Purpose: Various Prompt Gamma rays (PGs) techniques have been proposed to monitor the proton range in-vivo, but the poor PGs statistics increase the complexity and the cost of its clinical implementation. Through this study, we propose injection of the non-radioactive elements such as ¹⁷O, ¹⁹F, ⁶⁴Zn, and ¹²⁷I in the tumor area to enhance the PGs production of the 4.44 MeV PG peak (P1) and 6.15 MeV PG peak (P2) that have been correlated with the distal fall-off of the proton Bragg Peak.
Methods: We have simulated the interaction of a mono-energetic 75 MeV, 100 MeV, 200 MeV, and 250 MeV incident proton beam in a co-centric cylindrical geometry using the TOol for PArticle Simulation (TOPAS) Monte Carlo (MC) toolkit. The outer cylinder (scorer) was filled with 100% H₂O and the inner cylinder (hypothetical tumor area) that is leveled with respect to the outer cylinder was filled with 0.1%, 0.5%, 1%, 5%, 10%, and 15% fractions in weight of the suggested elements + a % fraction in weight of H₂O, so that the total weight percentage of the composition of the inner material remains 100%.
Results: PG energy spectra were produced and the % change in PG production was recorded for all cases. Energy deposited versus depth was scored and compared with and without the addition of the stable element in the mixture. Nuclear cross sections for proton-tested nucleus interactions were also studied. We show that the selected stable elements, previously used in medicine, can improve the PG statistics under certain combinations of the incident proton beam energies and mixture composition.
Conclusion: The use of the suggested elements as PG enhancement agents in proton therapy is feasible. Further work is needed for the clinical applicability of this initial yet promising methodology.
Not Applicable / None Entered.