ELLIPTICALLY BENT SLOTTED WAVEGUIDE CONFORMAL FOCUSED ARRAY FOR HYPERTHERMIA TREATMENT OF TUMORS IN CURVED REGION OF HUMAN BODY

In present paper, a novel and effective hyperthermia applicator utilizing an elliptically bent conformal array of longitudinal slots in narrow wall of rectangular waveguide is analyzed by two different approaches, viz., the vector potential method and Fresnel- Kirchhoff scalar diffraction field theory. The agreement between two theories is reasonably very good. This configuration is mainly intended as a specialized and very effective applicator for hyperthermia treatment of tumor within curved portions of human body such as abdomen, neck, chest etc. Each slot of the conformal array is excited by a coaxial line probe. It is proposed that the interior of the waveguide be filled with water to provide a good impedance match with the bio-medium. The contour distribution of specific absorption rate (SAR) in x-z plane, SAR distribution in y-direction and parameters such as penetration depth, power absorption coefficient, effective field size (EFS) due to the conformal array as well as single slot are evaluated and compared at 433 MHz. The results for contour SAR distribution at 433 MHz for elliptically bent conformal array are also compared with those for other array configurations such as circularly bent conformal array and planar array. The effect of change in phase and amplitude excitation of each slot of the array on SAR distribution is also examined. The results demonstrate that slotted waveguide conformal array offers marked improvement in SAR distribution and penetration depth over single slot. It also has better focusing ability as compared with planar array for controlled amplitude and phase excitations of the elements.

[1]  Waveguide slot applicators for microwave heating , 2003, 17th International Conference on Applied Electromagnetics and Communications, 2003. ICECom 2003..

[2]  E. Grant,et al.  Microwaves: Industrial, Scientific, and Medical Applications , 1992 .

[3]  V. M. Pandharipande,et al.  Equivalent Circuit of a Narrow-Wall Waveguide Slot Coupler , 1979 .

[4]  S. Silver.  Microwave antenna theory and design , 1949 .

[5]  Margarethus M Paulides,et al.  Theoretical investigation into the feasibility to deposit RF energy centrally in the head-and-neck region. , 2005, International journal of radiation oncology, biology, physics.

[6]  G. Gaboriaud,et al.  Discussion of Capabilities of Microwave Phased Arrays for Hyperthermia Treatment of Neck Tumors , 1986 .

[7]  Richard L. Magin,et al.  Focused Array Hyperthermia Applicator: Theory and Experiment , 1983, IEEE Transactions on Biomedical Engineering.

[8]  T. Deng.  Optimization of SAR distributions in liver and lung regions irradiated by the H-horn annular phased array hyperthermia system , 1991 .

[9]  P. A. Mason,et al.  Effects of frequency, permittivity, and voxel size on predicted specific absorption rate values in biological tissue during electromagnetic-field exposure , 2000 .

[10]  G. Monich,et al.  Systematic design of antennas for cylindrical 3D phased array hyperthermia applicator , 1999, IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.99CH37010).

[11]  J. Hand,et al.  Absorbed Power Distributions from Coherent Microwave Arrays for Localized Hyperthermia , 1986 .

[12]  M. Krairiksh,et al.  A spherical slot array applicator for medical applications , 1995 .

[13]  K. Foster,et al.  RF-field interactions with biological systems: Electrical properties and biophysical mechanisms , 1980, Proceedings of the IEEE.

[14]  Hao Ling,et al.  Experimental Investigation of a Retro-Focusing Microwave Hyperthermia Applicator: Conjugate-Field Matching Scheme , 1986 .

[15]  Editor-H.P. Westman.  Reference Data for Radio Engineers , 1967 .