IVUS

Intravascular ultrasound (IVUS) is an imaging modality that uses a miniature ultrasound transducer mounted on a catheter to obtain real-time, cross-sectional images of a vessel from within the lumen. It is commonly used during catheter-based interventions to evaluate coronary arteries and other vessels.

Two main IVUS designs exist: mechanically rotating transducers and electronic phased-array transducers. Frequencies typically range from 20 to 40 MHz, which balance spatial resolution and penetration depth. IVUS produces grayscale cross-sectional images showing the lumen, vessel wall, and external elastic membrane; cross-sectional area measurements (lumen area, vessel area) support assessment of stenosis and remodeling. Blood is displaced by saline or contrast to obtain clear images. Three-dimensional reconstructions are possible with serial slices.

Clinical uses include guiding percutaneous coronary intervention (PCI), optimizing stent sizing and deployment, detecting dissections, malapposition, or residual plaque, and evaluating diffuse atherosclerosis. In peripheral and structural interventions, IVUS provides similar benefits. Tissue characterization can be performed with software packages such as virtual histology IVUS or iMAP, which classify plaque components.

Advantages and limitations: IVUS penetrates deeper than some other intravascular imaging modalities and can assess large and heavily calcified vessels, but has lower axial resolution than optical coherence tomography and limited ability to characterize microstructure. Image quality may be reduced by calcification, vessel tortuosity, or motion. The technique is invasive and carries risks related to catheter manipulation and contrast use.

Safety and training: IVUS is generally safe when performed by trained operators. Complications are uncommon but can include vessel injury, dissection, hematoma, or contrast-associated nephropathy. The modality complements angiography and other imaging tools in contemporary interventional cardiology.