Brachyvision treatment planning system

High-dose-rate brachytherapy was done using ¹⁹²Ir source of 370 GBq initial activity with GammaMed HDR Plus afterloading machine (Varian Medical Systems, Inc., Palo Alto, CA, USA). Target definition and delineation was done according GEC-ESTRO Breast Cancer Working Group recommendations [26 (link)]. Post implantation CT images were transferred to BrachyVision treatment planning system (Varian Medical Systems, Inc., Palo Alto, CA, USA), on which the target volume segmentation and planning was performed. After the tumor bed was identified, a margin of 1.5 cm was uniformly expanded while keeping a minimum distance of 5 mm from the skin surface to create a CTV. Posteriorly, the CTV did not expand to the chest wall muscles. Planning target volume (PTV) was the same as CTV. After catheters’ reconstruction, a geometrical optimization with subsequent manual modification of the dwell times and positions was done to achieve homogenous dose distribution among the CTV. The aimed dose constraints for the plan were: V₁₀₀ for CTV > 90%, dose non-homogeneity ratio (DNR, relation of volume received 150% of prescribed dose to the volume received 100% of prescribed dose, V₁₅₀/V_100%) was ≤ 0,33, and the dose to the skin surface and chest wall ≤ 70% of prescribed dose. Twenty two patients received 8 times 4 Gy, and twenty six patients 7 times 5 Gy fractions.