title: Water-selective excitation of short T2 species with binomial pulses.
abstract: OBJECTIVE
  For imaging of fibrous musculoskeletal components, ultra-short echo time methods are often combined with fat suppression. Due to the increased chemical shift, spectral excitation of water might become a favorable option at ultra-high fields. Thus, this study aims to compare and explore short binomial excitation schemes for spectrally selective imaging of fibrous tissue components with short transverse relaxation time (T2 ).
  
  
  METHODS
  Water selective 1-1-binomial excitation is compared with nonselective imaging using a sub-millisecond spoiled gradient echo technique for in vivo imaging of fibrous tissue at 3T and 7T.
  
  
  RESULTS
  Simulations indicate a maximum signal loss from binomial excitation of approximately 30% in the limit of very short T2 (0.1 ms), as compared to nonselective imaging; decreasing rapidly with increasing field strength and increasing T2 , e.g., to 19% at 3T and 10% at 7T for T2 of 1 ms. In agreement with simulations, a binomial phase close to 90° yielded minimum signal loss: approximately 6% at 3T and close to 0% at 7T for menisci, and for ligaments 9% and 13%, respectively.
  
  
  CONCLUSIONS
  Overall, for imaging of short-lived T2 components, short 1-1 binomial excitation schemes prove to offer marginal signal loss especially at ultra-high fields with overall improved scanning efficiency.
authors.affiliation: Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland.
authors.forename: Xeni
authors.initials: X
authors.lastname: Deligianni
authors.forename: Peter
authors.initials: P
authors.lastname: Bär
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Oliver
authors.initials: O
authors.lastname: Bieri
mesh_terms: D000273:Adipose Tissue; D001834:Body Water; D003198:Computer Simulation; D003238:Connective Tissue / Q000033:anatomy & histology*; D064368:Healthy Volunteers; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007717:Knee / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*
keywords: binomial pulses; musculoskeletal imaging; short T2; ultra high fields; variable echo time; water excitation