Minimum TR radiofrequency-pulse design for rapid gradient echo sequences.

Autor: Abo Seada S; School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom., Price AN; School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom., Hajnal JV; School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom., Malik SJ; School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom.
Jazyk: angličtina
Zdroj: Magnetic resonance in medicine [Magn Reson Med] 2021 Jul; Vol. 86 (1), pp. 182-196. Date of Electronic Publication: 2021 Feb 15.
DOI: 10.1002/mrm.28705
Abstrakt: Purpose: A framework to design radiofrequency (RF) pulses specifically to minimize the TR of gradient echo sequences is presented, subject to hardware and physiological constraints.
Methods: Single-band and multiband (MB) RF pulses can be reduced in duration using variable-rate selective excitation (VERSE) VERSE for a range of flip angles; however, minimum-duration pulses do not guarantee minimum TR because these can lead to a high specific absorption rate (SAR). The optimal RF pulse is found by meeting spatial encoding, peripheral nerve stimulation (PNS) and SAR constraints. A TR reduction for a range of designs is achieved and an application of this in an MB cardiac balanced steady-state free-precession (bSSFP) experiment is presented. Gradient imperfections and their imaging effects are also considered.
Results: Sequence TR with low-time bandwidth product (TBP) pulses, as used in bSSFP, was reduced up to 14%, and the TR when using high TBP pulses, as used in slab-selective imaging, was reduced by up to 72%. A breath-hold cardiac exam was reduced by 46% using both MB and the TR-optimal framework. The importance of RF-based correction of gradient imperfections is demonstrated. PNS was not a practical limitation.
Conclusion: The TR-optimal framework designs RF pulses for a range of pulse parameters, specifically to minimize sequence TR.
(© 2021 International Society for Magnetic Resonance in Medicine.)
Databáze: MEDLINE
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