Premium
Contrast behavior and relaxation effects of conventional and hyperecho‐turbo spin echo sequences at 1.5 and 3 T
Author(s) -
Weigel Matthias,
Hennig Juergen
Publication year - 2006
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.20816
Subject(s) - flip angle , spin echo , fast spin echo , contrast (vision) , specific absorption rate , nuclear magnetic resonance , formalism (music) , echo (communications protocol) , echo time , physics , relaxation (psychology) , computer science , magnetic resonance imaging , optics , telecommunications , medicine , art , musical , computer network , antenna (radio) , visual arts , radiology , social psychology , psychology
To overcome specific absorption rate (SAR) limitations of spin‐echo‐based MR imaging techniques, especially at (ultra) high fields, rapid acquisition relaxation enhancement/TSE (turbo spin echo)/fast spin echo sequences in combination with constant or variable low flip angles such as hyperechoes and TRAPS (hyperTSE) have been introduced. Due to the multiple spin echo and stimulated echo pathways involved in the signal formation, the contrast behavior of such sequences depends on both T 2 and T 1 relaxation times. In this work, constant and various variable flip angle sequences were analyzed in a volunteer study. It is demonstrated that a single effective echo time parameter TE eff can be calculated that accurately describes the overall T 2 weighted image contrast. TE eff can be determined by means of the extended phase graph concept and is practically independent of field strength. Using the described formalism, the contrast of any TSE sequence can be predicted. HyperTSE sequences are demonstrated to show a robust and well‐defined T 2 contrast allowing clinical routine MRI to be performed with SAR reductions of typically at least 70%. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.