Biophotonics involves understanding how light interacts with biological matter, from molecules and cells, to tissues and even whole organisms. Light can be used to probe biomolecular events, such as gene expression and protein–protein interaction, with impressively high sensitivity and specificity. The spatial and temporal distribution of biochemical constituents can also be visualized with light and, thus, the corresponding physiological dynamics in living cells, tissues, and organisms in real time. Computer-based Monte Carlo (MC) models of light transport in turbid media take a different approach. In this paper, the optical and structural properties of biomaterials discussed. We explain the numerical simulationmethod used for studying the optical properties of biomaterials. Applications of the Monte-Carlo method in photodynamic therapy, skin tissue optics, and bioimaging described.
In this work, we report on two different and very efficient approaches for modelling of Raman scattering in turbid media irradiated by laser light. Both approaches utilize the Monte-Carlo method to simulate the Raman scattering process and optimized for different application scenarios. We compare the efficiency of both approaches and experimental results for confocal Raman spectroscopy.
The aim of this work was to evaluate the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed ultraviolet (UV) laser (λ=337 nm ) and a continuous-wave (cw) visible laser beam (λ=632.8 nm ) using Monte Carlo modeling. Finite-element methodology was used for heat transfer simulation. The analysis of the results showed that heat is not localized on the surface, but is collected inside the tissue in lower skin layers. The simulation was made with the pulsed UV laser beam (used as excitation source in laser-induced fluorescence) and the cw visible laser (used in photodynamic therapy treatments), in order to study the possible thermal effects.
Continuous-wave laser micro-beams are generally used as diagnostic tools in laser scanning microscopes or in the case of near-infrared (NIR) micro-beams, as optical traps for cell manipulation and force characterization. Because single beam traps are created with objectives of high numerical aperture, typical trapping intensities and photon flux densities are in the order of 106 W/cm2 and 103 cm-2s-1, respectively. The main idea of our theoretical study was to investigate the thermal reaction of RBCs irradiated by laser micro-beam. The study is supported by the fact that many experiments have been carried out with RBCs in laser NIR tweezers. In the present work it has been identified that the laser affects a RBC with a density of absorbed energy at approximately 107 J/cm3, which causes a temperature rise in the cell of about 7 – 12 °C.
Laser induced fluorescence spectroscopy and photodynamic therapy (PDT) are techniques currently introduced
in clinical applications for visualization and local destruction of malignant tumours as well as premalignant lesions.
During the laser irradiation of tissues for the diagnostic and therapeutic purposes, the absorbed optical energy generates
heat, although the power density of the treatment light for surface illumination is normally low enough not to cause any
significantly increased tissue temperature.
In this work we tried to evaluate the utility of Monte Carlo modeling for simulating the temperature fields and
the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed UV
laser and a continuous wave visible laser beam. The analysis of the results showed that heat is not localized on the
surface, but it is collected inside the tissue. By varying the boundary conditions on the surface and the type of the laser
radiation (continuous or pulsed) we can reach higher than normal temperature inside the tissue without simultaneous
formation of thermally damaged tissue (e.g. coagulation or necrosis zone).
Usually biological tissue has complex geometry. In earlier works we used simple skin model with a number of horizontal
layers. In this work we use the model that approximates complex objects. For example, cancerous growth consists of
many layers which can be of different forms, for inter alia blood vessels. In this work we attempted to elaborate a
mathematical model of thermal response of laser irradiated multilayered biological tissue. Every layer has its own optical
and physical characteristics. We used Monte-Carlo simulation to calculate the propagation of light (laser beams) in tissue
and receive the heat source function. As we usually have radial symmetric laser beams we use cylindrical coordinates.
The solution of the 2D heat conduction equation is based on finite-element theory with the use a predefined number of
finite elements. We simulated constant and pulse laser irradiation and as result there are temperature fields and the
dynamics of heat conduction. Analysis of the results shows that heat is not localized on the surface, but is collected
inside the tissue. By varying the boundary condition on the surface and type of laser irradiation (constant or pulse) we
can reach high temperature inside the tissue without simultaneous formation of necrosis.
In this work we tried to create a mathematical model of thermal response of laser irradiated multilayer biological tissue.
The tissue has 4 horizontal radial symmetric layers with its own optical-physical characteristics. We used the results of
Monte Carlo modeling to describe the propagation of light (laser beams) in tissue and receive the function of heat source
after we multiply the density of thermal emission by absorption coefficient. As we usually have radial symmetric laser
beams we can use cylindrical coordinates. The solution of the 2D heat conduction equation is based on finite-element
theory with using square finite elements. We simulated constant laser fluency and as result there are temperature fields.
The analysis of the results represents, that heat does not localize on the surface, but collects inside of the tissue. By
varying the boundary condition on the surface and type of laser irradiation we can reach high temperature inside the
tissue without formation of necrosis at the same time.