Abstract
We developed a three-beam Doppler optical coherence tomography (OCT) system that enables measurement of the velocity vector of moving particles in three-dimensions (3-D). The spatial orientation as well as the magnitude of motion can be determined without prior knowledge of the geometry of motion. The system combines three spectral-domain OCT interferometers whose sample beams are focused at the sample by a common focusing lens at three different angles. This provides three spatially independent velocity components simultaneously from which the velocity vector can be reconstructed. We demonstrate the system in a simple test object (rotating disc), a flow phantom, and for blood flow measurements in the retina of a healthy human subject. Measurements of blood flow at a venous bifurcation achieve a good agreement between in- and outflow and demonstrate the reliability of the method.
Highlights
Optical coherence tomography (OCT) was introduced more than two decades ago[1] as a noninvasive modality for imaging transparent and translucent tissues with a resolution of a few micrometers.[2,3] The first application field of OCT was ophthalmology, where OCT revolutionized retinal imaging and diagnostics.[4,5] In the later years, several functional extensions of OCT were developed, one of the most promising being Doppler OCT (DOCT)[6,7,8] which provides information on the movement of backscattering particles
The vessel diameters were measured to be between 0.12 and 0.17 mm while the total flow rate in the respective vessels showed a range of 0.11–0.31 μl∕s. These results are in good agreement with the results found in the literature: measurements done with laser Doppler velocimetry (LDV)[49] suggest total flow rates of 0.10–0.25 μl∕s for the same vessel diameter range
We developed a new three-beam DOCT system that allows the 3-D reconstruction of flow orientation and the determination of the absolute flow velocity, without the need for information on the orientation of the vessel
Summary
Optical coherence tomography (OCT) was introduced more than two decades ago[1] as a noninvasive modality for imaging transparent and translucent tissues with a resolution of a few micrometers.[2,3] The first (and still dominating) application field of OCT was ophthalmology, where OCT revolutionized retinal imaging and diagnostics.[4,5] In the later years, several functional extensions of OCT were developed, one of the most promising being Doppler OCT (DOCT)[6,7,8] which provides information on the movement of backscattering particles. Since major eye diseases such as diabetic retinopathy and glaucoma, as well as disorders such as retinal branch vein occlusion, are associated with alterations in blood perfusion, DOCT is of special interest for ophthalmic imaging. A variety of different DOCT techniques have been reported in the literature. Examples are time domain-based optical Doppler tomography,[9] phase-resolved DOCT (PR-DOCT),[10,11,12,13] resonant Doppler flow imaging,[14] joint spectral and time domain imaging,[15,16] optical micro-angiography[17,18] or single-pass volumetric bidirectional blood flow imaging.[19]
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