Inelastic photon scattering: Effects and applications in biomedical science and industry

Compton scattering is widely used to analyse electron momentum distributions in solid state systems. Perhaps less well-known is its role as the major cause of image contrast in medical and industrial radiography. This article discusses the principles and applications of a technique, known as Compton scatter imaging (CSI), which is based on direct registration of the Compton scatter radiation. Following a historical survey of the major developments in this field, the strengths and weaknesses of transmission radiography and Compton scatter imaging are compared in order to determine those measurement situations to which the latter is best suited. A description is given of several disturbing effects to which CSI is prone and ways in which these may be accounted for to yield quantitative density data are presented. The most important types of imaging system based on Compton scatter are discussed and compared. The ComScan (an acronym for Compton scatter scanner) is a commercially-available backscatter imaging system which is discusssed here in some detail. ComScan images taken from applications of topical and historical interest are presented. (C) 1997 Elsevier Science Ltd.