Which region is most affected by overcolor gain in color Doppler imaging?

• A. Anterior wall
• B. Posterior wall
• C. Lumen center
• D. Near the transducer surface

Answer: (B)

Color Doppler gain amplifies all Doppler signals, so signals with low velocity are most easily boosted into visible color. In a vessel with laminar flow, velocity is highest in the center and drops to near zero at the walls. The region at the posterior wall represents this low-velocity zone, where tiny Doppler shifts or even noise can be magnified into color when gain is too high. That makes the posterior wall show color artifacts or “bloom” more readily than the lumen center, where true high-velocity flow remains clearly defined. The anterior wall or the lumen center aren’t as susceptible because their flow velocities are higher and color remains more accurate unless gain is extreme.