Dosimetric comparison between microSelectron iridium-192 and flexi cobalt-60 sources in high-dose-rate brachytherapy...

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Miniaturized iridium-192 (¹⁹²Ir) sources are preferred in brachytherapy for their flexibility.
• Cobalt-60 (⁶⁰Co) sources offer a longer half-life, making them a viable alternative for high-dose-rate (HDR) brachytherapy.

Purpose of the Study:

• To compare the TG-43 dosimetric parameters of HDR flexi ⁶⁰Co and HDR microSelectron ¹⁹²Ir sources.
• To evaluate the suitability of these sources for modern brachytherapy applications.

Main Methods:

• Monte Carlo simulations using Geant4 (v.11.0) were performed.
• Calculations followed AAPM TG-43 formalism for validation.
• Key parameters included radial dose function, anisotropy function, and dose-rate constants in a water phantom.

Main Results:

• Dose-rate constants were similar: 1.108 cGy h^-1U^-1 for ¹⁹²Ir and 1.097 cGy h^-1U^-1 for ⁶⁰Co.
• ⁶⁰Co showed higher radial dose function values beyond 22 cm.
• Anisotropy increased more sharply for the ⁶⁰Co source.

Conclusions:

• ¹⁹²Ir photons have limited range and are attenuated, affecting dose distribution.
• ⁶⁰Co sources may be more effective for treating tumors beyond the immediate source vicinity.
• ⁶⁰Co offers potential advantages in dose delivery for certain brachytherapy scenarios.