For an abdominal exposure with single-phase equipment using 92 kV and 12 mAs, how much mAs is required for a similar exposure with three-phase, six-pulse equipment?

To determine the mAs required for a similar exposure with three-phase, six-pulse equipment after starting with single-phase equipment, it is important to understand the efficiencies of different types of x-ray generators.

Three-phase, six-pulse equipment typically has a higher output efficiency compared to single-phase equipment due to the continuous voltage waveforms it produces. This results in a more consistent x-ray beam and reduced patient dose while providing comparable image quality.

When using three-phase, six-pulse equipment, a common rule of thumb is that you can reduce the mAs required by approximately 50% compared to single-phase equipment for similar exposures. The initial exposure was set at 12 mAs for the single-phase system.

Consequently, halving 12 mAs (because of the efficiency of three-phase, six-pulse equipment) results in a requirement of 6 mAs for the same exposure conditions. This indicates that the correct answer reflects the need to adjust the mAs accordingly to achieve similar imaging results while accounting for the differences in equipment.

Using this reasoning, the answer of 6 mAs is justified, as it aligns with the typical adjustments made when switching from single-phase to three-phase x-ray systems.