Performance evaluation of respiratory motion-synchronized dynamic IMRT delivery

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Respiratory motion significantly impacts radiation therapy accuracy for lung tumors.
• Dynamic Intensity-Modulated Radiation Therapy (IMRT) aims to adapt radiation delivery to target motion.
• Motion-synchronized IMRT (MS-IMRT) is an advanced technique for improving dose delivery precision.

Purpose of the Study:

• To evaluate the dosimetric accuracy of DMLC-based MS-IMRT under varying dose rates.
• To compare MS-IMRT performance against static and gated IMRT techniques.
• To identify optimal dose rates for MS-IMRT delivery in lung cancer patients.

Main Methods:

• MS-IMRT plans were created by synchronizing DMLC leaf motion with simulated respiratory patterns (4s period, 2cm amplitude).
• Plans were delivered at 100, 400, and 600 MU/min using a medical linear accelerator.
• Fluence measurements using a 2D ion chamber array on a moving platform were compared to static deliveries via gamma analysis.

Main Results:

• MS-IMRT demonstrated superior dosimetric accuracy compared to gated and non-MS-IMRT deliveries.
• The 100 MU/min MS-IMRT delivery showed significantly better dosimetric accuracy.
• High dose rates (600 MU/min) led to dose-rate modulation and beam hold-offs, compromising synchronization and increasing dose deviations.

Conclusions:

• MS-IMRT is a viable technique for improving dosimetric accuracy in lung cancer radiotherapy.
• Lower dose rates (e.g., 100 MU/min) are preferable for maintaining synchronization and accuracy in MS-IMRT.
• High dose rates require careful consideration due to potential synchronization issues and increased dose errors.