title: B(0) homogeneity throughout the monkey brain is strongly improved in the sphinx position as compared to the supine position.
abstract: 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.
authors.affiliation: Comissariat à l'energie atomique, Service hospitalier Frédéric Joliot, 4 Place du Général Leclerc, 91401 Orsay, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Valette
authors.forename: Martine
authors.initials: M
authors.lastname: Guillermier
authors.forename: Fawzi
authors.initials: F
authors.lastname: Boumezbeur
authors.forename: Cyril
authors.initials: C
authors.lastname: Poupon
authors.forename: Alexis
authors.initials: A
authors.lastname: Amadon
authors.forename: Philippe
authors.initials: P
authors.lastname: Hantraye
authors.forename: Vincent
authors.initials: V
authors.lastname: Lebon
mesh_terms: D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D008252:Macaca fascicularis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011187:Posture; D016683:Supine Position