Which imaging modality requires blood clearance to obtain high-quality images?

• A. OCT requires blood clearance to obtain high-quality images.
• B. IVUS requires blood clearance.
• C. CTCA requires blood clearance.
• D. MRI requires blood clearance.

Answer: (B)

Blood clearance is needed when the imaging relies on optical light rather than sound. Optical coherence tomography uses infrared light to resolve very small wall details, and red blood cells scatter and absorb that light strongly. To see the vessel wall clearly and capture high-resolution microstructures, the lumen is flushed with saline or contrast to create a blood-free field.

Intravascular ultrasound, by contrast, sends sound waves that can travel through blood with less disruption, so images can be obtained without clearing the blood. CT coronary angiography and MRI don’t depend on displacing blood for image formation in the same way; they rely on different physics (X-ray contrast for CT, magnetic resonance properties for MRI).

So the modality that requires blood clearance to obtain high-quality images is the optical one—OCT.