84. Monte Carlo simulations of light ion dose distribution in tissue-like media: dosimetry and diagnostics aspects

AimThe radiobiological superiority of ions heavier than protons, with an augmentation of the RBE by a factor of 3–4 relative to that of conventional beams, led to an increased interest worldwide in light ion radiation therapy. In order to evaluate the dose delivered to tissue and to estimate biological effects in ion radio-therapy, accurate knowledge of the phsics of ion interaction with media is necessary and accurate transport computational methods are required. The aim of this work is to present the use of the SHIELD-HIT Monte Carlo code for the computations of ion beam dose distribution in tissue-like media. The application of the SHIELD-HIT for in situ monitoring of ion dose delivery to a patient using calculated distributions of isotopes for PET imaging is also discussed.Material and MethodsThe Monte Carlo code SHIELD-HIT (Heavy Ion Transport) has been used to simulate the transport of proton and light ions in tissue-like media for projectiles with energies up to 500 MeV/u.ResultsGood agreement between the SHIELD-HIT results and experimental data is obtained for the depth dose distributions of protons and 12C ions impinging on water. The computed distribution of the PET emitters in a PMMA Phantom irradiated by neon ions shows good agreement with experimental data ftrom the GSI laboratory.ConclusionsCurrently, the SHIELD-HIT Monte Carlo code is one of the most accurate ion transport codes, suitable for ion therapy purposes. Based on numerous comparisons with experimental data, this code predicts adequately ion energy deposition along the whole track including the Bragg peak. It is concluded that a careful analysis of stopping power data is necessary for radiotherapy applications, since an incorrect estimation of the position of the Bragg peak might lead to a significant deviation from the prescribed dose in small target volumes