A versatile physical phantom design and construction for I-125 dose measurements and dose-to-medium determination

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Brachytherapy Research

Background:

• Experimental validation of dose calculation algorithms is crucial for brachytherapy accuracy.
• There is a scarcity of experimental studies for brachytherapy validation, hindering the development of accurate dose calculation methods.
• TG-186 guidelines request independent reference data for brachytherapy quality assurance.

Purpose of the Study:

• To present a novel phantom for generating reference data for brachytherapy validation.
• To perform accurate experimental dose measurements of ¹²⁵I brachytherapy seeds using LiF dosimeters.
• To experimentally validate Monte Carlo (MC) calculations and model-based dose calculation algorithms (MBDCA) and evaluate a LiF dose conversion methodology.

Main Methods:

• A physical phantom made of PMMA with cavities for LiF dosimeters and ¹²⁵I seeds was designed.
• Monte Carlo simulations using MCNP6.2 were employed to score absorbed dose and determine dose conversion parameters.
• A sensitivity analysis was conducted to identify and quantify sources of uncertainty.

Main Results:

• The developed phantom and experimental procedure yielded precise dose data with an uncertainty of 5.68% (k=1).
• The experimental results enabled the conversion of LiF responses to absorbed dose in the medium.
• The dose conversion factor methodology was successfully validated using the experimental data.

Conclusions:

• The simple, reproducible phantom design facilitates precise dose evaluations for brachytherapy.
• The experimental measurements support the proposed dose conversion methodology.
• The phantom and methodology are adaptable for use with different materials and radiation sources, advancing brachytherapy research.