Optical properties of bovine ocular tissues were determined at laser wavelengths in the visible region. The inverse adding doubling (IAD), Kubelka–Munk (KM), and inverse Monte Carlo (IMC) methods were applied to the measured values of the total diffuse transmission, total diffuse reflection, and collimated transmission to determine the optical absorption and scattering coefficients of the bovine cornea, lens and retina at 457.9 nm, 488 nm, and 514.5 nm laser lines from an argon ion laser. The optical properties obtained from these three methods were compared, and their validity is discussed.
The optical properties of human whole blood and blood plasma with and
without Y2O3 and
Nd3+:Y2O3 nanoparticles are characterized
in the near infrared region at 808 nm using a double integrating sphere
technique. Using experimentally measured quantities of diffuse reflectance and
diffuse transmittance, a computational analysis was conducted utilizing the
Kubelka-Munk, the Inverse Adding Doubling, and Magic Light Kubelka-Munk and
Monte Carlo Methods to determine optical properties of the absorption and
scattering coefficients. Room temperature absorption and emission spectra were
also acquired of Nd3+:Y2O3 nanoparticles
elucidating their utility as biological markers. The emission spectra of
Nd3+:Y2O3 were taken by exciting the
nanoparticles before and after entering the whole blood sample. The emission
from the 4F3/2→4I11/2
manifold transition of Nd3+:Y2O3 nanoparticles
readily propagates through the blood sample at excitation of 808 nm and exhibits
a shift in relative intensities of the peaks due to differences in scattering.
At 808 nm, in both whole blood and plasma samples, a direct relationship was
found with absorption coefficient and Y2O3 nanoparticle
concentration. Results for the whole blood indicate a small inverse relationship
with Y2O3 nanoparticle concentration and scattering
coefficient and in contrast a direct relation for the plasma.
Since its invention in the early 1960’s, the laser has been used as a tool for surgical, therapeutic, and diagnostic purposes. To achieve maximum effectiveness with the greatest margin of safety it is important to understand the mechanisms of light propagation through tissue and how that light affects living cells. Lasers with novel output characteristics for medical and military applications are too often implemented prior to proper evaluation with respect to tissue optical properties and human safety. Therefore, advances in computational models that describe light propagation and the cellular responses to laser exposure, without the use of animal models, are of considerable interest. Here, a physics-based laser-tissue interaction model was developed to predict the dynamic changes in the spatial and temporal temperature rise during laser exposure to biological tissues. Unlike conventional models, the new approach is grounded on rigorous electromagnetic theory that accounts for wave interference, polarization, and nonlinearity in propagation using a Maxwell’s equation-based technique.
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