Related Experiment Videos
Interleaf leakage for 5 and 10 mm dynamic multileaf collimation systems incorporating patient motion
1Radiation Oncology Center, Mallinckrodt Institute of Radiology, St. Louis, Missouri 63110, USA. klein_ee@castor.wustl.edu
Medical Physics
|September 11, 2001
Summary
Dynamic multileaf collimation (DMLC) for intensity modulated radiation therapy (IMRT) can lead to significant interleaf leakage (IL). This study shows that patient motion during treatment effectively reduces peak IL, making 5 mm leaf systems suitable for IMRT.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Technology
Background:
- Dynamic multileaf collimation (DMLC) is increasingly used in intensity modulated radiation therapy (IMRT).
- Interleaf leakage (IL) is an inherent issue in DMLC systems, potentially delivering significant unintended dose to non-target regions.
- IL is characterized by narrow peaks, but its impact can be substantial due to IMRT delivery inefficiencies.
Purpose of the Study:
- To investigate the impact of patient motion (longitudinal shifts and angulations) on interleaf leakage (IL) in dynamic multileaf collimation (DMLC) systems.
- To evaluate the performance of 5 mm and 10 mm leaf systems under simulated patient motion conditions.
- To determine the suitability of different DMLC leaf sizes for intensity modulated radiation therapy (IMRT).
Main Methods:
- Performed leakage studies using solid phantoms and film dosimetry with 5 mm and 10 mm leaf DMLC systems.
- Simulated intratreatment and intertreatment motions, including longitudinal shifts up to 4 mm and angulations up to 4 degrees.
- Compared DMLC delivery with segmented jaw delivery as a baseline and validated film data with a microionization chamber.
Main Results:
- Patient motion, in general, diminished peak interleaf leakage (IL) values across both 5 mm and 10 mm leaf systems.
- For the 10 mm system, IL decreased from 3.6% to 3.2%.
- The 5 mm system showed decreased IL with small shifts (2 mm) but increased with larger shifts (4 mm), indicating motion's complex effect.
Conclusions:
- Rigid body motion effectively reduces peak interleaf leakage (IL) values in dynamic multileaf collimation (DMLC) systems.
- Non-target regions are influenced more by an effective transmission than discrete IL peaks during patient motion.
- The 5 mm leaf system is appropriate for intensity modulated radiation therapy (IMRT) as it does not introduce increased IL and benefits from motion-induced reduction of peak leakage.