Numerically simulated exposure of children and adults to pulsed gradient fields in MRI

PurposeTo determine exposure to gradient switching fields of adults and children in a magnetic resonance imaging (MRI) scanner by evaluating internal electric fields within realistic models of adult male, adult female, and child inside transverse and longitudinal gradient coils, and to compare these results with compliance guidelines. Materials and MethodsPatients inside x-, y-, and z-gradient coils were simulated using anatomically realistic models of adult male, adult female, and child. The induced electric fields were computed for 1 kHz sinusoidal current with a magnitude of 1 A in the gradient coils. Rheobase electric fields were then calculated and compared to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2004 and International Electrotechnical Commission (IEC) 2010 guidelines. The effect of the human body, coil type, and skin conductivity on the induced electric field was also investigated. ResultsThe internal electric fields are within the first level controlled operating mode of the guidelines and range from 2.7V m(-1) to 4.5V m(-1), except for the adult male inside the y-gradient coil (induced field reaches 5.4V m(-1)).The induced electric field is sensitive to the coil type (electric field in the skin of adult male: 4V m(-1), 4.6V m(-1), and 3.8V m(-1) for x-, y-, and z-gradient coils, respectively), the human body model (electric field in the skin inside y-gradient coil: 4.6V m(-1), 4.2V m(-1), and 3V m(-1) for adult male, adult female, and child, respectively), and the skin conductivity (electric field 2.35-4.29% higher for 0.1S m(-1) skin conductivity compared to 0.2S m(-1)). ConclusionThe y-gradient coil induced the largest fields in the patients. The highest levels of internal electric fields occurred for the adult male model. J. Magn. Reson. Imaging 2016;44:1360-1367

Resonant Cavity Perturbation: A Promising New Method for the Assessment of Total Body Water in Children

The accurate measurement of total body water (TBW) in children has important clinical and nutritional applications. Resonant cavity perturbation (RCP) is a new method for estimating TBW. This method measures the dielectric properties of the body which are related to body water. For RCP measurements, each subject lay supine on a bed inside a screened room which acts as a resonant cavity. A network analyser measures the frequencies of two low-order cavity resonances of the room, with electric-field vectors that were respectively vertical and horizontal, the resonant frequency shifts relative to the empty room are then derived. These frequency shifts correlates with TBW. The aims of this present study were to a) develop TBWRCP predictive equations for children using TBWdil as the criterion method, b) cross-validate the derived equations, c) determine precision of the TBWRCP method, and d) compare the criterion method TBWdil with three methods of estimating TBW: RCP, MFBIS and Anthropometry. Predictive equations, independent of sex, were developed with linear regression in a group of 36 children. The relationship between combined RCP frequency shifts and TBWdilution had an r2=0.90 and standard error of the estimate (SEE) =1.42kg. Multiple regression analysis, that included a term for body mass index, only had a small effect on r2=0.93 and SEE=1.25kg. In-vivo TBW precision for the vertical, horizontal and combined frequency modes ranged from 0.7 to 3.4%. Bland Altman analysis indicated close agreement between the criterion method TBWdil and the three other methods of TBW estimation. Mean differences were TBWRCP(2) = 0.01+/-1.34kg, TBWMFBIS = 0.45+/-1.35kg, TBWAnthropometry = 0.29+/-1.29kg. Currently the RCP method does not significantly improve the prediction of TBW compared to MFBIS and anthropometry in this initial study. However the derived equation was independent of sex and body size had only a small effect

Functional plant science and biotechnology

This chapter reviews the biological effects and the consequences for health that result from exposure to extremely low-frequency (ELF) fields and radiofrequency (RF) radiation - time-varying electromagnetic fields (EMFs) up to 300 GHz. The well-established effects of exposure to ELF frequencies result from the interaction of induced electric fields and currents with electrically excitable nerve and muscle tissue, whereas exposure to sufficiently intense RF radiation results in whole-body and/or localized tissue heating. The chapter reviews these effects and the effects of exposure to much lower EMF levels such as those encountered in the environment. The final section summarizes existing health-risk assessments and the current International Commission on Non-ionizing Radiation guidelines on exposure

Systematic review of wireless phone use and brain cancer and other head tumors

Repacholi MH, Lerchl A, Roosli M, et al. Systematic review of wireless phone use and brain cancer and other head tumors. Bioelectromagnetics. 2012;33(3):187-206.We conducted a systematic review of scientific studies to evaluate whether the use of wireless phones is linked to an increased incidence of the brain cancer glioma or other tumors of the head (meningioma, acoustic neuroma, and parotid gland), originating in the areas of the head that most absorb radiofrequency (RF) energy from wireless phones. Epidemiology and in vivo studies were evaluated according to an agreed protocol; quality criteria were used to evaluate the studies for narrative synthesis but not for meta-analyses or pooling of results. The epidemiology study results were heterogeneous, with sparse data on long-term use (=10 years). Meta-analyses of the epidemiology studies showed no statistically significant increase in risk (defined as P<0.05) for adult brain cancer or other head tumors from wireless phone use. Analyses of the in vivo oncogenicity, tumor promotion, and genotoxicity studies also showed no statistically significant relationship between exposure to RF fields and genotoxic damage to brain cells, or the incidence of brain cancers or other tumors of the head. Assessment of the review results using the Hill criteria did not support a causal relationship between wireless phone use and the incidence of adult cancers in the areas of the head that most absorb RF energy from the use of wireless phones. There are insufficient data to make any determinations about longer-term use (=10 years). Bioelectromagnetics 33:187206, 2012. (C) 2011 Wiley Periodicals, Inc