Simulation and design of shaped pulses beyond the piecewise-constant approximation

Uluk Rasulov; Anupama Acharya; Marina Carravetta; Guinevere Mathies; Ilya Kuprov

doi:10.1016/j.jmr.2023.107478

Simulation and design of shaped pulses beyond the piecewise-constant approximation

J Magn Reson. 2023 Aug:353:107478. doi: 10.1016/j.jmr.2023.107478. Epub 2023 May 15.

Authors

Uluk Rasulov¹, Anupama Acharya¹, Marina Carravetta¹, Guinevere Mathies², Ilya Kuprov³

Affiliations

¹ School of Chemistry, University of Southampton, United Kingdom.
² Department of Chemistry, University of Konstanz, Germany.
³ School of Chemistry, University of Southampton, United Kingdom. Electronic address: i.kuprov@soton.ac.uk.

PMID: 37343394
DOI: 10.1016/j.jmr.2023.107478

Abstract

Response functions of resonant circuits create ringing artefacts if their input changes rapidly. When physical limits of electromagnetic spectroscopies are explored, this creates two types of problems. Firstly, simulation: the system must be propagated accurately through every response transient, this may be computationally expensive. Secondly, optimal control: circuit response must be taken into account; it may be advantageous to design pulses that are resilient to such distortions. At the root of both problems is the popular piecewise-constant approximation for control sequences in the rotating frame; in magnetic resonance it has persisted since the earliest days and has become entrenched in the commercially available hardware. In this paper, we report an implementation and benchmarks of recent Lie-group methods that can efficiently simulate and optimise smooth control sequences.

Keywords: Lie group methods; Magnetic resonance; Optimal control; Spin dynamics; Spinach.