Induced magnetic force in human heads exposed to 4 T MRI.
OBJECTIVE
To map the distribution of the magnetic force induced in the human head during magnetic resonance imaging (MRI) at 4 T for a large group of healthy volunteers.


METHODS
The magnetic field distribution in the head of 100 men and 18 women was mapped using phase mapping techniques. Statistical parametric mapping methods using a family-wise error (FWE) corrected threshold P < 0.05 and region-of-interest analyses were used to assess the significance of the results.


RESULTS
Eyeballs, orbitofrontal and temporal cortices, subcallosal gyrus, anterior cingulate, midbrain, and brainstem (pons) are the brain regions most susceptible to magnetic force. The strength of the magnetic force density in the head was lower than 11.5 +/- 5.3 N/m(3) (right eyeball). The strength of the magnetic force density induced in occipital cortex varied linearly with the x-rotation (pitch) angle.


CONCLUSIONS
We found that the induced magnetic force is highly significant in the eyeballs, orbitofrontal and temporal cortices, subcallosal gyrus, anterior cingulate as well as midbrain and brainstem (pons), regardless of subjects' age or gender. The maximum induced magnetic force was 6 x 10(5) times weaker than the gravitational force; thus, biological effects of the magnetic force during imaging are not expected to be significant.
Wang
Ruiliang
R
Medical Department, Brookhaven National Laboratory, Upton, New York 11973, USA. rlwang@bnl.gov
Wang
Gene-Jack
GJ
Goldstein
Rita Z
RZ
Caparelli
Elisabeth C
EC
Volkow
Nora D
ND
Fowler
Joanna S
JS
Tomasi
Dardo
D
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000473:pathology / Q000528:radiation effects; D004574:Electromagnetic Fields; D005260:Female; D006112:Gravitation; D006257:Head / Q000528:radiation effects*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects / Q000379:methods*; D008280:Magnetics; D008297:Male; D008875:Middle Aged