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Prolonged treatment time deteriorates positioning accuracy for stereotactic radiosurgery.
Chun-Wei Wang1, Yin-Chun Lin2, Ham-Min Tseng3
1Division of Radiation Oncology, Departments of Oncology, National Taiwan University Hospital, Taipei, Taiwan; Department of Radiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Plos One
|April 21, 2015
Summary
Intracranial radiosurgery shows increased patient motion over time, particularly in the superior-inferior direction. Longer treatments exceeding 15 minutes necessitate larger planning target volume margins for precision.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Oncology
Background:
- Accurate radiation delivery is crucial in advanced radiotherapy.
- Intracranial radiosurgery demands precise targeting to minimize damage to healthy tissue.
Purpose of the Study:
- To evaluate intrafractional motion during intracranial radiosurgery.
- To investigate the relationship between motion changes and treatment duration.
Main Methods:
- Retrospective analysis of 50 CyberKnife Radiosurgery System treatment records (5988 images).
- Measurement of translational (SI, RL, AP) and rotational motion over 45 minutes.
- Data grouped into 15-minute intervals (0-15, 16-30, 31-45 min) to assess time-dependent changes.
Main Results:
- Mean deviations remained below 0.1 mm in the first 15 minutes.
- Significant increase in 3D vector motion over time (0.34 mm to 0.77 mm, p=0.01), especially in the SI direction.
- Longer treatment times correlated with increased systematic error, impacting planning target volume (PTV) margins.
Conclusions:
- Consistent increase in positioning deviation observed during intracranial radiosurgery, particularly in the SI direction.
- Recommend increased PTV margins for treatments exceeding 15 minutes to maintain accuracy.
- Findings emphasize the importance of considering treatment time in radiosurgery planning.
