Citation:
Meglinsky I V, Matcher S J (2001) Modeling the sampling volume for the skin blood oxygenation measurements, Medical & Biological Engineering & Computing, 39 (1): 44-50, The Institution of Electrical Engineers
Abstract:
Abstract The absolute quantified measurement of haemoglobin skin blood
saturation from collected reflectance spectra of the skin is complicated by the
fact that the blood content of tissues can vary both in the spatial distribution
and in the amount. These measurements require an understanding of which vascular
bed is primarily responsible for the detected signal. Knowing the spatial
detector depth sensitivity makes it possible to find the best range of different
probe geometries for the measurements of signal from the required zones and
group of vessels inside the skin. To facilitate this, a Monte Carlo simulation
has been developed to estimate the sampling volume offered by fibre-optic probes
with a small source-detector spacing (in the current report 250 μm, 400 μm and
800 μm). The optical properties of the modelled medium are taken to be the
optical properties of the Caucasian type of skin tissue in the visible range of
the spectrum. It is shown that, for a small source-detector separation (800 μm
and smaller), rough boundaries between layers of different refractive index can
play a significant role in skin optics. Wavy layer interfaces produce a deeper
and more homogeneous distribution of photons within the skin and tend to
suppress the direct channelling of photons from source to detector. The model
predicts that a probe spacing of 250 μm samples primarily epidermal layers and
papillary dermis, whereas spacings of 400–800 μm sample upper blood net dermis
and