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Effects of RF amplifier distortion on selective excitation and their correction by prewarping
Author(s) -
Chan Frandics,
Pauly John,
Macovski Albert
Publication year - 1992
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.1910230204
Subject(s) - distortion (music) , amplifier , excitation , rf power amplifier , spins , radio frequency , nonlinear distortion , modulation (music) , physics , pulse (music) , phase distortion , materials science , nuclear magnetic resonance , nonlinear system , rf probe , phase (matter) , optics , optoelectronics , computer science , acoustics , telecommunications , detector , cmos , quantum mechanics , condensed matter physics
In a magnetic resonance imaging system, an RF power amplifier is employed to boost an RF pulse to sufficient strength to excite the nuclear spins in a subject. The nonideal behavior of this amplifier distorts a selective‐excitation pulse, and this distortion in turn degrades the slice profile. We have found two types of nonideal behavior particularly troublesome: nonlinearity and incidental phase modulation. One of their effects is the introduction of an unwanted “skirt” in the out‐of‐slice region of a slice profile. We present an effective method of correction in which a selective‐excitation pulse is prewarped to compensate for the distortion. © 1992 Academic Press, Inc.