Basic Radiation Physics
Beam Quantity

The amperage and the exposure time determine the number of electrons passing through the cathode filament. Increasing the amperage or exposure time will increase the number of photons generated in the x-ray tube. Since the amperage and the exposure time directly influence the number of photons emitted, they form a common factor called the milliampere-seconds (mAs). When we increase one of these two factors, we must decrease the other settings to maintain the same beam quantity (Figure 6).^1,2,3,4,9