Spectral Domain Optical Coherence Tomography: a Better OCT Imaging Strategy

Abstract

This paper reviews the current state of research in spectral domain optical coherence tomography (SDOCT). SDOCT is an interferometric technique that provides depth-resolved tissue structure information encoded in the magnitude and delay of the back-scattered light by spectral analysis of the interference fringe pattern. There are two approaches to SDOCT--one that uses a broadband source and a spectrometer to measure the interference pattern as a function of wavelength and the other that utilizes a narrowband tunable laser that is swept linearly in k approximately 1/lambda space during spectral fringe data acquisition. Unlike time domain (TD) OCT, the reference arm is stationary in both SDOCT methods, which allows for ultra high-speed OCT imaging. Owing to its high speed and superior sensitivity, SDOCT has become indispensable in biomedical imaging applications. After a brief introduction and a discussion on sensitivity advantage, methods of implementation of the two SDOCT schemes will be presented. The two peer approaches are compared in speed, scan depth range, complexity, spectral regions of operation, and methods of detection. The review also discusses OCT enhancements and functional methods based on SDOCT format and concludes with possible directions that this research may take in the near future.

Methods to assess sensitivity of optical coherence tomography systems

“…Since the early days of OCT, SNR has been calculated as [3][4][5][6][7] I samp is the background-subtracted image intensity from a reflecting object placed in the interferometer's sample arm, and σ bg is the standard deviation of the image background intensity (i.e., with no sample present). Squaring the signal and noise terms is needed to convert OCT image intensity values, proportional to the amplitude of the interference fringes resulting from cross-correlation of sample and reference fields, to power values.…”

“…Squaring the signal and noise terms is needed to convert OCT image intensity values, proportional to the amplitude of the interference fringes resulting from cross-correlation of sample and reference fields, to power values. From established formulas for the OCT image intensity [5,6,8], SNR is expected to be proportional to the sample reflectance R, shown in Eq. (2a) with proportionality constant K, which lumps light source intensity and system noise properties.…”

‘Go with the flow ’: A review of methods and advancements in blood flow imaging

“…Although FdOCT methods require more complex post-processing, they have great potential in terms of speed of acquisition and sensitivity. For a given N pixel-based SdOCT with a depth scan range of x depth ¼ N 2 l C , a TdOCT system acquiring signal over the same total time duration as an SdOCT system will have an signal-to-noise (SNR) ratio of [315]:…”

Improving Segmentation of 3D Retina Layers Based on Graph Theory Approach for Low Quality OCT Images

“…An older, the so-called Time Domain (TD) OCT technology, uses a movable mirror andfor registration -a photodiode [3]. Contemporary OCT devices are based on the Spectral Domain (SD) analysis, in which the mirror is fixed and a spectrometer is used as the recorder.…”