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Flow compensation in balanced SSFP sequences
Author(s) -
Bieri O.,
Scheffler K.
Publication year - 2005
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20619
Subject(s) - steady state free precession imaging , pairing , spins , flow (mathematics) , waveform , phase (matter) , precession , physics , sequence (biology) , imaging phantom , signal (programming language) , encoding (memory) , nuclear magnetic resonance , algorithm , computer science , acoustics , mechanics , optics , chemistry , artificial intelligence , magnetic resonance imaging , voltage , medicine , biochemistry , superconductivity , quantum mechanics , astronomy , radiology , programming language , condensed matter physics
In balanced steady‐state free precession (b‐SSFP) sequences, uncompensated first‐order moments of encoding gradients induce a nonconstant phase evolution for moving spins within the excitation train, resulting in signal loss and image artifacts. To restore these flow‐related phase perturbations, “pairing” of consecutive phase‐encoding (PE) steps is compared with a fully flow‐compensated sequence using compensating gradient waveforms along all three encoding directions. In volunteer studies, the quality of images acquired with the “pairing” technique was comparable to that of images obtained with the fully flow‐compensated technique, regardless of the selected view‐ordering scheme used for data acquisition. Nevertheless, the results of phantom experiments indicate that the pairing technique becomes ineffective at flow velocities exceeding roughly 0.5–1 m/s. Consequently, the additional scan time required to null the first gradient moments in a flow‐compensated b‐SSFP sequence makes the “pairing” technique preferable for applications in which slow to moderate flow velocities can be expected. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.