Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping

The retinal volumetric flow rate contains useful information not only for ophthalmology but also for the diagnosis of common civilization diseases such as diabetes, Alzheimer's disease, or cerebrovascular diseases. Non-invasive optical methods for quantitative flow assessment, such as Doppler optical coherence tomography (OCT), have certain limitations. One is the phase wrapping that makes simultaneous calculations of the flow in all human retinal vessels impossible due to a very large span of flow velocities. We demonstrate that three-dimensional Doppler OCT combined with three-dimensional four Fourier transform fast phase unwrapping (3D 4FT FPU) allows for the calculation of the volumetric blood flow rate in real-time by the implementation of the algorithms in a graphics processing unit (GPU). The additive character of the flow at the furcations is proven using a microfluidic device with controlled flow rates as well as in the retinal veins bifurcations imaged in the optic disc area of five healthy volunteers. We show values of blood flow rates calculated for retinal capillaries and vessels with diameters in the range of 12-150 µm. The potential of quantitative measurement of retinal blood flow volume includes noninvasive detection of carotid artery stenosis or occlusion, measuring vascular reactivity and evaluation of vessel wall stiffness

Imaging of the stroke-related changes in the vascular system of the mouse brain with the use of extended focus Optical Coherence Microscopy

We used Optical Coherence Microscopy (OCM) to monitor structural and functional changes due to ischemic stroke in small animals brains in vivo. To obtain lateral resolution of 2.2 μm over the range of 600 μm we used extended focus configuration of OCM instrument involving Bessel beam. It provided access to detailed 3D information about the changes in brain vascular system up to the level of capillaries across I and II/III layers of neocortex. We used photothrombotic stroke model involving photoactive application of rose bengal to assure minimal invasiveness of the procedure and precise localization of the clot distribution center. We present the comparative analysis involving structural and angiographic maps of the stroke-affected brain enabling in-depth insight to the process of development of the disorder

In vivo brain imaging with multimodal optical coherence microscopy in a mouse model of thromboembolic photochemical stroke

We used a new multimodal imaging system that combines optical coherence microscopy and brightfield microscopy. Using this in vivo brain monitoring approach and cranial window implantation, we three-dimensionally visualized the vascular network during thrombosis, with high temporal (18 s) and spatial (axial, 2.5 μm; lateral, 2.2 μm) resolution.We used a modified mouse model of photochemical thromboembolic stroke in order to more accurately parallel human stroke. Specifically, we applied green laser illumination to focally occlude a branch of the middle cerebral artery. Despite the recanalization of the superficial arteries at 24 h after stroke, no blood flow was detected in the small vessels within deeper regions. Moreover, after 24 h of stroke progression, scattering signal enhancement was observed within the stroke region. We also evaluated the infarct extent and shape histologically. In summary, we present a novel approach for real-time mouse brain monitoring and ischemic variability analysis. This multimodal imaging method permits the analysis of thrombosis progression and reperfusion. Additionally and importantly, the system could be used to study the effect of poststroke drug treatments on blood flow in small arteries and capillaries of the brain

Extended-focus optical coherence microscopy for high-resolution imaging of the murine brain

We propose a new method and optical instrumentation for mouse brain imaging based on extended-focus optical coherence microscopy. This in vivo imaging technique allows the evaluation of the cytoarchitecture at cellular level and the circulation system dynamics in three dimensions. This minimally invasive and non-contact approach is performed without the application of contrasting agents. The optical design achieved a resolution of 2.2 mu m over a distance of 800 mu m, which was sufficient to obtain a detailed three-dimensional image of a wild-type mouse's brain down to the layer III of the cortex. Intrinsically contrasted microvessels and structures similar to the bodies of neurons were distinguishable. (C) 2016 Optical Society of Americ

Visualization 1: Extended-focus optical coherence microscopy for high-resolution imaging of the murine brain

Fly-through across the whole 3D structural data set from the mouse brain after spatio-temporal averaging. Originally published in Biomedical Optics Express on 01 November 2016 (boe-7-11-4400