How does decreased kilovoltage peak (kVp) affect differences in signal intensity in the remnant beam?

How does decreased kilovoltage peak (kVp) affect differences in signal intensity in the remnant beam?

• A. Decreased differences in signal intensity
• B. Increased differences in signal intensity
• C. No change
• D. Scatter increases

Answer: (B)

Photon energy set by kVp governs how X-rays interact with matter. At lower kVp, photons have less energy, so absorption is dominated by the photoelectric effect, which depends strongly on tissue density and atomic number. This makes dense structures (like bone) attenuate much more than soft tissue, widening the differences in the remnant beam’s transmitted signal. So decreasing kVp increases the differences in signal intensity in the remnant beam (increased image contrast). If kVp is raised, attenuation differences become less pronounced, reducing the contrast.

Photon energy set by kVp governs how X-rays interact with matter. At lower kVp, photons have less energy, so absorption is dominated by the photoelectric effect, which depends strongly on tissue density and atomic number. This makes dense structures (like bone) attenuate much more than soft tissue, widening the differences in the remnant beam’s transmitted signal. So decreasing kVp increases the differences in signal intensity in the remnant beam (increased image contrast). If kVp is raised, attenuation differences become less pronounced, reducing the contrast.