Researchers at the Academic Medical Center (AMC-UvA) and the University of Amsterdam (UvA) have developed a method to measure the movement of particles in a liquid with high accuracy and speed. The scientists (Jeroen Kalkman (AMC-UvA), Ton van Leeuwen (AMC-UvA) and Rudolf Sprik (UvA)) used a Fourier-domain optical coherence tomography (OCT) setup. The method can be used in the future, among other things, to quantify blood flow in tissue. The results were published in Physical Review Letters on 5 November 2010.
Optical Coherence TomographyOCT makes images of the amount of diffuse light in tissue. This is achieved by lighting up the tissue with a broadband light source (which includes many different colors). Part of the light is directed through optical fibers to the target tissue. The light that comes back out, plus a portion of the original light, is then sent through a spectrometer and recorded by a speed camera. The recorded images are then analysed by the scientists using Fourier techniques.
DynamicsBy analysing the time dependent behavior as well as watching the static OCT images, the researchers measured - with high-speed recording and at different locations in the tissue - the particle dynamics and flow of fluids. The spontaneous movement of particles in the liquid (Brownian motion) provides information about the diffusion rate of these particles, and hence the viscosity (viscosity) of the surrounding liquid in different places. They demonstrated this by making pictures of the diffusion of particles in liquid in a tissue with a complex geometry.
Publication DetailsJ. Kalkman, R. Sprik, T. G. van Leeuwen: Path-Length-Resolved Diffusive Particle Dynamics in Spectral-Domain Optical Coherence Tomography. Phys. Rev. Lett. 105, 198302 (2010).