Optimization of Digital Subtraction Mammography Using Monte Carlo Simulation of the Imaging Chain

Abstract

The aim of this work was to search for the optimal x-ray tube voltage (20–55 kV) and anode-filter combination (Mo/Rh, Rh/Cu, W/Cu) for digital iodine subtraction mammography. The optimum was defined as the combination minimizing the average glandular dose, AGD, for a fixed signal- to-noise ratio, SNR, for detecting an iodine contrast detail. For a 4 cm thick breast (50% glandularity) and conventional Mo/25µmRh spectrum, two shallow dose-minima were found at 28 kV and 47 kV. Using W/0.3mmCu, two local minima were also found at 23 kV and 46 kV; the AGD at the higher tube voltage was significantly lower and results in 3.8 times lower AGD (for SNR=5) than the Mo/Rh combination. The results for Rh/0.3mmCu are similar to W/Cu. The dose advantage using copper filtration is larger for thicker breasts. We conclude that an increase in tube voltage and added Cu-filtration will result in significant dose-advantage in digital iodine subtraction mammography.