Sampling Volume Distribution
A quantified analysis of the optical reflectance of human skin is complicated by the fact that the blood and melanin content of skin tissues can vary both in the spatial distribution and in the amount. An understanding of which vascular bed is primarily responsible for the detected signal is required. Knowing the sampling volume (spatial detector depth sensitivity) makes it possible to find the best range of different probe geometries for the measurements of signal from the required depths and group of vessels inside the skin. Sampling volume is formed by so-called effective optical paths. When multiple photon packets travel between a light source and detector some trajectories are more likely to occur than others.
Current application imitates the sampling volume offered by a probe with a small source-detector spacing (~mm) applied to a human skin or to any other multi-layered medium. The source and detector areas can be overlapped or separated. The numerical aperture and angle of the detector positioning at the surface can be taken into account. For more details please see/refer the following papers below, where the current application has been originally developed.
I.V. Meglinski, A.V. Doronin, “Monte Carlo modeling for the needs of biophotonics and biomedical optics”, in: Advanced Biophotonics: tissue optical sectioning, Edited by V.V. Tuchin, R.K. Wang, Taylor & Francis, Chapter (2012)
I.V. Meglinski, S.J. Matcher, “Modeling the sampling volume for the skin blood oxygenation measurements”, Medical & Biological Engineering & Computing, Vol.39, No.:1, pp.44-50 (2001)
I.V. Meglinski, S.J. Matcher, “The analysis of spatial distribution of the detector depth sensitivity in multi-layered inhomogeneous highly scattering and absorbing medium by the Monte Carlo technique”, Optics & Spectroscopy, Vol.91, No.:4, pp.654-659 (2001)