A novel, potential and efficient microwave direct contact hyperthermia applicator referred to as water-loaded box-horn for therapeutic heating of bio-medium is designed and developed at 915 and 2450MHz. Also, theoretical expressions for fields in bio-medium as produced by a direct contact box-horn applicator have been derived using plane wave spectral technique. The box-horn is a special type of dual mode horn antenna which supports TE10- and TE30- modes. Therefore, the aperture field distribution over the H-plane of the box-horn is nearly uniform which prevents steep temperature gradients in the heating medium. Water-loading of the box-horn provides a better impedance match to the bio-medium and hence better coupling of microwave energy into bio-medium. Also, it reduces the size of box-horn applicator considerably. The SAR distributions in bio-medium in direct contact with water-loaded box-horn have been computed theoretically with the developed analytical model and measured experimentally with the help of Agilent/HP vector network analyzer (8714 ET) at 915 and 2450MHz. The theoretical and experimental results for SAR are in nearly in agreement with each other. It is investigated that higher penetration depth, lower power absorption coefficient and higher half-power width/depth or lower resolution in heating medium are found for box-horn designed at 915MHz in comparison to those for box-horn designed at 2450MHz.
1. Guy, A. W., J. F. Lehmann, J. B. Stonebridge, and C. C. Sorenson, "Development of a 915-MHz direct-contact applicator for therapeutic heating of tissues," IEEE Trans. Microwave Theory Tech., Vol. MTT-26, No. 8, 550-556, 1978. doi:10.1109/TMTT.1978.1129437
2. Uzunoglu, N. K., E. A. Angelikas, and P. A. Cosmidis, "A 432MHz local hyperthermia system using an indirectly cooled, water-loaded waveguide applicator," IEEE Trans. Microwave Theory Tech., Vol. MTT-35, 106-111, 1987. doi:10.1109/TMTT.1987.1133611
3. Verba, Jr., J., C. Franconi, F. Montecchia, and I. Vannucci, "Evanescent-mode applicators (EMA) for superficial and subcutaneous hyperthermia," IEEE Trans. Microwave Theory Tech., Vol. MTT-40, 397-407, 1993.
4. Stuchly, M. A., S. S. Stuchly, and G. Kantor, "Diathermy applicators with circular aperture and corrugated flange," IEEE Trans. Microwave Theory Tech., Vol. MTT-28, No. 3, 267-271, 1980. doi:10.1109/TMTT.1980.1130054
5. Lin, J. C., G. Kantor, and A. Ghods, "A class of new microwave therapeutic applicators," Radio Sci., Vol. 17, No. 10, 1982.
6. Samaras, T., P. J. M. Rietveld, and G. C. V. Rhoon, "Effectiveness of FDTD in predicting SAR distributions from the Lucite cone applicator," IEEE Trans. Microwave Theory Tech., Vol. MTT-48, No. 1, 2059-2063, 2000.
7. Nikawa, Y., H. Wantanabe, M. Kikuchi, and S. Mori, "A direct-contact microwave lens applicator with a microcomputercontrolled heating system for local hyperthermia," IEEE Trans. Microwave Theory Tech., Vol. MTT-34, No. 5, 626-630, 1986. doi:10.1109/TMTT.1986.1133402
8. Sherar, M. D., F. F. Liu, D. J. Newcombe, B. Cooper, W. Levin, W. B. Taylor, and J. W. Hunt, "Beam shaping for microwave waveguide hyperthermia applicators," Int. J. Radiat. Oncol. Biol. Phys. (UK), Vol. 25, 849-857, 1993.
9. Alexander, P. H. and J. Liu, "Field analysis of dielectricloaded lens applicator for microwave hyperthermia," IEEE Trans. Microwave Theory Tech., Vol. MTT-41, No. 5, 792-796, 1993. doi:10.1109/22.234512
10. Compton, Jr., R. T., The admittance of aperture antenna radiating into lossy media, Rep. 1691-5, Antenna Laboratory Ohio State University, Research Foundation, Columbus, Ohio, 1964.
11. Harrington, R. F., Time-harmonic Electromagnetic Field, 123-135, McGraw-Hill Book Company, New York, 1961.
12. Silver, S. (ed.), Microwave Antenna Theory and Design, Vol. 12, 123-135, MIT Radiation laboratory series, Vol. 12, 123-135, McGraw-Hill Book Company, New York, 1949.
13. International Telephone and Telegraph Company, Reference data for radio engineers, Reference data for radio engineers, 5/e, H. W. Sams & Company, Indianpolis, IN, 1968.
14. Stuchly, M. A. and S. S. Stuchly, "Dielectric properties of biological substances-tabulated," J. Microwave Power, Vol. 15, No. 1, 19-26, 1980.
15. Manson, P. A., W. D. Hurt, T. J. D'Andra, P. GajË˜sek, K. L. Ryan, D. A. Nelson, K. I. Smith, and J. M. Ziriax, "Effect of frequency, permittivity, and voxel size on predicted specific absorption rate values in biological tissue during electromagnetic field exposure," IEEE Trans. Microwave Theory Tech., Vol. MTT-48, No. 1, 2050-2058, 2000.
16. Loane, J., H. Ling, B. F. Wang, and S. W. Lee, "Experimental investigation of a retro-focused microwave hyperthermia applicator: Conjugate-field matching scheme," IEEE Trans. Microwave Theory Tech., Vol. MTT-34, No. 5, 490-494, 1986. doi:10.1109/TMTT.1986.1133381
17. Gee, W., S.-W. Lee, N. K. Bong, C. A. Cain, R. Mittra, and R. L. Magin, "Focused array hyperthermia applicator: Theory and experiment," IEEE Trans. Biomed. Eng., Vol. BME-31, No. 1, 38-46, 1984.