Digital signal processing is one of the fundamental technologies utilized in the field of biomedical engineering. Typical purposes of digital signal processing are acquisition and analysis of biological signals, noise reduction and extraction of the required signals, and identification of biological systems. This introductory article provides some basic ideas and techniques of digital signal processing in biomedical engineering:biosignal sampling, spectrum analysis, and filter design.

This manuscript is to introduce the recording and analytic methodologies of surface electromyography (sEMG). sEMG is often concerned not only biomechanics and sport sciences but also recently IoT and ordinary life monitoring. However, although there are many publications for studies of biomechanics or rehabilitation, their documents for EMG is not understandable enough for the persons who are not specialized as EMG users. In view of the development of IoT or computer technologies, it must increase the researches and the novel technologies with EMG recordings in our daily lives but, because there is no standard for EMG, the beginners for EMG might face the difficulties to use EMG in their own interests. The author will try to explain for them on the physiological basis, the recording and analyses for EMG and then will also describe the applications of EMG.

A creative engineer tends to understand the principles and phenomena not only based on mathematical physics but also by intuition. Author has picked up several topics among such principles and phenomena in the area of medical ultrasound and challenges to explain them intuitively in this article. The chosen topics are the lateral resolution, Doppler blood flow measurement, a piezoelectric element, ultrasonic absorption by biological tissues, and intensive/extensive variables. Author hopes that the presented intuitive explanation will help the readers to enhance their creativity as an engineer.

Virtual reality is a technology to mimic real objects and environments. In this manuscript, the author introduces a basic concept of virtual reality as well as metaverse, which is a recent trend. In medical and biological engineering, virtual reality is used for basic and application studies to reveal basic biological functions and support medical treatment. The virtual reality system consists of display system, input system and simulation. The author explains the difference of the two types of head mounted displays and introduces tips for a beginner of virtual reality to develop a system.

Optical measurement techniques have many features suitable for biomedical applications. This review paper summarizes the fundamental principles and techniques of optical measurement with a focus on biomedical applications. First, the physical properties and parameters of light are presented. Next, the basic elements of optical measurement, such as units, light sources, photodetectors, image sensors, lenses, optical fibers, integrating spheres, and lock-in amplifiers, are described. Then, the basic techniques of optical measurement, such as spectroscopy, optical interferometry, time-resolved measurement, and scattering measurement, are explained. Examples of applied optical measurement are introduced as laboratory test instruments, pulse oximeters, optical fiber sensors, structural imaging, and functional imaging.

Already 50 years have past since the principle of MRI has been proposed. MRI has become the necessary clinical diagnostic tool such as X-CT. MRI techniques have been still in further progress. In this manuscript, the historical review of NMR and MRI were introduced, and the fundamental principle of NMR phenomena such as the principle of magnetic resonance, relaxation process and NMR information were introduced to understand MRI techniques. Following these introduction, fundamental MR imaging techniques such as 2-D Fourier Transform in relation to MR imaging, parameters of image construction, the role of gradient field, contrast enhanced images and fast MR imaging techniques were introduced.

NM (Nuclear medicine) uses radioisotopes to diagnose and treat biological functions. This paper outlines the history and principles of PET. Measurement of projection data by electron-positron annihilation, 3D scan that contributed to the advancement of PET performance, TOF and other representative technologies will be explained.

X-ray CT occupies the most essential position among various diagnostic imaging equipment. In this article, the author provides an introductory explanation of CT technology. It is intended to provide some interesting entry points but not an overview of CT as a whole. Regarding the image reconstruction method, the author tried to explain it in a way that facilitates intuitive understanding, in the belief it is more important than formulas. In addition, some interesting topics are picked up that could lead to a better understanding of CT. Some issues that are often misunderstood are also picked up.

An endoscope is a device that allows an observation for the inside of objects that are difficult for humans to see directly by inserting a thin tube with an optical system. By the endoscope, doctors can observe the inside of the human body in real time and perform treatment by using treatment instruments through the forceps channel installed inside the endoscope. In this manuscript, the author explains the history of endoscope, the basic structure of the endoscope system, the fields of use and endoscope types, and the technology used.

Electromagnetic waves below 3000THz (1THz=10¹²Hz) are called “non-ionizing radiation,” while those below 300GHz are commonly referred to as “radiofrequency (RF) waves” (but are defined by the Radio Law of Japan as electromagnetic waves with frequency spectra from 10kHz to 3000GHz) . The primary effect of RF waves on human physiology is acute, resulting from the heat-generating effect of induced currents within the body. The magnitude of this effect correlates with the RF wave strength when the biological threshold is exceeded, but there is no cumulative effect for exposure to radio waves below the threshold. This concept is analogous to the acute effects (non-probabilistic effects) of ionizing radiation, based on the hypothesis that weak radio waves do not cause late effects (probabilistic effects) in humans. This review paper provides an overview of the bioeffects of electromagnetic waves on humans from an electrical engineering perspective, followed by a comparison of Japan’s guidelines with international safety standards for human protection from radio waves, focusing on the heat-generating effects of RF waves, along with the underlying principle and rationale behind safety limits and protection guidelines for whole-body exposure to radio waves.

As technology advances, a wide variety of biomaterials have been developed. Biomaterials are materials that are used to support body functions or to replace organs that are no longer functioning. Today, a wide variety of biomaterials are in use and their properties are being used to advantage. Research on these biomaterials will become even more important in the future of medicine. In this manuscript, the basics of biomaterials, their classification, and their applications are introduced.