Dosimetric Characterization of a Waveguide-Based Exposure System for Laboratory Studies with Unrestrained Mice at 1.9 GHZ
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It is essential for research on the biological effects of radiofrequency (RF) electromagnetic energy to be conducted using well-characterized exposure systems in order to ensure the reliability of research outcomes. Realizing this importance, a waveguide-based in vivo exposure system was developed at the Consumer and Clinical Radiation Protection Bureau of Health Canada for conducting laboratory studies with live mice exposed to RF electromagnetic energy. This thesis presents the important aspects and dosimetric characterization evaluation of the developed exposure system. The Health Canada in vivo exposure system consists of four identical cylindrical waveguide chambers, each with a plastic cage for housing the animal. The chamber is fed by circularly-polarized RF power in the 1.9 GHz cellular frequency band, and is vertically mounted so that the long axis of the animal is co-planar with the rotating incident electric field. Power sensors were used along with directional or hybrid couplers and a digital voltmeter for data acquisition for real-time dose rate monitoring. The exposure chamber was characterized to obtain its dosimetric information in three aspects including field intensity and pattern, influences of an exposed mouse, and chamber dose rate evaluation. The variations and pattern of the electric field intensity inside the mouse cage volume were analyzed. The impacts due to the presence of the exposed mouse, such as reflected power at chamber input ports and the axial ratio of the circularly-polarized field when impinging upon the animal, were investigated. Chamber dose rates quantified in terms of whole-body-average (WBA) specific absorption rate SAR), brain-average (BA) SAR and peak-spatial-average (PSA) SAR were evaluated. The evaluations were experimentally performed on mouse cadavers and live mice and computationally conducted on heterogeneous mouse models. The results obtained from experiments and computations were in fairly good agreement with each other. SAR data obtained from live-mouse exposures were found to be within the bounds derived from the dosimetric information obtained from experiments with mouse cadavers. Uncertainties in measured and computed results were estimated. The dosimetric information produced by this work supports the use of the Health Canada exposure system for carrying out laboratory studies with live mice. The data obtained from these biological studies would contribute to a concerted assessment of human health risks from exposure to RF energy emitted from wireless communication devices such as mobile phones, wireless fidelity (Wi-Fi) and Bluetooth devices.