A new smoothing procedure to reduce delivery segments for static MLC-based IMRT planning

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Pixel-based intensity-modulated radiation therapy (IMRT) using step-and-shoot delivery faces challenges with prolonged treatment times.
• Reducing IMRT delivery time is crucial for improving patient comfort and operational efficiency in radiation oncology.

Purpose of the Study:

• To develop and evaluate an integrated IMRT planning system incorporating a smoothing method to decrease beam profile complexity and shorten delivery times.
• To assess the trade-off between plan quality and delivery efficiency using the proposed IMRT planning system.

Main Methods:

• An inverse planning process utilizing a least-square dose-based cost function and simulated annealing with discrete intensity levels.
• A novel smoothing technique applied to intensity maps, averaging adjacent beamlets based on anatomical structure indices, with clinical protocol-based acceptance criteria.
• Reoptimization of segment weights post-smoothing to refine plan quality and ensure clinical acceptability.

Main Results:

• The integrated IMRT planning system successfully reduced segment numbers and delivery times by up to 40% in clinical cases (medulloblastoma, prostate, oropharyngeal carcinoma).
• While a slight degradation in original plan quality was observed, all final plans met predefined clinical acceptance criteria.
• The smoothing method effectively reduced intensity map complexity, contributing to shorter treatment durations.

Conclusions:

• The developed integrated IMRT planning system offers a viable method for reducing treatment delivery times in step-and-shoot IMRT.
• The system demonstrates that significant reductions in delivery time can be achieved while maintaining clinically acceptable plan quality.
• This approach holds promise for enhancing efficiency in radiation therapy delivery without compromising patient safety.