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Ocular OCT retinal thickness map, right eye Time-domain OCT of the macular area of a retina at 800 nm, axial resolution 3 μm Spectral-domain OCT macula cross-section scan. Optical coherence tomography (OCT) is a technique for obtaining sub-surface images of translucent or opaque materials at a resolution equivalent to a low-power microscope.
The same disadvantages occur when using the spectrogram method to do in vivo tissue structure and flow velocity imaging, as spectral-domain OCT is limited to fast imaging. Phase-resolved Doppler OCT, based around the invention of Fourier-Domain OCT, was invented to overcome these limitations. [1]
SV-OCT can be done with spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). [5] SD-OCT and SS-OCT are both methods of Fourier domain OCT (FD-OCT), which has significantly faster image acquisition speed compared to time domain OCT. In general, OCT measures the echo time delay and intensity of reflected and backscattered light.
Both the spatial domain and spectral domain descriptions of the collected OCT signal, can be related by Fourier transformation: = | {()} | where is the Fourier transform. However, due to the wavelength dependence with depth for both scattering and absorption in tissue, direct Fourier transform cannot be applied to obtain localized spectroscopic ...
A short scan time prevents too much patient movement during signal acquisition. With the development of Fourier-domain OCT, spectral-domain OCT, and swept source signal acquisition time was greatly improved making OCTA possible. [40] OCTA scan time is now around three seconds, however, saccadic eye movement still causes a low signal-to-noise ratio.
The time for light to be reflected back from the tissue under inspection is used to measure distances. However, due to the high speed of light, the backreflection time cannot be measured directly, but is instead measured using interferometry. [4] OCT is measured using either time domain (TD-OCT) or frequency domain techniques (FD-OCT ...
Then, in order to filter the reference pulse in the time domain, the main portion of the pulse is used for cross-polarized wave generation (XPW) in a nonlinear crystal. [21] The interference between the reference pulse and the mirror image is recorded and analyzed via Fourier transform spectral interferometry (FTSI). [6]
Time-domain diffuse optics [1] or time-resolved functional near-infrared spectroscopy is a branch of functional near-Infrared spectroscopy which deals with light propagation in diffusive media. There are three main approaches to diffuse optics namely continuous wave [ 2 ] (CW), frequency domain [ 3 ] (FD) and time-domain [ 4 ] (TD).