title: Lipid suppression for brain MRI and MRSI by means of a dedicated crusher coil.
abstract: OBJECTIVE
  Lipid suppression in MR brain imaging and spectroscopy has been a long-standing problem for which various techniques have been developed. Most methods are based on inversion recovery or spatially or spectrally selective excitation of the lipid signal followed by dephasing. All techniques require additional RF pulses, gradient crushers and delays, which increase the duration and complexity of sequences. In addition, the lipid signal is poorly shimmed, and is composed of different resonance frequencies that have different relaxation properties.
  
  
  METHODS
  In this work, a novel approach for suppression of extra cranial lipids is presented, by means of an outer volume crusher coil. It is based on the principle of surface spoiling gradients, which generate a very local and inhomogeneous magnetic field in the outer layer of the head, and thereby destroys the phase coherence of the extra cranial signals.
  
  
  RESULTS
  Dephasing of the signal can be incorporated in almost any sequence because it requires only a short pulse of the coil, and does not require additional RF pulses or delays. Examples of lipid suppression are shown in both gradient echo imaging and spectroscopic imaging.
  
  
  CONCLUSIONS
  Outer volume crushing allows for simple fat suppression and boosts scanning efficiency, which is particularly beneficial at ultra-high field strengths.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, The Netherlands.
authors.forename: Vincent O
authors.initials: VO
authors.lastname: Boer
authors.affiliation: Department of Radiology, University Medical Center Utrecht, The Netherlands.
authors.forename: Tessa
authors.initials: T
authors.lastname: van de Lindt
authors.affiliation: Department of Radiology, University Medical Center Utrecht, The Netherlands.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Luijten
authors.affiliation: Department of Radiology, University Medical Center Utrecht, The Netherlands.
authors.forename: Dennis W J
authors.initials: DW
authors.lastname: Klomp
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D001923:Brain Chemistry; D001931:Brain Mapping; D004867:Equipment Design; D064368:Healthy Volunteers; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*
keywords: 7T; MRSI; high field; lipid suppression; spectroscopic imaging