Robust optimization and robustness quantification in intensity modulated proton therapy

Intensity-Modulated Proton Therapy (IMPT) is highly sensitive to uncertainties in beam range, patient setup and organ motion. In the worst case and nominal scenarios, robustly optimized plans showed better target coverage, improved dose homogeneity, and lower or equivalent dose to organs at risk (OARs). Robust optimization provided significantly more robust dose distributions to targets and organs than conventional optimization in H&N using IMPT. Reduction of PTV and planning directly based on CTV provided better or equivalent OAR sparing. Also 4D robust optimization mitigated the influence of interplay effect than 3D robust optimization in lung cancer patients treated by IMPT.