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McIntosh R.L.,Australian Center for Radiofrequency Bioeffects Research | Anderson V.,Swinburne University of Technology
Biophysical Reviews and Letters | Year: 2010

Accurate numerical calculation of the thermal profile in humans requires reliable estimates of the following five tissue properties: specific heat capacity (c), thermal conductivity (k), blood perfusion rates (m), metabolic heat production (A0), and density (ρ). A sixth property, water content (w, as a %), can also be used to estimate c and k. To date, researchers have used various and inconsistent estimates of these parameters, which hinders comparison of the corresponding results. In an effort to standardize and improve the accuracy of these parameters for future studies, we have documented over 150 key papers and books and developed a database of the six thermal properties listed above for 43 human tissues. For each tissue and each property the following were obtained: the average value, the number of source values, the minimum and maximum of source values, and the reference for each source value. A key premise for the development of the database was to only use references that provided the original measurements. This database is offered for use by the biological thermal modeling community to help improve the accuracy and consistency of thermal modeling results. © 2010 World Scientific Publishing Company.

Mcintosh R.L.,Australian Center for Radiofrequency Bioeffects Research | Anderson V.,Australian Center for Radiofrequency Bioeffects Research | Anderson V.,Swinburne University of Technology
Bioelectromagnetics | Year: 2011

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 mass (1, 3, 5, 7, or 10g) and averaging shape (cube or sphere). We also consider an alternative metric, volumetric energy absorption rate (VAR), which uses volume averaging (over 1, 3, 5, 7, and 10cm3; cube and sphere). The SAR and VAR averaging approaches were compared by considering which was a better predictor of tissue temperature rise (ΔT) induced by near- and far-field RF exposures (0.5-6GHz), calculated in a detailed human body model. For the exposure scenarios that we examined, VAR is better correlated with ΔT than SAR, though not at a statistically significant level for most of the metric types we studied. However, as VAR offers substantive advantages in ease of assessment we recommend this metric over SAR. Averaging over a cube or a sphere provides equivalent levels of correlation with ΔT, and so we recommend choosing the averaging shape on the basis of which is easier to assess. The optimal averaging volume is 10cm3 for VAR, and the optimal mass is 10g for SAR. The correlation between VAR or SAR and ΔT diminishes substantially at 6GHz, where incident power flux density may be a better exposure metric. © 2010 Wiley-Liss, Inc.

McIntosh R.L.,Australian Center for Radiofrequency Bioeffects Research | Anderson V.,Australian Center for Radiofrequency Bioeffects Research | Anderson V.,Swinburne University of Technology
Bioelectromagnetics | Year: 2010

This is the second of the two articles that present modeling data and reasoned arguments for specifying the appropriate crossover frequency at which incident power flux density (Sinc) replaces the peak 10 g averaged value of the specific energy absorption rate (SAR) as the designated basic restriction for protecting against radiofrequency electromagnetic heating effects in the 1-10 GHz range. In our first study, we compared the degree of correlation between these basic restrictions and the peak-induced tissue temperature rise (ΔT) for a representative range of population/exposure scenarios using simple multi-planar models exposed to plane wave conditions. In this complementary study, complex heterogeneous head models for an adult and 12-year-old child were analyzed at 1, 3, 6, 8, and 10 GHz for a variety of exposure conditions. The complex models indicate that peak DT is better correlated with peak 10 g SAR than Sinc at 1 and 3 GHz and with Sinc at 6-10 GHz, in contrast to the results from Part I. Considering the planar and complex body modeling results together, and given the equivocal indications of the two metrics in the 6-10 GHz range, we recommend that the breakpoint be set at 6 GHz. This choice is also based on other considerations such as ease of assessment. We also recommend that the limit level of S inc should be adjusted to provide a better match with 10 g SAR in the induced tissue temperature rise. © 2010 Wiley-Liss, Inc.

Loughran S.P.,Swinburne University of Technology | Loughran S.P.,Australian Center for Radiofrequency Bioeffects Research | Loughran S.P.,University of Zurich | McKenzie R.J.,Swinburne University of Technology | And 6 more authors.
Bioelectromagnetics | Year: 2012

Mobile phone exposure-related effects on the human electroencephalogram (EEG) have been shown during both waking and sleep states, albeit with slight differences in the frequency affected. This discrepancy, combined with studies that failed to find effects, has led many to conclude that no consistent effects exist. We hypothesised that these differences might partly be due to individual variability in response, and that mobile phone emissions may in fact have large but differential effects on human brain activity. Twenty volunteers from our previous study underwent an adaptation night followed by two experimental nights in which they were randomly exposed to two conditions (Active and Sham), followed by a full-night sleep episode. The EEG spectral power was increased in the sleep spindle frequency range in the first 30min of non-rapid eye movement (non-REM) sleep following Active exposure. This increase was more prominent in the participants that showed an increase in the original study. These results confirm previous findings of mobile phone-like emissions affecting the EEG during non-REM sleep. Importantly, this low-level effect was also shown to be sensitive to individual variability. Furthermore, this indicates that previous negative results are not strong evidence for a lack of an effect and, given the far-reaching implications of mobile phone research, we may need to rethink the interpretation of results and the manner in which research is conducted in this field. © 2011 Wiley Periodicals, Inc.

McIntosh R.L.,Australian Center for Radiofrequency Bioeffects Research | McIntosh R.L.,Swinburne University of Technology | Deppeler L.,Swinburne University of Technology | Oliva M.,Swinburne University of Technology | And 6 more authors.
Physics in Medicine and Biology | Year: 2010

In vivo studies involving radiofrequency (RF) exposure of rodents require detailed dosimetric analysis to enable correct interpretation of biological outcomes. Detailed anatomical models of mice - a female, a pregnant female, a male and a foetus - have been developed for analyses using finite difference numerical techniques. The mouse models, consisting of 49 tissues, will be made freely available to the research community. In this note, the pregnant mouse model, which included eight mature foetuses, was utilized specifically to consider (a) the RF dosimetry in a radial cavity exposure system operated at a frequency of 900 MHz and (b) a 900 MHz plane wave exposure. A comparison was made between the exposure of the mouse dam and the foetuses as specified by the specific energy absorption rate (SAR) and the resultant temperature change. In general, the SAR levels in the foetuses were determined to be slightly lower (around 14% lower than the average values of the dam) and the peak temperature increase was significantly lower (45%) than the values in the dam. © 2010 Institute of Physics and Engineering in Medicine.

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