X-ray scatter tomography for explosives detection

An account is given of three explosive detection techniques based on X-ray scatter tomography i.e. coherent scatter computed tomography, energy-dispersive X-ray diffraction tomography and Compton back-scatter imaging. Following an introduction to the physics of the underlying X-ray interaction phenomena, the principles on which these image-forming techniques are based are elaborated. A brief description is given of some of the parameters relevant to the X-ray scatter system design and of the optimisation of these parameters for the target application. Signal degradation owing to self- attenuation of the primary and scatter radiations and multiple scattering is discussed and procedures to correct for these effects are presented. The above techniques have been applied to the problem of identifying and detecting explosive material in airport baggage and buried land mines. Decision criteria needed to limit the number of "false alarms" are discussed. Representative results drawn from the fields of baggage inspection and mine clearance are given. (C) 2004 Elsevier Ltd. All rights reserved.