PIONEERING EXPERIMENT
Optical Coherence Tomography
OPTICAL COHERENCE TOMOGRAPHY
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Patrice TANKAM * School of Optometry, Indiana University, Bloomington, Indiana, United States * ptankam @ iu. edu
https:// doi. org / 10.1051 / photon / 202413420
Optical coherence tomography( OCT) has become a critical imaging tool in medicine owing to its noninvasive imaging capability of tissues with micrometerlevel details. From its initial experiments in the 1980s to now, the adoption of OCT has been facilitated not only by scientific innovations but also advances in fiber optic telecommunications and photonics, as well as industry and government support. This review highlights key milestones that have contributed to the clinical adoption of OCT, as well as current and future trends.
Optical coherence tomography( OCT) represents one of the major imaging technological breakthroughs of our century, owing to its capabilities to noninvasively enable three dimensional( 3D) visualization of tissues in living specimens with cellular-level resolution [ 1 ]. OCT has become the standard of care in ophthalmology and has been a critical tool for understanding disease mechanism, facilitating their diagnosis, and monitoring their treatment, particularly for blinding diseases such as diabetic retinopathy, age-related macular degeneration( AMD), and glaucoma, affecting hundreds of millions of people worldwide. OCT has also emerged as a critical clinical tool in cardiology, dermatology, endoscopy, gastroenterology, and beyond.
The principle of OCT is analogous to ultrasound imaging, measuring the time of flight of echoes reflecting from different layers of tissues to infer the depth localization of the layers. Owing to the greater speed of light waves compared with ultrasound waves, OCT leverages the unique sensitivity of interferometry techniques to achieve such measurements. Interferometry can be traced back to Thomas Young’ s double-slit experiment in the 1800s, where two light waves from the same source, passing through two distinct slits, can be recombined coherently. The resulting wave has a maximum energy( i. e., constructive interference) when the difference in distances travelled( i. e., the optical path difference) by the two waves is a multiple of the wavelength( i. e., the waves are in phase) and a lower energy( i. e., destructive interference) when the optical path difference between the two waves is an odd multiple of half the wavelength( i. e., the waves are out of phase). By analysing the repeated pattern( i. e., fringes) of the interference signal, one can inform the distance travelled by one wave relative to the other, with an accuracy below the wavelength of light. The same principle is applied to different variations of interferometry techniques and OCT, with one light path serving as the reference arm and the other path serving as the sample arm. While several scientific experiments, including Albert Michelson’ s interferometry in the 1880s and low-coherence interferometry( LCI) by Sir Isaac Newton in the 1980s, have contributed to the working principle of OCT, pioneering experiments carried out by Professor Adolf Fercher’ s
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