A study of IMRT planning parameters on planning efficiency, delivery efficiency, and plan quality

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Planning

Background:

• Intensity-modulated radiation therapy (IMRT) is a complex radiotherapy technique requiring precise treatment planning.
• Optimizing IMRT planning and delivery efficiency is crucial for patient throughput and resource management.
• Inverse planning parameters significantly influence both plan quality and efficiency.

Purpose of the Study:

• To enhance head and neck IMRT planning and delivery efficiency.
• To evaluate the impact of inverse planning parameters on IMRT quality and efficiency.
• To identify optimal parameter settings for improved IMRT workflow.

Main Methods:

• Retrospective analysis of 11 head and neck IMRT patient plans.
• Utilized Pinnacle treatment planning system (TPS) to generate 45 plans per patient by varying dose/fluence grid resolution, minimum MU/segment, and minimum segment area.
• Evaluated plans based on dose-volume histograms (DVHs), planning time, and delivery time; developed and validated a delivery time model.

Main Results:

• A 4 mm dose grid with a 2 mm fluence grid reduced dose calculation time by 63% with minimal impact on DVH variation.
• Optimal thresholds for adequate plan quality were identified as 5 cm² for minimum segment area and 5 MU for minimum MU.
• Increasing minimum MU decreased segment count and delivery time; increasing minimum segment area reduced plan MU but had less impact on delivery time.

Conclusions:

• Increasing dose grid resolution while maintaining a fine fluence grid improves planning efficiency without compromising IMRT quality.
• Increasing minimum MU enhances delivery efficiency; increasing minimum segment area does not significantly improve delivery efficiency.
• Exceeding 5 MU for minimum MU or 5 cm² for minimum segment area is not recommended due to potential degradation of plan quality.