mA·s
Product of tube current (mA) and exposure time (seconds). The primary exposure parameter in radiography and the core dose driver. CT systems modulate mA·s dynamically per slice based on patient attenuation and protocol.
Why it matters to buyers: Directly proportional to dose and to image signal. Dose-reduction strategies aim to reduce mA·s while maintaining diagnostic image quality, primarily through dose-modulation software (CT-AEC, automatic exposure control on radiography) and iterative / DL recon.
Why it matters to engineers: Accumulated mA·s over a tube's life is the truest wear metric — better than calendar hours or scan count. Tube manufacturers spec lifetime in scan exposures or mA·s rather than years.