Coherent X-ray scatter imaging and its applications in biomedical science and industry

Coherent x-ray scatter (CXRS) imaging refers to the spatially-resolved measurement of the coherent scatter cross-section in localised volume elements ("voxels") of an extended object. Following a historical introduction to the subject of CXRS, an account is given of the physical principles on which it is based, Representative coherent scatter plots of materials of interest in medical and industrial applications ape presented. Several alternative measurement configurations based on angular-dispersive and energy-dispersive x-ray diffraction are described and reasons are discussed which have lead to the adoption of the latter in the bulk of published CXRS investigations. The coherent scatter signal is subject to various degrading effects, such as self-attenuation of the primary and scatter radiations within the object, multiple scatter and statistical (photon) noise. These effects are described and data processing procedures to account for them in order to derive useful quantitative are illustrated. The design of a CXRS device ("RayScan") in use at the Philips Research Labs is discussed in some detail and representative results obtained with it are presented. The utility of coherent scatter imaging is demonstrated with examples drawn from the fields of tissue characterization in the medical environment, explosives detection for airport security screening purposes and the detection of narcotics. (C) 1999 Elsevier Science Ltd. All rights reserved.