Morimoto Ryota, Laakso Ilkka, De Santis Valerio, Hirata Akimasa
Department of Computer Science and Engineering, Nagoya Institute of Technology, Nagoya, Japan.
Phys Med Biol. 2016 Jul 21;61(14):5406-5425. doi: 10.1088/0031-9155/61/14/5406. Epub 2016 Jul 1.
This study investigates the relationship between the peak temperature elevation and the peak specific absorption rate (SAR) averaged over 10 g of tissue in human head models in the frequency range of 1-30 GHz. As a wave source, a half-wave dipole antenna resonant at the respective frequencies is located in the proximity of the pinna. The bioheat equation is used to evaluate the temperature elevation by employing the SAR, which is computed by electromagnetic analysis, as a heat source. The computed SAR is post-processed by calculating the peak spatial-averaged SAR with six averaging algorithms that consider different descriptions provided in international guidelines and standards, e.g. the number of tissues allowed in the averaging volume, different averaging shapes, and the consideration of the pinna. The computational results show that the SAR averaging algorithms excluding the pinna are essential when correlating the peak temperature elevation in the head excluding the pinna. In the averaging scheme considering an arbitrary shape, for better correlation, multiple tissues should be included in the averaging volume rather than a single tissue. For frequencies higher than 3-4 GHz, the correlation for peak temperature elevation in the head excluding the pinna is modest for the different algorithms. The 95th percentile value of the heating factor as well as the mean and median values derived here would be helpful for estimating the possible temperature elevation in the head.
本研究调查了在1-30 GHz频率范围内人体头部模型中，峰值温度升高与10克组织平均的峰值比吸收率（SAR）之间的关系。作为波源，在耳廓附近放置一个在各个频率下谐振的半波偶极天线。生物热方程用于通过将电磁分析计算得到的SAR作为热源来评估温度升高。通过六种平均算法计算峰值空间平均SAR对计算得到的SAR进行后处理，这些算法考虑了国际指南和标准中提供的不同描述，例如平均体积中允许的组织数量、不同的平均形状以及耳廓的考虑。计算结果表明，在关联不包括耳廓的头部峰值温度升高时，排除耳廓的SAR平均算法至关重要。在考虑任意形状的平均方案中，为了更好地关联，平均体积中应包含多个组织而非单个组织。对于高于3-4 GHz的频率，不同算法对不包括耳廓的头部峰值温度升高的关联程度一般。此处得出的加热因子的第95百分位数以及均值和中值将有助于估计头部可能的温度升高。
