Table 4.

Showing optical properties and OCT image interpretation of various atherosclerotic plaque morphologies.

Tissue	Optical properties		Imae
	Backscatter	Attenuation
Lipid	Low	High	Anatomic border with fibrous layer cannot be made out due to high backscattering. But then light attenuates much faster. So, lipid pool is progressively dark (Figure 1B)
Fibrous	High	Low	Bright signal rich homogenous appearance (Figure 1C)
Calcified tissue	Low	Low	Signal poor region with sharp boundaries between calcified and fibrous tissue (Figures 1D–F)
Thin cap fibrous atheromas (TCFA)	• Cap–High • Core–low	• Cap–Low • Core–High	Bright and signal rich fibrous cap followed by signal poor area of lipid pool with cap thickness <65 μm. TCFAs are more prone for plaque rupture (Figure 1G)
Red thrombus	High	High	Intraluminal mass and casts a shadow on the vessel walls due to high attenuation of RBCs (Figure 1H)
White thrombus	High	Low	Intraluminal mass with no attenuation (Figure 1I)
Macrophages	High	High	Bright spots or bands at border between fibrous cap and lipid core casting shadow behind it (Figure 1J)
Cholesterol crystal	High	Low	Thin & linear structure in the plaque (Figure 1K)