title: An antiproton simulation study using MCNPX for radiation therapy.
abstract: Radiation therapy using antiprotons is a potential interesting future modality. Energetic antiprotons penetrate matter with almost near identical stopping powers and radio biological effectiveness (RBE) as protons in the region well before the Bragg peak region. When the antiprotons come to rest at or near the Bragg peak, they annihilate releasing almost 2 GeV per annihilation. Most of the energy is carried away on the average by 4 to 5 energetic pi mesons. The annihilations lead to roughly a doubling of physical dose with additional increase due to RBE in the Bragg peak region. This study was undertaken in order to assess the effect of the products of antiproton annihilations on depth dose profiles through MCNPX simulations. Beams of protons and antiprotons with varying energies and field sizes were used in the simulations. In our study, for 126 MeV beam, the peak to entrance (P/E) dose ratios of 4.9 for protons and 8.9 for antiprotons were found which gave the antiproton/proton P/E dose ratio equals to 1.8. This is in excellent agreement with the previous result obtained with FLUKA simulations.
authors.affiliation: University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Michael Handley
authors.forename: Salahuddin
authors.initials: S
authors.lastname: Ahmad
mesh_terms: D035843:Biomedical Research / Q000379:methods; D003198:Computer Simulation; D009010:Monte Carlo Method; D011522:Protons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted
chemical_list: D011522:Protons