Improved design of frequency-swept pulse sequences

Jean-Baptiste Verstraete; Mohammadali Foroozandeh

doi:10.1016/j.jmr.2022.107146

Improved design of frequency-swept pulse sequences

J Magn Reson. 2022 Mar:336:107146. doi: 10.1016/j.jmr.2022.107146. Epub 2022 Jan 31.

Authors

Jean-Baptiste Verstraete¹, Mohammadali Foroozandeh²

Affiliations

¹ Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, UK.
² Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, UK. Electronic address: mohammadali.foroozandeh@chem.ox.ac.uk.

PMID: 35144158
DOI: 10.1016/j.jmr.2022.107146

Abstract

Frequency-swept pulses are extensively used in magnetic resonance spectroscopic techniques for the robust manipulation of spins across wide ranges of offset frequencies in the presence of B₁ field variations. Nevertheless, designing pulse sequences consisting of multiple frequency-swept pulses can be challenging, as they often require specific timings and parameter tweaking. In the present work we discuss a simple and general approach for constructing such sequences. We present new and improved pulse sequences for applications including broadband B₁-tolerant CPMG (CHORUS-CPMG), broadband chirped excitation with suppression of homonuclear J-modulation (PROCHORUS), and the further compression of frequency-swept pulse sequences by superposition of pulses which reduces pulse sequence durations by 25-40%. All sequence design strategies are accompanied by mathematical presentations, experimental results, and supporting simulations.

Keywords: -tolerant pulses; Broadband pulses; CHORUS; CPMG; Chirped pulses; Frequency-swept pulses; HS pulses; J-modulation; PROCHORUS; Perfect echo; Pulse superposition.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Algorithms*
Magnetic Resonance Imaging* / methods
Magnetic Resonance Spectroscopy / methods