A generalized slab‐wise framework for parallel transmit multiband RF pulse design. Issue 4 (20th May 2015)

• Record Type: Journal Article
• Authors: Wu, Xiaoping; Schmitter, Sebastian; Auerbach, Edward J.; Uğurbil, Kâmil; Van de Moortele, Pierre‐François
• Is Part Of: Magnetic resonance in medicine. Volume 75:Issue 4(2016)
• Page Start: 1444
• Page End: 1456
• Publication Date: 2015-05-20
• Subjects: parallel excitation -- simultaneous multislice imaging -- transmit B1 homogenization -- high‐field MRI -- multiband RF pulse design; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.25689
• Languages: English
• ISSNs: 0740-3194

Abstract

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.Magn Reson Med 75:1444–1456, 2016. © 2015 Wiley Periodicals, Inc.