Geometric factor analysis for dose distribution in the whole breast irradiation

Abstract

Abstract Background Protecting the heart and left lung is important for left-sided breast cancer radiotherapy. So，this study was to investigate the effect of geometric parameters on the dose of left lung and heart in whole breast radiotherapy. Methods A plan was designed for each patient using VMAT technology for thirty patients. A triangular ABC of the target was defined layer by layer. The geometric parameters were defined: Rat-H (the ratio of heart), Rat-L (the ratio of lung), the curvature and thickness of the target ρ and d. Explored the relationships between these parameters and the dose-volume of heart (V5,h, V10,h, V20,h, MHD) and left lung (V5,LL, V10,LL, V20,LL, V30,LL, V40,LL, MLD). Results The V5,h, V10,h and MHD were all significantly associated with Rat-H (p<0.05). The V5,LL, V10,LL, V20,LL, V30,LL, V40,LL and MLD were all significantly associated with Rat-L (p<0.05). And the V20,LL, V30,LL and V40,LL were all significantly associated with d (p<0.05). Meanwhile，V30,LL and V40,LL were all significantly associated with ρ (p<0.05) . The correlations of the dose-volume of left lung and the four geometric parameters could be expressed by linear functions. Conclusions The geometric parameters Rat-H, Rat-L, d and ρ were closely related to the dose-volume of heart and left lung in whole breast radiotherapy.