微波暴露下实验用鼠体重与电磁能量吸收关系研究

The EM energy absorption in different rat model exposed to microwave irradiation

目的探讨实验用鼠暴露于3GHz微波时，其体重与全身平均比吸收率以及电磁能量吸收之间的关系。方法首先基于鼠核磁共振三维解剖图像，建立了包含45种生物组织的鼠电磁模型，再通过改变模型的单元尺寸来改变模型的大小与体重，得到长度9～24cm，相应体重16～334g共16个鼠电磁模型；然后采用时域有限差分法计算3GHz微波照射下各个鼠模型体内的感生电场分布，进而得到鼠模型吸收的电磁能量与比吸收率。结果在3GHz微波照射下，鼠体重与全身平均比吸收率的关系可分为3个区域，每个区域均可拟合成一条直线；其中，小鼠区域全身平均比吸收率变化剧烈，中等鼠区域变化趋于平缓，大鼠区域变化更为平缓。鼠体重与电磁能量吸收的关系可以拟合成一条二次曲线，当鼠模型较小时，吸收的电磁能量大致相同，当鼠模型逐渐增大时，鼠吸收的电磁功率也逐渐增大，但增大的幅度小于体重增加的幅度。结论动物越大，其在电磁场中吸收的电磁功率也越大，但其全身平均比吸收率却越小。在相同的照射条件下，大鼠因体重变化而产生的受照剂量差异比小鼠小很多，因此建议使用大鼠作为电磁生物效应实验用鼠。

Objective To find out the relationship between the weight and whole body averaged SAR, and the relationship between the weight and the EM energy absorption in rat model exposed to 3 GHz microwave irradiation. Methods Based on 3D rat NMR images, a rat EM model consisting of 45 tissues was established, then by changing the size of model cell, 16 models of which the sizes varied from 9 cm to 24 cm, and the weights from 16 g to 334 g correspondingly were established too. Using FDTD method, the induced electric fields in these rat models were calculated, and then SAR and EM energy absorption have been obtained accordingly. Results The relationship between the weight and the whole body averaged SAR of rat model exposed to 3 GHz microwave irradiation can be divided into three sections, and each of them can be fitted into one line. In small rat section, SAR changed sharply; in middle rat section, SAR changed moderately; in large rat section, SAR changed littlely. The relationship between the weight and the EM energy absorption of rat model were fitted into one quadratic polynomial curve. The EM energy absorption was almost identical when the model is small, with the increasing of the weight, the EM energy absorption also increases, but the increasing ratio of the energy is less than that of the weight. Conclusions Larger rat absorbs more EM energy, but gets less SAR. Exposed to the same irradiation, the dose differences of larger rat is much less than that of smaller rat because of the changes in body weight, so the larger rat is to be recommended.