Abstract
Background: 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.Materials and Methods: 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 10 8 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.Results: 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.Conclusion: 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.