Abstract
Since the first introduction of reconstructive tomography in medicine more than a decade ago, research into this technique has continued to arrest the interest of a growing number of scientists especially in the area of industrial non-destructive testing. It is thus an advantage for a laboratory to have a test rig that combines the various Imaging modalities using ionising radiations. Such a test rig has been designed and built around a BBC-B microcomputer complete with its own display system. It combines the ability for transmission and emission tomography with a capability for Compton scattering imaging. Imaging characteristics of the rig including the detectors efficiency, response, collimating systems line spread functions, resolution and the modulation transfer functions are determined. A model has been established to numerically calculate accurately the scattering volume and predict the scattering field at any scattering angle for bore-hole type of collimation. Images of aluminium phantom with lead and brass inclusions have been used to demonstrate the particular suitability of the Compton scattering technique for detecting dense materials within a low density medium. The use of an attenuation correction method for the scattered photons has proved very successful in improving contrast and signal-to-noise ratio of the images. None of the established imaging methods has proved capable of elemental distribution analysis and the methods used in elemental analysis lack the spatial information provided in imaging. A new and novel method is presented in this work that combines the elemental capability of neutron activation analysis with the spatial information of emission tomography. This method has been termed neutron induced gamma-ray emission tomography (NIGET). NIGET images obtained of a freeze-dried water pellet, a piece of human tibia and a study of the diffusion of a preservative solution in a sample of Scots-pine, have been used to demonstrate the potentials of this method.