mA (Milliamperage)
Also written as: mA — Milliamperage
A radiographic exposure parameter expressing the number of electrons produced per second by the X-ray tube, directly controlling the quantity (number) of X-ray photons generated.
Full Definition
Milliamperage (mA) determines the tube current in a dental X-ray unit and governs the quantity of radiation produced—the higher the mA, the more photons generated per unit time and the greater the overall exposure. In dental radiography, mA is often set as a fixed value and combined with exposure time (seconds) to yield milliampere-seconds (mAs), which is the key determinant of image density. Editors of radiographic technique documents must clearly distinguish mA (quantity) from kVp (quality/energy) and from mAs (the product of current and time). Incorrect substitution of these units in a clinical protocol document is a reportable error.
Usage
Usage note: Use lowercase 'm' and uppercase 'A' per SI convention. Do not conflate with mAs (milliampere-seconds), which incorporates exposure time. In editing, flag any document that uses 'milliamps' as a synonym without clarification of whether time is included.
In Context
- "The protocol specified an mA of 7 and an exposure time of 0.16 seconds, yielding an mAs of 1.12." — Radiographic technique protocol
- "Reducing mA rather than kVp is preferred when decreasing patient dose without sacrificing image contrast." — Radiation protection guidelines document