intravascular ultrasound

Intravascular ultrasound puts a miniature ultrasound probe on the tip of a catheter and slides it inside a coronary artery, so the vessel is imaged from within. Where an ordinary angiogram outlines only the channel where dye flows, IVUS looks sideways into the artery wall itself, producing a cross-sectional ring that shows the lumen, the layers of the wall, and the plaque built up between them.

This inside view answers questions the dye picture cannot. It measures the true diameter and area of the lumen and the artery, reveals how much plaque is present and what it is made of, and shows whether a narrowing that looks borderline on angiography is genuinely tight. During treatment it is invaluable for sizing and positioning a stent and for confirming afterward that the stent is fully expanded and well apposed to the wall — details strongly linked to good long-term results.

IVUS adds time, cost, and the small extra risk of passing an instrument down a coronary artery, so it is used selectively rather than in every case. A related light-based technique, optical coherence tomography, gives even finer resolution but less depth. Both are tools of the catheterization laboratory that complement angiography and pressure-wire measurements to guide precise, durable treatment.