Dose modification factor analysis of multilumen balloon brachytherapy applicator with Monte Carlo simulation

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• Multilumen applicators like Contura are used for accelerated partial breast irradiation (APBI) when asymmetric dose distributions are needed.
• Tissue heterogeneity corrections are crucial for accurate brachytherapy dose calculations, as recommended by AAPM Task Group 186.
• Many current treatment planning systems lack these essential heterogeneity corrections.

Purpose of the Study:

• To quantify the dose deviation caused by tissue heterogeneity when using the Contura brachytherapy applicator.
• To evaluate the dose modification factor (DMF) for the Contura applicator.
• To assess the dose-shaping capabilities of the Contura device for asymmetric dose distributions.

Main Methods:

• Modeling the Contura applicator using the Monte Carlo N-Particle (MCNP) code version 5.
• Simulating dose distributions with and without tissue heterogeneity.
• Calculating the dose modification factor (DMF) to quantify dose deviation.
• Comparing dose-shaping capabilities with MammoSite ML and SAVI devices.

Main Results:

• The dose modification factor (DMF) showed minimal dependence on symmetric versus asymmetric dose distributions.
• Simulations indicated that the actual dose delivered to the planning target volume (PTV) could be up to 12% lower than planned.
• The Contura applicator's dose-shaping capabilities were similar to MammoSite ML but inferior to SAVI.

Conclusions:

• Brachytherapy plans using the Contura applicator may require cautious interpretation due to potential underdosing of the PTV.
• Accurate dose calculations incorporating tissue heterogeneity are essential for effective APBI.
• Further research into applicator design and treatment planning is needed to optimize dose delivery.