High tip angle approximation based on a modified Bloch-Riccati equation

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DOIResolve DOI: http://doi.org/10.1002/mrm.23270
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TypeArticle
Journal titleMagnetic Resonance in Medicine
ISSN07403194
Volume67
Issue2
Pages339343; # of pages: 5
SubjectBloch equation; flip angle dynamics; high tip angle approximation
AbstractWhen designing a radio-frequency pulse to produce a desired dependence of magnetization on frequency or position, the small flip angle approximation is often used as a first step, and a Fourier relation between pulse and transverse magnetization is then invoked. However, common intuition often leads to linear scaling of the resulting pulse so as to produce a larger flip angle than the approximation warrants—with surprisingly good results. Starting from a modified version of the Bloch–Riccati equation, a differential equation in the flip angle itself, rather than in magnetization, is derived. As this equation has a substantial linear component that is an instance of Fourier's equation, the intuitive approach is seen to be justified. Examples of the accuracy of this higher tip angle approximation are given for both constant- and variable-phase pulses
Publication date
LanguageEnglish
AffiliationNRC Institute for Biodiagnostics; National Research Council Canada
Peer reviewedYes
NPARC number21268225
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Record identifier96fd1253-9a4b-40e8-9218-196f38f80f6a
Record created2013-06-06
Record modified2016-05-09
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