Optical Coherence Tomography (OCT): Principle and Technical Realization

Optical coherence tomography (OCT) is a non-invasive technique for cross-sectional tissue imaging. It typically uses light in the near-infrared spectral range which has a penetration depth of several hundred microns in tissue. The backscattered light is measured with an interferometric set-up to reconstruct the depth profile of the sample at the selected location. A scanning OCT beam allows for acquisition of cross-sectional images of the tissue structure. Different technical methods are introduced and compared regarding their properties like sensitivity, imaging speed and penetration depth. Regardless of the technical realization, axial resolution and imaging range of an OCT system are determined by light source and detector characteristics. Combining retinal OCT with a confocal scanning laser ophthalmoscope allows for motion tracking during acquisition and to examine the exact same position at any time again. Segmentation of features is the basis for automatic depth measurements and standardized measurements to be compared with normative databases. New trends show the ability of functional OCT to image flow, polarizing properties of tissue and even mechanical properties like elasticity. Recent approaches to improve the resolution and the acquisition speed show the ongoing research interest in OCT.