11/13/2023 0 Comments Optical coherence tomography scan![]() ![]() Changing the location of the reference mirror allows backscattered tissue intensity levels to be detected from different depths in the tissue sample. Intensity information, in the form of a reflectivity profile in depth, can be extracted from the interference profile. Provided the path length to the reference mirror and tissue match to within the coherence length of the light source, when the reflected beams recombine, interference occurs. OCT uses low coherence interferometry to obtain A-scan intensity profiles, and the process requires light to be split and sent to both a reference arm with a mirror and to the sample. The first clinical system was limited to a scanning speed of 400 axial scans (A-scans)/s because of a physical constraint: a moving reference mirror. 9 Scan patterns that enabled reproducible measurements were developed, 10 and these eventually became incorporated into a commercial system, which had an axial resolution of ∼10 μm. ![]() 4 OCT cross sections were also used to evaluate the optic disc and retinal layers 5, 8 such as the retinal nerve fiber layer (RNFL). 1 At the time of introduction, it was used to obtain in vivo optical cross sections of the anterior segment, 6 as well as retinal diseases, such as macular detachment, macular hole, epiretinal membrane, macular edema, and idiopathic central serous chorioretinopathy. 1 – 7 It is an extension of a technique called low-coherence interferometry, which was initially applied to ophthalmology for in vivo measurements of eye axial length. Optical coherence tomography (OCT) has advanced considerably since it was first applied to the eye. ![]()
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