en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;"><span style="font-size:10pt"><span style="text-justify:newspaper"><span style="text-kashida-space:50%"><span style="line-height:119%"><span style="font-family:Calibri"><span style="color:black"><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Background</span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-weight:bold"><span style="language:en-US">:</span></span></span></span></span> <span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">In this study, Monte Carlo simulations were performed to estimate the dose of proton therapy to involved and uninvolved organs in gastric cancer. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Materials and Methods:</span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US"> The dose received by involved and uninvolved organs during gastric treatment was simulated during pencil beam scanning proton therapy using the MIRD-UF phantom and the MCNPX code. In this modeling, the appropriate energy range for tumor treatment in the gastric tissue of an adult male MIRD-UF phantom with monoenergetic proton beams was calculated. The dose secondary charged particles, neutrons and photons in the tumor and vital organs were evaluated. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Results: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">The results showed that, depending on the size of the tumor, the appropriate and optimal range of proton energy to cover the tumor is 67 - 81.5 MeV. The distribution of energy deposition, total primary dose, and the ratio of neutron equivalent dose to absorbed therapeutic dose (H/D) were calculated for the tumor and 12 vital organs. The ratio between the total received dose of the healthy gastric tissue and the delivered dose of the tumor was about 0.0046. The average photon equivalent dose was about 0.9% of the neutrons. The highest H/D ratios for normal stomach, spleen, pancreas, and left kidney tissue were 0.167 mSv/Gy, 0.0362 mSv/Gy, 0.0231 mSv/Gy and 0.0143 mSv/Gy, respectively. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Conclusion: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">In the study, a small gastric tumor in an adult male phantom was irradiated with high-energy protons. Proton therapy delivered the highest possible dose to the tumor, while the healthy organs received a low dose.</span></span></span></span></span></span></span></span></span></div> Proton therapy, Gastric Cancer, Neutrons, Pencil Beam. 823 829 http://ijrr.com/browse.php?a_code=A-10-1-1245&slc_lang=en&sid=1 S. Sadrzadeh 7900319475328460028380 7900319475328460028380 No School of Physics, Damghan University, P.O. Box 36716-41167, Damghan, Iran M. Tajik tajik@du.ac.ir 7900319475328460028381 7900319475328460028381 Yes School of Physics, Damghan University, P.O. Box 36716-41167, Damghan, Iran