Clinical microwave tomography with a lossy coupling bath - insights into challenging reconstruction cases

We have rigorously analyzed the computed amplitude and phase projections as they evolve during the progression of the iterative, log transformed image reconstruction process especially in breast imaging cases. All information concerning the breast composition and presence of benign and malignant tumors are encoded in these projections. In cases where the overall tissue permittivity is less than that for the surrounding background, the phase and amplitude projections are always smoothly varying and well-behaved with the phase components tending less than zero, and the reconstruction process proceeds in a predictable and efficient manner. However, in situations where the tissue properties exceed those of the background, the phase and amplitude projections appear more uneven with the permittivity portion exhibiting mostly positive phase values often with sharp jumps immediately on either side of the principle feature. For these targets, the recovery process is more uneven. In this report we examine the nature of these challenging cases and propose a set of strategies to deal with them systematically while not arbitrarily biasing the final solution.