Radiation doses in mammography exams: Effects of oncological treatments

Abstract

IntroductionBreast cancer treatments cause breast changes that are detectable in subsequent mammography exams. This work investigates if these changes are perceived as differences in breast composition by automatic exposure systems, and if such differences are high enough to have impact in exam doses. MethodsData was obtained for 226 patients treated with unilateral conservative surgery followed by radiotherapy (S&RT) of the left (114) or right (112) breast, who had mammographic exams in direct digital GE units, Senographe DS (SenoDS) or Senographe Essential (Essential). The relevant data was extracted from Digital Imaging and Communications in Medicine (DICOM) images, and the Mean Glandular Dose (MGD) was calculated using the model of Dance. ResultsCompression force and area were 15–30% lower for treated breasts (S&RT) relative to untreated, while compressed breast thickness (CBT), incident air kerma (Ki) and MGD were 14–17%, 22–28% and 10–18% higher, respectively. The variation of MGD and Ki with CBT is similar for treated and untreated breasts. High values of Ki, MGD and CBT occur for some treated breasts with relatively small areas, probably as a result of less compressible breast tissue. Equipment-determined composition was found to be similar for treated and untreated breasts. ConclusionTreated breasts are imaged with slightly higher doses as a result of higher CBT, but the dependence of Ki and MGD on CBT remains unchanged. There is no need to separate data for treated and untreated breasts in large-scale analysis of exam doses.