Performance of automatic exposure control on dose and image quality: comparison between slot-scanning and flat-panel digital radiography systems
Résumé
Background: EOSedge™a (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 in patients.
Purpose: This study aims at characterizing EOSedge organ dose deposition in comparison to a Digital Radiography (DR) system and the previous EOS system (EOS-1st generation), in relation to their respective image quality levels.
Method: Organ doses were measured in an anthropomorphic female adult phantom and a 5 years old pediatric phantom using Optically Stimulated Luminescence dosimeters (OSL), which were carefully calibrated within the studied energy range. Organ doses were recorded on the EOSedge and the Fuji Visionnary 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 DR system.
Results: For a Full-Spine exam, and on the female adult phantom (resp. the pediatric phantom), an effective dose of 92 μSv (resp. 32 μSv) was obtained on EOSedge, and 572 μSv (resp. 179 μSv) on the DR system; these values were compared to effective dose values of 290 μSv (resp. 200 μSv) from the literature on EOS-1st generation, leading to an effective dose reduction factor of 6 with respect to the DR system, and of 3 to 6 with respect to EOS-1st generation. 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 cm to 40 cm of poly(methyl methacrylate) (PMMA). Within this range, EOSedge is also comparable to DR for 10 cm and 20 cm of PMMA, and better than DR for 30 cm and 40 cm 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 tested modalities.
Conclusion: 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-axis images.
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