Dose optimization of breast balloon brachytherapy using a stepping 192Ir HDR source

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• Stationary source anisotropy in breast balloon brachytherapy leads to significant underdosage (11%-13%) of the planning target volume (PTV).
• Achieving optimal dose coverage is crucial for effective radiation therapy outcomes.

Purpose of the Study:

• To improve PTV coverage in breast balloon brachytherapy by optimizing dwell positions and weights.
• To develop a practical optimization program for enhanced dose distribution.

Main Methods:

• A computational model was developed assuming spherical balloons (4.0-5.0 cm diameter) and a 1-cm thick PTV shell.
• The number of dwell positions (2-13) and their weights were varied to minimize dose discrepancies compared to ideal spherical distributions.
• Two objective functions were used: minimizing PTV-voxels with >10% dose difference and minimizing overall dose difference per PTV-voxel.

Main Results:

• Optimal PTV coverage was achieved with 8-11 dwell positions, with weights determined by the optimization scheme.
• The optimization resulted in ellipsoidal isodose distributions, potentially offering relative skin sparing.
• Volumetric dose optimization results closely matched literature findings from linear and multiple-points optimization methods.

Conclusions:

• The developed optimization scheme provides a simple and practical solution for improving PTV coverage in breast balloon brachytherapy.
• This method offers a viable approach for clinical application, addressing underdosage issues.
• The technique shows promise for enhancing treatment efficacy and patient outcomes.