April 21, 2017 Conference
OCTA and Doppler Techniques using Ultrahigh Speed Swept Source OCT
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Dr. James Fujimoto, Research Laboratory of Electronics / Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA (Presenter)
Speaker Session Topic
Recent advances in OCT technology enable dramatic increases in imaging speed. Swept source OCT (SS-OCT) can achieve speeds ~4-5x faster than current commercial spectral domain OCT (SD-OCT). In addition SS-OCT enables imaging at longer 1050nm wavelengths compared with SD-OCT at 840nm. Long wavelengths have increased immunity to ocular opacities as well as improved image penetration, enabling imaging of choroidal structure. The ultrahigh imaging speeds achieved by SS-OCT are important not only for improving retinal coverage, but also enable functional OCT imaging. OCT angiography (OCTA) detects motion contrast by performing repeated B-scans in the same retinal location and measuring decorrelation signals generated by moving erythrocytes. OCTA has the advantage that it generates three dimensional, depth resolved images of vasculature, but does not require dye injection and therefore can be performed rapidly and on every patient visit. However, since OCTA requires repeated scanning, extremely high acquisition speeds are required in order to achieve retinal coverage. OCTA using SS-OCT is especially promising for imaging of the choriocapillaris, detecting flow impairment and atrophy. Ultrahigh speeds also enable functional OCT methods for measuring total retinal blood flow. En face Doppler OCT measures blood flow in an en face plane by volumetrically scanning the central retinal vasculature. En face Doppler has the important advantage that determination of the Doppler angle is not required and flow can be measured using automated algorithms. However, ultrahigh speeds are required because flow measurements involve acquisition of OCT volumes rather than B-scan images as in standard Doppler OCT. In addition, rapidly repeated volumes are required to average cardiac pulsatility. We describe the development SS-OCT prototype technology at 400 kHz axial scan rates and its application for studies of age related macular degeneration and diabetic retinopathy.