Continuous Wave Doppler

Similar to Pulsed Doppler, Continuous Wave Doppler (CW Doppler) produces a spectral display of the Doppler shifts.

However, unlike Pulsed Doppler, CW Doppler has extremely poor range resolution.  So, why would we use it?  The answer is that CW Doppler cannot alias.  Because it is not a pulsed technique, it has no Nyquist limit.  Therefore, CW Doppler can be used to assess extremely high Doppler shifts without ever encountering aliasing.

Due to its poor range resolution, CW Doppler is not typically used in general-duty scanning, but does have a role in both echocardiography and vascular ultrasound.  The adjacent video provides a good overview of CW Doppler.