Ideal spatial radiotherapy dose distributions subject to positional uncertainties

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Radiotherapy commonly uses margins to create planning target volumes (PTVs) from clinical target volumes (CTVs) to account for setup errors and organ motion.
• Uncertainty in patient positioning and internal organ movement are significant challenges in delivering accurate radiotherapy doses.

Purpose of the Study:

• To develop a method for calculating ideal spatial dose distributions that minimize expected loss under conditions of uncertainty.
• To provide insights into the suitability and optimal selection of margins in radiotherapy planning.

Main Methods:

• Utilized weighted power loss functions to quantify treatment plan performance.
• Developed a method to calculate optimal spatial dose distributions assuming invariance to patient and internal structure displacement.
• Analyzed the impact of margin size and loss function parameters on dose distribution robustness.

Main Results:

• Identified a method to calculate ideal spatial dose distributions that are robust against uncertainties.
• Demonstrated that the common practice of increasing loss function power parameters to enforce target dose requirements can be counterproductive.
• Provided qualitative insights into the effectiveness of using margins and how to select appropriate margin sizes.

Conclusions:

• The developed method offers a way to create radiotherapy dose distributions that are more robust against setup errors and organ motion.
• Findings suggest a re-evaluation of current margin strategies in radiotherapy planning.
• Results can complement inverse planning techniques for improved treatment outcomes.