Vasodilation is the relaxation and widening of blood vessel walls, resulting in an increased vessel diameter and reduced resistance to blood flow. It can occur as a normal physiological response (such as during exercise or warming), as a response to medications, or as part of an inflammatory process. On Doppler ultrasound, vasodilation manifests as increased blood flow velocity and volume, decreased resistive index, and enhanced diastolic flow in the affected vascular bed. For example, reactive hyperemia testing uses temporary limb compression to induce vasodilation, and the resulting increase in blood flow is measured by Doppler. Understanding vasodilation is important for sonographers because it affects the interpretation of Doppler waveforms and hemodynamic measurements throughout the body.
Sonography Term