Spectral broadening in Doppler studies refers to a wider spectral peak due to velocity distribution. Which option best describes this phenomenon?

• A. Aliasing
• B. Spectral broadening
• C. Mirror image
• D. Bidirectional flow

Answer: (B)

In Doppler spectra, the width of the peak reflects how many different velocities are present within the sampled volume. If all the moving scatterers shared the same velocity, the spectrum would be a sharp, narrow spike. But in real vessels, there’s a distribution of speeds across the flow—due to the parabolic velocity profile of laminar flow, angle effects, and any turbulent or multi-directional components. That spread of velocities makes the Doppler spectrum widen, producing a broader spectral peak. This widening is exactly what’s described by spectral broadening.

This isn’t about aliasing, which is a sampling-rate issue that causes wrap-around of high-velocity signals, nor about a mirror image artifact or simply flow that goes in two directions. Those describe different phenomena; the broadening specifically represents velocity dispersion within the sampled region.