) and it appears necessary to develop new methods for bone strength evaluation. Bone quality changes that occur during aging and osteoporosis are receiving increasing interest. Among bone quality factors, the role of bone micro-architecture which refers essentially to the organization of the trabecular network has been widely demonstrated. The quantification of bone micro-architecture should make possible to improve the prediction of bone mechanical resistance. Although bone architecture was conventionally evaluated by histomorphometry, new non-destructive techniques derived from medical imaging are increasingly used for the assessment of bone tissue. In this chapter, we shall concentrate on X-ray imaging techniques, and in particular on 3D Xray microtomography (micro-CT) which is progressively supplanting standard histomorphometry for the analysis of bone micro-architecture. This technique is non destructive, avoids sample preparation and provides three-dimensional images with a high and isotropic spatial resolution in the three spatial directions. Using synchrotron radiation (SR) coupled to micro-CT instead of standard X-ray beams possesses additional advantages in terms of image quality and signal to noise ratio. Thanks to the properties of synchrotron radiation, this modality enables to study simultaneously bone microstructure and bone mineralization. As clinicians expect more than images, objective measures of bone architecture and quantification techniques based on these images have been developed. The availability of