Incorporating three-dimensional ultrasound into permanent breast seed implant brachytherapy treatment planning

作者：Morton Daniel^*; Batchelar Deidre; Hilts Michelle; Berrang Tanya; Crook Juanita

来源：Brachytherapy, 2017, 16(1): 167-173.

DOI：10.1016/j.brachy.2016.09.007

• Permanent breast seed implants
• Breast brachytherapy
• Accelerated partial breast irradiation
• 3D ultrasound
• Seroma
• Treatment planning

PURPOSE: Planning permanent breast seed implant (PBSI) brachytherapy using CT alone may reduce treatment accuracy because of differences in seroma visualization compared with ultrasound (US). This study evaluates dosimetric effects of seroma delineation in PBSI and the potential impact of incorporating three-dimensional (3D) US into PBSI treatment planning.
METHODS AND MATERIALS: Spatially coregistered CT and 3D US images from 10 patients were retrospectively analyzed to simulate the PBSI procedure. Seromas contoured on CT and US defined clinical target volumes, CTVcT and CTVus, which were expanded to create planning target volumes (PTVs). PBSI plans were generated using PTVcT alone, and the resulting coverage to PTVus was evaluated. To assess the potential impact of transferring to an US-guided procedure, the CT-based plans were centered on CTVus. The volume encompassed by both PTVs was used to evaluate how 3D US can affect the planning procedure.
RESULTS: Median (range) PTVcr V-100 was 95.6% (93.3-97.3%), resulting in PTVs coverage of 91.5% (80.5-97.9%). Centering plans on CTVus decreased PTVer V-100 by a mean of 10 +/- 8%, and increased PTVus V-100 by 5 +/- 4%. The combined PTVs were a mean 9 +/- 6% larger than PTVcr. Acceptable dosimetry to the combined PTVs resulted in sufficient coverage to individual PTVs but with a mean 11 +/- 24% increase to skin dose and 6 +/- 8% increase in breast V-200.
CONCLUSIONS: Differences in seroma visualization have dosimetric effects in PBSI. CT-based plans can underdose US-defined volumes and may not adequately translate to an US-guided procedure. Implementing 3D US into planning can potentially compensate for differences in delineation.

• 出版日期2017-2