What would be the most likely result from increasing the transmit frequency of color Doppler?

• A. Improved penetration for imaging flow in deep tissues
• B. Reduced color Doppler aliasing
• C. Improved sensitivity to slow flow
• D. Reduced flash artifact obscuring small vessel flow

Answer: (C)

In color Doppler, the Doppler shift that the system detects scales with the transmitted frequency. Raising the transmit frequency increases the frequency shift produced by a given flow velocity, so signals from slow or weak flow become easier to detect above noise and clutter. That means sensitivity to slow flow improves when you use a higher frequency.

However, higher frequency also suffers greater attenuation, which reduces penetration and can make deep vessels harder to visualize, so penetration is typically worse, not better. Aliasing depends on the pulse repetition frequency and the velocity range, not solely on the transmit frequency, so increasing frequency doesn’t inherently reduce aliasing. Flash artifacts are related to rapid color changes and high-velocity jets near the imaging plane and aren’t directly mitigated by simply raising frequency.