The relationship between kVp and receptor exposure is best described as

The relationship between kVp and receptor exposure is best described as

• A. Directly proportional
• B. Direct, although not proportional
• C. Governed by the 15 to 50 rule
• D. Controlled by the x-ray tube current

Answer: (B)

Raising kVp makes the x-ray beam more penetrating, so more photons reach the image receptor after passing through the patient, which increases receptor exposure. But this relationship isn’t linear; the increase in exposure isn’t directly proportional to the increase in kVp because higher kVp changes beam quality, scatter production, and how much attenuation occurs in the patient. In practice, you can adjust mAs when you change kVp to keep receptor exposure more constant (the idea behind the 15% rule, where a 15% increase in kVp can be offset by roughly a 50% decrease in mAs). So receptor exposure does rise with higher kVp, but not in a strictly proportional way. The notion that exposure is simply governed by the x-ray tube current isn’t accurate for describing how kVp affects exposure.

Raising kVp makes the x-ray beam more penetrating, so more photons reach the image receptor after passing through the patient, which increases receptor exposure. But this relationship isn’t linear; the increase in exposure isn’t directly proportional to the increase in kVp because higher kVp changes beam quality, scatter production, and how much attenuation occurs in the patient. In practice, you can adjust mAs when you change kVp to keep receptor exposure more constant (the idea behind the 15% rule, where a 15% increase in kVp can be offset by roughly a 50% decrease in mAs). So receptor exposure does rise with higher kVp, but not in a strictly proportional way. The notion that exposure is simply governed by the x-ray tube current isn’t accurate for describing how kVp affects exposure.