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Errors in the measurements of T 2 using multiple‐echo MRI techniques. II. Effects of static field inhomogeneity
Author(s) -
Majumdar S.,
Orphanoudakis S. C.,
Gmitro A.,
O'Donnell M.,
Gore J. C.
Publication year - 1986
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.1910030410
Subject(s) - bloch equations , spin echo , imaging phantom , relaxation (psychology) , magnetostatics , field (mathematics) , pulse (music) , nuclear magnetic resonance , echo (communications protocol) , amplitude , spin (aerodynamics) , physics , magnetic resonance imaging , computational physics , computer science , magnetic field , optics , mathematics , medicine , psychology , social psychology , computer network , quantum mechanics , detector , pure mathematics , radiology , thermodynamics
The accurate estimation of the spin‐spin relaxation time T 2 is an important goal in magnetic resonance imaging particularly because it can be used for quantitative tissue characterization. The spin‐spin relaxation time T 2 may be estimated using multiecho pulse sequences, but the accuracy of the estimate is dependent on the fidelity of the spin‐echo amplitudes, which may be severely compromised by rf pulse and static field imper‐fections. In this paper, the effects of static field inhomogeneities are investigated. The propagation of the errors introduced by off‐resonance effects are analyzed through computer simulations and analytical solutions of the Bloch equations. A series of experiments performed on a simple tissue phantom using a whole‐body imaging system operating at 6.35 MHz corroborates the simulation and analytical results. For accurate measurements of T 2 using a whole‐body imaging system it is necessary to correct for these inhomogeneities. A correction scheme which would enable a more accurate estimate of T 2 is currently under investigation. © 1986 Academic Press, Inc.