Biological Effects of Microwave Radiation

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Presented By:Suruchi KumariECE,NIT Trichy

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

Model

Desired model is made using Comsol 4.4.

It consists of RF model and Heat transfer model.

RF module solves for Electromagnetic fielddistribution and SAR in Human body.

Heat Transfer Model solves for temperature increasebecause of electromagnetic energy absorption. Bothmodel is coupled together through ComsolMultiphysics.

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Assumptions made for RF model

Electromagnetic wave propagation is modeled in twodimensions.

The human body in which electromagnetic wavesinteract proceeds in free space.

The free space is truncated by a scattering boundary

condition.

The model assumes that dielectric properties of eachtissue are uniform and constant.

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Equation used for RF module

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∆ ×1

𝜇𝑟∆ × 𝐸 − 𝑘0

2휀𝑟 𝐸 = 0

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

Equation used for RF module

The Maxwell’s equation demonstrates the electromagnetic field ofmicrowaves penetrated in the human body

∆ ×1

𝜇𝑟∆ × 𝐸 − 𝑘0

2 휀𝑟 − 𝑗𝜎

𝜔𝜀0𝐸 = 0

휀𝑟 = 𝑛2 Where n is refractive index

The perfect-electric-conductor boundary condition along the patchesn × E = 0

Continuous boundary conditions along the interfaces of two differentmediums, n × E1 −E2 = 0

The outer sides of free space are considered as scattering boundaryconditions to define absorbing boundaries

n × ∆ × E – jknk × E × n = −n × E0 × jk × n − k exp −jk. r

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Assumptions made for Heat transfermodel

Human tissue is biomaterial with uniform and constant

thermal properties.

There is no energy exchange throughout the human body

model.

There is no chemical reaction within the tissue.

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Equation used for Heat Transfer

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ρC𝜕T

𝜕t= 𝛻. k𝛻T + ρbCbωb Tb − T + Qmet + Qext

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

Equation used for heat transfer

The boundaries of the human body are considered asan insulated n. k𝛻T = 0

The internal boundaries of human body are assumedas continuous boundaries n. k1𝛻T1 − k2𝛻T2 = 0

For this analysis, the temperature distribution within thehuman body is assumed to be uniform. Initialtemperature of the human body is defined as T t0 = 37°C .The thermoregulation mechanisms and themetabolic heat generation of each tissue is neglected

Qmet=0.

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Electric data of Biological Tissue

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Electrical data value

epsilonr_substrate 5.23

epsilonr0_brain 49.7

sigma0_brain 0.59[S/m]

rho_brain 1.04e3[kg/m^3]

c_blood(Heat capacity of blood) 3639[J/(kg*K)]

dens_liver 1050

rho_blood 1000[kg/m^3]

eps_skin 46.7eps_heart 66dens_skin 1010eps_liver 51.2eps_kidney 66.4cond_skin 0.69cond_heart 0.97cond_liver 0.65cond_kidney 1.10

dens_heart 1050[kg/m^3]

dens_kidney 1050[kg/m^3]

Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore

Skin depth

휀𝑟 = 휀𝑟′ − 𝑗휀𝑟"

휀𝑟′ =

𝜀𝑟0−𝜀𝑟∞

1+𝜔2𝜏2+ 휀𝑟∞ 휀𝑟

” =(𝜀𝑟0−𝜀𝑟∞)𝜔𝜏

1+𝜔2𝜏2

𝛿𝑒 =1

𝜔

𝜇𝜀

21 +

𝜎

𝜔𝜀

21

2

− 1

1

2

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Skin depth

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SAR

Human tissues are lossy mediums with finite electric conductivity forEM waves. They are neither good dielectric materials nor goodconductors, hence when EM waves propagate through the humantissues is absorbed by the human tissues. It is represented by Specificabsorption rate.

The specific absorption rate is given by equation SAR= σ E(r) 2

2ρ

Where E(r) is the electric field intensity at a distance r, σ is the conductivity of human brain tissue, ρ is the density.

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Steps of Work done in COMSOL Geometry

Partitioning of Geometry

Material Assignment to different domains

Added physics.

Addition of RF and Heat transfer module

Addition of all equations and Boundary condition ofthese models.

Meshing

Computation

Analysis of Result.

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Model Structure

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Meshing of Humam body

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Temperature increased in human body

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Electric Field in human body

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SAR in human heart

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SAR in human lever

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SAR in Human Brain

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Conclusion

The biological effects of EM radiation are studied by observing the variations in temperature and SAR on human body due to cell phone radiations.

The study gives solid evidences of the adverse effects the radiations causes in a human body . These results can be taken as a reference for better design of EM emitting devices and also for treatment of illness related to these radiations.

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References[1] André Vander Vorst, Arye Rosen, Youji Kotsuka, RF/MicrowaveInteraction with Biological Tissues. Hoboken, New Jersey: A JohnWiley & Sons, Inc., 2006.

[2] M. Okoniewski, M. A. Stuchly, “A study of the handset antennaand human body interaction,” in A. Rosen and A. Vander Vorst(Eds.), Special Issue on Medical Application and Biological Effectsof RF/Microwaves, IEEE Trans. Microwave Theory Tech.,Vol. 44,No. 10, pp. 1855–1864, Oct. 1996.

[3] S. Michaelson, J. C. Lin, Biological Effects and HealthImplications of Radiofrequency Radiation, New York: Plenum, 1987.

[4] H. G. Booker, Energy in Electromagnetism, Stevenage: P.Peregrinus, 1982.

[5] S. M. Michaelson, J. C. Lin, Biological Effects and HealthImplications of Radiofrequency Radiation, New York: Plenum, 1987.

[6] J.Thuery, Microwaves: Industrial, Scientific and MedicalApplications, Boston,MA:Artech House, 1992.

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References[7] G. Grosse, “Permittivity of a suspension of charged spherical particles in electrolyte solution. II. Influence of the surface conductivity and asymmetry of the electrolyte on the low and high frequency relaxations,” J. Phys. Chem.,Vol. 92, pp. 3905–3910, 1988.[8] G. Grosse, K. R. Foster, “Permittivity of a suspension of charged spherical particles in electrolyte solution,” J. Phys. Chem.,Vol. 91, p. 3073, 1987.[9] K. R. Foster, H. P. Schwan, “Dielectric properties of tissues,” in C. Polk and E. Postow (Eds.), Handbook of Biological Effects of Electromagnetic Fields, Boca Raton, FL: CRC Press, 1996.[10] Girish Kumar, “Cell Tower Radiation,” Mumbai, December 2010.

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THANK YOU

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