Please use this identifier to cite or link to this item: https://ahro.austin.org.au/austinjspui/handle/1/34044
Title: What can we gain from subpopulation universal pulses? A simulation-based study.
Austin Authors: Tyshchenko, Igor;Lévy, Simon;Jin, Jin;Tahayori, Bahman;Blunck, Yasmin;Johnston, Leigh A
Affiliation: Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia.;Melbourne Brain Centre Imaging Unit, The University of Melbourne, Parkville, Victoria, Australia.
MR Research Collaborations, Siemens Healthcare Pty Ltd, Australia.
The Florey Institute of Neuroscience and Mental Health
Melbourne Brain Centre Imaging Unit, The University of Melbourne, Parkville, Victoria, Australia.
Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia.;Melbourne Brain Centre Imaging Unit, The University of Melbourne, Parkville, Victoria, Australia.
Issue Date: Feb-2024
Date: 2023
Publication information: Magnetic Resonance in Medicine 2024-02; 91(2)
Abstract: The aim of the study was to explore a novel methodology for designing universal pulses (UPs) that balances the benefits of a calibration-free approach with subject-specific online pulse design. The proposed method involves segmenting the population into subpopulations with variability in anatomical shapes and positions reduced to 75%, 50%, and 25% of their original values while keeping the mean values unchanged. An additional 25% extreme case with a large volume of interest and shifted position was included. For each group, a 5kT-points universal inversion pulse was designed and assessed by the normalized root mean square error (NRMSE) on the target longitudinal magnetization profile. The performance was compared to the conventional one-size-fits-all approach. A total of 132 electromagnetic simulations were executed to generate representative anatomies and specific absorption rate (SAR) distributions in a three-dimensional parameter space comprised of head breadth, head length, and Y-shift. The 99.9th percentile on the peak local SAR distribution was utilized to establish an intersubject variability safety margin. UPs designed for subpopulations with decreased head shape and position variability reduced the anatomical safety margin by up to 20%. Furthermore, when a head was significantly different to the average case, the proposed approach improved the inversion homogeneity by up to 24%, compared to the conventional one-size-fits-all approach. Subpopulation UPs present an opportunity to improve the B1+$$ {\mathrm{B}}_1^{+} $$ homogeneity and reduce anatomical SAR safety margins at 7T without additional acquisition time for calibration.
URI: https://ahro.austin.org.au/austinjspui/handle/1/34044
DOI: 10.1002/mrm.29884
ORCID: 0000-0002-7829-7372
0000-0002-6492-2990
0000-0001-6357-9329
0000-0002-4927-0023
0000-0003-3600-9958
0000-0002-5032-4674
Journal: Magnetic Resonance in Medicine
PubMed URL: 37849035
ISSN: 1522-2594
Type: Journal Article
Subjects: kT$$ {\mathrm{k}}_{\mathrm{T}} $$-points
MRI
RF pulse design
SAR
UHF
parallel transmission
universal pulse
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