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Tracking the dose distribution in radiation therapy by accounting for variable anatomy
B Schaly1, J A Kempe, G S Bauman
1Radiation Treatment Program, London Regional Cancer Centre, 790 Commissioners Rd E, London, ON, N6A 4L6, Canada.
Physics in Medicine and Biology
|April 9, 2004
Summary
This study tracks moving tissue elements (voxels) during radiotherapy to calculate actual radiation doses. Results show significant dose differences in organs like the rectum and bladder due to patient anatomy changes.
Area of Science:
- Medical Physics
- Radiotherapy
- Image Analysis
Background:
- Accurate radiation dose calculation is crucial in radiotherapy.
- Patient anatomy can vary during treatment, affecting delivered dose.
- Conventional treatment planning may not account for intra-fraction motion.
Purpose of the Study:
- To develop and validate a method for calculating daily and cumulative dose distributions considering patient anatomical variations.
- To quantify dose differences resulting from voxel motion during radiotherapy.
- To assess the potential for adaptive radiotherapy guided by actual delivered doses.
Main Methods:
- Utilized non-linear image registration (thin-plate splines) to track voxel motion.
- Integrated dose distributions from multiple 3D computed tomography (CT) scans.
- Combined registration with a conventional treatment planning system.
Main Results:
- Demonstrated significant localized dose differences in a clinical prostate case due to voxel motion.
- Observed largest positive dose differences in rectum (29%), bladder (2%), and seminal vesicles (24%) after the first fraction.
- Found largest positive dose differences after 15 fractions in rectum (23%), bladder (32%), and seminal vesicles (18%).
Conclusions:
- The developed method accurately calculates delivered radiotherapy doses accounting for anatomical changes.
- Voxel motion leads to substantial dose variations in critical organs.
- This approach offers quantitative insights for guiding adaptive radiotherapy strategies.