title: Enhanced phase-sensitive SSFP reconstruction for fat-water separation in phased-array acquisitions.
abstract: To propose and assess a method to improve the reliability of phase-sensitive fat-water separation for phased-array balanced steady-state free precession (bSSFP) acquisitions. Phase-sensitive steady-state free precession (PS-SSFP) is an efficient fat-water separation technique that detects the phase difference between neighboring bands in the bSSFP magnetization profile. However, large spatial variations in the sensitivity profiles of phased-array coils can lead to noisy phase estimates away from the coil centers, compromising tissue classification.
  
  
  
  We first perform region-growing phase correction in individual coil images via unsupervised selection of a fat-voxel seed near the peak of each coil's sensitivity profile. We then use an optimal linear combination of phase-corrected images to segregate fat and water signals. The proposed method was demonstrated on noncontrast-enhanced SSFP angiograms of the thigh, lower leg, and foot acquired at 1.5T using an 8-channel coil. Individual coil PS-SSFP with a common seed selection for all coils, individual coil PS-SSFP with coil-wise seed selection, PS-SSFP after coil combination, and IDEAL reconstructions were also performed. Water images reconstructed via PS-SSFP methods were compared in terms of the level of fat suppression and the similarity to reference IDEAL images (signed-rank test).
  
  
  
  While tissue misclassification was broadly evident across regular PS-SSFP images, the proposed method achieved significantly higher levels of fat suppression (P < 0.005) and increased similarity to reference IDEAL images (P < 0.005).
  
  
  
  The proposed method enhances fat-water separation in phased-array acquisitions by producing improved phase estimates across the imaging volume. J. Magn. Reson. Imaging 2016;44:148-157.
authors.affiliation: Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.|National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey.
authors.forename: Ozgur
authors.initials: O
authors.lastname: Yilmaz
authors.affiliation: Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.|National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey.|Neuroscience Program, Bilkent University, Ankara, Turkey.
authors.forename: Emine Ulku
authors.initials: EU
authors.lastname: Saritas
authors.affiliation: Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.|National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey.|Neuroscience Program, Bilkent University, Ankara, Turkey.
authors.forename: Tolga
authors.initials: T
authors.lastname: Çukur
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000328:Adult; D000465:Algorithms; D001834:Body Water / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: SSFP; fat-water separation; phase sensitive; phased array; weighted combination