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Interplay effects during Enhanced Dynamic Wedge deliveries
M B Kakakhel1, T Kairn, J Kenny
1School of Chemistry, Physics & Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001, Australia.
Summary
Enhanced Dynamic Wedge (EDW) treatments are affected by motion interplay. Tumor motion amplitude and period significantly impact dose discrepancies, especially with larger wedge angles and limited fractions.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Physics
Background:
- Understanding interplay effects in Enhanced Dynamic Wedge (EDW) treatments is crucial for accurate dose delivery.
- Tumor motion during radiotherapy can significantly alter planned dose distributions.
Purpose of the Study:
- To experimentally investigate the interplay effects in Enhanced Dynamic Wedge (EDW) treatments.
- To evaluate the impact of motion parameters (amplitude, period) and treatment factors (wedge angle, field size) on dose discrepancies.
Main Methods:
- Delivered single and multiple field EDW plans to a phantom on a moving platform with varying motion parameters.
- Investigated parallel and perpendicular motion, different wedge angles, and field sizes.
- Delivered a 4D CT-planned lung EDW treatment to a dummy tumor over four fractions.
Main Results:
- For parallel motion, both amplitude and period affected interplay, causing step functions and penumbral cut-offs.
- Tumor motion amplitude was dominant for perpendicular motion.
- Larger wedge angles showed more pronounced dose discrepancies.
- Small field sizes (5x5 cm²) resulted in loss of wedged distribution.
- 4D CT-planned delivery showed mixed over/under dosages with a 40% gamma pass rate (3%/1 mm DTA).
Conclusions:
- Tumor motion amplitude and period significantly influence interplay effects in EDW treatments.
- Limited fraction deliveries may not allow for averaging of EDW interplay effects.
- These findings highlight the importance of considering motion management in EDW radiotherapy planning.
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