dosimetry: present researches and future challenges · @ 2008 joe wiart recherche &...

recherche & développement

DOSIMETRY:Present researches and future challenges

Joe Wiart & Man Fai Wong

Orange Labs

""Il faut de l'imagination pour se Il faut de l'imagination pour se

reprrepréésenter la rsenter la rééalitalitéé" "

Giuseppe Giuseppe PontiggiaPontiggia

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Outline

� What is dosimetry

� Why dosimetry is facing the uncertainty

� What are the preliminary investigations

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Why performed dosimetric studies

� Understand how the RF energy is deposited in biological

tissues

� Design exposure system applicable for in vivo and in vitro

� Check the compliance of system to limits

� Assess the exposure encountered in operating network

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Exposure assessment facing multiple Wireless communication technologies

� A few hundred millions of handset user

� Communicating objects

� Different technologies

� Different frequencies (FM, TETRA,TV, GSM,

UMTS, WIFI, WIMAX, UWB ….)

� Different protocols (TDMA,

CDMA,CSMA/CA,…)

� Variable channel occupancy

Number of users (millions) in France vs years

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Large efforts carried out in ANR and RNRT projects

� Past project

� COMOBIO

� ADONIS

� On-going projects

� OP2H

� MULTIPASS

� ANR SAMPER

� Starting projects

� MERODAS

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Standards have been developed: The example of Europe

� Mobile :

� Put on the market :

• EN 50360 & 50361: Adopted in 2000 and replace by the IEC 62209-1 adopted

in 2006

� For new usages and higher frequencies: IEC 62209-2

� Base Station

� Put on the market

• EN 50383 & EN 50384 adopted in 2002

� Put into service

• EN50400 & EN 50401 adopted in 2006

� In situ measurement

• EN50492 Adopted in 2008

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Large efforts have been done to develop experimental equipments

� Small SAR probes have been developed

� Small E & H probes developed

� Probes for in situ measurement

� Personal dosimeter

Small SAR isotropic probes

Small H field probe

E field probe

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Numerical methods have been adapted and improved.

� SAR and temperature calculations are not

anymore a problem.

� Simulations are larger and larger, faster and

faster

• Finite Difference in Time Domain (FDTD) has been

improved (ABC's..)

• Computer Memory increases

• Processors are faster

• Graphic cards used to accelerate the calculations

• New approaches ADI-FDTD, CFDTD…

� Field estimation

� Tools have been developed

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Exposure system are well characterized

0 5 10 15 20 25 30 35 400

5

10

15

Skin

SAR Histograms per tissue (100 highest value)

0 5 10 15 20 25 30 35 400

50

100

Skull

0 5 10 15 20 25 30 35 400

5

10

15

Dura

matt

er

0 5 10 15 20 25 30 35 400

10

20

30

Bra

in

W/kg for 1 Watt emitted

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Numerical methods have been adapted and improved.� SAR and temperature calculations are not

anymore a problem.

� Simulations are larger and larger, faster and

faster

• Finite Difference in Time Domain (FDTD) has been

improved (ABC's..)

• Computer Memory increases

• Processors are faster

• Graphic cards used to accelerate the calculations

• New approaches ADI-FDTD, CFDTD…

� Field estimation

� Tools have been developed

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Numerical methods are quitemature…

recherche & développement

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But they are facing representativeness

Ratio between MSAR10g and the MSAR1g in brain tissues

0.30.6Std

1.52.5Median

1.42.5Mean

ChildrenAdultsMSAR10g/MSAR1g in brain

FACING

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And complexity

� Complex environment

� Complex, non regular and multiples

sources

� Complex and variable bodies

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Facing complexity : models, methods adapted to targetaccuracy� Field prediction / MoM,… PO vs Go + homogeneisation

� Model resolution

s1

s2

s3s4

r1

r2

r3

r4

E

R1s5

r5R2

1mm 2mm

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Facing complexity : Hybridapproaches adapted to target accuracy

� Hybrid methods : eg Domain decomposition

� Combining measurement and simulation

� Rat in reverberating chamber

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Facing uncertainty

x1

xi

xN

Y1

Yi

YM

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Surrogate model?

How determine the key parameters influencing the SAR

X=(Height, Weight, Surface, upper segment, perimeter, BMI…)

SAR=f(X); Is it possible to limit the dimension of X

Are these parameters accessible ?

{Xi} are not independent

How get the joint probability law?

1800MHz

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Thanks

Dans la confusion trouver la simplicité

De la discorde faire jaillir l'harmonie

Au milieu de la difficulté se trouve l'opportunité

Albert Einstein,

Trois règles de travail