Shadow noise in OCT images of biological tissues

Optical coherence tomography (OCT) images of turbid medium with spatially fluctuating optical parameters demonstrate the presence of spatial noise ("shadow noise") caused by shading of the observed layer by variations in scattering and absorption coefficients of superficial layers. In this paper we report the development of the theoretical model of shadow noise in OCT images in which the features for discriminating this type of noise from the noise of a different origin are determined. Shadow noise is discovered in OCT images of biological tissue after specific image processing and the validity of the developed theoretical model is proven. The role of shadow noise as an interfering factor at imaging the variations in the backscattering coefficient, as well as the source of extra information on optical characteristics of the medium is analysed.