en Clinical Medicine Clinical Medicine مقاله پژوهشی Original Research Article <span style="font-size:10pt"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="background:#2d7f8f"><span style="color:white">Background & Objective:</span></span></span></b><b> </b><b>&nbsp;</b><span style="font-size:9.0pt"><span style="color:black">Proton therapy has emerged as a superior method in cancer treatment compared to traditional photon-based radiation therapies. Because of the unique physical features of protons and Bragg curve, it can deliver the greatest dosage directly to the tumor while minimizing the radiation absorbed by surrounding healthy tissues. By spreading out Bragg Peak, proton therapy ensures that the tumor receives the prescribed high dose while reducing side effects. In proton therapy, the positrons play a significant role in dose monitoring and imaging.</span></span></span></span><br> <span style="font-size:10pt"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="background:#2d7f8f"><span style="color:white"><span style="letter-spacing:-.1pt">&nbsp;Materials & Methods:</span></span></span></span></b> &nbsp;<span style="font-size:9.0pt"><span style="color:black"><span style="letter-spacing:-.1pt">In this research, GEometry ANd Tracking (GEANT4) simulation code was used to study the number of positrons emitted and their dose depositions during proton therapy at energies of 50 and 100 MeV in both soft tissue and bone with variety of densities.</span></span></span></span></span><br> <span style="font-size:10pt"><span new="" roman="" style="font-family:" times=""><b><span lang="EN-IN" style="font-size:9.0pt"><span style="background:#2d7f8f"><span style="color:white">Results: </span></span></span></b><b>&nbsp;</b><span style="font-size:9.0pt"><span style="color:black"><span style="letter-spacing:-.1pt">The results showed that for 50 MeV protons, ¹⁵O was identified as the positron emitter that emits the most positrons in both tissues at two energies. The maximum penetration depth of 50 MeV proton beam was 26 mm in soft tissue and 16 mm in bone, while at 100 MeV, the depth was 89 mm in soft tissue and 53 mm in bone. Furthermore, the dose deposition by positrons decreases by increasing tissue density.</span></span></span></span></span><br> <span style="font-size:10pt"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="background:#2d7f8f"><span style="color:white">Conclusion: </span></span></span></b><b>&nbsp;</b><span style="font-size:9.0pt"><span style="color:black">In proton therapy 50 and 100 MeV the most positrons emitted from ¹⁵O, ¹¹C, ³⁰P, ¹³N, ³⁸k, ³⁹Ca in soft tissue and bone.</span></span></span></span><br> &nbsp; Proton therapy, Positron emitters, Dose deposition, GEANT4 simulation code 405 414 http://journal.zums.ac.ir/browse.php?a_code=A-10-7145-1&slc_lang=en&sid=1 Amir Reza Khoshhal amirrezakhoshhal79@gmail.com 5200319475328460082400 5200319475328460082400 Yes Faculty of Sciences and Modern Technologies, Graduate University of Advanced Technology, Kerman, Iran Ahmad Esmaili Torshabi ahmad4958@gmail.com 5200319475328460082401 5200319475328460082401 No Faculty of Sciences and Modern Technologies, Graduate University of Advanced Technology, Kerman, Iran Sharareh Babamohammadi shararehb15@gmail.com 5200319475328460082402 5200319475328460082402 No Faculty of Sciences and Modern Technologies, Graduate University of Advanced Technology, Kerman, Iran