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. Author manuscript; available in PMC: 2016 Sep 12.
Published in final edited form as: Gut. 2015 May 14;64(11):1816–1823. doi: 10.1136/gutjnl-2013-306706

Figure 2.

Figure 2

Optical properties of tissue. Image resolution improves with shorter wavelengths, and tissue penetration increases with longer wavelengths. Haemoglobin (Hb) dominates absorption of light in the visible (400–700 nm). Water absorption plays a small role in the infrared (IR; >900 nm). The extinction coefficients for Hb (blue), oxyhaemoglobin (HbO2; red) and water (black) are shown. Fluorophores can be used to improve image contrast, and include Diethylaminocoumarin (DEAC), fluorescein, fluorescein isothiocyanate (FITC; derivative of fluorescein), Cyanine (CY) derivatives (Cy5, Cy5.5), and IR800. AFI, autofluorescence imaging; NBI, narrow band imaging; OCT, optical coherence tomography; OFDI, optical frequency domain imaging; WLE, white light endoscopy.