Anti-scatter grid performance in digital mammography and contrast-enhanced mammography: a Monte Carlo study

<i>Objective.</i>Digital mammography (DM) and dual-energy contrast-enhanced mammography (CEM) use the same anti-scatter grid, despite their differences in x-ray spectra. This study investigated grid performance under clinically relevant conditions in DM and CEM across representative ranges of patient characteristics and assessed the effect of increased grid ratior.<i>Approach.</i>Monte Carlo simulations of low-energy (LE) and high-energy (HE) images of a clinical DM/CEM system were performed using realistically shaped compressed breast phantoms with varying thickness, size, and composition. Linear grids withr= 5, 10, 15, and 20 were simulated. Grid performance was measured via the signal-difference-to-noise-ratio (SDNR) improvement factor (SIF), and differences in spatial scatter distributions were assessed via scatter-to-primary ratio (SPR) profiles.<i>Main results.</i>Breast composition had no considerable impact on grid performance for DM or CEM. SIF increased with breast size by an average of 1.3% (LE) and 6.9% (HE), and with breast thickness by 21%-30% (LE) and 19%-27% (HE). The standard grid (r=5) did not reduce SDNR in LE or HE images for the examined thickness range (30-90 mm). Higher grid ratios improved SPR homogeneity between LE and HE images in the inner projected breast area. A grid withr=10yielded up to 4% higher SIF at the centre of mass thanr=5in HE images, while causing a maximum SDNR loss of 3.5% for 30 mm thick breasts in LE images.<i>Significance.</i>This study provides clinically relevant measures of grid performance in DM and CEM, closing a gap on missing insights of breast size effects. Contrary to previous findings, SDNR is not necessarily degraded for thin breasts under standard imaging conditions. Increasing the grid ratio tor=10improves HE image quality and might reduce rim artifacts in CEM due to increased SPR homogeneity, with minimal SDNR loss in DM.