Optical Coherence Tomography: Introduction and Theory

Optical coherence tomography (OCT) is an emerging medical imaging technology that enables micron scale, cross-sectional, and 3D imaging of microstructure of biological tissues in situ and in real time (Huang et al. 1991a, Fujimoto et al. 2000, Fujimoto 2003). OCT can function as a type of “optical biopsy”: imaging tissue microstructure with 1-10 μm resolutions and 1-2 mm penetration depths, approaching those of standard excisional biopsy and histopathology, but without the need to remove and process tissue specimens (Fujimoto et al. 1995, Brezinski et al. 1996b, Tearney et al. 1997b). OCT is analogous to ultrasound B mode imaging, except that imaging is performed by measuring the echo time delay and intensity of back-re¦ected or backscattered light rather than sound. An optical beam is scanned across the tissue and echoes of backscattered light are measured as a function of axial range (depth) and transverse position (see Figure 13.1). Two-dimensional cross-sectional OCT images of tissue are constructed by juxtaposing a series of axial measurements of backscattered light at dižerent transverse positions. ™e resulting data set is a 2D array that represents the optical backscattering within a cross-sectional slice of the tissue. ™reedimensional imaging can also be performed by stacking the 2D cross-sectional images at dižerent transverse positions.