Optical coherence tomography

Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to capture micrometer-resolution, two- and three-dimensional images from within optical scattering media (e.g., biological tissue). It is used for medical imaging and industrial nondestructive testing (NDT). Optical coherence tomography is based on low-coherence interferometry, typically employing near-infrared light. The use of relatively long wavelength light allows it to penetrate into the scattering medium. Confocal microscopy, another optical technique, typically penetrates less deeply into the sample but with higher resolution. Depending on the properties of the light source (superluminescent diodes, ultrashort pulsed lasers, and supercontinuum lasers have been employed), optical coherence tomography has achieved sub-micrometer resolution (with very wide-spectrum sources emitting over a ~100 nm wavelength range). Optical coherence tomography is one of a class of optical tomographic techniques. Commercially available optical coherence tomography systems are employed in diverse applications, including art conservation and diagnostic medicine, notably in ophthalmology and optometry where it can be used to obtain detailed images from within the retina. Recently, it has also begun to be used in interventional cardiology to help diagnose coronary artery disease, and in dermatology to improve diagnosis. A relatively recent implementation of optical coherence tomography, frequency-domain optical coherence tomography, provides advantages in the signal-to-noise ratio provided, thus permitting faster signal acquisition. OCT is not the same as Optical coherence microscopy (OCM), which "is a microscopic incarnation of optical coherence tomography (OCT)" that can be used for 3D imaging reconstruction through intrinsic contrasting of back-scattered (coherent) light. Starting from Adolf Fercher and colleagues’ work on low-, partial coherence or white-light interferometry for in vivo ocular eye measurements in Vienna in the 1980s, imaging of biological tissue, especially of the human eye, was investigated in parallel by multiple groups worldwide.