T(2) selectivity: comparison between different kinds of RF pulses.
Techniques allowing characterization of specific T(2) species are used to perform MR imaging of structures whose signal intensity is poor on conventional methodologies. T(2)-selective pulses can be used to discriminate signals from tissues with different T(2) values. In case of soliton pulses, the magnetization from all the T(2) species is inverted, with the exception of specific T(2) structures which have both the longitudinal and the transverse magnetization nulled on resonance. Solitons have the drawback of being very long even if the selected T(2) value is in the order of tens of milliseconds. The aim of this paper is to examine whether it is possible to use pulses shorter then solitons keeping their T(2) selectivity, that is keeping null longitudinal magnetization, while accepting some residual transverse magnetization for structures with the selected T(2). Different kinds of inversion pulses were generated, all to select the same T(2) species. Pulses performance was analyzed by studying the dependence of the residual transverse magnetization on resonance from the length of the pulse. An exponential relationship between transverse magnetization and pulse length was found, which was not dependent on the pulse type.
Klose
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U
Division of Experimental NMR of CNS, Department of Neuroradiology, University of Tübingen, Hoppe-Seyler Strasse 3, Tübingen, D-72076, Germany.
Raddi
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A