Automatic verification of step-and-shoot IMRT field segments using portal imaging

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Intensity-modulated radiation therapy (IMRT) involves delivering numerous individual beam segments.
• The complex electronic transmission of treatment data in IMRT necessitates robust quality assurance.
• An independent monitoring system for actual field shape during delivery is crucial for IMRT quality assurance.

Purpose of the Study:

• To develop and test an independent system for monitoring radiation field shapes during IMRT delivery.
• To enhance the quality assurance process in step-and-shoot IMRT by verifying delivered field shapes against planned ones.

Main Methods:

• Development of a system that compares the radiation field detected by the linac's portal imaging system with the planned field shape from the treatment planning system.
• Utilization of a software algorithm to detect and compare leaf edge positions from portal images against calculated positions.
• The system is designed for automated operation with minimal radiation therapist intervention.

Main Results:

• The developed system successfully verifies field shapes by comparing detected radiation fields with planned shapes.
• The automated comparison algorithm accurately detects leaf edge positions.
• Testing with clinical plan sequences demonstrated the system's ability to alert operators to incorrect settings in real time.

Conclusions:

• The developed system provides an effective, automated method for real-time quality assurance of field shapes in IMRT.
• This independent verification adds a significant layer of safety to the complex IMRT delivery process.
• The system's real-time alerts can help prevent treatment errors and improve patient safety in radiation oncology.