Advanced Fast 3-D Electromagnetic Solver for Microwave Tomography Imaging.

This paper describes a fast-forward electromagnetic solver (FFS) for the image reconstruction algorithm of our microwave tomography system. Our apparatus is a preclinical prototype of a biomedical imaging system, designed for the purpose of early breast cancer detection. It operates in the 3-6-GHz frequency band using a circular array of probe antennas immersed in a matching liquid; it produces image reconstructions of the permittivity and conductivity profiles of the breast under examination. Our reconstruction algorithm solves the electromagnetic (EM) inverse problem and takes into account the real EM properties of the probe antenna array as well as the influence of the patient's body and that of the upper metal screen sheet. This FFS algorithm is much faster than conventional EM simulation solvers. In comparison, in the same PC, the CST solver takes ~45 min, while the FFS takes ~1 s of effective simulation time for the same EM model of a numerical breast phantom.

Animal testing using 3D microwave tomography system for breast cancer detection.

The three dimensional microwave tomography (3D MT) system of the Electronics and Telecommunications Research Institute (ETRI) comprises an antenna array, transmitting receiving module, switch matrix module and a signal processing component. This system also includes a patient interface bed as well as a 3D reconstruction algorithm. Here, we perform a comparative analysis of image reconstruction results using the assembled system and MRI results, which is used to image the breasts of dogs. Microwave imaging reconstruction results (at 1,500 MHz) obtained using the ETRI 3D MT system are presented. The system provides computationally reliable diagnosis results from the reconstructed MT Image.

Microwave tomography analysis system for breast tumor detection.

In the breast-cancer image detection device field, remarkable advancements have been made in the breast cancer detection method using microwave radiation that satisfies the conditions required by Institute of Medicine (IOM). This paper is for embodying the microwave analysis breast tumor detection system that can analyze the permittivity and the conductivity of the breast inside, discover breast tumors, and easily check the various analytical information of the scatter and size of tumors inside breasts. The microwave breast tumor detection system is composed of an antenna array and the RF transceiver for the acquiring of microwave exposure information; the inverse scattering algorithm for searching the permitivity, conductivity and position of a material, and graphic user interface software that includes the visualization and various analyses of acquired data. The embodied system has shown the same-level function of tumor detection even in the type of heterogeneously dense material that is difficult to detect through mammography by experimentations with four kinds of classifications according to the distribution of lactiferous duct inside the breast.

Induction of hair growth by insulin-like growth factor-1 in 1,763 MHz radiofrequency-irradiated hair follicle cells.

Radiofrequency (RF) radiation does not transfer high energy to break the covalent bonds of macromolecules, but these low energy stimuli might be sufficient to induce molecular responses in a specific manner. We monitored the effect of 1,763 MHz RF radiation on cultured human dermal papilla cells (hDPCs) by evaluating changes in the expression of cytokines related to hair growth. The expression of insulin-like growth factor-1 (IGF-1) mRNA in hDPCs was significantly induced upon RF radiation at the specific absorption rate of 10 W/kg, which resulted in increased expression of B-cell chronic lymphocytic leukemia/lymphoma 2 (BCL-2) and cyclin D1 (CCND1) proteins and increased phosphorylation of MAPK1 protein. Exposure to 10 W/kg RF radiation 1 h per day for 7 days significantly enhanced hair shaft elongation in ex vivo hair organ cultures. In RF-exposed follicular matrix keratinocytes in the hair bulb, the expression of Ki-67 was increased, while the signal for terminal deoxynucleotidyl transferase dUTP nick end labeling was reduced. From these results, we suggest that 1,763 MHz RF exposure stimulates hair growth in vitro through the induction of IGF-1 in hDPCs.

Importance of phase unwrapping for the reconstruction of microwave tomographic images.

Microwave image reconstruction is typically based on a regularized least-square minimization of either the complex-valued field difference between recorded and modeled data or the logarithmic transformation of these field differences. Prior work has shown anecdotally that the latter outperforms the former in limited surveys of simulated and experimental phantom results. In this paper, we provide a theoretical explanation of these empirical findings by developing closed form solutions for the field and the inverted electromagnetic property parameters in one dimension which reveal the dependency of the estimated permittivity and conductivity on the absolute (unwrapped) phase of the measured signal at the receivers relative to the source transmission. The analysis predicts the poor performance of complex-valued field minimization as target size and/or frequency and electromagnetic contrast increase. Such poor performance is avoided by logarithmic transformation and preservation of absolute measured signal phase. Two-dimensional experiments based on both synthetic and clinical data are used to confirm these findings. Robustness of the logarithmic transformation to variation in the initial guess of the reconstructed target properties is also shown. The results are generalizable to three dimensions and indicate that the minimization form with logarithmic transformation offers image reconstruction performance characteristics that are much more desirable for medial microwave imaging applications relative to minimizing differences in complex-valued field quantities.