A novel and individualized robust optimization method using normalized dose interval volume constraints (NDIVC) for...

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Intensity-modulated proton therapy (IMPT) is susceptible to uncertainties in patient setup and proton beam range.
• Existing robust optimization methods aim to mitigate these issues, but a clinically practical approach offering user control is needed.

Purpose of the Study:

• To introduce a novel, clinically practical robust optimization method for IMPT.
• To enable users to control the trade-off between nominal plan quality and plan robustness in a user-defined manner.

Main Methods:

• Calculated dose distributions for nominal and eight extreme uncertainty scenarios.
• Defined Normalized Dose Interval (NDI) and Normalized Dose Interval Volume Histogram (NDIVH) to quantify robustness.
• Incorporated a user-defined Normalized Dose Interval Volume Constraint (NDIVC) to specify desired robustness.

Main Results:

• The new method produced IMPT plans comparable in quality and robustness to voxel-wise worst-case optimization.
• Achieved more conformal and homogeneous target doses in some cases with appropriate NDIVC application.
• Demonstrated the feasibility of adjusting NDIVCs to explore the nominal plan quality versus robustness trade-off.

Conclusions:

• The NDIVH-based robust optimization offers a novel, individualized approach for IMPT.
• This method empowers users to customize the balance between plan quality and robustness.
• The approach is suitable for advancing future IMPT planning algorithms.