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SAR‐reduced spin‐echo‐based Bloch–Siegert B 1 + mapping: BS‐SE‐BURST
Author(s) -
BasseLüsebrink Thomas Christian,
Kampf Thomas,
Fischer André,
Sturm Volker Jörg Friedrich,
Neumann Daniel,
Köstler Herbert,
Hahn Dietbert,
Stoll Guido,
Jakob Peter Michael
Publication year - 2012
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.23259
Subject(s) - specific absorption rate , excitation , physics , phase (matter) , nuclear magnetic resonance , pulse sequence , spin echo , echo (communications protocol) , sequence (biology) , pulse (music) , signal (programming language) , atomic physics , chemistry , optics , magnetic resonance imaging , computer science , telecommunications , medicine , computer network , biochemistry , quantum mechanics , detector , antenna (radio) , radiology , programming language
Fast and accurate B 1 + mapping is possible using phase‐based Bloch–Siegert (BS) methods. Importantly, the off‐resonant pulses needed for BS B 1 + mapping methods can easily be implemented in multiple MR sequences. BS‐based B 1 + mapping has thus been introduced for gradient echo (BS‐FLASH), spin‐echo (BS‐SE), and Carr, Purcell, Meiboom, Gill (CPMG)‐based multi‐SE and turbo‐SE sequences. When using SE and multi‐SE/turbo‐SE‐based BS sequences, however, the high intrinsic specific absorption rates must be considered in clinical situations. This study introduces a fast BS B 1 + mapping method based on a SE‐BURST sequence (BS‐SE‐BURST). With SE‐BURST sequences, multiple low‐magnitude excitation pulses are applied prior to the refocusing pulse. Thus, multiple and different phase‐encoded echoes can be acquired per excitation cycle. Compared with a SE sequence, this excitation strategy results in a similar signal‐to‐noise ratio (SNR) per unit time but with reduced specific absorption rate. The proposed BS‐SE‐BURST sequence was implemented on a conventional 3 T whole body MRI scanner and applied successfully. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.