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Accelerated imaging with segmented 2D pulses using parallel imaging and virtual coils.

Authors
  • Mullen, Michael1
  • Gutierrez, Alexander2
  • Kobayashi, Naoharu3
  • Haupt, Jarvis4
  • Garwood, Michael5
  • 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA.
  • 2 School of Mathematics, University of Minnesota, Minneapolis, MN, USA.
  • 3 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA.
  • 4 Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA.
  • 5 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA. Electronic address: [email protected]
Type
Published Article
Journal
Journal of Magnetic Resonance
Publisher
Elsevier
Publication Date
Aug 01, 2019
Volume
305
Pages
185–194
Identifiers
DOI: 10.1016/j.jmr.2019.07.001
PMID: 31302513
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Large magnetic field inhomogeneity can be a significant cause of spatial flip-angle variation when using ordinary, limited-bandwidth RF pulses. Multidimensional RF pulses are particularly sensitive to inhomogeneity due to their extended pulse length, which decreases their bandwidth. Previously, it was shown that, by breaking a 2D pulse into multiple undersampled k-space segments, the excitation bandwidth can be increased at the expense of increased imaging time. The present study shows how this increased imaging time can be offset by undersampling acquisition k-space in a phase-encoded dimension that is in the direction of excitation segmentation. Data from each segment are viewed as originating from "virtual receive coils" rather than multiple physical coils. The undersampled data are reconstructed using parallel imaging techniques (e.g. as in GRAPPA). The method was tested in vivo with brain imaging at both 3 T and 4 T, and used in conjunction with a 32-channel head coil and conventional GRAPPA on the 3 T data. Relationships with existing techniques and future applications are discussed. Copyright © 2019 Elsevier Inc. All rights reserved.

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