Best Practice: CT-guided Adaptive Radiotherapy Reference Planning on the Ethos Platform.

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Conventional radiotherapy uses static plans, limiting adaptation to anatomical changes.
• Online adaptive radiotherapy (ART) allows real-time treatment plan adjustments.
• CT-guided ART (CTgART) on the Varian Ethos platform is increasingly adopted but relies heavily on initial reference plan quality.

Purpose of the Study:

• To present a practical framework, termed "Thinking in 4D," for designing robust online adaptive radiotherapy reference plans.
• To provide strategies for integrating standard planning with temporal workflow considerations in ART.
• To improve the quality, efficiency, and safety of adaptive radiotherapy planning and delivery.

Main Methods:

• Development of a planning framework integrating standard planning with temporal workflow considerations.
• Leveraging high-volume clinical experience with hundreds of adaptive cases across multiple institutions.
• Formulating practical recommendations and strategies for robust Varian Ethos reference plan template design.

Main Results:

• The "Thinking in 4D" framework emphasizes understanding upstream planning impacts on downstream adaptation.
• Practical strategies are provided to enhance optimization robustness and on-treatment efficiency.
• Recommendations are based on accumulated clinical experience to guide template design.

Conclusions:

• The "Thinking in 4D" approach offers practical guidance for clinicians designing ART reference plans.
• This paradigm aims to improve adaptive plan quality, efficiency, and safety.
• The framework supports the implementation, training, and routine checks for teams adopting advanced ART.