Which Doppler technique does NOT provide range resolution?

Which Doppler technique does NOT provide range resolution?

• A. Color Doppler
• B. Pulsed-wave Doppler
• C. Continuous-wave Doppler
• D. Power Doppler

Answer: (C)

Range resolution means the ability to tell apart echoes coming from different depths along the ultrasound beam. Continuous-wave Doppler transmits and receives continuously, so the signal is the sum of reflections from all depths along the beam and cannot be localized to a specific depth. That lack of depth discrimination is why it does not provide range resolution. In contrast, pulsed-wave Doppler sends short pulses and uses a depth-limited listening gate, so reflections from a particular depth can be isolated, giving range information. Color Doppler overlaid on a B-mode image samples velocities within a defined depth region (a color box), providing depth localization within that area. Power Doppler uses a depth gate to accumulate Doppler energy in a defined region, offering depth confinement as well. Hence, the technique without range resolution is continuous-wave Doppler.

Range resolution means the ability to tell apart echoes coming from different depths along the ultrasound beam. Continuous-wave Doppler transmits and receives continuously, so the signal is the sum of reflections from all depths along the beam and cannot be localized to a specific depth. That lack of depth discrimination is why it does not provide range resolution. In contrast, pulsed-wave Doppler sends short pulses and uses a depth-limited listening gate, so reflections from a particular depth can be isolated, giving range information. Color Doppler overlaid on a B-mode image samples velocities within a defined depth region (a color box), providing depth localization within that area. Power Doppler uses a depth gate to accumulate Doppler energy in a defined region, offering depth confinement as well. Hence, the technique without range resolution is continuous-wave Doppler.