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Toward correcting drift in target position during radiotherapy via computer-controlled couch adjustments on a
Joseph E McNamara1, Rajesh Regmi, D Michael Lovelock
1Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
Medical Physics
|May 3, 2013
Summary
This study introduces a novel method for real-time radiation therapy, predicting and correcting respiratory target motion using couch adjustments. This approach significantly reduces breathing-related positional errors, enhancing treatment accuracy.
Area of Science:
- Medical Physics
- Radiation Oncology
- Image-Guided Therapy
Background:
- Real-time tracking of respiratory target motion in radiation therapy is complex due to unpredictable breathing patterns.
- Accurate patient positioning is crucial for effective radiation delivery and minimizing off-target dose.
Purpose of the Study:
- To develop and evaluate a method for predicting and correcting respiration-averaged target position drift during radiation therapy.
- To utilize couch adjustments on a capable accelerator to compensate for breathing-induced motion.
Main Methods:
- Dose delivery segmented into 10s fields with subsequent couch adjustments based on external breathing motion monitoring.
- Signal averaging over three respiratory cycles determined target drift, with a Kalman filter predicting baseline position 5s ahead for couch correction.
- Feasibility tested using a motion phantom and evaluated in 10 patient cases (hypofractionated treatment and CT simulation).
Main Results:
- Successfully reduced root-mean-squared deviation (RMSD) of baseline position from planned position in all 10 cases.
- Mean RMSD decreased from 4.9 mm to 1.7 mm post-correction.
- Treatment time increased by approximately 5% compared to treatments without motion correction.
Conclusions:
- Periodic couch position adjustments during treatment can significantly reduce baseline respiratory drift.
- This method demonstrates potential for improving accuracy in radiation therapy for moving targets.
- Future advancements may allow for real-time, "on-the-fly" couch adjustments during treatment delivery.
