Thyroid and contralateral breast surface dose variation in mammography: a phantom study on the role of breast tissue composition

Abstract

The organs of the thyroid and contralateral breast can be exposed to radiation because of scattered x-rays during mammography. It is important to determine the dose values of these quantities in terms of the risk of triggering a second cancer induction for both organs. In the present study, thyroid and contralateral breast surface doses were investigated with LiF:Mg,Ti (TLD-100) dosimeters for three types of BR-12 phantoms with glandularity/fat tissue ratios (70%/30%, 50%/50% and 30%/70%) over four views as in the real patient situation in Mo/Mo and Mo/Rh anode/filter combinations in each phantom thickness as opposed to a single glandular/fat tissue commonly used in the literature. Both thyroid and contralateral surface doses increased with increasing both phantom thickness and glandularity/fat ratio. The thyroid surface doses changed within 0.06–0.18 mGy and 0.05–0.14 mGy according to phantom thickness of 2 to 6 cm for the glandularity/adipose of 50%/50% in the Mo/Mo and Mo/Rh, respectively. On the other hand, the contralateral breast surface doses were within 0.35–1.39 mGy and 0.40–0.99 mGy for 50%/50% in the Mo/Mo and Mo/Rh, respectively. Based on a 70%/30% breast composition with a phantom thickness of 6 cm, the thyroid and contralateral breast surface doses increased by approximately 40% compared with 50%/50% for both Mo/Mo and Mo/Rh. These results showed that both thyroid and contralateral breast surface doses significantly depend on the glandularity/fat composition of the breast. Therefore, the outputs of this study may contribute to future studies aimed at reducing the doses received by organs during examination.