Which parameter primarily affects the exposure to the image receptor?

Which parameter primarily affects the exposure to the image receptor?

• A. Milliamperage (mA).
• B. Kilovolts peak (kVp).
• C. Half Value Layer (HVL).
• D. Source to image receptor distance (SID).

Answer: (A)

Exposure to the image receptor depends on how many x-ray photons actually reach the receptor. The number of photons produced in the tube is controlled by the tube current and exposure time, so increasing the milliamperage setting raises the tube current and, in turn, the photon flux reaching the receptor. This makes it the factor that most directly alters receptor exposure. Kilovoltage peak mainly changes the energy and penetrability of the photons, which affects image contrast more than the overall amount of exposure. Half Value Layer relates to beam filtration and beam quality, not how many photons reach the receptor. Source-to-image receptor distance follows the inverse square law—larger distances reduce exposure at the receptor but don’t increase photon production themselves. In practice, exposure is controlled primarily through mA (and exposure time, i.e., mAs).

Exposure to the image receptor depends on how many x-ray photons actually reach the receptor. The number of photons produced in the tube is controlled by the tube current and exposure time, so increasing the milliamperage setting raises the tube current and, in turn, the photon flux reaching the receptor. This makes it the factor that most directly alters receptor exposure.

Kilovoltage peak mainly changes the energy and penetrability of the photons, which affects image contrast more than the overall amount of exposure. Half Value Layer relates to beam filtration and beam quality, not how many photons reach the receptor. Source-to-image receptor distance follows the inverse square law—larger distances reduce exposure at the receptor but don’t increase photon production themselves. In practice, exposure is controlled primarily through mA (and exposure time, i.e., mAs).