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Cedric Blatter, Laurin Ginner, Amardeep S. Singh, Tilman Schmoll, Leopold Schmetterer, Rainer A. Leitgeb; Dual Beam Doppler Optical Coherence Tomography at 1060nm. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2188.
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© ARVO (1962-2015); The Authors (2016-present)
To image the blood flow dynamics quantitatively independent of the axial Doppler angle and to contrast the vasculature network of the retina with high penetration using a Dual Beam Doppler Swept Source OCT System at 1060nm.
Traditional Doppler OCT is highly sensitive to motion artifacts due to the dependence on the Doppler angle. This limits its reproducibility in clinical practice. To overcome this limitation, we use a bidirectional technique. Here, the volume is probed from two distinct illumination directions, allowing reconstruction of the true flow velocity. The principle was implemented with Swept Source OCT at 100,000 A-Scans/s. Furthermore, measurement at 1060nm shows better penetration below the RPE, so that choroidal flow can be effectively quantified. Simple flow contrast can be achieved by calculating the phase variance between successive B-scans. The dual beam approach permits intrinsic bulk motion correction and offers the advantage to contrast the full range of flow present at the retina from small capillaries up to large vessels at the ONH.
Circumpapillary Doppler OCT scan series over time have been recorded for three healthy volunteers. The angle independent quantitative flow dynamics have been extracted from specific vessel cross-sections of arteries and veins. The quantitative analysis profits from the intrinsic stability with respect to motion over time. The flow values fit well with previous findings. Furthermore we assessed choroidal flow quantitatively in selected vessel cross-section close to the optic nerve head. This marks an important step since the choroidal perfusion is believed to play an important role for retinal health and disease. Highly sensitive flow contrasting based on phase variance has been performed on the parafoveal capillary network of the inner retina in a patch of 1.5x1.5mm. Capillaries smaller than 10µm could be well visualized. The sensitivity benefits greatly from the bulk motion independence of the dual beam approach.
We introduce a large penetration bidirectional Doppler OCT system capable to perform quantitative imaging of retinal flow dynamics in the human retina. We demonstrated the advantage of 1060nm center wavelength to assess quantitatively the choroidal perfusion that plays a major role for various retinal diseases. The flow quantification and visualization may therefore lead ultimately to a better understanding and an enhanced early diagnosis of major retinal diseases.
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