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An MRI method for measuring T 2 in the presence of static and RF magnetic field Inhomogeneities
Author(s) -
Yablonskiy Dmitriy A.,
Haacke E. Mark
Publication year - 1997
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.1910370611
Subject(s) - spin echo , magnetostatics , nuclear magnetic resonance , pulse sequence , magnetic field , signal (programming language) , physics , echo (communications protocol) , relaxation (psychology) , gradient echo , magnetic resonance imaging , field (mathematics) , sampling (signal processing) , pulse (music) , physics of magnetic resonance imaging , spin (aerodynamics) , computational physics , optics , magnetic resonance microscopy , computer science , mathematics , computer network , detector , psychology , social psychology , quantum mechanics , radiology , programming language , medicine , pure mathematics , thermodynamics
A magnetic resonance imaging method for measuring the T 2 relaxation time constant is proposed. It is based on the assumption that, under very general conditions, the MR signal near a spin echo has a special symmetry arising from the refocusing nature of the 180° RF pulse. A gradient echo sampling of the spin echo (GESSE) sequence is implemented to evaluate T 2 by collecting multiple gradient echoes before and after the spin echo. This approach is a modification of the GESFIDE sequence proposed by Ma and Wehrli. However, our approach compares images that are not separated by any RF pulses and, as a result, is insensitive to slice profile imperfections. In addition, the calculated T 2 value does not rely on any special assumptions about the MRI signal behavior in the presence of an inhomogeneous static magnetic field and, hence, is insensitive to the presence of static magnetic field inhomogeneities.