Measurement of scatter and evaluation of grid performance for dual-layer flat-panel detector prototype

We are developing a direct-indirect dual-layer flat-panel detector (DLFPD) for motion-free dual-energy (DE) contrast-enhanced digital mammography (CEDM) and digital breast tomosynthesis (CEDBT). Effective suppression of scattered radiation is essential for maximizing image quality and lesion detectability. This study conducts experimental measurements of detector glare in both the amorphous selenium (a-Se) front layer (FL) and cesium iodide (CsI) back layer (BL) detectors of a prototype DLFPD using beam-stop (BS) and pinhole-array (PA) methods. Measurements of scatter from a 4 cm PMMA semi-cylindrical phantom was measured using the PA method. The measured results were compared to our previous estimate with Monte Carlo (MC) simulations. We also measured the impact of an anti-scatter grid (ASG) on scatter. Our results showed reasonable agreement between measured and MC simulated scatter-to-primary ratio (SPR), for both FL and BL detectors. The BL detector sees a slightly higher glare than the FL, which is expected from the additional scatter from the FL detector. The ASG reduces SPR more significantly for the FL than the BL, which is attributed to the decreased scatter rejection efficiency of ASG as x-ray energy increases. Our results indicate that our scatter correction method developed previously using MC simulation may work effectively in a clinical system with integrated DLFPD. We will also investigate different ASG designs in our MC simulation to accommodate all needs of a clinical system.