Millimeter‐wave emissivity as a metric for the non‐contact diagnosis of human skin conditions

A half‐space electromagnetic model of human skin over the band 30–300 GHz was constructed and used to model radiometric emissivity. The model showed that the radiometric emissivity rose from 0.4 to 0.8 over this band, with emission being localized to a layer approximately one millimeter deep in the skin. Simulations of skin with differing water contents associated with psoriasis, eczema, malignancy, and thermal burn wounds indicated radiometry could be used as a non‐contact technique to detect and monitor these conditions. The skin emissivity of a sample of 30 healthy volunteers, measured using a 95 GHz radiometer, was found to range from 0.2 to 0.7, and the experimental measurement uncertainty was ±0.002. Men on average were found to have an emissivity 0.046 higher than those of women, a measurement consistent with men having thicker skin than women. The regions of outer wrist and dorsal forearm, where skin is thicker, had emissivities 0.06–0.08 higher than the inner wrist and volar forearms where skin is generally thinner. Recommendations are made to develop a more sophisticated model of the skin and to collect larger data sets to obtain a deeper understanding of the signatures of human skin in the millimeter wave band. Bioelectromagnetics. 38:559–569, 2017. © 2017 The Authors. Bioelectromagnetics published by Wiley Periodicals, Inc.     

Assessment of the efficacy and safety of low frequency,low intensity magnetic fields in patients after knee endoprosthesis plasty. Part 1: In vitro safety

The purpose of this in vitro study was to assess the potential influence of low frequency, low intensity magnetic fields (rectangular pulse, 5 mT, 30 Hz) applied in therapy on the temperature, contact electric potential, and magnetization in knee endoprosthesis, which might be dangerous for implantation and stability of knee prosthesis, and later slacking it off, causing postoperative complications. The experimental investigation was carried out on a knee endoprosthesis which had been placed in a container with physiological saline. The prosthesis located inside the container was under the exposure of the magnetic field applied by a solenoid. The results indicated that magnetic fields did not influence thermal and electromagnetic properties of knee endoprosthesis in vitro. The magnetic fields of examined parameters should not be dangerous for implantation and stability of knee endoprosthesis. Bioelectromagnetics 30:159–162, 2009. © 2008 Wiley‐Liss, Inc.     

Factors Affecting Risk Perception of Electromagnetic Waves From 5G Network Base Stations

The coverage of the fifth-generation network has increased steadily since the network was introduced in 2019. However, public protests around the globe against the construction of 5G network base stations have continued to occur for fear that electromagnetic (EM) waves emitted from the stations would cause adverse health effects. To identify factors that have contributed to such increased risk perception, we conducted a cross-sectional study using data obtained from a survey that assessed Korean adults’ risk perception of EM wave-related objects. We found that female gender, high level of perceived exposure to EM waves, evaluation of public policies as ineffective, and high level of objective knowledge on EM waves were associated with increased risk perception. Furthermore, we found that higher ratings on a few risk characteristics such as “personal knowledge,” “seriousness of the risk to future generations,” “dreadfulness,” and “severity of consequences” were also associated with increased risk perception as well. Bioelectromagnetics. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society     

Millimeter‐Wave Heating in In Vitro Studies: Effect of Convection in Continuous and Pulse‐Modulated Regimes

Shallow penetration of millimeter waves (MMW) and non‐uniform illumination in in vitro experiments result in a non‐uniform distribution of the specific absorption rate (SAR). These SAR gradients trigger convective currents in liquids affecting transient and steady‐state temperature distributions. We analyzed the effect of convection on temperature dynamics during MMW exposure in continuous‐wave (CW) and pulsed‐wave (PW) amplitude‐modulated regimes using micro‐thermocouples. Temperature rise kinetics are characterized by the occurrence of a temperature peak that shifts to shorter times as the SAR of the MMW exposure increases and precedes initiation of convection in bulk. Furthermore, we demonstrate that the liquid volume impacts convection. Increasing the volume results in earlier triggering of convection and in a greater cooling rate after the end of the exposure. In PW regimes, convection strongly depends on the pulse duration that affects the heat pulse amplitude and cooling rate. The latter results in a change of the average temperature in PW regime. Bioelectromagnetics. 2019;40:553–568. © 2019 Bioelectromagnetics Society.     

Frequency‐dependent and montage‐based differences in phosphene perception thresholds via transcranial alternating current stimulation

It is well known that applying transcranial alternating current stimulation (tACS) to the scalp can generate artefactual visual perceptions of flashing or shimmering light known as phosphenes. The thresholds for generating these phosphenes have been used by international standards bodies to provide conservative estimates of the field strength required to interfere with human neural functioning and set safety limits accordingly. However, the precise relationship between electric currents and phosphene perception thresholds remains uncertain. The present study used tACS to systematically investigate the effects of the location and the frequency of stimulation on phosphene perception thresholds. These thresholds were obtained from 24 participants using a within‐subject design as a function of scalp stimulation sites (FPz‐Cz versus Oz‐Cz) and stimulation frequency (2–30 Hz in steps of 2 Hz). Phosphene perception thresholds were consistently lower for FPz‐Cz stimulation, and regardless of tACS location were lowest for 16 Hz stimulation. Threshold variation between participants was very small, which is meaningful when setting standards based on phosphenes. Bioelectromagnetics. 2019;40:365–374. © 2019 Bioelectromagnetics Society.     

Efficient and Reliable Assessment of the Maximum Local Tissue Temperature Increase at the Electrodes of Medical Implants under MRI Exposure

Standard risk evaluations posed by medical implants during magnetic resonance imaging (MRI) includes (i) the assessment of the total local electromagnetic (EM) power (P) absorbed in the vicinity of the electrodes and (ii) the translation of P into a local in vivo tissue temperature increase ?T (P2?T) in animal experiments or simulations. We investigated the implant/tissue modeling requirements and associated uncertainties by applying full‐wave EM and linear bioheat solvers to different implant models, incident field conditions, electrode configurations, and tissue models. Results show that the magnitude of the power is predominately determined by the lead, while the power distribution, and the P2?T conversion, is determined by the electrode and surrounding tissues. P2?T is strongly dependent on the size of the electrode, tissue type in contact with the electrode, and tissue inhomogeneity (factor of >2 each) but less on the modeling of the lead (<±10%) and incident field distribution along the lead (<±20%). This was confirmed by means of full‐wave simulations performed with detailed high‐resolution anatomical phantoms exposed to two commonly used MRI clinical scenarios (64 and 128 MHz), resulting in differences of less than 6%. For the determination of P2?T, only the electrode and surrounding tissues must be modeled in great detail, whereas the lead can be modeled as a computationally efficient simplified structure exposed to a uniform field. The separate assessments of lead and electrode reduce the overall computational effort by several orders of magnitude. The errors introduced by this simplification can be considered by uncertainty terms. Bioelectromagnetics. 2019;40:422–433. © 2019 Bioelectromagnetics Society.     

Morphological Changes Induced By Extremely Low‐Frequency Electric Fields

In this paper, morphological effects of electric fields on avian erythrocytes (nucleated red blood cells) have been studied in detail. Morphological changes include rounding and cytoplasm transparency. It has been shown that the effect is non‐thermal. Careful imaging and image analyses have been carried out to show that the degree of this effect is frequency‐dependent, and has a higher conversion rate at higher temperatures. Furthermore, to better understand the mechanisms behind the morphological changes, we investigated the dedifferentiation hypothesis and performed a series of tests on avian erythrocytes including fluorescence spectroscopy for hemoglobin, and tests on human umbilical cord blood, mesenchymal stem cells, and bone marrow mesenchymal stem cells including flow‐cytometry analysis for expression of certain markers and calcium staining. Bioelectromagnetics. 2019;40:375–390. © 2019 Bioelectromagnetics Society.     

Magnetic Resonance Examinations of Patients With Implanted Active Devices. A Low‐Cost Approach in Slew Rate Evaluation

Time‐varying magnetic field gradients involved in magnetic resonance examinations can damage implanted electronic systems. The quantity related to this side effect is the gradient slew rate, which is usually not directly available on magnetic resonance console. The present study proposes a low‐cost approach in slew rate assessment, which is useful in risks versus benefits evaluation as well as in sequences optimization. The experimental method is based on an analog circuit, which senses the output voltage of the scanner waveform generator. This allows taking easy and reliable slew rate measurements, even during clinical examinations on patients. Whereas previous studies required managing a considerable amount of data, the present work addresses only the maximal slew rate of any clinical sequence. Experimental results show that the smooth gradient mode, selectable on the two scanners examined, is very effective in patient safety improvement. In particular, it reduces slew rate values in the range from 52.4 up to 132.4 T m^‐1 s^‐1, i.e. far below the interval 216–346 T m^‐1 s^‐1, indicated as slew rate tolerance limit of modern implanted electronic devices. Bioelectromagnetics. 2019;40:512–521. © 2019 Bioelectromagnetics Society     

Anatomical Model Uncertainty for RF Safety Evaluation of Metallic Implants Under MRI Exposure

The Virtual Population (ViP) phantoms have been used in many dosimetry studies, yet, to date, anatomical phantom uncertainty in radiofrequency (RF) research has largely been neglected. The objective of this study is to gain insight, for the first time, regarding the uncertainty in RF‐induced fields during magnetic resonance imaging associated with tissue assignment and segmentation quality and consistency in anatomical phantoms by evaluating the differences between two generations of ViP phantoms, ViP1.x and ViP3.0. The RF‐induced 10g‐average electric (E‐) fields, tangential E‐fields distribution along active implantable medical devices (AIMD) routings, and estimated AIMD heating were compared for five phantoms that are part of both ViP1.x and ViP3.0. The results demonstrated that differences exceeded 3 dB (?29%, +41%) for local quantities and 1 dB (±12% for field, ±25% for power) for integrated and volume‐averaged quantities (e.g., estimated AIMD‐heating and 10 g‐average E‐fields), while the variation across different ViP phantoms of the same generation can exceed 10 dB (?68% and +217% for field, ?90% and +900% for power). In conclusion, the anatomical phantom uncertainty associated with tissue assignment and segmentation quality/consistency is larger than previously assumed, i.e., 0.6 dB or ±15% (k = 1) for AIMD heating. Further, multiple phantoms based on different volunteers covering the target population are required for quantitative analysis of dosimetric endpoints, e.g., AIMD heating, which depend on patient anatomy. Phantoms with the highest fidelity in tissue assignment and segmentation should be used, as these ensure the lowest uncertainty and possible underestimation of exposure. To verify that the uncertainty decreases monotonically with improved phantom quality, the evaluation of differences between phantom generations should be repeated for any improvement in segmentation. Bioelectromagnetics. 2019;40:458–471. © 2019 Bioelectromagnetics Society     

A Vascular Thrombus Therapy Method Based on Magnetic‐Induced Vibration

A vascular thrombus therapy method based on magnetic‐induced vibration is presented. It is a mechanicalway of removing vascular thrombus that adopts the combined use of two concepts, namely (i) magnetic‐induced vibration of magnetostrictive materials and (ii) changes in physical form of thrombus under high‐frequency impact and vibration. This method has many advantages that (i) eliminate the side effects of drug treatment, (ii) reduce the complexity of traditional mechanical method, and (iii) improve the reliability of treatment. Practical results obtained from the simulations and experiments are included. They verify the proposed system and indicate that this method can effectively treat vascular thrombus and reduce patient's suffering and costs. Bioelectromagnetics. 2019;40:391–401. © 2019 Bioelectromagnetics Society.     

Characterization of Levels of Extremely Low Frequency Magnetic Fields Emitted From Portable Hand‐Held Fans

This study aims to assess the levels of extremely low frequency magnetic fields (ELF‐MF) emitted from portable hand‐held fans (HHFs) and their principal frequency and to identify factors influencing these levels. We collected a total of eleven models of HHF and monitored the ELF‐MF as a function of fan speed and distance from the fan. EMDEX II was used to monitor the ELF‐MF. An SMP2 EMF‐meter equipped with a P400 field probe was used to determine the levels of ELF‐MF and the frequency spectrum. Ten of the fans, excluding only one bladeless‐fan model, emitted a high level of ELF‐MF near the source of the HHF direct‐current motor. The maximum measured level of ELF‐MF ranged from 14.07 to 218.7 µT. All measurements of the ELF‐MF taken within 10 cm from the HHFs showed values higher than 1.0 µT. ELF‐MF levels were found to decrease markedly with distance, regardless of the HHF product. The level of ELF‐MF rose noticeably with increased fan speed. The speed of and distance from the HHF significantly influenced the level of ELF‐MF. All principal frequencies ranged from 1 to 300 Hz, which falls in the typical range of ELF. Bioelectromagnetics. 2019;40:569–577. © 2019 Bioelectromagnetics Society.     

Application of Bio‐Impedance Analysis to Estimate the Condition of Yellowtail (Seriola quinqueradiata) Muscle at Different Storage Temperatures

Changes in impedance at 2 kHz, adenosine triphosphate (ATP) content, and muscle contraction were evaluated in yellowtail during 0 (ice), 5, 10, 15, and 20°C storage. Histological changes during ice storage were also measured. At any temperature, although impedance increased with both rigor mortis and ATP consumption during early storage, it began to decrease rapidly when ATP was almost depleted. Moreover, temporarily increasing impedance had a strong relationship with ATP content; decreasing impedance had a significant correlation with storage temperature after ATP depletion. Furthermore, impedance increased with narrowing of intercellular spaces when sarcolemma was intact and decreased with expansion of intercellular spaces when sarcolemma was leaky. Meanwhile, changes of sarcolemma and intercellular spaces were accompanied by ATP change. Thus, ATP is one significant physiological factor for impedance change, and temperature greatly influenced impedance after depletion of ATP. Results suggest that impedance analysis can be used as a convenient and nondestructive method to diagnose condition of tissue at different storage temperatures. Bioelectromagnetics. 2019;40:488–497. © 2019 Bioelectromagnetics Society     

Evaluation of Radiofrequency and Extremely Low‐Frequency Field Levels at Children's Playground Sites in Greece From 2013 to 2018

From 2013 to 2018, in‐situ measurements of radiofrequency (RF) electromagnetic fields (EMF) and extremely low‐frequency (ELF) electric and magnetic fields in 317 existing and under‐construction children's playground facilities, in 16 municipalities all over Greece, were carried out by the Greek Atomic Energy Commission (EEAE). These measurements were conducted following legislative framework established in 2009, which requires that compliance with the established exposure limits for EMFs should be verified in playground areas. The results are presented by the value of the electric field (E) and exposure ratio (Λ) for the RF EMF, as well as the value of the electric field (E) and magnetic flux density (B) for the ELF electric and magnetic fields. Statistical analysis tools were applied on measurement data and conclusions have been made, taking into consideration: (i) environment type (urban/suburban), and (ii) vicinity to any transmitting installations. Measurement results correspond to the typical EMF background levels for each environment type. Concerning the environment type, RF EMF, and ELF electric/magnetic field measurements reveal no differentiation between urban and suburban environments. Bioelectromagnetics. 2019;40:602–605. © 2019 Bioelectromagnetics Society.     

Electromagnetic and thermal evaluation of an applicator specialized to permit high‐resolution non‐perturbing optical evaluation of cells being irradiated in the W‐band

To permit epi‐illuminated, high‐resolution optical microscopy of cells in monolayer culture during unperturbed W‐band (75–110 GHz) irradiation, a new class of applicator has been developed based upon WR10 rectangular waveguide components: the cells are normally plated onto the underside of a coverslip which is then placed against the under side of a waveguide flange and receives a roughly circular exposure pattern, with the ±1 dB central spot roughly 1 mm in diameter. Constructed and tested with 94 GHz millimeter waves, water‐immersion optics, and free‐convection cooling, the applicator works robustly and permits SARs at the cell layer as high as 4500 W/kg before the steady‐state temperature rise at the cell layer exceeds 0.5 K. Bioelectromagnetics 31:140–149, 2010. © 2009 Wiley‐Liss, Inc.     

Discussion on Spatial and Time Averaging Restrictions Within the Electromagnetic Exposure Safety Framework in the Frequency Range Above 6 GHz for Pulsed and Localized Exposures

Both the current and newly proposed safety guidelines for local human exposure to millimeter-wave frequencies aim at restricting the maximum local temperature increase in the skin to prevent tissue damage. In this study, we show that the application of the current and proposed limits for pulsed fields can lead to a temperature increase of 10°C for short pulses and frequencies between 6 and 30 GHz. We also show that the proposed averaging area of 4 cm², that is greatly reduced compared with the current limits, does not prevent high-temperature increases in the case of narrow beams. A realistic Gaussian beam profile with a 1 mm radius can result in a temperature increase about 10 times higher than the 0.4°C increase the same averaged power density would produce for a plane wave. In the case of pulsed narrow beams, the values for the time and spatial-averaged power density allowed by the proposed new guidelines could result in extreme temperature increases. Bioelectromagnetics. 2020;41:164–168. © 2019 Bioelectromagnetics Society.     

Temperatures in Pigs During 3 T MRI Temperatures,Heart Rates,and Breathing Rates of Pigs During RF Power Deposition in a 3 T (128 MHz) Body Coil

Exposure to radiofrequency (RF) power deposition during magnetic resonance imaging (MRI) induces elevated body‐tissue temperatures and may cause changes in heart and breathing rates, disturbing thermoregulation. Eleven temperature sensors were placed in muscle tissue and one sensor in the rectum (measured in 10 cm depth) of 20 free‐breathing anesthetized pigs to verify temperature curves during RF exposure. Tissue temperatures and heart and breathing rates were measured before, during, and after RF exposure. Pigs were placed into a 60‐cm diameter whole‐body resonator of a 3 T MRI system. Nineteen anesthetized pigs were divided into four RF exposure groups: sham (0 W/kg), low‐exposure (2.7 W/kg, mean exposure time 56 min), moderate‐exposure (4.8 W/kg, mean exposure time 31 min), and high‐exposure (4.4 W/kg, mean exposure time 61 min). One pig was exposed to a whole‐body specific absorption rate (wbSAR) of 11.4 W/kg (extreme‐exposure). Hotspot temperatures, measured by sensor 2, increased by mean 5.0 ± 0.9°C, min 3.9; max 6.3 (low), 7.0 ± 2.3°C, min 4.6; max 9.9 (moderate), and 9.2 ± 4.4°C, min 6.1, max 17.9 (high) compared with 0.3 ± 0.3°C in the sham‐exposure group (min 0.1, max 0.6). Four time‐temperature curves were identified: sinusoidal, parabolic, plateau, and linear. These curve shapes did not correlate with RF intensity, rectal temperature, breathing rate, or heart rate. In all pigs, rectal temperatures increased (2.1 ± 0.9°C) during and even after RF exposure, while hotspot temperatures decreased after exposure. When rectal temperature increased by 1°C, hotspot temperature increased up to 42.8°C within 37 min (low‐exposure) or up to 43.8°C within 24 min (high‐exposure). Global wbSAR did not correlate with maximum hotspot. Bioelectromagnetics. 2021;42:37–50. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society     

Effects of 171 MHz Low‐Intensity Electromagnetic Field on Glucocorticoid and Mineral Corticoid Activity of the Adrenal Glands of Rats

A sub‐acute electromagnetic field (EMF) biological effect study was carried out on rats exposed in the Transverse ElectroMagnetic exposure chamber at 171 MHz Continuous Wave (CW). The experiments involved three exposure levels (15, 25, and 35 V/m) for 15 days with triplicate parallel sham‐exposed controls in each series. All exposure conditions were simulated for the evaluation of the electromagnetic energy distribution and specific absorption rate (SAR) in the rat phantoms. Studies have shown a biphasic biological response depending on time and absorbed electromagnetic energy. Under low SAR, approximately 0.006 W/kg, EMF exposure leads to the stimulation of adrenal gland activity. This process is accompanied by an initial increase of daily excretion of corticosterone and Na⁺, which is seen as a higher Na⁺/K⁺ ratio, followed by a decrease of these parameters over time. It is possible that EMF exposure causes a stress response in animals, which is seen as an increased adrenal activity. Bioelectromagnetics. 2019;40:578–587. © 2019 Bioelectromagnetics Society.     

Proposal of 28 GHz In Vitro Exposure System Based on Field Uniformity for Three‐Dimensional Cell Culture Experiments

This paper proposes a novel in vitro exposure system operating at millimeter‐wave (mmWave) 28 GHz, one of the frequency bands under consideration for fifth generation (5G) communication. We employed the field uniformity concept along cross‐sectional observation planes at shorter distances from the radiation antenna for better efficiency and a small‐size system. A choke‐ring antenna was designed for this purpose in consideration of a wider beamwidth (BW) and a symmetric far‐field pattern across three principal planes. The permittivity of Dulbecco's modified Eagle's medium solution was measured to examine the specific absorption rate (SAR) of the skin cell layer inside a Petri dish model for a three‐dimensional (3D) cell culture in vitro experiment. The best deployment of Petri dishes, taking into account a geometrical field symmetry, was proposed. Local SAR values within the cell layer among the Petri dishes were determined with different polarization angles. It was determined that this polarization effect should be considered when the actual exposure and deployment were conducted. We finally proposed an in vitro exposure system based on the field uniformity including downward exposure from an antenna for 3D cell culture experiments. A small‐size chamber system was obtained, and the size was estimated using the planar near‐field chamber design rule. Bioelectromagnetics. 2019;40:445–457. © 2019 Bioelectromagnetics Society     

The Effect of Extremely Low‐Frequency Electromagnetic Fields on the Prevalence of Musculoskeletal Disorders and the Role of Oxidative Stress

Extremely low‐frequency electromagnetic fields (ELF‐EMFs) may cause negative health effects. This study aimed to investigate the direct and indirect effects of chronic exposure to extremely low‐frequency electric and magnetic fields on the prevalence of musculoskeletal disorders (MSDs). In this cross‐sectional study, 152 power plant workers were enrolled. The exposure level of employees was measured based on the IEEE Std C95.3.1 standard. Superoxide dismutase (SOD), catalase (Cat), glutathione peroxidase (GPx), total antioxidant capacity (TAC), and malondialdehyde (MDA) (independent variables) were measured in the serum of subjects. The Nordic musculoskeletal questionnaire was used to assess MSDs (dependent variable). The mean exposure of electric and magnetic fields were 4.09 V/m (standard deviation [SD] = 4.08) and 16.27 µT (SD = 22.99), respectively. Increased levels of SOD, Cat, GPx, and MDA had a direct significant relation with MSDs. In the logistic regression model, SOD (odds ratio [OR] = 0.952, P = 0.026), GPx (OR = 0.991, P = 0.048), and MDA (OR = 0.741, P = 0.021) were significant predictors of MSDs. ELF‐EMFs were not related to MSDs directly; however, increased levels of oxidative stress may cause MSDs. Bioelectromagnetics. 2019;40:354–360. © 2019 Bioelectromagnetics Society.