Body Specific Absorption Rate Research Articles

Effects of 3.5-GHz radiofrequency radiation on energy-regulatory hormone levels in the blood and adipose tissue.

In recent years exposure of living beings to radiofrequency radiation (RFR) emitted from wireless equipment has increased. In this study, we investigated the effects of 3.5-GHz RFR on hormones that regulate energy metabolism in the body. Twenty-eight rats were divided into four groups: healthy sham (n = 7), healthy RFR (n = 7), diabetic sham (n = 7), and diabetic RFR (n = 7). Over a month, each group spent 2 h/day in a Plexiglas carousel. The rats in the experimental group were exposed to RFR, but the sham groups were not. At the end of the experiment, blood and adipose tissues were collected from euthanized rats. Total antioxidant, total oxidant, hydrogen peroxide, ghrelin, nesfatin-1, and irisin were determined. Insulin expression in pancreatic tissues was examined by immunohistochemical analysis. Whole body specific absorption rate was 37 mW/kg. For the parameters analyzed in blood and fat, the estimated effect size varied within the ranges of 0.215-0.929 and 0.503-0.839, respectively. The blood and adipose nesfatin-1 (p = 0.002), blood and pancreatic insulin are decreased, (p = 0.001), gherelin (p = 0.020), irisin (p = 0.020), and blood glucose (p = 0.040) are increased in healthy and diabetic rats exposed to RFR. While nesfatin-1 are negatively correlated with oxidative stress, hyperglycemia and insulin, ghrelin and irisin are positively correlated with oxidative stress and hyperglycemia. Thus, RFR may have deleterious effects on energy metabolism, particularly in the presence of diabetes.

Study on RF Heating of Implants in Different Conductivity Medium

In MRI examination, RF heating of implants will affect the safety of implant wearers. The conductivity of various tissues in the human body is significantly different, and the medium conductivity will affect the distribution of the RF electric field. Therefore, it is necessary to study the RF heating of different medium conductivity. Based on the analysis of the principle of MRI RF heating, this study build the model of the bird cage coil, ASTM standard phantom and lead, and the conductivity of several typical human tissues is selected as the conductivity in the experiment. Then calculate the power deposition of the lead at 64 MHz. The results show that the medium conductivity has no effect on the distribution of electric field and power deposition, and the hot spot distribution remains unchanged under different conductivity; The smaller the conductivity is, the larger the power deposition of the lead is, and the greater the temperature rise of the lead caused by RF heating is; The change of conductivity and power deposition is approximately linear. At the limit of 2 W/kg whole body specific absorption rate(SAR), the conductivity decreases, and the wire power deposition increases sharply.

Design of Low-SAR and High On-Body Efficiency Tri-Band Smartwatch Antenna Utilizing the Theory of Characteristic Modes of Composite PEC-Lossy Dielectric Structures

A low specific absorption rate (SAR) and high on-body efficiency tri-band smartwatch antenna is designed utilizing the theory of characteristic modes (TCM) of composite perfect electric conductors and lossy dielectric structures. The antenna works in the GPS frequency band, WLAN 2.4 GHz/Bluetooth frequency band, and 5G frequency band. After analyzing the characteristic modes of the antenna and human body in the above three frequency bands, the characteristic modes with small modal coupling coefficients (MCCs) are selected and excited. Due to the small mutual coupling between the antenna and the human body, the proposed antenna has good performance on both SAR and on-body efficiency. Its measured 10 g average body SAR is lower than 1.3 W/kg. When it is placed 0 mm above the body, its on-body efficiency is 9.3%–9.88% in the GPS frequency band, 12%–14.2% in the WLAN 2.4 GHz/Bluetooth frequency band, and 17.3%–20.1% in the 5G frequency band.

Low-SAR MIMO Antenna Array Design Using Characteristic Modes for 5G Mobile Phones

A low specific absorption rate (SAR) multiple-input and multiple-output (MIMO) antenna array is designed for 5G mobile phones based on the theory of characteristic modes (TCMs). First, a geometrically symmetric dipole antenna is analyzed using TCM. The modal currents with symmetrical and reverse distributions are selected and excited to obtain the low-SAR antenna element. Then the antenna element is further optimized, and eight antenna elements constitute an MIMO array. The −6 dB impedance bandwidth of the proposed MIMO array is from 3.4 to 3.6 GHz. The isolations between different antenna elements are higher than 16 dB. Their total efficiencies range from 48% to 67%. Its envelope correlation coefficient (ECC) is lower than 0.08. The 1 g spatial-average head SAR and 10 g spatial-average body SAR of the proposed antenna are simulated and measured.

Spinal Cord Stimulators: Patient Safety and Adverse Outcomes from Imaging

<h3>Research Objectives</h3> A literature review of the current recommendation for SCS compatibility with MR imaging and a review of the Food and Drug Administration (FDA) approved spinal cord stimulation systems were performed. <h3>Design</h3> The literature review was completed using PubMed, the FDA website (www.fda.gov), and the SCS manufacturers' websites. <h3>Setting</h3> N/A. <h3>Participants</h3> N/A. <h3>Interventions</h3> N/A. <h3>Main Outcome Measures</h3> Is the usage of MRI safe in patients with spinal cord stimulators (SCS)? <h3>Results</h3> The current recommendations, composed on the basis of evidence-based medicine, reveal close adherence of an MRI with a 1.5T magnet and a mean total body specific absorption rate (SAR) of 0.9 W/kg or below which can promote patient safety and satisfaction, despite the variability between different SCS manufacturers1. Measurement of safety includes tearing of tissues due to rotational force generated by the magnetic field, acceleration of the device towards the bore of the magnet ("missile effect"), and burns caused by overheating of the device. <h3>Conclusions</h3> Strict adherence to an MRI with a 1.5T magnetic bore core and a SAR of 0.9 W/kg or below can promote patient safety despite the various SCS developed by manufacturers. Providers and technicians should be encouraged to seek specific SAR and Slew Rate and Field Strength conditions found on the manufacturers' website to yield the highest safety index and optimal image quality. <h3>Author(s) Disclosures</h3> None.

An automated computational tool to study MRI safety of implanted passive cardiovascular medical devices

Abstract Introduction The absorption of radiofrequency (RF) energy during an MRI procedure may cause tissue heating in the vicinity of an implanted device, such as a stent or a stented valve, potentially causing patient harm. Computational modeling and simulation (M&amp;S) can be used by medical device manufacturers to assess the RF-induced heating of implanted devices during an MRI scan and identify worst-case configurations within a given line of implants. However, despite the use of in-silico tools, a standard for in-silico testing of such problematic is still missing; The tool here proposed is a web-based application that automates the set-up and solution of RF-heating analysis, in line with existing standards for in-vitro testing. Methods The presented tool is part of a commercial web-based platform. The tool was developed in collaboration with the market leader of computer-aided engineering software and as part of a Research Collaboration Agreement with the American regulatory body. Commercial software was used to compute RF energy absorption and thermal heating of implantable medical devices replicating the directives of the ASTM F2182–11a Standard Test Method. The model is integrated in an automated workflow. Each simulation submitted by the user is sent to the cloud infrastructure for solution. Simulation results are stored in a database for later retrieval and report generation. Results The tool consists of a web-interface where the user can: i) upload the medical device computer-aided design (CAD) or select a simplified geometry from a library; ii) define the material properties of the device; ii) specify the desired input parameters specific to an MRI exposure scenario. Specifically, it is possible to study the device exposure: i) at different field frequencies (i.e., 64 MHz and 128 MHz); ii) at different powers (i.e., 2, 4 and 10 W/kg Whole body Specific Absorption Rate - SAR); iii) at different field polarizations (i.e., two circular and two linear); and iv) for different exposure time (i.e., form 240 s to 900 s). The presented tool allows the users to view and export results for each simulation, including electromagnetic fields, local SAR, and the temperature rise over time. Finally, the simulation results are summarized in an automatically generated report that follows regulatory guidance on M&amp;S reporting. Conclusion The presented web-based M&amp;S tool allows users to perform the thermal safety assessment of implantable medical devices during an MRI procedure following established good simulation practices. Minimal training or background in computer modeling is required to use the tool. Specific potential applications of the tool include RF-heating assessment of cardiovascular devices (e.g., stents, stented valves, stent retrievers). The proposed platform promotes the broader adoption of digital evidence in preclinical trials for RF safety analysis, supporting the device submission process and pre-market regulatory evaluation. Stent safety simulation result interface Funding Acknowledgement Type of funding source: None

Design of Low-SAR Mobile Phone Antenna: Theory and Applications

This article focuses on the design of a low specific absorption rate (SAR) mobile phone antennas. First, the interaction mechanism of the radiation fields of mobile phone antennas with nearby human tissues is analyzed by using boundary conditions of electromagnetics. The relations between SAR and the electric field are constructed. Then, a concept of reverse current is proposed to decrease the electric field radiated by the antenna at the air-tissue interface and, consequently, reduce the SAR of human tissues. Finally, a metal-rimmed mobile phone antenna is designed according to the proposed theory. The ground clearance of the designed antenna is 2 mm. Their measured normalized peak head and body SAR values are lower than 1.0 W/kg, much less than the SAR safety limit of 1.6 W/kg according to the guidelines of IEEE and FCC or 2.0 W/kg according to the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The measured -6 dB impedance bandwidths are 830-1040 and 1670-2730 MHz, respectively. The measured efficiencies are higher than -5 dB at the lower band and -4 dB at the higher band. The measured results prove that the proposed theory can provide guidance for the design of low-SAR mobile phone antennas.

Wireless Body Area Networks: UWB Wearable Textile Antenna for Telemedicine and Mobile Health Systems.

A compact textile ultra-wideband (UWB) antenna with an electrical dimension of 0.24λo × 0.24λo × 0.009λo with microstrip line feed at lower edge and a frequency of operation of 2.96 GHz is proposed for UWB application. The analytical investigation using circuit theory concepts and the cavity model of the antenna is presented to validate the design. The main contribution of this paper is to propose a wearable antenna with wide impedance bandwidth of 118.68 % (2.96–11.6 GHz) applicable for UWB range of 3.1 to 10.6 GHz. The results present a maximum gain of 5.47 dBi at 7.3 GHz frequency. Moreover, this antenna exhibits Omni and quasi-Omni radiation patterns at various frequencies (4 GHz, 7 GHz and 10 GHz) for short-distance communication. The cutting notch and slot on the patch, and its effect on the antenna impedance to increase performance through current distribution is also presented. The time-domain characteristic of the proposed antenna is also discussed for the analysis of the pulse distortion phenomena. A constant group delay less than 1 ns is obtained over the entire operating impedance bandwidth (2.96–11.6 GHz) of the textile antenna in both situations, i.e., side by side and front to front. Linear phase consideration is also presented for both situations, as well as configurations of reception and transmission. An assessment of the effects of bending and humidity has been demonstrated by placing the antenna on the human body. The specific absorption rate (SAR) value was tested to show the radiation effect on the human body, and it was found that its impact on the human body SAR value is 1.68 W/kg, which indicates the safer limit to avoid radiation effects. Therefore, the proposed method is promising for telemedicine and mobile health systems.

Toward 7T breast MRI clinical study: safety assessment using simulation of heterogeneous breast models in RF exposure

To facilitate assessment of RF power deposition and temperature rise within the breast, we present a method to seamlessly join heterogeneous breast models with standard whole-body models and demonstrate simulations at 7 T. Finite-difference time-domain electromagnetic and bioheat simulations are performed to analyze the specific absorption rate (SAR) and temperature rise distributions in 36 Breast Imaging Reporting and Data System (BI-RADS) categorized breast models fused to 2 female whole-body models while transmitting from a 7T breast volume coil. The breast models are uncompressed in the prone position and feature heterogeneous tissue contents; fusion with human models uses affine transformation and the level-set method. The fusion method produces a continuous transient from the chest region to the posterior portion of breast models while preserving the original volume and shape of breast models. Simulation results of both Ella and Hanako models indicate that the maximum local SAR, partial body SAR, and local tissue temperature rise are positively correlated with both breast density and the highest BI-RADS density classification. Additionally, maximum local tissue temperature rise is positively correlated with maximum 10-g SAR values. Fibroglandular tissue content plays an important role in the distribution of SAR and temperature rise within breast tissue. The combined body-breast models preserve the integrity of breast models while concurrently exhibiting the loading of whole-body human models. The procedures presented in this simulation study facilitate safety assessments for breast MRI across the population at both clinical and ultrahigh field strengths.

Alteration of adaptive behaviors of progeny after maternal mobile phone exposure.

Exposure of pregnant women to radiofrequency (RF) devices raises questions on their possible health consequences for their progeny. We examined the hazard threshold of gestational RF on the progeny's glial homeostasis, sensory-motor gating, emotionality, and novelty seeking and tested whether maternal immune activation would increase RF toxicity. Pregnant dams were daily restrained with loop antennas adjoining the abdomen (fetus body specific absorption rates (SAR): 0, 0.7, or 2.6W/kg) and received three lipopolysaccharide (LPS) intra-peritoneal injections (0 or 80μg/kg). Scores in the prepulse startle inhibition, fear conditioning, open field, and elevated plus maze were assessed at adolescence and adulthood. Glial fibrillary acidic protein (GFAP) and interleukines-1β (ILs) were quantified. LPS induced a SAR-dependent reduction of the prepulse startle inhibition in adults. Activity in the open field was reduced at 2.6W/kg at adolescence. GFAP and ILs, emotional memory, and anxiety-related behaviors were not modified. These data support the hypothesis that maternal immune activation increased the developmental RF exposure-induced long-term neurobiological impairments. These data support the fact that fetuses who receive combined environmental exposures with RF need special attention for protection.

Assessment of exposure to radio frequency electromagnetic fields from smart utility meters in GB; part II) numerical assessment of induced SAR within the human body.

Human body exposure to radiofrequency electromagnetic waves emitted from smart meters was assessed using various exposure configurations. Specific energy absorption rate distributions were determined using three anatomically realistic human models. Each model was assigned with age- and frequency-dependent dielectric properties representing a collection of age groups. Generalized exposure conditions involving standing and sleeping postures were assessed for a home area network operating at 868 and 2,450 MHz. The smart meter antenna was fed with 1 W power input which is an overestimation of what real devices typically emit (15 mW max limit). The highest observed whole body specific energy absorption rate value was 1.87 mW kg-1 , within the child model at a distance of 15 cm from a 2,450 MHz device. The higher values were attributed to differences in dimension and dielectric properties within the model. Specific absorption rate (SAR) values were also estimated based on power density levels derived from electric field strength measurements made at various distances from smart meter devices. All the calculated SAR values were found to be very small in comparison to International Commission on Non-Ionizing Radiation Protection limits for public exposure. Bioelectromagnetics. 39:200-216, 2018. © 2017 Wiley Periodicals, Inc.

Investigating the effect of coil model losses on computational electromagnetic exposure of an ASTM phantom at 64 MHz MRI.

The goal of this work is to investigate the effect of coil losses on the electromagnetic field generated in an ASTM phantom by a birdcage coil. The study was based on different numerical implementations of an RF body coil at 64 MHz, using the same 3D EM and RF circuit co-simulation procedure. The coil quality factor was evaluated with respect to losses due to power feed mismatch and to resistive losses of the coil components. The results of the study showed that the magnetic field at the coil iso-center, normalized to the square root of the whole body specific absorption rate, depends on the coil quality factor.

Design of PIFA With Metamaterials for Body-SAR Reduction in Wearable Applications

This letter proposes a planar inverted-F antenna (PIFA) with an artificial magnetic conductor (AMC) structure for body specific absorption rate (SAR) reduction in a wideband-code-division-multiple-access band. As wireless devices such as wearable phones and smart watches become more common, health risks originating from electromagnetic waves generated by devices worn on the body have become an important issue. AMC structures are a type of metamaterial that can act as a perfect magnetic conductor and control the radiation pattern of an antenna. Thus, an antenna with an AMC structure is capable of preventing hazardous electromagnetic fields being emitted in the direction of the body. The S-parameters, radiation patterns, total radiated power values, and SAR values of such a designed structure are presented. The results demonstrate a 43.3% reduction in the SAR value at the center frequency. Thus, the human body can be protected from electromagnetic waves using metamaterials.

Equivalent Permittivity Based on Debye Model of Blood and Its SAR

Dielectric parameters vary with frequencies are important properties of biological systems, which determine the absorption rates of electromagnetic radiation in human body. Two phase dielectric model is considered to investigate the dielectric properties of human blood in this paper. This paper systematically calculates the body's specific absorption rate of electromagnetic fields at low frequencies based on the dielectric properties obtained from the Debye model. This study could lay foundation not only for the theoretical basis for further study on electrical properties of biological tissue, but also for the exposure limits of health standard on electromagnetic radiation.

2.45 GHz Microwave Radiation Impairs Learning and Spatial Memory via Oxidative/Nitrosative Stress Induced p53-Dependent/Independent Hippocampal Apoptosis: Molecular Basis and Underlying Mechanism.

A close association between microwave (MW) radiation exposure and neurobehavioral disorders has been postulated but the direct effects of MW radiation on central nervous system still remains contradictory. This study was performed to understand the effect of short (15 days) and long-term (30 and 60 days) low-level MW radiation exposure on hippocampus with special reference to spatial learning and memory and its underlying mechanism in Swiss strain male mice, Mus musculus. Twelve-weeks old mice were exposed to 2.45 GHz MW radiation (continuous-wave [CW] with overall average power density of 0.0248 mW/cm(2) and overall average whole body specific absorption rate value of 0.0146 W/Kg) for 2 h/day over a period of 15, 30, and 60 days). Spatial learning and memory was monitored by Morris Water Maze. We have checked the alterations in hippocampal oxidative/nitrosative stress, neuronal morphology, and expression of pro-apoptotic proteins (p53 and Bax), inactive executioner Caspase- (pro-Caspase-3), and uncleaved Poly (ADP-ribose) polymerase-1 in the hippocampal subfield neuronal and nonneuronal cells (DG, CA1, CA2, and CA3). We observed that, short-term as well as long-term 2.45 GHz MW radiation exposure increases the oxidative/nitrosative stress leading to enhanced apoptosis in hippocampal subfield neuronal and nonneuronal cells. Present findings also suggest that learning and spatial memory deficit which increases with the increased duration of MW exposure (15 < 30 < 60 days) is correlated with a decrease in hippocampal subfield neuronal arborization and dendritic spines. These findings led us to conclude that exposure to CW MW radiation leads to oxidative/nitrosative stress induced p53-dependent/independent activation of hippocampal neuronal and nonneuronal apoptosis associated with spatial memory loss.

Studies on SAR reduction using impedance mismatch loss for simple printed 5 GHz monopoles

ABSTRACTA new approach to decreasing the specific absorption rate (SAR) for simple, printed monopoles in the 5‐GHz (5150–5825 MHz) WLAN band is presented. The antennas here are the conventional T‐shaped monopoles with a shorting strip located in between the top radiating arm and the antenna ground. The antenna was devised to be less matched (6 dB return loss) with 0.59 dB more insertion loss, yet the far‐field characteristics were slightly degraded and still met the industrial antenna specifications. It was found that the decreased near‐field radiation can be obtained, and the measured body SAR was substantially lowered by about 35–36% with an air gap of 2 mm directly from the antenna, which was provided by various input power. Details of the design approach and the results are discussed in the article. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2376–2384, 2015

Planar small-size LTE/WWAN tablet computer antenna with eight-band operation

By attaching a C-shaped parasitic monopole strip on the backside of the antenna, a novel compact eight-band monopole antenna (MA) is proposed and embedded in the LTE/WWAN tablet computer. The operating impedance bandwidths of 264/997 MHz can be obtained across the LTE/WWAN bands, respectively. Given that the overall antenna size is only 35 × 10 × 0.8 mm3, the proposed planar MA provides more than 22% reduction in antenna size over that of the conventional ones. Meanwhile, this small-size MA provides the measured peak gains and antenna efficiencies of 2.0/3.2 dBi and 60/66% for the LTE/WWAN bands, respectively. Additionally, to fulfill the limitation of 1.6 W/kg of the 1-g body specific absorption rate (SAR) requirement for mobile device applications, the proposed planar compact MA is deposited inside the tablet computer for the study of radiating performance.

Effect of Radiofrequency Waves Emitted From Conventional WIFI Devices on Some Oxidative Stress Parameters in Rat Kidney

Wireless Fidelity (WIFI) is widely used in cell phones, computers and electronic devices to access the Internet. It is unclear whether or not the frequency range of the WIFI has any harmful biological effects. In this report, the effect of standard 2.45 GHz radio frequency source (Averaged whole body specific absorption rate (SAR) 0.01 W/ Kg, 24 hours daily for 40 successive days) on some oxidative stress parameters was examined in Wistar female rats. We found that exposure to WIFI decreased the malondialdehyde levels as well as the glutathione-S-transferase and catalase activities. Moreover, the activity of superoxide dismutase showed significant increase in the WIFIexposed group relative to the control group. Meanwhile, kidney functions were found to be unaffected. In addition, no significant histological alterations in rats’ kidneys were detected in WIFI-exposed group. These results indicate that WIFI exposure used in the present study implies oxidative alterations in rat kidneys, which does not result in severe consequences due to the effective activity of the antioxidant enzyme system of the rat kidneys.

The effect of 900 and 1800 MHz GSM-like radiofrequency irradiation and nicotine sulfate administration on the embryonic development of Xenopus laevis

The aim of this study was to investigate the effects of GSM-like radiofrequency electromagnetic radiation (RF EMR) and nicotine sulfate (NS) exposure on Xenopus embryonic development.The developmental effects of GSM-like RF-EMR (900–1800MHz, at a SAR value of 1W/kg and NS on Xenopus laevis embryos were investigated). Following the application of radiofrequency radiation and/or NS administration, the embryos were closely examined in order to determine their possible teratogenic effects. Xenopus frogs obtained from the Department of Physiology of the Cukurova University, in accordance described by the Standard Guide of the American Society for Testing and Materials (ASTM). Following the exposure of Xenopus embryos to RF-EMR at 900 and 1800MHz (1.0W/kg) for 4, 6 and 8h; the whole body specific energy absorption rate (SAR) of the embryos was calculated. With the exception of irradiation at 1800MHz no dramatic developmental anomalies were observed in the Xenopus embryos in association with RF-EMR applications. Combined RF-EMR and NS applications resulted in dramatic abnormalities and death among the Xenopus embryos. The study results indicated that GSM-like RF-EMR (e.g. radiation from cell phones) was not as harmful to Xenopus embryos as might have been expected. However, the combined effects of GSM-like RF-EMR and NS on Xenopus embryos were more severe than the effect of RF-EMR or NS alone. In conclusion, the study results appear to suggest that the combined use of nicotine and cell phones might result in more pronounced detrimental effects on the health of smokers.

Planar Small-Size Eight-Band LTE/WWAN Monopole Antenna for Tablet Computers

This work describes a novel small-size monopole antenna with eight-band LTE/WWAN operation in tablet computers by introducing a G-shaped driven monopole strip. The subsequently obtained impedance bandwidths across dual operating bands approach 264/1046 MHz at the LTE and WWAN bands, respectively. Given that the overall antenna size is only 35 ×10 ×0.8 mm 3 , the proposed planar monopole antenna provides more than 40% reduction in antenna size over that of the conventional ones. Additionally, the measured peak gains and antenna efficiencies are approximately 3.6/5.2 dBi and 67/70% for the LTE/WWAN bands, respectively. Moreover, the proposed planar compact antenna can be deposited inside the tablet computer and fulfills the body specific absorption rate (SAR) requirement (for 1-g body tissue) for mobile device applications.