Minimum-TR RF pulse design for rapid gradient echo sequences

Samy Abo Seada, Anthony N. Price, Joseph V. Hajnal, Shaihan J. Malik*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
93 Downloads (Pure)

Abstract

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.

Original languageEnglish
Pages (from-to)182-196
Number of pages15
JournalMagnetic Resonance in Medicine
Volume86
Issue number1
Early online date15 Feb 2021
DOIs
Publication statusPublished - Jul 2021

Keywords

  • cardiac
  • radiofrequency pulse design
  • rapid imaging
  • simultaneous multislice (SMS)

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