![]() Swept source technology, uses a wavelength-sweeping laser and dual balanced photo detector, allowing for faster acquisition speeds of 100,000-400,000 A-scans per second. ![]() EDI employed the use of image averaging and set the 0 delay line to adjacent to the choroid. In the late 2000's, the advent of enhanced depth imaging (EDI) allowed for better visualization of the choroid and choroidoscleral interface using the spectral domain system. Spectral domain systems typically operate at 800-870 nm wavelengths, although longer wavelengths of 1050-1060 nm are being developed for deeper penetration in the tissue. This diminishes the chance of inadvertently missing pathology. Whereas most time domain OCTs image 6 radial slices, spectral domain systems continuously image a 6mm area. Whereas most time domain OCTs are accurate to 10-15 microns, newer spectral domain machines may approach 3 micron resolution. Spectral domain systems increase the signal-noise ratio by image averaging of multiple B-scans at the same location. This increased scan rate and number diminishes the likelihood of motion artifact, enhances the resolution and decreases the chance of missing lesions. Spectral domain technology, on the other hand, scans approximately 20,000-40,000 A-scans per second. Because the slices are 30 degrees apart, care must be taken to avoid missing pathology between the slices. Time domain systems acquire approximately 400 A-scans per second using 6 radial slices oriented 30 degrees apart. Swept Sourceįrom its inception, OCT images were acquired in a time domain fashion. the retina can be viewed through the pupil), OCT has gained wide popularity as an ophthalmic diagnostic tool. OCT was first introduced in 1991 and has found many uses outside of ophthalmology, where it has been used to image certain non-transparent tissues. OCT utilizes a concept known as inferometry to create a cross-sectional map of the retina that is accurate to within at least 10-15 microns. Optical Coherence Tomography (OCT) is a non-invasive diagnostic technique that renders an in vivo cross sectional view of the retina.
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