Production of AC-225 for cancer therapy by photon induced transmutation of RA-226

Abstract

Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. The reduction of radium by photonuclear transmutation by bombarding Ra-226 with high-energy photons from a medical linac has been investigated. The irradiated needles would then be processed to remove the Ac-225, which can then be used for .Targeted Alpha Therapy. (TAT) of cancer. This project has the potential to slowly reduce obsolete radioactive material, and displace future expensive importation of Ac-225 from Russia, Germany (Institute for Transuranium Elements - ITU) and the US in the years ahead. This thesis progresses through a number of stages and begins by providing a background to the usefulness of Ac-225 as an alpha emitter, some of the equipment used in the experimental work such as linear accelerators and detectors, as well as the initialisation of a process whereby a reliable source of high-grade radium is secured, suitable equipment obtained, followed by a series of experiments leading to the production of the desired product, actinium and bismuth. The second stage of this study involved the formulation of a theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra- 226. This enabled the total integrated yield of Ra-225 and its daughter product Ac-225 to be obtained. The third stage of this study ties the theoretical and experimental work together by presenting the results of a number of experiments performed on radium sources. These experiments were performed over a period of about three years using a variety of detectors in a hospital setting. These experiments, as presented in this thesis, demonstrate that Ac-225 can be produced in small quantities by a medical linac or in commercial quantities by the use of a high-powered linac or cyclotron, thereby, ensuring a reliable supply of Ra-225 for TAT and also reducing the radium waste product.

Date of Award	2007
Original language	English