Physics in Medicine and Biology · 2000 · 127 citations · 10 references
EngineeringBiomedical EngineeringElectrical EngineeringComputational Heat TransferHeat TransferMedical PhysicsHealth PhysicsHeat ConductionHeat Transfer ModelingRadiative Heat TransferRadiobiological ModelingTissue Responses To RadiationFinite Difference Time Domain ModelingFinite Element Mesh GenerationFinite Element ModelingFinite Element Thermal AnalysisFinite Element Thermal ModelingTetrahedral Mesh GenerationTetrahedral MeshingThermal Effects
In the normal cerebral cortex, high blood perfusion provides efficient cooling. A finite‑element thermal model of the head, built from a 1 mm MRI segmentation and tetrahedral mesh, combined metabolic heat and absorbed RF power (derived from a finite‑difference time‑domain SAR calculation) to compute steady‑state temperature distributions via the Pennes bioheat equation. The model predicts a maximum brain temperature rise of about 0.1 °C for typical consumer devices, supporting guideline development.
A finite element thermal model of the head has been developed to calculate temperature rises generated in the brain by radiation from cellular telephones and similar electromagnetic devices. A 1 mm resolution MRI dataset was segmented semiautomatically, assigning each volume element to one of ten tissue types. A finite element mesh was then generated using a fully automatic tetrahedral mesh generator developed at NRPB. There are two sources of heat in the model: firstly the natural metabolic heat production; and secondly the power absorbed from the electromagnetic field. The SAR was derived from a finite difference time domain model of the head, coupled to a model 'mobile phone', namely a quarter-wavelength antenna mounted on a metal box. The steady-state temperature distribution was calculated using the standard Pennes 'bioheat equation'. In the normal cerebral cortex the high blood perfusion rate serves to provide an efficient cooling mechanism. In the case of 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.
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