Multiple-CT optimization: An adaptive optimization method to account for anatomical changes in intensity-modulated...

Area of Science:

• Medical physics
• Radiation oncology
• Cancer treatment

Background:

• Intensity-modulated proton therapy (IMPT) is an advanced radiation technique.
• Anatomical changes during treatment can compromise IMPT plan efficacy.
• Adaptive replanning is often required to maintain treatment accuracy.

Purpose of the Study:

• To evaluate if multiple-CT (MCT) optimization of IMPT improves plan robustness to anatomical variations.
• To determine if MCT optimization can reduce the need for adaptive replanning in head and neck cancer patients.

Main Methods:

• Retrospective analysis of 10 head and neck cancer patients treated with IMPT.
• Generated selective robust IMPT plans using primary planning CT (PCT), adaptive CT 1 (ACT1), and adaptive CT 2 (ACT2) data.
• Created a MCT optimized plan using PCT and ACT1 data, then re-calculated doses on ACT2 data for comparison.

Main Results:

• MCT plans met all target and organ-at-risk criteria across all CT datasets.
• PCT and ACT1 plans showed compromised target coverage and organ-at-risk doses when re-calculated on ACT2 data.
• MCT plans demonstrated robust target coverage (CTV1, CTV3) and reduced doses to critical structures (chiasm, esophagus, larynx) on ACT2 data.

Conclusions:

• MCT optimization enhances IMPT plan robustness against anatomical changes.
• This strategy holds potential for reducing the frequency of adaptive replanning in head and neck cancer treatment.