IN 1974, the International Radiation Protection Association (IRPA) formed a working group on non-ionizing radiation (NIR), which examined the problems arising in the field of protection against the various types of NIR. At the IRPA Congress in Paris in 1977, this working group became the International Non-Ionizing Radiation Committee (INIRC). In cooperation with the Environmental Health Division of the World Health Organization (WHO), the IRPA/INIRC developed a number of health criteria documents on NIR as part of WHO’s Environmental Health Criteria Programme, sponsored by the United Nations Environment Programme (UNEP). Each document includes an overview of the physical characteristics, measurement and instrumentation, sources, and applications of NIR, a thorough review of the literature on biological effects, and an evaluation of the health risks of exposure to NIR. These health criteria have provided the scientific database for the subsequent development of exposure limits and codes of practice relating to NIR. At the Eighth International Congress of the IRPA (Montreal, 18–22 May 1992), a new, independent scientific organization—the International Commission on Non-Ionizing Radiation Protection (ICNIRP)—was established as a successor to the IRPA/INIRC. The functions of the Commission are to investigate the hazards that may be associated with the different forms of NIR, develop international guidelines on NIR exposure limits, and deal with all aspects of NIR protection. Biological effects reported as resulting from exposure to static and extremely-low-frequency (ELF) electric and magnetic fields have been reviewed by UNEP/ WHO/IRPA (1984, 1987). Those publications and a number of others, including UNEP/WHO/IRPA (1993) and Allen et al. (1991), provided the scientific rationale for these guidelines. A glossary of terms appears in the Appendix.

Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz)

National Institute of Standards and Technology における超伝導研究及び生活

IN THIS document, guidelines are established for the protection of humans exposed to electric and magnetic fields in the low-frequency range of the electromagnetic spectrum. The general principles for the development of ICNIRP guidelines are published elsewhere (ICNIRP 2002). For the purpose of this document, the low-frequency range extends from 1 Hz to 100 kHz. Above 100 kHz, effects such as heating need to be considered, which are covered by other ICNIRP guidelines. However, in the frequency range from 100 kHz up to approximately 10 MHz protection from both, low frequency effects on the nervous system as well as high frequency effects need to be considered depending on exposure conditions. Therefore, some guidance in this document is extended to 10 MHz to cover the nervous system effects in this frequency range. Guidelines for static magnetic fields have been issued in a separate document (ICNIRP 2009). Guidelines applicable to movement-induced electric fields or time-varying magnetic fields up to 1 Hz will be published separately. This publication replaces the low-frequency part of the 1998 guidelines (ICNIRP 1998). ICNIRP is currently revising the guidelines for the high-frequency portion of the spectrum (above 100 kHz).

ICNIRP Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz).

Noninvasive brain stimulation with transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) is valuable in research and has potential therapeutic applications in cognitive neuroscience, neurophysiology, psychiatry, and neurology. TMS allows neurostimulation and neuromodulation, while tDCS is a purely neuromodulatory application. TMS and tDCS allow diagnostic and interventional neurophysiology applications, and focal neuropharmacology delivery. However, the physics and basic mechanisms of action remain incompletely explored. Following an overview of the history and current applications of noninvasive brain stimulation, we review stimulation device design principles, the electromagnetic and physical foundations of the techniques, and the current knowledge about the electrophysiologic basis of the effects. Finally, we discuss potential biomedical and electrical engineering developments that could lead to more effective stimulation devices, better suited for the specif...

https://www.annualreviews.org/doi/pdf/10.1146/annurev.bioeng.9.061206.133100

Noninvasive human brain stimulation.

The aim of this study is to evaluate all the 58 available NFL cases and compare various predictors for mild traumatic brain injuries using a detailed and extensively validated finite element model of the human head. Global injury measures such as magnitude in angular and translational acceleration, change in angular velocity, head impact power (HIP) and HIC were also investigated with regard to their ability to predict the intracranial pressure and strains associated with injury. The brain material properties were modeled using a hyperelastic and viscoelastic constitutive law. Also, three different stiffness parameters, encompassing a range of published brain tissue properties, were tested. 8 tissue injury predictors were evaluated for 6 different regions, covering the entire cerebrum, as well as for the whole brain. In addition, 10 head kinematics based predictors were evaluated both for correlation with injury as well as with strain and pressure. When evaluating the results, a statistical correlation between strain, strain rate, product of strain and strain rate, Cumulative Strain Damage Measure (CSDM), strain energy density, maximum pressure, magnitude of minimum pressure, as well as von Mises effective stress, with injury was found when looking into specific regions of the brain. However, the maximal pressure in the gray matter showed a higher correlation with injury than other evaluated measures. On the other hand, it was possible, through the reconstruction of a motocross accident, to re-create the injury pattern in the brain of the injured rider using maximal principal strain. It was also found that a simple linear combination of peak change in rotational velocity and HIC showed a high correlation (R=0.98) with the maximum principal strain in the brain, in addition to being a significant predictor of injury. When applying the rotational and translational kinematics separately for one of the cases, it was found that the translational kinematics contribute very little to the intracranial distortional strains while the rotational kinematics contributes insignificantly to the pressure response. This study underlines that the strain based brain tissue injury predictors are very sensitive to the choice of stiffness for the brain tissue.

Predictors for traumatic brain injuries evaluated through accident reconstructions.

In this study a mathematical model, based on Navier Stokes equations, was developed and validated against experimental data. This model predicts the pressure changes in the spinal canal as a function of the volume change inside the canal during neck bending in the x-z (sagittal) plane. Another aim of the study was to investigate pressure phenomena and ganglion injuries at static neck extension loading and dynamic neck extension trauma with a head-restraint present. Experiments on pigs were conducted. Preliminary results indicate that ganglion injuries, as well as pressure transients inside the spinal canal, seem to correlate to the phase shift when the neck passes an s-shape (or maximal retraction) during the rearward motion of the head. That is, when the upper neck quickly changes from a flexion to an extension shape. Static loading of the neck resulted in no signs of injuries to the ganglia. A possible candidate for a neck injury criterion is presented, based on the relative acceleration between the top and the bottom of the cervical spine. A tolerance level based on the pig tests is also discussed.

https://publications.lib.chalmers.se/records/fulltext/181305/local_181305.pdf

A new neck injury criterion candidate-based on injury findings in the cervical spinal ganglia after experimental neck extension trauma

Low-frequency and transient magnetic fields of moderate flux densities are known to generate visual phenomena, so-called magnetophosphenes. In the present study, time-variable very low frequency (10–50 Hz) electromagnetic fields of moderate flux density (0–40 mT) were used to induce magnetophosphenes. The threshold values for these phosphenes were determined as a function of the frequency of the magnetic field both in normal subjects and colour defective ones. Maximum sensitivity occurred at a frequency of approximately 20–30 Hz, and with broad-spectrum light the threshold flux density was 10–12 mT. The threshola values were found to be dependent upon the intensity and the spectral distribution of the background light. Sensitivity decreased during dark adaptation. In certain respects deutans differed from subjects with normal colour vision. Possible mechanisms for generation of magnetophosphenes are discussed. The present magnetic threshold curves show a close resemblance to corresponding curves obtained by electric stimulation at various frequencies provided the electric thresholds are divided by the a.c. frequency. These problems are under current investigation in our laboratory. This is in full agreement with the assumption that the fluctuating magnetic field affects retinal neurons by inducing currents which polarise synaptic terminals.

Magnetophosphenes: a quantitative analysis of thresholds.

A human-body 3D mathematical model for simulation of car-pedestrian impacts

Neck injuries in car collisions. a review covering a possible injury mechanism and the development of a new rear-impact dummy

impact-velocities (<20 km/h) often cause pain in the
neck region as well as a number of other neurological
symptoms, most of which can be related to the nerve
paths that pass through the cervical intervertebral
foramina.
When the neck is flexed or extended in the sagittal
plane the length of the cervical spinal canal alters but
the cross-sectional area of the canal remains almost
constant. During flexion-extension motion of the
cervical spine, the size of the inner volume of the
spinal canal will change. Since the tissues inside the
canal can be considered incompressible, an alteration
will take place of either the amount of cerebro spinal
fluid or the amount of blood in the veinplexa of the
epidural space, or both. This requires fluid
transportation through the intervertebral foramina as
well as along the spinal canal. During a whiplash
extension motion, the flow velocity can be expected to
rise far above physiologically normal levels and
pressure gradients can thus be expected to occur. In turn,
the soft tissues inside and around the cervical spine and
particularly in the intervertebral foramina will sustain
mechanical strain and stress.
Anaesthetised pigs were exposed to a swift
extension-flexion motion of the neck while the
pressure inside the spinal canal and the skull was
measured. Pressure pulses of magnitudes up to 150
mmHg (20 kPa) were observed during the motion. The
magnitude of pressure is for each moment dependent on
the position of the neck, the velocity and the
acceleration of the motion.
Plasma membrane dysfunction was indicated by the
results from light microscopic analyses of the cervical
and the three upper thoracic spinal ganglia revealing
the staining of nerve cells and satellite cells by protein
complexed to the Evans Blue dye.

/pdf/pressure-effects-in-the-spinal-canal-during-whiplash-irm8gbr697.pdf

Per Lövsund

Papers

A new neck injury criterion candidate-based on injury findings in the cervical spinal ganglia after experimental neck extension trauma

Magnetophosphenes: a quantitative analysis of thresholds.

A human-body 3D mathematical model for simulation of car-pedestrian impacts

Neck injuries in car collisions. a review covering a possible injury mechanism and the development of a new rear-impact dummy

Pressure Effects in the Spinal Canal During Whiplash Extension Motion - A Possible Cause of Injury to the Cervical Spinal Ganglia