2 March 2015 High-speed, digitally refocused retinal imaging with line-field parallel swept source OCT
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MHz OCT allows mitigating undesired influence of motion artifacts during retinal assessment, but comes in state-of-the-art point scanning OCT at the price of increased system complexity. By changing the paradigm from scanning to parallel OCT for in vivo retinal imaging the three-dimensional (3D) acquisition time is reduced without a trade-off between speed, sensitivity and technological requirements. Furthermore, the intrinsic phase stability allows for applying digital refocusing methods increasing the in-focus imaging depth range. Line field parallel interferometric imaging (LPSI) is utilizing a commercially available swept source, a single-axis galvo-scanner and a line scan camera for recording 3D data with up to 1MHz A-scan rate. Besides line-focus illumination and parallel detection, we mitigate the necessity for high-speed sensor and laser technology by holographic full-range imaging, which allows for increasing the imaging speed by low sampling of the optical spectrum. High B-scan rates up to 1kHz further allow for implementation of lable-free optical angiography in 3D by calculating the inter B-scan speckle variance. We achieve a detection sensitivity of 93.5 (96.5) dB at an equivalent A-scan rate of 1 (0.6) MHz and present 3D in vivo retinal structural and functional imaging utilizing digital refocusing. Our results demonstrate for the first time competitive imaging sensitivity, resolution and speed with a parallel OCT modality. LPSI is in fact currently the fastest OCT device applied to retinal imaging and operating at a central wavelength window around 800 nm with a detection sensitivity of higher than 93.5 dB.
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Daniel J. Fechtig, Daniel J. Fechtig, Abhishek Kumar, Abhishek Kumar, Laurin Ginner, Laurin Ginner, Wolfgang Drexler, Wolfgang Drexler, Rainer A. Leitgeb, Rainer A. Leitgeb, "High-speed, digitally refocused retinal imaging with line-field parallel swept source OCT", Proc. SPIE 9312, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XIX, 931203 (2 March 2015); doi: 10.1117/12.2081924; https://doi.org/10.1117/12.2081924

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