• minibeam
• proton radiotherapy
• SNAKE

Proton minibeam radiotherapy, an innovative approach to reduce side effects in radiotherapy, has recently been developed at the ion microprobe SNAKE in Munich.
It consists of a spatially fractionated radiotherapy method using sub-millimeter proton beams. A homogeneous dose distribution can be achieved in the tumor, due to multiple Coulomb scatter, by applying multiple beams and adjusting beam size and inter beam distances. Moreover, the application of sub-millimeter proton beams spares a large number of healthy cells within the irradiation field.
Currently, the accelerator facility in Munich accelerates the proton beam up to 20 MeV using a Tandem Van de Graaff accelerator. Several experiments, both in vitro and in vivo, tested the absence of side effects at this energy.
A tandem post accelerator is planned to be built as a radio frequency linear accelerator, based on the TOP IMPLART project (ENEA institute, Rome), which allows the irradiation of small animals using a 70 MeV proton beam to further validate the potential of the proton minibeam therapy.
The aim of this thesis is to carry out a preliminary study of the conditions required to install a RF LINAC as post accelerator to ensure the efficiency of the proton minibeam therapy and the safety of the facility. For this purpose, three different experiments are performed.
The aim of the first experiment is to measure the beam spot size at the target using different irradiation setups to select which are suitable for proton minibeam technique. The beam spot size corresponds to the full width half maximum of dose distribution and it should be less than 400 μm to fulfill the request to spare healthy tissue and irradiate the tumor with a homogeneous dose. The experiment is carried out using 20 MeV proton beam and the experimental results are used to estimate the beam spot size at 70 MeV. Since a 70 MeV proton beam is unavailable, the experimental results at 20 MeV are rescaled using a theoretically derived scale factor from 20 MeV to 70 MeV to estimate the beam spot size at this energy.
The beam spots size at 20 MeV and 70 MeV are compared with the values obtained from SRIM simulations and theoretical calculations.
The aim of the second experiment is to find how to match the TANDEM beam with the RF LINAC. The best configuration of the frequency of the chopper and of the aperture of the slits in the tandem beam lime is chosen in order to obtain a normalized emittance ε<0.2 mm·mrad before LINAC and to irradiate the target with a current of I=1-10 nA, necessary for preclinical studies.
The aim of the third experiment is to estimate the dose rate produced during the acceleration process, which should never exceed Ḋ = 3 mSv/h to respect safety standards of the facility. In the LINAC, about 85% of the beam is lost up to E=18 MeV. The isotopes produced in this process and their activity are measured using a HPGe detector and a mobile dosimeter by irradiating a piece of copper using different beam parameters. Moreover, for every isotopes the maximum activity and dose rate achievable (at d=10 cm) and the time required to reach the dose rate safety criteria (Ḋ < 0.1 mSv/h) are calculated. The same analytical calculation are performed considering the effects of all isotopes and using different beam time scenarios.