Speckle in Optical Coherence Tomography

Speckle is a characteristic granular texture inherent to optical coherence tomography (OCT) images of turbid media, such as biological tissues. Speckle is a consequence of the coherent nature of OCT, and results from the interference of light scattered by sub-resolution scatterers. As deformation can rearrange these scatterers, consequently changing the realization of speckle, an understanding of speckle is required to understand elastogram formation in optical coherence elastography (OCE). In this chapter, we analyze speckle using both 1D and 3D models of OCT image formation, and we use these models to describe key concepts, including statistics of the OCT amplitude, intensity, and phase; speckle size; and speckle contrast. The chapter concludes with a description of techniques developed to reduce speckle contrast, including digital image processing, and speckle-modulation techniques.