Clinically-implementable template plans for multidwell treatments using Leipzig-style applicators in ¹⁹²Ir surface...

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• Leipzig-style applicators offer dose uniformity and treatment area expansion via multiple dwell positions (multidwell).
• Accurate dose calculations for these non-water-equivalent applicators with complex geometry necessitate model-based dose calculation algorithms (MBDCAs).

Purpose of the Study:

• To develop template plans using MBDCA calculations for Leipzig-style applicators.
• To provide users without MBDCA access with pre-calculated dwell times and positions for multidwell brachytherapy.

Main Methods:

• Designed five template plans using a Leipzig-style applicator model and MBDCA within a treatment planning system.
• Optimized plans normalized to 0.3 cm depth in a water phantom, with varying dwell positions, times, and active lengths (0.5-1.5 cm).
• Assessed the impact of intrafraction rotation and rotational offsets (up to ±10°) on dose coverage metrics (V100%, D95%, minimum dose).

Main Results:

• The 90% (80%) isodose line dimensions at 0.3 cm depth increased significantly with multidwell template plans compared to single-dwell.
• Template plans demonstrated substantial increases in treatment area, e.g., 90% isodose dimensions grew from 0.94 × 0.97 cm² to 2.09 × 1.24 cm².
• Rotational offsets up to ±10° minimally impacted V100% (≤2.0%), D95% (≤1.9%), and minimum dose (≤8.0%).

Conclusions:

• A set of template plans was successfully created, enhancing accessibility to multidwell brachytherapy techniques.
• These templates enable users without MBDCA access to leverage advanced treatment planning for Leipzig-style applicators.
• Clinical implementation requires careful review of each template plan before use.