Dynamic delivery of IMRT using an independent collimator: a model study

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Intensity-modulated radiation therapy (IMRT) requires precise beam shaping.
• Dynamic multileaf collimators (dMLC) are commonly used for IMRT beam delivery.
• Limitations of dMLC include discrete leaf movement and tongue-and-groove effects.

Purpose of the Study:

• To develop and evaluate a model for intensity-modulated beam delivery using dynamic independent collimators (dIC).
• To optimize dIC jaw trajectories for desired beam intensity maps.
• To compare the delivery efficiency of dIC with dMLC for prostate and nasopharynx cancer cases.

Main Methods:

• A computational model was developed using adaptive simulated annealing to optimize dIC jaw trajectories.
• dIC trajectories were generated as a series of control points for continuous jaw movement.
• Delivery times of dIC were compared to dMLC for 56 prostate and 72 nasopharynx intensity maps, assuming equivalent accuracy.

Main Results:

• dIC delivery time was 2.00 ± 0.83 times longer than dMLC for prostate cases.
• dIC delivery time was 2.90 ± 1.39 times longer than dMLC for nasopharynx cases.
• Estimated mean treatment times were 5.8 min for prostate and 12.2 min for nasopharynx cases.

Conclusions:

• Dynamic independent collimators (dIC) offer potential for high-resolution IMRT due to continuous spatial resolution and sharp penumbra.
• Despite longer delivery times compared to dynamic multileaf collimators (dMLC), dIC presents advantages for specific radiotherapy applications.
• Further investigation into dIC's clinical utility for precise IMRT is warranted.