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Intrafractional motion of the prostate during hypofractionated radiotherapy
Yaoqin Xie1, David Djajaputra, Christopher R King
1Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305-5847, USA.
International Journal of Radiation Oncology, Biology, Physics
|August 30, 2008
Summary
Prostate motion during CyberKnife radiotherapy can be managed with real-time monitoring. A sampling rate of 40 seconds between X-rays is generally sufficient for submillimeter tracking, though individual variations may require adjustments.
Area of Science:
- Radiation Oncology
- Medical Physics
- Prostate Cancer Treatment
Background:
- Hypofractionated radiotherapy for prostate cancer requires precise tumor targeting.
- CyberKnife utilizes stereoscopic X-ray imaging and fiducial markers for real-time prostate position monitoring.
- Accurate tracking is crucial to minimize radiation dose to surrounding healthy tissues.
Purpose of the Study:
- To characterize prostate motion during CyberKnife treatment using stereoscopic X-ray imaging.
- To evaluate the effectiveness of fiducial marker tracking for prostate repositioning.
- To determine optimal imaging parameters for hypofractionated prostate radiotherapy.
Main Methods:
- Retrospective analysis of 21 prostate cancer patients treated with CyberKnife.
- Monitoring of implanted gold fiducial markers via stereoscopic X-ray imaging.
- Calculation of prostate deviations between consecutive couch motions.
Main Results:
- Analysis of 427 datasets and 4,439 X-ray images.
- Prostate motion exceeding 2 mm occurred in 5% of datasets at 30 seconds, increasing to 14% at 120 seconds.
- Significant inter-patient variability in prostate motion patterns was observed.
Conclusions:
- Real-time monitoring and intervention effectively manage prostate shifts within CyberKnife's tracking range.
- An average X-ray sampling rate of 40 seconds is adequate for submillimeter prostate tracking.
- Individual patient monitoring and potentially higher sampling rates are necessary due to motion variability.
