Measurement of velocity profiles of red blood cells in the microcirculation by Laser Doppler Anemometry (LDA)1

Review of methodological developments in laser Doppler flowmetry

“…Moreover, a heat provocation test showed that green light was more sensitive to the changes in blood flow during vasodilatation and showed an increase in the high-frequency component in the power spectrum, whereas it falls in the case of red light. This observation was explained based on the results of Einav et al [38], which showed that, when vessel diameter increases, the more or less parabolic profile of the blood velocity becomes more flat-topped and shows an increase in velocity close to the vessel wall, in contrast to the velocity at the axis, which remains in the same range. Thus, green light, which probes the periphery of the larger microvessels only, due to a much larger absorption than that of red and near infrared light (Fig.…”

“…a Before vasodilation, blood flow shows a parabolic velocity profile (dotted line); green light probes only the periphery of the vessel, where the velocity is low. b Vasodilation produces a flat-topped velocity profile [38], where the green light probes mainly the wall region where the velocity has increased to a larger extent than in the center. In both situations red light probes a larger volume, covering a large part of the velocity profile, which makes the red light less sensitive to flow change than the green light the use of optical fibers and related motion artifacts.…”

In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system

“…In addition, the non-continuum behavior of blood flow through microvessels leads to complex flow mechanics, which are not yet clearly understood (Goldsmith and Turitto 1986, Secomb 1995, Mchedlishvili & Maeda 2001. Because several important physiological and pathological phenomena occur in the microcirculation, velocity profiles have been intensively studied both in vivo (Einav et al 1975, Tangelder et al 1986, Golster et al 1999, Parthasarathi et al 1999, Nakano et al 2003 and in vitro (Gaehtgens et al 1970, Baker & Wayland 1974, Born et al 1978, Cochrane et al 1981, Gaehtgens 1987, Uijttewaal et al 1994, Alonso et al 1995, Moger et al 2004, Kim & Lee 2006) using several blood flow measuring techniques. Both in vivo and in vitro experiments have played important roles in our understanding of several phenomena in the microcirculation.…”

“…Historically, the most commonly used experimental techniques to study blood flow in the microcirculation have been double-slit photometry (Gaehtgens et al 1970, Baker & Wayland 1974, video microscopy and image analysis (Bugliarello et al 1963, Tangelder et al 1986, Goldsmith and Turitto 1986, Gaehtgens 1987, Alonso et al 1995, Parthasarathi et al 1999, Tsukada 2000, and laserDoppler anemometry (Einav et al 1975, Born et al 1978, Cochrane et al 1981, Uijttewaal et al 1994, Golster et al 1999. However, with these techniques, both spatial resolution and velocity accuracy are unsatisfactory.…”

Speckles in laser Doppler perfusion imaging

“…Moreover a heat provocation test showed that green light is more sensitive to the changes of blood flow during vasodilatation, and showed an increase in the high frequency component in the power spectrum where as it falls in the case of red light. This observation was explained based on the results of Einav et al [38] which showed that when vessel diameter increases, the more or less parabolic blood velocity profile becomes more flattopped and shows an increase in velocity close to the vessel wall compared to the velocity at the axis which remains in the same range. So green light which probes the periphery of the larger microvessels only, due to a much larger absorption than red and near infrared light (Fig.…”