A MICROWAVE IMAGING APPROACH BASED ON AMPLITUDE-ONLY DATA FOR THE RECONSTRUCTIN OF THE ELECTROMAGNETIC FIELD INDUCED IN BIOLOGICAL PHANTOMS

摘要

In this paper, a microwave imaging technique for the reconstructin of the electromagnetic field distribution inside exposed biological bodies from amplitude-only data is presented. The scattering problem, formulated in terms of integral equations, is recast into an optimization problem after defining a suitable cost function which is proportional to the difference between reconstructed and measured amplitudes of the scattered and of the incident electric fields in the near-field region. The field solution is obtained by minimizing the cost function by means of an hybrid simulated annealing-conjugate gradient based procedure, which, in principle, ensures the convergence to the global minimum, preventing the solution from being trapped in local minima. Moreover, the proposed approach prevents the problems due to inaccuracies in near-field phase measurements. The effectiveness of the microwave imaging approach is assessed by means of some numerical expamples (with synthetic input data) concerning a realistic cross-section of a biological phantom exposed to a TM electromagnetic illumination. The presence of noise on synthetic data is also considered and the dependence of the reconstruction accuracy on the signal-to-noise ratio investigated. Finally, in order to give some indications to further improve the prediction capability of the proposed approach, some preliminary guidelines are pointed out.