Microwave tomography

• Microwave tomography for non-destructive detection of internaldielectric properties has received increasing interest during the lastdecades. Several application areas are under research, includingapplications in geoscience, biomedical applications, safety andsecurity etc. The goal with this work is development of an microwaveimaging equipment for breast cancer detection. Potentially this isvery beneficial due to the large contrast in dielectric propertiesbetween the tumour and the healthy breast tissue. Within the frames ofthis work a microwave tomography prototype has been constructed. Sincethe image reconstruction is generally requiring computationallyintensive optimisation algorithms comparison with a morecomputationally efficient algorithm, based on a low contrastapproximation of the target, has been made. The results show that thereconstructions are comparable up to 10% contrast. For biomedicalapplications this is not sufficient and thus the iterativeoptimisation algorithms have been selected as the preferred algorithmfor the rest of the work and as a platform for furtherdevelopments. In the work with the experimental prototype somelimitations in the performance of the algorithm have beenidentified. One is the inability to image large and small objectssimultaneously, using a single electromagnetic pulse in themeasurement. This is a problem in breast cancer tomography where theentire breast mass should be imaged together with potentialtumours. The problem has been resolved by performing a reconstructionin several steps using successively increased frequency of theilluminating pulses. Another question that is addressed is whether itis feasible to utilise a priori knowledge about thedielectric properties of the object to improve the accuracy of thereconstructions. A reconstruction algorithm has been developed that iscapable of reconstructing objects with given dielectric values. Theresults show that smaller objects can be resolved with the samefrequency content of the illuminating pulse compared to when thea priori data is not taken into account.

Subject headings

NATURVETENSKAP  -- Biologi -- Biofysik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biophysics (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

inverse algorithms

microwave tomography

image reconstruction

FDTD

inverse Maxwell problem

mammography

Publication and Content Type

dok (subject category)

vet (subject category)