Anatomy And Physiology Diagnostic Imaging Practice Test

When a vessel narrows, the flow has to speed up at that point to push the same amount of blood through a smaller area. That rise in velocity shows up on Doppler as a high peak systolic velocity right at the stenosis. After the narrow segment, the jet often decelerates and becomes unstable as it expands again, creating turbulent flow downstream. You’ll see spectral broadening and irregular color flow in that post-stenotic region. So the combination of increased peak systolic velocity at the narrowing plus post-stenotic turbulence is the best sign that the stenosis is hemodynamically significant. Absence of flow points to occlusion rather than stenosis, laminar flow across a narrowed segment is uncommon due to disturbance, and decreased velocity contradicts the basic principle that velocity rises with reduced cross-sectional area.