Hart R A, Gandhi O P
University of Utah, Department of Electrical Engineering, Salt Lake City 84112-9202, USA.
Phys Med Biol. 1998 Oct;43(10):3083-99. doi: 10.1088/0031-9155/43/10/027.
Time-domain potentials measured at 64 points on the surface of a large canine heart, considered comparable with those of a human heart, were used to calculate the electric fields and current densities within various organs of the human body. A heterogeneous volume conductor model of an adult male with a resolution of approximately 6 mm3 and 30 segmented tissue types was used along with the admittance method and successive over-relaxation to calculate the voltage distribution throughout the torso and head as a function of time. From this time-domain voltage description, values of [E(t)] and [J(t)] were obtained, allowing for maximum values to be found within the given tissues of interest. Frequency analysis was then used to solve for [E(f)] and [J(f)] in the various organs, so that average, minimum and maximum values within specific bandwidths (0-40, 40-70 and 70-100 Hz) could be analysed. A comparison was made between the computed results and measured data from both EKG waveforms and isopotential surface maps for validation, with good agreement in both amplitude and shape between the computed and measured results. These computed endogenous fields were then compared with exogenous fields induced in the body from a 60 Hz high-voltage power line and a 60 Hz uniform magnetic field of 1 mT directed from the front to the back of the body. The high-voltage power line EMFs and 1 mT magnetic field were used as 'bench' marks for comparison with several safety guidelines for power frequency (50/60 Hz) EMF exposures. The endogenous electric fields and current densities in most of the tissues (except for organs in close proximity to the heart, for example lungs, liver, etc) in the frequency band 40-70 Hz were found to be considerably smaller, between 5% and 10%, than those induced in the human body by the electric and magnetic fields generated by the 60 Hz sources described above.
在大型犬心脏表面64个点测量的时域电位，被认为与人类心脏的电位相当，用于计算人体各个器官内的电场和电流密度。使用了一个成年男性的非均匀体积导体模型，分辨率约为6立方毫米，有30种分段组织类型，并结合导纳法和逐次超松弛法来计算整个躯干和头部随时间变化的电压分布。从这个时域电压描述中，获得了[E(t)]和[J(t)]的值，从而能够在给定的感兴趣组织内找到最大值。然后使用频率分析来求解各个器官中的[E(f)]和[J(f)]，以便分析特定带宽（0 - 40、40 - 70和70 - 100赫兹）内的平均值、最小值和最大值。将计算结果与心电图波形和等电位表面图的测量数据进行比较以进行验证，计算结果与测量结果在幅度和形状上都有很好的一致性。然后将这些计算出的内源场与由60赫兹高压电源线和从身体前部指向后部的1毫特斯拉60赫兹均匀磁场在体内感应出的外源场进行比较。高压电源线电磁场和1毫特斯拉磁场被用作“基准”，与一些工频（50/60赫兹）电磁场暴露的安全指南进行比较。发现在40 - 70赫兹频段内，大多数组织（心脏附近的器官除外，例如肺、肝脏等）中的内源电场和电流密度比上述60赫兹源产生的电场和磁场在人体中感应出的场小得多，在5%到10%之间。
