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Enhanced phase‐sensitive SSFP reconstruction for fat‐water separation in phased‐array acquisitions
Author(s) -
Yilmaz Ozgur,
Saritas Emine Ulku,
Çukur Tolga
Publication year - 2016
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.25138
Subject(s) - phased array , phase (matter) , separation (statistics) , steady state free precession imaging , materials science , environmental science , biomedical engineering , computer science , medicine , chemistry , radiology , magnetic resonance imaging , telecommunications , organic chemistry , machine learning , antenna (radio)
Purpose 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. Materials and Methods 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). Results 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). Conclusion 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.