What factor most influences the number of photons reaching the image receptor?

The factor that most influences the number of photons reaching the image receptor is the milliampere-seconds (mAs). This is because mAs is a measurement of the quantity of radiation produced during an exposure. It represents the product of the tube current (in milliamperes) and the exposure time (in seconds).

When you increase the mAs, you increase the total number of photons generated in the x-ray tube. A higher mAs results in a higher number of photons being emitted and subsequently reaching the image receptor, which directly affects the image density and quality. Therefore, mAs is the primary determinant in controlling the overall exposure to the image receptor.

While exposure time and kilovoltage peak (kVp) also play important roles in radiographic imaging, they do not solely determine the quantity of photons reaching the receptor in the same direct manner as mAs. Film type also affects image quality but is less about the quantity of photons directly impacting the receptor.