Electromagnetic Energy is converted into heat when tissue is in electromagnetic field. Due to heat energy tissue temperature increases with time. Without the cooling effects of blood flow & heat loss from the tissue surface, the calculated tissue temperature increases & no steady state solution exists. We observe here that this theoretical model, while approximate, demonstrates several important aspects of the electromagnetic heating of tissue which have not been widely appreciated. Blood flow made large effect on the microwave induced heating pattern. The extent of tissue heat can be experimentally controlled by artificial cooling the skin. In this article we are going to focus on microwave heating in deeper level in the tissue.

The electromagnetic radiation is of increasing importance in the study of the biological characteristic variations, when more complex heterogeneous objects like skin with nonflat surface are radiated the additional picks in the surface filed patterns are possible. In order to have deep understanding about the effects of biological cells the theoretical analysis of heat transfer in the tissue is essential, Now, we analize one dimensional heat transfer equation from fundamental equations.

The single-dimensional heat transfer equation in tissue is given by Where, P= the density of tissue in gm/cm3 C= the specific heat of tissue plus blood in cal/gm0C K= the coefficient of tissue heat conduction in cal/cm/s0C VS= the product of flow and heat capacity of blood in cal/cm3/s0C Q(x,t) = the heat input due to the microwave field in cal/cm3/s T(x,t) = the tissue temperature in 0C TO= the temperature of the arterial blood entering the tissue. The term Vs (T' - To) represents the contribution of the blood convection to the dissipation of heat deposited by the microwave field.' This energy input

Mr. D. S. Bhangari1*, Dr. A. C.Bhagali2, Dr. R. V. Kshirsagar3 7

where J is the mechanical equivalent of heat, L is the depth at which the microwave power deposition is reduced by a factor e, u (t) is the unit step function, and r is the fraction of energy transmitted into the tissue (the remaining energy being reflected). For muscle tissue r is near 0.4 at 2.4 GHz. For convenience, we consider the simplified equation The simpler expression does, however, produce reasonable temperature profile. We have also neglected a constant source term in above eq. accounting for metabolic heat production, since we are interested in the tissue temperature increase resulting from microwave radiation. where T= T' - To is the differential temperature increase, and Here we made steady-state solution on the above eqn. In the stedy-state , (dT/dt=0) Where The solution of above eqn is given by The microwave penetration depth L varies in muscle from 1.0 cm to 0.1 cm at 2 GHz and 10 GHz, respectively. The other parameters are approximately: k=0.001 cal/cm/s0C (thermal conductivity of tissue) Pc= 1 cal/cm3 0C Vs=0.0013 cal/cm3/s0C (average blood flow in man) λ = 1.30 cm-2 α= 0.25 cm-1 (for resting nude man in a 30C environment). The Equation suggests that the position of the temperature maximum, The location of the temperature maximum as a function of L and 𝝀 can be found by differentiating Eq. Thus, for the tissue surface maintained at temperature Te. The position is express in terms of x.

These three results are analyzed at I0=100 mw as shown in Fig 1,2 & 3 respectively.

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This result is analyzed at I0=10 mw as shown in Fig 4

Comparative Chart:-

1 10 0.1 100 3 2 8 0.3 100 2.29 3 2.4 1 100 1.76 4 10 0.1 10 1.76 5 2.4 1 10 0.4

Tissue thermal conductivity and blood flow where about equally effective in limiting the temperature rise in the heated area. The increase in tissue surface temperature is 3◦C for 10 GHz with 100 mw/ cm2. The maximum increase in tissue temperature in an animal exposed to the ―safe‖ microwave field of 10 mw/ cm2 is upto 1◦C. K.R.Foster, H.N. Kritikos & H.P.Schwan ―Effect of surface cooling and blood flow on the microwave Heating of tissue‖ IEEE Transaction of medical engineering, Vol.25, No.3,May 1978. Eugene P. Khizhnyak & Marvin C. Ziskin ―Heating patterns in Biological tissue phantoms caused by millimeter wave electromagnetic irradiation‖ IEEE Transaction of biomedical engineering, Vol. 41,No-9,Sep 1994 Maxim Zhadobov, Ronan Sauleau, Yves Le Drean, Stanislav I. Alekseev and Marvin C. Ziskin ―Numerical & experimental millimeter- wave dosimetry for in vitro experiments‖ IEEE Transactions on microwave theory and techniques, Vol.56 No- 12,Dec 2008 Om P. Gandhi and Abbas Riazi ―Absorption of millimeter waves by human beings and its biological implications‖ IEEE Transactions on microwave theory and techniques, Vol.MTT-34, No.2, Feb-1986. Nacer Chahat, Maxim Zhadobov, Laurent Le Coq, Stanislav I.Alekseev and Ronan Sauleau ―Characterization of the interactions between a 60-Ghz antenna and the human body in an off-body scenario‖ IEEE Transactions on Attennas and propagation. Vol 60 No.12, Dec 2012. Igor SmirNov ―Comparative study of the effect of microwave radiation neutralizers on physiological state of human subjects‖. Chin-Yuan Chuang, Jiun-Hung Lin, Shih-Tsang, Wei-Ru Han, Ping- Ting Liu and Shuenn-Tsong Young ―Monitoring and measuring instrument design of RF electromagnetic fields for human physical and mental health ‖Intl. Conf. on Biomedical and Pharmaceutical Engineering 2006 (ICBPE 2006).

Nacer Chahat , Maxim Zhadobov , Ronan Sauleau , Koichi Ito ―A Compact UWB Antenna for On-

Mr. D. S. Bhangari1*, Dr. A. C.Bhagali2, Dr. R. V. Kshirsagar3 7

Priyadarshini college Engineering, Nagpur (PHD Student)