Microwave Imaging

CHAPTER EIGHT

Hybrid Approaches

8.1 INTRODUCTION

As mentioned previously, the fields of industrial, civil, and military engineering continuously need new and efficient diagnostic methods. The same holds in the areas of geophysical applications, buried-object detection, cultural heritage, demining, and medical diagnostics. However, although several excellent results have been obtained by applying the imaging procedures developed in the previous chapters, the need for new application-oriented methods based on hybrid strategies is widely recognized. The idea is to combine different imaging modalities in order to derive profit from the specific features of the different methods and improve the effectiveness of the inspection.

Hybrid methods could include, for example, two-step procedures in which fast qualitative algorithms (Chapter 5) are combined with quantitative methods (Chapters 6 and 7) in order to first derive the supports of the unknown scatterers and successively retrieve the distributions of their dielectric parameters. Other approaches can combine different quantitative procedures (e.g., deterministic and stochastic algorithms can be combined in order to speed up the convergence of slow and computationally expensive stochastic methods near the global solution). Since efficient “general purpose” imaging techniques cannot be developed, these new combined strategies must be closely related to specific applications and should essentially lead to the implementation of model-driven ...