Ponente
Descripción
Contrast-enhanced mammography (CEM) has become an important breast imaging technique because it combines the anatomical information of digital mammography with functional information associated with iodinated contrast uptake. However, the use of higher tube voltages, copper-based filtration and dual-energy acquisition introduces additional dosimetric challenges, especially regarding the estimation of mean glandular dose (MGD) ) (Neeter, L.M.F.H. et al., BJR Open 3, 20210034, 2021). This study investigated the application of the egs_kerma application from the EGSnrc Monte Carlo system for estimating air kerma and dose-related quantities in digital and contrast-enhanced mammography. X-ray spectra for conventional digital mammography were generated using Siemens X-Ray Toolbox Mammography, while CEM spectra were produced with SpekPy. The simulations were performed with EGSnrc v2023a. The breast was modeled as a semicylindrical phantom with 90 mm radius and compressed thicknesses of 20, 45 and 60 mm, corresponding to glandular fractions of 75%, 50% and 25%, respectively (Dance, D.R., Phys. Med. Biol. 35, 1211–1219, 1990). For the CEM model, iodinated contrast was represented as a layer within the breast volume. The evaluated anode/filter combinations included Mo/Mo, Rh/Rh and W/Rh for digital mammography, and W/Cu, Mo/Cu and Rh/Al+Cu for CEM. Air kerma, mean breast dose and MGD estimates were obtained and compared with conversion coefficients and reference data from the literature. For digital mammography, the egs_kerma simulations reproduced physically consistent trends for air kerma and MGD, with satisfactory agreement for several anode/filter combinations, particularly Rh/Rh and W/Rh under selected conditions. For CEM, simulated air kerma values showed internal consistency among spectra, ranging from 11.70 to 12.20 mGy for 20 mm breasts, approximately 6.68 to 6.71 mGy for 45 mm, and 5.27 to 5.33 mGy for 60 mm. Mean breast doses in the contrast model ranged from 0.682 to 0.849 mGy, depending on spectrum and breast thickness. For W/Cu and Mo/Cu, the comparison between simulated mean breast dose and normalized glandular dose factors indicated values of the same order of magnitude, especially for intermediate and larger breast thicknesses. The results suggest that egs_kerma is a useful computational tool for exploratory dosimetric evaluation in mammography and CEM. Although the geometry was initially simplified and contrast distribution do not reproduce clinical MGD exactly, the method provides physically coherent estimates and supports further development of Monte Carlo-supported dosimetry protocols for contrast-enhanced mammography.