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Comparison of CT scatter rejection effectiveness using antiscatter grids and energy-discriminating detectors

A potential application for energy-discriminating detectors (EDD) is scatter rejection in CT. If paired with a monoenergetic source, EDDs can identify scattered photons by their reduced energy relative to primary photons. However, it is unknown how the scatter rejection of an EDD compares with that of an antiscatter grid. In this study, the scatter rejection efficiency of energy-integrating detectors (EIDs) with antiscatter grids was compared with that of EDDs. Monte Carlo simulations were performed to generate projection images of head and body-sized cylindrical water phantoms in a typical clinical CT scanner geometry and a non-traditional geometry in which antiscatter grids would be impossible to install. Eight different detectors were used: four EIDs with 1D antiscatter grids of different heights (between 1 mm and 20 mm) and four EDDs with different energy bin sizes (between 0.1 keV and 10 keV.) Different source energy spectra were also investigated. Scatter to primary ratio (SPR) was calculated for each setup. The results showed that most antiscatter grid setups outperformed EDD setups. In the traditional CT geometry, the EDD with a 0.1 keV energy bin size produced slightly better SPR than a 5-mm-tall antiscatter grid, but the more realistic 1 keV energy bin EDD outperformed only a 1-mm-tall grid. However, the EDDs significantly reduced the SPR in the non-traditional geometry in which it was impossible to install antiscatter grids. The results suggest that EDDs are unlikely to outperform antiscatter grids in scatter rejection but could be useful when antiscatter grids are impossible to install.