Paper on variations of absorption of electromagnetic power in the human body

Paper on variations of absorption of electromagnetic power in the human body accepted for publication in IOP Physics in Medicine and Biology.

The electromagnetic absorption cross-section (ACS) averaged over polarisation and angle-of incidence of 60 ungrounded adult subjects was measured at microwave frequencies of 1-12 GHz in a reverberation chamber. Average ACS is important in non-ionising dosimetry and exposure studies, and is closely related to the whole-body averaged specific absorption rate (WBSAR). The average ACS was measured with a statistical uncertainty of less than 3 % and high frequency resolution for individuals with a range of body shapes and sizes allowing the statistical distribution of WBSAR over a real population with individual internal and external morphologies to be determined for the first time.

This technique has made it possible for the first time to experimentally validate the variations in human exposure obtained from a small number of numerical phantoms against the variations in a real population of people.

The figure above shown the quantiles (0%, 5% , 25%, 50%, 75%, 95% and 100%) of the average ACS of the subjects measured compared to literature results obtained from simulations on specific numerical phanotms. The overall dispersion of measured average WBSAR of the sample of the UK population studied is consistent with the dispersion of simulated worst-case WBSAR across multiple numerical phantom families. These statistical results allow the calibration of human exposure assessments made with particular phantoms to a population with individual morphologies.

The measurements were performed as part of the High Intensity Radiated Field Synthetic Environment (HIRFSE) research project to quantify how people affect the electromagnetic field in enclosed spaces.

The full details are in the paper (Flintoft et al., 2014). The datasets from the paper are available in the resources section.

References

1. Flintoft, I.D., Robinson, M.P., Melia, G.C.R., Marvin, A.C. and Dawson, J.F., 2014. Average absorption cross-section of the human body measured at 1-12 GHz in a reverberant chamber: results of a human volunteer study. Physics in Medicine and Biology, 59(13), pp.3297–3317.
   

   The electromagnetic absorption cross-section (ACS) averaged over polarization and angle-of-incidence of 60 ungrounded adult subjects was measured at microwave frequencies of 1–12 GHz in a reverberation chamber. Average ACS is important in non-ionizing dosimetry and exposure studies, and is closely related to the whole-body averaged specific absorption rate (WBSAR). The average ACS was measured with a statistical uncertainty of less than 3% and high frequency resolution for individuals with a range of body shapes and sizes allowing the statistical distribution of WBSAR over a real population with individual internal and external morphologies to be determined. The average ACS of all subjects was found to vary from 0.15 to 0.4 m 2 ; for an individual subject it falls with frequency over 1–6 GHz, and then rises slowly over the 6–12 GHz range in which few other studies have been conducted. Average ACS and WBSAR are then used as a surrogate for worst-case ACS/WBSAR, in order to study their variability across a real population compared to literature results from simulations using numerical phantoms with a limited range of anatomies. Correlations with body morphological parameters such as height, mass and waist circumference have been investigated: the strongest correlation is with body surface area (BSA) at all frequencies above 1 GHz, however direct proportionality to BSA is not established until above 5 GHz. When the average ACS is normalized to the BSA, the resulting absorption efficiency shows a negative correlation with the estimated thickness of subcutaneous body fat. Surrogate models and statistical analysis of the measurement data are presented and compared to similar models from the literature. The overall dispersion of measured average WBSAR of the sample of the UK population studied is consistent with the dispersion of simulated worst-case WBSAR across multiple numerical phantom families. The statistical results obtained allow the calibration of human exposure assessments made with particular phantoms to a population with a range of individual morphologies.

   @article{Flintoft2014,
     author = {Flintoft, I. D. and Robinson, M. P. and Melia, G. C. R. and Marvin, A. C. and Dawson, J. F.},
     title = {Average absorption cross-section of the human body measured at 1-12 GHz in a reverberant chamber: results of a human volunteer study},
     journal = {Physics in Medicine and Biology},
     year = {2014},
     volume = {59},
     number = {13},
     pages = {3297--3317},
     month = may,
     issn = {0031-9155},
     note = {Date of acceptance: 06/05/2014. This is an author created, uncopyedited version of an article accepted for publication in IOP Physics in Medicine. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/0031-9155/59/13/3297.},
     doi = {10.1088/0031-9155/59/13/3297},
     file = {:pdfs/PMB59-Flintoft-3297.pdf:PDF},
     owner = {idf1},
     postprint = {https://pure.york.ac.uk/portal/files/43360156/PMB59_Flintoft_et_al_postprint.pdf},
     timestamp = {2016.10.12}
   }