The objective of this study was to develop anatomically correct whole body human models of an adult male (34 years old), an adult female (26 years old) and two children (an 11-year-old girl and a six-year-old boy) for the optimized evaluation of electromagnetic exposure. These four models are referred to as the Virtual Family. They are based on high resolution magnetic resonance (MR) images of healthy volunteers. More than 80 different tissue types were distinguished during the segmentation. To improve the accuracy and the effectiveness of the segmentation, a novel semi-automated tool was used to analyze and segment the data. All tissues and organs were reconstructed as three-dimensional (3D) unstructured triangulated surface objects, yielding high precision images of individual features of the body. This greatly enhances the meshing flexibility and the accuracy with respect to thin tissue layers and small organs in comparison with the traditional voxel-based representation of anatomical models. Conformal computational techniques were also applied. The techniques and tools developed in this study can be used to more effectively develop future models and further improve the accuracy of the models for various applications. For research purposes, the four models are provided for free to the scientific community.

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The Virtual Family—development of surface-based anatomical models of two adults and two children for dosimetric simulations

The strong reactive near-field wireless power transmission (WPT) systems induce electric fields in the body tissue of persons in their close vicinity. This may pose potential direct health hazards or indirect risks via interference with medical implants. In this paper, the safety guidelines and the fundamental coupling mechanisms of the human body with the electromagnetic near fields of WPT are reviewed as well as the methodology and the instrumentation for the demonstration of the safety of such systems operating between 100 kHz and 50 MHz. Based on this review, the advantages and shortcomings of state-of-the-art numerical and experimental techniques are discussed and applied to a generic WPT operating at 8 MHz. Finally, current research needs are identified which include: 1) the extension of safety guidelines for coverage of persons with implants; 2) more computationally efficient full-wave solvers; 3) higher quality human models which cover different population groups and include improved models of nerve tissue; 4) experimental dosimetric methods for the WPT frequency range; and 5) product standards to demonstrate safety of specific WPT.

Assessing Human Exposure to Electromagnetic Fields From Wireless Power Transmission Systems

Methods and apparatuses are provided for reducing sweat production via, for example, the removal, disablement, and incapacitation of sweat glands in the epidermis, dermis and subdermal tissue regions of a patient. In one embodiment, a method of treating a patient is provided which involves identifying a patient having a condition of excessive sweating, positioning an energy delivery device proximate to a skin tissue of the patient and delivering energy to sweat glands to halt secretion of sweat. The energy delivery device may include microwave delivery devices, RF delivery devices, and cryogenic therapy devices. Some embodiments may include using a cooling element for avoiding destruction of non-target tissue and/or a suction device to localize treatment at specific portions of the skin fold.

Methods and apparatus for reducing sweat production

The peak spatial specific absorption rate (SAR) assessed with the standardized specific anthropometric mannequin head phantom has been shown to yield a conservative exposure estimate for both adults and children using mobile phones. There are, however, questions remaining concerning the impact of age-dependent dielectric tissue properties and age-dependent proportions of the skull, face and ear on the global and local absorption, in particular in the brain tissues. In this study, we compare the absorption in various parts of the cortex for different magnetic resonance imaging-based head phantoms of adults and children exposed to different models of mobile phones. The results show that the locally induced fields in children can be significantly higher (>3 dB) in subregions of the brain (cortex, hippocampus and hypothalamus) and the eye due to the closer proximity of the phone to these tissues. The increase is even larger for bone marrow (>10 dB) as a result of its significantly high conductivity. Tissues such as the pineal gland show no increase since their distances to the phone are not a function of age. This study, however, confirms previous findings saying that there are no age-dependent changes of the peak spatial SAR when averaged over the entire head.

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Age-dependent tissue-specific exposure of cell phone users

The present invention is directed to systems, apparatus, methods and procedures for the noninvasive treatment of tissue using microwave energy. In one embodiment of the invention a medical device and associated apparatus and procedures are used to treat dermatological conditions using microwave energy.

Systems, apparatus, methods and procedures for the noninvasive treatment of tissue using microwave energy

The dielectric parameters of the tissue simulating liquids to assess the exposure from mobile phones were determined in a previous study considering the tissue distribution of the exposed regions of the head using a planar layered model and the transmission-line method. Currently, the standards for the compliance testing of wireless devices are being extended to more general exposure situations. This paper uses the same methods considering different locations of the body and the respective variations of the tissue structures and dimensions. The analysis of tissue compositions shows a significant increase of 2.2-4.7 dB of the peak spatial specific absorption rate (SAR) in comparison to the values assessed with current standard liquids. This increase is due to standing-wave effects in tissues with low water content. For a certain distance between the antenna and the body (approximately /spl lambda//3 for a /spl lambda//2 dipole), these standing-wave effects dominate the coupling mechanism, leading to a higher average SAR in layered tissue. The observations were validated using finite-difference time-domain simulations of an anatomical high-resolution human model. Nevertheless, a sound conservative exposure assessment applying phantoms filled with homogeneous standardized liquids is possible if a distance and frequency-dependent scaling factor is applied.

The dependence of electromagnetic far-field absorption on body tissue composition in the frequency range from 300 MHz to 6 GHz

ICNIRP 2020 guidelines for limiting exposure to radiofrequency fields replace the radiofrequency part of the ICNIRP 1998 guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields. Besides setting new restrictions that prevent thermal effect they also took over the 100 kHz to 10 MHz part of the ICNIRP 2010 guidelines for limiting exposure to low-frequency electromagnetic fields, which provides restrictions that prevent nerve stimulation effect. The latest guidelines brought many changes to the system of protection against exposure to radiofrequency fields starting with the physical quantities used to express restrictions and continuing with specific restrictions and new exposure metrics employed. For the first time, the case of brief local exposure to intense radiofrequency fields was accounted by ICNIRP for setting new types of exposure restrictions. All these changes led to more detailed and complex guidelines, but their provisions are more difficult to apply in practice. Our paper presents some of the challenges related to the use in practice of the new ICNIRP restrictions for human exposure to radiofrequency fields.

C. Goiceanu

Papers

The dependence of electromagnetic far-field absorption on body tissue composition in the frequency range from 300 MHz to 6 GHz

Some considerations on the challenges related to the use of the new ICNIRP restrictions for human exposure to radiofrequency fields.