Dosimetric parameters for three low-energy brachytherapy sources using the Monte Carlo N-particle code

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Engineering

Background:

• Brachytherapy is a cancer treatment utilizing internal radiation sources.
• Accurate characterization of brachytherapy sources is crucial for effective radiation delivery.
• Syncor Pharmaceuticals Inc. manufactures commonly used brachytherapy seeds, including 125I and 103Pd isotopes.

Purpose of the Study:

• To perform Monte Carlo calculations for characterizing the dosimetric properties of three brachytherapy sources.
• To determine the dose rate constant, radial dose function, and anisotropy for specific 125I and 103Pd seeds.
• To validate the calculated dosimetric data against established protocols and existing literature.

Main Methods:

• Monte Carlo N-Particle (MCNP) code was employed for simulations.
• Dosimetric properties were calculated in water according to the TG-43 protocol.
• Calculations included dose rate constant, radial dose function g(r), and anisotropy function F(r, theta).

Main Results:

• The dose rate constant for BT-125-1 (125I) was 0.955±0.005 cGyh⁻¹U⁻¹.
• The dose rate constant for BT-125-2 (125I) was 0.967±0.005 cGyh⁻¹U⁻¹.
• The dose rate constant for BT-103-3 (103Pd) was 0.659±0.005 cGyh⁻¹U⁻¹.

Conclusions:

• Monte Carlo calculations provide accurate dosimetric characterization of Syncor brachytherapy seeds.
• The calculated dose rate constants, radial dose functions, and anisotropy values align with published data.
• This study validates the use of MCNP for brachytherapy source dosimetry.