Specific absorption rate and temperature elevation in a subject exposed in the far-field of radio-frequency sources operating in the 10-900-MHz range

• Published in: IEEE transactions on biomedical engineering Vol. 50; no. 3; pp. 295 - 304
• Main Authors: Bernardi, P., Cavagnaro, M., Pisa, S., Piuzzi, E.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2003; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorption; Anatomy, Cross-Sectional - standards; Biological and medical sciences; Biological effects of radiation; Biological system modeling; Body Temperature - radiation effects; Body Temperature Regulation - radiation effects; Computer Simulation; Dose-Response Relationship, Radiation; Electromagnetic fields; Electromagnetic modeling; Equations; Finite difference methods; Fundamental and applied biological sciences. Psychology; Humans; Models, Biological; Non ionizing radiations. Hertzian waves. Biooptics; Organ Specificity; Radio frequency; Radio Waves; Radiotherapy Planning, Computer-Assisted - methods; Sensitivity and Specificity; Specific absorption rate; Temperature; Temperature distribution; Time domain analysis; Tissues, organs and organisms biophysics; Whole-Body Counting - methods; Whole-Body Irradiation - methods; Human; Absorbed dose; Computer simulation; electromagnetic heating; Body temperature; Thermoregulation; finite difference methods; Far field; Experimental study; Radiofrequency; Modeling; Radioprotection; safety standards; Thermal properties; Time domain method; temperatures; Resonance frequency; Electromagnetic field; Dosimetry; Comparative study; Finite difference method
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2003.808809

The exposure of a subject in the far field of radiofrequency sources operating in the 10-900-MHz range has been studied. The electromagnetic field inside an anatomical heterogeneous model of the human body has been computed by using the finite-difference time-domain method; the corresponding temperature increase has been evaluated through an explicit finite-difference formulation of the bio-heat equation. The thermal model used, which takes into account the thermoregulatory system of the human body, has been validated through a comparison with experimental data. The results show that the peak specific absorption rate (SAR) as averaged over 10 g has about a 25-fold increase in the trunk and a 50-fold increase in the limbs with respect to the whole body averaged SAR (SAR/sub WB/). The peak SAR as averaged over 1 g, instead, has a 30- to 60-fold increase in the trunk, and up to 135-fold increase in the ankles, with respect to SAR/sub WB/. With reference to temperature increases, at the body resonance frequency of 40 MHz, for the ICNIRP incident power density maximum permissible value, a temperature increase of about 0.7/spl deg/C is obtained in the ankles muscle. The presence of the thermoregulatory system strongly limits temperature elevations, particularly in the body core.