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Fast proton spectroscopic imaging using steady‐state free precession methods
Author(s) -
Dreher Wolfgang,
Geppert Christian,
Althaus Matthias,
Leibfritz Dieter
Publication year - 2003
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.10548
Subject(s) - steady state free precession imaging , nuclear magnetic resonance , signal (programming language) , precession , physics , signal to noise ratio (imaging) , proton , temporal resolution , spins , image resolution , steady state (chemistry) , chemistry , resolution (logic) , optics , magnetic resonance imaging , computer science , medicine , quantum mechanics , astronomy , artificial intelligence , radiology , programming language , condensed matter physics
Various pulse sequences for fast proton spectroscopic imaging (SI) using the steady‐state free precession (SSFP) condition are proposed. The sequences use either only the FID‐like signal S 1 , only the echo‐like signal S 2 , or both signals in separate but adjacent acquisition windows. As in SSFP imaging, S 1 and S 2 are separated by spoiler gradients. RF excitation is performed by slice‐selective or chemical shift‐selective pulses. The signals are detected in absence of a B 0 gradient. Spatial localization is achieved by phase‐encoding gradients which are applied prior to and rewound after each signal acquisition. Measurements with 2D or 3D spatial resolution were performed at 4.7 T on phantoms and healthy rat brain in vivo allowing the detection of uncoupled and J‐coupled spins. The main advantages of SSFP based SI are the short minimum total measurement time (T min ) and the high signal‐to‐noise ratio per unit measurement time (SNR t ). The methods are of particular interest at higher magnetic field strength B 0 , as TR can be reduced with increasing B 0 leading to a reduced T min and an increased SNR t . Drawbacks consist of the limited spectral resolution, particularly at lower B 0 , and the dependence of the signal intensities on T 1 and T 2 . Further improvements are discussed including optimized data processing and signal detection under oscillating B 0 gradients leading to a further reduction in T min . Magn Reson Med 50:453–460, 2003. © 2003 Wiley‐Liss, Inc.