Affiliations: University of Oklahoma Health Sciences Center,
Oklahoma City, OK, USA
Note: [] Corresponding author: Salahuddin Ahmad, Ph.D., University of
Oklahoma Health Sciences Center, Department of Radiation Oncology, 825 N. E.
10th, Suite 1430, Oklahoma City, Oklahoma, OK 73104, USA. Tel.: +1 405 271
5641; Fax: +1 405 271 8297; E-mail: [email protected]
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.
