A study of photon induced nuclear reactions and their applications using a medical betatron.

High energy electron accelerators installed in hospitals to provide routine electron and X-ray therapy have potential uses outside the field of radiotherapy that can have important applications. The electron energy is often higher than photo-nuclear reaction thresholds, which allows applications such as photon activation analysis, neutron production and isotope production to be considered. The 34 MeV Betatron at St. Luke's Hospital in Guildford has been used as a source of high energy electrons to study a wide range of uses of photonuclear reactions. The area of interest of most importance to this work is the detection and measurement of photon induced activity occurring in bulk elements in tissue. Patients receiving therapy doses of high energy electrons have induced activity within the irradiation site at the end of the treatment. This information, usually discarded in the normal course of treatment, allows quantitative determination of the concentration of Carbon, Nitrogen and Oxygen within the treatment field. The purpose of this study was to assess the accuracy of such determinations to see if small variations in the concentration of these elements can be detected. A gamma camera was used to monitor the physical distribution of these elements within a phantom. Three other areas of interest were explored: 1. The concentration of Nitrogen within the body, which can be correlated with body protein content, was measured in phantoms using low doses of 16 MeV bremsstrahlung. This important measurement, used in a variety of diseases associated with protein loss, is so far limited to hospitals with a neutron source available. 2. Neutron sources have a wide range of applications in the hospital, such as in-vivo and in-vitro activation analysis and neutron therapy. A neutron flux suitable for in-vitro activation analysis was obtained using 34 MeV electrons impinging on a Lead target. High gamma dose rates behind the target made the flux unsuitable for in-vivo applications. 3. Detection limits were obtained for the measurement of elements of biological interest using in-vitro photon activation analysis