Which approach to increasing the signal may lead to an increase in scatter reaching the image receptor (IR)?

• A. Increasing milliampere-seconds (mAs)
• B. Increasing kilovoltage peak (kVp)
• C. Increasing grid ratio
• D. Increasing source-to-image distance (SID)

Answer: (B)

Raising the kilovoltage peak makes the beam more energetic, changing how photons interact with the patient. With higher energy, photons are more likely to undergo Compton scattering inside the body. Those scattered photons travel in various directions, and some reach the image receptor, adding unwanted exposure and reducing image contrast. This is why increasing kVp is the approach that can raise the signal at the receptor while also increasing the amount of scatter reaching the IR.

Increasing mAs would boost the total number of photons and thus the signal, but scatter also increases; the key factor that drives the rise in scatter reaching the IR is beam energy, which is why the kVp increase is the more influential choice. Increasing grid ratio absorbs more scatter before it reaches the IR, and increasing SID reduces exposure and scatter reaching the IR due to geometric and distance effects, so neither option increases scatter reaching the IR in the same way as higher kVp.