Measurement of particle flux in a static matrix with suppressed influence of optical properties, using low coherence interferometry.
Perfusion measurements using conventional laser Doppler techniques are affected by the variations in tissue optical properties. Differences in absorption and scattering will induce different path lengths and consequently will alter the probability that a Doppler shift will occur. In this study, the fraction of Doppler shifted photons and the Doppler broadening of a dynamic medium, are measured with a phase modulated low coherence Mach-Zehnder interferometer. Path length-resolved dynamic light scattering measurements are performed in various media having a constant concentration of dynamic particles inside a static matrix with different scattering properties and the results are compared with a conventional laser Doppler technique, with a simple model and with Monte Carlo simulations. We demonstrate that, for larger optical path lengths, the scattering coefficient of the static matrix in which the moving particles are embedded have a small to minimal effect on the measured fraction of Doppler shifted photons and on the measured average Doppler frequency of the Doppler shifted light. This approach has potential applications in measuring perfusion independent of the influence of optical properties in the static tissue matrix.
Varghese
Babu
B
MIRA Institute for Biomedical Technology and Technical Medicine, Biophysical Engineering Group, University of Twente, PO Box 217, NL-7500AE Enschede, The Netherlands. babu.varghese@philips.com
Rajan
Vinayakrishnan
V
Van Leeuwen
Ton G
TG
Steenbergen
Wiendelt
W
D007368:Interferometry / Q000379:methods*; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008863:Microspheres; D009010:Monte Carlo Method; D055620:Optical Phenomena; D017785:Photons