Preliminary characterization of the external proton beam from a PET cyclotron for use in neutron and proton radiobiology and other dosimetric studies

Different cyclotron models capable of accelerating protons up to 20MeV have been worldwide installed. Although their purpose is mainly positron emission tomography (PET) radioisotope production, they are equipped with several beam lines suitable for scientific research. Each beam line may typically deliver proton currents up to 150 μA (1×10¹⁵ particles/s). Radiobiological and dosimetric studies can be performed using these beam lines, which may contribute to further improve ion therapy and material radiation hardness results, among other applications. We report experimental results aiming at characterizing the proton beam achievable outside a PET cyclotron. In addition, we simulate this experimental setup by using Geant4. We show that simulation is consistent with previous published experimental data and with our first-measured results. These point to a beam angular spreading which may be utilized to establish an irradiation setup within the bunker. We estimate that the dose achievable with such setup may span 4-orders-of-magnitude, useful in radiobiology, ranging from 10mGy to 100 Gy. Finally, we show by simulation that neutron and γ-ray dose on a realistic, in-bunker target is negligible down to at most the 1% level. Further quantification for lower levels is ongoing.