Automatic exposure control

Last revised by Andrew Murphy on 9 Mar 2023

Automatic exposure control (AEC) is incorporated into radiographic and mammographic imaging systems. Its function automatically terminates exposure when a preset amount of radiation has been detected.

Automatic exposure control systems help to provide a consistent optical density/signal-to-noise ratio between images, regardless of patient-centric factors such as size and density.

Automatic exposure control systems also help to reduce 'dose creep' that can occur with inadvertent radiation overexposure by the technologist.

The first generation of automatic exposure control systems are phototimers, which are now largely superseded by ionization chambers.

In radiography, the automatic exposure control device is placed in front of the image receptor. In mammography, the automatic exposure control device is placed underneath the image receptor.

Related (though discrete) principles include automatic brightness control (ABC) in fluoroscopy and tube current modulation in CT.

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