Radiation protection for ion therapy centre, simulations using Monte-Carlo with SRIM

The goal of particle therapy is to exploit the possibility of depositing a high dose in the target volume (usually the tumor) with a minimum dose in the surrounding healthy tissue. To achieve this goal, use is made of the characteristic shape of the dose profile deposited by the particles as a function of depth: a plateau followed by a peak (the so-called Bragg peak) and a drop to zero just before the end of the range. The irradiation is performed by ‘filling’ the target volume with Bragg peak doses. The particle energy determines the depth at which the Bragg peak dose will be deposited in the patient’s body. The clinically useful maximum beam energy for proton therapy is 200–250 MeV. For carbon ions, the maximum energy used is 400–450 MeV per nucleus. The lowest particle energies which are down to a few megaelectron volts are needed for treatment of very superficially located tissues. Today all particle treatments are done with beams of protons or carbon ions [1]. Carbon-ion beams have gained a strong interest because they exhibit Bragg peak in the body, followed by rapid dose fall-off beyond the peak, enabling delivery of sufficient dose to the target volume while minimizing the dose to the surrounding tissues. Furthermore, as compared with proton beams, carbon-ion beams cause less scattering and range-struggling in the body [2]. Radiation protection is a key aspect of any radiotherapy (RT) department; in Ion Beam Therapy (IBT) large and complex radiation producing devices are used and made available to the public for treatment. It is thus the responsibility of the facility to put in place measures to protect not only the patient but also the general public, occupationally and non-occupationally exposed personnel working within the facility, and electronics installed within the department to ensure maximum safety. The purpose of this study is to propose a radiation protection shielding (maze) made of sandwich walls composed of concrete walls with soil in between. This work will present the analysis of the shielding in case of dumping the direct proton or ion-beam into the maze wall. The analysis will be made using Monte Carlo simulations from the SRIM package.