Practice Test GeeksARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test
← All ARDMS SPI Flashcard Decks

Pulsed-Wave and CW Doppler Flashcards

6 cards from real ARDMS SPI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Pulsed-Wave and CW Doppler flashcards as text

  1. Which of the following is a primary advantage of Continuous-Wave (CW) Doppler over Pulsed-Wave (PW) Doppler?

    Answer: It is not limited by aliasing at high velocities.

    Continuous-Wave (CW) Doppler continuously transmits and receives ultrasound, so it does not have a sampling rate (PRF) that limits velocity measurement. This allows it to accurately measure very high velocities without the aliasing artifact that affects Pulsed-Wave (PW) Doppler.

  2. A sonographer observes that the spectral waveform on a Pulsed-Wave Doppler display appears to "wrap around" from the top of the scale to the bottom. This artifact is known as:

    Answer: Aliasing

    Aliasing occurs in PW Doppler when the measured Doppler shift exceeds the Nyquist limit (half the PRF). The system cannot sample the signal fast enough, causing the highest velocities to be incorrectly displayed on the opposite side of the baseline.

  3. A sonographer is performing a PW Doppler examination and notes significant aliasing. Which of the following adjustments is LEAST likely to correct this artifact?

    Answer: Increasing the overall Doppler gain.

    Increasing the Doppler gain amplifies the entire signal, including the aliased components, making the display brighter but does not correct the aliasing itself. Increasing the PRF raises the Nyquist limit, shifting the baseline provides more room for the waveform, and using a lower frequency transducer reduces the Doppler shift for a given velocity; all are valid methods to reduce or eliminate aliasing.

  4. Which of the following statements accurately describes a key characteristic of Continuous-Wave (CW) Doppler?

    Answer: It cannot determine the exact depth from which a velocity signal originates.

    Because a CW Doppler system transmits and receives sound continuously along the entire beam, it detects all velocities in its path. It cannot isolate a specific depth, a characteristic known as range ambiguity.

  5. A Pulsed-Wave Doppler system is operating with a Pulse Repetition Frequency (PRF) of 12 kHz. What is the maximum Doppler shift that can be displayed without aliasing?

    Answer: 6 kHz

    The Nyquist limit states that the highest Doppler frequency that can be measured without aliasing is one-half of the Pulse Repetition Frequency (PRF). Therefore, with a PRF of 12 kHz, the Nyquist limit is 6 kHz (12,000 Hz / 2).

  6. A sonographer is tasked with measuring the peak velocity of a severe aortic stenosis jet, which is expected to be approximately 4 m/s. Which Doppler modality is most appropriate for this measurement and why?

    Answer: Continuous-Wave Doppler, because it is not subject to aliasing and can measure very high velocities.

    A velocity of 4 m/s will create a Doppler shift that far exceeds the Nyquist limit of Pulsed-Wave Doppler, resulting in severe aliasing. Continuous-Wave (CW) Doppler is the correct choice because it does not alias and is designed to accurately measure such high velocities. While PW Doppler is precise in location, it cannot handle the speed. Color and Power Doppler are for qualitative assessment, not peak velocity quantification.