Improved encoding pulses for Bloch-Siegert B1(+) mapping.

Jankiewicz M, Gore JC, Grissom WA
J Magn Reson. 2013 226: 79-87

PMID: 23220183 · PMCID: PMC3561618 · DOI:10.1016/j.jmr.2012.11.004

A new family of optimized encoding pulses for Bloch-Siegert (BS)


mapping is introduced, as well as an algorithm to design them. The pulses are designed by numerical maximization of BS sequence sensitivity, subject to constraints that ensure low on-resonance excitation. The pulses are in all cases characterized by a constant envelope and U-shaped frequency sweep. They are validated in simulations, 7T in vivo experiments, and an experiment to measure their on-resonance excitation, and are compared to a Fermi pulse conventionally used in the BS method. The pulses are shown to produce larger phase shifts in a shorter time and with lower on-resonance excitation than the Fermi pulse, which results in lower SAR and improved


accuracy in areas of the body with large main field inhomogeneities.

Copyright © 2012 Elsevier Inc. All rights reserved.

MeSH Terms (9)

Algorithms Brain Mapping Computer Simulation Electromagnetic Fields Humans Image Enhancement Magnetic Resonance Imaging Phantoms, Imaging Reproducibility of Results

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