Domenica A. M. Iero

Thermal and Microwave Constrained Focusing for Patient-Specific Breast Cancer Hyperthermia: A Robustness Assessment

In this paper, we address the problem of microwave hyperthermia. In particular, we first introduce simple tools to understand the relationship between thermal and electromagnetic power focusing. Then, we assess the electromagnetic and thermal performances of a recently proposed strategy to design array applicators. Contrary to common approaches, such a strategy allows a punctual control of power deposition, which is crucial for effective treatment planning. With respect to breast cancer hyperthermia, we analyze the robustness of the strategy against inaccuracies based on the knowledge of the scenario, in a quantitative manner. This analysis allows us to draw useful guidelines on the accuracy of patient-specific information required to guarantee the effectiveness of treatment.

Constrained power focusing of vector fields: an innovative globally optimal strategy

This paper introduces and discusses an innovative approach to focus the electromagnetic power carried by a vector field into a target point, while keeping the field level bounded elsewhere. To overcome the complexity of the underlying NP-hard problem, we introduce a multi-objective optimization framework based on convex programming sub-problems. Notably, such a strategy has the unique capability of achieving the globally optimal solution by means of local search algorithms. A numerical analysis is reported to assess the methods’ performance, including a comparison with previous contributions. The proposed approach is herein presented in the case of 2D vector fields (transverse electric polarization) but it can be easily extended to the general 3D case.

Focusing Time-Harmonic Scalar Fields in Complex Scenarios: A Comparison

This letter deals with the problem of focusing a time-harmonic wave into a target point embedded into a known complex scenario. In particular, we compare the performances of the Time Reversal approach and the Optimal Constrained Focusing technique, which relies on the formulation of the focusing problem in terms of convex programming. Both techniques guarantee a fast and adaptive design of effective applicators, but the second one allows to control the sidelobes of the field, providing a higher selectivity and a more flexible shaping of the field. Some numerical examples relevant to microwave hyperthermia, including a case where the scenario at hand is not exactly known, are given to appraise the importance of this capability.

AN ADAPTIVE METHOD TO FOCUSING IN AN UNKNOWN SCENARIO

The problem of fleld focusing onto a target location in an unknown scenario is considered. In particular, we devise an adaptive procedure in which flrst an image of the unknown region where the target point is located is formed via the linear sampling method (LSM). Then, the LSM result is used also to deflne the excitations coe-cients for the array elements needed to focus the fleld. This novel approach to focusing is described and tested with numerical examples.

On the Role and Choice of Source Polarization in Time-Reversal Focusing of Vector Fields

Time reversal is a well-known method to focus a wave-field into complex unknown/known media. In this letter, we show that when applying time reversal to vector fields, a proper choice of the test sources polarization allows definite advantages as compared to the usual approach of using an a priori fixed polarization. As a matter of fact, by so doing, one can not only focus the target point, but also obtain a field distribution that better accommodates some other requirements (e.g., minimizes sidelobe level). To exploit this possibility, we propose a simple and effective optimization strategy and assess it in case of focusing transverse electric (TE) fields into 2-D scenarios.

Optimization of the Array Element Layout for a Rotating Imaging Interferometer

In this paper, after a brief review on the working principles of synthetic aperture radiometers exploiting interferometry and mechanical rotation of the antenna, analytical expressions are provided which allow to easily compute the receiving performance of the interferometer starting from given locations of its sensors. Then, an innovative and general approach is developed and discussed for the optimal synthesis of the locations of the array sensors in order to fulfill requirements of crucial interest. Moreover, an innovative approach is also developed for the synthesis of the optimal weighting of the different collected signals. Finally, the performances of the developed synthesis approaches are discussed with reference to the GEO Atmospheric Sounder (GAS) array instrument.

Arbitrary field intensity shaping via multi-target optimal constrained power focusing

The capability of controlling the spatial distribution of a field into a given scenario is relevant to many applications as different as hyperthermia treatment planning and wireless network optimization. In this respect, many strategies to focus the field into a target point have been presented, whereas the possibility of arbitrarily shaping a field still remains an open challenge. In this communication, we present an innovative approach to field intensity shaping that unravels the original NP hard problem into several convex programming ones, by means of the proper equality constrained method. The approach is discussed and assessed with a numerical example.

Optimal wave focusing in complex environments

The canonical problem of focusing the intensity of the a field in a given point of space while fulfilling upper bounds elsewhere is addressed and solved for the 3D vector case. The approach takes advantage from results available for the case of scalar fields, and allows the achievement of the globally optimal solution.

Optimizing test source polarization in time reversal electromagnetic focusing

Time Reversal (TR) is a well known simple time/spatial refocusing based on the time invariance of wave equation in lossless media, which is performed in a two phases process (M. Fink, IEEE Trans. Ultrason. Ferroelec. Freq. Contr., 39, 1992, pp. 555–566). The first (sensing) step consists in sensing the field radiated by a point source located in the point where one wants to refocus the field. In the second (back-propagation) step, the signal collected by a set of receivers (Time Reversal Mirror) is time reversed and back-propagated. By virtue of the time invariance of the wave equation which governs the propagation phenomenon, the wave will undergoes the same path focusing in the point where the original point source was located.

Design of biomedical array applicators: An innovative constrained synthesis strategy to focusing vector fields

Spatially focusing a wave field into a target point is an open topic of remarkable interest for the scientific community both from the theoretical and applicative point of view. Designing applicator able to focus a field into a target point is required in many biomedical applications such as hyperthermia, imaging, activation of chemical or biological processes or remotely heat-controlled drugs release. In those cases, the main objective of suitable synthesis procedures is designing a source (typically the excitations of an antenna array) able to induce a selective power deposition in a target point while keeping its value below prescribed levels elsewhere in order to avoid unwanted side power peaks.