The following pages contain examples of normal flow patterns recorded by pulsed wave and continuous wave techniques. Along with each example, is a schematic representation of the sampling location, and an indication of the timing of normal flow. Note that these are approximate sampling sites.
When searching for the highest velocity flow, or when looking for an indication of nonlaminar flow, take care to do a thorough interrogation of the area. This examination involves sampling not only in the standard imaging planes, but also requires that the transducer be angled upward and downward, right and left in search of the plane of maximal blood flow. Therefore, a spectral flow pattern that contains the “best” Doppler information may not correspond to a “classic” two-dimensional image. The audio signal is the best indicator of proper beam angulation for both pulsed and continuous wave recordings.
In order to understand sampling technique, it is important not only to know normal flow events, but also the types of flow disturbances that may be recorded from individual sampling locations. Flow abnormalities include retrograde flow, increased velocity and spectral broadening.
