Improving Hadron Therapy: Design of the Beam Transport System for a Biomedical Research Facility and PET Isotope Production

Recently there have been great advancements in the development of hadron therapy (HT)in Europe to treat cancer with external beam therapy. However, the relative superiority and especially cost effectiveness of HT over existing photon based forms of therapy have not yet been generally proven. Furthermore, the biological effect of particle radiation is a major source of uncertainty in HT. As a result there is a strong interest from the biomedical research community to have more access to clinically relevant beams. Unfortunately, beam time for pre-clinical studies is currently very limited and a new dedicated facility would allow extensive research into the radiobiological mechanisms of ion beam radiation. A very important tool in treatment planning in HT are Monte-Carlo simulations. These can also be used as a tool to improve beam delivery and explore dose deposition verification, one of the uncertainties in HT. This basic research would support the current clinical efforts of the new treatment centres in Europe (for example HIT in Heidelberg, CNAO in Pavia, and MedAustron in Vienna).

This thesis presents three research projects. The first part presents a feasibility study of an experimental biomedical facility based on the CERN Low Energy Ion Ring (LEIR) accelerator and suggests possible optics improvements to that design using MAD-X. This new facility would use CERN’s existing infrastructure and thus provide ion beams (from protons to neon ions) in a cost effective way with the aim of establishing an accessible facility to establish the development and implementation of best treatment practices. As low extraction scheme has been proposed for extracting ions from LEIR into the designed experimental beamline that separates into two horizontal beamlines suitable for clinical beam energies and a low-energy vertical beamline for radiobiological experiments. The first horizontal beamline and the vertical beamline are intended for biomedical experiments on cells and the second horizontal beamline is reserved for phantom work, (micro-)dosimetry and detector development.

The second part of the thesis utilizes the Monte-Carlo package Geant4 to explore the production of radioisotopes during proton bombardment in a phantom or patient at a proton therapy facility. The possibility of depth dose verification during proton therapy at the TRIUMF proton therapy centre treating ocular melanomas was explored. Currently, work has been done at TRIUMF to simulate the interactions of particle beams with a phantoms, using the Monte Carlo particle transport and interaction code FLUKA. However, due to the lack of reliable cross-section data for the relevant therapeutic energy range, there are great uncertainties about the isotope production, and consequently the axial isotope activity profile inside the phantom. Simulation programs Geant4 and FLUKA are being used to validate data from PET scans thus improving patient care through validation after each treatment fraction.

This technique has also been utilized in the third and final part of the thesis. It explores the production of PET isotopes on the TR13 cyclotron, a medical cyclotron at TRIUMF. Again, both Geant4 and FLUKA are used to compare to experimental yield measurements and to validate the Monte-Carlo simulations at these low proton energies.