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Displacement‐encoded cardiac MRI using cosine and sine modulation to eliminate (CANSEL) artifact‐generating echoes
Author(s) -
Epstein Frederick H.,
Gilson Wesley D.
Publication year - 2004
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.20232
Subject(s) - signal (programming language) , displacement (psychology) , artifact (error) , physics , nuclear magnetic resonance , dephasing , relaxation (psychology) , amplitude , modulation (music) , phase (matter) , trigonometric functions , acoustics , computer science , mathematics , optics , computer vision , geometry , medicine , psychology , quantum mechanics , psychotherapist , programming language
Displacement‐encoded imaging with stimulated echoes (DENSE) and harmonic phase imaging (HARP) employ 1‐1 spatial modulation of magnetization to cosine modulate the longitudinal magnetization as a function of position at end diastole. Later in the cardiac cycle they sample the cosine‐modulated signal and compute myocardial strain from the signal phase. The sampled signal generally includes three distinct echoes: 1) a displacement‐encoded stimulated echo, 2) the complex conjugate of the displacement‐encoded echo, and 3) an echo arising from T 1 relaxation. If the T 1 ‐relaxation and complex conjugate echoes are suppressed, then a phase image representing just the displacement‐encoded echo can be reconstructed. In the present study, the use of cosine and sine modulation to eliminate (CANSEL) the T 1 ‐relaxation and complex conjugate echoes was investigated. With the use of CANSEL, it was demonstrated that DENSE accurately measures through‐plane as well as in‐plane components of tissue motion. Also, DENSE with CANSEL artifact suppression can provide increased signal‐to‐noise ratio (SNR) secondary to reduced intravoxel dephasing by using relatively low displacement‐encoding frequencies. For applications that employ DENSE imaging with multiple acquisitions, the CANSEL technique can suppress artifact‐generating echoes without placing constraints on the displacement‐encoding frequency and direction. Magn Reson Med 52:774–781, 2004. © 2004 Wiley‐Liss, Inc.