Abstract
We present a numerical spectroscopic study of visible and infrared laser radiation in a biological tissue. We derive a solution of a general two-dimensional time dependent radiative transfer equation in a tissue-like medium. The used model is suitable for many situations especially when the external source is time-dependent or continuous. We use a control volume-discrete ordinate method associated with an implicit three-level second-order time differencing scheme. We consider a very thin rectangular biological-tissue-like medium submitted to a visible or a near infrared light sources. The RTE is solved for a set of different wavelength source. All sources are assumed to be monochromatic and collimated. The energetic fluence rate is computed at a set of detector points on the boundaries. According to the source type, we investigate either the steady-state or transient response of the medium. The used model is validated in the case of a heterogeneous tissue-like medium using referencing experimental results from the literature. Also, the developed model is used to study changes on transmitted light in a rat-liver tissue-like medium. Optical properties depend on the source wavelength and they are taken from the literature. In particular, light-transmission in the medium is studied for continuous wave and for short pulse.
Highlights
Diffuse light imaging and spectroscopy aims to investigate tissue physiology in subsurface
Spectroscopy is useful for measurement of time-dependent variations in the absorption and scattering of large tissue volumes
We have considered a case of 678 nm-light punctual continuous wave source
Summary
Diffuse light imaging and spectroscopy aims to investigate tissue physiology in subsurface. The absorption of hemoglobin and water is small in the near-infrared, but elastic scattering from organelles and other microscopic interfaces is large. Any measuring is devoted for either spectroscopy or imaging. Spectroscopy is useful for measurement of time-dependent variations in the absorption and scattering of large tissue volumes. Photon propagation in a biological tissue is affected by absorption and scattering. A computational light propagation model which describes the interaction of photons with scattering and absorbing media is essential in biomedical optics. It is useful for setting optical tissue properties and for the development of optical imaging algorithms [4,5,6,7,8]
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