Related Experiment Videos
How much margin reduction is possible through gating or breath hold?
M Engelsman1, G C Sharp, T Bortfeld
1Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston MA 02114, USA. mengelsman@partners.org
Physics in Medicine and Biology
|March 19, 2005
Summary
Intra-fractional breathing motion significantly impacts radiosurgery safety margins. Controlling breathing motion during treatment, especially for larger motions, can substantially reduce required safety margins, improving treatment precision.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiosurgery
Background:
- Intra-fractional breathing motion introduces uncertainties in radiation delivery.
- Accurate tumor targeting is crucial for effective radiosurgery and minimizing off-target dose.
Purpose of the Study:
- To determine the relationship between intra-fractional breathing motion and required safety margins in radiosurgery.
- To quantify the potential reduction in safety margins achievable through breathing motion control techniques.
Main Methods:
- Analysis of real-time tumor tracking data from 40 patients undergoing radiosurgery.
- Convolution of 1D dose profiles with breathing probability density functions (PDFs) to assess dose blurring.
- Modeling breathing motion using Gaussian distributions.
Main Results:
- Required safety margin is a nonlinear function of peak-to-peak breathing motion.
- Breathing motion up to 10 mm results in minimal shift of isodose curves.
- For motions of 20-30 mm, gating or breath-hold can reduce margins by 7-12 mm.
- Random setup uncertainties have minimal impact on margins needed for breathing motion.
Conclusions:
- Breathing motion control is essential for reducing safety margins in radiosurgery, particularly for larger motions.
- Gaussian modeling of breathing motion provides a practical approach for margin calculations.
- One-dimensional analysis primarily applies to the superior-inferior direction.