'Remcom_nl_1-05.indd' by Unknown

Electromagnetic Simulation Used to Evaluate

Safety of Combining EEG and MRI

Electromagnetic simulation software

for SAR modeling." In FCC Part 95

the tissues adjacent to the electrodes. The

is being used to investigate the safety

Section 603(f), it is stated: "Applications

difference in SAR between the electrodes

of an important research technique

for equipment authorization of

and no-electrodes conditions was greater

that integrates electroencephalography

devices operating under this section

with the birdcage coil than with the

(EEG) with magnetic resonance imaging

must contain a finite-difference time-

surface coil. The peak 1g averaged SAR

(MRI). The integration of these two

domain (FDTD)

values were highest at 124

analysis methods has the potential to

computational

electrodes, increasing to as much

improve investigations of brain activity

modeling

as two orders of magnitude

because EEG offers high temporal

report showing

at 300 MHz compared to the

resolution while MRI offers high spatial

compliance with

original value. At 300 MHz, there

resolution. Concerns have arisen about

these provisions

was a fourfold increase of SAR

temperature increases in sensitive brain

for fundamental

averaged over the bone marrow,

tissues that could be caused by the

emissions."

and a sevenfold increase

current induced in the EEG electrodes

in the skin. The study

by the radio frequency (RF) power

Using the XFDTD

shows that the presence

generated by MRI. Leonardo Angelone

geometric modeler,

of nonmagnetic, high

and Dr. Giorgio Bonmassar, researchers

they constructed

conductive metallic EEG

at the Massachusetts General Hospital,

an FDTD model of

electrodes can increase

simulated the RF power dissipated in the

a birdcage coil placed symmetrically

the peak SAR on the

human head in an integrated MRI-EEG

around the head. Using the standard

subject by as much as 172

software simulation.

features available in XFDTD, a circular

times.

excitation was simulated. Again using

Angelone and Bonmassar used

standard postprocessing features in the

The simulation also showed that with

electromagnetic simulation to determine

Bio-pro module, XFDTD was used to

the electrodes and leads, because of the

the RF energy absorbed by the human

compute the electric and magnetic fields

RF induced currents along the leads, the

head in an integrated EEG-MRI

and the SAR (Specific Absorption Rate).

electric field increases near the electrodes.

experiment. They selected XFDTD for

Simulations were performed with surface

Thus, the electrodes increase the electric

this simulation. According to the Federal

and birdcage MRI coils.

field on the skin and on the surrounding

Communications Commission (FCC),

tissues. This generates an increase of peak

"Currently, the finite-difference time-

The results confirmed an average of up to

SAR values for both surface and birdcage

domain (FDTD) algorithm is the most

seven times the original value in averaged

coils, relative to that produced by the RF

widely accepted computational method

SAR on the skin as well as an increase in

of the coil only.

REQUEST FOR INFORMATION

I am interested in receiving informa-

Here is my personal contact information:

tion about the following Remcom

Name: _______________________________________

product(s) or service(s):

❑ XFDTD

❑ Bio-Pro

❑ Pro

❑ SE

Address: ______________________________________

❑ VariPose

❑ Wireless InSite

❑ XGTD

______________________________________

❑ Training

❑ Other _____________________

Telephone: (________) _________________________

I am interested in utilizing the prod-

E-mail: ________________________________________

ucts and services of Remcom for the

following application(s):

I prefer to be contacted by the following

________________________________________

mean(s):

❑ E-mail

❑ Postal Mail

❑ Telephone

________________________________________

Please mail this completed form to Remcom, Inc., 315 S. Allen St., Suite 222, State College, PA 16801, or fax it to (814) 861-1308.

In the U.K., mail to Central Boulevard, Blythe Valley Park, Solihull, West Midlands, England, B90 8A, or fax it to 0870 351 7641.

Xsite