OCT vs IVUS Resolution — EECC MCQ

Correct answer: D — OCT provides ~10x higher spatial resolution than IVUS (10-20 microns vs 100-150 microns), enabling detailed assessment of thin fibrous cap, plaque erosion, thrombus composition, and stent strut apposition — however, it requires blood clearance with contrast flushing and has limited depth penetration

OCT (optical coherence tomography) uses near-infrared light (vs IVUS which uses ultrasound) for intravascular imaging. OCT advantages: (1) ~10x higher resolution (10-20 μm vs 100-150 μm for IVUS) — enabling visualisation of: thin-cap fibroatheroma (<65 μm cap), plaque erosion (intact fibrous cap with thrombus), red vs white thrombus, macrophage infiltration, neo-intimal coverage of stent struts, and stent strut malapposition with micrometer precision; (2) better for identifying the mechanism of ACS (plaque rupture vs erosion vs calcified nodule). OCT limitations: (1) requires contrast flush to clear blood (adds contrast volume); (2) limited penetration depth (~1-2 mm vs 4-8 mm for IVUS) — cannot see through the vessel wall or heavily calcified segments; (3) cannot assess large vessels (aorta). The 2024 ESC CCS Guidelines recommend intravascular imaging (IVUS or OCT) for complex PCI optimisation (Class I).

Reference: ESC (2024): CCS Guidelines