Evaluation of an Imager-Based Automatic Exposure Control System for Mobile Radiography
Abstract
Purpose
To evaluate the performance of a digital, imager-based automatic exposure control (AEC) system for bedside radiography that uses a low-dose scout image to adaptively select x-ray technique, and to compare its exposure control and image quality performance with conventional ion-chamber AEC.
Methods
Phantom-based experiments were performed to evaluate S-AEC, a detector-based AEC feature of the Samsung GM85 Elite mobile x-ray unit. This system acquires a low-dose scout image, segments the image to identify anatomical regions of interest, and computes the exposure time for the diagnostic acquisition. Polymethyl methacrylate (PMMA) slabs from 0–30 cm thickness in 5 cm increments were imaged using an Abdomen AP Supine processing protocol. Additional acquisitions were performed using quality assurance phantoms (Leeds TOR-18FG, Fuji OneShot) and an anthropomorphic pelvis phantom. Matched measurements were obtained on a conventional radiographic system using ionization chamber–based AEC. For each acquisition, exposure index (EI) relative to a target receptor dose of 2.5 µGy (EI = 250) was recorded. Image quality was quantified using contrast-to-noise ratio (CNR) measurements from standardized regions of interest.
Results
Across PMMA thicknesses and phantom types, S-AEC exposures were within 25% of the target EI for all but the lowest-attenuation conditions. DI values closer to zero indicate EI consistency was superior to that achieved using conventional ion-chamber AEC. For abdomen protocol on each system with 20 cm of PMMA above the Leeds phantom, CNR values were slightly higher for S-AEC compared with the conventional AEC system.
Conclusion
A scout-based, fully digital AEC system for mobile radiography achieved reliable target exposure control and demonstrated improved contrast-to-noise performance relative to conventional ion-chamber AEC. These results suggest that algorithm-driven exposure control may provide a clinically meaningful advantage for portable radiography.