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Partial RF echo‐planar imaging with the FAISE method. II. Contrast equivalence with spin‐echo sequences
Author(s) -
Melki Philippe S.,
Jolesz Ferenc A.,
Mulkern Robert V.
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.1910260213
Subject(s) - spin echo , echo (communications protocol) , nuclear magnetic resonance , contrast (vision) , echo time , physics , magnetization transfer , multislice , fast spin echo , pulse sequence , signal (programming language) , chemistry , magnetic resonance imaging , computer science , optics , medicine , computer network , radiology , programming language
The fast acquisition interleaved spin‐echo (FAISE) sequence and its dual‐echo version (DEFAISE) are partial RF echo‐planar methods which utilize a specific phase‐encode reordering algorithm to manipulate T 2 contrast via an operator‐controlled pseudo‐echo time, pTE. The repetition time, TR, between successive applications of the Carr‐Purcell‐ Meiboom‐Gill (CPMG) echo trains used in FAISE may be reduced to introduce T 1 weighting. To quantitatively determine the extent to which FAISE T 1 and T 2 contrast characteristics agree with spin‐echo methods, signal intensities from FAISE acquisitions were compared with signal intensities from equivalent CPMG acquisitions. In phantoms and in human heads, the contrast Characteristics of FAISE are found to be highly correlated with that obtained with equivalent CPMG sequences. However, conventional SE sequences generally utilize longer echo spacings than employed with FAISE/CPMG. Thus, echo spacing‐dependent mechanisms such as spin‐spin coupling and magnetic susceptibility lead to some differences in contrast between conventional SE and FAISE. Finally, FAISE appears to be more sensitive to magnetization transfer effects than conventional SE sequences since more off‐resonance irradiation is applied to individual slices during multislice acquisitions.