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Sci‐Thur PM – Brachytherapy 03: Identifying the impact of seroma visualization on permanent breast seed implant brachytherapy
Author(s) -
Morton Daniel,
Batchelar Deidre,
Hilts Michelle,
TetreaultLaflamme Audrey,
Mou Benjamin,
Lucas Sarah,
Crook Juanita
Publication year - 2016
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 - 10.1118/1.4961771
Subject(s) - seroma , medicine , brachytherapy , nuclear medicine , implant , concordance , radiology , radiation therapy , surgery , complication
Purpose: Uncertainties in target identification can reduce treatment accuracy in permanent breast seed implant (PBSI) brachytherapy. This study evaluates the relationship between seroma visualization and seed placement accuracy. Methods: Spatially co‐registered CT and 3D ultrasound (US) images were acquired for 10 patients receiving PBSI. Seromas were retrospectively contoured independently by 3 radiation oncologists on both CT and US and respective consensus volumes were defined, CTV CT and CTV US . The seroma clarity and inter‐user conformity index (CI), as well as inter‐modality CI, volume, and positional differences were evaluated. Correlations with seed placement accuracy were then assessed. CTVs were expanded by 1.25cm to create PTV CT and PTV US and evaluate the conformity with PTV Clinical (CTV Clinical +1.25cm) used in treatment planning. The change in PTV coincidence by expanding PTV Clinical by 0.25cm was determined. Results: CTV US were a mean 68 ± 12% smaller than CTV CT and generally had improved clarity and inter‐user conformity. No correlations between seed displacement and CTV US ‐CTV CT positional difference or CI were observed. Greater seed displacements were associated with larger CTV US ‐CTV CT volume differences (r=−0.65) and inter‐user CT CI (r=−0.74). A median (range) 88% (71–99%) of PTV CT and 83% (69–100%) of PTV US were contained within PTV Clinical . Expanding treatment margins to 1.5cm increased coincidence to 98% (86–100%) and 94% (82–100%), respectively. Conclusions: Differences in seroma visualization impacts seed displacement in PBSI. Reducing dependence on CT by incorporating 3DUS into target identification, or expanding CT‐based treatment margins to 1.5cm may reduce or mitigate uncertainties related to seroma visualization.