A refined diffusion model of the interaction of laser radiation with biological tissue

Tereshchenko, S. A.; Данилов, А. А.; Podgaetsky, Vitaly M.

doi:10.1134/s0030400x07050207

Cited by 9 publications

(8 citation statements)

References 5 publications

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“…(3) requires an additional assump tion (type of RTE, solution type, properties of medium, etc.). RTE can be solved using the enhanced diffusion model (EDM) [6]. In contrast to the classical diffusion model [4], the EDM provides accurate description of the interaction of laser radiation with scattering medium (HSM with thickness of free motion order).…”

Section: Theorymentioning

confidence: 99%

Simultaneous Determination of Extinction and Scattering Coefficients of Highly Dispersive Biological Medium Using Continuous Laser Emission

et al. 2010

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A method for simultaneous determination of extinction and scattering coefficients for high scattering biological medium is suggested. This method is based on the use of a refined diffusion model for radiation transport and the detection of intensity of radiation passed through the layer of the medium with two various thicknesses. The results of experiments with model high scattering biological medium are described. Extinction and scattering coefficients of the model medium were determined from experiments. The applicability of the method was proved by comparison with additional experimental data.

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Section: Theorymentioning

confidence: 99%

Simultaneous Determination of Extinction and Scattering Coefficients of Highly Dispersive Biological Medium Using Continuous Laser Emission

et al. 2010

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“…The factor z 0 is introduced into the CDM to adjust it to the boundary condition where B is medium boundary [6,7]. The CDM does not provide a good description of the photon trajectory near the source and medium layer with free photon movement thickness [9].…”

Section: Theorymentioning

confidence: 99%

“…The point monodirectional radiation source function is [9]: (5) where Ω → 0 is radiation propagation direction; δ 2 (...) is sur face delta function [7].…”

Section: Theorymentioning

confidence: 99%

“…The temporal distribution of ultrashort pulse intensi ty in semi infinite medium for Ω → 0 coinciding with the z axis gives [9]: (6) In the EDM the boundary condition does not require additional assumption or z 0 . The EDM provides enhanced accuracy of photon behavior near medium lay ers with free photon movement thickness and laser radia tion propagation through scattering medium.…”

Section: Theorymentioning

confidence: 99%

“…The main disad vantage of CDM is substitution of monodirectional radi ation source (laser) by an isotropic source embedded in the medium. The enhanced diffusion model (EDM) is an alterna tive to the CDM [9]. In this work, numerical simulation of laser radiation propagation through SSM and results of experimental testing of the EDM are discussed.…”

Section: Introductionmentioning

confidence: 99%

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Determination of Optical Characteristics of Highly Scattering Biological Medium Based on Enhanced Diffusion Model of Radiation Transport

Данилов¹,

Селищев²,

Tereshchenko³

2010

Biomed Eng

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IntroductionLaser radiation is used in studies of biological media and tissues [1 5].The problem of laser radiation propagation through strongly scattering media (SSM) is very important. Scattering dominates over absorption during laser radia tion propagation through biological tissues. Therefore, the model of purely absorbing medium is not appropriate in this case, in contrast to the transmission X ray tomo graphy algorithm. Laser radiation interaction with SSM includes both scattering and absorption. The equation of radiation transition (ERT) with regard to scattering describes laser radiation propagation through biological tissues. ERT has no analytical solution, so an approxi mate solution is required. The classical diffusion model (CDM) is presently used [6 8]. In some cases, this model provides an ERT solution, but it has substantial disadvan tages limiting the area of its application. The main disad vantage of CDM is substitution of monodirectional radi ation source (laser) by an isotropic source embedded in the medium. The enhanced diffusion model (EDM) is an alterna tive to the CDM [9]. In this work, numerical simulation of laser radiation propagation through SSM and results of experimental testing of the EDM are discussed. The EDM is superior to the CDM in terms of laser pulse propagation through thin layer SSM and medium with small scattering. The EDM is comparable to the CDM in terms of description of laser pulse propagation through thick layer SSM and medium with strong scattering. TheoryThe ETDM is a particle (energy) balance equation in closed volume and nonstationary form [6,7]:is scattering coefficient; ν is radiation propagation veloc ity module.The numerical and experimental comparison of two models of laser pulse propagation through highly scattering medium, namely a classical diffusion model and an enhanced diffusion model, is given. It is shown that the results obtained for the two models correspond to experimental data. The enhanced diffusion model more pre cisely describes the propagation of laser radiation through scattering layers with thickness about the length of mean path of photons.

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Comparative Study of Diffusion and Axial Models of Radiation Passing through a Biological Scattering Layer Based on the Monte Carlo Method

Tereshchenko

Titenok

2012

Biomed Eng

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The Monte Carlo method (MCM) is used for math ematical simulation of many complicated processes [1]. Propagation of optical radiation through strongly scatter ing medium (SSM) is such a problem [2,3]. In biomedical research, SSM represents biological tissues. Near IR lasers should be used for testing such objects. The near IR range corresponds to a so called transparency window [4].The interaction of IR radiation with biological tis sues is characterized by two processes: absorption and scattering. The probability of scattering is 1 2 orders of magnitude larger than the probability of absorption. SSM is characterized by extinction coefficient and scattering indicatrix. It is difficult to monitor extinction coefficient and scattering indicatrix simultaneously. Thus, scattering coefficient is used instead of scattering indicatrix.Ultrashort laser pulses together with photon count ing are used in experiments. The propagation of pulsed radiation through SSM is described using the transient equation (TE). The TE contains optical parameters of the medium as coefficients for photon flux density. Because TE has no analytical solution, a numerical method with additional assumptions is used. Two models are most fre quently used: the diffusion [5, 6] and axial models [7].Numerical diversity of SSM optical parameters is a serious problem. This diversity is due to difference in the assumptions of different models [8]. Comparative assess ment of the models is required in controlled SSM condi tions. The MCM provides such controlled SSM condi tions.The MCM is based on the trajectory of individual photons with given optical parameters of the SSM. In the case of ultrashort laser pulses, the MCM gives temporal distribution of detected photons. Comparison of various models (MCM and other models of radiation propaga tion in SSM) allows the capacity of each model to be evaluated in terms of temporal distribution of optical parameters in individual samples. TheoryThe photon propagation trajectory through SSM is determined by scattering events. In isotropic SSM the scattering indicatrix μ s (Ω → Ω → ') determines the photon scat tering probability in direction Ω → and solid angle dΩ' near the trajectory Ω → ' during passage of distance dl:Absorption coefficient μ a , scattering coefficient μ s , and extinction coefficient μ = μ a + μ s are macroscopic optical parameters of a SSM. The anisotropy factor g is mean cosine of scattering angle: 211 0006 3398/12/4506 0211 A comparative study of the diffusion and axial models (non stationary axial model, NAM; comprehensive diffu sion model, CDM; and revised diffusion model, RDM) of radiation passing through a biological scattering layer based on the Monte Carlo method is described. NAM gives scattering coefficient close to reduced scattering coef ficient rather than to complete scattering coefficient. It is concluded that RDM is superior to CDM.

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A refined diffusion model of the interaction of laser radiation with biological tissue

Cited by 9 publications

References 5 publications

Simultaneous Determination of Extinction and Scattering Coefficients of Highly Dispersive Biological Medium Using Continuous Laser Emission

Simultaneous Determination of Extinction and Scattering Coefficients of Highly Dispersive Biological Medium Using Continuous Laser Emission

Determination of Optical Characteristics of Highly Scattering Biological Medium Based on Enhanced Diffusion Model of Radiation Transport

Comparative Study of Diffusion and Axial Models of Radiation Passing through a Biological Scattering Layer Based on the Monte Carlo Method

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