Photon optimizer (PO) vs progressive resolution optimizer (PRO): a conformality- and complexity-based comparison for...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Planning

Background:

• Intensity-modulated arc therapy (IMAT) is a widely used radiotherapy technique.
• Optimizers play a crucial role in developing efficient and effective IMAT plans.
• Comparing novel optimizers with established ones is essential for clinical adoption.

Purpose of the Study:

• To compare the performance of the photon optimizer (PO) against the progressive resolution optimizer (PRO) for IMAT.
• To evaluate plan conformity, target coverage, organ-at-risk sparing, and plan complexity.
• To provide guidance on the advantages and limitations of PO in clinical settings.

Main Methods:

• Eleven diverse treatment plans (prostate, head and neck, brain) were generated using both PRO and PO algorithms.
• A standardized plan template with identical objectives and iterations was used for comparability.
• Plan analysis included conformity metrics (coverage factor, conformation number, homogeneity) and complexity metrics (MLC variability, modulation scores, monitor units).

Main Results:

• Both PRO and PO achieved comparable target volume coverage and dose conformity across most sites.
• PO plans demonstrated generally improved organ-at-risk sparing compared to PRO plans.
• PRO plans exhibited lower complexity, with reduced MLC leaf variability and monitor unit usage than PO plans.

Conclusions:

• The photon optimizer (PO) can produce IMAT plans with similar target conformity and enhanced organ-at-risk sparing compared to the progressive resolution optimizer (PRO).
• PO-optimized plans may present higher multileaf collimator variability and monitor unit requirements.
• Clinical implementation of PO necessitates careful assessment of plan conformity and complexity to ensure deliverability.