A simplified analytical dose calculation algorithm accounting for tissue heterogeneity for low-energy brachytherapy...

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• The American Association of Physicists in Medicine Task Group No. 43 (AAPM TG-43) formalism is the standard for brachytherapy dose calculations.
• Monte Carlo simulations indicate significant dose calculation errors in heterogeneous breast tissue for seed implants using the TG-43 method.

Purpose of the Study:

• To develop and validate an inhomogeneity correction factor (ICF) for Pd-103 brachytherapy in heterogeneous media.
• To improve the accuracy of dose calculations in breast seed implants by accounting for tissue heterogeneity.

Main Methods:

• Proposed an inhomogeneity correction factor (ICF) dependent on media attenuation properties, independent of source structure.
• Calculated dose in heterogeneous media as a product of TG-43 water dose and the ICF.
• Validated the ICF method by comparing absorbed dose in heterogeneous phantoms with Monte Carlo simulations.

Main Results:

• The ICF method demonstrated agreement within 5% with Monte Carlo simulations in soft tissues near Pd-103 sources.
• The ICF is calculated using linear attenuation and mass energy absorption coefficients.
• The method is independent of the brachytherapy source's internal structure.

Conclusions:

• The ICF provides a clinically applicable method to correct TG-43 dose calculations for tissue heterogeneity in Pd-103 brachytherapy.
• The ICF can be readily integrated into treatment planning systems, offering a practical alternative to complex Monte Carlo simulations.