Transcript ASSESSMENT OF SAR IN THE HUMAN HEAD, caused by mobile

ASSESSMENT OF SAR IN THE
HUMAN HEAD, CAUSED BY MOBILE
PHONE WITH MEASUREMENT OF THE
EMITTED ELECTRIC FIELD
Branko Stepanovski, Gjorgi Spasovski - Military
Medical Center Skopje Macedonia.
Trajče Trajčev - ECO DETECT Accredited
laboratory for testing of non-ionizing radiation
according EN 17025 standard
?
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
CONTENT
introduction
equipment
model for SAR assessment
in which cases we use this model
some advises for reducing radiation
results and conclusion
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
INTRODUCTION
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
INTRODUCTION
The primary goal of this research is based on measurements of the emitted electric field (E)
from mobile phone to assess the Specific Absorption Rate SAR, at some point in the
brain of the user.
To achieve this, it is necessary to establish such conditions that the field strength (E)
before reaching the sensor of the instrument is weakened (by passage through a water
phantom), as much as it would undermine the field passing through the tissues of head
(skin, ear shell, skull bone, brain liquid) and reach the point at a depth of 2,5 mm in the
human brain.
The equation for transformation of the measured electric field E into the operational quantity
SAR, in near field conditions, according the standard EN 50413, has the following shape:
σ - specific conductivity of brain tissue [S/m]
where
ρ - mass density of the brain tissue [kg/m3]
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
E QUIPMENT USED IN OUR STUDY
Willtek
RF Shield 4921
Аntenna Coupler 4916
Freq. range 700MHz - 6GHz
Willtek
Handheld Spectrum Analyzer
9102B
Frequency range 100kHz – 4GHz
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
MEANING OF NEAR- AND FAR-FIELD
All measurements were performed in near-field region
 (900 MHz) = 0,33 m;  (1800 MHz) = 0,17 m
Reactive near-field Radiating near-field
region
region
Lateral edge of the
region, measured
from antenna
EH
Z=E/H
Component to be
measured
Far-field region
0 to 
 to +2D2/
+2D2/ to 
No
 Z0
Quite Yes
 Z0
Yes
= Z0
E&H
E or H
E or H
“Because all the tissues in human body are non-magnetic (the relative permeability μr ≈ 1)” [6],
although in the region of the near-filed both, magnetic and electric components of the
electromagnetic field should be considered, conclusion is drawn that main contribution to SAR at
RF, is from the interaction with the electric field. That is why, our assessment of SAR is made with
analysis of the electric field.
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I NTERACTION
OF ELECTROMAGNETIC
RADIATION WITH MATTER
absorption
Incident radiation
reflection
transmission
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attenuation
ESTABLISHING EQUALITY
BETWEEN E B AND E D
Eb = Ed
Eb – electric field strength at 2.5 mm depth in the brain;
Ed – electric field strength at the detector’s surface.
Attenuationtissue = Attenuationphantom
- average relative dielectric constant
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
T ISSUE DATA
All data are valid for an average adult man
Type of tissue
Dielectric
constants of each
tissue
Brain
ρ = 1040 kg/m3
Skull
bone
Skin
εrb σ [S/m] εrsb εrs
900 MHz
56,0
0,97
16,62
41,41
1800 MHz
43,5
1,15
15,56
38,87
Ear
cartilage
Brain
liquid
Dura
Air
εrc
εrbl
εrd
εra
46,00
71,71
44,4
1
34,7
67,2
42,9
1
30,6
4
0,3
5
26,3
Equivalent
38,10
(1,9 GHz)
Average thickness
of each tissue [mm]
2,5
6,5
2
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6
BASIC CALCULATIONS FOR
THE TISSUE
Еach layer of tissue that lies between mobile phone and brain have different relative
dielectric constant. Based on their individual contribution to the interaction with the
radiation, the average dielectric constant of all these tissues can be calculated.
q(t) – antenna’s electrical charge in dependence of time;
- average relative dielectric constant
All contribution in tissue attenuation
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
PHANTOM MATERIAL DATA
Type of material
Air
Plexiglas
Distilled water
Relative
dielectric
constants of each
material
εra
εrp
εrw
900 MHz
1
2,63
78,2
34,7
1800 MHz
1
2,59
77,4
30,6
6
(2 x 3 = 6)
15 (900 MHz)
13 (1800 MHz)
35
Thickness of each 14 (900 MHz)
material [mm]
16 (1800 MHz)
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Equivalent
BASIC CALCULATIONS FOR
THE PHANTOM
rtf – distance between the mobile phone
and the surface of the detector
All contribution in phantom attenuation
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SPECIFIC CHARACTERISTIC OF
THE INTENSITY OF THE MOBILE
PHONE RADIATION
Hold it at he bottom
By covering large areas of the phone with your
hand, you reduce its ability to send and receive
signals. The phone then increases its power and
transmits stronger radiation to compensate this.
So hold the phone as far down as possible, so it
can operate at low power.
Get in the best position
You can see the signal reception strength in
the display. When reception is good, the
phone reduces power and radiation. If
reception is poor , the phone uses maximum
power and radiation.
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
DIFFERENT INTENSITY OF
RECEIVED SIGNAL
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B A S I C R E S T R I C T I O N S F O R T I M E VA RY I N G E L E C T R I C A N D
M A G N E T I C F I E L D S F O R F R E Q U E N C I E S U P TO 1 0 G H Z .
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RADIATION PENETRATES
DEPENDING ON AGE
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TIME DEPENDENCE OF
TEMPERATURE DURING TALK
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PHASES OF RADIATION DURING
THE USE OF MOBILE PHONE
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RESULTS AND CONCLUSION
Results: In the case of optimal received signal of the tested mobile phones, assessed SAR
values are close to the values that are declared by the manufacturers, for those mobile phones
(valid for an ideal case). In case of weakening of the received signal by mobile phones (real
situation), SAR values can be increased multiple times. E is 3 to 4 times greater
Conclusion:
Possibilities of the measuring equipment and the applied mathematical model opens up the
doors for the following research:
•With change of the received signal for the tested phones, SAR assessment is made for many
different situations in reality, for the same phone (in places where received signal of mobile
phones is lower) . For such places SAR grows dramatically, due to its dependence on |Ei|2.
•With change of the attenuation factor (changes of the thickness of water phantom), it can be
determined SAR for different depths in the brain or in any other tissue,
•With accurately calculated SAR we can assess temperature increase at the point of
measurement, located in brain tissue.
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
R EFERENCES
1. Guidelines for Limiting Exposure to Time-varying Electric, Magnetic and Electromagnetic
Fields (up to 300 GHz), ICNIRP
2. 50413 Basic Standard on Measurement and Calculation Procedures for Human Exposure
to Electric, Magnetic and electromagnetic Fields (0 Hz – 300 GHz), European Committee
for Standardization
3. Elektromagnetizam I, II, Mirjana Jonoska
4. FDTD Computation of Temperature Rise in the Human Head for Portable Telephones,
Wang, J. and O. Fujiwara
5. On Averaging Mass of SAR Correlating with Temperature Elevation due to a Dipole
Antenna, A. Hirata, K. Shirai, and O. Fujiwara
6. Interaction between mobile terminal antenna and user, Juho Poutanen
7. SAR and Temperature Elevation in a Multilayered Human Head Model due to an
Obliquely Incident Plane Wave, A. I. Sabbah and N. I. Dib
8. SAR Estimation for Cellular Phone, Association of Radio Industries and Businesses
9. Review of the scientific evidence for Limiting Exposure to EMFs (0–300 GHz), NRPB
Britain
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Thank yu for your attention
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
П РАШАЊА
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
S OME REMARKS
Unlike the brain itself, “temperature elevation 0.2 K– 0.3 K in hypothalamus leads to
altered thermoregulatory behavior” [5].
Acute RF heating (more than about 41-43 oC for 2-3 hours) can induce lens opacities
(cataracts) in experimental animals. However, threshold for cataract induction resulting
from chronic exposure to RF EMFs has not been defined. [9]
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RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
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П РОЦЕНА НА ДОЗА КАЈ НЕЈОНИЗИРАЧКОТО ЗРАЧЕЊЕ
За процена на количеството на апсорбираната енергија во човековото тело (дозата)
потребно е де се дефинираат неколку клучни поими:
• Специфична енергетска апсорпција (ЅА): Се дефинира како апсорбирана енергија
по единица маса биолошко ткиво изразена со џул врз килограм (J/kg).
• Количина на специфична енергетска апсорпција (ЅАR): Се дефинира како
апсорбирана енергија по единица маса биолошко ткиво за одредено време, (W/kg).
• Густина на моќност (Ѕ): Кога моќност на зрачењето на рамен бран ќе помине низ
единица површина нормална на правецот на движење на бранот. Се дефинира (W/m2)
SA(Jkg-1) = SAR (Wkg-1) * време на експозиција (секунди)
Основни единици
Единици за
јонизиречко зрачење
Единици за
не-јонизирачко зрачење
J/kg
Sv
Доза
SA
Специфична апсорпција
J/kg *1/т
W/kg
Sv/т
Количина на доза
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SA/h
SAR
Количина на специфична
апсорпција
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RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
S IMPLIFIED MODEL OF TISSUE
LAYERS
Еach layer of tissue that lies between mobile
phone and brain have different relative dielectric
constant. Based on their individual contribution
for each can calculate the average dielectric
constant of all these tissues
Eb
Depth
in
brain
CSF –
liquor
(brain
liquid)
D
u
r
a
Skull bone
26,3 mm
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Ear
cartilage
Air
S
k
i
n
Ein
The Heart's Electromagnetic
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2012 - N
PRIL
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Affected part of
the head, taken
in consideration
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Depth
in
brain
CSF –
liquor
(brain
liquid)
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
D
u
r
a
Skull bone
Cartilage
Air
S
k
i
n
S IMULATING
THE
ATTENUATION FROM THE
HEAD TISSUES
Ed
detector
P
l
e
x
i
g
l
a
s
P
l
e
x
i
g
l
a
s
Distilled
water
19 (21) mm
35 mm
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Ein
Air
mobile
phone
T ISSUE DATA
Skin
Ear
cartilage
Brain
liquid CSF
Dura
Air
εrsb
εrs
εrc
εrbl
εrd
εra
0,97
16,62
41,41
46,00
71,71
44,4
1
34,7
1,15
15,56
38,87
38,10
(1,9 GHz)
67,2
42,9
1
30,6
6,5
2
6
4
0,3
5
26,3
Brain
ρ = 1040 kg/m3
Skull
bone
Relative
dielectric
constants of
each tissue
εrb
σ [S/m]
900 MHz
56,0
1800 MHz
43,5
Average
thickness of
each tissue
[mm]
2,5
Type of tissue
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Equival
ent
M EANING OF SAR
SAR – specific absorption rate [W/kg]
Time derivative of the incremental electromagnetic energy (dW) absorbed by
(dissipated in) an incremental mass (dm) contained in a volumen element (dV) of
given mass density (ρ).
where
Ei
σ
ρ
ci
dT/dt
r.ms. value of the electric field strength in the tissue in V/m;
conductivity of body tissue in S/m;
density of body tissue in kg/m3;
heat capacity in body tissue in J/kg K;
time derivative of temperature in body tissue in K/s.
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
Table below indicates the method at different
distances from radio-stations:
Reactive near-field region
Radiating near-field
region
Far-field region
Lateral edge of the region,
measured from antenna
0 to 
 to +2D2/
+2D2/ to 
EH
No
Quite Yes
Yes
Z=E/H
 Zo
 Zo
= Zo
Component to be measured
E&H
E or H
E or H
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
S IMPLIFIED MODEL OF TISSUE
LAYERS
Еach layer of tissue that lies between mobile phone
and brain have different relative dielectric constant.
Based on their individual contribution for each can
calculate the average dielectric constant of all these
tissues
Depth
in
brain
CSF –
liquor
(brain
liquid)
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
D
u
r
a
Skull bone
Cartilage
Air
S
k
i
n
Ed
P
l
e
x
i Distilled water
g
l
a
s
P
l
e
x
i
g
l
a
s
Ein
Air
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
mobile phone
air
plexiglas
distilled water
detector
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
ASSESSMENT OF SAR IN THE
HUMAN HEAD, CAUSED BY MOBILE
PHONE WITH MEASUREMENT OF THE
EMITTED ELECTRIC FIELD
Branko Stepanovski, Gjorgi Spasovski - Military
Medical Center Skopje Macedonia.
Trajče Trajčev - ECO DETECT Accredited
laboratory for testing of non-ionizing radiation
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
RAD2012, 25-27 APRIL 2012 - NIŠ, SERBIA
В ЗАЕМНОДЕЈСТВО
НА ЕЛЕКТРОМАГНЕТНОТО
ЗРАЧЕЊЕ СО МАТЕРИЈАТА
Количина на специфична енергетска
апсорпција (ЅАR) (W/kg).
Апсорпција
Упаден зрак
Рефлексија
Густина на моќност
(Ѕ) (W/m2)
Трансмисија
RAD2012, 25-27 APRIL 2012 NIŠ, SERBIA
Aпсорбирана доза