Which change would directly increase the dose at the image receptor if distance and filtration remain constant?

Which change would directly increase the dose at the image receptor if distance and filtration remain constant?

• A. Increase kVp
• B. Increase distance
• C. Increase filtration
• D. Increase mAs

Answer: (D)

The key idea is that the dose at the image receptor is driven mainly by how many photons are produced and reach the receptor. That photon quantity is controlled by the mA–seconds (mAs). With distance and filtration held constant, increasing mAs directly increases the number of X-ray photons emitted by the tube and traveling to the receptor, so the dose at the receptor goes up. Increasing distance would spread photons out (inverse square law) and isn’t allowed here, so it wouldn’t directly increase receptor dose. Increasing filtration removes low-energy photons and actually decreases dose. Increasing kVp changes the energy/penetrability of photons but, if mAs stays the same, it does not increase the number of photons reaching the receptor as directly as increasing mAs; it can also affect image quality.

The key idea is that the dose at the image receptor is driven mainly by how many photons are produced and reach the receptor. That photon quantity is controlled by the mA–seconds (mAs). With distance and filtration held constant, increasing mAs directly increases the number of X-ray photons emitted by the tube and traveling to the receptor, so the dose at the receptor goes up.

Increasing distance would spread photons out (inverse square law) and isn’t allowed here, so it wouldn’t directly increase receptor dose. Increasing filtration removes low-energy photons and actually decreases dose. Increasing kVp changes the energy/penetrability of photons but, if mAs stays the same, it does not increase the number of photons reaching the receptor as directly as increasing mAs; it can also affect image quality.