Rayleigh to Compton ratio computed tomography using synchrotron radiation

The detection of X-ray photons scattered through a sample by the Rayleigh a nd Compton processes is used to perform tomographic images. In the present paper, we describe a new experimental arrangement and the corresponding rec onstruction method. The scanning method is similar to the one used for firs t generation tomographs. A standard reconstruction algorithm gives two inte rmediate images, corresponding to the Compton and Rayleigh contributions. Q uantitative comparisons are made with the aim to explain the difference of sensitivity between each scattering process. On both images artifacts are p resent, due to photon attenuation. Computing the ratio between those two im ages produces a map, free from artifacts, which represents the atomic numbe r Z. Differentiation between polyethylene and an aqueous solution containin g a low concentration of iodine (0.5 g l(-1)) is easily performed. The expe riments were carried out at the European Synchrotron Radiation Facility (ES RF), in Grenoble (France), on line ID15 B. As a result of the very high pho ton flux, short measurement times (about five seconds per point) are allowe d, as well as a good spatial resolution. The voxel size is 1 x 1 mm(2) in t he plane of the slice and 0.3 mm in the third direction. (C) 1999 Elsevier Science Ltd. An rights reserved.