At the MedAustron synchrotron facility, cancer patients will be treated with therapeutic carbon and proton beams. Although this center is mainly dedicated to clinical irradiation, it also provides great opportunities to perform various research in radiation physics. Researchers are able to experiment in a dedicated experimental irradiation room, using proton beams up to 800 MeV and carbon ions up to 400 MeV per nucleon. In the upcoming years, the research group Radiation Physics plans to address the following research topics related to ion beam therapy, as well as fundamental physics:
- experimental and theoretical studies of nucleus-nucleus inelastic cross sections;
- measurements of dose and energy distributions in human phantoms, using passive detectors, like thermoluminescence detectors and plastic nuclear track detectors, comparing of the results of Monte Carlo particles and heavy ion transport codes, and of treatment planning systems;
- improvement and development of particle and heavy ion transport codes;
- effects of ionizing radiation with different linear energy transfer (LET) on the deoxyribonucleic acid (DNA);
- range verification using positron emission tomography (PET).
The knowledge of nucleus-nucleus cross sections plays an important role, not only in physics as a fundamental quantity describing nuclear reactions and the production of nuclear fragments during the interaction process, but also for proton and ion beam therapy planning for proper dose delivery to the tumour regions. Due to lack of experimental data, systematic measurements of these cross sections for all relevant energies and projectile-target combinations achievable at MedAustron are planned.
Measurements of dose and LET distributions from both primary and secondary particles, including neutrons, in anthropomorphic phantoms will be performed with passive detectors, like thermoluminescence detectors and plastic nuclear track detectors. The results will be useful to compare calculations performed with different Monte Carlo particles and heavy ion transport codes, and the RayStation treatment planning system.
All measurements of cross sections, dose and energy distributions will be used for improvement and development of particle and heavy ion transport codes.
Due to an increasing use of protons and carbon ion beams for therapy, as well as plans for human exploration of Mars and long-duration missions on the Earth's moon, a better understanding of the biological effects of high LET radiation is needed. Complex DNA damage is considered a precursor of genomic instability and carcinogenesis. Since DNA is also a simple and reliable endpoint/biomarker to measure radiation biological damage, without repair and late cellular effects, clustered damaged DNA samples, resulting from exposure to high LET radiation, will be studied in detail.
The physical properties of ion beams allow a precise dose deposition to the tumor. Due to the sharp depth-dose profile (Bragg curve), the treatment of deep-seated tumors close to critical organs is possible. Additionally, the sharp dose profile makes range verification desirable. One possibility to verify the actual range of the beam particles in the human tissue is the use of PET. At MedAustron, a commercial PET scanner will be used for range monitoring in an off-line mode. The range verification using PET is based on β+-emitting nuclides produced in the body of the patient during the ion beam irradiation by nuclear reactions between the beam particles and the target during the treatment, e.g. carbon-11 is produced with a half-life of 20 min. From PET measurements, the dose cannot be deduced directly due to different underlying physical processes. A simulation is required to predict the β+-activity and the subsequent PET measurement to enable a comparison of the actually obtained PET data. Ideally, the measured and the predicted data are reconstructed using the same algorithm. A software framework aimed at the prediction of the PET measurement as well as at image analysis and comparison will therefore be established at MedAustron.
By means of PET measurements, using different target material it is also feasible to measure yields of the β+-emitting isotopes. This method can be applied to improve the knowledge on the corresponding cross sections.
Head of Applied Medical Physics Research
at the Technical University of Vienna