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In‐plane velocity encoding with coherent steady‐state imaging
Author(s) -
Grinstead John,
Sinha Shantanu
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.20526
Subject(s) - signal (programming language) , physics , encoding (memory) , tracking (education) , vector field , nuclear magnetic resonance , sensitivity (control systems) , steady state (chemistry) , phase (matter) , plane (geometry) , optics , flow velocity , signal to noise ratio (imaging) , flow (mathematics) , computational physics , mathematics , chemistry , computer science , artificial intelligence , geometry , mechanics , programming language , psychology , pedagogy , quantum mechanics , electronic engineering , engineering
Standard phase‐contrast flow quantification (PC‐FQ) using radiofrequency (RF) spoiled steady‐state (SS) incoherent gradient‐echo sequences have a relatively low signal‐to‐noise ratio (SNR). Unspoiled SS coherent (SSC) gradient‐echo sequences have a higher intrinsic SNR and are T 2 / T 1 weighted so that blood has a relatively large signal compared to other tissues. An SSC sequence that was modified to allow in‐plane velocity encoding is presented. Velocity encoding was achieved by inverting the readout gradients. This offers the benefit that there is no resultant increase in repetition time (TR), which avoids increased sensitivity to off‐resonance artifacts when conventional velocity‐encoding methods using separate velocity‐encoding gradients are extended to SSC sequences. The results of standard PC‐FQ and the new method from in vitro experiments of constant and sinusoidal flow, and in vivo imaging of the carotid artery were compared. Vector field maps and paths obtained from particle‐tracking calculations based on the velocity‐encoded images were used to visualize the velocity data. The technique has the potential to increase the precision of PC‐FQ measurements. Magn Reson Med 54:138–145, 2005. © 2005 Wiley‐Liss, Inc.