Post on 18-Dec-2015
Microwave Imaging for Microwave Imaging for Detecting Breast CancerDetecting Breast Cancer
Amir GolnabiENGS 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
0 jj
0f 2
Tissue Dielectric Properties: Range 1Hz – 30GHz
•3 Dispersion regions: α, β, and γ
•Alpha Dispersion (0.1-100kHz):–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: 50-900 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):
222
2
22
19
nnnmnm
nnnm
n
m
P
P
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
BC
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: 500-2500 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
References:•Larsen, Lawrence, and John Jacobi. Medical Applications of Microwave Imaging. New York: IEEE Press, 1985.
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•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. 4373-4380, 1968
•H.F. Cook, “The dielectric behavior of some types of human tissue at microwave frequencies,” Br. J. Appl. Phys., Vol 2, pp. 295-296, Oct. 1951.
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IEEE Trans. Microwave Theory Tech., Vol. MTT 28, No. 4, pp. 414-423, 1980.
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Physics, vol. 21, 1994, pp. 547-550.
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Theory Tech., vol. 48, pp. 1841-1853, Nov.2000.
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5:453472S
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35. No.4.257-263
Acknowledgements:
Prof. Paul Meaney, Prof. Keith Paulsen, MIS group at Thayer School of Engineering