Which factor primarily affects patient dose during a radiographic examination?

Which factor primarily affects patient dose during a radiographic examination?

• A. Examination duration
• B. mAs
• C. kVp
• D. Filtration

Answer: (B)

The amount of radiation dose a patient receives is driven mainly by the number of x‑ray photons produced, which comes from the tube current and how long the exposure lasts. This combined factor, mAs, determines photon fluence, so dose increases in direct proportion to mAs. In other words, more photons mean more energy deposited in the patient, and reducing mAs lowers the dose accordingly. Filtration and kVp influence dose in different ways but are secondary to the photon quantity. Filtration trims the beam by removing low-energy photons, reducing skin dose without compromising image quality as much. kVp changes the energy of the photons and thus beam penetration and contrast; higher kVp can change dose requirements but does not control the photon count as directly as mAs does. The exposure duration is the time component of mAs, so its effect on dose is through the same direct relationship with photon production.

The amount of radiation dose a patient receives is driven mainly by the number of x‑ray photons produced, which comes from the tube current and how long the exposure lasts. This combined factor, mAs, determines photon fluence, so dose increases in direct proportion to mAs. In other words, more photons mean more energy deposited in the patient, and reducing mAs lowers the dose accordingly.

Filtration and kVp influence dose in different ways but are secondary to the photon quantity. Filtration trims the beam by removing low-energy photons, reducing skin dose without compromising image quality as much. kVp changes the energy of the photons and thus beam penetration and contrast; higher kVp can change dose requirements but does not control the photon count as directly as mAs does. The exposure duration is the time component of mAs, so its effect on dose is through the same direct relationship with photon production.