DETAILED MULTIPLE-SCATTERING PROFILE EVALUATIONS IN COLLIMATED PHOTONSCATTERING TECHNIQUES

The spectra of gamma radiation, multiple-scattered by large volume sam ples, have been studied in different irradiation conditions and positi ons of the sensitive volume (SV) defined by the intersection of the in coming beam and the solid angle seen by a detector collimation. Monte Carlo simulations of up to third order scattering are performed on pha ntoms of small and large dimensions compared to the mean free path of the incoming photons, Qualitative and quantitative results are discuss ed in terms of both the equipment collimation and the peak integration limits of the recorded photon energy spectra. Experiments with 59.54 keV incident photons and water phantoms are reported in order to valid ate the simulation results. The experimental and simulated results cle arly show that the non-linear dependence of the multiple-scattered fra ction on the SV position inside the sample volume cannot be ignored in the assessment of Compton tomographic techniques.