Heterogeneous physical phantom for I-125 dose measurements and dose-to-medium determination

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Brachytherapy

Background:

• Brachytherapy (BT) validation in heterogeneous media lacks experimental data.
• TG-186 requests true reference data for treatment planning.
• Monte Carlo (MC) calculations require experimental validation.

Purpose of the Study:

• Implement a physical phantom for brachytherapy validation in heterogeneous media.
• Generate reference data for ¹²⁵I dose distribution.
• Experimentally validate MC calculations and determine dose conversion factors (DCF).

Main Methods:

• Incorporated heterogeneous materials (adipose, bone, breast, lung) into a physical phantom.
• Performed MC calculations using MCNP6.2 code.
• Measured LiF response and calculated DCF using cavity theory.

Main Results:

• The heterogeneous phantom yielded accurate dose data for converting LiF response to absorbed dose.
• Achieved excellent dosimetry with a maximum uncertainty of 6.92% (k=1) for low-energy BT sources.
• Validated the dose conversion methodology across different media.

Conclusions:

• The reproducible heterogeneous phantom provides precise dose evaluations.
• Results support the dose conversion methodology for various tissues.
• Experimental validation of DCF is significant for clinical brachytherapy, applicable to water and other media.