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Minimum envelope roughness pulse design for reduced amplifier distortion in parallel excitation
Author(s) -
Grissom William A.,
Kerr Adam B.,
Stang Pascal,
Scott Greig C.,
Pauly John M.
Publication year - 2010
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.22512
Subject(s) - amplifier , excitation , waveform , distortion (music) , pulse (music) , computer science , optics , nonlinear distortion , parallel communication , pulse shaping , nonlinear system , physics , telecommunications , bandwidth (computing) , radar , laser , quantum mechanics , transmission (telecommunications) , detector
Parallel excitation uses multiple transmit channels and coils, each driven by independent waveforms, to afford the pulse designer an additional spatial encoding mechanism that complements gradient encoding. In contrast to parallel reception, parallel excitation requires individual power amplifiers for each transmit channel, which can be cost prohibitive. Several groups have explored the use of low‐cost power amplifiers for parallel excitation; however, such amplifiers commonly exhibit nonlinear memory effects that distort radio frequency pulses. This is especially true for pulses with rapidly varying envelopes, which are common in parallel excitation. To overcome this problem, we introduce a technique for parallel excitation pulse design that yields pulses with smoother envelopes. We demonstrate experimentally that pulses designed with the new technique suffer less amplifier distortion than unregularized pulses and pulses designed with conventional regularization. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.