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In this paper, a transverse electro-magnetic (TEM) coil operating at 128 MHz in a 3-T magnetic resonance imaging system has been studied in terms of the interaction with patients with or without an implanted pacemaker. The pacemaker has been simulated as a copper box with a catheter constituted by an insulated copper wire with an uncapped tip and it has been placed inside either box or anatomical models of the thorax. Electromagnetic and thermal simulations have been performed by using finite difference time domain codes. The obtained results show that in the absence of the pacemaker, and for a radiated power producing in the box a whole body specific absorption rate (SAR) of 1 W/kg, that is a typical value for MRI examinations, the coil produces in the anatomical models peak temperature values lower than the limits issued by the International Electrotechnical Commission (IEC). In the presence of the pacemaker, temperature increments at the catheter tip in excess of those issued by the IEC standard are obtained when the MRI scanned area involves the pacemaker region. The 3-T coil produces lower SAR and temperature increments with respect to a 64-MHz (1.5-T system) birdcage antenna in patients with implanted pacemaker. [ABSTRACT FROM AUTHOR]

In this paper, a transverse electro-magnetic (TEM) coil operating at 128 MHz in a 3-T magnetic resonance imaging system has been studied in terms of the interaction with patients with or without an implanted pacemaker. The pacemaker has been simulated as a copper box with a catheter constituted by an insulated copper wire with an uncapped tip and it has been placed inside either box or anatomical models of the thorax. Electromagnetic and thermal simulations have been performed by using finite difference time domain codes. The obtained results show that in the absence of the pacemaker, and for a radiated power producing in the box a whole body specific absorption rate (SAR) of 1 W/kg, that is a typical value for MRI examinations, the coil produces in the anatomical models peak temperature values lower than the limits issued by the International Electrotechnical Commission (IEC). In the presence of the pacemaker, temperature increments at the catheter tip in excess of those issued by the IEC standard are obtained when the MRI scanned area involves the pacemaker region. The 3-T coil produces lower SAR and temperature increments with respect to a 64-MHz (1.5-T system) birdcage antenna in patients with implanted pacemaker. [ABSTRACT FROM AUTHOR]

A pilot numerical study is conducted to investigate whether a tumor located in the outermost layers of the brain is able to change power absorption and temperature increase in the head, when exposed to the field radiated by a cellular phone. Results show that absorption into the head tissues different from the tumor is barely affected by its presence. On the other hand, inside the tumor, tumor dielectric properties highly influence electromagnetic power absorption, while temperature increments are mainly affected by tumor thermal properties rather than dielectric properties. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1264–1267, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25158 [ABSTRACT FROM AUTHOR]

Measurement and control of the dielectric parameters of liquids play a major role in industrial quality-control applications. Although several techniques are currently available to this aim, none of them is simultaneously accurate, cost-effective, and reasonably quick. On the other hand, reflectometry has become a very attractive method for monitoring applications, mostly thanks to its accuracy and flexibility. In this paper, a combined method based on time-domain reflectometry (TDR) and frequency-domain (FD) analysis is presented: the aim is to substantially improve the measurement accuracy of the dielectric parameters of liquids. Starting with typical TDR measurements, the associated FD evaluation of the dielectric parameters is considerably enhanced through the combined effect of the following: 1) specific data-processing techniques; 2) the implementation of a calibration procedure; and 3) the final modeling and minimization routine. Furthermore, to definitively assess the proposed combined procedure, results are compared with measurements directly performed in the FD through a vector network analyzer (VNA). The ultimate goal of the work is to pave the way for the adoption of inexpensive and portable TDR devices in practical industrial monitoring applications. [ABSTRACT FROM AUTHOR]

In this paper, the finite-difference time-domain (FDTD), multiple-region/FDTD (MR/FDTD) and ray-tracing/FDTD (RT/FDTD) techniques have been compared with reference to the study of the field scattered by and induced inside an exposed target. The three techniques have been validated on a free-space radiation problem through a comparison with the MoM solution. Compression techniques have been implemented to obtain a reduction of the computational costs associated with MR/FDTD, performing an accurate evaluation of the associated errors. The applicability and accuracy of the three techniques have then been tested studying the exposure of a sphere to a half-wavelength dipole. The obtained results have shown that the best computational performances are achieved employing RT/FDTD. However, this technique gives accurate results only in the radiative far-field of the antenna. MR/FDTD, instead, gives accurate predictions of field distributions for a wide range of distances between the scatterer and the antenna and, thanks to the introduction of compression techniques, requires acceptable computational costs. Pure FDTD, finally, is the most suitable technique, among the three considered, when the scatterer is close to the antenna but its computational costs become prohibitive for large-scale problems. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]