elf exposure systems for in vitro and in vivo experiments

ELF exposure systems for in vitro and in vivo experimentsInternational School of Biolelectromagnetics “Alessandro Chiabrera”1st COURSE “Methodology in bioelectromagnetic experimental investigations”

21 – 28 April 2004, Erice

ELF exposure systemsfor in vitro and in vivo experiments

Section of Toxycology and Biomedical SciencesCR ENEA Casaccia, Roma

G.A. Lovisolo, L. Ardoino

ELF exposure systems for in vitro and in vivo experiments

Summary

General requirements of ELF exposure systems

How to generate a uniform magnetic field?

Systems of coils

Basic concepts and definitions

How to determine optimal values for the electric parameters

First steps of improvements: most widely used “reference” systems

Experimental and technical improvements

Two examples of ELF exposure systems for in vivo and in vitro studies


Before listing the requirements, a simple consideration about ELF fieldcharacteristic must be done…

At ELF the electric and magnetic part of EM field can be consideredacting in a separate manner.

An external electric field is greatly attenuated inside the body andperpendicularly oriented to the surface. This is due to the dielectricproperties (conductivity and permittivity) of the body tissues.

On the contrary, the magnetic field penetrate the body virtuallyunperturbed and induced electric fields and currents inside the tissues.

“the main objective of the bioeffects studies of ELF fields isto investigate the effects related to the exposure to the

magnetic field, thus the exposure system has to be essentiallya system for generating magnetic fields”


Basic requirements - all exposure systems -

(Real time) Measurements of the generated fields and of the backgroundlevels

Shielding from external disturbances

Allow sham exposure

Dosimetry: assessment of induced electric fields and currents inside thetarget (especially for in vitro experiments)

Assessment and monitoring of environmental parameters and otherchanges introduced by the system (electrical heating effects, noise and/orvibrations produced by the coils, ...)


Modify intensity and frequency values of magnetic field generated in awide range (0 – 100 Hz).

Large volumes of uniform magnetic field, related to the size of thebiological model.

Simultaneous generation of static and dynamic magnetic fields.

Opportunity of varying magnetic field direction and generating linearlyand circularly polarized fields.

Basic requirements - ELF exposure systems -


• How to generate a uniform magnetic field?


*(Spiegel et al. 1987; Paul et al. 1995)

**(Gundersen 1986; Miller 1989)

Generation of static and ELF magnetic field

Permanent magnets and ferromagnetic materials

Ferromagnetic structures with loop of wires

Other special arrangements: Crawford cell*, flat plates**

Current loops

onlystaticfield

Static and ELF magnetic field can be generated by:


Generation of magnetic field at ELF: ferromagneticmaterial with loops

Reference:Mullins RD, Sisken JE, Hejase HAN and Sisken BF: ’Design and Characterization of a System for Exposure of CulturedCells to Extremely Low Frequency Electric and Magnetic Fields Over a Wide Range of Fields Strengths’Bioelectromagnetics 14: 173-186, 1993.

“Air-gap reactor constructed from lamination of aferromagnetic material with a multiturn winding ofwire on one arm and an air gap in the opposite one.A rectangular medium filled chamber containing livingcells is placed in the air gap.”

lengthgap !=

NIB

0µ

N=1000; lgap= 0.015 m

B = 8.316 10-2 T for one Ampereof current applied to the coil

! B > 80 mT with 1 A


Generation of magnetic field at ELF: MF produced by“sheets of currents”

Three parallel plates used in vertical stacked configuration and appropriately energized:the sheet of current in the central plate divides equally between the upper and the lower onesproducing a magnetic field, parallel to the plates, that is in opposite direction in the two zones

V+V-

E

EB

I

I/2

I/2

BI

I/2

I/2

Magnetic field lines

Reference:Miller DL, Miller MC and Kaune WT, “Addition of Magnetic Field Capability to Existing Extremely Low Frequency Electric FieldExposure System”, Bioelectromagnetics 10: 85-98, 1998.

These kind of systems result inadequate to the present research needs in thebioelectromagnetic area that requests high homogeneous field volumes!


These kind of systems result inadequate to the present research needs in thebioelectromagnetic area that requests high homogeneous field volumes!

An equivalent systems consist of tworectangular solenoid…

I

I/2

I/2

Magnetic field lines

I/2

I/2 B

B

This arrangements eliminatessignificant skin effects andrequires less current than‘plates’ to produce the samefield

Generation of magnetic field at ELF: MF produced by“sheets of currents”


Generation of magnetic field at ELF: system of loops

Because of symmetry consideration, Bx and By vanish along the z-axis and the total flux density B is equal to the z-component Bz

P(x,y,z)

xy

r’1

r’2

r1

r2

r3

r4

s

z2b

2a

!="

""#

µ )(4

0 rfBz

NIi

!=i

zzrBB )()(Pi

P

z-component of flux density B (due to one coil) at thelocation of P is the sum of the contribution of each side (α)

By the principle of superposition, the flux density at P dueto the current in both loops (assuming the same N andcurrent direction), is:

square loops


square loops:

Graphs show

• the uniformity of Bz in awide area (with respect tothe overall volume),

• Bx and By components arenegligible in the samearea.


Bz along z-axis

Bz along vertical lineat points (x, y ≠ 0)

Bx and By along verticalline at points (x, y ≠ 0)

1.0

0.9

1.1

1.2

Bz(x,y,z) / Bz(0,0,0.1)

Bz(0,0,z) / Bz(0,0,0.1)

0 1.00.75z / s

0.25 0.5

Bx(x,y,z) / Bz(0,0,0.1)By(x,y,z) / Bz(0,0,0.1)

0

-0.1

0.1

0.2

0 1.00.75z / s

0.25 0.5

Nor

mal

ized

flux

den

sity


circular loops

[ ]...)(cos)(cos2)

),( 4

44

2

225.12

2

0 ++++

= rPArPAdb

brB

z!!µ!

22(

NI

where: ),('2 dbfA = ),(''4 dbfA =[m-2] [m-4]and

z-of flux density B at the location of P is given by thefollowing formula.

d

d

I

I

P(r,θ)

xy

z

b


As for square loops, for symmetry consideration, Bxand By vanish along the z-axis and the total fluxdensity B is equal to the z-component Bz


Generation of magnetic field at ELF: solenoids

Pθ1

L

az

θ2

z

2

NIL

NI

La

B

LzB

z

z

+=

+=

20

210

4)2/(

)cos(cos2

)(

µ

!!µ

For a long cylinder (L>>a) the field within the solenoid is nearly uniformexcept close to the ends and to the turns of wire …

[In a solenoid N turns of wire wound on a cylindrical form of length L and radius a]


Generation of magnetic field at ELF: ferromagneticmaterials or coils?

are able of producing UNIFORM magnetic flux density across a wide range ofvalues (up to some Teslas), higher than those generated with systems of coils ofsimilar dimension

Systems using ferromagnetic core

cannot vary the magnetic vector direction or generate circularly polarized field

Systems realized by coils and loops

can vary the magnetic vector direction and generate circularly polarized field

can generate and control simultaneously both the static and dynamic fieldcomponents

are restricted in generating high magnetic field by the currents that flow through the wires …


Most suitable arrangements for the generation ofuniform magnetic fields and for satisfying otherfundamental requirements are

systems of coils


Steps and improvements in the generation of the uniformmagnetic fields with coils

I. Two axial coils (Helmholtz)

II. Set of more than two coils:• Rubens (1945)• Lee-Whiting (1957)• Alldred & Scollar (1967)• Merritt (1983)

III. Double wrapped coil

IV. Multiple orthogonal sets

Increasing the level of generated field

Increasing the level of generated fieldand improving the high uniformityvolume

Generation of null field

Generation of circularly polarized fieldsand anyway oriented field


LOOP: single circular or square wire

COIL: several turns of wire

SET: several axial coils (usually from 2 to 5)

SYSTEM: One, two or three orthogonal sets

set

Coils (circular)

B

Scheme of two orthogonal sets of twocoils (multiwire) each, for the

generation of circularly polarizedmagnetic field

Basic concepts and definitions I

B

loop

B

coil

wires

coil section


Basic concepts and definitions IGeneration of low intensity magnetic field at ELF: one single coil

N: number of turns of the coil;I: current which flows through it (A)r: coil radius (m)

r200

NIHB µµ == (T)

loop B

B

y

x

zcoil

r200

IHB µµ == (T)


Generation of magnetic field at ELF: two coils (Helmholtz)

a

x

Px

C1 C2

a = r/2

r

C

Using two axial coils the field in the center of the system canbe increased …It is the sum of the contributions of the two coils

[ ]21

0)0(|0

C

z

C

zyz HHHBBz

+=== = µµ

( )[ ] ( )[ ] !"!#

$

!%

!&

'

++

+

(+

==322

322

211

20

xarxar

r)(yzNI

H

x = 0a = r/2

rr)(yz

243,17155,00NINI

H ===

Basic concepts and definitions I


Basic concepts and definitions I - Helmholtz system

• Most common commercial generators have R=50 Ω and Vmax<40V …

One coil (radius r, N turns, …)

B

y

x

z

Two coils (radius r, N turns, …)

a

x

C1 C2

a = r/2

rB

N is increased by a factor 2I is divided by a factor 2R required for each coil is 100Ω(the 2 coils are set in parallel)

r200

NIHB µµ == (T)

r243,1 0

NIB µ=

Using the same generators (R=50 Ω; Vmax<40V)we can increase the intensity field and theuniformity area


How design a system of coils?

Which factors should be considered?


• uniformity flux density volume (as a function of D)

• field exposure level (required B)

are defined by the experiment design


Definitions of technical parameters

Designing ELF exposure systems several geometrical and physicalconstrains should be considered.

These constrains concern, mainly, the following physical factors:

a) Small-diameter coils do not allow large spatial region of uniformity

b) Large-diameter coils cause weight and cost problems

c) High value of current cause high power dissipation and temperatureincrease


Geometrical and physical constrains

If we want to keep R=100 Ω …N is only a function of D and d

224

4

dd

l NDDN

SR !

"

"!! ===

D

RN

22

4

d

d

t

!="

#

$%&

'=

Physical constrain:

2/DN <d

d

wire

dNt =

Coil cross-section

Elements definition:d - is the wire diametert - is the coil thicknessD – is the coil diameter (2r)

Geometrical constrain: Maximal distance between coils is D/2 Minimal distance … is t=√N d

D/2

t/2 t/2



How determine optimal values for the

coil diameters (D),

wire diameter (d),

number of turns (N),

current (I) ?


Geometrical and physical constraints: number of turns N and B level

Reference:De Seze R., Lahitte A., Moreau J.M., Veyret B.:’ Generation of extremely-low frequency magnetic fields with standardavailable commercial equipment: implications for experimental bioelectromagnetics work’. Bioelectrochemistry andBioenergetics 35: 127-131, 1994.


2/1

22/1

4 D

dRt !!

"

#$$%

&=

'

a: unreasonable value;b: acceptable value4.77 a2.381.651.060.590.410.26200

5.89 a2.94 b2.041.310.730.510.33180

8.49 a4.23 a2.94 b1.881.060.730.47150

19.1 a9.52 a6.61 a4.23 b2.381.651.06100

76.4 a38.1 a26.4 a16.9 a9.52 a6.61 a4.2350

212 a106 a73.4 a47.0 a26.4 a18.4 a11.8 a30

0.850.60.50.40.30.250.2Field intensity B (mT) as a function of coil diameter D and wire diameter d with 10 V

D (mm)

61.930.921.413.77.75.43.4200

65.332.522.614.58.15.63.6180

71.535.624.715.88.96.24.6150

87.6 a43.630.319.410.97.64.8100

123.8 a61.7 a42.9 a27.4 b15.410.76.950

159.9 a79.7 a55.3 a35.4 a19.9 a13.88.930

0.850.60.50.40.30.250.2

Coil thickness t (mm) as a function of coil diameter D and wire diameter d for 100 ΩD (mm)

880N !""#

$%%&

'=

2

2

d

t

1180N !""#

$%%&

'=

2

2

d

t

Example:RequiredD ≥ 15 cmandB = 1 mT



Coil section, length and mass as a function of wire diameter (copper, R=100 Ω)MassM (g)

Lengthl (m)

SectionS (mm2)

Wire diameterd (mm)

1684133360.570.85

32261a46180.791

516179b184713.142

418116620.280.6

201611540.200.5

8267390.130.4

2614160.070.3

521850.030.2

DN!=lengthcoil _

kLength

lengthcoil=

_

System Mass = 2 · k · Mass

Feasibility: current density



28.3-------50.00

11.325.535.3-----20.00

5.712.717.635.4----10.00

2.86.48.817.725.540--5.00

1.12.53.57.110.21628-2.00

0.61.31.83.55.18.014321.00

0.280.640.881.82.54.07.1160.50

0.110.250.350.711.01.62.86.40.20

0.060.130.180.350.510.801.43.20.10

1.55 mm1.77 mm2

1 mm0.79 mm2

0.85 mm0.57 mm2

0.6 mm0.28 mm2

0.5 mm0.20 mm2

0.4 mm0.13 mm2

0.3 mm0.07 mm2

0.2 mm0.03 mm2

Current density J (A/mm2) as a function of wire diameter and sectionI (A)



Feasibility: current density

Unreasonable valuesAcceptable values

N

B1I

043.1

2µ

r=


Improvements in the generation ofuniform magnetic fields with coils


• Helmholtz configuration consists of a pair of parallel coils separated at adistance obtained with the condition that the first and second spatialderivatives of the applied field are equal to zero at the center of volumebetween the two coils.

• Subsequent work showed that several higher-order derivatives can bezeroed using assemblies of three, four or five coils, yielding much largervolumes of uniform field space.

• From this concept several systems of different size, coils shape, numbersof coils and wires have been studied and performed by severalresearchers.


A. - Helmholtz

B. - Rubens

C. - Lee-Whiting

D. - Merritt et al.

E. - Merritt et al.

F. - Alldred & Scollar

Basic “reference” systems


46.65/D26 / 11 / 11 / 26-0.51 D, -0.13 D,+0.13 D, +0.51 D

D, D ,D ,D4squareMerritt et al.(2)

35.69/D19 / 4 / 10 / 4 / 19-0.5 D, -0.25 D, 0,

+0.25 D, +0.5 DD, D ,D ,D, D5squareRubens

40.29/D21 / 11 / 11 / 21-0.52 D, -0.14 D,+0.14 D, +0.52 D

0.95 D, D,D, 0.95 D

4squareAlldred andScollar

68.21/D39 / 20 / 39-0.41 D, 0,

+0.41 DD, D, D3squareMerritt et al.

(1)

17.96/D9 / 4 / 4 / 9-0.47 D, -0,12 D,+0.12 D, +0.47 D

D, D ,D ,D4circularLee-Whiting

1.629/D1 / 1-0.27 D, +0.27 DD, D2square

1.798/D1 / 1-0.25 D, +0.25 DD, D2circularHelmholtz

Centralfield

(µT/A)

Ampere-turnRatios

Coil spacing w.r.t.center of system

Coil diameteror side length

N° ofcoils

CoilShape

Design specifications for basic “reference” systems

Reference: Kirschvink JL, ‘Uniform Magnetic Field and Double Wrapped Coil Systems: Improved techniques for the design of bioelectromagneticsexperiments’, Bioelectromagnetics 13: 401-411 (1992)


Uniformity levels of basic coil configurations

HelmoltzHigh uniformity area:

20 cm x 20 cmArea within 20% contour:

1 m x 1 m

Merritt et al. (4 coil) –Alldred & ScollarHigh uniformity area:

40 cm x 40 cmArea within 20% contour:

1,4 m x 1,4 m


Overall dimensions and uniformity of basic “reference” systems

Reference:* Gottardi G, Mesirca P, Agostini C, Remondini D and Bersani F, ‘A Four Coil Exposure System (Tetracoil) Producing a Highly UniformMagnetic Field’, Bioelectromagnetics 24: 125-133 (2003)

0. 086 D20.163 D20.132 D21.01 D3Merritt et al. (2)

0.012 D20.115 D20.269 D2D3Rubens

0.04 D20.147 D20.228 D20.984 D3Alldred andScollar

0.046 D20.096 D20.169 D20.821 D3Merritt et al. (1)

0.067 D20.212 D20.371 D20.739 D3Lee-Whiting

0.006 D20.016 D20.049 D20.393 D3Helmholtz

Uniformity region0.01%

Uniformity region0.1%

Uniformity region1%

OverallDimension


Last steps for the realization of the “ideal” system:

• Generation of null field: “double-wrapped coil”

• Generation of circular polarization: orthogonal sets


Why a null field should be generated

“Control experiments should be designed such that the only difference betweentreated and untreated groups is the magnetic field …”

In addition to the magnetic field, the coils introduce other undesired changeswhich might have some influence:

Electrical (ohmic) heating effects (temperature increase)

Variable-frequency noise and / or vibration

Small electric fields produced by the voltage drop between loops withinthe coils

The proposed solution consist in the realization of coils “wrapped in parallelwith two separate strands of wire” … where currents can flow in parallel andin antiparallel direction …

Double-wrapped coils also facilitate the use of truly double-blind procedure.


Generation of null field: basic technique

B’=2BPhase shifter(0°)

in out out

Double wrapped coil

B’= + B - B = 0Phase shifter(180°)

in out out

Double wrapped coil

r20

NIB µ=

I1= I2 :

( ) 0IIB2

N

=+=210

2rµ

I1= -I2 :

Double-wrapped coils( )210

2IIB

2N

+=r

µ


Each set of coils generates a field components along its axis; the magnetic field vector is the sum of these components: it rotates and traces an ellipse in the plane perpendicular to both sets; the period of rotation coincides with the period of the ac voltage applied to the loops.

Phase shifter90°

in out 0°

amplifiers

Magnetic field coils

Set 2

Set 1

B1

B2

Generation of circularly polarized field


Each set of coils generates a field components along its axis; the magnetic field vector is the sum of these components: resulting B vector have thedesired direction

Generation of oriented field

in out out

amplifiers

Magnetic field coils

Set 2

Set 1

B1

B2

B


-73 / 107 / 107 / 731 (linear)0.67 D / D / D / 0.67 D4CircularGottardi et al.(2003)

Alldred andScollar21 / 11 / 11 / 213 (linear and

circular)

X: int 1.099, ext 1.15Y: int 0.908, ext 0.95Z: int 0.745, ext 0.78

4SquareRaganella etal. (1994)

Harvey (*)4 / 2 / 2 / 41 (linear)3.15 x 1.164Doublerectangular

Yasui &Otaka (1993)

Rubens11 / 2 / 5 / 2 /112 (circular)Hor: 1.7Ver: 1.85SquareShigemitsu et

al. (1993)

Merrit at al. (1)68 / 34 / 6864 / 32 / 642 (circular)Hor: 2.14

Ver: 1.963SquareBaum et al.(1991)

Basicconfiguration

Ampere-turnRatios

Number of sets(polarization)

coil diameter or lenght(m)

n° ofcoils /setCoil Shape

Design specifications for other systems


Some recent systems for in vivo and in vitro experiments


An In vivo triaxial exposure system*

* Raganella L, Guelfi M and d’Inzeo G, ‘Triaxial Exposure System Providing Static And Low-frequency Magnetic Fields For In Vivo And In Vitro Biological Studies’, Bioelectrochemistry andBioenergetics 35 (1994)

This tri-axial exposure systemprovides static and low-frequencymagnetic fields with differentpolarization.


• The apparatus consists of three sets of four square coils (Alldred &Scollar) to provide greater uniformity.

A magnetic field linearly polarized along the coil axis is allowed. Therefore, we needthree nested systems, each fed independently, to control the component directed alongits axis.Such a configuration also generates elliptically polarized fields.

• Each coil is made by wrapping together two copper wires (Φ=2.5 mm) on a fibreglass frame;

• If the current flows in the same direction in both wires the induced magnetic fields add together producing the desired exposure conditions, while equal and opposite currents produce a null field in the direction of each system;

• The untreated group can be placed in the same experimental conditions as the treated group except for the presence of the magnetic field.

• The number of turns is 44 for the inner coils and 84 for the outer coils. The carrying structure of the system is made entirely of plastic material;

In vivo triaxial exposure system


In vivo triaxial exposure systemIsofield regions for the xz plane of this system (side D<1.2 m)

Uniformity levels are, from the inner to the outer region,0.01%, 0.1% and 1% with respect to the central value.

x (m)

z (m

)

> (50 x 70) cm2

0.01!"

00

00

B

BBxz

Uniformity of 1%with respect to thecentral value:

DEFINITION



Supply and control system:1= triaxial system;2=PC and Labview (NI);3= analog output board*;4=data acquisition board;5=amplifiers;6=digital teslameter;7=triaxial magnetic field sensor and Hall effect probe;8=thermometer;9=GPIB-PCIIA interface board (NI)

*The waveforms, one for each axis component, are generated in digital form (2) bya D/A converter (3); the amplifiers (5) connect the board to the exposure system (1).

5 55

3

8 7

4

6

9

1

2



• Field values generated by each system in thecenter of the exposure area as a function ofthe current

The control program compares the measured and thedesired values, and adjusts the waveform in order toobtain a stable static component of the field along eachaxis.The dynamic components can be superimposed on thestatic component.The values of static and dynamic fields and thetemperature are shown on the panel.

Bx/I= 140.129 µT/A

By/I= 169.629 µT/A

Bz/I= 206.600 µT/A5 55

3

8 7

4

6

9

1

2


Measurements of:• background values (magnetic field) and• residual values when nullifying the field

are necessary for planning the experiments


Electric and magnetic fields measurements: In vivo ELF exposure systems

A B CDE

Bx

By

Bz

General requirements: background measurements I

Background Magnetic field

Background Electric field

The electric field is measured by Holaday HI3638 (directional sensor), while flux magnetic density by Holaday 3627 (isotropic sensor).The static geomagnetic field is about 40 ±1 µT and has been measured by Group3-Danfysik-Hall sensor (directional) and Bartingtonfluxgate magnetometer-MAG-01H (directional).

3020163,5E (V/m)

B = 1.5 mTB = 1.0 mTB = 0

¦I¦ = 11 AB = 0I = 0

0,20-E

0,40-D

0,40-C

0,250,02B

0,30-A

Null magnetic fieldB=0, ¦I¦ = 11 A (µT)

Backgroundmagnetic fieldB=0, I=0 (µT)


A similar exposure system has been realized for in vitro experiments, scaling theprevious one.

In vitro triaxial exposure system


General requirements: background measurements II

1,81,4B max

1,41,0B min

Null magneticfield

B=0, ¦I¦ = 5 A (µT)

Backgroundmagnetic fieldB=0, I=0 (µT)

Electric and magnetic fields measures: In vitro ELF exposure systems

A B CDE

Bx

By

Bz

Square coils system (side 40 cm) is placed in a water jacket incubator.

Background Magnetic field

Background Electric field

31273,5E (V/m)

B = 1,0 mTB = 0¦I¦ = 5 A

B = 0I = 0


An In vitro (Tetracoil) exposure system**

** Gottardi G, Mesirca P, Agostini C, Remondini D and Bersani F, ‘A Four Coil Exposure System(Tetracoil) Producing a Highly Uniform Magnetic Field’, Bioelectromagnetics 24: 125-133 (2003)

A particular four coils system in which thecoils are geometrically constrained on asphere, producing a very uniform magneticfield over a wide volume.


In vitro “Tetracoil” exposure system

R

-b1 b1 b2-b2

a1 a1 a2 a2

1

23

4

1%

0.1%

Uniformity level within 1% (a) and 0.1% (b) with respect to the central value.


If the background values are significantly high compared to the plannedexposure level (B required by experiment design) orexposed and sham-exposed groups need to be placed in the sameincubatorthe system should be surrounded by µ-shieldthusit should also be provided by forced ventilation.

Use of shielding materials (µ-metal)


EF: two horizontal electrodes;MF: five pairs of vertically arrangedrectangular coils

Vertical EFHorizontal MF

EF: 1, 5, 25, 100kV/m,MF: 5, 100 mT; 50 Hz

Various morphologic andchemical parameters

Sprague-Dawleymale rats

Margonato et al.(1993/98)

Three orthogonally systems of four squarecoils each one; basic configuration:Alldred & Scollar

Linear andcircular

2 mT, sham;50 HzImmune system functionC57BL/6 female

miceFrasca et al(1997)

Three pairs of Helmoltz coilsLinear1 mT, sham;50 Hz

Lymphoma/leukemiainduction on DMBAtreated animals

Swiss WebstermiceShen et al (1997)

EF: two horizontal electrodes;MF: two sets of uniformly spacedconductors, around the EF system

Vertical EFHorizontal MF

EF: 65 kV/m,MF: up to 100 mT; 60Hz

Behavioral andneuroendocrine effectsBaboonsRogers et al

(1995)

Three orthogonally systems of four squarecoils each one; basic configuration:Alldred & Scollar

Linear andcircular

2 mT,sham; 50 Hz

Incidence and growth ofimplanted mammarytumor; comparison with X-rays treatment

C3HxDBAfemale mice

Marino et al.(1995/98)

Four coils Merrit system(coil length= 1 m)Linear100 mT,

sham; 50 Hz

Incidence and growth ofmammary tumor with andwithout DMBA treatment

Sprague-Dawleyfemale rats

Baum, Mevissenet al. (1994)

Solenoidal coils(dia= 40 cm; length= 66 cm)Linear0.3-1 mT, 30 mT,

sham; 50 Hz

Incidence and growth ofmammary tumor aftertreatment with DMBA

Sprague-Dawleyfemale rats

Mevissen,Loscher et al.(1993)

Two systems of four rectangular Helmoltzcoils each one, assembled coaxially

Linear(horizontal)

1, 100, 1000 mT,sham; 50 HZLymphoma inductionEm-PIM1

transgenic miceRepacholi et al.(1998)

Exposure systemPolarizationFlux density ;frequencyEnd-pointsAnimals

In vivo experiments with their relative exposure systems


Two pairs of Helmholtz coilsperpendicular to each other housed in an

incubatorCircular0.22 mT;

60 HzCythogenetic and cell kinetic

studiesHuman lymphocytesand CHO fibroblasts

Livingston at al.(1991)

Two pairs of Helmholtz coilsperpendicular to each other placed in a

mu-metal box inside an incubatorVertical0.05 mT;

60 HzNorepinephrine-inducedproduction of Melatonin

Primary pinealocytesof Sprague-Dawley

rats

Rosen at al.(1998)

A pair of Helmholtz coils mounted onthe objective stage of an inverted

microscopeVertical0.04-0.15 mT

5-100 HzIntracellular calcium

oscillations

Jurkat cells(human leukemic

T-cell line)

Lindstrom et al.(1995)

Two pairs of Helmholtz coilsperpendicular to each other and four

small solenoid coils housed in a woodenincubator

Horizontal andVertical

20.9 mT; 16 Hz65.3 mT; 50 Hz

Ca++ intracellularconcentration

T-Lymphocytes fromthymus of BALB-c

mice

Coulton &Barker(1993)

A rotating four coils Merrit system witha mu-metal chamber is placed in a

commercial incubator

Horizontal orVertical

0.2, 1.2 mT;60 HZ

Inhibition of antiproliferativeaction of Tamoxifen and

Melatonin

MCF-7 human breastcancer cells

Harland &Liburdy(1997)

Exposure systemPolarizationFlux density ;frequencyEnd-pointsCells line

In vitro experiments with relative exposure systems


Exposure systems for in vivo experiments require large uniform magneticfield volumes since is fundamental to allow the simultaneous treatment of asmany animals as possible, thus configurations with square coils are generallyemployed,

for animal studies, it is suitable to generate circularly polarized magneticfields thus exposure apparatus with two orthogonal oriented systems of coilsare generally employed.

In vivo experiments


The simple Helmholtz design provide an adequate field uniformity just for invitro experiments, and it’s widely employed for these ones, because is easier tomake for experiments that require relatively small volumes,

apparatus with orthogonal oriented systems of coils would be employed alsofor in vitro experiments, in order to allow the control of all the static and ELFcomponents.

In vitro experiments


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References

elf exposure systems for in vitro and in vivo experiments

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