S Ynchrotron Based X -ray Scatter Ing : Techn Iques for the B Iomed Ical Sc I Ences

X-ray scattering is well established for probing the structure of matter at the atomic level in the materials sciences. In particular, coherent X-ray scattering (X-ray diffraction) has developed to become an indispensable tool for crystal structure determination. The level of technological advancement is such that, coupled with the high fluxes offered by synchrotron sources, a high degree of automation in the data collection process is possible. In the biomedical sciences, X-ray diffraction techniques are now essential to the characterisation of macromolecules in growth areas such as structural genomics. The demand for such structural characterisation techniques across all areas of contemporary science is amply demonstrated by the fact that of the 13 beamlines envisaged for the first stage of the Australian Synchrotron, 5 will be dedicated to various diffraction techniques. In contrast, X-ray scattering is usually regarded as a problem for radiographic imaging, where it is considered to be a major contributor to reduced image quality. The familiar X-radiograph relies on the differential absorption of X-rays by materials of varying densities, and considerable effort is directed towards minimising X-ray scatter during image acquisition and the subsequent correction of its effects. However, it is readily apparent to diffraction specialists that this scattered radiation must contain considerable information about the sample. It is only relatively recently that the increased availability of synchrotron sources for imaging applications has permitted these apparently disparate approaches to Xray scattering to be united. These techniques are able to utilise scattered radiation to provide novel imaging methods that are able to substantially increase image contrast or provide material specific analysis.