Premium
Motion‐insensitive determination of B 1 + amplitudes based on the bloch‐siegert shift in single voxels of moving organs including the human heart
Author(s) -
Dokumaci Ayse Sila,
Pouymayou Bertrand,
Kreis Roland,
Boesch Chris
Publication year - 2016
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.25763
Subject(s) - amplitude , physics , voxel , imaging phantom , nuclear magnetic resonance , pulse (music) , fermi gamma ray space telescope , computational physics , optics , condensed matter physics , computer science , artificial intelligence , detector
Purpose To reliably determine the amplitude of the transmit radiofrequency ( B 1 + ) field in moving organs like the liver and heart, where most current techniques are usually not feasible. MethodsB 1 +field measurement based on the Bloch‐Siegert shift induced by a pair of Fermi pulses in a double‐triggered modified Point RESolved Spectroscopy (PRESS) sequence with motion‐compensated crusher gradients has been developed. Performance of the sequence was tested in moving phantoms and in muscle, liver, and heart of six healthy volunteers each, using different arrangements of transmit/receive coils. ResultsB 1 +determination in a moving phantom was almost independent of type and amplitude of the motion and agreed well with theory. In vivo, repeated measurements led to very small coefficients of variance (CV) if the amplitude of the Fermi pulse was chosen above an appropriate level (CV in muscle 0.6%, liver 1.6%, heart 2.3% with moderate amplitude of the Fermi pulses and 1.2% with stronger Fermi pulses). Conclusion The proposed sequence shows a very robust determination ofB 1 +in a single voxel even under challenging conditions (transmission with a surface coil or measurements in the heart without breath‐hold). Magn Reson Med 75:1867–1874, 2016. © 2015 Wiley Periodicals, Inc.