Characterization of Scatter Radiation of a Breast Phantom on Siemens Prototype FFDM with and without an Anti-Scatter Grid

摘要

In this study, the beam stop technique was applied to obtain the scatter fraction values for an anthropomorphic breast phantom on a flat-panel full field mammography system. The phantom was equivalent to a compressed breast of 5 cm thickness with 50% glandular tissue content. The images were acquired at 28kVp with Mo/Mo target/filter combination and multiple mAs values with or without an anti-scatter grid. The one-dimensional and two-dimensional scatter fraction profiles of the breast phantom without a grid were plotted. The effect of mAs on scatter fraction calculation was investigated. It was found that in order to get a reliable measurement of scatter fraction, the mAs had to be above about 40mAs without a grid and 160mAs with a grid. In addition, the SNR values at 28kVp and 80mAs (AEC level for the phantom using the same imaging technique on a screen/film system) with and without a grid were compared with each other. The SNR with a grid was slightly smaller than that without a grid. The SNR improvement factor (K_(SNR)) defined as the ratio of SNR without the grid to SNR with the grid was 0.976. The grid had the primary and scatter transmissions of 73% and 13% respectively.