Inverse methods
Because of the use of remote-sensing and non-local diagnostic systems, the group has an ongoing interest in the application of advanced signal processing techniques and inverse methods. Our current areas of interest include tomography of vector fields and strongly scattering sources for applications in human breast cancer imaging using microwaves. The group has made original contributions in the following areas
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Theoretical determination of reliable information content in 2d and 3d tomography. A paper detailing results in the 3d case is in preparation.
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Established link between statistical properties of scattered laser beam and properties of a weakly fluctuating refractive index field.
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Determined the conditions under which the Doppler broadened emission from an inhomogeneous plasma can be tomographically unfolded for the local velocity distribution function (in preparation)
The development of coherence imaging systems has followed from theoretical investigations of the Doppler tomography problem where it was shown that certain moments of the Doppler broadened spectral lineshape of transition radiation from an excited atomic or ionic state in a plasma relate in a simple way to spatial line integrals of brightness weighted moments of the species velocity distribution function.
Imaging the optical coherence has the nice property that measurements of fringe phase and visibility relate in a simply invertible way to fundamental plasma properties. For a locally drifting isotropic distribution function, and because of the Fourier transform relationship between spectrum and coherence, the drift component separates from the body of the distribution function, being encoded by the interferogram phase (shift theorem), while the shape of the isotropic part is carried by the fringe contrast.
Recently we have established a collaboration with the Group for Electromagnetic, Bio and Plasma Physics at Chalmers University in Sweden in relation to the use of microwaves for human tissue imaging. This work is ARC funded and PhD research projects are available.
In this project we investigate the possibility of using microwaves and microwave tomography to detect inhomogeneities in the dielectric constant of human breast tissue. The work contains both theoretical modelling of the forward and inverse problems and the construction and testing of a prototype system.