What type of Doppler device uses two elements, one to receive and one to transmit?

What type of Doppler device uses two elements, one to receive and one to transmit?

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

Answer: (C)

The main idea here is how the Doppler device handles transmission and reception. Continuous-wave Doppler uses two separate crystal elements: one for constantly transmitting ultrasound and another for constantly receiving the echoes. Keeping transmission and reception separate allows the system to measure Doppler frequency shifts over the entire transmitted signal, which enables detecting a wide range of flow velocities without worrying about timing to distinguish depth. However, because there’s no range gating, you don’t get precise depth information about where the echoes come from. Pulsed-wave Doppler, by contrast, uses a single element that both emits and receives in short bursts, with time delays that let the machine know the distance of the returning echoes. That provides depth (range) information but limits the maximum measurable velocity due to aliasing. Color Doppler and Power Doppler are imaging modes that typically rely on pulsed transmissions to map flow over an area, rather than relying on two separate transmit and receive elements. So, the two-element arrangement—one transmitting and one receiving continuously—is the hallmark of continuous-wave Doppler.

The main idea here is how the Doppler device handles transmission and reception. Continuous-wave Doppler uses two separate crystal elements: one for constantly transmitting ultrasound and another for constantly receiving the echoes. Keeping transmission and reception separate allows the system to measure Doppler frequency shifts over the entire transmitted signal, which enables detecting a wide range of flow velocities without worrying about timing to distinguish depth. However, because there’s no range gating, you don’t get precise depth information about where the echoes come from.

Pulsed-wave Doppler, by contrast, uses a single element that both emits and receives in short bursts, with time delays that let the machine know the distance of the returning echoes. That provides depth (range) information but limits the maximum measurable velocity due to aliasing. Color Doppler and Power Doppler are imaging modes that typically rely on pulsed transmissions to map flow over an area, rather than relying on two separate transmit and receive elements.

So, the two-element arrangement—one transmitting and one receiving continuously—is the hallmark of continuous-wave Doppler.