Head and neck (192)Ir HDR-brachytherapy dosimetry using a grid-based Boltzmann solver

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Accurate dosimetry is crucial for effective head and neck cancer brachytherapy.
• Traditional TG-43 formalism has limitations in complex geometries and tissue inhomogeneities.
• Advanced computational methods like Boltzmann solvers offer potential improvements.

Purpose of the Study:

• To compare dosimetry calculations for head and neck cancer brachytherapy patients.
• Evaluate differences between TG-43 formalism and a grid-based Boltzmann solver.
• Assess the clinical impact of these dosimetric variations.

Main Methods:

• 3D dosimetry was performed on 49 head and neck cancer brachytherapy patients.
• Calculations were conducted using both TG-43 formalism and a grid-based Boltzmann solver.
• Computed tomography (CT) was used for 3D treatment planning, accounting for tissue inhomogeneities.

Main Results:

• The grid-based Boltzmann solver yielded median D90 and V100 values approximately 3% lower than TG-43 (p < 0.01).
• A 1.6% increase in the V150 dose parameter was observed with the grid-based Boltzmann solver compared to TG-43 (p < 0.01).
• Mean D90 differences for the clinical target volume (CTV) were small (2.63 Gy vs. 2.71 Gy).

Conclusions:

• Significant dose differences exist between grid-based Boltzmann solver and TG-43 calculations for head and neck brachytherapy.
• Despite observed differences, current clinical practice for prescription doses in high-dose-rate head and neck brachytherapy remains unchanged.
• Further evaluation may be needed to fully integrate advanced solvers into clinical workflows.