Influence of robust optimization in intensity-modulated proton therapy with different dose delivery techniques

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Intensity-modulated proton therapy (IMPT) offers advantages but is sensitive to uncertainties.
• Distal edge tracking (DET) in IMPT is energy-efficient and simplifies planning but requires robust optimization.
• Understanding plan robustness is crucial for clinical application of advanced IMPT techniques.

Purpose of the Study:

• To explore the application of DET in IMPT (IMPT-DET).
• To conduct robust optimization of IMPT-DET to reduce sensitivity to uncertainties.
• To compare robust and conventional optimization of IMPT-DET with three-dimensional IMPT (IMPT-3D).

Main Methods:

• Compared robustness of IMPT-DET and IMPT-3D plans for prostate and base of skull cancer cases.
• Utilized highest and second highest energy layers for Bragg peak at distal edge in IMPT-DET.
• Performed worst-case robust optimization considering range and setup uncertainties; evaluated plans using robust quantification.

Main Results:

• Without uncertainties, DET is less robust than 3D but offers better normal tissue protection.
• Robust optimization improved IMPT plan robustness against range and setup uncertainties.
• The extent of robustness improvement varied, indicating nuanced effects of optimization.

Conclusions:

• Robust optimization enhances IMPT plan robustness against uncertainties.
• Improvement mechanisms include localized single-field uniform dose distribution and perturbed dose distribution.
• Multiple-instance optimization enhances IMPT robustness by leveraging knowledge of influence matrices.