GE Smart mA

GE introduced Smart mA in 1994 and was the first CT manufacturer to provide scanners with Automatic Exposure Control –a major step forward in managing patient dose.
The LightSpeed VCT offers the Smart mA system, which combines both z-axis and angular tube current modulation to adjust the dose to the size and shape of individual patients – accounting for all three dimensions.

Prior to scanning, the user selects the desired image quality, or noise index. Based on a single scout scan, the system adjusts the exposure during the CT scan to achieve that level of acceptable noise across the region of interest. Similar to cruise control on a car, the system increases and decreases the mA as it encounters various anatomy thicknesses and asymmetries.

Compared with using a fixed mA, Smart mA can reduce patient dose by as much as 32.5% while maintaining consistent image quality.


ECG gating also can be used to modulate the mA during the heart cycle to achieve up to 50% dose reductions on many cardiac studies. ECG modulation takes advantage
of the fact that cardiac motion is generally greatest during the systolic phase and only applies full tube current to the patient when imaging during the diastolic period where motion is minimal.