In CT imaging, increasing the tube voltage (kVp) while keeping the tube current (mAs) constant will have which of the following effects on image contrast between soft tissue and bone?

• A Contrast decreases because the photoelectric effect falls and Compton scattering predominates ✓
• B Contrast increases due to greater photoelectric absorption
• C Contrast remains unchanged as contrast depends only on mAs
• D Contrast increases because beam hardening is eliminated

Explanation

At higher kVp, the photoelectric effect (which scales roughly as Z³/E³ and provides excellent soft tissue-bone contrast) decreases sharply, while Compton scattering (which depends on electron density and is similar across soft tissues) predominates. This reduces subject contrast between bone and soft tissue.

Reference: Bushberg, The Essential Physics of Medical Imaging, 3rd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.