Electromagnetic Fields in Biological Systems

James C. Lin

• Publisher: CRC Press
• Year: 2016
• eBook ISBN: 9781000218695
• Edition: 1
• Topic: Medicine
• Subtopic: Biotechnology in Medicine

Spanning static fields to terahertz waves, this volume explores the range of consequences electromagnetic fields have on the human body. Topics discussed include essential interactions and field coupling phenomena; electric field interactions in cells, focusing on ultrashort, pulsed high-intensity fields; dosimetry or coupling of ELF fields into biological systems; and the historical developments and recent trends in numerical dosimetry. It also discusses mobile communication devices and the dosimetry of RF radiation into the human body, exposure and dosimetry associated with MRI and spectroscopy, and available data on the interaction of terahertz radiation with biological tissues, cells, organelles, and molecules.

1

Coupling of Electromagnetic Fields into Biological Systems

James C. Lin

1.1 Introduction

1.2 Physical Laws Governing Electromagnetic Phenomena

1.3 Electromagnetic Properties of Tissue

1.4 Electromagnetic Phenomena at Tissue Interfaces

1.5 Static Electric and Magnetic Fields

1.6 Time-Varying Electromagnetic Fields

1.7 Low-Frequency and Quasistatic Electric and Magnetic Fields

1.8 Propagation of Electromagnetic Energy from Antennas

Quasistatic Fields of a Dipole Antenna • Near Field of a Dipole Antenna • Far Field of a Dipole Antenna

1.9 Coupling of Quasistatic Electric and Magnetic Fields

Quasistatic Electric Field Coupling • Quasistatic Magnetic Field Coupling • Combined Quasistatic Electric and Magnetic Fields • Summary of Quasistatic and Low-Frequency Field Coupling

1.10 Radiofrequency Fields and Energy Deposition

Radiofrequency Reflection and Transmission at Planar Interfaces • Radiofrequency Field Coupling to Bodies with Curvature • Orientation and Polarization Dependence • Radiofrequency Coupling in the Near Field

1.11 Radiofrequency Dosimetry and Energy Absorption in Anatomical Models

Coupling from Handheld Mobile Phones • Specific Absorption Rate in Childlike Head Models • Fields from Body-Worn Devices • Whole-Body Exposure from Cell-Phone Base Stations • Summary of Radiofrequency Field Coupling

1.12 Coupling of Short and Ultra-Wideband Pulses into the Human Body

Induced Electromagnetic Pulse Fields in Biological Bodies • Gaussian Electromagnetic Pulse Inside a Planar Biological Medium • Gaussian Electromagnetic Pulse inside Spherical Head Models • Constant Conductivity Spherical Model for Electromagnetic Pulse Propagation • Induced Ultra-Wideband Field and Current • Summary of Short and Ultra-Wideband Pulse Coupling

1.13 Coupling of Millimeter and Terahertz Waves

Transmitted and Reflected Millimeter Waves and Terahertz Fields, and Energy Deposition • Summary of Millimeter-Wave Coupling

References

1.1 Introduction

Electromagnetic fields or energies of frequencies that range from 0 Hz to 1 THz (1 THz = 10¹² Hz) have wavelengths longer than 1 μm in air. Furthermore, at wavelengths close to the micrometer limit of the spectrum, electromagnetic energy behaves as infrared radiation. These wavelengths produce photons (or quanta) of low energy; therefore, under ordinary circumstances, the energy in a photon is too low to break chemical bonds, excite electrons, or produce ionization of biological molecules. Consequently, they are often referred to as low-energy or nonionizing radiation. Electromagnetic energies propagate through a material medium (including biological medium) at a constant speed in that medium. For example, they propagate through air or vacuum at the speed of light, that is, at 2.998 × 10⁸ m/s. Moreover, electromagnetic energies with wavelengths longer than 10 m (frequencies lower than 30 MHz) have interaction properties that differ greatly from those of wavelengths that are approximately equal to or less than the physical dimensions of a human body.

Although living organisms thrive in a natural electromagnetic environment, they are increasingly subjected to a myriad of human-made nonionizing radiation in the form of electromagnetic fields and waves for telecommunication uses, industrial and medical applications, and many other purposes. For example, the radiofrequency (RF) band of 300–30,000 kHz (or 0.3–30 MHz with wavelengths from 1000 m to 10 m) is used in medicine for ablating, coagulating, and cauterizing tissue. Recently, nanosecond-pulsed electric fields were shown to induce long-lasting plasma membrane permeabilization changes. They are providing new insights into the nature of pulsed electric field induced opening of conductance pores and into molecular mechanisms that underlie biological effects. The technological breakthrough at millimeter-wave (mmW) and terahertz frequencies has stimulated new applications not only in biology and medicine but also in environmental studies, material science, telecommunication, and security screening in the form of whole-body image scans. Besides their primary intended roles, these fields and waves produce other effects that may influence the vital activities of a biological system. The changes produced depend on many physical and biological factors. They may or may not be grossly apparent and observable soon after exposure of the living organism.

The biological effects of electromagnetic fields and waves have been a subject of scientific research since the discovery of electromagnetic radiation and its first use in therapeutic applications more than 100 years ago. Since then, our knowledge regarding its effects on health has increased tremendously. Nevertheless, they have become the focus of much attention because of the expansion and distribution of electric power at 50 and 60 Hz in the extremely-low-frequency (ELF) spectrum (between 3 Hz and 3 kHz) and because of the accelerated use of RF radiation (300 MHz–6 GHz and beyond) in wireless communication in recent decades. A notable reason for the increased attention on the subject is the uncertainty and lack of understanding of the mechanism of interaction of electromagnetic fields and waves with biological systems. Although ELF fields and RF radiation are all part of the same known electromagnetic spectrum, the mode of coupling into biological tissues and mechanism of interaction can be quite different for th...

Table of contents

• Cover
• Halftitle
• Series
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Editor
• Contributors
• 1 Coupling of Electromagnetic Fields into Biological Systems
• 2 Pulsed Electric Fields in Biological Cells and Membranes
• 3 Static, Low-Frequency, and Pulsed Magnetic Fields in Biological Systems
• 4 Interaction of Extremely Low–Frequency Electromagnetic Fields with Biological Systems
• 5 Mobile Communication Fields in Biological Systems
• 6 Medical Devices and Systems Exposure and Dosimetry
• 7 Terahertz Radiation: Sources, Applications, and Biological Effects
• Index