Computational techniques for studying the interactions of radiation with matter and applications in radiotherapy physics

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Radiotherapy is commonly used as a treatment for cancer. All forms of radiotherapy aim to maximize tumour cell kill while limiting healthy tissue radiation exposure. Despite the widespread application of radiotherapy to treat cancer, fundamental questions relating to the interactions of radiation with matter remain. Further, potential future treatment methods prompt new areas of investigation. This research program involves the development and application of sophisticated computer codes which employ the so-called 'Monte Carlo' (MC) method to model the passage of radiation through matter. These MC simulations can be used to compute dose, the energy deposited by radiation in tissue, as well as to study a wide array of questions relevant for radiotherapy treatments. An existing treatment to be considered is brachytherapy, in which radioactive sources are placed next to or inside a tumour (in, e.g., the prostate, breast, or eye). Widely-used dose calculation algorithms are inaccurate; a fast, accurate, and comprehensive MC dose calculation program is under development and will be used to study brachytherapy physics. There is increasing interest in simulating radiation interactions and radiation-induced damage at the level of cellular constituents and DNA to understand the biological effects of radiation. Simulations of microscopic tissue structure including cells and their components present computational challenges; furthermore, new approaches consistent with modern quantum physics may be required at very low energies and short distance scales. New methods for performing simulations of radiation transport on multiple scales, from patient-level down to cells and cell components in tissue, will be developed. These techniques will be applied to understand patterns of energy deposition within tissue for different radiation sources, towards developing an understanding of the biological effects of radiation. These new computational approaches will also be applied to study potential future treatment techniques such as delivery of radiotherapy involving nanometre-sized devices and other targeted therapies. This research will advance our knowledge of the interactions of radiation with matter and radiation dosimetry. It will yield new computational techniques to simulate radiation transport from macroscopic to microscopic length scales. Computer codes developed will be disseminated to the international research community to foster further research. The results of this research program will find application in many fields involving radiation physics including diagnostic imaging, radiation protection, radiobiology, and radiation therapy. This research will contribute to the development of new treatment techniques, as well as yielding new insights into past and current treatments.