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">This paper presents a Monte Carlo (MC) simulation study estimating Relative Biological Effectiveness at a 10% survival fraction (RBE10) of light ion beams by means of microdosimetric approach. Microdosimetric parameters for estimating Relative Biological Effectiveness (RBE) were determined through the utilisation of the Tool for Particle Simulation (TOPAS) MC simulations. These simulations incorporated a 3D silicon on insulator (SOI) Bridge microdosimeter model. </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 incident 176.8 MeV proton and 176.4 MeV/u helium ion beams were simulated at different depths within a water phantom. The microdosimetric aspects, such as&nbsp; </span></span></span><span lang="ru" style="font-size:9.0pt"><span style="font-family:&quot;Times New Roman&quot;"><span style="language:ru">у</span></span></span><span lang="en-US" style="font-size:5.9939pt"><span style="font-family:Calibri"><span style="language:en-US">_F</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US"> ̅ and </span></span></span><span lang="ru" style="font-size:9.0pt"><span style="font-family:&quot;Times New Roman&quot;"><span style="language:ru">у</span></span></span><span lang="en-US" style="font-size:5.9939pt"><span style="font-family:Calibri"><span style="language:en-US">_D</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US"> ̅ at different depths along the fields were predicted from simulations. The RBE10 were derived using simulated microdosimetric spectra as inputs to the modified Microdosimetric Kinetic Model (MKM). </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">Simulated </span></span></span><span lang="ru" style="font-size:9.0pt"><span style="font-family:&quot;Times New Roman&quot;"><span style="language:ru">у</span></span></span><span lang="en-US" style="font-size:5.9939pt"><span style="font-family:Calibri"><span style="language:en-US">_D</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US"> ̅ distributions for proton and helium ion beams in water were about 4 keV/&micro;m and 4 to 8 keV/&micro;m at the plateau region, respectively and around 7 to 14 keV/&micro;m and 35 to 56 keV/&micro;m at the Bragg peak (BP) region, respectively. In the tail region </span></span></span><span lang="ru" style="font-size:9.0pt"><span style="font-family:&quot;Times New Roman&quot;"><span style="language:ru">у</span></span></span><span lang="en-US" style="font-size:5.9939pt"><span style="font-family:Calibri"><span style="language:en-US">_D</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US"> ̅ values were increasing from 5 keV/&micro;m to 10 keV/&micro;m and 7 keV/&micro;m to 14 keV/&micro;m at depths of 224 mm to 250 mm, 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">The RBE10 for protons exhibit a range of 0.99 to 1.22, which differs from the standard practice of using a fixed RBE of 1.1 in the Treatment Planning System (TPS) for proton therapy. The simulation results in this study may be used as an outlook for radiobiological experiments in the NASA Space Radiation Laboratory (NSRL).</span></span></span></span></span></span></span></span></span></div> Helium ion, Modified MKM, NSRL, Proton, TOPAS. 703 709 http://ijrr.com/browse.php?a_code=A-10-1-1229&slc_lang=en&sid=1 M. Arif Efendi 7900319475328460028015 7900319475328460028015 No Department of Biomedical Imaging, Advanced Medical and Dental Institute, Universiti Sains Malaysia, Penang, Malaysia D. Sakata 7900319475328460028016 7900319475328460028016 No Division of Health Sciences, Graduate School of Medicine, Osaka University, Osaka, Japan Y.C. Keat ckying7@usm.my 7900319475328460028017 7900319475328460028017 Yes Department of Biomedical Imaging, Advanced Medical and Dental Institute, Universiti Sains Malaysia, Penang, Malaysia