Determining the Position and Orientation of In-body Medical Instruments Using Near-Field Magnetic Field Mapping
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The permanent magnet fails due to low power, and static current source requires relatively high power source. The RF field source requires high frequencies to get enough precision, which undergoes high attenuation in the body. At low frequency, when the distance between the source and the receiver array is shorter than the wavelength, the far field assumption fails for localization methods. Therefore, we propose a novel method of mapping the magnetic field vector in the near field region, with which wavelength independent localization is done. We did extensive MATLAB and CST Microwave simulations followed by practical experiments. The proposed method has achieved localization accuracy of less than 1 cm in Y-Z plane, 2 cm in depth (in X-axis) and the maximum orientation error remained 10° in 3-D.
Impact of Electrode Structure on RF-induced Heating for an AIMD Implanted Lead in a 1.5-Tesla MRI System
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It is shown that increasing the size of lead electrode reduces the SAR distribution and temperature rise near the electrode. Our results indicate that a larger electrode size will reduce the magnitudes of the lead transfer function, and subsequently reduces the heating effect near the electrode. Both numerical simulations and experimental measurements were performed to verify the effectiveness of a large electrode in mitigating the RF-induced heating.
Feasibility Study of Hydration Monitoring using Microwaves Part 2: Measurements of Athletes
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Extremity microwave measurement is a promising method for ongoing hydration monitoring, owing to the inherent differences in dielectric properties with varying tissue water content. This paper reports on a feasibility study of textit{in vivo} hydration assessment using microwave measurements in athletes undergoing acute water loss during exercise. We developed and then tested a system for performing reliable microwave property estimation at the forearm. This system was used to measure hydration status in varsity wrestlers before and after a training session. A relationship between estimated permittivity and body weight change due to water loss was found, showing promise for the use of microwaves to assess hydration status. No significant relationship with attenuation was found. A novel method of assessing changes in hydration status is described, which may be of practical use for athletes in guiding fluid replacement during and after exercise.
Feasibility Study of Hydration Monitoring using Microwaves Part 1: A Model of Microwave Property Changes with Dehydration
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However, existing assessment techniques lack the accuracy and/or convenience for ongoing monitoring, motivating the development of novel methods. We propose using low-power microwave measurements (2-12 GHz) at the extremities to monitor human hydration, relying on the strong relationship between dielectric properties of tissues and water content. Electromagnetic simulations of realistic models are used to explore changes in microwave signals transmitted through the forearm to changes in hydration. Tissue properties are adjusted according to expected changes in water content, and average dielectric properties are estimated from signals transmitted through the arm by ultra-wideband antennas placed in contact with the tissues. A causal relationship between weight loss due to water loss and dielectric permittivity is found in human simulation models. Little relationship is found with conductivity. The theoretical groundwork for hydration assessment with microwaves is developed through a model which relates changes in total body water content with changes in microwave properties at the extremities. This model could be useful for monitoring hydration in at-risk populations such as older adults and athletes.
A Survey on Electromagnetic Risk Assessment and Evaluation Mechanism for Future Wireless Communication Systems
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Similarly, the multiplication of future connected devices,e.g. internet of things(IoT)devices, will also contribute to an increase in EMF exposure. This paper provides a detailed survey relating to the potential health hazards linked with EMF exposure and the different metrics that are currently used for evaluating,limiting and mitigating the effects of this type of exposure on the general public. This paper also reviews the possible impacts of new wireless technologies on EMF exposure and proposes some novel research directions for updating the EMF exposure evaluation framework and addressing these impacts in future wireless communication systems. For instance, the impact of mmWave or massive-MIMO/beamforming on EMF exposure has yet to be fully understood and included in the exposure evaluation framework.
Sensitivity Analysis for Ultra-wideband 2-port Impedance Spectroscopy of a Live Cell
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The sensitivity analysis validated our previous empirical observation that the insertion loss of a series-trapped cell and the return loss of a shunt-trapped cell were most sensitive to the cell impedance. Additionally, the membrane resistance and cytoplasm capacitance were most sensitive to low- and high-frequency scattering parameters, respectively. In the future, the analysis can be used to optimize the test setup and protocol for fast, compact and label-free characterization of a cell at the subcelluar level.
