2000 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

IEEE Transactions on Microwave Theory and Techniques
Volume 48 Number 1, January 2000

Table of Contents for this issue

Complete paper in PDF format

Analysis of Focusing of Pulsed Baseband Signals Inside a Layered Tissue Medium

Konstantina S. Nikita , Member, IEEE Georgios D. Mitsis and Nikolaos K. Uzunoglu Senior Member, IEEE

Page 30.

Abstract:

The derivation and application of a method designed to investigate the focusing properties of pulsed baseband signals of short pulsewidth ( 1 ns) in biological tissue media are reported. To this end, sources fed from TEM waveguides, concentrically placed at the periphery of a three-layer cylindrical lossy model, are assumed. A Fourier-series-based methodology, appropriate for a useful class of pulse train incident signals, is presented and utilized to study the dynamics of pulse propagation inside the tissue medium. The propagation of each spectral component of the incident field within the tissue medium is analyzed by applying an integral-equation technique and a Fourier-series representation is used in order to obtain the time dependence of the electromagnetic fields produced at any point within tissue due to the pulsed excitation of the array elements. Numerical results are computed and presented at several points in a three-layer geometry, 20 cm in diameter, irradiated by an eight-element waveguide array. Focusing at a specific point of interest within tissue is achieved by properly adjusting the time delay of the signals injected to the individual applicators of the array.

References

  1. J. Chen and O. P. Ghandhi, "Numerical simulation of annular phased arrays of dipoles for hyperthermia of deep seated tumors", IEEE Trans. Biomed. Eng., vol. 39, pp.  209- 216, Mar.  1992.
  2. K. S. Nikita, N. G. Maratos and N. K. Uzunoglu, "Optimal steady-state temperature distribution for a phased array hyperthermia system", IEEE Trans. Biomed. Eng., vol. 40, pp.  1299- 1306, Dec.  1993.
  3. A. Boag, Y. Leviatan and A. Boag, "Analysis and optimization of waveguide multiapplicator hyperthermia systems", IEEE Trans. Biomed. Eng., vol. 40, pp.  946- 952,  Sept.  1993.
  4. K. S. Nikita and N. K. Uzunoglu, "Coupling phenomena in concentric multiapplicator phased array hyperthermia systems", IEEE Trans. Microwave Theory Tech., vol.  44, pp.  65- 74, Jan.  1996.
  5. K. E. Oughstun and J. E. K. Laurens, "Asymptotic description of electromagnetic pulse propagation in a linear causally dispersive medium", Radio Sci. , vol. 26, pp.  245- 258, 1991.
  6. K. E. Oughstun and G. C. Sherman, "Uniform asymptotic description of ultrashort rectangular optical pulse propagation in a linear, causally dispersive medium", Phys. Rev. A: Gen. Phys., vol. 41, pp.  6090- 6113, 1990.
  7. P. Wyns, D. P. Fotty and K. E. Oughstun, "Numerical analysis of the precursor fields in linear dispersive pulse propagation", J. Opt. Soc. Amer. A: Opt. Image Sci. , vol. 6, pp.  1421- 1429, 1989.
  8. J. Bolomey, C. Durix and D. Lesselier, "Time domain integral equation approach for inhomogeneous and dispersive slab problems", IEEE Trans. Antennas Propagat., vol. AP-26, pp.  658- 667, Sept.  1978.
  9. R. Joseph, S. Hagness and A. Taflove, "Direct time integration of Maxwell's equations in linear dispersive media with absorption for scattering and propagation of femtosecond electromagnetic pulses", Opt. Lett., vol. 16, pp.  1412- 1414,  1991.
  10. R. J. Luebbers and F. Hunsberger, "FD-TD for n -th order dispersive media", IEEE Trans. Antennas Propag., vol. 40, pp.  1297- 1301,  Nov.  1992.
  11. P. G. Petropoulos, "The wave hierarchy for propagation in relaxing dielectrics", Wave Motion, vol. 21, pp.  253 - 262, 1995.
  12. R. Albanese, J. Penn and R. Medina, "Short-rise-time microwave pulse propagation through dispersive biological media", J. Opt. Soc. Amer. A: Opt. Image Sci. , vol. 6, pp.  1441- 1446, 1989.
  13. J. G. Blashank and J. Frazen, "Precursor propagation in dispersive media from short-rise-time pulses at oblique incidence", J. Opt. Soc. Amer. A: Opt. Image Sci., vol. 12, pp.  1501- 1512, 1995.
  14. W. C. Chew, Waves and Fields in Inhomogeneous Media, New York : Van Nostrand , 1990.
  15. P. G. Petropoulos, "Stability and phase error analysis of FD-TD in dispersive dielectrics", IEEE Trans. Antennas Propagat., vol.  42, pp.  62- 69, Jan.  1994.
  16. K. S. Nikita and N. K. Uzunoglu, "Analysis of focusing of pulse modulated microwave signals inside a tissue medium", IEEE Trans. Microwave Theory Tech., vol. 44, pp.  1788- 1798, Oct.  1996.
  17. J. Benford and J. Swengle, High Power Microwaves, Norwood , MA : Artech House, 1992.
  18. D. S. Jones, Theory of Electromagnetism, New York : Pergamon, 1964.
  19. H. P. Schwan and K. R. Foster, "RF field interactions with biological systems: Electrical properties and biophysical mechanism", Proc. IEEE, vol. 68, pp.  104- 113, Jan.  1980.
  20. C. Gabriel, S. Gabriel and E. Corthout, "The dielectric properties of biological tissues", Med. Phys., vol. 41, pp.  2231- 2293, 1996.
  21. R. V. Churchill, Fourier Series and Boundary Value Problems, New York : McGraw-Hill , 1941.