Abstract
Purpose We propose a new slab-wise framework to design parallel transmit multiband pulses for volumetric simultaneous multislice imaging with a large field of view along the slice direction (FOVs). Theory and Methods The slab-wise framework divides FOVs into a few contiguous slabs and optimizes pulses for each slab. Effects of relevant design parameters including slab number and transmit B1 (B1+) mapping slice placement were investigated for human brain imaging by designing pulses with global or local SAR control based on electromagnetic simulations of a 7T head RF array. Pulse design using in vivo B1+ maps was demonstrated and evaluated with Bloch simulations. Results RF performance with respect to SAR reduction or B1+ homogenization across the entire human brain improved with increasing slabs; however, this improvement was nonlinear and leveled off at ∼12 slabs when the slab thickness reduced to ∼12 mm. The impact of using different slice placements for B1+ mapping was small. Conclusion Compared with slice-wise approaches where each of the many imaging slices requires both B1+ mapping and pulse optimization, the proposed slab-wise design framework attained comparable RF performance while drastically reducing the number of required pulses; therefore, it can be used to increase time efficiency for B1+ mapping, pulse calculation, and sequence preparation.
Original language | English (US) |
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Pages (from-to) | 1444-1456 |
Number of pages | 13 |
Journal | Magnetic resonance in medicine |
Volume | 75 |
Issue number | 4 |
DOIs | |
State | Published - Apr 1 2016 |
Bibliographical note
Publisher Copyright:© 2015 Wiley Periodicals, Inc.
Keywords
- high-field MRI
- multiband RF pulse design
- parallel excitation
- simultaneous multislice imaging
- transmit B1 homogenization
Center for Magnetic Resonance Research (CMRR) tags
- MRE