Realignment capability of the nCPMG sequence

• Published in: Journal of magnetic resonance (1997) 2011-08, Vol.211 (2), p.121-133
• Main Authors: Le Roux, P., McKinnon, G., Yen, Y.-F., Fernandez, B.
• Format: Article
• Language: English
• Subjects: Algorithms; Amplitudes; Carr–Purcell–Meiboom–Gill (CPMG); Driven equilibrium Fourier transform (DEFT); Electromagnetic Fields; Electron Spin Resonance Spectroscopy - methods; Indicators and Reagents; Magnetization; MLEV; nCPMG; Nutation; Phase modulation; Realignment; Rendering; Shinnar–LeRoux; Signal Processing, Computer-Assisted; Stabilization; Trains
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2011.05.005

[Display omitted] ► The nCPMG sequence aims at phase insensitive generation of a long train of echoes. ► The magnetization it generates presents a symmetry property in the frequency domain. ► This is taken advantage of to determine an inverse sequence. ► A realignment of any type of magnetization at the last echo time is then possible. ► An experimental verification of this claim is presented here. The nCPMG sequence is based on a particular phase modulation of the refocusing pulse train, and was originally designed for rendering the spin echo amplitude insensitive to the initial magnetization phase. This pulse sequence has the peculiarity of being easily invertible, which enables perfect driven equilibrium experiments, in the absence of relaxation. This magnetization ‘realignment’ is effective for all three components. Hence the overall operation is transparent. Supporting theory is presented here, together with the first direct experimental proof of the claim. The experiment shows that, with the present stabilization sequence, perfect realignment is indeed made possible for a range of refocusing pulse nutation angles from 130° to 230°.