Characterization of B1 field focussing effects in magnetic resonance spectroscopy and imaging at 17.6 tesla

As Larmor frequencies for high-resolution NMR spectroscopy and microimaging approach 1 GHz, effects such as dielectric resonance and sample-induced spatial inhomogeneities in the radiofrequency transmission and reception fields become more prominent. These effects have been studied extensively for high field human imaging, but have received less attention in the areas of NMR spectroscopy and microimaging. Although the effects in small samples are not as pronounced as in large biological samples, the use of multiple-pulse spectroscopic and imaging sequences, for example, can exacerbate the intrinsic B1 inhomogeneities introduced by the sample. In this article, we show computational and analytical simulations as well as experimental data acquired at 17.6 tesla to study high frequency effects for high-resolution NMR, in vivo animal imaging, and microimaging of fixed tissue samples. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 27B: 8–16, 2005.

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