Table 3.

Summary of the four most common automatic exposure control strategies.

Manufa cturer	AEC trade name	Image quality reference	Goal
General Electric	Auto mA, Smart mA	Noise index	Maintain a constant noise level (defined in noise index), using tube currents within prescribed minimum and maximum values
Toshiba	SureExposure	Standard deviation (high quality, standard, low dose)	Maintain a constant noise level (defined in standard deviation values for each protocol), using tube currents within preset minimum and maximum values
Siemens	CARE Dose4D	Quality reference mAs	Maintain the same image quality (varying noise target for different attenuation level) with reference to a target effective mAs level for a standard- sized patient
Philips	DoseRight	Reference image	Keep the same image quality as in the reference image, regardless of attenuation level

AEC: Automatic exposure control; mAs: Product of tube current and rotation time.