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Dynamic multileaf collimation without 'tongue-and-groove' underdosage effects
J P van Santvoort1, B J Heijmen
1Department of Clinical Physics, Dr Daniel den Hoed Cancer Center/Academic Hospital Rotterdam, The Netherlands.
Physics in Medicine and Biology
|October 1, 1996
Summary
This study introduces a new method to prevent underdosage in intensity-modulated radiation therapy by synchronizing multileaf collimator leaf movements. This technique ensures accurate beam delivery, crucial for effective cancer treatment.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- Commercially available multileaf collimators (MLCs) use tongue-and-groove constructions to reduce leakage radiation between adjacent leaves.
- These constructions can lead to significant underdosages in intensity-modulated photon beams, compromising treatment accuracy.
Purpose of the Study:
- To present a novel method for calculating leaf trajectories in dynamic MLC that completely eliminates underdosage effects caused by tongue-and-groove constructions.
- To ensure accurate and reliable dose delivery in intensity-modulated radiation therapy (IMRT).
Main Methods:
- The proposed method synchronizes the trajectories of adjacent leaf pairs.
- The delivered beam intensity in the tongue-and-groove region is maintained at the minimum of the two prescribed intensities for the adjacent leaf pairs.
- Effectiveness was validated using numerous intensity-modulated fields on an MM50 Racetrack Microtron.
Main Results:
- The synchronization method effectively avoids underdosage effects associated with MLC tongue-and-groove designs.
- Beam-on times were found to be equal or longer compared to standard dynamic MLC without synchronization.
- A typical increase in beam-on time of 5% to 15% was observed in the studied cases.
Conclusions:
- The presented leaf trajectory calculation method offers a robust solution to underdosage issues in IMRT caused by MLC tongue-and-groove designs.
- This technique enhances the precision of radiation delivery, potentially improving treatment outcomes.
- While beam-on time may increase slightly, the improved dose accuracy is a critical benefit for patient safety and treatment efficacy.