Mid Term Review

Applications of beta particles In Medicine

Mr David Stevens

Beta particles are a component of emissions during radioactive decay of certain radioisotopes. Beta particles are either of two types: Beta-minus particles are emitted as high energy electrons when a nuclear neutron decays into a proton and Beta-plus particles are emitted as high energy positrons when a proton decays into a neutron. Positrons are an anti-matter particle. Since their postulation by Paul Dirac (1928) and discovery by Carl David Anderson (1932), positrons have captured the imagination of, and garnered applications by physicists.

One of the more valuable applications of positrons is in positron emission tomography (PET), wherein the annihilation of positrons and electrons in-vivo has allowed advances in the diagnosis and treatment of cancer. The present research endeavours to build upon the library of positron / molecule scattering data which has enabled accurate scattering models to evolve, which attempt to reflect reality during PET. A comprehensive set of measurements have been performed on pyrazine and further targets are proposed, including thymine.

Our apparatus only permits the analysis of scattering behaviour in an atomic or molecular vapour phase. Liquid phase targets pose a number of challenges, some of which are also investigated. I will present the progress towards the construction of a suitable liquid target mechanism which can be used in conjunction with a positron beamline system where positrons pass into atmosphere through a thin silicon nitride window. Such an apparatus is available at the National Institute of Advanced Industrial Science and Technology (AIST) at Tsukuba in Japan. I will also describe the method by which the data so obtained can reveal positron depth penetration information and characteristics.

On the other hand, in recent decades, beta-minus particles have been effective in the direct treatment of certain types of tumors via brachytherapy. The final aspect of the present research investigates the possibility of programming the energy of beta-minus particles in-vivo such that the extent of the treatment zone is limited to the tumor, rather than extending into healthy tissue. I will describe the work to date involving the production of sub-micron particles comprised of a beta emitter bound to a heavy metal and the proposed work to encapsulate such particles within amino acid shells to facilitate targeting specific biological sites in-vivo.

Date & time

Wed 24 Aug 2022, 3–4pm



NPAA Seminar Room


Members of RSPE welcome