Assessing flow impairment using ultrahigh speed
swept source OCT angiography
James G. Fujimoto, Ph.D.
Elihu Thomson Professor of Electrical Engineering and Computer Science
Department of Electrical Engineering and Computer Science and
Research Laboratory of Electronics
Massachusetts Institute of Technology, Cambridge, MA 02139
Swept source OCT (SS-OCT) can achieve faster imaging speeds than spectral domain OCT (SD-OCT) as well as image at longer 1050nm wavelengths which have reduced attenuation. Increased imaging speed is especially important for OCT angiography (OCTA) because protocols require repeated scanning of the same retinal position to detect blood flow. Research SS-OCT instruments can operate at 400kHz axial scan rates, 4-5x faster than current commercial technology. High speeds enable OCTA to be acquired not only over wider fields of view, but also enable advanced OCTA acquisition protocols which use large numbers of repeated scans and assess blood cell motion using different interscan times. Longer interscan times which are used in most commercial instruments have high sensitivity to slow blood flow, but cannot distinguish differences between faster flows or detect flow impairment. High speed enables shorter interscan times which can detect flow impairment, but trade off sensitivity to slow flows. Variable interscan time analysis (VISTA) has the advantage that it can distinguish differences between fast flows while preserving sensitivity to slow flows. We describe the application of these methods to detect flow impairment of the retinal and choroidal vasculature in age related macular degeneration and diabetic retinopathy as well as present methods to quantitatively assess flow impairment.
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Research support from Topcon.