Abstract: The spectral reflectance measurements in tissue reveal physiological
meaning. Normally, functional changes like, increase in total hemoglobin
concentration, decrease in oxygen saturation, etc., are observed when there is
an abnormality creeping in the normal tissue. These functional changes can act
together to reveal disease by non-invasive near-infrared (NIR) spectroscopy, as
it influence its optical properties. In the present study, a simple two
dimensional, four layer model of breast is proposed. The four layers are (i)
skin (ii) adipose layer (iii) glandular tissue and (iv) muscle. Each layer is
modeled with appropriate biological chromophores like hemoglobin, water, lipid
and melanin. From the literature, the concentrations and molar extinction
coefficients of the chromophores in various layers of the model are obtained.
These values are used to calculate the wavelength dependent absorption
characteristics of a particular layer. Monte Carlo simulation of diffuse
reflectance (percentage of back reflected photons after multiple scattering
with the broad variety of angles) are simulated for the modeled breast tissue
with and without diseased condition. Near-infrared wavelengths are chosen, as
the depth of penetration in tissue is more compared to UV and visible region.
Simulations are carried out on the modeled breast tissue for different races
(skin colors) at different NIR wavelengths. Results show significant changes in
diffuse reflectance and relative absorbance for normal and diseased breast
tissues for differently pigmented model. This model can be used to study the
photo dynamical therapy, drug delivery and prognosis of cancer.
Keywords: Diffuse reflectance, chromophores, modeling and Monte Carlo simulations
Journal: BioFactors, vol. 30, no. 4, pp. 255-263, 2007
