Abstract
Object
A selective-excitation radiofrequency (RF) pulse that uses hard pulses composed of a sequence of composite pulses with positive and negative phases (P/N pulse) is proposed herein. Because the amplitude of the RF signal is unchanged during the excitation, RF amplification can be accomplished using a nonlinear RF power amplifier (i.e., class C or D type).
Materials and methods
In this article, Fourier series have been first used to analyze the equivalence between the proposed P/N pulse and the conventional soft pulse on selective excitation. Subsequently, computer simulations based on density-matrix theory are used to compare the excitation profiles of both the soft and the P/N pulses.
Results
The excitation profiles of the P/N pulses have been measured experimentally through a home-built 0.3-T magnetic resonance imaging (MRI) system. In addition, several slices of images have been obtained as proofs by using the multislice two-dimensional spin echo sequence through replacement of the conventional soft pulse by the proposed P/N pulse.
Conclusion
Because the perfect selectivity of the proposed P/N pulse, it can be used for imaging studies to improve the efficiency of amplification at the lowest cost.
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Ying, L., Jianqi, L. & Gengying, L. A novel selective-excitation RF pulse for magnetic resonance imaging. Magn Reson Mater Phy 21, 199–205 (2008). https://doi.org/10.1007/s10334-008-0111-9
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DOI: https://doi.org/10.1007/s10334-008-0111-9