title: Improved frequency selective fat suppression in the posterior neck with tissue susceptibility matched pyrolytic graphite foam.
abstract: OBJECTIVE
  To demonstrate improved frequency selective fat suppression in MRI using a magnetic susceptibility matching foam by reducing B0 inhomogeneities induced within the body by air-tissue interfaces.
  
  
  METHODS
  Flexible pyrolytic graphite (PG) composite foam was tailored to match the magnetic susceptibility of human tissue and was shaped to surround the cervical spine region. Field maps and frequency selective fat suppressed T1 -weighted FLASH images were acquired at 3 Tesla in both phantoms and six healthy necks.
  
  
  RESULTS
  B0 field uniformity was shimmed to a target critical threshold of 1 ppm for fat suppression. The percentage of voxels in the phantom that did not achieve the critical threshold was reduced from 64% without the PG foam to only 1% with the foam. A similar decrease from 16% to 2% was observed in the in vivo region of interest.
  
  
  CONCLUSIONS
  PG foam improved B0 field uniformity by moving air-tissue field gradients outside of the neck where they cannot cause MRI artifacts. The PG foams consistently mitigated signal dropout, improved overall SNR, and enabled more robust frequency selective fat suppression.
authors.affiliation: Berkeley/UCSF Bioengineering Joint Graduate Group, Berkeley, California, USA; Department of Bioengineering, University of California, Berkeley, Berkeley, California, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Lee
authors.forename: Caroline
authors.initials: C
authors.lastname: Jordan
authors.forename: Pamela
authors.initials: P
authors.lastname: Tiet
authors.forename: Carlos
authors.initials: C
authors.lastname: Ruiz
authors.forename: Jeff
authors.initials: J
authors.lastname: McCormick
authors.forename: Kevin
authors.initials: K
authors.lastname: Phuong
authors.forename: Brian
authors.initials: B
authors.lastname: Hargreaves
authors.forename: Steven
authors.initials: S
authors.lastname: Conolly
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D000704:Analysis of Variance; D016477:Artifacts; D002244:Carbon; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009333:Neck / Q000033:anatomy & histology*; D019047:Phantoms, Imaging; D012016:Reference Values; D055815:Young Adult
chemical_list: C009139:pyrolytic carbon; D002244:Carbon
keywords: fat suppression; magnetic susceptibility; passive shim; pyrolytic graphite