15

Introduction

classifed as non-ionizing radiation (Wilmink and Grundt, 2012). Over the past decades, THz sources,

detectors, and transmission or refection technologies have been developed and are widely used in dif­

ferent application felds such as chemistry, biomedicine, material science, security and communications.

With the rapid development of THz technologies, the need to study and investigate the biological efects

of THz radiations has become more important than in past.

Optical imaging with non-ionizing radiation makes it difcult to quantitatively assess deep tissue.

Tis is due to its low penetrability into the living body. Te penetration depth is related to the absorp­

tion and scattering of light. However, it has the advantage that there are no exposure afictions like

with ionizing radiation. Molecular imaging using near-infrared light is currently being carried out.

Near-infrared radiation is absorbed in vivo mainly by the hemoglobin in the blood. Optical imaging

can provide information on enzyme metabolism and circulation. Moreover, optical imaging using

non-ionizing radiations in the optical region including the THz band has been studied in various

felds. As mentioned previously, optical imaging has difculty in imaging deep tissues because of

the low penetrability of its electromagnetic waves into the living body. However, there are two non­

invasive methods for visualizing inside the body: one is to irradiate light from outside the body and

image the transmitted light (light transmission imaging). Te other is to inject a fuorescent agent

into the body and then detect and image the patterns emitted from outside the body (biofuorescence

imaging). Near-infrared light with a wavelength of 700 nm or more has less absorption and scattering

biological materials and water than UV and visible light. Because it has relatively high penetrability

into tissues and because it can capture signals at a depth of several centimeters, near-infrared light

can be applied from outside body, and the transmitted light can be imaged. For this reason, near-

infrared light, which has a longer wavelength (700–900 nm) than visible light, is used in biofuores­

cence imaging.

Currently, CT and MRI are in practical use for non-invasive visualization of the inside of living body.

It is hoped that the technology for imaging the inside of the body using non-ionizing radiation in the

optical range will be developed, and in vivo imaging that can be used safely on living bodies will be

utilized in the medical and biological research felds in the future (Pirovano et al., 2020).

1.5 Discussion

Te term “bioelectromagnetism” became popular in scientifc communities around 1980. Tis book

starts with an overview of the historical developments of bioelectromagnetism starting from ancient

times until the twenty-frst century. Aferward, the book discusses past and current knowledge of the

atmospheric electricity and geomagnetic felds with biological systems such as magnetic navigation,

magnetoreception, magnetic sense, etc. and the safety issues regarding human health. Present-day bio-

electromagnetism focuses on biological and medical studies of non-ionizing radiation ranging from

static electric felds through low-frequency electromagnetic felds, radiofrequency electromagnetic

felds up to optical frequencies. Tese studies can be divided mainly into two types, benefcial such as

for the various medical applications and the harmful such as for the establishment of safety guidelines.

By taking them into consideration, it will be possible to represent today’s state on the study of bioelec­

tromagnetism and its future prospects well to discuss the issues that bioelectromagnetism is facing.

Te following text will provide an overview of the chapters covered in this book to illustrate the diver­

sity of research in bioelectromagnetism. Tis book consists of seven chapters. It begins with general

information which forms the objectives and frameworks for understanding of this book. It continues

with the description of the origin of bioelectromagnetism and its defnition as the study of the relation­

ship between electromagnetism and living systems. It also explains the connections of electricity, mag­

netism and electromagnetism with biology, medicine, chemistry, physics and engineering.

Te seven chapters of this book have been arranged into four parts. In Chapter 1 the historical discus­

sion about the development of bioelectromagnetism which sets the fundamental background to then be

able to introduce the topics regarding the interaction between nature and electromagnetism, and also