Optical coherence tomography: Principles applications and advances

Optical coherence tomography (OCT) is a rapidly emerging high-resolution biomedical imaging modality that has found application in a wide range of biological and medical specialties. OCT performs optical ranging in tissue, using low-coherence interferometry to determine where reflections of light originate. OCT is analogous to ultrasound, except reflections of near-infrared light are detected rather than sound. The use of light permits spectroscopic discrimination of tissue and with shorter wavelengths compared to ultrasound, higher spatial resolutions less than 1 μm are possible. OCT can perform optical biopsies non-invasively and in real-time, with images that approach the resolutions of histology. The OCT system can be extremely compact using fiber optics and portable broad bandwidth optical sources. Modular beam-delivery instruments including hand-held probes, fiber-optic catheter-endoscopes, imaging biopsy needles, and various microscopes enable OCT imaging in a large number of applications. This paper will review the basic principles of OCT, detail representative application areas in biological microscopy, ophthalmology, gastroenterology, cardiology, and oncology, and introduce several of the latest advances in the field including ultrahigh-resolution optical sources, functional OCT, Fourier (spectral)-domain OCT, novel contrast agents, and molecular imaging techniques. To date, the breadth and applicability of OCT to biological and medical imaging suggests that in time, OCT is likely to become a major clinical imaging modality.