Absolute blood velocity measured with a modified fundus camera

Abstract

We present a new method for the quantitative estimation of blood flow velocity, based on the use of the Radon transform. The specific application is for measurement of blood flow velocity in the retina. Our modified fundus camera uses illumination from a green LED and captures imagery with a high-speed CCD camera. The basic theory is presented, and typical results are shown for an in vitro flow model using blood in a capillary tube. Subsequently, representative results are shown for representative fundus imagery. This approach provides absolute velocity and flow direction along the vessel centerline or any lateral displacement therefrom. We also provide an error analysis allowing estimation of confidence intervals for the estimated velocity.

Randomized controlled trial of electro‐stimulation therapies to modulate retinal blood flow and visual function in retinitis pigmentosa

“…The optical design, image registration, calibration, and results in human subjects have been previously described in detail. (Lemaillet et al 2010)(Duncan et al 2010)(Ibrahim et al 2015) This approach relies on tracking the non-uniform distribution of red blood cells within the capillary, and is capable of dealing with very low signal-to-noise ratios. Vessel diameter and blood velocity were used to calculate mean flow velocity [MFV =((((Diameter/2) 2 )*π)/1000)*velocity] as a measure of RBF.…”

Use of Mueller matrix polarimetry and optical coherence tomography in the characterization of cervical collagen anisotropy

“…The Radon transform projects the sum of image intensities along the different orientation angles inputted into the transformation. 55 Five X-Y images (c-scans) were first averaged in the Z-direction to improve the orientation measurements across a depth of 40 μm. The c-scans were then smoothed with a 3 × 3 median filter to remove speckle noise.…”

Expanding Applications, Accuracy, and Interpretation of Laser Speckle Contrast Imaging of Cerebral Blood Flow

“…Generally, optical techniques for measuring of cerebral blood flow (CBF) either rely on spatio-temporal tracking of blood cells or use of dynamic light scattering (DLS). The former include laser scanning microscopy, 1 , 2 high speed red blood cell (RBC) photography, 3 , 4 and recently RBC-optical coherence tomography. 5 Dynamic light scattering techniques include laser Doppler flowmetry (LDF), 6 , 7 diffuse correlation spectroscopy, 8 , 9 DLS-optical coherence tomography, 10 and laser speckle contrast imaging (LSCI).…”