SU-D-213AB-03: Design Optimization of a HDR Ir-192 Brachytherapy Skin Applicator Using Monte Carlo-Based Dosimetry

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• AccuBoost applicators are used for whole breast irradiation.
• Augmenting AccuBoost with a wedge and tungsten window allows for skin cancer treatment.
• Existing designs require optimization for conformal and homogeneous skin brachytherapy.

Purpose of the Study:

• To design an optimized skin applicator for brachytherapy.
• To achieve conformal and homogeneous dose delivery to the skin.
• To minimize dose to organs at risk (OARs).

Main Methods:

• Modified a 6 cm round AccuBoost applicator with internal cone, wedge, and external window.
• Utilized Monte Carlo (MC) methods (MCNP5) for dose characterization and optimization.
• Iteratively varied component dimensions in simulations using HDR Ir-192 dose distributions.

Main Results:

• Internal wedge angle controlled field size and limited depth-dose spread.
• Internal cone and collimating window enhanced dose conformity.
• A 3 mm window thickness was optimal, balancing treatment time and dose rate; the design improved lateral coverage at 5mm depth.

Conclusions:

• Established standardized criteria for skin applicator dose optimization.
• An optimized AccuBoost skin applicator design was achieved using MC methods.
• Further optimization for different applicator diameters and clinical evaluation are in progress.