Reflection and penetration depth of millimeter waves in murine skin

Fentanyl overdose: Temporal effects and prognostic factors in SKH1 mice

Fentanyl exposure and overdose are growing concerns in public health and occupational safety. This study aimed to establish parameters of fentanyl lethality in SKH1 mice for future overdose research. Lethality was determined using the up-down procedure, with subjects monitored post-administration using pulse oximetry (5 min) and then whole-body plethysmography (40 min). Following the determination of subcutaneous dose-response, [18F]Fluorodeoxyglucose positron emission tomography (18 F-FDG PET) was performed after LD10 fentanyl at 40 min, 6 h, 24 h or 7 days post-dose. LD10 and LD50 were observed to be 110 and 135 mg/kg, respectively, and consistent with four-parameter logistic fit values of 111.2 and 134.6 mg/kg (r2  = 0.9996). Overdose (LD10 or greater) yielded three distinct cardiovascular groups: survival, non-survival with blood oxygen saturation (SpO2) minimum ≥37% and non-survival with SpO2 <37%. Breaths per minute, minute volume and inspiratory quotient were significantly different between surviving and non-surviving animals for up to 40 min post-injection. 18 F-FDG PET revealed decreased glucose uptake in the heart, lungs and brain for up to 24 h. These findings provide critical insights into fentanyl lethality in SKH1 mice, including non-invasive respiratory effects and organ-specific impacts that are invaluable for future translational studies investigating the temporal effects of fentanyl overdose.

Measurement and image-based estimation of dielectric properties of biological tissues —past, present, and future—

The dielectric properties of biological tissues are fundamental pararmeters that are essential for electromagnetic modeling of the human body. The primary database of dielectric properties compiled in 1996 on the basis of dielectric measurements at frequencies from 10 Hz to 20 GHz has attracted considerable attention in the research field of human protection from non-ionizing radiation. This review summarizes findings on the dielectric properties of biological tissues at frequencies up to 1 THz since the database was developed. Although the 1996 database covered general (normal) tissues, this review also covers malignant tissues that are of interest in the research field of medical applications. An intercomparison of dielectric properties based on reported data is presented for several tissue types. Dielectric properties derived from image-based estimation techniques developed as a result of recent advances in dielectric measurement are also included. Finally, research essential for future advances in human body modeling is discussed.

Adverse health effects of 5G mobile networking technology under real-life conditions

This article identifies adverse effects of non-ionizing non-visible radiation (hereafter called wireless radiation) reported in the premier biomedical literature. It emphasizes that most of the laboratory experiments conducted to date are not designed to identify the more severe adverse effects reflective of the real-life operating environment in which wireless radiation systems operate. Many experiments do not include pulsing and modulation of the carrier signal. The vast majority do not account for synergistic adverse effects of other toxic stimuli (such as chemical and biological) acting in concert with the wireless radiation. This article also presents evidence that the nascent 5G mobile networking technology will affect not only the skin and eyes, as commonly believed, but will have adverse systemic effects as well.

Exposure Assessment in Millimeter-Wave Reverberation Chamber Using Murine Phantoms

This study deals with the design and calibration of the first mode-stirred reverberation chamber (RC) in the 60-GHz-band adapted for in vivo bioelectromagnetic studies. In addition to the interface for electromagnetic and thermal dosimetry, the interfaces for lighting and ventilation were integrated into the RC walls while preserving acceptable shielding. The RC with mechanical and electronic steering capabilities is characterized in the 55-65 GHz range. To this end, murine skin-equivalent phantoms of realistic shape were designed and fabricated. Their complex permittivity is within ±12% of the target value of murine skin (6.19-j5.81 at 60 GHz). The quality factor of the RC loaded with an animal cage, bedding litter, and five murine phantoms was found to be 1.2 × 10⁴ . The losses inside the RC were analyzed, and it was demonstrated that the main sources of the power dissipation were the phantoms and mice cage. The input power required to reach the average incident power density of 1 and 5 mW/cm² was found to be 0.23 and 1.14 W, respectively. Surface heating of the mice models was measured in the infrared (IR) range using a specifically designed interface, transparent at IR and opaque at millimeter waves (mmW). Experimental results were compared with an analytical solution of the heat transfer equation and to full-wave computations. Analytical and numerical results were in very good agreement with measurements (the relative deviation after 90 min of exposure was within 4.2%). Finally, a parametric study was performed to assess the impact of the thermophysical parameters on the resulting heating. Bioelectromagnetics. 2020;41:121-135. © 2020 Bioelectromagnetics Society.

5G Wireless Communication and Health Effects-A Pragmatic Review Based on Available Studies Regarding 6 to 100 GHz

The introduction of the fifth generation (5G) of wireless communication will increase the number of high-frequency-powered base stations and other devices. The question is if such higher frequencies (in this review, 6-100 GHz, millimeter waves, MMW) can have a health impact. This review analyzed 94 relevant publications performing in vivo or in vitro investigations. Each study was characterized for: study type (in vivo, in vitro), biological material (species, cell type, etc.), biological endpoint, exposure (frequency, exposure duration, power density), results, and certain quality criteria. Eighty percent of the in vivo studies showed responses to exposure, while 58% of the in vitro studies demonstrated effects. The responses affected all biological endpoints studied. There was no consistent relationship between power density, exposure duration, or frequency, and exposure effects. The available studies do not provide adequate and sufficient information for a meaningful safety assessment, or for the question about non-thermal effects. There is a need for research regarding local heat developments on small surfaces, e.g., skin or the eye, and on any environmental impact. Our quality analysis shows that for future studies to be useful for safety assessment, design and implementation need to be significantly improved.

Emerging medical applications based on non-ionizing electromagnetic fields from 0 Hz to 10 THz

The potential for using non-ionizing electromagnetic fields (EMF; at frequencies from 0 Hz up to the THz range) for medical purposes has been of interest since many decades. A number of established and familiar methods are in use all over the world. This review, however, provides an overview of applications that already play some clinical role or are in earlier stages of development. The covered methods include modalities used for bone healing, cancer treatment, neurological conditions, and diathermy. In addition, certain other potential clinical areas are touched upon. Most of the reviewed technologies deal with therapy, whereas just a few diagnostic approaches are mentioned. None of the discussed methods are having such a strong impact in their field of use that they would be expected to replace conventional methods. Partly this is due to a knowledge base that lacks mechanistic explanations for EMF effects at low-intensity levels, which often are used in the applications. Thus, the possible optimal use of EMF approaches is restricted. Other reasons for the limited impact include a scarcity of well-performed randomized clinical trials that convincingly show the efficacy of the methods and that standardized user protocols are mostly lacking. Presently, it seems that some EMF-based methods can have a niche role in treatment and diagnostics of certain conditions, mostly as a complement to or in combination with other, more established, methods. Further development and a stronger impact of these technologies need a better understanding of the interaction mechanisms between EMF and biological systems at lower intensity levels. The importance of the different physical parameters of the EMF exposure needs also further investigations.

Impact of 60-GHz millimeter waves on stress and pain-related protein expression in differentiating neuron-like cells

Millimeter waves (MMW) will be increasingly used for future wireless telecommunications. Previous studies on skin keratinocytes showed that MMW could impact the mRNA expression of Transient Receptor Potential cation channel subfamily Vanilloid, member 2 (TRPV2). Here, we investigated the effect of MMW exposure on this marker, as well as on other membrane receptors such as Transient Receptor Potential cation channel subfamily Vanilloid, member 1 (TRPV1) and purinergic receptor P2X, ligand-gated ion channel, 3 (P2 × 3). We exposed the Neuroscreen-1 cell line (a PC12 subclone), in order to evaluate if acute MMW exposures could impact expression of these membrane receptors at the protein level. Proteotoxic stress-related chaperone protein Heat Shock Protein 70 (HSP70) expression level was also assessed. We used an original high-content screening approach, based on fluorescence microscopy, to allow cell-by-cell analysis and to detect any cell sub-population responding to exposure. Immunocytochemistry was done after 24 h MMW exposure of cells at 60.4 GHz, with an incident power density of 10 mW/cm(2) . Our results showed no impact of MMW exposure on protein expressions of HSP70, TRPV1, TRPV2, and P2 × 3. Moreover, no specific cell sub-populations were found to express one of the studied markers at a different level, compared to the rest of the cell populations. However, a slight insignificant increase in HSP70 expression and an increase in protein expression variability within cell population were observed in exposed cells, but controls showed that this was related to thermal effect. Bioelectromagnetics. 37:444-454, 2016. © 2016 Wiley Periodicals, Inc.

Experimental Procedure for Determination of the Dielectric Properties of Biological Samples in the 2-50 GHz Range

The objective of this paper was to test and evaluate an experimental procedure for providing data on the complex permittivity of different cell lines in the 2-50-GHz range at room temperature, for the purpose of future dosimetric studies. The complex permittivity measurements were performed on cells suspended in culture medium using an open-ended coaxial probe. Maxwell's mixture equation then allows the calculation of the permittivity profiles of the cells from the difference in permittivity between the cell suspensions and pure culture medium. The open-ended coaxial probe turned out to be very sensitive to disturbances affecting the measurements, resulting in poor precision. Permittivity differences were not large in relation to the spread of the measurements and repeated measurements were performed to improve statistics. The 95% confidence intervals were computed for the arithmetic means of the measured permittivity differences in order to test the statistical significance. The results showed that for bone cells at the lowest tested concentration (33 500/ml), there were significance in the real part of the permittivity at frequencies above 30 GHz, and no significance in the imaginary part. For the second lowest concentration (67 000/ml) there was no significance at all. For a medium concentration of bone cells (135 000/ml) there was no significance in the real part, but there was significance in the imaginary part at frequencies below about 25 GHz. The cell suspension with a concentration of 1 350 000/ml had significance in the real part for both high (above 30 GHz) and low (below 15 GHz) frequencies. The imaginary part showed significance for frequencies below 25 GHz. In the case of an osteosarcoma cell line with a concentration of 2 700 000/ml, only the imaginary part showed significance, and only for frequencies below 15 GHz. For muscle cells at a concentration of 743 450/ml, there was only significance in the imaginary part for frequencies below 5 GHz. The experimental data indicated that the complex permittivity of the culture medium may be used for modeling of cell suspensions.

An anisotropic, hyperelastic model for skin: experimental measurements, finite element modelling and identification of parameters for human and murine skin

The mechanical characteristics of skin are extremely complex and have not been satisfactorily simulated by conventional engineering models. The ability to predict human skin behaviour and to evaluate changes in the mechanical properties of the tissue would inform engineering design and would prove valuable in a diversity of disciplines, for example the pharmaceutical and cosmetic industries, which currently rely upon experiments performed in animal models. The aim of this study was to develop a predictive anisotropic, hyperelastic constitutive model of human skin and to validate this model using laboratory data. As a corollary, the mechanical characteristics of human and murine skin have been compared. A novel experimental design, using tensile tests on circular skin specimens, and an optimisation procedure were adopted for laboratory experiments to identify the material parameters of the tissue. Uniaxial tensile tests were performed along three load axes on excised murine and human skin samples, using a single set of material parameters for each skin sample. A finite element model was developed using the transversely isotropic, hyperelastic constitutive model of Weiss et al. (1996) and was embedded within a Veronda-Westmann isotropic material matrix, using three fibre families to create anisotropic behaviour. The model was able to represent the nonlinear, anisotropic behaviour of the skin well. Additionally, examination of the optimal material coefficients and the experimental data permitted quantification of the mechanical differences between human and murine skin. Differences between the skin types, most notably the extension of the skin at low load, have highlighted some of the limitations of murine skin as a biomechanical model of the human tissue. The development of accurate, predictive computational models of human tissue, such as skin, to reduce, refine or replace animal models and to inform developments in the medical, engineering and cosmetic fields, is a significant challenge but is highly desirable. Concurrent advances in computer technology and our understanding of human physiology must be utilised to produce more accurate and accessible predictive models, such as the finite element model described in this study.

Millimeter waves: acoustic and electromagnetic

This article is the presentation I gave at the D'Arsonval Award Ceremony on June 14, 2011 at the Bioelectromagnetics Society Annual Meeting in Halifax, Nova Scotia. It summarizes my research activities in acoustic and electromagnetic millimeter waves over the past 47 years. My earliest research involved acoustic millimeter waves, with a special interest in diagnostic ultrasound imaging and its safety. For the last 21 years my research expanded to include electromagnetic millimeter waves, with a special interest in the mechanisms underlying millimeter wave therapy. Millimeter wave therapy has been widely used in the former Soviet Union with great reported success for many diseases, but is virtually unknown to Western physicians. I and the very capable members of my laboratory were able to demonstrate that the local exposure of skin to low intensity millimeter waves caused the release of endogenous opioids, and the transport of these agents by blood flow to all parts of the body resulted in pain relief and other beneficial effects.

Temperature and burn injury prediction of human skin exposed to microwaves: a model analysis

A one-dimensional multi-layer model is presented to characterize skin temperature rises and burn processes resulting from skin exposure to microwaves. Temperature variations and damage function analyses in the skin tissue exposed to microwaves were predicted depending on blood perfusion rate, thermal conductivity, power density, and exposure time. Thermal wave model was applied and the bio-heat transfer equation was solved using the finite difference time domain method. The thermal wave model of bio-heat transfer predicts a lower temperature rise than a model that uses Pennes' equation. When approaching steady state, the solutions overlaps with that obtained using the Pennes' equation. The results obtained may help to analyze the consequences of short-time high-power MW exposures in biological tissues.

Near-field dosimetry for in vitro exposure of human cells at 60 GHz

Due to the expected mass deployment of millimeter-wave wireless technologies, thresholds of potential millimeter-wave-induced biological and health effects should be carefully assessed. The main purpose of this study is to propose, optimize, and characterize a near-field exposure configuration allowing illumination of cells in vitro at 60 GHz with power densities up to several tens of mW/cm(2) . Positioning of a tissue culture plate containing cells has been optimized in the near-field of a standard horn antenna operating at 60 GHz. The optimal position corresponds to the maximal mean-to-peak specific absorption rate (SAR) ratio over the cell monolayer, allowing the achievement of power densities up to 50 mW/cm(2) at least. Three complementary parameters have been determined and analyzed for the exposed cells, namely the power density, SAR, and temperature dynamics. The incident power density and SAR have been computed using the finite-difference time-domain (FDTD) method. The temperature dynamics at different locations inside the culture medium are measured and analyzed for various power densities. Local SAR, determined based on the initial rate of temperature rise, is in a good agreement with the computed SAR (maximal difference of 5%). For the optimized exposure setup configuration, 73% of cells are located within the ±3 dB region with respect to the average SAR. It is shown that under the considered exposure conditions, the maximal power density, local SAR, and temperature increments equal 57 mW/cm(2) , 1.4 kW/kg, and 6 °C, respectively, for the radiated power of 425 mW.

Enhanced absorption of millimeter wave energy in murine subcutaneous blood vessels

The aim of the present study was to determine millimeter wave (MMW) absorption by blood vessels traversing the subcutaneous fat layer of murine skin. Most calculations were performed using the finite-difference time-domain (FDTD) technique. We used two types of models: (1) a rectangular block of multilayer tissue with blood vessels traversing the fat layer and (2) cylindrical models with circular and elliptical cross-sections simulating the real geometry of murine limbs. We found that the specific absorption rate (SAR) in blood vessels normally traversing the fat layer achieved its maximal value at the parallel orientation of the E-field to the vessel axis. At 42 GHz exposure, the maximal SAR in small blood vessels could be more than 30 times greater than that in the skin. The SAR increased with decreasing the blood vessel diameter and increasing the fat thickness. The SAR decreased with increasing the exposure frequency. When the cylindrical or elliptical models of murine limbs were exposed to plane MMW, the greatest absorption of MMW energy occurred in blood vessels located on the lateral areas of the limb model. At these areas the maximal SAR values were comparable with or were greater than the maximal SAR on the front surface of the skin. Enhanced absorption of MMW energy by blood vessels traversing the fat layer may play a primary role in initiating MMW effects on blood cells and vasodilatation of cutaneous blood vessels.