No abstract

Reports that low‐intensity microwave radiation induces heat‐shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by slight heating. This study used a microwave exposure system (1.0 GHz, 0.5 W power input; SAR 0.9–3 mW kg−1 for 6‐well plates) that minimises temperature differentials between sham and exposed conditions (≤0.1 °C). Parallel measurement and simulation studies of SAR distribution within this exposure system are presented. We compared five Affymetrix gene arrays of pooled triplicate RNA populations from sham‐exposed L4/adult worms against five gene arrays of pooled RNA from microwave‐exposed worms (taken from the same source population in each run). No genes showed consistent expression changes across all five comparisons, and all expression changes appeared modest after normalisation (≤40% up‐ or down‐regulated). The number of statistically significant differences in gene expression (846) was less than the false‐positive rate expected by chance (1131). We conclude that the pattern of gene expression in L4/adult C. elegans is substantially unaffected by low‐intensity microwave radiation; the minor changes observed in this study could well be false positives. As a positive control, we compared RNA samples from N2 worms subjected to a mild heat‐shock treatment (30 °C) against controls at 26 °C (two gene arrays per condition). As expected, heat‐shock genes are strongly up‐regulated at 30 °C, particularly an hsp‐70 family member (C12C8.1) and hsp‐16.2. Under these heat‐shock conditions, we confirmed that an hsp‐16.2::GFP transgene was strongly up‐regulated, whereas two non‐heat‐inducible transgenes (daf‐16::GFP; cyp‐34A9::GFP) showed little change in expression. Bioelectromagnetics 30:602–612, 2009. © 2009 Wiley‐Liss, Inc.

No abstract

This paper examines the measurement of the specific absorption rate (SAR) of radio frequency energy during magnetic resonance imaging using an optical electric field sensor (OEFS). The sensor was used to measure SAR in a simple phantom during a 3-Tesla MRI scan and the results compared to computer simulations and also those obtained through temperature measurements. Good agreement is demonstrated. The optical electric field sensor has much higher sensitivity for SAR measurement than thermometers and the measurements are much quicker. The application of this technology allows the spatial distributions of SAR within phantoms during MRI to be measured.

This paper examines the effectiveness at 2.4 GHz of heterogeneous and homogeneous phantoms for assessing the performance of antennas used in close proximity to the body, as required for testing body-centric networks. The effects of tissue layering on the antenna performance were also investigated. A simple geometric homogeneous phantom was found to be adequate for body-mounted antenna measurements at this frequency.