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Consistent fat suppression with compensated spectral‐spatial pulses
Author(s) -
Block Walter,
Pauly John,
Kerr Adam,
Nishimura Dwight
Publication year - 1997
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.1910380207
Subject(s) - excitation , signal (programming language) , computer science , physics , spiral (railway) , optics , nuclear magnetic resonance , materials science , acoustics , mathematics , quantum mechanics , programming language , mathematical analysis
Reliable fat suppression is especially important with fast imaging techniques such as echo‐planar (EPI), spiral, and fast spin‐echo (FSE) T 2 ‐weighted imaging. Spectral‐spatial excitation has a number of advantages over spectrally selective presaturation techniques, including better resilience to B 0 and B 1 , inhomogeneity. In this paper, a FSE sequence using a spectral‐spatial excitation pulse for superior fat suppression is presented. Previous problems maintaining the CPMG condition are solved using simple methods to accurately program radio‐frequency (RF) phase. Next an analysis shows how B 0 eddy currents can reduce fat suppression effectiveness for spectral‐spatial pulses designed for conventional gradient systems. Three methods to compensate for the degradation are provided. Both the causes of the degradation and the compensation techniques apply equally to gradient‐recalled applications using these pulses. These problems do not apply to pulses designed for high‐speed gradient systems. The spectral‐spatial FSE sequence delivers clinically lower fat signal with better uniformity than spectrally selective pre‐saturation techniques.