# Analyzing the SAR in Human Head Tissues under Different Exposure Scenarios
###### Abstract  
This paper deals with the assessment of induced specific absorption rate (SAR) in various human models under different exposure scenarios, including both laboratory measurements and simulations. Firstly, SAR values were measured in a standardized SAR laboratory using a phantom for two radiofrequency electromagnetic field (RF-EMF) sources at 900 MHz and 1800 MHz. These laboratory measurements served as a reference for SAR calculations conducted on a specific anthropomorphic mannequin (SAM) using a computer simulation technology (CST) program, thus enabling the determination of antenna location and excitation signal levels for further evaluation. Subsequently, simulations were carried out with CST to evaluate average SAR for the head and for specific head tissues such as the brain, muscles, and fat. Realistic computational human models were also used alongside SAM in CST to explore the influence of gender, age, and tissue type on SAR. Various power levels representing low, moderate, and high RF-EMF exposure were applied to the human models to compare against basic restrictions and reference levels. The simulation results indicate significantly higher SAR values calculated for 1800 MHz compared with 900 MHz. The ratio of the highest SAR values at 1800 MHz to 900 MHz is approximately 1.70 for a baby, 2.59 for a child, and 2.84 for both adult female and adult male. While the SAR values for the brain, fat, muscle, and head are comparable at 900 MHz for the baby, the brain's SAR value at 1800 MHz stands out significantly from the other tissues. In contrast with the baby, the difference in SAR values between 900 MHz and 1800 MHz is more pronounced for the child, adult female and adult male. The lowest SAR values at 900 MHz and 1800 MHz were obtained for brain tissue in all human models, while the head has the highest SAR value. The maximum SAR change ratio between the brain and the head is calculated to be 4.44 for the male at 1800 MHz. The results reveal that, although the applied electromagnetic field levels were below reference levels for general public local exposure, some local SAR values exceeded the International Commission of Non-Ionizing Radiation Protection's basic restriction for the general public at certain power levels, particularly at 1800 MHz. The SAR analysis derived from this study is significant in understanding the impact of wireless technologies on health, establishing safety standards, guiding technology advancement, conducting risk assessments, and increasing public awareness. specific absorption rate; SAR laboratory; human head tissues; CST; RF-EMF +
Footnote †: journal: _Scienced Reviews_  
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of RF-EMF. These guidelines are specified by institutions such as the International Commission on Non-Ionizing Radiation Protection (ICNIRP) [1] and the Institute of Electrical and Electronics Engineers (IEEE) [2]. Limits set by these institutions, so-called \"basic restrictions\", are originally derived using the metric of the average specific absorption rate (SAR) for a part of the human body or entire body. SAR measurement procedures are mostly applied to mobile phones. Although base station antennas are installed in places far from the public, this distance has become shortened with the increasingly dense use of wireless technologies. The rapid growth in cellular phone use has resulted in an increase in the number of base stations installed and an increase in public debate about potential health risks associated with electromagnetic energy absorption. Although many recent studies [3; 4; 5; 6; 7; 8] have shown that ambient RF-EMF levels are below established limits, it is essential to carefully determine the doses absorbed by the human body in order to fully evaluate the potential health implications.