Dual-beam Doppler OCT for complete angle independent flow measurement

In vascular plexuses perpendicular to the optical axis, traditional Doppler OCT (DOCT) is highly sensitive to the Doppler angle, limiting its reproducibility and accuracy in clinical practice. A more stable approach is the dual-beam bidirectional technique that probes the sample from two distinct illumination directions allowing reconstruction of the true flow velocity and later the blood flow with knowledge of the vessel diameter. However the absolute velocity calculation still requires the evaluation of the flow angle in the en face plane. Based on dual beam bidirectional DOCT we suggest calculating the flow directly from an adequately chosen Doppler cross section and demonstrate that this method is independent of the vessel angle. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We confirm, with in vitro measurements of a perfused capillary and with a selected human retinal artery, that this method employing two beams only is completely independent of any vessel orientation.