title: Four dimensional spectral-spatial fat saturation pulse design.
abstract: OBJECTIVE
  The conventional spectrally selective fat saturation pulse may perform poorly with inhomogeneous amplitude of static (polarizing) field (B0 ) and/or amplitude of (excitation) radiofrequency field (B1 ) fields. We propose a four dimensional spectral-spatial fat saturation pulse that is more robust to B0/B1 inhomogeneity and also shorter than the conventional fat saturation pulse.
  
  
  BACKGROUND
  The proposed pulse is tailored for local B0 inhomogeneity, which avoids the need of a sharp transition band in the spectral domain, so it improves both performance and pulse length. Furthermore, it can also compensate for B1 inhomogeneity. The pulse is designed sequentially by small-tip-angle approximation design and an automatic rescaling procedure.
  
  
  METHODS
  The proposed method is compared to the conventional fat saturation in phantom experiments and in vivo knee imaging at 3 T for both single-channel and parallel excitation versions.
  
  
  RESULTS
  Compared to the conventional method, the proposed method produces superior fat suppression in the presence of B0 and B1 inhomogeneity and reduces pulse length by up to half of the standard length.
  
  
  CONCLUSIONS
  The proposed four dimensional spectral-spatial fat saturation suppresses fat more robustly with shorter pulse length than the conventional fat saturation in the presence of B0 and B1 inhomogeneity.
authors.affiliation: Biomedical Engineering Department, The University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhao
authors.forename: Jon-Fredrik
authors.initials: JF
authors.lastname: Nielsen
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Noll
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007719:Knee Joint / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013382:Subtraction Technique
keywords: B0 inhomogeneity; B1 inhomogeneity; fat saturation; parallel excitation; pulse design; spectral-spatial pulse