How does increased kilovoltage peak (kVp) affect the proportion of scatter radiation striking the image receptor?

How does increased kilovoltage peak (kVp) affect the proportion of scatter radiation striking the image receptor?

• A. Increased scatter
• B. Decreased scatter
• C. No change
• D. Scatter only at high mA

Answer: (A)

Raising kilovolt peak increases the energy of the X-ray photons, which shifts interactions in the patient from mostly photoelectric absorption toward more Compton scattering. Scatter photons come from these Compton interactions and, being higher energy and less easily absorbed, are more likely to escape the patient and reach the image receptor. So the fraction of detected radiation that is scatter grows as kVp goes up. This also helps explain why higher kVp can reduce image contrast, since more scatter contributes to the signal at the receptor.

Raising kilovolt peak increases the energy of the X-ray photons, which shifts interactions in the patient from mostly photoelectric absorption toward more Compton scattering. Scatter photons come from these Compton interactions and, being higher energy and less easily absorbed, are more likely to escape the patient and reach the image receptor. So the fraction of detected radiation that is scatter grows as kVp goes up. This also helps explain why higher kVp can reduce image contrast, since more scatter contributes to the signal at the receptor.