B(0) homogeneity throughout the monkey brain is strongly improved in the sphinx position as compared to the supine position.
OBJECTIVE
To map B(0) distortions throughout the monkey brain in the two positions commonly used for NMR studies (the prone sphinx position and the supine position) in order to test the hypothesis that B(0) homogeneity in the sphinx position is significantly improved as compared to the supine position.


METHODS
Three macaque monkeys were installed in the two positions in a 3T whole-body MR system without shim correction. B(0) maps were acquired using a 3D gradient double-echo sequence, and field dispersion throughout the brain was quantified. In addition, field maps and localized (1)H spectra were acquired after first-order shimming was performed.


RESULTS
The field maps collected in the three animals were highly reproducible. B(0) dispersion throughout the brain was typically two to three times greater in the supine position than in the sphinx position. Although first-order shimming proved relatively more efficient in the supine position, B(0) dispersion still remained greater in the supine than in the sphinx position. These findings can be explained by the thickness of outer brain tissues.


CONCLUSIONS
This work demonstrates that the sphinx position is highly favorable in terms of B(0) homogeneity. It should prove useful for NMR exploration of the monkey brain, particularly at high fields where B(0) inhomogeneity associated with susceptibility artifacts is increased.
Valette
Julien
J
Comissariat à l'energie atomique, Service hospitalier Frédéric Joliot, 4 Place du Général Leclerc, 91401 Orsay, France.
Guillermier
Martine
M
Boumezbeur
Fawzi
F
Poupon
Cyril
C
Amadon
Alexis
A
Hantraye
Philippe
P
Lebon
Vincent
V
D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D008252:Macaca fascicularis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011187:Posture; D016683:Supine Position