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-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">High Dose Rate (HDR) brachytherapy is an internal radiation therapy method that delivers high-intensity radiation at >12 Gy/hour dose rate. In clinical practice, the dose calculation is often carried out using the TG-43 However, the method does not consider the effects of patient dimensions and tissue heterogeneity. To overcome this challenge, this study proposed the use of energy spectrum analysis of the source model used. </span></span></span></span><span lang="en-GB" 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-GB">Materials and Methods: </span></span></span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">GEANT4 Monte Carlo simulation was used to build the geometry of Bebig Co-60 A86 source and radiation interaction system. The interaction physics used Penelope with 1.0 &times; 10</span></span></span></span><span lang="en-GB" style="font-size:5.9939pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">⁸</span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB"> beam on. The scoring region was spherical with radius 20, 30, 40, and 50 cm as well as material variations of water, muscle, and bone. </span></span></span></span><span lang="en-GB" 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-GB">Results: </span></span></span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">The spectrum in Compton continuum scattering increased along with a reduction in radius and material density, while the opposite effect was observed at the photoelectric peak. The photoelectric peak ratio experienced 2.96 times increment when the radius of the muscle increased from 20 cm to 30 cm. In addition, the particle count experienced an increment as the radius and medium density of the scoring region increased, with linear regression values of 0.83 for bone and 0.91 for the water and muscle. </span></span></span></span><span lang="en-GB" 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-GB">Conclusion:&nbsp; </span></span></span></span></span></span><span lang="en-GB" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:black"><span style="language:en-GB">Increasing the radius and medium density led to variations in the height of the energy spectrum in Compton continuum and photoelectric regions. These variations caused an 18.42% increase in particle count when transitioning from 20 cm to 30 cm radius in water.</span></span></span></span></span></span></span></span></span></span></div> Energy spectrum, Co-60, HDR brachytherapy, Monte Carlo. 97 102 http://ijrr.com/browse.php?a_code=A-10-1-1297&slc_lang=en&sid=1 N. Qomariyah 7900319475328460030010 7900319475328460030010 No Department of Physics, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, Indonesia F. Haryanto freddy@itb.ac.id 7900319475328460030011 7900319475328460030011 Yes Department of Physics, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, Indonesia A. Waris 7900319475328460030012 7900319475328460030012 No Department of Physics, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, Indonesia R. Wirawan 7900319475328460030013 7900319475328460030013 No Department of Physics, Faculty of Mathematics and Natural Science, University of Mataram, Jl. Majapahit 62 Mataram 83125, Indonesia