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Rapid emission angle selection for rotating‐shield brachytherapy
Author(s) -
Liu Yunlong,
Flynn Ryan T.,
Yang Wenjun,
Kim Yusung,
Bhatia Sudershan K.,
Sun Wenqing,
Wu Xiaodong
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4802750
Subject(s) - brachytherapy , azimuth , dosimetry , shield , optics , aperture (computer memory) , monte carlo method , volume (thermodynamics) , materials science , nuclear medicine , electromagnetic shielding , physics , radiation therapy , geology , acoustics , mathematics , medicine , surgery , petrology , statistics , quantum mechanics , composite material
Purpose: The authors present a rapid emission angle selection (REAS) method that enables the efficient selection of the azimuthal shield angle for rotating shield brachytherapy (RSBT). The REAS method produces a Pareto curve from which a potential RSBT user can select a treatment plan that balances the tradeoff between delivery time and tumor dose conformity.Methods: Two cervical cancer patients were considered as test cases for the REAS method. The RSBT source considered was a Xoft Axxent TM electronic brachytherapy source, partially shielded with 0.5 mm of tungsten, which traveled inside a tandem intrauterine applicator. Three anchor RSBT plans were generated for each case using dose‐volume optimization, with azimuthal shield emission angles of 90°, 180°, and 270°. The REAS method converts the anchor plans to treatment plans for all possible emission angles by combining neighboring beamlets to form beamlets for larger emission angles. Treatment plans based on exhaustive dose‐volume optimization (ERVO) and exhaustive surface optimization (ERSO) were also generated for both cases. Uniform dwell‐time scaling was applied to all plans such that that high‐risk clinical target volume D 90 was maximized without violating the D 2cc tolerances of the rectum, bladder, and sigmoid colon.Results: By choosing three azimuthal emission angles out of 32 potential angles, the REAS method performs about 10 times faster than the ERVO method. By setting D 90 to 85–100 Gy 10 , the delivery times used by REAS generated plans are 21.0% and 19.5% less than exhaustive surface optimized plans used by the two clinical cases. By setting the delivery time budget to 5–25 and 10–30 min/fx, respectively, for two the cases, the D 90 contributions for REAS are improved by 5.8% and 5.1% compared to the ERSO plans. The ranges used in this comparison were selected in order to keep both D 90 and the delivery time within acceptable limits.Conclusions: The REAS method enables efficient RSBT treatment planning and delivery and provides treatment plans with comparable quality to those generated by exhaustive replanning with dose‐volume optimization.