title: Half radiofrequency pulse excitation with a dedicated prescan to correct eddy current effect and gradient delay.
abstract: OBJECTIVE
  To improve the slice profile of the half radiofrequency (RF) pulse excitation and image quality of ultrashort echo time (UTE) imaging by compensating for an eddy current effect.
  
  
  METHODS
  The dedicated prescan has been developed to measure the phase accumulation due to eddy currents induced by the slice-selective gradient. The prescan measures two one-dimensional excitation k-space profiles, which can be acquired with a readout gradient in the slice-selection direction by changing the polarity of the slice-selective gradient. The time shifts due to the phase accumulation in the excitation k-space were calculated. The time shift compensated for the start time of the slice-selective gradient. The total prescan time was 6-15 s. The slice profile and the UTE image with the half RF pulse excitation were acquired to evaluate the slice selectivity and the image quality.
  
  
  RESULTS
  Improved slice selectivity was obtained. The simple method proposed in this paper can eliminate eddy current effect. Good UTE images were obtained.
  
  
  CONCLUSIONS
  The slice profile of the half RF pulse excitation and the image quality of UTE images have been improved by using a dedicated prescan. This method has a possibility that can improve the image quality of a clinical UTE imaging.
authors: Molecular Imaging Center, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan. takayuki.abe.mri@gmail.com
authors: Takayuki
authors: T
authors: Abe
mesh_terms: D016477:Artifacts; D004553:Electric Conductivity; D006801:Humans; D007717:Knee; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011846:Radio Waves; D013997:Time Factors