What is automatic exposure control (AEC), and what is its main benefit?

• A. Increases exposure to maximize detector signal.
• B. Automatic exposure control terminates exposure when the detector signal reaches a preset level, ensuring consistent receptor exposure and reducing repeats.
• C. Reduces patient dose by halting after a fixed time regardless of detector signal.
• D. Relies on manual timing and never terminates exposure.

Answer: (B)

Automatic exposure control uses detectors placed behind or near the image receptor to monitor the amount of X-ray energy reaching the detector. When the signal reaches a pre-set level that provides adequate receptor exposure, the exposure is terminated. The main benefit is delivering a consistent amount of exposure to the image receptor across different patients and body parts, which reduces image repeats and helps keep patient dose more predictable. It adapts to variations in patient size, part thickness, and positioning, so technique doesn’t have to be guessed manually. It does not aim to maximize exposure, nor rely on a fixed timer, nor require manual timing.