Model for laser Doppler measurements of blood flow in tissue

Abstract

A theory is developed which relates quasi-elastic light scattering measurements to blood flow in tissue micro-vasculature. We assume that the tissue matrix surrounding the blood cells is a strong diffuser of light and that moving erythrocytes, therefore, are illuminated by a spatially distributed source. Because the surrounding tissue is considered to be stationary, Doppler shifts in the frequency of the scattered light arise only from photon interactions with the moving blood cells. The theory implies that the time decay of the photon autocorrelation function scales proportionally with cell size and inversely with mean translational speed. Analysis of multiple interactions of photons with moving cells indicates the manner in which spectral measurements additionally are sensitive to changes in blood volume. Predictions are verified by measurements of particle flow in model tissues.

An in-shoe laser Doppler sensor for assessing plantar blood flow in the diabetic foot

“…A simple flow rig of the type described in chapter four was used to calibrate the plantar monitoring system. To facilitate comparison with published data, flow and concentration variables were matched to those used by Obied (1993), in evaluation of the signal processing algorithm of Bonner and Nossal (1981). The same frequency weighted algorithm is used for calculating the flux response in the present system.…”

“…Absorption spectra for the skin are given in figure 5. The structure and composition of skin tissue results in a very high coefficient of scattering (Van der Zee 1993) with a mean distance between scattering events, termed the scattering length of -10ORm (Bonner and Nossal 1981). Consequently, light is scattered diffusely within the tissue forming a scattered field.…”

“…Subsequently, the results obtained for identical measurement conditions were found to differ from one system to another. To overcome this problem a theoretical model of light scattering in tissue was developed by Bonner and Nossal (1981). This work resulted in an algorithm that produced a single output parameter 'blood flux' that scaled linearly with red blood cell velocity and concentration over a limited range.…”

Dexmedetomidine-induced decrease in cerebral blood flow is attenuated by verapamil in rats: a laser Doppler study

“…The measurement volume is approximately 1 mm3. [30][31][32] All measurements were performed with a frequency cutoff at 20 kHz and a time constant of 0.2 sec.…”

Cortical Microcirculation in a New Model of Focal Laser-Induced Secondary Brain Damage

“…The theoretical basis and the validity of LDF in addition to the stability of this instrument have previously been documented (Shepherd et ai., 1987;Skarphedinsson et ai., 1988;Haberl et ai., 1989;Lindsberg et ai., 1989). Although the exact volume of the monitored tissue in the CNS still needs further definition, LDF estimates are generally accepted to rep resent approximately 1-2 mm3 of tissue directly under neath the probe (Bonner and Nossal, 1981). at each time (3 min, 2 h, and 8 h).…”