Work

Position‐dependent offset corrections for ring applicator reconstruction in cervical cancer brachytherapy

Year: 2025

Type: article

Abstract: PURPOSE: Due to the tight curvature in their design, ring applicators are usually associated with large positioning errors. The standard practice to correct for these deviations based on global offsets may not be sufficient to comply with the recommended tolerance. In this work, we investigate two methods for applicator reconstruction that implement position-dependent source offset corrections. METHODS: Ir sources over a period of 5 months. Additionally, the actual source path was determined by means of a series of planar kV images for different dummy cable positions. The first position-dependent correction method consists of locally modifying the radius of the reconstructed source path according to the measured offsets. The second method, recommended by Varian, simulates a bidirectional movement of the source during applicator reconstruction to compensate for positioning errors. RESULTS: Autoradiographs showed a quasi-linear increase of the dwell position offsets, with a negligible error at the tip and a value close to 3 mm at the end of the ring. This result, consistent with a circular wire movement with an effective radius 0.5 mm larger than the nominal value, was in agreement with the observations from the kV images. After implementation of the position-dependent correction methods, residual positioning errors for the two methods resulted in a mean value (±1 SD) of 0.0 (±0.3) mm, and a range of [-0.7 mm, 0.7 mm]. CONCLUSION: The two tested methods for applicator reconstruction with position-dependent source offset corrections were able to successfully correct the positioning errors. The method recommended by the manufacturer had the additional advantages of a more straightforward implementation and the potential for use in other applicator types.

Source: Journal of Applied Clinical Medical Physics

DOI: 10.1002/acm2.70079

Authors: Leon G. Aldrovandi, Matthias E. T. Dessein, Shelley M. Pearson, Shelley M. Bulling

Institution: Varian Medical Systems (United Kingdom)

Language: English

Topic: Advanced Radiotherapy Techniques

Subfield: Radiation

Field: Physics and Astronomy

Domain: Physical Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $900