Characterisation of Proton and Helium Ion Beams Therapy Using Geant4 GATE Monte Carlo Simulation

Hadron beam therapy has a major advantage over conventional therapy in terms of depositing the maximum energy before it stops, which gives a lower dose to healthy tissues and organs. To benefit from hadron properties, treatment has to be delivered as it is planned with optimal accuracy. Monte Carlo (MC) simulations play an important role in radiotherapy, especially as a method to evaluate the physical properties that are either impossible or difficult to measure. GEANT4 GATE is one of the simplest Monte Carlo (MC) codes that has been used in many medical applications including hadron radiotherapy. Geant4 GATE Monte Carlo simulation that was mainly used to analyse energy deposition curves (Brage Gray curve) produced by Proton ¹₁H and Helium ⁴₂ He in radiotherapy energy range. The simulation was validated using a circular beam (radius = 1.5 cm) of proton ¹₁H with energy 55.25, and 252 MeV/u and helium ⁴₂ He with energy 250.3 MeV/u in a polyethylene phantom (ρ = 0.97 gr/cm³), to compare the results of the simulation with the values obtained by the NASA Space Radiation Laboratory (NSRL) [1]. The results of the simulation were found to agree with the measured values in (NSRL) with less than 2% shift, and the shift can be understandable, as beam geometry details haven't been mentioned in (NSRL) data, so we had to assume the beam size and shape. [1] A square beams (8 x 8 cm²) of (60 MeV/u) proton ¹₁H and (59.5 MeV/u) helium ⁴₂He used, first with a water phantom and then with a heterogeneous phantom consisting of a biological material layer to analyze energy deposition curves (Brage Gray curve), further analysis was performed for some of the secondary particle energy depositions for the square beams in water. The square beam energy has been carefully selected to provide the same maximum depth to compare proton ¹₁ H and helium ⁴₂ He energy deposition curves. The result in water, coupled with the higher relative biological effect, shows that it may be possible to use ⁴₂ He beam to achieve higher energy deposition and to obtain a therapeutic dose better than ¹₁H beam radiotherapy. The results in a heterogeneous comparison to water in the peak region of the Bragg-Gray curve demonstrated that the energy deposition in lung material is lower than that in water, while in bone material is higher than that inwater in both proton ¹₁H and helium ⁴₂He beams. On the other hand, in the tail region of the Bragg-Gray curve, the energy deposition is very small in both prtoton ¹₁H and helium ⁴₂He beams.