30-01-2013, 04:34 PM
Applications of Microwaves in Medicine
1Applications of Microwaves.pdf (Size: 2.89 MB / Downloads: 131)
Introduction
Advantages of technology
– Wide range of frequencies
– Ability to focus the energy
– Variety of simulation tools
– Relatively low cost
– Low if any health risk
Human characteristics
– Differences in tissue
properties (normal/tumor)
Applications
Frequencies 100 MHz -30 GHz.
Diagnostic applications: tumor detection based
on differences in tissue electrical properties.
Regional hyperthermia integrated with MRI
Therapeutic applications based on local heating:
prostate hyperplasia, heart and other tissue
ablation, angioplasty.
Applications not reviewed: MRI (& fMRI),
radiometry, telemetry, motion detection.
Microwave breast tumor detection
Microwave tomography
– Inverse scattering, non-linear relationship
between the acquired data and imagined
pattern, non-unique solution.
– Early solutions - linear approximation, more
recent accurate solutions based on
optimization.
Microwave Tomography
Transmitted waves recorded at a
number of locations; repeated for
various transmitter positions
Measured data compared to model
forward problem: material properties
estimated, transmitted waves at the
measurement points computed
forward problem solution and
measurements compared
estimate of material properties
updated and the process repeated till
convergence
Radar-based detection - basics
Ultra-wideband pulse: modulated Gaussian or frequency
contents optimized (1 - 10 GHz)
Small broadband antennas
Signal processing
– Calibration: removal of the antenna artifacts
– Skin surface identification and artifact removal: reduce dominant
reflection from skin - various algorithms
– Compensation: of frequency dependent propagation effects
– Tumor detection
Basic algorithm: compute time delays from antennas to focal
point, add together corresponding signals, scan focal point
through volume
Additional complex signal processing