10 Photon-Tissue Interaction Modelled by Monte Carlo Method …
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Fig. 10.10 Sensor sensitivity dI in relation to skin depths for different wavelengths. Using infrared
light the penetration depth can be increased by a factor of 3 compared to green illumination [11]
measures the upper skin layers up to a depth of about 0.3 mm will provide measurements solely of the skin microcirculation. While sensors utilizing red or infrared light
will additionally collect information of deeper and larger vessels in the skin and thus
gather information of the macrocirculation.
10.8 Dynamic MC Simulations
Due to increasing computing power also parameterized simulations can be done.
In repeated simulation runs different scenario properties can be changed. As an
example, the blood volume contents in the capillary layer have been chosen as
dynamic parameters.
These dynamic simulation runs thus model the contraction of one heartbeat. It will
result mainly in an increase of blood volume in the capillaries by about 10%, which is
from 4% to 4.4%. Figure 10.11 shows the simulation results. With increasing blood
volume the light intensity at the detector will decrease due to increased absorbance
in the skin.