Which factor controls the quantity of photons produced per second during an exposure?

The quantity of photons produced per second during an x-ray exposure is primarily controlled by the milliampere (mA) setting on the x-ray machine. The mA indicates the tube current, which is the amount of electrical current flowing through the x-ray tube. An increase in mA results in a greater number of electrons being released from the cathode, which in turn results in a higher number of x-ray photons being generated when these electrons collide with the anode. Therefore, the quantity of photons is directly proportional to the mA; as mA increases, the number of photons produced also increases, leading to a higher radiation exposure.

In contrast, kilovoltage peak (kVp) affects the energy (quality) of the photons but does not directly control their quantity. Exposure time does determine the duration of the exposure but, by itself, does not influence the number of photons produced per second; rather, it multiplies the quantity produced by the mA setting over that time. Anode heat is a concern for the durability and performance of the x-ray tube but does not control the number of photons generated.

Thus, the controlling factor for the quantity of photons produced per second during an exposure is the mA setting, as