This document discusses Doppler ultrasonography and the spectral waveforms used to analyze blood flow patterns in vessels. It provides details on: - The Doppler spectrum which represents blood flow velocities over time on a graph with frequency on the vertical axis and time on the horizontal axis. - Characteristics of normal flow patterns seen in major vessels and how they relate to vessel anatomy and organ function. - Abnormal flow patterns seen in pathologies like pseudoaneurysms and arteriovenous fistulas. Pseudoaneurysms show a to-and-fro waveform and arteriovenous fistulas demonstrate elevated continuous flow from the artery into the vein.