Performance of automatic exposure control on dose and image quality: comparison between slot-scanning and flat-panel digital radiography systems.

Abstract

EOSedge™* (EOS Imaging, Paris, France) is an X-ray imaging system using automatic exposure control (AEC) with tube current modulation, in order to optimize dose deposition inpatients. This study aims at characterizing EOSedge organ dose deposition in comparison to a digital radiography (DR) system and the previous EOS system (EOS-1stgeneration), in relation to their respective image qualitylevels. Organ doses were measured in an anthropomorphic female adult phantom and a 5-year-old pediatric phantom using optically stimulated luminescence (OSL) dosimeters, which were carefully calibrated within the studied energy range. Organ doses were recorded on the EOSedge and the Fuji Visionary DRF (Fujifilm Medical Systems U.S.A., Inc, Lexington, MA). The resulting effective doses were compared to the EOS-1st-generation values present in the literature. Image quality assessment was carried out on end-user images. Quantitative image quality metrics were computed for all tested modalities on a quality assurance phantom. Qualitative assessment of EOSedge image quality was based on anthropomorphic phantom acquisitions against the EOS-1st-generation system, and on clinical images against the tested DRsystem. For a full-spine exam, and on the female adult phantom (respectively, the pediatric phantom), an effective dose of 92μSv (respectively, 32μSv) was obtained on EOSedge, and 572μSv (respectively, 179μSv) on the DR system; these values were compared to effective dose values of 290μSv (respectively, 200μSv) from the literature on EOS-1stgeneration, leading to an effective dose reduction factor of 6 with respect to the DR system, and of 3-6 with respect to EOS-1stgeneration. EOSedge provides the best compromise between contrast-to-noise ratio (CNR) and dose, with more consistent CNR values than the other tested modalities, in a range of attenuation from 10 to 40cm of poly(methyl methacrylate) (PMMA). Within this range, EOSedge is also comparable to DR for 10 and 20cm of PMMA, and better than DR for 30 and 40cm of PMMA, both in terms of spatial resolution and low-contrast detection. The anatomical landmarks of interest in the follow-up of spinal deformities can be detected in all testedmodalities. Results showed that EOSedge provides significant dose reduction factors for full spine imaging in both adults and children compared to the other tested modalities, without compromising image quality. We believe that this work could help raise awareness on the capabilities of modern X-ray systems, when equipped with appropriate AEC strategies, to perform ultra-low-dose, long-axisimages.