What unit is used to indicate the total quantity of x-ray exposure delivered?

The total quantity of x-ray exposure delivered is measured in milliampere-seconds, commonly referred to as mAs. This unit represents the product of the tube current (measured in milliamperes, or mA) and the time (in seconds) for which the x-ray tube is active. The mAs value is crucial because it directly influences the amount of ionizing radiation produced during the x-ray exposure. Essentially, a higher mAs leads to more x-ray photons being generated, resulting in a greater exposure to the image receptor.

In relation to the other options, mA indicates the current flowing through the x-ray tube but does not provide a complete measure of exposure because it does not consider the exposure time. kVp, or kilovolt peak, measures the peak voltage applied across the x-ray tube, which primarily affects the quality or energy of the x-rays produced, rather than the quantity. Roentgen is a unit that measures exposure to ionizing radiation, specifically in air, but is less commonly used in modern practice compared to mAs for defining the total quantity delivered during an x-ray procedure.