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Investigation of the spinal cord as a natural receptor antenna for incident electromagnetic waves and possible impact on the central nervous system

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The effects of electromagnetic field (EMF) exposure on biological systems have been studied for many years, both as a source of medical therapy and also for potential health risks. In particular, the mechanisms of EMF absorption in the human or animal body is of medical/engineering interest, and modern modelling techniques, such as the Finite Difference Time Domain (FDTD), can be utilized to simulate the voltages and currents induced in different parts of the body. The simulation of one particular component, the spinal cord, is the focus of this article, and this study is motivated by the fact that the spinal cord can be modelled as a linear conducting structure, capable of generating a significant amount of voltage from incident EMF. In this article, we show, through a FDTD simulation analysis of an incoming electromagnetic field (EMF), that the spinal cord acts as a natural antenna, with frequency dependent induced electric voltage and current distribution. The multi-frequency (100-2400 MHz) simulation results show that peak voltage and current response is observed in the FM radio range around 100 MHz, with significant strength to potentially cause changes in the CNS. This work can contribute to the understanding of the mechanism behind EMF energy leakage into the CNS, and the possible contribution of the latter energy leakage towards the weakening of the blood brain barrier (BBB), whose degradation is associated with the progress of many diseases, including Acquired Immuno-Deficiency Syndrome (AIDS).
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Investigation of the Spinal Cord as a Natural Receptor
Antenna for Incident Electromagnetic Waves and
Possible Impact on the Central Nervous System
Sevaiyan Balaguru, Rajan Uppal, Ravinder Pal Vaid &
Balasubramaniam Preetham Kumar
Department of Electrical and Electronic Engineering, California State University,
Sacramento, California, USA
The effects of electromagnetic field (EMF) exposure on biological systems have been studied
for many years, both as a source of medical therapy and also for potential health risks.
In particular, the mechanisms of EMF absorption in the human or animal body is of
medical/engineering interest, and modern modelling techniques, such as the Finite Difference
Time Domain (FDTD), can be utilized to simulate the voltages and currents induced in different
parts of the body. The simulation of one particular component, the spinal cord, is the focus
of this article, and this study is motivated by the fact that the spinal cord can be modelled
as a linear conducting structure, capable of generating a significant amount of voltage from
incident EMF.
In this article, we show, through a FDTD simulation analysis of an incoming electromagnetic
field (EMF), that the spinal cord acts as a natural antenna, with frequency dependent induced
electric voltage and current distribution. The multi-frequency (100 –2400 MHz) simulation
results show that peak voltage and current response is observed in the FM radio range around
100 MHz, with significant strength to potentially cause changes in the CNS. This work can
contribute to the understanding of the mechanism behind EMF energy leakage into the CNS,
and the possible contribution of the latter energy leakage towards the weakening of the blood
brain barrier (BBB), whose degradation is associated with the progress of many diseases,
including Acquired Immuno-Deficiency Syndrome (AIDS).
INTRODUCTION
The effects of electromagnetic field (EMF) radiation on biological systems have
been studied for decades, both for therapeutic applications such microwave
hyperthermia treatment of cancer (National Cancer Institute, 2011), and also health
risks associated with prolonged exposure (SCENIHR, 2007). Very recently, the World
Health Organization (WHO) listed mobile phone use in the same “carcinogenic
hazard” category as lead, engine exhaust, and chloroform.
In the U.S., the Federal Communications Commission (FCC) regulates EMF
exposure according to table (Table 1) below (FCC, 1997), which sets limits on
electric/magnetic field strengths and power density in the vicinity of human and
animal population.
Address correspondence to B. P. Kumar, Department of Electrical and Electronic Engineering,
California State University, 6000 J Street, Sacramento, CA-95819-6019; E-mail: kumarp@ecs.csus.edu
Electromagnetic Biology and Medicine, Early Online: 1–11, 2012
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ISSN: 1536-8378 print / 1536-8386 online
DOI: 10.3109/15368378.2011.624653
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However, to obtain accurate estimates of voltages and currents induced in
biological systems, and also EMF absorption (measured by the Specific Absorption
Rate or SAR), specific simulation studies have to be performed and the results
analyzed to conclude if the above FCC regulations are maintained.
Effects of Electromagnetic Fields on CNS Pathologies
Exposure to electromagnetic fields has been associated with health risks (Johansen,
2000; Nikitina, 2000), which include neurological diseases such as amyotrophic lateral
sclerosis, senile dementia, Parkinson’s disease, and Alzheimer’s disease (Johansen,
2000). In a Russian study (Nikitina, 2000), for example, the aim was to examine
the health of workers exposed to HF and microwave range (3 and 10 cm wavelength)
EMF. The results of the Johansen study are summarized in Table 2 below.
Such studies show that EMF exposure affects the CNS to a major extent, thereby
increasing the importance of focusing on this part of the human or animal system.
The mechanisms of EMF entry and absorption in the body are not very clearly
understood, and require study of key elements of the CNS system such as the Blood
Brain Barrier (BBB), brain system, and the spinal cord. The aim of this article is to
examine if the antenna-like properties of the spinal cord enhances the EMF
absorption of the CNS, as compared to other systemes in the human or animal system.
Direct Effects of EMF Exposure and Absorption
Experimental studies on animals have clearly shown that electromagnetic fields have
the capacity to alter, and weaken, the structure of the Blood Brain Barrier (BBB)
TABLE 1 FCC Guidelines for EMF exposure (FCC, 1997).
FCC Limits for Maximum Permissible Exposure (MPE)
Frequency
Range (MHz)
Electric Field
Strength (E) (V/m)
Magnetic Field
Strength (H) (A/m)
Power Density (S)
(mW/cm
2
)
Averaging
Time jEj
2
,jHj
2
or S (minutes)
(A) Limits for Occupational/Controlled Exposure
0.3–3.0 614 1.63 (100)*6
3.0–30 1842/f 4.89/f (900/f
2
)*6
30–300 61.4 0.163 1.0 6
300–1500 – f/300 6
1500–100,000 – 5 6
(B) Limits for General Population/Uncontrolled Exposure
0.3–1.34 614 1.63 (100)*30
1.34–30 824/f 2.19/f (180/f
2
)*30
30–300 27.5 0.073 0.2 30
300–1500 f/1500 30
1500–100,000 – 1.0 30
NOTE 1: See Section 1 for discussion of exposure categories. f¼frequency in MHz. *Plane-wave
equivalent power density.
TABLE 2 Pathological changes pattern and rate in workers exposed to 3–30 MHz EMF and control
groups (%) (Johansen, 2000).
Pathological changes Basic groups n¼72 Control groups n¼45 P
Central nervous system disturbances 50.0 13.3 ,0.01
Cardiovascular system diseases 34.7 6.7 ,0.01
Gastrointestinal tract diseases (gastritis,
cholecystitis)
19.4 11.1 ,0.1
Peripheral nervous system diseases 9.7 6.7 NS
Respiratory organs diseases 12.5 4.4 NS
2 S. Balaguru et al.
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(Baureus Koch et al., 2003; NIH, 1995; Deeken and Lo
¨scher, 2007). The blood-brain
barrier (BBB) is an intricate cellular system composed of vascular endothelial cells
and perivascular astrocytes that restrict the passage of molecules between the blood
stream and the brain parenchyma. Specifically, as reported in Deeken and Lo
¨scher
(2007), 344 rats were exposed in a transverse electromagnetic transmission line
chamber to microwaves of 915 MHz as continuous wave (CW) and pulse-modulated
with repetition rates of 8, 16, 50, and 200 Hz. The specific energy absorption rate
(SAR) varied between 0.016 and 5 W/kg. The results showed albumin leakage in 5 of
62 of the controls and in 56 of 184 of the animals exposed to 915 MHz microwaves.
A continuous wave resulted in 14 positive findings of 35, which differ significantly
from the controls. Hence, it has been shown experimentally that even small values of
SAR can potentially damage or alter the BBB properties.
Other investigations have detected abnormalities in the human BBB permeability
in association with HIV infection, which suggest that abnormal permeability of the
BBB is associated with HIV infection. However, the exact role the perturbation of the
BBB plays in HIV neuropathogenesis and in disease progression is unclear. For
example, one would like to know whether the perturbation of the BBB precedes or
succeeds the entry of HIV into the parenchyma (Deeken and Lo
¨scher, 1993). Hence,
the study of any process that weakens the BBB in humans or animals is of vital
importance in the understanding of the mechanisms behind the evolution of AIDS,
in addition to other neurological disorders in the human or animal system.
Proposed Theory and Modeling of Increased EMF Absorption in the CNS
This article is motivated to provide understanding of the mechanism of EMF
induction in the human body, specifically focusing on the modelling of the human
spinal cord structure as a natural antenna receptor for incident EMF, by taking into
account its wire-like and conductive properties. Accurate models of the spinal cord
structure have been developed in the past (Salford et al., 1994; Wesselink et al., 1998;
Struijk et al., 1993a,b), especially for its stimulation in clinical neurological
applications; however, in this article, a concentric cylindrical layer model for the
spinal cord structure is employed, and FDTD analysis carried out for an incident
plane wave. This study will help in understanding significant effects of EMF on
nervous system components such as the Blood-Brain Barrier (BBB), which serves as
a vital block between the human physiological and neurological systems.
FDTD MODELLING OF PLANE WAVE INCIDENCE ON SPINAL CORD
Brief Background on the FDTD Method
The finite-difference time-domain (FDTD) formulation of EMF problems is a
convenient tool for solving scattering problems. The FDTD method, first introduced
by Yee (1996), is a direct solution of Maxwell’s time-dependent curl equation.
Yee’s Finite Difference Algorithm
In an isotropic medium, Maxwell’s equation can be written as:
7£E¼2
m
H
tð1aÞ
7£H¼
s
Eþ1
E
tð1bÞ
Using Yee’s notation, we define a grid point in the solution region as:
ði;j;kÞ¼ðiDx;jDy;kDzÞð2Þ
Investigation of the Spinal Cord 3
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We determine the scattered fields as follows. At t ,0, the program is started by
setting all the field components at the grid points equal to zero:
E0
xði;j;kÞ¼E0
yði;j;kÞ¼E0
zði;j;kÞ¼0ð3aÞ
H0
xði;j;kÞ¼H0
yði;j;kÞ¼H0
zði;j;kÞ¼0ð3bÞ
If we know
Hn21
xði;j;kÞ;Hn21
yði;j;kÞ;Hn21
zði;j;kÞ;En21
xði;j;kÞ;En21
yði;j;kÞand En21
zði;j;kÞ
for all grid points in the solution region, then we can determine new Hn
xði;j;k) and
En
xði;j;k) everywhere from the Eqs. (4a) (4f) below:
Hn
xði;j;kÞ¼Hn21
xði;j;kÞþEn21
yði;j;kþ1Þ2En21
yði;j;kÞ2En21
xði;jþ1;kÞ
þEn21
xði;j;kÞð4aÞ
Hn
yði;j;kÞ¼Hn21
yði;j;kÞþEn21
xðiþ1;j;kÞ2En21
xði;j;kÞ2En21
xði;j;kþ1Þ
2En21
xði;j;kÞð4bÞ
Hn
xði;j;kÞ¼Hn21
xði;j;kÞþ
,
En21
xði;jþ1;kÞ2
,
En21
xði;j;kÞ2En21
yðiþ1;j;kÞ
þEn21
yði;j;kÞð4cÞ
En
xði;j;kÞ¼CaðmÞEn21
xði;j;kÞþCbðmÞ½Hn21
xði;j;kÞ2Hn21
xði;j21;kÞ
2Hn21
yði;j;kÞþHn21
yði;j;k21Þ ð4dÞ
En
yði;j;kÞ¼CaðmÞEn21
yði;j;kÞþCbðmÞ½Hn21
xði;j;kÞ2Hn21
xði;j;k21Þ
2Hn21
xði;j;kÞþHn21
xði21;j;kÞ ð4eÞ
En
xði;j;kÞ¼CaðmÞEn21
xði;j;kÞþCbðmÞ½Hn21
yði;j;kÞ2Hn21
yði21;j;kÞ
2Hn21
xði;j;kÞþHn21
xði;j21;kÞ ð4fÞ
where, following Taflove et al. (1995), we define the following constants:
R¼
m
0=210ð5aÞ
Ra¼c
d
t=
d
2ð5bÞ
Rb¼
d
t=
m
o
d
ð5cÞ
Cb¼Rb=1ði;j;kÞþ
fR
s
ði;j;kÞgð5dÞ
where
m
0
denotes the permeability of free space, 1,
s
, respectively, the permittivity
and conductivity. The spatial increment is
d
¼Dx¼Dy¼Dz, and time increment
d
t
¼nDt.
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The initial field components are obtained by simulating a single-frequency, z
polarized plane wave, traveling along the positive x-direction. A desirable plane
wave condition takes into account the scattered fields at the source plane. For a
three-dimensional case, a typical wave source condition at the plane
j¼js;ðnear y ¼0Þis
En
zði;j;kÞˆsin ð2
p
fn
d
tÞð6Þ
where fis the irradiation frequency, Equation (2.9) is a modification of the algorithm
for all the points on the plane j¼j
s
. Thus, at t¼0, the plane wave source frequency,
fis assumed to be turned on (Taflove et al., 1995). Time stepping simulates the
propagation of waves from this source, which is repeatedly implementing Yee’s finite
difference algorithm on lattice points. The incident wave is then tracked as it first
propagates to the scatterer and then interacts with it via surface current excitation,
diffusion, penetration, and diffraction. Time stepping is continued until the
sinusoidal steady state is achieved at each point.
Modelling of the Spinal Cord
The modelling and study of electromagnetic field (EMF) interaction with the human
spinal cord is motivated by the fact that the spinal cord structure possesses the
following important antenna like properties:
.The spinal cord has an almost linear structure with cylindrical cross-section.
.The innermost region of the spinal cord, such as the cerebro-spinal fluid (CSF), is
conductive, and hence the current can be induced by incident electromagnetic
radiation.
Given the above properties, the two important applications, which would require
an accurate and fast modelling of the EMF interaction with the spinal cord, are
neural therapeutic systems, and EMF hazard study application.
The spinal cord is modelled as a concentric multi-layer cylinder, based on the
cross-section of the spinal cord illustrated in Fig. 1 (Thuery, 1992). The cross-section
is comprised of different biological media, starting with the outer skin layer, and
Gray matter
Ventral End of Spinal Column
Dorsal End of Spinal Column
White matter
Cerebro-spinal fluid (CSF)
Epidural fat
Vertebral bone
Skin
5 mm
FIGURE 1 Transverse section of midcervical spinal cord model (National Cancer Institute, 2011).
Investigation of the Spinal Cord 5
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converging to the innermost central canal of the spinal cord. The detailed electrical
and magnetic properties of the spinal cord model layers are given in Table 3. The
reference medium air is given as the first item in the latter table, and the innermost
central canal of the spinal cord is the last item.
The conduction current density induced in the spinal cord is given by:
J¼
s
Eð7Þ
where Jis the electric current density vector (A/m
2
), E(x,y,z) is the electric field
vector, and
s
is the electricity conductivity distribution, Siemens/m. The voltage
induced in the length of the spinal cord is given by:
V¼2ð
L
0
Edl ð8Þ
where the integration is carried out over the length of the spinal cord.
In addition to the induced voltage and current in the spinal cord, the specific
absorption rate or SAR was also calculated in this study. The SAR is a measure of the
energy absorption and is given by:
SAR ðWatts=kgÞ¼
s
jEj2
2
r
ð9Þ
where the density
r
is usually taken to be approximately equal to that of water
(
r
¼10
3
kg/m
3
).
SIMULATION RESULTS
The FD-TD simulation grid is divided into 30 £30 £30 cells along the x-y-zaxis,
with the cell size Dx¼Dy¼Dz¼D¼6.7 mm, and time step Dt¼1.9 picoseconds.
The simulation time step Dtwas selected based upon the FD-TD method (Taflove,
1995) where:
umax Dt
D#ffiffiffi
1
n
rð10Þ
where n¼3 is the maximum number of space dimensions, u
max
is the maximum
velocity of the electromagnetic plane wave in the biological medium, and DT
and Dare the space step and the time step respectively. The simulation was
performed in MATLABQfor an average spinal cord length of 45 cm (Balaguru
et al., 2001).
TABLE 3 Material properties and dimensions of spinal model.
No. Medium
Thickness
(mm)
Dielectric
constant (1
r
)
Permeability
(
m
H/m)
Conductivity
s
S/m
1 Air 1 4
p
£10
27
0.0
2 Skin 5/3 44.5 4
p
£10
27
0.01
3 Bone 15 6.4 4
p
£10
27
0.02
4 Epidural Fat 8/3 6.4 4
p
£10
27
0.04
5 Cerebro-spinal Fluid (CSF) 4 60 4
p
£10
27
1.7
6 White Matter (WM) 2 15 4
p
£10
27
0.6
7 Grey Matter (GM) 2 10 4
p
£10
27
0.23
Layer Number 8: Central Canal of the Spinal Column
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Voltage and Current Density Distribution
Fig. 2 shows the current density magnitude jJj¼jJ
z
jdistribution induced in
the spinal cord model corresponding to an z-polarized incident plane wave of
magnitude 1 V/m, and frequency 400 MHz. Fig. 2a shows the 3-dimensional current
density distribution, whereas Fig. 2b depicts the cross-sectional top view in the x-y
plane. Similarly, Fig. 3 illustrates the current density distribution (3-dimensional
and top view) at incident plane wave frequency of 1800 MHz. The peak current
density and induced voltage are listed in Table 4 in a frequency range of
100–2400 MHz, and it is observed that the peak current density decreases from
30.9 mA/m
2
at 100 MHz to 3.9 mA/m
2
at 2400 MHz. The increasing attenuation of
the electric field with frequency, as demonstrated by the decrease in induced
current and voltage with frequency, is consistent with current knowledge of
electromagnetic fields, and their dependence of penetration depth in media with
frequency (Salford et al., 1994).
Specific Absorption Rate (SAR) distribution
The SAR distribution was simulated at two frequencies of 400 MHz and 1800 MHz,
and the results are graphically illustrated in Figs 4 and 5, respectively. The SAR
0.2
0.2
0.15
0.1
0.05
0
–0.05
–0.1
–0.15
–0.2
–0.2 –0.15 –0.1 –0.05 0 0.05 0.1 0.15 0.2
0.1
0
–0.1
–0.2
0.2
z, meter
y, meter
y, meter
x, meter
x, meter
(a) 3-dimensional view
Top view (b)
Ventral end Dorsal end
Ventral end Dorsal end
Current density
(mA/m2)
0.00–1.90
1.90–3.80
3.80–5.70
5.70–7.60
7.60–9.50
0.1 0–0.1 –0.2 –0.2 –0.1 00.1 0.2
FIGURE 2 Current distribution in the spinal cord for plane wave incidence: Frequency ¼400 MHz,
Electric field amplitude ¼1 V/m.
Investigation of the Spinal Cord 7
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decreases from a peak value of 0.085 W/kg at 400 MHz to a peak value of 0.035W/kg
at 1800 MHz.
CONCLUSIONS
This article describes the FDTD simulation of plane wave interaction with the
stratified model of the human spinal column and the resultant induced current
TABLE 4 Peak current density, induced voltage, and SAR in spinal column.
Frequency (MHz) Peak Current Density (mA/m
2
) Induced Voltage (millivolts)
100 30.9 8.2
400 9.5 2.5
700 4.9 1.3
1000 4.3 1.1
1800 3.7 0.97
2400 3.4 0.9
0.2
0.2
0.15
0.1
0.05
0
–0.05
–0.1
–0.15
–0.2
–0.2 –0.15 –0.1 –0.05 0 0.05 0.1 0.15 0.2
0.1
0
–0.1
–0.2
0.2
z, meter
y, meter
y, meter
x, meter
x, meter
Ventral end Dorsal end
Ventral end Dorsal end
Current density
(mA/m2)
0.00–0.74
0.74–1.48
1.48–2.22
2.22–2.96
2.96–3.70
0.1 0–0.1 –0.2 –0.2 –0.1 00.1 0.2
FIGURE 3 Current distribution in the spinal cord for plane wave incidence: Frequency ¼1800 MHz,
Electric field amplitude ¼1 V/m.
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and voltage at various frequencies. Preliminary results show that incident EMF
frequencies in the FM band of ,100 MHz show increased response on the spinal
cord structure generating significant voltage of ,8 mV, which could have potential
impact on the CNS processes, including the Blood Brain Barrier.
It cannot be definitely surmised if the purported BBB leakage could occur in the
spinal cord itself or in the main brain region. However, since the voltage generated
by the integrative effect of the cord would be maximum at the upper end of the cord,
it would support the theory that the BBB weakening could potentially occur at the
junction of the brain and spinal cord. Future work will focus on the effects of the
induced voltage and current on the central nervous system, and if it does have
significant impact on the Blood-Brain-Barrier (BBB), which is an area of great
interest in the study of immunological diseases.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the
content and writing of the paper.
0.2
0.2
0.15
0.1
0.05
0
–0.05
–0.1
–0.15
–0.2
–0.2 –0.15 –0.1 –0.05 0 0.05 0.1 0.15 0.2
0.1
0
–0.1
–0.2
0.2
z, meter
y, meter
y, meter
x, meter
x, meter
Top view
3-dimensional view (a)
(b)
Ventral end Dorsal end
Ventral end Dorsal end
SAR values (W/kg)
0.000–0.017
0.017–0.034
0.034–0.051
0.051–0.068
7.068–0.085
0.1 0–0.1 –0.2 –0.2 –0.1 00.1 0.2
FIGURE 4 Specific Absorption Rate (SAR) distribution in spinal cord for plane wave incidence at
400 MHz.
Investigation of the Spinal Cord 9
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magnetic fields and cell membranes. Bioelectromagnetics 6:395–402.
Deeken, J. F., Lo
¨scher, W. (2007). The blood-brain barrier and cancer: Transporters, treatment, and trojan
horses. Clin. Cancer Res. 13:1663.
FCC (1997). Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency
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Johansen, C. (2000). Exposure to electromagnetic fields and risk of central nervous system disease in utility
workers. Epidemiology 11(5):539– 543.
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Nikitina, V. N. (2000). Hygienic, clinical and epidemiological analysis of disturbances induced by radio
frequency EMF exposure in human body. Proc. Int. Wkshp: Clin. Physiolog. Investig. of People Highly
Exposed to Electromagnetic Fields. St. Petersburg, Russia. October 16–17.
Salford, L. G., Brun, A., Sturesson, K., Eberhardt, J. L., Persson, B. R. (1994). Permeability of the blood-brain
barrier induced by 915 MHz electromagnetic radiation, continuous wave and modulated at 8, 16, 50,
and 200Hz. Microsc. Res. Tech. 27(6):535–542.
Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) (2007). European
Commission, ‘Possible effects of Electromagnetic Fields (EMF) on Human Health’, pp. 13– 28, March 21,
Brussels.
0.2
0.2
0.15
0.1
0.05
0
–0.05
–0.1
–0.15
–0.2
–0.2 –0.15 –0.1 –0.05 0 0.05 0.1 0.15 0.2
0.1
0
–0.1
–0.2
0.2
z, meter
y, meter
y, meter
x, meter
x, meter
3-dimensional view (a)
(b) Top view
Ventral end Dorsal end
Ventral end Dorsal end
SAR values (W/kg)
0.000–0.007
0.007–0.014
0.014–0.021
0.021–0.028
0.028–0.035
0.1 0–0.1 –0.2 –0.2 –0.1 00.1 0.2
FIGURE 5 Specific Absorption Rate (SAR) distribution in spinal cord for plane wave incidence at
1800 MHz.
10 S. Balaguru et al.
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Investigation of the Spinal Cord 11
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... Additionally, several technologies based on the delivery of SW radio frequency energy are available for therapeutic medical applications[1][2][3]. However, it cannot be ignored that the non-ionizing radiation of SW with HF may damage biological tissues by non-thermal or thermal mechanisms[4][5][6]. It is known that a rapidly moving electromagnetic field (EMF) can be a health hazard when the energy level is sufficiently high enough, but the variety of electromagnetic devices with different radiation intensities makes the biological effects inconsistent. ...
... The central nervous system was thought to be one of the systems that is sensitive to electromagnetic radiation, and the impairment was mainly characterized by brain dysfunction[4,[21][22][23][24][25]. An epidemiological study tested the electroencephalogram (EEG) characteristics in 98 workers exposed to high frequency (3–30 MHz) EMF for more than 2 years[23]. ...
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With the increasing knowledge of shortwave radiation, it is widely used in wireless communications, radar observations, industrial manufacturing, and medical treatments. Despite of the benefits from shortwave, these wide applications expose humans to the risk of shortwave electromagnetic radiation, which is alleged to cause potential damage to biological systems. This review focused on the exposure to shortwave electromagnetic radiation, considering in vitro, in vivo and epidemiological results that have provided insight into the biological effects and mechanisms of shortwave. Additionally, some protective measures and suggestions are discussed here in the hope of obtaining more benefits from shortwave with fewer health risks.
... Embriyonal ve ergenlik öncesi dönemde yapılan çalışmalarda elektromanyetik alanın canlı organizmaların dokularında patolojik etkileri olabileceği bildirilmiştir (17). Merkezi sinir sistemi, elektromanyetik alanın neden olduğu etkilere en açık sistem olduğu bilinmektedir (12). ...
... Kaspaz-3, hücrelerde apoptozis mekanizması içerisinde yer alan anahtar bir protein olup nörodejenerasyona yol açan süreçlerle ilişkilendirilmiştir (12,13,17). Kerimoğlu ve ark., çalışmalarında elektromanyetik alanın nöronlarda apoptozise neden olduğunu raporlamışlardır (5). ...
... Some authors have reported that the spinal cord can act as an antenna for the effects produced by EMF in the CNS (Balaguru et al., 2012). There is therefore a strong probability that the spinal cord, a component of the CNS that enables constant communication between the brain and peripheral nervous system will also be affected by EMF. ...
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The Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) has updated the previous opinion on ”Possible effects of Electromagnetic Fields (EMF), Radio Frequency Fields (RF) and Microwave Radiation on human health” by the Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE) from 2001, with respect to whether or not exposure to electromagnetic fields (EMF) is a cause of disease or other health effects. The opinion is primarily based on scientific articles, published in English language peer-reviewed scientific journals. Only studies that are considered relevant for the task are cited and commented upon in the opinion. The opinion is divided into frequency (f) bands, namely: radio frequency (RF) (100 kHz < f ≤ 300 GHz), intermediate frequency (IF) (300 Hz < f ≤ 100 kHz), extremely low frequency (ELF) (0< f ≤ 300 Hz), and static (0 Hz) (only static magnetic fields are considered in this opinion). There is a separate section for environmental effects. Radio Frequency Fields (RF fields) Since the adoption of the 2001 opinion extensive research has been conducted regarding possible health effects of exposure to low intensity RF fields, including epidemiologic, in vivo, and in vitro research. In conclusion, no health effect has been consistently demonstrated at exposure levels below the limits of ICNIRP (International Committee on Non Ionising Radiation Protection) established in 1998. However, the data base for evaluation remains limited especially for long-term low-level exposure. Intermediate Frequency Fields (IF fields) Experimental and epidemiological data from the IF range are very sparse. Therefore, assessment of acute health risks in the IF range is currently based on known hazards at lower frequencies and higher frequencies. Proper evaluation and assessment of possible health effects from long-term exposure to IF fields are important because human exposure to such fields is increasing due to new and emerging technologies. Extremely low frequency fields (ELF fields) The previous conclusion that ELF magnetic fields are possibly carcinogenic, chiefly based on occurrence of childhood leukaemia, is still valid. For breast cancer and cardiovascular disease, recent research has indicated that an association is unlikely. For neurodegenerative diseases and brain tumours, the link to ELF fields remains uncertain. No consistent relationship between ELF fields and self-reported symptoms (sometimes referred to as electrical hypersensitivity) has been demonstrated. Static Fields Adequate data for proper risk assessment of static magnetic fields are very sparse. Developments of technologies involving static magnetic fields, e.g. with MRI (Magnetic Resonance Imaging) equipment require risk assessments to be made in relation to occupational exposure. Environmental Effects There are insufficient data to identify whether a single exposure standard is appropriate to protect all environmental species from EMF. Similarly the data are inadequate to judge whether the environmental standards should be the same or significantly different from those appropriate to protect human health.
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In epidural spinal cord stimulation it is likely that not only dorsal column fibers are activated, but that dorsal root fibers will be involved as well. In this investigation a volume conductor model of the spinal cord was used and dorsal root fibers were modeled by an electrical network including fiber excitation. The effects of varying some geometrical fiber characteristics, as well as the influence of the dorsal cerebrospinal fluid layer and the electrode configuration on the threshold stimulus for their excitation, were assessed. The threshold values were compared with those of dorsal column fibers. The results of this modeling study predict that, besides the well known influence of fiber diameter, the curvature of the dorsal root fibers and the angle between these fibers and the spinal cord axis were of major influence on their threshold values. Because of these effects, threshold stimuli of dorsal root fibers were relatively low as compared to dorsal column fibers. Excitation of the dorsal root fibers occurred near the entry point of the fibers.
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A volume conductor model of the spinal cord and surrounding anatomical structures is used to calculate current (and current density) charge per pulse, and maximum charge density per pulse at the contact surface of the electrode in the dorsal epidural space, in the dorsal columns of the spinal cord and in the dorsal roots. The effects of various contact configurations (mono-, bi-, and tripole), contact area and spacing, pulsewidth and distance between contacts and spinal cord on these electrical parameters were investigated under conditions similar to those in clinical spinal cord stimulation. At the threshold stimulus of a large dorsal column fiber, current density and charge density per pulse at the contact surface were found to be highest (1.9.10(5) microA/cm2 and 39.1 microC/cm2.p, respectively) when the contact surface was only 0.7 mm2. When stimulating with a pulse of 500 microseconds, highest charge per pulse (0.92 microC/p), and the largest charge density per pulse in the dorsal columns (1.59 microC/cm2. p) occurred. It is concluded that of all stimulation parameters that can be selected freely, only pulsewidth affects the charge and charge density per pulse in the nervous tissue, whereas both pulsewidth and contact area strongly affect these parameters in the nonnervous tissue neighboring the electrode contacts.
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The characteristics of the waves guided along a plane [I] P. S. Epstein, “On the possibility of electromagnetic surface waves, ” Proc. Nat’l dcad. Sciences, vol. 40, pp. 1158-1165, Deinterface which separates a semi-infinite region of free cember 1954. space from that of a magnetoionic medium are investi- [2] T. Tamir and A. A. Oliner, “The spectrum of electromagnetic waves guided by a plasma layer, ” Proc. IEEE, vol. 51, pp. 317gated for the case in which the static magnetic field is 332, February 1963. oriented perpendicular to the plane interface. It is [3] &I. A. Gintsburg, “Surface waves on the boundary of a plasma in a magnetic field, ” Rasprost. Radwvoln i Ionosf., Trudy found that surface waves exist only when w,<wp and NIZMIRAN L’SSR, no. 17(27), pp. 208-215, 1960. that also only for angular frequencies which lie bet\\-een [4] S. R. Seshadri and A. Hessel, “Radiation from a source near a plane interface between an isotropic and a gyrotropic dielectric,” we and 1/42 times the upper hybrid resonant frequency. Canad. J. Phys., vol. 42, pp. 2153-2172, November 1964. The surface waves propagate with a phase velocity [5] G. H. Owpang and S. R. Seshadri, “Guided waves propagating along the magnetostatic field at a plane boundary of a semiwhich is always less than the velocity of electromagnetic infinite magnetoionic medium, ” IEEE Trans. on Miomave waves in free space. The attenuation rates normal to the Tbory and Techniques, vol. MTT-14, pp. 136144, March 1966. [6] S. R. Seshadri and T. T. \Vu, “Radiation condition for a maginterface of the surface wave fields in both the media are netoionic medium. ” to be Dublished. examined. Kumerical results of the surface wave characteristics are given for one typical case.
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