What aspect of the filament does mA regulate?

The milliampere (mA) setting is crucial in regulating the heating of the filament within an X-ray tube. When the mA is increased, more electric current flows through the filament, which results in a higher temperature. This elevated temperature is essential because it causes the filament to emit more electrons through a process known as thermionic emission. These emitted electrons are then used to generate X-rays when they interact with the target in the tube. The amount of heating directly correlates with the number of X-rays produced during an exposure, making the regulation of mA fundamental in controlling the overall output of the X-ray machine.

The other aspects mentioned, such as cooling, termination of exposure, and detection of radiation, are influenced by different factors and settings within the X-ray system, but they are not directly controlled by mA.