Thermal effects of radiation from cellular telephones

A finite element thermal model of the head has been developed to calculate temperature rises generated in the brain by radiation from cellular telepho nes and similar electromagnetic devices. A 1 mm resolution MRI dataset was segmented semiautomatically, assigning each volume element to one of ten ti ssue types. A finite element mesh was then generated using a fully automati c tetrahedral mesh generator developed at NRPB. There are two sources of he at in the model: firstly the natural metabolic heat production; and secondl y the power absorbed from the electromagnetic field. The SAR was derived fr om a finite difference time domain model of the head, coupled to a model 'm obile phone', namely a quarter-wavelength antenna mounted on a metal box. T he steady-state temperature distribution was calculated using the standard Pennes 'bioheat equation'. In the normal cerebral cortex the high blood per fusion rate serves to provide an efficient cooling mechanism. In the case o f equipment generally available to the public, the maximum temperature rise found in the brain was about 0.1 degrees C. These results will help in the further development of criteria for exposure guidelines, and the technique developed may be used to assess temperature rises associated with SARs for different types of RF exposure.