![]() ![]() By scanning the measurement beam over the sample, adjacent axial scans can be recorded and displayed as an image using a grey or false color scale. 1B Each axial scan contains the depth-resolved backscattering signal for one transverse position. From the detected interference signal, back scattered light intensity and depth location can be computed.įig. The two beams recombine at the beamsplitter and are detected at (4) the detection unit. Using a beam splitter, light is split into (2) a sample beam that is backscattered from tissue and into (3) a reference beam backreflected from a mirror. (1) Broadband light source illuminates an interferometer. Three-dimensional (3D) imaging can be performed by recording a stack of two-dimensional images.įig. Two-dimensional imaging is accomplished by performing successive A-scan measure-ments at different transverse positions on the sample. depth information is called an axial scan (A-scan). The interference signal is recorded with a detector and the echo magnitude versus delay or axial depth scan information can be recovered (Fig. ![]() After being backscattered from structures in the tissue and reflected from the reference mirror, the two beams interfere. At the beam splitter, the light source is split into two beams: One beam of light is directed onto the tissue or specimen to be imaged, and another beam is sent to a mirror to provide a reference reflection with a known time delay. A broadband light source is used with an interferometric setup consisting of a beam splitter, a sample arm and a reference arm (Fig. The internal tissue structure is imaged noninvasively by measuring the echo delay time and intensity of light which is backreflected or backscattered from microstructural features in tissue at different depths. In ophthalmology, OCT imaging is noncontact and yields high resolution images which cannot be achieved by any other means.įigure 1 shows a schematic of how OCT imaging works. Although this depth is shallow when compared to other clinical imaging techniques, OCT can be integrated with catheters and endoscopes to perform internal body imaging and can achieve resolutions 10x to 100x finer than conventional ultrasound, magnetic resonance imaging (MRI), or computer tomography (CT). The maximum imaging depth in non-transparent tissue is ~2 to 3 mm because of attenuation from light scattering. OCT can achieve axial image resolutions of 1 to 10 microns (μm), which is one to two orders of magnitude finer than standard clinical ultrasound. OCT is analogous to ultrasound imaging except that it measures the echo time delay and intensity of backscattered or backreflected light rather than sound. ![]() While OCT has found numerous applications in fundamental research, ophthalmic medical imaging - in particular retinal imaging - remains the major field of application. Soon after the first demonstration of imaging in vitro tissue, OCT emerged as an effective tool for imaging retinal tissue in the living human eye. Since its invention two decades ago, optical coherence tomography (OCT) has played an increasingly important role in biomedical imaging. ![]()
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