This report results from a contract tasking National Institute of Public Health as follows: The contractor will investigate the role of averaging mass on calculated specific absorption rate (SAR) values in predicting the effects of radiofrequency radiatio...
National Technical Information Service (NTIS)
The electric field distribution of the rate of energy absorption referred to as the specific absorption rate (SAR) in a biological body is a complex function of several exposure parameters such as frequency, intensity of the incident field, polarization, source to object configur...
EPA Science Inventory
...National Standards Institute (ANSI) for localized specific absorption rate (�SAR�) in Section 4.2 of �IEEE Standard for Safety...Maryland 20814. SAR is a measure of the rate of energy absorption due to exposure to an RF transmitting source. ...
Code of Federal Regulations, 2010
The goal of the research was to compare the relationship of whole body averaged specific absorption rate (SAR) and specific absorption (SA) to determine whether dose rate or dose was the better predictor of biological effects. Sperm positive Long-Evans fe...
These studies clearly indicate the thermoregulatory capacity of the dog to withstand exposure to high microwave fields at specific absorption rates (SAR) of 3.7 and 6.1 W/kg. It appears that adequate thermoregulation takes place at an SAR of 3.7 W/kg but ...
Highlights Background Frequently Asked Questions(FAQ) Cellular Telephone Specific Absorption Rate (SAR) OET RF Safety Bulletins, Fact Sheets, Guides and Reports Software FDA...
Science.gov Websites
OBJECT: Parallel transmission facilitates a relatively direct control of the RF transmit field. This is usually applied to improve the RF field homogeneity but might also allow a reduction of the specific absorption rate (SAR) to increase freedom in sequence design for high-field MRI. However, predicting the local ...
PubMed
Full-size models of a man and a rhesus monkey were exposed to radiofrequency (RF) radiation at 225 MHz. The model of man was also exposed to 2,000 MHz. Specific absorption rates (SARs) were measured in partial-body sections, such as the arms, legs, etc., using gradient-layer calorimeters. Also, front-surface thermographic images were ...
A frequent problem in the radiofrequency (RF) irradiation of experimental animals in health effects studies is the temporal variation of the specific absorption rate (SAR) with animal movement. An RF power controller which regulates the energy absorption rate has been designed fo...
To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels from the basic restrictions on the induced whole-body-averaged specific absorption rate (SAR(wb)) and the peak 10 g spatial-averaged ...
playing along each. Peak and average SAR. For each RF design, SAR(r) in a 2-D slice of the head model R MeanSAR SVD LSQR CGLS Figure 1: (a) 8-Channel Coil (b) Head Model Figure 3: Relative SAR and Computer Science, MIT, Cambridge, MA, United States, 2 A. A. Martinos Center for Biomedical Imaging
E-print Network
This report results from a contract tasking Institute of non- ionizing radiation as follows: The main part of the proposed work will be designed to verify the parallel C code with the published results obtained by the Fortran code. To carry out trustful v...
... exposure to 0.4 W/kg for whole-body specific absorption rate (SAR ... by thermoelastic expansion of brain tissue and a propagating acoustic wave ...
DTIC Science & Technology
The major objective of this project has been to determine whether radiofrequency radiation (RFR), at power densities and specific absorption rate (SAR) values which can result in temperature increases in the exposure medium, can affect the extent of chemi...
The purpose of this study was to determine the threshold specific absorption rate (SAR) during exposure to 2450 MHz continuous wave (CW) microwaves that affected thermoregulatory behavior in mice. A plexiglas shuttle box was placed inside a waveguide impo...
The purpose of this study was to determine the threshold specific absorption rate (SAR) during exposure to 2450 MHz continuous wave (CW) microwaves that affected thermoregulatory behavior in mice. A plexiglas shuttle box was placed inside a waveguide imposed with a temperature gr...
... 13.56MHz) at a specific absorption rate (SAR) of 2.5 W/kg (RF) with warm water immersion (40 C) (WW) and an insulated mummy-type rewarming ...
The goal of the research was to compare the relationship of whole body averaged specific absorption rate (SAR) and specific absorption (SA) to determine whether dose rate or dose was the better predictor of biological effects. Sperm positive Long-Evans female rats were exposed to...
The purpose of this paper is to calculate the specific absorption rate (SAR) reduction in a muscle cube with metamaterial attachment. The finite-difference time-domain (FDTD) method has been used to evaluate the SAR in a realistic anatomically based model of the muscle cube. In this paper, we have designed the ...
A method of controlling the specific absorption rate (SAR) distribution in radiofrequency hyperthermia is proposed. The superposition of the current density associated with capacitively coupled electrodes and that associated with H-field coupled inductive aperture-type applicators modifies the actual current distribution in the heating ...
Finite-difference time-domain (FDTD) calculations of whole-body averaged specific energy absorption rate (SAR) have been performed from 100 MHz to 3 GHz at the basic 2 mm resolution of the voxel (volume pixel) model NORMAN without any rescaling to larger cell sizes. The reduction in the voxel size from previous work allows ...
NASA Astrophysics Data System (ADS)
The specific absorption rate (SAR) is an important safety criterion, limiting many MR protocols with respect to the achievable contrast and scan duration. Parallel transmission enables control of the radiofrequency field in space and time and hence allows for SAR management. However, a trade-off exists between ...
The supervision of local specific absorption rate (SAR) in parallel transmission applications in MRI is crucial. One existing approach is to use electromagnetic simulations including human anatomical models and to precalculate the electric field distributions of each individual channel. These can be superposed later with respect to ...
excitations via regional cancellation. Here, we study average and local SAR in a head model at 7 Tesla for 2D model to obtain whole-head and maximum local 1- gram & 10-gram averaged SAR. Here, the effect CENTER FOR BIOMEDICAL IMAGING, MGH, CHARLESTOWN, MA, UNITED STATES, 3 HARVARD-MIT DIVISION OF HEALTH
The research program was initiated to determine both the specific absorption rate (SAR) and the behavioral and physiological consequences of chronic CW microwave radiation exposure at 2450 MHz in the laboratory rat. Whole-body average and local SARs at discrete sites within the b...
The Dewar-flask calorimetric method of determining SARs, as described by Blackman and Black and Allen and Hurt requires the use of two animal cadavers for each SAR determination. One cadaver is exposed to electromagnetic(EM) radiation and its average body...
A finite-difference time-domain technique was used to calculate the specific absorption rate (SAR) at various sites in a heterogeneous block model of man. The block model represented a close approximation to a full-scale heterogeneous phantom model. Both ...
A finite-difference time-domain technique was used to calculate the specific absorption rate (SAR) at various sites in a heterogeneous block model of man. he block model represented a close approximation to a full-scale heterogeneous phantom model. oth models were comprised of a ...
The aim of this paper is to evaluate the specific absorption rate (SAR) reduction in a muscle cube by using metamaterial. To evaluate the SAR in a realistic anatomically based model of the muscle cube, the finite-difference time-domain (FDTD) method has been utilized. The effective medium parameter is obtained to ...
Magnetic resonance imaging (MRI) on patients with implanted deep brain stimulators (DBSs) can be hazardous because of the antenna-effect of leads exposed to the incident radio-frequency field. This study evaluated electromagnetic field and specific absorption rate (SAR) changes as a function of lead resistivity on an anatomically ...
PubMed Central
The possibility of using thermocouples for the artifact-free measurements of skin temperature during millimeter wave exposure was studied. The distributions of the specific absorption rate (SAR) in the human skin were calculated for different orientations of the thermocouple relative to the E-field of exposure. It was shown that, at ...
Radio-frequency heated magnetic nanoaparticle suspensions have potential applications in cancer hyperthermia. To optimize these systems for hyperthermia applications it is important to be able to predict how their heat generation or specific absorption rate (SAR) is influenced by various factors, including nanoparticle coating or ...
As part of a study of far-field microwave dosimetry in the human body, local and average specific absorption rates (SARs) in a homogeneous full-size muscle-equivalent upper-body man model were compared with measurements in an upper-body man model also con...
This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including ...
This study investigates occupational exposure to electromagnetic fields in front of a multi-band base station antenna for mobile communications at 900, 1800, and 2100?MHz. Finite-difference time-domain method was used to first validate the antenna model against measurement results published in the literature and then investigate the specific absorption ...
The promise of increased signal-to-noise ratio and spatial/spectral resolution continues to drive MR technology toward higher magnetic field strengths. SAR management and B1 inhomogeneity correction become critical issues at the high frequencies associated with high field MR. In recent years, multiple coil excitation techniques have been recognized as potentially powerful ...
To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels from the basic restrictions on the induced whole-body-averaged specific absorption rate (SARwb) and the peak 10 g spatial-averaged SAR ...
An extensive study on specific absorption rate (SAR) covering 720 simulations and 15 voxel models (18-105 kg) has been performed by applying the parallel finite-difference time-domain method. High-resolution whole-body models have been irradiated with plane waves from 300 MHz to 5 GHz by applying various incoming directions and ...
Localized and averaged specific absorption rates (SARs) were obtained in a full-size muscle-equivalent human model exposed to near-field 29.9-MHz irradiation at an outdoor facility. The model was positioned erect on a metallic groundplane 1.22 m (4 ft) from the base of a 10.8-m (35 ft) whip antenna with an input power of 1.0 kW. For ...
Energy Citations Database
A change in the posture of the human body can significantly affect the way in which it absorbs radiofrequency electromagnetic radiation. To study this, an anatomically realistic model of the body has been modified to develop new voxel models in postures other than the standard standing position with arms to the side. These postures were sitting, arms stretched out horizontally to the side and ...
Deionized water is commonly used to couple microwave applicators to the patient surface in the administration of local hyperthermia. Profiles of the specific absorption rate (SAR) at 1-cm depth show that deionized water coupling significantly distorts the SAR distributions of the Clini-Therm 915-MHz 10 X 10 and 15 ...
In the present study, we investigate the relationship between the mass-averaged specific absorption rate (SAR) and temperature elevation in anatomically based Japanese head models due to the dipole antenna. A homogeneous cubical model is also used as a basis for the investigation. The frequency region considered is from 1 to 6 GHz. We ...
This paper reports on the electromagnetic effects on the biological tissue surrounding a transcutaneous transformer for an artificial anal sphincter. The coupling coils and human tissues, including the skin, fat, muscle, liver, and blood, were considered. Specific absorption rate (SAR) and current density were analyzed by a ...
The purpose of this work was to investigate the dependence of whole-body averaged specific energy absorption rate (SAR), calculated using the finite-difference time-domain (FDTD) method, on the width of the free space region between a numerical phantom and the perfectly matched layer (pml) absorbing boundary. Results show that an ...
This article describes the analysis of electromagnetic energy absorption properties of models of the human eye with common visual disorders. The investigation addresses two types of visual disorders, namely hyperopia (or farsightedness) and myopia (or nearsightedness). Calculations were carried out using plane multilayered method with common wireless communication frequencies ...
ABSTRACT: The suitability of magnetic nanoparticles (MNPs) to act as heat nano-sources by application of an alternating magnetic field has recently been studied due to their promising applications in biomedicine. The understanding of the magnetic relaxation mechanism in biocompatible nanoparticle systems is crucial in order to optimize the magnetic properties and maximize the specific ...
A new and fast numerical method is presented to assess the whole-body averaged specific absorption rate (SAR) in a human body model in a realistic electromagnetic environment. The method requires a minimum set of initial numerical simulations with a 3D electromagnetic solver. From the initial simulation results, the ...
Specific energy absorption rate (SAR) values have been calculated in a 10 year old sitting voxel model from exposure to electromagnetic fields at 2.4 and 5 GHz, frequencies commonly used by Wi-Fi devices. Both plane-wave exposure of the model and irradiation from antennas in the near field were investigated for a variety of exposure ...
The effect of dielectric loading on the cell layer specific absorption rate (SAR) within a T-75 culture flask being irradiated within a transverse electromagnetic (TEM) cell was studied both experimentally and numerically. Direct thermal measurements of a T-75 containing 40 mL of culture medium and resting upon a 3-mm-thick slab of ...
In this work, the effect of antenna element loading on the localized specific absorption rate (SAR) has been analyzed for base station antennas. The analysis was conducted in order to determine whether localized SAR measurements of large multi-element base station antennas can be conducted using standardized ...
The high frequency of the radiofrequency (RF) fields used in high field magnetic resonance imaging (MRI) results in electromagnetic field variations that can cause local regions to have a large specific absorption rate (SAR) and/or a low excitation. In this study, we evaluated the use of a B1 shimming technique which can simultaneously ...
MRI in catheterized patients is considered unsafe due to the potential for focal heating. This concern arises from the continuous metallic braid that is incorporated into catheters to provide their desired physical properties. The potential for catheter heating during MR scanning was assessed in an in vitro model simulating a patient undergoing a neurovascular procedure in which MR scans of the ...
An enhancement of the specific absorption rate (SAR) inside a lossy dielectric object has been investigated theoretically based on a slab of left-handed medium (LHM). In order to make an accurate analysis of SAR distribution, a proper Green's function involved in the LHM slab is proposed, from which an integral ...
This paper reports on the specific absorption rate (SAR) and the current density analysis of biological tissue surrounding an air-core type of transcutaneous transformer for an artificial heart. The electromagnetic field in the biological tissue surrounding the transformer was analyzed by the transmission-line modeling method, and the ...
We propose a new application of voltage gradient measurements to determine specific absorption rate (SAR) at low frequencies where quasi-static electromagnetic conditions apply. This method, which we call the voltage gradient method, relies on direct measurement of the voltage field rather than measurement of the electric field or ...
An enhancement of the specific absorption rate (SAR) inside a lossy dielectric object has been investigated theoretically based on a slab of left-handed medium (LHM). In order to make an accurate analysis of SAR distribution, a proper Green�s function involved in the LHM slab is proposed, from which an integral ...
Multi-transmit coils are increasingly being employed in high-field magnetic resonance imaging, along with a growing interest in multi-transmit body coils. However, they can lead to an increase in whole-body and local specific absorption rate (SAR) compared to conventional body coils excited in circular polarization for the same total ...
Male CBA/J mice were administered heat loads of 0-28 J. per g at specific absorption rates (SARs) of either 47 or 93 W. per kg by exposure to 2,450-MHz microwave radiation at an ambient temperature of 30 C while evaporative heat loss (EHL) was continuously monitored with dew-poin...
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 ...
Determining the low-temperature dependence of the specific absorption rate (SAR) of magnetic nanoparticles under alternating magnetic fields with amplitudes and frequencies similar to those used in applications such as magnetic fluid hyperthermia, becomes essential when theoretical expressions fail to extrapolate the behavior of ...
Numerous studies have attempted to address the question of the RF energy absorption difference between children and adults using computational methods. They have assumed the same dielectric parameters for child and adult head models in SAR calculations. This has been criticized by many researchers who have stated that child organs are not fully developed, ...
The effects of sweat gland ducts (SGD) on specific absorption rate and temperatures during millimeter wave irradiation of skin were investigated with a high resolution finite differences time domain model consisting of a 30 ?m stratum corneum (SC), a 350 ?m epidermis, 1000 ?m dermis and five SGD (60 ?m radius, 300 ?m height, 370 ?m separation). The source ...
The interaction of radiofrequency (RF) and microwave (MW) electromagnetic radiation with biological tissues is of increasing importance from the standpoint of health and safety. From considerable literature devoted to the study of RF and MW bioeffects based primarily on animal experimentation it has been determined that bioeffects are correlated with mass-normalized rates of ...
Electromagnetic (EM) absorption of the human body for far-field exposure at the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference level has two peaks in the resonance frequency and GHz regions. Dominant factors influencing whole-body average specific absorption rate (SAR) in these two ...
The dosimetry of exposure to radiofrequency (RF) electromagnetic (EM) fields of mobile phones is generally based on the specific absorption rate (SAR, W kg-1), which is the electromagnetic energy absorbed in the tissues per unit mass and time. In this study, numerical methods and modelling were used to estimate the effect of a passive, ...
A new human head phantom has been proposed by CENELEC/IEEE, based on a large scale anthropometric survey. This phantom is compared to a homogeneous Generic Head Phantom and three high resolution anatomical head models with respect to specific absorption rate (SAR) assessment. The head phantoms are exposed to the radiation of a generic ...
We report on the magnetic and hyperthermia properties of 5.5 nm in diameter iron nanoparticles synthesized by organometallic chemistry, which display the bulk magnetization. Quantitative analysis of alternative susceptibility measurements allows the determination of the effective anisotropy Keff=1.3�105 J m-3. Hyperthermia measurements are performed at a magnetic field up to 66 mT and at ...
In this paper the design of a multiband compact antenna for the integration into the new multi function mobile phones is presented. The antenna is matched to operate at GSM 920 MHz, WI-Fi 2.4 GHz and HiperLan 5.1 GHz standards with low SAR levels. Return loss coefficient and radiation pattern of this antenna are computed in free space as well as in the presence of head. The ...
The finite difference time domain method is used to calculate the specific absorption rate (SAR) due to a butterfly surface coil in a realistic tissue model of the leg. The resulting temperature distribution and temperature changes are found using a finite difference solution to the bioheat transfer equation. Reasonable agreement is ...
The University of Florida (UF) Series B paediatric phantoms were developed for medical and radiation protection photon dosimetry. The series includes a 9 month male, a 4 year female, an 8 year female, an 11 year male and a 14 year male. In this paper they have been adapted to calculate the whole-body-averaged specific energy absorption rate ...
This paper deals with the variability of body models used in numerical dosimetry studies. Six adult anthropomorphic voxel models have been collected and used to build 5-, 8- and 12-year-old children using a morphing method respecting anatomical parameters. Finite-difference time-domain calculations of a specific absorption rate (SAR) ...
We have evaluated the specific absorption rate (SAR) in the eye induced by the perpendicular incidence of 30 GHz uniform plane millimeter wave (MMW). An anatomically based 0.25 mm voxel model of the eye with 10 types of tissue is constructed. Debye�s dispersion equation is used to derive the dielectric properties of the eye tissues ...
This paper presents the computational electromagnetic dosimetry inside an anatomically based pregnant woman models exposed to electromagnetic wave during magnetic resonance imaging. The two types of pregnant woman models corresponding to early gestation and 26 weeks gestation were used for this study. The specific absorption rate (SAR) ...
From an anatomically-based Japanese model of three-year-old child with a resolution of 1 mm, we developed a nine-month Japanese infant with linear shrink. With these models, we calculated the whole-body average specific absorption rate (WBA-SAR) for plane-wave exposure from 0.1 to 6 GHz. A conservative estimate of the ...
Basic restrictions for protecting against localized tissue heating induced from exposure to radiofrequency (RF) fields are typically specified as the specific energy absorption rate (SAR), which is mass averaged in recognition of the thermal diffusion properties of tissues. This article seeks to determine the most appropriate averaging ...
This study analyzes the exposure of the human torso to electromagnetic fields caused by wireless body-mounted or handheld devices. Because of the frequency and distance ranges from 30-5800 MHz and 10 to 200 mm, respectively, both near-field and far-field effects are considered. A generic body model and simulations of anatomical models are used to evaluate the worst case tissue composition with ...
For quality assurance of hyperthermia treatment planning systems, quantitative validation of the electromagnetic model of an applicator is essential. The objective of this study was to validate a finite-difference time-domain (FDTD) model implementation of the Lucite cone applicator (LCA) for superficial hyperthermia. The validation involved (i) the assessment of the match between the predicted ...
In order to determine the effects of microwave radiation on the testis, it is necessary to express the physical insult in animal studies in a way that can be replicated elsewhere and ultimately used as a basis for extrapolation to man. However, there is conflict--especially in chronic experiments--between the desire for precise dosimetry and the need to minimise alteration of the normal ...
If an electromagnetic field is incident normally onto a perfectly conducting ground plane, the field is reflected back into the domain. This produces a standing wave above the ground plane. If a person is present within the domain, absorption of the field in the body may cause problems regarding compliance with electromagnetic guidelines. To investigate this, the whole-body ...
Most epidemiological studies investigating health effects of mobile telephone use have been criticised for poor quality of exposure assessment. Most used questionnaires which have limited precision to assess exposure. Clearly more relevant and direct methods of exposure assessment are needed. We describe the calibration of hardware modified phones (HMPs) for exposure assessment and dosimetry and ...
This study sought to clarify the effects of exposure to electromagnetic waves (EMW) used in cellular phones on learning and memory processes. Sprague-Dawley rats were exposed for either 1 h daily for 4 days or for 4 weeks to a pulsed 1439 MHz time division multiple access (TDMA) field in a carousel type exposure system. At the brain, average specific absorption ...
Finite-difference time-domain (FDTD) calculations have been performed to investigate the frequency dependence of the specific energy absorption rate (SAR) in a seated voxel model of the human body. The seated model was derived from NORMAN (NORmalized MAN), an anatomically realistic voxel phantom in the standing posture with arms to the ...
This study investigated the relationship between the specific absorption rate and temperature elevation in an anatomically-based model named NORMAN for exposure to radio-frequency far fields in the ICNIRP guidelines (1998 Health Phys. 74 494-522). The finite-difference time-domain method is used for analyzing the electromagnetic ...
Of the biological effects of human exposure to radiofrequency and microwave radiation, the best-established are those due to elevation of tissue temperature. To prevent harmful levels of heating, restrictions have been proposed on the specific absorption rate (SAR). However, the relationship between SAR and ...
Dosimetric measurements were made in a muscle-equivalent model of an adult rhesus monkey subjected to far-field irradiation at 1.29 GHz. Profiles of microwave-induced heating in the model were obtained at eight locations, and a gradient-layer whole-body calorimeter was used to measure total absorbed energy. Average specific absorption rate ...
Most of the recently revised safety standards worldwide are set in terms of internal rates of electromagnetic energy deposition (specific absorption rates or SAR) at radio frequencies (RF) and microwave frequencies, and of induced electric fields or current densities at lower frequencies up to 10 MHz. Numerical ...
Virtually continual exposure to 970-MHz microwaves in circularly-polarized waveguides was used to elicit fetal responses in Sprague-Dawley rats during gestation. wo hundred fifty rats were exposed to microwave radiation at whole-body averaged specific absorption rates (SAR) of 0....
The purpose of this study was to compare the rewarming effectiveness of a radio frequency coil (13.56MHz) at a specific absorption rate (SAR) of 2.5 W/kg (RF) with warm water immersion (40 C) (WW) and an insulated mummy-type rewarming sack (TS). Four male...
Colonic and tail skin temperature of the unrestrained Fischer rat were measured immediately after a 90 min exposure to 600 MHz radiofrequency radiation in a waveguide-type system. Ambient temperature (Ta) was maintained at either 20, 28, or 35 C. The specific absorption rate (SAR...
Groups of time-bred pregnant mice were irradiated with 2450-MHz microwaves at an incident power density of 28 mW/sq. cm. for 100 min daily from day 6 to day 18 of pregnancy. The average specific absorption rate (SAR) was 16.5 W/kg. Two experiments were performed under these condi...
This article is related to the proposed hypothesis and experimental data regarding the ability of defined polar polymer compound (MRET polymer) applied to RF phones to increase the dielectric permittivity of water based solutions and to reduce the SAR (Specific Absorption Rate) values inside the "phantom head" filled with the jelly ...
The electric properties (EPs) of biological tissues, i.e., the electric conductivity and permittivity, can provide important diagnostic information in cancer detection and characterization. The conductivity also plays an important role in specific absorption rate (SAR) calculation, which is a major concern in high-field Magnetic ...
This paper reports on the current density and specific absorption rate (SAR) analysis of biological tissue surrounding an air-core transcutaneous transformer for an artificial heart. The electromagnetic field in the biological tissue is analyzed by the transmission line modeling method, and the current density and ...
A worldwide epidemiological study called 'INTERPHONE' has been conducted to estimate the hypothetical relationship between brain tumors and mobile phone use. In this study, we proposed a method to estimate 3D distribution of the specific absorption rate (SAR) in the human head due to mobile phone use to provide the exposure gradient ...
PurposeTo investigate the behavior of whole-head and local SAR as a function of trajectory acceleration factor and target excitation pattern due to the parallel transmission (pTX) of spatially-tailored excitations at 7T.Materials and MethodsFDTD simulations in a multi-tissue head model are used to obtain B+1 and electric field maps ...
Parallel excitation using multiple transmit channels has emerged as an effective method to shorten multidimensional spatially selective radiofrequency (RF) pulses, which have a number of important applications, including B1 field inhomogeneity correction in high-field MRI. The specific absorption rate (SAR) is a primary concern in ...
Numerical simulations of specific absorption rate (SAR) and temperature changes in a 26-week pregnant woman model within typical birdcage body coils as used in 1.5 T and 3 T MRI scanners are described. Spatial distributions of SAR and the resulting spatial and temporal changes in temperature are determined using a ...
Due to the difficulty of the specific absorption rate (SAR) measurement in an actual human body for electromagnetic radio-frequency (RF) exposure, in various compliance assessment procedures the incident electric field or power density is being used as a reference level, which should never yield a larger whole-body average ...
Electric fields (E-fields) induced within a phantom head from exposure to three different advanced mobile phone system (AMPS) hand-held telephones were measured using an implantable E-field probe. Measurements were taken in the eye nearest the phone and along a lateral scan through the brain from its centre to the side nearest the phone. During measurement, the phones were positioned alongside the ...
Electric fields (E-fields) induced within a phantom head from exposure to three different advanced mobile phone system (AMPS) hand-held telephones were measured using an implantable E-Field probe. Measurements were taken in the eye nearest the phone and along a lateral scan through the brain from its center to the side nearest the phone. During measurement, the phones were positioned alongside the ...
Finite-difference time-domain (FDTD) calculations have been performed of the whole-body averaged specific energy absorption rate (SAR) in a female voxel model, NAOMI, under isolated and grounded conditions from 10 MHz to 3 GHz. The 2 mm resolution voxel model, NAOMI, was scaled to a height of 1.63 m and a mass of 60 kg, the dimensions ...
Rats were irradiated with circularly polarized, 2,450-MHz pulsed microwaves (2-microseconds pulses, 500 pulses per second (pps)) for 45 min in the cylindrical waveguide system of Guy et al. Immediately after exposure, sodium-dependent high-affinity choline uptake, an indicator of cholinergic activity in neural tissue, was measured in the striatum, frontal cortex, hippocampus, and hypothalamus. The ...
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) . ...
High resolution SAR images of a target scene at near video rates can be produced by using overlapped, but nevertheless, full-size synthetic apertures. The SAR images, which respectively correspond to the apertures, can be analyzed in sequence to permit detection of movement in the target scene.
DOE Information Bridge
The body area network (BAN) has attracted attention because of its potential for high-grade wireless communication technology and its safety and high durability. Also, human area transmission of a BAN propagating at an ultra-wide band (UWB) has been demonstrated recently. When considering the efficiency of electromagnetic (EM) propagation inside the human body for BAN and hyperthermia treatment ...
Calculations of specific energy absorption rate (SAR) have been performed on the rescaled NORMAN 7-y-old voxel model and the Electronics and Telecommunications Research Institute (ETRI) child 7-y-old voxel model in the standing arms down, arms up and sitting postures. These calculations were for plane-wave exposure under isolated and ...
This study investigated the effects of microwave radiation on the PVN of the hypothalamus, extracted from rat brains. Expression of c-Fos was used to study the pattern of cellular activation in rats exposed once or repeatedly (ten times in 2�weeks) to 2.45�GHz radiation in a GTEM cell. The power intensities used were 3 and 12�W and the Finite Difference Time Domain calculation was used to ...
In a case�control study in Japan of brain tumours in relation to mobile phone use, we used a novel approach for estimating the specific absorption rate (SAR) inside the tumour, taking account of spatial relationships between tumour localisation and intracranial radiofrequency distribution. Personal interviews were carried out with 88 ...
In a case-control study in Japan of brain tumours in relation to mobile phone use, we used a novel approach for estimating the specific absorption rate (SAR) inside the tumour, taking account of spatial relationships between tumour localisation and intracranial radiofrequency distribution. Personal interviews were carried out with 88 ...
Rapid increase in the use of numerical techniques to predict current density or specific absorption rate (SAR) in sophisticated three dimensional anatomical computer models of man and animals has resulted in the need to understand how numerical solutions of the complex electrodynamics equations match with empirical measurements. This ...
The near field finite-difference time-domain method was used to calculate the current and specific absorption rate (SAR) distributions in an inhomogeneous model of a human heat exposed to the electromagnetic waves irradiated from a cellular phone. The human head was simulated by a model of 57 263 block cells with inhomogeneous ...
The purpose of this study was to assess the ability of the rat to reduce metabolic rate when exposed to deep-penetrating radio-frequency (RF) radiation. Male Sprague-Dawley rats were maintained at an ambient temperature (Ta) of 10 degrees C and exposed to 600-MHz radiation while metabolic rate (MR) was measured by indirect calorimetry. RF radiation ...
Parallel excitation holds strong promises to mitigate the impact of large transmit B(1) (B(1)(+)) distortion at very high magnetic field. Accelerated RF pulses, however, inherently tend to require larger values in RF peak power which may result in substantial increase in Specific Absorption Rate (SAR) in tissues, which is a constant ...
Parallel excitation holds strong promises to mitigate the impact of large transmit B1 (B1+) distortion at very high magnetic field. Accelerated RF pulses, however, inherently tend to require larger values in RF peak power which may result in substantial increase in Specific Absorption Rate (SAR) in tissues, which is a constant concern ...
Parallel excitation holds strong promises to mitigate the impact of large transmit B1 (B+1) distortion at very high magnetic field. Accelerated RF pulses, however, inherently tend to require larger values in RF peak power which may result in substantial increase in Specific Absorption Rate (SAR) in tissues, which is a constant concern ...
As the use of radiofrequency (RF) electromagnetic (EM) fields has increased along with increased use of wireless communication, the possible related health risks have also been widely discussed. One safety aspect is the interaction of medical implants and RF devices like mobile phones. In the literature, effects on active implants like pacemakers have been discussed but the studies of passive ...
This paper discusses a recent proposal for definitions of acoustic dose and acoustic dose-rate. Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Its time-derivative, acoustic dose-rate, Qm, in W kg?1 is central to the prediction of both ...
The rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in possible carcinogenic effects of radio frequency (RF). Because exposure to RF from phones is localized, if a risk exists it is likely to be greatest for tumours in regions with greatest energy absorption. The objective of the current paper was to characterize the spatial ...
In this article, personal electromagnetic field measurements are converted into whole-body specific absorption rates for exposure of the general public. Whole-body SAR values calculated from personal exposure meter data are compared for different human spheroid phantoms: the highest SAR values (at 950 MHz) are ...
Anatomic variability in the deposition of radiofrequency electromagnetic energy in mammals has been well documented. A recent study reported specific absorption rate (SAR) hotspots in the brain, rectum and tail of rat carcasses exposed to 360- and to 2450-MHz microwave radiation. Regions of intense energy ...
The aim of this work was to investigate the potential effect of sweat gland ducts (SGD) on specific absorption rate (SAR) and temperature distributions during mm-wave irradiation. High resolution electromagnetic and bio-heat transfer models of human skin with SGD were developed using a commercially available simulation software package ...
During an MR procedure, the patient absorbs a portion of the transmitted RF energy, which may result in tissue heating and other adverse effects, such as alterations in visual, auditory and neural functions. The Specific Absorption Rate (SAR), in W/kg, is the RF power absorbed per unit mass of tissue and is one of the most important ...
This is the first of two articles addressing the most appropriate crossover frequency at which incident power flux density (S(inc)) replaces the spatial peak value of the specific energy absorption rate (SAR) averaged over 1 or 10 g (i.e., peak 1 or 10 g SAR) as the basic restriction for protecting against ...
Due to current computer limitations, specific absorption rate (SAR) distributions in regional hyperthermia treatment planning (HTP) are limited to centimetre resolution. However, since patient anatomy is highly structured on a millimetre scale, millimetre-resolution SAR modelling is required. A method called ...
A head exposure setup for efficient and precisely defined exposure of human subjects equipped with a near-infrared imaging (NIRI) sensor is presented. In a partially shielded anechoic chamber the subjects were exposed to Universal Mobile Telecommunications System (UMTS)-like electromagnetic fields (EMF) by using a patch antenna at a distance of 4?cm from the head. The non-contact design of the ...
Purpose: To experimentally verify the feasibility of focused heating in the neck region by an array of two rings of six electromagnetic antennas. We also measured the dynamic specific absorption rate (SAR) steering possibilities of this setup and compared these SAR patterns to simulations. Methods and Materials: ...
The interpretation of the effects in biological systems exposed to electromagnetic (EM) fields requires knowledge of the internal fields and absorbed energy. The quantification of the specific absorption rate (SAR) is called dosimetry. The SAR given in units of watts per kilogram is a complex function of the source ...
Calorimetric measurements were performed to determine the average specific absorption rates (SAR) resulting from MRI head examinations. The data were compared with average head coil SAR estimates displayed by the MR scanner in order to refine the imaging protocols used in imaging patients with implanted deep brain ...
The heating ability of mineral oil-based magnetic fluids with different magnetic particle concentrations is studied. The calorimetric measurements were carried out in an alternating magnetic field of 500 A � m-1 to 2500 A � m-1 amplitude and of 1500 kHz frequency. The revealed H n law-type dependence of the temperature increase rate, (d T/d t) t=0, on the amplitude of ...
The finite difference time domain (FDTD) method in combination with a well established frequency scaling method was used to calculate the internal fields and current densities induced in a simple model of a pregnant woman and her foetus, when exposed to hand-held metal detectors. The pregnant woman and foetus were modelled using a simple semi-heterogeneous model in 10 mm resolution, consisting of ...
There is uncertainty regarding the risk posed by magnetic resonance imaging (MRI) examinations to pregnant patients. The most frequently used methods, such as single-shot fast spin echo (ssFSE), often require operation at the specific absorption rate (SAR) limits imposed by safety guidelines. With the introduction of higher-field ...
Worldwide expansion of mobile phones and electromagnetic field (EMF) exposure has raised question of their possible biological effects on the brain and nervous system. Radiofrequency (RF) radiation might alter intracellular signaling pathways through changes in calcium (Ca(2+)) permeability across cell membranes. Changes in the expression of calcium binding proteins (CaBP) like calbindin D28-k ...
PurposeTo develop a scanner-independent dosimeter for measuring the average radio frequency (RF) power deposition and specific absorption rates (SAR) for human MRI exposure.Materials and MethodsA prototype dosimeter has a transducer with orthogonal conducting loops surrounding a small signal-generating MRI sample. The loops contain ...
It is important to accurately characterize the heating of tissues due to the radiofrequency energy applied during MRI. This has led to an increase in the use of numerical methods to predict specific energy absorption rate distributions for safety assurance in MRI. To ensure these methods are accurate for actual MRI coils, however, it is necessary to ...
The so-called carousel setup has been widely utilized for testing the hypotheses of adverse health effects on the central nervous system (CNS) due to mobile phone exposures in the frequency bands 800-900 MHz. The objectives of this article were to analyze the suitability of the setup for the upper mobile frequency range, i.e., 1.4-2 GHz, and to conduct a detailed experimental and numerical ...
A 3D subgridding technique is used to model the specific absorption rate (SAR) distribution in the isolated cochlea exposed to mobile phone radiation at 1750 MHz using the FDTD method. The cochlea is modeled using an increasing spatial resolutions of 1, 1/3, 1/5, and 1/7 mm. First simulations were performed at 1 mm spatial resolution. ...
In this paper, external electric field values that are derived from the largest peak average 10 g SAR (Specific Absorption Rate) results in a realistic human head model are compared with current IEEE and ICNIRP reference levels. The head is illuminated by a plane wave source at seven different frequencies ranging from 500 MHz to 2500 ...
Water-based ferrofluids of substituted ferrites Fe1-xMnxFe2O4 (0<=x<=1) have been prepared by the co-precipitation method and characterized. Particles are superparamagnetic with an average particle size of about 10-12 nm. The specific absorption rate (SAR) was measured by calorimetric measurement at a frequency of 300 kHz and a ...
This paper highlights the design criteria of a gigahertz transverse electromagnetic (GTEM) cell to be used for the evaluation of potential biological effects induced by radio frequency electromagnetic waves on animal cell cultures. In particular, the estimation of the electromagnetic power absorbed by the cell culture allows us to evaluate the scalar specific absorption ...
Both eyes of anesthetized cynomolgus monkeys (Macaca fascicularis) were irradiated with 2.45-GHz microwaves, either pulsed or continuous wave. In vivo corneal endothelial abnormalities were observed by specular microscopy and confirmed through histologic techniques after a 16- to 48-hour postexposure period. Pulsed microwaves with an average power density of 10 mW/cm2 (equivalent to a specific ...
A powerful finite-difference numerical technique was applied to the human radiofrequency dosimetry problem. The method possesses inherent advantages over the method of moments approach in that its implementation requires much less computer memory. Consequently, it has the capability to calculate specific absorption rates (SARs) at ...
Harmful effects of electromagnetic fields (EMF) on cognitive and behavioural features of humans and rodents have been controversially discussed and raised persistent concern about adverse effects of EMF on general brain functions. In the present study we applied radio-frequency (RF) signals of the Universal Mobile Telecommunications System (UMTS) to full brain exposed male Wistar rats in order to ...
Male Sprague-Dawley rats were maintained at an ambient temperature (Ta) of 10 C and exposed to 600-MHz radiofrequency (RF) radiation while metabolic rate (MR) was measured by indirect calorimetry. RF radiation exposures were made in a waveguide-type system which permitted the continuous control of specific absorption rate ...
Although heating rate is important for stimulating thermoregulatory reflexes, it is not known if the control system differentiates between total heat gain and rate of heat gain. Exposing animals to microwaves inside a waveguide permits continuous monitoring of whole-body heat absorption. Tail skin temperature of restrained mice was ...
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 ...
The effects of microwave irradiation at two different frequencies (1.28 and 5.62 GHz) on observing-behavior of rodents were investigated. During daily irradiation, eight male hooded rats performed on a two-lever task; depression of one lever produced one of two different tones and the other lever produced food when depressed in the presence of the appropriate tone. At 5.62 GHz, the ...
BackgroundWe have developed magnetic cationic liposomes (MCLs) that contained magnetic nanoparticles as heating mediator for applying them to local hyperthermia. The heating performance of the MCLs is significantly affected by the property of the incorporated magnetite nanoparticles. We estimated heating capacity of magnetite nanoparticles by measuring its specific absorption ...
The level and distribution of radiofrequency energy absorbed in a child's head during the use of a mobile phone compared to those in an adult head has been a controversial issue in recent years. It has been suggested that existing methods that are used to determine specific absorption rate (SAR) and assess compliance with exposure ...
Virtually continual exposure to970-MHz microwaves in circularly-polarized waveguides was used to elicit fetal responses in Sprague-Dawley rats during gestation. Two hundred fifty rats were exposed to microwave radiation at whole-body averaged specific absorption rates (SAR) of 0.07, 2.4, or 4.8 W/kg, or concurrently sham-irradiated for ...
Present day use of mobile phones is ubiquitous. This causes some concern for human health due to exposure to high-frequency electromagnetic fields (HFEMF) from mobile phones. Consequently, we have examined the effects of 2.45 GHz electromagnetic fields on bacterial mutations and the hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene mutations. Using the Ames test, bacteria were exposed to ...
The aim of this study is to examine the scale and significance of differences in peak specific energy absorption rate (SAR) in the brains of children and adults exposed to radiofrequency emissions from mobile phones. Estimates were obtained by method of multipole analysis of a three layered (scalp/cranium/brain) spherical head exposed ...
The eye is considered to be a critical organ when determining safety standards for radiofrequency radiation. With a detailed anatomy of the human eye and orbit inserted in a whole-head model, the specific absorption rates (SARs) and thermal effects were determined under exposure to a dipole antenna representing a mobile phone operating ...
In the last few years, significant developments have taken place in the field of Wireless Local Area Networks (WLAN), and the popularity of portable devices supporting Wireless Fidelity (Wi-Fi) is continuously growing. At the same time, the number of Active Implanted Medical Devices (AIMD) being placed in patients is widely increasing and among them, cochlear implants (CI) are becoming a common ...
L929 murine fibroblast cells were exposed to radiofrequency (RF) radiation from a time division multiple access wireless phone operating at 835 MHz frequency to determine the effect of RF-radiation energy emitted by wireless phones on ornithine decarboxylase (ODC) activity in cultured cells. Exposure was for 8 h to an average specific absorption rate ...
In the current international guidelines and standards with regard to human exposure to electromagnetic waves, the basic restriction is defined in terms of the whole-body average-specific absorption rate. The rationale for the guidelines is that the characteristic pattern of thermoregulatory response is observed for the whole-body average ...
Microwave radiation decreased specific camphor binding to a membrane fraction of rat epithelium but not to a Triton X-100 extract of this fraction. Inhibition of the ligand binding did not depend on the modulation frequency of the microwave field in the region 1-100 Hz and was not a linear function of specific absorption rate (SAR). ...
The environment is an important parameter when evaluating the exposure to radio-frequency electromagnetic fields. This study investigates numerically the variation on the whole-body and peak spatially averaged-specific absorption rate (SAR) in the heterogeneous virtual family male placed in front of a base station antenna in a ...
Realistic numerical models of human subjects and their surrounding environment represent the basic points of radiofrequency (RF) electromagnetic dosimetry. This also involves differentiating the human models in men and women, possibly with different body shapes and postures. In this context, the aims of this paper are, firstly, to propose a female dielectric anatomical model (fDAM) and, secondly, ...
The study compared bioeffects of continuous wave (CW) microwaves and short, extremely high power pulses (EHPP) at the same carrier frequency (9.3 GHz) and average power (1.25 W). The peak transmitted power for EHPP was 250 kW (0.5-micro s pulse width, 10 p.p.s.), producing the E field of 1.57 MV/m in the waveguide. A biological endpoint was the density of yeast cells, achieved after a 6 h growth ...
INTRODUCTION. The AirSAR instrument is in the process of ... 1 kHz repetition rates with low pixel read noise. ... data rate of 1 Gbps and on-off keyed modulation. ... data channel is validated by sending a pseudo ...
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The purpose of the study was to assess the effects of electrodes and leads on electromagnetic field and specific absorption rate (SAR) distributions during simultaneous electroencephalography (EEG) and 7-T MRI. Two different approaches were evaluated and compared to the case without electrodes: (a) the use of different EEG lead ...
This paper investigates the internal electric and magnetic field distribution and the specific absorption rate (SAR) values in a magnetic resonance imaging-based model of the inner hearing system exposed to 900 and 1800 MHz. The internal fields distributions were calculated using the Finite Integration Technique. The estimation of the ...
Six male New Zealand white rabbits were individually exposed to 600-MHz radiofrequency (RF) radiation for 90 min in a waveguide exposure system at an ambient temperature (Ta) of 20 or 30 C. Immediately after exposure, the rabbit was removed from the exposure chamber and its colonic and ear skin temperatures were quickly measured. The whole-body specific absorption ...
Magnetic resonance imaging (MRI) avoids risks of genetic damage but may be associated with excess heating of body tissues. To investigate the exposure to MRI radio-frequency (RF) electromagnetic fields (EMF), low-pass and high-pass birdcage coils were simulated and the whole-body pregnant woman model SILVY used to determine local and whole-body specific absorption ...
In electromagnetic dosimetry, anatomical human models are commonly obtained by segmentation of magnetic resonance imaging or computed tomography scans. In this paper, a human head model extracted from thermal infrared images is examined in terms of its applicability to specific absorption rate (SAR) calculations. Since thermal scans ...
This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in ...
A circulating water bath exposure system has been designed for in vitro radiofrequency radiation (RFR) exposure studies in the 915 to 2450 MHz range. A Styrofoam float, in which 10 T-25 plastic tissue culture flasks are embedded, is rotated at approximately 20 rpm in a Plexiglas water bath at a distance beneath a rectangular horn. The continuous circular rotation of the flasks is designed to ...
The increasing use of mobile communication devices, especially mobile phones by children, has triggered discussions on whether there is a larger radio frequency (RF) energy absorption in the heads of children compared to that of adults. The objective of this study was to clarify possible differences in RF energy absorption in the head region of children ...
The proportion of energy absorbed by the tail of a rat carcass was determined. Male (288 g - 457 g) and female (195 g - 249 g) Sprague-Dawley rat carcasses were exposed to far-field, continuous-wave radiofrequency radiation (RFR). The carcasses were split into two mixed groups: one group was exposed to 700-MHz RFR; and the other, to 350-MHz RFR. Immediately after each exposure, the tail was ...
In this paper, personal electromagnetic field exposure of the general public due to 12 different radiofrequency sources is characterized. Twenty-eight different realistic exposure scenarios based upon time, environment, activity, and location have been defined and a relevant number of measurements were performed with a personal exposure meter. Indoor exposure in office environments can be higher ...
Isothermal (37 +/- 0.2 degrees C) exposure of glioma cells (LN71) for 2 h to 27 or 2450 MHz continuous-wave radiofrequency (RF) radiation in vitro modulated the rates of DNA and RNA synthesis 1, 3, and 5 days after exposure. The alterations indicate effects on cell proliferation and were not caused by RF-induced cell heating. The dose response for either frequency of the ...
Parallel excitation holds strong promises to mitigate the impact of large transmit B1 (B1+) distortion at very high magnetic field. Accelerated RF pulses, however, inherently tend to require larger values in RF peak power which may result in substantial increase in Specific Absorption ...
Biomedical applications of nanoparticle heating range in scale from molecular activation (i.e. molecular beacons, protein denaturation, lipid melting and drug release), cellular heating (i.e. nanophotolysis and membrane permeability control and rupture) to whole tumor heating (deep and superficial). This work will present a review on the heating of two classes of biologically compatible metallic ...
Cellular phones are used in the vicinity of the human head, resulting in localized exposure to this part of the body. To simulate exposure during cellular phone use, microwave energy absorption should be focused within the head region of laboratory animals. In this paper, we developed an exposure system using a figure-8 loop antenna to permit localized exposure of a rat head ...
MR imaging procedures, which have important diagnostic values, may result in specific absorption rates (SAR) which exceed recommended guidelines. To determine the thermal effect of a MR imaging scan at a relatively high SAR, 12 adult human volunteers were exposed for 20 min to a 4.0 W/kg whole-body MR imaging scan ...
The case for a DNA-damaging action produced by radiofrequency (RF) signals remains controversial despite extensive research. With the advent of the Universal Mobile Telecommunication System (UMTS) the number of RF-radiation-exposed individuals is likely to escalate. Since the epigenetic effects of RF radiation are poorly understood and since the potential modifications of repair efficiency after ...
There has been considerable discussion about the influence of high-frequency electromagnetic fields (HFEMF) on the human body. In particular, HFEMF used for mobile phones may be of great concern for human health. In order to investigate the properties of HFEMF, we have examined the effects of 2.45-GHz EMF on micronucleus (MN) formation in Chinese hamster ovary (CHO)-K1 cells. MN formation is ...
This paper presents new definitions for obtaining reproducible results in numerical phone dosimetry. Numerous numerical dosimetric studies have been published about the exposure of mobile phone users which concluded with conflicting results. However, many of these studies lack reproducibility due to shortcomings in the description of the phone positioning. The new approach was tested by two groups ...
This paper analyzes the radio frequencies (RF) exposure in the head tissues of children using a cellular handset or RF sources (a dipole and a generic handset) at 900, 1800, 2100 and 2400 MHz. Based on magnetic resonance imaging, child head models have been developed. The maximum specific absorption rate (SAR) over 10 g in the head has ...
