This document discusses biomedical applications of electromagnetic fields including magnetic fluid hyperthermia cancer treatments, human exposure to electromagnetic fields, and electric field stimulation of brain cells. Finite element analysis is used to solve electromagnetic and thermal problems in human tissue to optimize medical device design. Examples include optimizing magnetic field uniformity for magnetic fluid hyperthermia, evaluating induced current densities in human models from welding equipment electromagnetic fields, and modeling electric field distribution in the brain from electrodes on the skull.

1. Biomedical applications of electromagnetic fields: human exposure,
hyperthermia and cellular stimulationTitolo: Biomedical applications of electroyp
Elisabetta Sieni hyperthermia and cellular stimulatElisabetta Sieni
Anno: 2011Anno: 2011
Supervisore: Prof Fabrizio Dughiero
Ph.D. candidate: Elisabetta Sieni
Supervisore: Prof. Fabrizio Dughiero
Year: 2011
Supervisor: Prof Fabrizio DughieroSupervisor: Prof. Fabrizio Dughiero
Ph.D. School Director: Prof. Matteo Bertocco
ABSTRACTABSTRACT
Electromagnetic fields are spread in the environment because a lot of the modern devices areElectromagnetic fields are spread in the environment because a lot of the modern devices are
supplied by means of an electric current and others equipments use electromagnetic waves Itsupplied by means of an electric current and others equipments use electromagnetic waves. It
is well known that electromagnetic fields can interact with metal structures, then withis well known that electromagnetic fields can interact with metal structures, then with
electrical conductor material, inducing a temperature increasing by means of Joule effect or, g p g y
energy deposition.gy p
Since electromagnetic fields can interact with electrical conductors, they might induce also the
same effects on the human body structures. In fact, with the same mechanisms the
electromagnetic fields can induce current density or heat in the human body. These
interactions can be studied in order to prevent adverse effects, but also to use them in medical
h h b d h b d f h d ftreatments. For instance, the human body tissue heating can be used for the reduction of
d th th i ht h th ti ff t h i thsome cancer mass and, then, they might have a therapeutic effect, whereas in some case they
might induce muscles contractions or nerve stimulationmight induce muscles contractions or nerve stimulation.
Finite Element Analysis has been used to solve electromagnetic and thermal problems inFinite Element Analysis has been used to solve electromagnetic and thermal problems in
structure with electric and thermal characteristics like the human body tissue whereasstructure with electric and thermal characteristics like the human body tissue, whereas
optimizations techniques have been used to design a medical deviceoptimizations techniques have been used to design a medical device.
Example on the electromagnetic field exposure, Magnetic Fluid Hyperthermia (MFH) cancerExample on the electromagnetic field exposure, Magnetic Fluid Hyperthermia (MFH) cancer
treatments and electric field distribution in the brain when a voltage difference is applied tog pp
the skull bone have been presented and solved by means of the above mentioned techniques.p y q
A. Electromagnetic fields in medical applications: MFH as tumor therapy
The MFH provides the heating of cancer lesions up to a temperature that can damage
tumor tissues. In this therapy the nanoparticles (NPs), injected in the human tissues, are
heated by means of a time‐varying magnetic field which should be as much as possible
uniform in the treatment area.
I h d i f h i fi ld h i fi ld if i fi d hIn the design of the magnetic field source the magnetic field uniformity at first and the
lti t t if it th t i t t bj ti f ti Th iresulting temperature uniformity are the most important objective functions. Then, in
addition the temperature rate in a predefined time interval that allows a temperature riseaddition, the temperature rate in a predefined time interval that allows a temperature rise
up to the therapeutic value (e g 42°C in mild hyperthermia or 60°C in the thermal ablation)up to the therapeutic value (e.g. 42 C in mild hyperthermia or 60 C in the thermal ablation)
is be another plausible objective functionis be another plausible objective function.
t
Thermal and magnetic uniformity solutions
stop
Start
Variable values
A. Thermal 1,8E‐02
2,0E‐02
UM_M
Thermal inhomogeneity
Variable values
optimization
1,4E‐02
1,6E‐02 UM_ T
M optimum
Thermal 1,0E‐02
1,2E‐02
UM
p
T optimum
New variable valuesSet magnetic problem post‐process
6,0E‐03
8,0E‐03
Magnetic computation Thermal computation
2,0E‐03
4,0E‐03
Magnetic computation Thermal computation 0,0E+00
0,0E+00 2,0E‐02 4,0E‐02 6,0E‐02 8,0E‐02
Set thermal problemMagnetic
UT
Thermal MagneticMagnetic field H Computation of the NP
power density
Magnetic
post‐process
Thermal
uniformity
Magnetic
uniformity
i
p y
Magnetic inhomogeneity B Magnetic
y y
Main
coilMagnetic inhomogeneity B. Magnetic
optimization
coil
stop Controlled regionControlled region
(Tumor)(Tumor)(Tumor)(Tumor)
Fl h f h i d h l l d i i i
Correcting
Flow chart for the magnetic and thermal coupled optimization
and results optimization (Evolution Stratyegy algorithms) g
coil
C il iti f th t ti i ti t t i
and results optimization (Evolution Stratyegy algorithms)
Search the thermal and magnetic field uniformity Coils position for the two optimization strategies.
g f f y
Both the magnetic fluid drug and the magnetic field source must be opportunely designedBoth the magnetic fluid drug and the magnetic field source must be opportunely designed
using optimization techniques in order to shape the magnetic field source and for the choiceusing optimization techniques in order to shape the magnetic field source and for the choice
of the magnetic fluid parameters.
0,08
of the magnetic fluid parameters.
0,07
conc_ 0,1%
M lti l Designi of the magnetic fluid (NP size and
0,06
K/s]
conc_ 0,2%
conc 0 3%
Multiple
solutions!!
Designi of the magnetic fluid (NP size and
concentration):
0,05
rate [
conc_ 0,3%
conc_ 0,5%
solutions!!
!
)
Design of the temperature rate‐ Multiple solutions
0 03
0,04
rature
conc_ 1% Ill-posed
tTttT −Δ+
ΩΔ
)()(
)( 11
0 02
0,03
emper
0 015 [K/s]
synthesis
problem t
tTttT
T mm
T
Δ
Δ+
=ΩΔ
)()(
)( 11
0,01
0,02
te
0.015 [K/s] problem tΔ Optimization
0,00
0,0
|*)(|),( TTDF T Δ−ΩΔ≡φ function
0 10 20 30 40 50
l d [ ]nanoparticle diameter [nm]
Developed designs by evolution strategy
S
•Eeffect of the
p g y gy
algorithms: •
•
ff f
position of NPs
g
•electromagnetic source based on magnetic
•
S
injections. and thermal field uniformity; the solution of a
•
SNot uniform NPs
coupled electromagnetic and thermal problem
•
2
Not uniform NPs
distribution . • heating source focusing some aspects of a
h •
•
therapeutic treatment;
NP i j ti it f i th th l d •
•
• NPs injection sites focusing the thermal and
the therapy design problems •
the therapy design problems.
magnetic fields: human exposure,
tion
B Human exposure to magnetic fieldsB. Human exposure to magnetic fields
Human models have been used in order to compute the induced current density in theHuman models have been used in order to compute the induced current density in the
human body tissues generated by means of a magnetic field at frequency under 100 kHzhuman body tissues generated by means of a magnetic field at frequency under 100 kHz.
Some examples of evaluation of the magnetic field effects rising from welding equipments areSome examples of evaluation of the magnetic field effects rising from welding equipments are
reported.reported.
18 mA/m2 27 mA/m2
H b d d l18 mA/m2 27 mA/m Human body model
built from real CTbuilt from real CT
data segmentingdata segmenting
each slice in ordereach slice in order
to distinguish theto distinguish the
different organsdifferent organs
and discretized byy
tetrahedral
elements for Finite
Element Analysis.
Induced current density in huma body model due to resistance welding equipment
The numerical computation of induced current density is important in cases where the
magnetic flux density overcomes prescribed limits. Since in some practical cases the
current that supplies the device can be so high that the magnetic flux density overcomes
li i h i d d d i b l d i d d id if ilimits, the induced current density must be evaluated in order to decide if equipment
ti fi fi ld li it t d b t d dsatisfies field limits suggested by standards.
C Electromagnetic fields in medical applications: electric field applicationsC. Electromagnetic fields in medical applications: electric field applications
Electric field can be used to stimulate brain cells In this example an evaluation of theElectric field can be used to stimulate brain cells. In this example an evaluation of the
possibility to reach the internal structure of the brain with an electric field enough intense topossibility to reach the internal structure of the brain with an electric field enough intense to
allow the cell stimulation is proposed The electric field can be applied by means of two orallow the cell stimulation is proposed. The electric field can be applied by means of two or
more electrodes on the surface of the head.
P1
more electrodes on the surface of the head.
P0 P0P1
P0
P1
P0
P1
Si CSi BElectric field model and some P2
Electric field for different electrode
Sim A Sim CSim BElectric field model and some
computation results
P1
Electric field for different electrode
voltage
computation results
g
Vn 0 VVn 0 V
osso
osso
osso
l f ld h h d f d ff fElectric field in human head for different position of
the electrodesthe electrodes
Numerical analysis on real models of the head has been conducted in order to evaluatey
the effect on different positions of the electrodes on the skull in order to induce an electric
field in the brain structures. It is to be noted that electrical characteristics of the tissues are
a function of the frequency, and then a time‐varying electric field have a different behavior
35
30
25
20
m]
15
E [V/m
10
5
SimA simB
Si C E0
0
SimC E0
0,00 0,05 0,10 0,15 0,20
Electric field in human head
x [m]
Electric field in human head
Some papers
•F Dughiero M Forzan E Sieni Numerical FEM models for the evaluation of EM fields exposure near welding machines Proc COMPUMAG 2009•F. Dughiero, M. Forzan, E. Sieni Numerical FEM models for the evaluation of EM fields exposure near welding machines, Proc. COMPUMAG 2009
•E. Sieni, F. Dughiero, M. Forzan Evaluation of the exposure to magnetic field generated by welding equipment with reference to induced current density, Cedrat News, 2010
M B ll M Chi i F D hi E Si i d L Zilb ti N i l di ti f t d d i h d l b i d ti ki li P I t ti l•M. Bullo, M. Chiampi, F. Dughiero, E. Sieni and L. Zilberti, Numerical prediction of currents produced in human models by induction cooking appliances , Proc. International
Symposium on Heating by Electromagnetic Sources, SGEditoriali, Padova, 67‐74 , May 19‐21, 2010.
•Di Barba, F. Dughiero, E. Sieni, Synthesizing a nanoparticle distribution in magnetic fluid hyperthermia, Proc. International Symposium on Heating by Electromagnetic
Sources, SGEditoriali, Padova, 483‐490 , May 19‐21, 2010.
•Sieni E., Candeo A., Dughiero F., A simplified 3d approach for the evaluation of the SAR and temperature distribution in magnetic nanoparticles hyperthermia, Proc. ESHO
2009 ‐ oral presentation appeared on Visual Journal of Medicine, 13 Ottobre 2009, www.vjmed.net Abstract book pp. 13‐14p pp , , j pp
•P. Di Barba, F. Dughiero, E. Sieni Magnetic Field Synthesis in the Design of Inductors for Magnetic Fluid Hyperthermia, IEEE Trans on Magn, 2010
•P. Di Barba, F. Dughiero, E. Sieni, A. Candeo, Coupled Field Synthesis in Magnetic Fluid Hyperthermia, in press IEEE Trans on MagnP. Di Barba, F. Dughiero, E. Sieni, A. Candeo, Coupled Field Synthesis in Magnetic Fluid Hyperthermia, in press IEEE Trans on Magn
•E. Sieni, F. Dughiero, M. Forzan, Simple 3D fem models for evaluation of EM exposure produced by welding equipments, To be appear on IOSPress 2010
•F Dughiero M Forzan E Sieni A numerical evaluation on Electromagnetic fields exposure on real human body models until 100 kHz In press on COMPEL•F. Dughiero, M. Forzan, E. Sieni A numerical evaluation on Electromagnetic fields exposure on real human body models until 100 kHz, In press on COMPEL