What is a significant limitation of continuous wave (CW) Doppler ultrasound?

The significant limitation of continuous wave (CW) Doppler ultrasound lies in its inability to discriminate axial resolution. CW Doppler is effective for measuring high-velocity blood flow, particularly in large vessels, but it does not provide the spatial resolution necessary to accurately determine the depth of structures. This means that while it can detect flow, it cannot pinpoint the exact location along the depth of the ultrasound beam where that flow is occurring.

This limitation is particularly critical in vascular imaging because it may lead to uncertainty regarding the source of a detected Doppler signal. When differentiating between structures that are close together or when multiple vessels overlap in a single plane, the inability to resolve the axial positions can impede accurate diagnosis or assessment of conditions like vascular stenosis or obstructions.

In contrast, other options such as high axial resolution and enhanced sensitivity to superficial flow would not apply as limitations since CW Doppler typically sacrifices axial resolution for improved sensitivity to flow detection. Additionally, CW Doppler often has good depth of penetration and is not limited in that regard. Understanding these nuances is essential for interpreting CW Doppler ultrasound findings in a clinical setting.