Rodrigo Trevisan Massera1, Alessandra Tomal2. 1. Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859 Campinas, Brazil. 2. Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859 Campinas, Brazil. Electronic address: atomal@ifi.unicamp.br.
Abstract
PURPOSE: To quantify the influence of different skin models on mammographic breast dosimetry, based on dosimetric protocols and recent breast skin thickness findings. METHODS: By using an adapted PENELOPE (v. 2014) + PenEasy (v. 2015) Monte Carlo (MC) code, simulations were performed in order to obtain the mean glandular dose (MGD), the normalized MGD by incident air Kerma (DgN), and the glandular depth dose (GDD(z)). The geometry was based on a cranio-caudal mammographic examination. Monoenergetic and polyenergetic beams were implemented, for a breast thickness from 2 cm to 9 cm, with different compositions. Seven skin models were used: a 5 mm adipose layer; a skin layer ranging from 5 mm to 1.45 mm, a 1.45 mm skin thickness with a subcutaneous adipose layer of 2 mm and 3.55 mm. RESULTS: The differences, for monoenergetic beams, are higher (up to 200%) for lower energies (8 keV), thicker and low glandular content breasts, decreasing to less than 5% at 40 keV. Without a skin layer, the differences reach a maximum of 1240%. The relative difference in DgN values for 1.45 mm skin and 5 mm adipose layers and polyenergetic beams varies from -14% to 12%. CONCLUSIONS: The implemented MC code is suitable for mammography dosimetry calculations. The skin models have major impacts on MGD values, and the results complement previous literature findings. The current protocols should be updated to include a more realistic skin model, which provides a reliable breast dose estimation.
PURPOSE: To quantify the influence of different skin models on mammographic breast dosimetry, based on dosimetric protocols and recent breast skin thickness findings. METHODS: By using an adapted PENELOPE (v. 2014) + PenEasy (v. 2015) Monte Carlo (MC) code, simulations were performed in order to obtain the mean glandular dose (MGD), the normalized MGD by incident air Kerma (DgN), and the glandular depth dose (GDD(z)). The geometry was based on a cranio-caudal mammographic examination. Monoenergetic and polyenergetic beams were implemented, for a breast thickness from 2 cm to 9 cm, with different compositions. Seven skin models were used: a 5 mm adipose layer; a skin layer ranging from 5 mm to 1.45 mm, a 1.45 mm skin thickness with a subcutaneous adipose layer of 2 mm and 3.55 mm. RESULTS: The differences, for monoenergetic beams, are higher (up to 200%) for lower energies (8 keV), thicker and low glandular content breasts, decreasing to less than 5% at 40 keV. Without a skin layer, the differences reach a maximum of 1240%. The relative difference in DgN values for 1.45 mm skin and 5 mm adipose layers and polyenergetic beams varies from -14% to 12%. CONCLUSIONS: The implemented MC code is suitable for mammography dosimetry calculations. The skin models have major impacts on MGD values, and the results complement previous literature findings. The current protocols should be updated to include a more realistic skin model, which provides a reliable breast dose estimation.
Authors: Christian Fedon; Carolina Rabin; Marco Caballo; Oliver Diaz; Eloy García; Alejandro Rodríguez-Ruiz; Gabriel A González-Sprinberg; Ioannis Sechopoulos Journal: Phys Med Biol Date: 2018-12-19 Impact factor: 3.609