Automatic exposure control

[3]: 106 In early radiographic AEC systems, a large paddle (17" x 17") of transparent lucite was sandwiched between rare earth screens,[4] which emitted photons when excited by X-rays.

The individual lucite sections were open on one end, and a solenoid was used to select one of three, or a combination of shutters that allowed the generated light into a Photomultiplier tube.

In an iontomat, a weak ionization signal resulting from the radiographic X-rays passing through it are integrated as a ramp shaped voltage waveform.

[6] Modern computed tomography (CT) scanners have AEC systems which aim to maintain image quality for patients of varying sizes, whilst keeping doses as low as reasonably practicable.

[7][8] CT AEC systems use the initial "scanogram", a fixed angle planning view, to determine the relative size of the patient, and variation over their length.

An x-ray image receptor, containing an anti-scatter grid and three AEC regions (represented by dark grey circles and square) These regions represent anatomical areas, e.g. lungs, spine. They can be selected individually, or all at once depending on the need.