A novel, microscope based, non-invasive laser Doppler flowmeter for choroidal blood flow assessment

Abstract

Impaired ocular blood flow is involved in the pathogenesis of numerous ocular diseases like glaucoma or AMD. The purpose of the present study was to introduce and validate a novel, microscope based, non invasive laser Doppler flowmeter (NILDF) for measurement of blood flow in the choroid. The custom made NI-LDF was compared with a commercial fiber optic based laser Doppler flowmeter (Perimed PF4000). Linearity and stability of the NI-LDF were assessed in a silastic tubing model (i.d. 0.3 mm) at different flow rates (range 0.4 – 3 ml/h). In a rabbit model continuous choroidal blood flow measurements were performed with both instruments simultaneously. During blood flow measurements ocular perfusion pressure was changed by manipulations of intraocular pressure via intravitreal saline infusions. The NILDF measurement correlated linearly to intraluminal flow rates in the perfused tubing model (r = 0.99, p<0.05) and remained stable during a 1 hour measurement at a constant flow rate. Rabbit choroidal blood flow measured by the PF4000 and the NI-LDF linearly correlated with each other over the entire measurement range (r = 0.99, y = x* 1,01 – 12,35 P.U., p < 0,001). In conclusion, the NI-LDF provides valid, semi quantitative measurements of capillary blood flow in comparison to an established LDF instrument and is suitable for measurements at the posterior pole of the eye.

High-resolution in-situ LDV monitoring system for measuring velocity distribution in blood vessel

“…In LDV, which detects the Doppler shift frequency in a single laser beam, blood flow parameters are estimated by integrating the spectrum of the optical signal [31,32]. The number of moving red cells (N) in the measurement volume is proportional to the integral of the Doppler power spectrum [P(f)], which can be obtained as follows:…”

Effect on vascular permeability of a self-etching adhesive system containing an antimicrobial quaternary ammonium polymer QAMP into subcutaneous tissue of rats

“…22 When laser light is directed into a tissue, the light is scattered by both stationary tissue matrix and moving elements in the blood vessels, mainly red blood cells. 23 Light scattered by the tissue matrix retains its original frequency whereas light scattered by blood components is Doppler shifted. 23 Spectral analysis can determine the average frequency shift as an index of the average velocity of the blood cells and the extent of spectral broadening as an index of the number of moving blood cells generating Doppler events, which are designated as blood volume or concentration of moving blood cells (CMBC).…”

“…23 Light scattered by the tissue matrix retains its original frequency whereas light scattered by blood components is Doppler shifted. 23 Spectral analysis can determine the average frequency shift as an index of the average velocity of the blood cells and the extent of spectral broadening as an index of the number of moving blood cells generating Doppler events, which are designated as blood volume or concentration of moving blood cells (CMBC). 23 In microcirculation, the product of average velocity times the concentration of moving blood cells is the flux of blood within the sampling volume of the tissue.…”

“…23 Spectral analysis can determine the average frequency shift as an index of the average velocity of the blood cells and the extent of spectral broadening as an index of the number of moving blood cells generating Doppler events, which are designated as blood volume or concentration of moving blood cells (CMBC). 23 In microcirculation, the product of average velocity times the concentration of moving blood cells is the flux of blood within the sampling volume of the tissue. 23 During the exudative phases of inflammatory process, microcirculation is changed which alters the velocity and the number of moving blood cells.…”

“…23 In microcirculation, the product of average velocity times the concentration of moving blood cells is the flux of blood within the sampling volume of the tissue. 23 During the exudative phases of inflammatory process, microcirculation is changed which alters the velocity and the number of moving blood cells. Consequently, laser-Doppler flowmetric procedure is a feasible method to investigate differences in vascular permeability.…”