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Laurin Ginner, Cedric Blatter, Daniel Fechtig, Reinhard Told, Andreas Pollreisz, Ursula Schmidt-Erfurth, Rainer A Leitgeb; Advantage of large field-of-view high-speed OCT-Angiography in clinical application. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5463.
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© ARVO (1962-2015); The Authors (2016-present)
Demonstrating the improvement of OCT Angiography (OCT A) image quality for wide-field (16°) imaging of clinically relevant cases, by increasing the A-scan rate to 400kHz exploiting the spectral splitting (SP) method in swept source (SS) OCT (SPOCTA).
3D OCTA data were acquired with different A-scan rate settings: 70 kHz (spectral domain OCT, AngioVue at 840nm, 3x3 or 6x6mm FOV) and 2 prototype SSOCT at 1060 nm, 5x5mm FOV with 100 kHz and 400 kHz. The data have been acquired in 40 cases of age-related macular degeneration (AMD) patients including 22 cases of choroidal neovascularization (CNV) and 18 of geographic atrophy (GA). The swept source OCT system utilizes SP to double the lateral sampling and thereby increasing the A-scan rate to 400 kHz. We compare representative cases of CNV and GA with all systems and quantify the respective image signal-to-noise-ratio (SNR). For the 100 and 400kHz recordings full spectral data had been available. For the 70kHz recordings, only processed images after the SSADA algorithm and layer segmentation had been available. In all cases, the angiography algorithm was based on OCT intensity data.
The increase to 400kHz Ascan rate after applying SP allows extending the FOV from 8 to 16deg by maintaining the same lateral sampling rate and thus microvascular contrast and SNR. We determined an average SNR increase of 4 dB by changing from 100 kHz to 400 kHz keeping the same FOV. Large FOV is important for extended lesions as in the case of GA. With respect to structural details the 5x5mm FOV at 400kHz is in excellent agreement to the 100kHz 3x3mm FOV. On the other hand increasing the FOV from 3x3mm to 6x6mm keeping the same A-scan rate results in considerable degradation of structural detail. The method of SP allows using a commercial source operating at 200kHz and operating the OCTA at virtually 400kHz.
Our results based on SPOCTA demonstrate that a higher A-scan rate enhances the diagnostic capabilities by providing better signal contrast and structural detail. Especially in case of GA (Fig. 1), where the affected area in patients is commonly larger than the FOV of a standard OCT A modality (8°), the SPOCTA enables capturing the full pathologic region preserving microvascular details. The SPOCTA system is currently the fastest OCT angiography system based on a commercial SS.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure 1, shows a case of geographic atrophy (FOV 16°) recorded with SPOCTA.
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