Laser & Optoelectronics Progress, Volume. 58, Issue 6, 600003(2021)
Theoretical Models of Light Distribution in Biological Tissues Irradiated by Laser
Figures & Tables(5)
Table 1. Meaning of physical quantities in equations in this paper
View tableTable 1. Meaning of physical quantities in equations in this paper
Parameter Physical meaning Parameter Physical meaning J Attenuated irradiance s’ Direction before scattering r=(r, z) Spatial location s Direction after scattering dω' Micro stereoangle in direction of s’ ρ Radial position vector θ Angle between s’ and s S Optical path length p Scattering phase function g Anisotropic factor Jc Coherent irradiance I0 Incident light intensity Jd Diffuse irradiance I Transmitted light intensity Q Photon source d Optical depth P Laser power φ Luminous flux density ω0 Spot radius φ0 Incident luminous flux density D Diffusion coefficient G Photon time dispersion τ Laser pulse duration t Calculating time μa Absorption coefficient R Specular reflectance μt Total attenuation coefficient μs Scattering coefficient L Physical thickness of sample c Speed of light in medium μs’ Reduced scattering coefficient μt’ Reduced attenuation coefficient ksc Scattered photon distribution h Spatial angular distribution function k Total photon distribution
Table 2. Comparison of characteristics of different accelerated MC methods
View tableTable 2. Comparison of characteristics of different accelerated MC methods
Method Acceleration relative to standard MC Relative error in simulated optical measurement Advantage Disadvantage SMC 200 Less than 4% No approximation is made, and it is accurate and fast Currently only be applicable to hierarchical organization models PMC 1300 Can be less than 4% , depending on magnitude of perturbation It is applicable to tissue with complex structures Sensitive to disturbances in scattering HMC 300 Around 5% It has a larger applicable range than PMC Calculation is relatively complex and specific area must be homogeneous Variance reduction 300 Around 5% There are a variety of choices available. Limitation varies with specific technique
Table 3. Classification and characteristic comparison of quantitative analysis methods
View tableTable 3. Classification and characteristic comparison of quantitative analysis methods
Quantitative analysis method Advantage Limitation First-order scattering When the diffuse anti-illumination rate is very small; the analytical solution can be obtained Limit to plane incident waves; not take multiple scattering into account; not be applicable for high scattering bands Monte Carlo simulation Consider the light loss of the sample edge that does not match the interface, any phase function of the medium, and the size and arbitrary angular distribution of the incident beam Because of its statistical reasons, it requires a lot of calculations and a long time to ensure good statistical convergence Beam broadening mode Most powerful solution for describing light distribution in approximate high forward scattering media Equivalent to MC method in accuracy Diffuse approximation High calculation speed and high precision;analytical solutions can be given in some specific cases Not be suitable for studying the light transmission and distribution near the light source and the marginal area of biological tissue Beam spreading function Consider the influence of higher-order photons propagating through paths of different lengths; allow to calculate the temporal dispersion of light intensity; much faster than MC method Not consider the wave characteristics of light Inverse adding-doubling Iterative solution it can be obtained quickly by computer; it can be used for more than one type of tissue block Can only be solved under the conditions of limited tissue thickness and uniform optical parameter distribution; the solution process is independent of time Kubelka-Munk Simple mathematical form Only be used for one-dimensional diffuse radiation with scattering far exceeding absorption;only be used be used be suitable for processing one-dimensional structural geometry; theoretical model is not perfect
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Lü Chenyang, Zhan Renjun. Theoretical Models of Light Distribution in Biological Tissues Irradiated by Laser[J]. Laser & Optoelectronics Progress, 2021, 58(6): 600003
Paper Information
Category: Reviews
Received: Jul. 14, 2020
Accepted: --
Published Online: Mar. 2, 2021
The Author Email: Renjun Zhan (zhanrenjun@aliyun.com)
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