Overcoming Insufficient Microwave Scattering Data in Microwave Tomographic Imaging

Abstract

One of the most challenging problems in microwave tomography is the reconstruction of dielectric properties inside parts of the human body. This is a crucial task for medical applications such as early cancer diagnostics and focused microwave thermotherapy. If not enough antennas are used, the amount of microwave scattering measurement data will be insufficient for satisfactory imaging with the conventional approach. This paper suggests a method for overcoming insufficient microwave scattering data using simultaneous reconstruction of the body shape and its interior dielectric properties, given the restriction that the shape must be regular and smooth. This restriction allows for reduced uncertainty in the reconstructed images. We developed a 2.5D electromagnetic solver and an iterative method for estimating body shape in the process of image reconstruction. This approach provides successful imaging even with insufficient scattering data. In addition, the simultaneous reconstruction leads to improved accuracy in both restorations.INDEX TERMS Microwave imaging, microwave tomography, electromagnetic scattering, inverse problem, shape reconstruction, biomedical imaging.

Application of the Model of Spots for Inverse Problems

“…Therefore, approximate solution methods are used that utilize regularization, filtering, interpolation, and other approaches [ 3 ]. For example, this applies to CT, MRI, and ultrasound, as well as to studies on microwave tomography [ 6 , 7 , 8 , 9 , 10 ].…”

“…This rigorous approach is especially relevant for microwave tomography, where one has to solve the nonlinear inverse problem of electromagnetic scattering. Unfortunately, using simple and approximate reconstruction methods is inadequate here, since microwave scanning of a part of the body is performed in the near-field area of antennas; furthermore, multi-pass scattering effects are significant [ 6 , 7 , 8 , 9 , 10 ]. A big issue is that iterative solutions, especially for electromagnetic scattering, require a long execution time and consume large computer resources [ 7 ].…”

Body Boundary Measurement Using Multiple Line Lasers for a Focused Microwave Thermotherapy System: A Proof-of-Concept Study

“…This environment makes it challenging to measure the shape (boundary line) of the body from the outside. The microwave tomographic imaging technique attempts to obtain the boundary of a body [5,10]. The technique is based on the electromagnetic inverse problem.…”

Application of the Model of Spots for Inverse Problems

“…Therefore, approximate solution methods are used that utilize regularization, filtering, interpolation, and other approaches [3]. For example, this applies to CT, MRI, ultrasound, as well as to studies on microwave tomography [6][7][8][9][10].…”

“…This rigorous approach is especially relevant for microwave tomography, where one has to solve the nonlinear inverse problem of electromagnetic scattering. Unfortunately, using simple and approximate reconstruction methods is inadequate here, since microwave scanning of a part of the body is performed in the near-field area of antennas, and also multi-pass scattering effects are significant [6][7][8][9][10]. A big issue is the fact that iterative solutions, especially for electromagnetic scattering, require a long execution time and consume large computer resources [7].…”