Which statement correctly distinguishes spectral Doppler from color Doppler?

• A. Color Doppler shows flow direction and relative velocity over an area; spectral Doppler provides a velocity spectrum over a defined sample volume with time, giving exact velocity and waveform information.
• B. Color Doppler shows a velocity spectrum over time at a defined sample volume; spectral Doppler shows flow direction and relative velocity over an area.
• C. Color Doppler provides a velocity spectrum over time; spectral Doppler provides color flow imaging.
• D. Color Doppler and spectral Doppler both provide only qualitative information.

Answer: (B)

The idea being tested is how these two Doppler modes convey information about blood flow in ultrasound. Color Doppler is used to map flow across a region of tissue, showing which way the blood is moving and how fast it is moving relative to the scale, over an area in the image. It provides direction (toward or away from the probe) and a qualitative sense of speed across that region, displayed as colors on top of the B-mode image.

Spectral Doppler, on the other hand, focuses on a single location defined by a gate or sample volume. It analyzes the Doppler shifts from that tiny volume over time and produces a velocity spectrum: velocity on the vertical axis and time on the horizontal axis. This gives exact velocity values in cm/s and the waveform shape, enabling precise quantification of flow patterns (such as peak systolic velocity and end-diastolic velocity).

So the correct distinction is that color Doppler shows flow direction and relative velocity over an area, while spectral Doppler provides a velocity spectrum over time from a defined sample volume, with quantitative velocity information. The other statements either swap these roles, describe color Doppler as providing a spectrum or spectral Doppler as color imaging, or claim both modalities are only qualitative, which isn’t accurate.