Abstract
We show a novel technique to distinguish between Doppler shifted and unshifted light in multiple scattering experiments on mixed static and dynamic media. With a phase modulated low coherence Mach- Zehnder interferometer, optical path lengths of shifted and unshifted light and path length dependent Doppler broadening are measured in a two-layer tissue phantom, with a superficial static layer of different thickness covering a semi-infinite dynamic medium having identical optical properties. No Doppler broadening is observed until a certain optical path length depending on the thickness of the superficial static layer. From the minimum optical path length corresponding to the Doppler-shifted light the thickness of the static layer that overlies the dynamic layer can be estimated. Validation of the experimentally determined thickness of the static layer is done with the Doppler Monte Carlo technique. This approach has potential applications in discriminating between statically and dynamically scattered light in the perfusion signal and in determining superficial burn depths.
Highlights
Laser Doppler flowmetry (LDF), a non-invasive technique for monitoring blood microcirculation, characterizes the time-varying signal arising from the temporal variations in the speckle pattern to estimate the perfusion in biological tissues [1]
Optical path length distributions and path length resolved Doppler shifts of multiply scattered light are measured from a two-layer scattering phantom, with a superficial static layer of various thicknesses covering a dynamic medium with identical optical properties
We have developed a new method to discriminate between Doppler shifted and non-shifted multiply scattered light using phase-modulated coherence gated interferometry
Summary
Laser Doppler flowmetry (LDF), a non-invasive technique for monitoring blood microcirculation, characterizes the time-varying signal arising from the temporal variations in the speckle pattern to estimate the perfusion in biological tissues [1] In this technique, the coherent light delivered into the tissue through an optical fiber follows different trajectories and reaches different depths and is guided to the detector through a spatially separated lightcollecting fiber. For a constant perfusion, the LDF output signal is affected by probe induced variations and by the changes in the tissue optical properties in terms of absorption and scattering [2] This dependence leads to uncertainties in interpreting the Doppler shifted and non-shifted fraction of photons and in discriminating the fraction of light scattered from superficial (nutrient) and deeper (thermoregulatory) layers of skin. Coherence domain path length resolved optical Doppler perfusion monitoring, of which the basic technique is presented in this work, may overcome this limitation of conventional LDF techniques and will enable to correctly interpret the inter-and intra-individual variations in the LDF readings introduced by the variance in individual photon path lengths (e.g., length and depth) due to changes in tissue optical properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
