Name two intravascular imaging modalities and one key difference between them.

• A. OCT provides higher resolution but does not visualize the vessel wall.
• B. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT); IVUS provides deeper penetration and vessel wall imaging, while OCT offers higher resolution but requires blood clearance.
• C. OCT uses radiation.
• D. Intravascular imaging modalities include IVUS and OCT; OCT provides deeper penetration.

Answer: (B)

Two intravascular imaging modalities are IVUS and OCT. The main difference is how they create images: IVUS uses ultrasound, which travels through blood and tissue, providing deeper penetration to visualize the entire vessel wall and plaque morphology. OCT uses near-infrared light, delivering much higher spatial resolution but shallower penetration, so it highlights fine details of the intima and shallow wall and usually requires clearing blood from the lumen for a clear image. In practice, IVUS is better for overall plaque burden and wall depth, while OCT offers exquisite detail of microstructures and thin fibrous caps. The statement that OCT cannot visualize the vessel wall is inaccurate, as it does visualize it with high resolution but not as deeply; OCT does not use radiation, and its deeper penetration claim is opposite of its real property.