Fast proton spectroscopic imaging using steady-state free precession methods

✍ Scribed by Wolfgang Dreher; Christian Geppert; Matthias Althaus; Dieter Leibfritz

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 522 KB
• Volume: 50
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.10548

✦ Synopsis

Abstract

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.