Optical coherence tomography (OCT) is an imaging technique that uses interferometry with short-coherence-length light to obtain micrometer-level depth resolution and uses transverse scanning of the light beam to form two- and three-dimensional images from light reflected from within biological tissue or other scattering media. Short-coherence-length light can be obtained using a superluminescent diode (SLD) with a broad spectral bandwidth or a broadly tunable laser with narrow linewidth. The first demonstration of OCT imaging (in vitro) was published by a team from MIT and Harvard Medical School in a 1991 article in the journal Science.[1] The article introduced the term "OCT" to credit its derivation from optical coherence-domain reflectometry, in which the axial resolution is based on temporal coherence.[2] The first demonstrations of in vivo OCT imaging quickly followed.[3][4][5]
The first US patents on OCT by the MIT/Harvard group described a time-domain OCT (TD-OCT) system.[6][7] These patents were licensed by Zeiss and formed the basis of the first generations of OCT products until 2006. Tanno et al. obtained a patent on optical heterodyne tomography (similar to TD-OCT) in Japan in the same year.[8]
In the decade preceding the invention of OCT, interferometry with short-coherence-length light had been investigated for a variety of applications.[9][10][11][12][13][14][15][16][17][18][19][20] The potential to use interferometry for imaging was proposed,[20] and measurement of retinal elevation profile and thickness had been demonstrated.[19]
The initial commercial clinical OCT systems were based on point-scanning TD-OCT technology, which primarily produced cross-sectional images due to the speed limitation (tens to thousands of axial scans per second). Fourier-domain OCT became available clinically 2006, enabling much greater image acquisition rate (tens of thousands to hundreds of thousands axial scans per second) without sacrificing signal strength. The higher speed allowed for three-dimensional imaging, which can be visualized in both en face and cross-sectional views. Novel contrasts such as angiography, elastography, and optoretinography also became possible by detecting signal change over time. Over the past three decades, the speed of commercial clinical OCT systems has increased more than 1000-fold, doubling every three years and rivaling Moore's law of computer chip performance. Development of parallel image acquisition approaches such as line-field and full-field technology may allow the performance improvement trend to continue.
OCT is most widely used in ophthalmology, in which it has transformed the diagnosis and monitoring of retinal diseases, optic nerve diseases, and corneal diseases. It has greatly improved the management of the top three causes of blindness – macular degeneration, diabetic retinopathy, and glaucoma – thereby preventing vision loss in many patients. By 2016 OCT was estimated to be used in more than 30 million imaging procedures per year worldwide.[21]
^Fercher AF, Hitzenberger CK, Drexler W, Kamp G, Sattmann H (July 1993). "In vivo optical coherence tomography". American Journal of Ophthalmology. 116 (1): 113–114. doi:10.1016/s0002-9394(14)71762-3. PMID8328536.
^US 5321501A, Swanson EA, Huang D, Fujimoto JG, Puliafito CA, "Method and apparatus for optical imaging with means for controlling the longitudinal range of the sample", issued 1994-06-14
^US 5459570A, Swanson EA, Huang D, Fujimoto JG, Puliafito CA, "Method and apparatus for performing optical measurements", issued 1995-10-17
^JA 2010042, Tanno N, Ichikawa T, Saeki A, "Lightwave Reflection Measurement", published 1990
^Takada K, Yokohama I, Chida K, Noda J (May 1987). "New measurement system for fault location in optical waveguide devices based on an interferometric technique". Applied Optics. 26 (9): 1603–1606. Bibcode:1987ApOpt..26.1603T. doi:10.1364/AO.26.001603. PMID20454375.
^Huang D, Wang J, Lin CP, Puliafito CA, Fujimoto JG (1991). "Micron-resolution ranging of cornea anterior chamber by optical reflectometry". Lasers in Surgery and Medicine. 11 (5): 419–425. doi:10.1002/lsm.1900110506. PMID1816476. S2CID19888483.
^ abFercher AF (12–16 August 1990). "Ophthalmic interferometry". In von Bally G, Khanna S (eds.). Proceedings of the International Conference on Optics in Life Sciences. Garmisch-Partenkirchen, Germany. pp. 221–228. ISBN0-444-89860-3.