Microwave Imaging for Detecting Breast Cancer Amir Golnabi ENGS 166 Spring 2008

Outline: Electrical Properties Tissue Dielectric Properties Dielectric Property Measurement Measured Tissue Dielectric Properties Normal Tissue vs. Malignant Tissue Microwave Tomography Breast Microwave Imaging at Dartmouth College Acknowledgements and References

Basic Concepts of Electrical Properties: The interaction of an electromagnetic (EM) field with a biological system Electrical properties: –Conductivity: σ the conductance of a unit volume of matter –Permittivity: ε the capacitance of a unit volume of matter Complex Permittivity: – Loss Factor – permittivity of free space (=8.85 x 10^(-12) F/m) – angular frequency and f represents the frequency of the EM field in hertz

Tissue Dielectric Properties: Range 1Hz – 30GHz 3 Dispersion regions: α, β, and γ Alpha Dispersion ( kHz): –Frequency dependence of the outer cell membrane Beta Dispersion (1-20MHz): –Insulating structure –Cellular membrane enclose bound water –EM frequency ↑ → Cellular membranes are short-circuited → Bound water insulating effects ↓ → Conduction through cell membrane ↑ → σ ↑ Gamma Dispersion (about 20GHz) –Dipolar relaxation of water in the tissue

Dielectric Properties of Different tissues: Blood, Muscle, and Fatty tissue in Microwave Frequencies Range: Water and electrolyte content Tissues: –High water content: Muscle, Blood, Brain, and Internal organs –Low water content: Fat, Bone, Lung, and Outer layer of skin Low water content Low Permittivity

Dielectric Property Measurement: Measuring the effects of the intervention of tissue with an electromagnetic field at specific frequency: –Open-ended coaxial cable Network Analyzer: Measures the relative amplitude and phase difference between the reference and reflected signal channels. Computer Algorithm: Computes the dielectric properties.

Joines et.al. 1994, In-vitro: Normal vs. Malignant Tissues –Colon, kidney, liver, lung, and breast –Frequency range: MHz –ratio of the power absorbed in the malignant tissue (Pm) to that absorbed in the normal tissue (Pn) n: Normal m: Malignant Measured Dielectric Properties (results):

Higher water content in malignant tissue Higher dielectric properties

Meaney et.al. 2000, In-vivo: clinical prototype of a microwave tomographic system for breast imaging –contrast between normal and malignant breast tissue close to 2:1 Sha et.al. 2002: Diagnostic value of dielectric properties of normal and malignant breast tissue at a wide range of frequencies –The low conductivity values of the normal breast tissue enable penetration of microwave frequencies up to the low GHz range. –At 100 MHz – 1 GHz, dielectric properties can significantly help classify normal and malignant breast tissues. Measured Dielectric Properties (results):

Basic idea Microwave Imaging at Dartmouth College: Microwave Tomography: A B C D E (A) Microwave illumination tank (B) Antenna motion actuator; (C) the coupling medium reservoir; (D) Patient examination table (E) Electronics cart.

16 monopole antennas Frequency range: MHz 7 vertical positions 1 antenna transmits and other 15 antennas receive the signal 2D Image reconstruction Microwave Imaging at Dartmouth College:  1,  1 2,22,2

Reconstructed Images: patient 1914 left Breast Microwave Imaging at Dartmouth College: (cont.) rr  rr 

Reconstructed Images: patient 1914 left Breast Microwave Imaging at Dartmouth College: (cont.) rr  rr 

References: Larsen, Lawrence, and John Jacobi. Medical Applications of Microwave Imaging. New York: IEEE Press, J. R. Reitz and F. J. Milford. Functions of electromagnetic theory. Addison Wesley Publishing Company, 1967 Von Hippel, A. R. Dielectric Materials and Applications. M.I.T. Press, 1954 Schwan, H. P. Electrical properties of tissue and cell suspensions. Adv, Biol. Med. Phys. Vol. 5 E.H. Grand, S.E. Keefe, and S. Takashima, “The dielectric behavior of aqueous solutions of bovine serum albumin from radiowave to microwave frequencies,” J.Phys. Chem., Vol. 72, pp , 1968 H.F. Cook, “The dielectric behavior of some types of human tissue at microwave frequencies,” Br. J. Appl. Phys., Vol 2, pp , Oct J. E. Roberts and H. F. Cook, “Microwave in medical and biological research,” Br. J. Appl. Phys., Vol. 3, pp , Feb C. C. Johnson and A.W. Guy, “Nonionizing electromagnetic wave effects in biological materials and systems,” Proc. IEEE, Vol. 60, pp , June Fear, Elise, Paul Meaney, and Maria A. Stuchly. "Microwaves for breast cancer detection?". IEEE POTENTIALS 2003: E. C. Burdette, F. L. Cain, and J. Seals, “In-vivo probe measurement technique for determining dielectric properties at VHF through microwave frequencies,” IEEE Trans. Microwave Theory Tech., Vol. MTT 28, No. 4, pp , W. T. Joines, Y. Z. Dhenxing, and R.L. Jirtle. “The measured electrical properties of normal and malignant human tissues from 50 to 900 MHz,” Medical Physics, vol. 21, 1994, pp P.M. Meaney, M.W. Fanning, D. Li, S.P. Poplack, and K.D Paulsen,“A clinical prototype for active microwave imaging of the breast,” IEEE Trans. Microwave Theory Tech., vol. 48, pp , Nov L. Sha, E. R. Ward, and B. Story, “A Review of Dielectric Properties of Normal and Malignant Breast Tissue”, IEEE SoutheastCon 2002 pp R.Smith,K.R Foster and J L.Wolf. "Dielectric properties of VX-2 carcinoma vs. normal liver Tissues”, IEEE trans Biomed. Eng.. BME-33,522,1986 H. Fricke and S. Morse, “The Electric Capacity of Tumor of the Breast", J. CancerRes., vol. 16, pp , R.Pethig, “Dielectric Properties of Biological Materials: Biophysical and Medical applications", EEE trans. un Electrical insulation Oct.1984;vol El-I9 No 5:453472S W. T. Joines, R. L. Jirtle, M. D. Rafal, D. J. Schaefer, "Microwave Power Absorption Differences Between Normal and Malignant Tissue", Int. J. Radiation Oncology Biol. Phys., voI.6, pp , 1980 A J. Suruwiec. S S. Stuchly. J R. Barr. A. Swarup. "Dielectric Properties of Breast Carcinoma and the Surrounding tissues". IEEE Trans. Biomd. Eng. 1988; VoI 35. No Acknowledgements: Prof. Paul Meaney, Prof. Keith Paulsen, MIS group at Thayer School of Engineering