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IEEE Transactions on Microwave Theory and Techniques
Volume 48 Number 11, November 2000

Effects of Frequency, Permittivity,and Voxel Size on Predicted Specific Absorption Rate Values in Biological Tissue During Electromagnetic-Field Exposure

Page 2050.

Abstract:

Current electromagnetic-field (EMF) exposure limits have been based, in part, on the amount of energy absorbed by the whole body. However,it is known that energy is absorbed nonuniformly during EMF exposure. The development and widespread use of sophisticated three-dimensional anatomical models to calculate specific-absorption-rate (SAR) values in biological material has resulted in the need to understand how model parameters affect predicted SAR values. This paper demonstrate the effects of manipulating frequency,permittivity values, and voxel size on SAR values calculated by a finite-difference time-domain program in digital homogenous sphere models and heterogeneous models of rat and man. The predicted SAR values are compared to empirical data from infrared thermography and implanted temperature probes.

References

1. E. L. Hunt and R. D. Phillips, "Absolute physical dosimetry for whole animal experiments", in Joint U.S. Army/Georgia Inst. Technol. Microwave Dosimetry Workshop Dig., Washington, DC, 1972, pp.  74-77. 
2. J. P. Padilla and R. Bixby, "Using Dewar-Flask calorimetry and rectal temperatures to determine the specific absorption rates of small rodents", USAF School Aerospace Med., Brooks AFB, TX, USAFSAM-TR-86-3, 1986.
3. C. H. Durney, H. Massoudi and M. F. Iskander, "Radiofrequency radiation dosimetry handbook", USAF School Aerospace Med., Brooks AFB, TX, USAFSAM-TR-85-73, 1986.
4. A. W. Guy, M. D. Webb and C. C. Sorensen, "Determination of power absorption in man exposed to high frequency electromagnetic fields by thermographic measurements on scale models", IEEE Trans. Biomed. Eng., vol. BME-23, pp.  361-371,  Sept.  1976.
5. T. W. Dawson, K. Caputa and M. A. Stuchly, "Influence of human model resolution on computed currents induced in organs by 60-Hz magnetic fields", Bioelectromagnetics , vol. 18, pp.  478-490, 1997.
6. P. J. Dimbylow, "FDTD calculations of the whole-body averaged SAR in an anatomically realistic voxel model of the human body from 1 MHz to 1 GHz", Phys. Med. Biol., vol. 42, pp.  479-490, 1997.
7. C. M. Furse and O. P. Gandhi, "Calculation of electric fields and currents induced in a millimeter-resolution human model at 60 Hz using the FDTD method", Bioelectromagnetics, vol. 19, pp.  293-299, 1998.
8. G. D. Lapin and C. Allen, "Requirements for accurate anatomical imaging of the rat for electromagnetic modeling", in Proc. 19th Int. IEEE/EMBS Conf., Chicago, IL, 1997, pp.  2480-2483. 
9. P. A. Mason, T. J. Walters, J. W. Fanton, D. N. Erwin, J.-H. Gao, J. W. Roby, J. L. Kane, K. A. Lott, L. E. Lott and R. V. Blystone, "Database created from magnetic resonance images of a Sprague-Dawley rat, rhesus monkey and pigmy goat", Fed. Amer. Soc. Exper. Biol. J, vol. 9, pp.  434-440, 1995.
10. P. A. Mason, J. M. Ziriax, W. D. Hurt, T. J. Walters, K. L. Ryan, D. A. Nelson, K. I. Smith and J. A. D'Andrea, "Recent advancements in dosimetry measurements and modeling,"in Radio Frequency Radiation Dosimetry , B. J. Klauenberg, and D. Miklavcic, Eds. Norwell, MA: Kluwer, 2000, pp.  141-155. 
11. W. D. Hurt, J. M. Ziriax and P. A. Mason, "Variability in EMF permittivity values: Implications for SAR calculations", IEEE Trans. Biomed Eng., vol. 47, pp.  396-401, Mar.  2000.
12. C. Gabriel, "Compilation of the dielectric properties of body tissue at RF and microwave frequencies", USAF School Aerospace Med., Brooks AFB, TX, AL/OE-TR-1996-0037, 1996.
13. C. Gabriel, S. Gabriel and E. Corthout, "The dielectric properties of biological tissues: I. Literature survey", Phys. Med. Biol., vol. 41, pp.  2231-2249,  1996.
14. S. Gabriel, R. W. Lau and C. Gabriel, "The dielectric properties of biological tissues: II. Measurement in the frequency range 10 Hz to 20 GHz", Phys. Med. Biol., vol. 41, pp.  2251-2269, 1996.
15. S. Gabriel, R. W. Lau and C. Gabriel, "The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues", Phys. Med. Biol., vol. 41, pp.  2271-2293, 1996.
16. K. S. Kunz and R. J. Luebbers, The Finite Difference Time Domain Method for Electromagnetics, Boca Raton, FL: CRC Press, 1993.
17. R. W. Olsen, "Temperature distributions during induced deep hypothermia and subsequent circulatory arrest: An experimental and numerical study", Ph.D. dissertation, Grad. School Biomed. Sci., Univ. Texas Health Sci. Center, Dallas, TX, 1985.
18. E. G. Moros and W. F. Pickard, "On the assumption of negligible heat diffusion during the thermal measurement of a nonuniform specific absorption rate", Radiat. Res., vol. 152, pp.  312-320, 1999.
19. K. R. Foster, A. Lozano-Nieto and P. J. Riu, "Heating of tissues by microwaves: Model analysis", Bioelectromagnetics, vol. 19, pp.  420-428, 1998.
20. D. A. Nelson, M. T. Nelson, T. J. Walters and P. A. Mason, "Skin heating of millimeter wave irradiation-Thermal modeling results", IEEE Trans. Microwave Theory Tech., vol. 48, pp.  2111-2120, Nov.  2000.
21. T. J. Walters, P. A. Mason, K. L. Ryan, D. A. Nelson and W. D. Hurt, "A comparison of SAR values determined empirically and by FD-TD modeling,"in Radio Frequency Radiation Dosimetry, Norwell, MA: Kluwer, 2000, pp.  207-216. 
22. T. J. Walters, D. W. Blick, L. R. Johnson, E. R. Adair and K. R. Foster, "Heating and pain sensation produced in human skin by millimeter waves: Comparison to a simple thermal model", Health Phys., vol. 78, pp.  259-267, 2000.