Theoretical Models of Light Distribution in Biological Tissues Irradiated by Laser

Lü Chenyang; Zhan Renjun

doi:10.3788/LOP202158.0600003

Journals >Laser & Optoelectronics Progress >Volume 58 >Issue 6 >Page 600003 > Article

Laser & Optoelectronics Progress
Vol. 58, Issue 6, 600003 (2021)

Theoretical Models of Light Distribution in Biological Tissues Irradiated by Laser

Lü Chenyang and Zhan Renjun^*

Author Affiliations

College of Equipment Management and Support, Engineering University of People’s Armed Police, Xi''an, Shaanxi 710086, China

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DOI: 10.3788/LOP202158.0600003 Cite this Article Set citation alerts

Lü Chenyang, Zhan Renjun. Theoretical Models of Light Distribution in Biological Tissues Irradiated by Laser[J]. Laser & Optoelectronics Progress, 2021, 58(6): 600003 Copy Citation Text

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Fig. 1. Dynamic analysis model of photothermal effect of biological tissues

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Fig. 2. Hierarchical structure of photon transport theory

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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
J_c	Coherent irradiance	I₀	Incident light intensity
J_d	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
μ_a	Absorption coefficient	R	Specular reflectance
μ_t	Total attenuation coefficient	μ_s	Scattering coefficient
L	Physical thickness of sample	c	Speed of light in medium
μ_s_’	Reduced scattering coefficient	μ_t’	Reduced attenuation coefficient
k_sc	Scattered photon distribution	h	Spatial angular distribution function
k	Total photon distribution

Table 1. Meaning of physical quantities in equations in this paper

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 tissuewith complex structures	Sensitive to disturbances in scattering
HMC	300	Around 5%	It has a larger applicablerange than PMC	Calculation is relatively complex and specific area must be homogeneous
Variancereduction	300	Around 5%	There are a variety ofchoices available.	Limitation varies withspecific technique

Table 2. Comparison of characteristics of different accelerated MC 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

Table 3. Classification and characteristic comparison of quantitative analysis methods

Lü Chenyang, Zhan Renjun. Theoretical Models of Light Distribution in Biological Tissues Irradiated by Laser[J]. Laser & Optoelectronics Progress, 2021, 58(6): 600003

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