title: Non-Cartesian balanced steady-state free precession pulse sequences for real-time cardiac MRI.
abstract: OBJECTIVE
  To develop a new spiral-in/out balanced steady-state free precession (bSSFP) pulse sequence for real-time cardiac MRI and compare it with radial and spiral-out techniques.
  
  
  METHODS
  Non-Cartesian sampling strategies are efficient and robust to motion and thus have important advantages for real-time bSSFP cine imaging. This study describes a new symmetric spiral-in/out sequence with intrinsic gradient moment compensation and SSFP refocusing at TE = TR/2. In vivo real-time cardiac imaging studies were performed to compare radial, spiral-out, and spiral-in/out bSSFP pulse sequences. Furthermore, phase-based fat/water separation taking advantage of the refocusing mechanism of the spiral-in/out bSSFP sequence was also studied.
  
  
  RESULTS
  The image quality of the spiral-out and spiral-in/out bSSFP sequences was improved with off-resonance and k-space trajectory correction. The spiral-in/out bSSFP sequence had the highest signal-to-noise ratio (SNR), contrast-to-noise ratio, and image quality ratings, with spiral-out bSSFP sequence second in each category and the radial bSSFP sequence third. The spiral-in/out bSSFP sequence provides separated fat and water images with no additional scan time.
  
  
  CONCLUSIONS
  In this study, a new spiral-in/out bSSFP sequence was developed and tested. The superiority of spiral bSSFP sequences over the radial bSSFP sequence in terms of SNR and reduced artifacts was demonstrated in real-time MRI of cardiac function without image acceleration.
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Xue
authors.initials: X
authors.lastname: Feng
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.|Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, Virginia, USA.|Department of Medicine, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Salerno
authors.affiliation: Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, Virginia, USA.|Department of Medicine, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kramer
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.|Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Craig H
authors.initials: CH
authors.lastname: Meyer
mesh_terms: D000328:Adult; D000465:Algorithms; D062485:Breath Holding; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D055425:Respiratory-Gated Imaging Techniques; D059629:Signal-To-Noise Ratio; D055815:Young Adult
keywords: bSSFP; fat-water separation; real-time cardiac imaging; spiral; spiral-in/out