50Hz磁场下大鼠感应电流的数值分析

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"这篇学术论文深入探讨了50赫兹线性极化和圆极化磁场对大鼠体内诱导电流的影响。研究由东京都立大学电气工程系的Kanako Wake、Toshiyuki Tanaka和Masao Taki进行，发表在2000年的《生物电磁学》杂志上（Bioelectromagnetics 21:354^363）。文章主要关注的是50赫兹频率的磁场如何在大鼠体内产生电流，特别是对松果体和视网膜的影响，因为这两个器官与褪黑激素的合成和浓度变化密切相关。通过使用电阻抗方法，研究人员计算了基于MRI的两种分辨率高达0.125毫米立方的鼠模型中的诱导电流。他们通过幅度和极化两个方面来表征这些诱导电流。计算结果显示，无论是在1.41毫特斯拉（峰值）的线性极化还是圆极化磁场中，诱导电流密度都非常小，均小于30毫安/平方米。对于垂直平面上的极化情况，线性极化和圆极化磁场在松果体内诱导的电流幅度和极化没有显著差异。然而，当磁场的极化方向转至水平时，圆极化磁场在视网膜中产生的诱导电流在幅度上显著高于线性极化磁场。此外，研究还讨论了不同极化方式下，磁场对生物组织的具体影响机制。例如，圆极化磁场可能导致更复杂的电流分布模式，因为它的磁力线环绕方向不断变化，而线性极化的磁场则产生更为定向的电流。这些发现对于理解生物体在电磁场环境下的生理响应以及潜在的生物效应具有重要意义，对于生物医学工程、环境安全评估以及电磁场对人体健康影响的研究提供了宝贵的参考数据。"

Bioelectromagnetics 21:354^363 (2000)

Analysis of Induced Currents in a Rat Exposed

to 50 Hz Linearly and Circul arly P ol arized

M ag netic Fie lds

Kanako Wake,* Toshiyuki Tanaka, and Masao Taki

Department of Electrical Engineering,Tokyo Metropolitan University,Tokyo, Japan

This paper presents a numerical analysis of currents induced in a rat by linearly and circularly

polarized magnetic fields of 50 Hz. Special focus was placed on pineal gland and retina of rats since

these organs were often associated with the changes of melatonin synthesis and concentration.

Induced currents in two MRI-based rat models with resolutions of up to 0.125 mm

were calculated

by using the impedance method. We characterized the induced currents by amplitude and

polarization. Calculated induced current densities were extremely small, i.e., < 30 mA/m

for both

linearly and circularly polarized magnetic fields of 1.41 mT (peak). There were no significant

differences in amplitude nor polarization of induced currents in the pineal gland between the

linearly and the circularly polarized magnetic fields when the polarization was in a vertical plane. In

contrast, the magnetic fields rotating in the horizontal plane produced most circularly polarized

currents both in the pineal gland and in the retina. Bioelectromagnetics 21:354±363, 2000.

ß 2000 Wiley-Liss, Inc.

Key words: numerical analysis; impedance method; pineal gland; retina; polarization; MRI-

based numerical model

INTRODUCTION

Recent years have seen a growing interest in the

effects of electromagnetic ®elds on the melatonin

synthesis in the pineal gland and on the concentration

of melatonin in the blood, especially since melatonin

has been linked to the occurrence of certain kinds

of hormone-related cancers. Several studies have

reported a suppression of the nocturnal melatonin

concentration in rats after exposure to weak static or

extremely low frequency (ELF) magnetic ®elds

[Welker et al., 1983; Lerchl et al., 1991; Kato et al.,

1993, 1997]. There are also some experimental reports

which found no effect on melatonin concentration in

rats exposed to electromagnetic ®elds [Kato et al.,

1994a,b; Lo

sher et al., 1998; John et al., 1998].

Kato et al. [1993, 1994a,b, 1997] conducted a

series of experiments to examine the changes in the

melatonin concentration in the pineal gland and blood

plasma of rats exposed to magnetic ®elds of 50 Hz.

Various linearly, elliptically and circularly polarized

magnetic ®elds of different ®eld strengths ranging

0.02±350 mT (rms) were applied. The circularly

polarized magnetic ®elds above 1.41 mT signi®cantly

suppressed the melatonin concentration compared to

the sham exposed group [Kato et al., 1993], whereas

no effect on the melatonin concentration was found for

the linearly and elliptically polarized magnetic ®elds

of the same order of magnitude [Kato et al., 1994a,b].

The linearly polarized ®elds were either horizontal or

vertical. The circularly and elliptically polarized ®elds

were generated by a superposition of a vertical and a

horizontal ®elds having a 90



phase shift between the

two. The resultant ®elds rotate in a vertical plane.

The results of these experiments suggest that the

observed effects on the melatonin concentration

depend on the characteristics of the applied magnetic

®eld. Lerchl et al. [1991] argued that eddy currents

induced by the applied magnetic ®eld could be

responsible for this phenomenon. The pineal gland

and the retina were discussed as possible sites of

interaction [Reiter, 1993]. If the induced currents are

responsible for the effects on the melatonin synthesis,

ß 2000 Wiley-Liss, Inc.

ÐÐÐÐÐÐ

Contract grant sponsor: Ministry of Education, Science, Sports

and Culture, Japan

Portions of this work were presented in preliminary form at the

1998 Annual Meeting of the Bioelectromagnetics Society.



Correspondence to: Kanako Wake, Dept. of Electrical Engine-

ering, Tokyo Metropolitan University, 1-1 Minami-Osawa,

Hachioji-Shi, Tokyo, Japan. E-mail: kana@com.eei.metro-u.ac.jp

Received 21 August 1998; Final revision received 27 September

1999

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