Every major vessel in the human body has a characteristic flow pattern that is visible in spectral waveforms obtained in that vessel with Doppler ultrasonography (US). Spectral waveforms reflect the physiologic status of the organ supplied by the vessel, as well as the anatomic location of the vessel in relation to the heart. In addition, the waveforms may be affected by age- and development-related hemodynamic differences. For example, adults tend to have higher flow velocities, whereas neonates, particularly those born prematurely, have higher resistance to flow, especially in the cerebral and renal vascular beds. As Doppler US is performed with increasing frequency for vascular evaluation in children, the recognition of normal flow patterns has become imperative. Familiarity with the waveforms characteristic of specific veins and arteries in children is important. In addition, an understanding of the hemodynamic factors involved provides a useful basis for interpreting waveform abnormalities.
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