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Figure 3: The mechanism responsible for white zone visibility at an angle. A-NBI light enters the mucosa from the intervening part in the direction of the crypt epithelium. It is then scattered, and the white zone appears as shown in Figure 3(b)A. B-NBI light entering crypts passes through the epithelium and is absorbed by the hemoglobin of red blood cells in blood vessels. As a result, the blood vessels appear as brown lines as shown in Figure 3(b)B.