Abstract
Purpose :
To demonstrate that the joint Spectral and Time domain Optical Coherence Tomography method (STdOCT) with a three-dimensional fast phase unwrapping method (3D 4FT FPU) allows for fast calculation of blood flow rate in human optic disc area for capillaries and vessels with diameters in the range of 12-150 μm.
Methods :
Data was acquired using commercial spectral-domain OCT (RevoNX, Optopol Technology, Poland). The axial imaging resolution was 5 μm in tissue and the lateral imaging resolution was 12 μm. Arteriole, veins, and capillaries were segmented by a semiautomatic fitting an ellipse to XY cross-section of the vessel and minor axis of ellipse was considered to be the lumen of the vessel. To obtain axial velocity we used STdOCT which is a more sensitive variation of Doppler OCT. The range of unambiguous velocity estimation, limited by phase wrapping, was extended by phase unwrapping method we recently developed (4FT FPU). The blood flow rate was calculated using the integration of axial velocity of flow over the XY cross-section of vessels. We used a GPU as a data processing accelerator and utilized NVIDIA CUDA compiler 10.1 with the cuFFT library. 3D data set 1024×1024×256 was processed in GPU in time 1 s or 27 s for standard Doppler OCT and STdOCT, respectively.
Results :
The ability to calculate blood flow rate is proven on a microfluidic device with the controlled flow and on arteriole bifurcations in data acquired from five healthy subjects. For each subject distribution of flow in arterioles, veins and capillaries versus vessel lumen were calculated. The additive character of flow within human retinal vessels, as well as parabolic relation between flow and vessel diameter, are shown. The log-log dependence of human retinal flow versus vessel lumens presents high correlation of variables with a linear coefficient of determination of more than 0.80.
Conclusions :
The results show that STdOCT method with our unwrapping 3D 4FT FPU method is able to provide blood flow rate for arterioles, veins, and capillaries in the optic disc area and for vessel lumens as low as 12 μm. Since the retinal flow can be used as indicator of pathological changes in the vessels in the course of systemic disorders, the proposed technique has high potential to be applied to research and diagnostics of ocular and systemic diseases such as cardiovascular, diabetic retinopathy, artery or vein occlusions.
This is a 2020 ARVO Annual Meeting abstract.