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An efficient method is presented to numerically model anechoic chambers ranging from VHF to microwave frequencies. In this method, an approximate image theory is proposed to improve the accuracy of plane wave assumptions used at lower frequencies. At high frequencies, an efficient image-based ray tracing algorithm is developed which integrates with the approximate image theory seamlessly. Numerical...
One of the critical MRI safety concerns for patients with medical implants is the RF coil induced heating in the vicinity of electrode lead tip. Many works have been carried out to assess such risk for fully implanted leads. However studies on partially implanted, as well as minimally implanted electrodes have not been explored. In addition, effects of statures, weight, ages and many other factors...
In this paper, a quick and efficient approach is proposed to estimate the in-vivo RF induced heating of small medical implants under MRI procedure. The method is based on scaling the in-vivo incident electric fields. Numerical and experimental studies demonstrate the efficiency and accuracy of the proposed method.
One type of nanoring reflectarray metasurface is demonstrated to achieve high-efficiency beam steering in anomalous reflections. Rings with varied inner radius are designed to manipulate the phase front of the incident wave. The efficiency of anomalous reflections achieves more than 80% at the reflection angle of 53° under normal incidence. The light reflects along the surface of structure when the...
This paper presents a novel technique for the efficient evaluation of MRI-induced electric fields in the vicinity of implantable metallic leads. The technique is based on the reciprocity theorem in conjuncture with the Huygens principle that allows one to separate the micro-scale modeling of the metallic lead from the macro-level modeling of human subjects within MRI scanners. In addition to the numerical...
The convergence properties of ASM-FDTD are discussed. It is shown the accuracy of this method is greatly dependant on the choice of sampling rate for calculating the spectral domain integral.
A decomposition and superposition technique is developed for the SAR analysis of a multiple antenna system. Upper and lower bounds for the total SAR can be calculated if the vector electric field from each antenna is available, while a most conservative SAR upper bound can be calculated if only SAR data from each antenna is available. A method for increasing antenna reception while decreasing peak...
An analytical model based on an equivalent impedance circuit for effective permittivity of a composite dielectric as a function of frequency with complex-shaped inclusions is presented. The geometry of the capacitor containing this composite dielectric is discretized into partial impedance elements, the total equivalent impedance is calculated, and the effective permittivity of the composite dielectric...
The article consists of a Powerpoint presentation on integral equation methods. The areas discussed include: integral equation method; method of moments; Maxwell's equation; Green's function; scattering formulation; dipole antenna and matrix equation.
This paper presents a procedure for SAR estimation for multi-transmitting antenna systems is proposed. This procedure can be used towards the development of a compliance test method for MIMO systems and can also be used to reduce SAR measurement uncertainty and the number of measurements needed for multi-transmitter (e.g., MIMO) systems.
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