Which of the following is directly proportional to the dose delivered to the patient?

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Multiple Choice

Which of the following is directly proportional to the dose delivered to the patient?

Explanation:
Photon quantity controlled by mAs determines how much dose the patient receives. The number of x-ray photons produced in the tube is proportional to the tube current (mA) times the exposure time (s). Doubling either mA or exposure time doubles the photon flux and roughly doubles the energy deposited in the patient, assuming tissue attenuation is similar. kVp changes the energy of the photons and how deeply they penetrate; it affects image contrast and penetration more than it directly scales dose. SID/FFD follows the inverse square law—increasing distance decreases dose, not increases. The percentage of characteristic radiation relates to the beam’s spectral composition and isn’t a direct driver of patient dose in routine imaging. So, the factor that is directly proportional to the dose delivered is the mAs.

Photon quantity controlled by mAs determines how much dose the patient receives. The number of x-ray photons produced in the tube is proportional to the tube current (mA) times the exposure time (s). Doubling either mA or exposure time doubles the photon flux and roughly doubles the energy deposited in the patient, assuming tissue attenuation is similar.

kVp changes the energy of the photons and how deeply they penetrate; it affects image contrast and penetration more than it directly scales dose. SID/FFD follows the inverse square law—increasing distance decreases dose, not increases. The percentage of characteristic radiation relates to the beam’s spectral composition and isn’t a direct driver of patient dose in routine imaging.

So, the factor that is directly proportional to the dose delivered is the mAs.

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