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Position-dependent offset corrections for ring applicator reconstruction in cervical cancer brachytherapy
Leon G Aldrovandi1, Matthias E T Dessein1, Shelley M Pearson2
1Radiation Treatment, Wellington Blood and Cancer Centre, Newtown, Wellington, New Zealand.
Journal of Applied Clinical Medical Physics
|March 19, 2025
Summary
Position-dependent corrections significantly improve accuracy for ring applicators in brachytherapy. Two methods effectively corrected source positioning errors, ensuring precise radiation delivery.
Area of Science:
- Medical Physics
- Radiation Oncology
- Brachytherapy
Background:
- Ring applicators in brachytherapy can have significant positioning errors due to their design.
- Standard global offset corrections may not meet required tolerances for these errors.
Purpose of the Study:
- To investigate two methods for applicator reconstruction with position-dependent source offset corrections.
- To assess the effectiveness of these methods in improving source positioning accuracy.
Main Methods:
- Measurements using Varian Interstitial PEEK Ring 60° and BRAVOS afterloader.
- Source positioning characterized via autoradiographs and planar kV images.
- Two position-dependent correction methods: local radius modification and bidirectional source movement simulation.
Main Results:
- Autoradiographs revealed quasi-linear dwell position offsets, up to 3 mm at the ring's end.
- kV images confirmed effective radius 0.5 mm larger than nominal.
- Both methods reduced residual positioning errors to a mean of 0.0 (±0.3) mm.
Conclusions:
- Position-dependent source offset corrections successfully corrected applicator positioning errors.
- The manufacturer-recommended method offered simpler implementation and broader applicability.
- Accurate source positioning is crucial for effective brachytherapy treatment.
