A Monte Carlo study on dose distribution evaluation of Flexisource (192)Ir brachytherapy source

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Brachytherapy source dosimetry is crucial for accurate radiation therapy.
• Task Group 43 (TG-43) of the American Association of Physicists in Medicine (AAPM) provides guidelines for dosimetric evaluation.
• The (192)Iridium Flexisource is a commonly used brachytherapy source requiring precise dose characterization.

Purpose of the Study:

• To evaluate the dose distribution of the Flexisource (192)Ir source using Monte Carlo simulations.
• To compare simulated dosimetric parameters with previously published data for verification.
• To assess the agreement between treatment planning system (TPS) calculations and Monte Carlo (MC) simulations for the Flexisource.

Main Methods:

• Utilized the MCNPX code to simulate the Flexisource (192)Ir.
• Calculated dose rate constant and radial dose function in water and soft tissue phantoms.
• Simulated dose rates along the transverse axis for both Flexisource and a point source, comparing results with the Flexiplan TPS.

Main Results:

• Dose rate constants for water and soft tissue phantoms were determined to be 1.108 and 1.106, respectively.
• Radial dose function and dose rate values were presented in tabulated data and figures.
• Maximum difference between TPS and MC dose rate values was 11% in a water phantom at 6.0 cm.

Conclusions:

• The study verified the accuracy of the Flexisource (192)Ir simulation by comparing dosimetric parameters with published values.
• Simulated dose rate constant and radial dose function were consistent for Flexisource and point sources in water and soft tissue.
• TPS calculations for the Flexisource in water showed agreement with MC simulations within uncertainties, validating TPS accuracy.