Publication

Modulations of Spin Echoes in Liquids

Geoffrey Bodenhausen
2013
Journal Articles

Résumé

Echo modulations that arise in Carr–Purcell–Meiboom–Gill (CPMG) spin echo sequences and stem from homonuclear couplings can be suppressed by different methods. The evolution under homonuclear couplings can be either ‘‘locked’’ or ‘‘refocused’’, leading to different transverse decay rates.

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https://infoscience.epfl.ch/entities/publication/c6dd055e-7829-4968-81c3-5279c0e38eff

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Geoffrey Bodenhausen
2013
Journal Articles

Résumé

Source officielle

https://infoscience.epfl.ch/entities/publication/c6dd055e-7829-4968-81c3-5279c0e38eff

À propos de ce résultat

Concepts associés (13)

Spin echo

In magnetic resonance, a spin echo or Hahn echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) make use of this effect. The NMR signal observed following an initial excitation pulse decays with time due to both spin relaxation and any inhomogeneous effects which cause spins in the sample to precess at different rates. The first of these, relaxation, leads to an irreversible loss of magnetisation.

Spin–spin relaxation

In physics, the spin–spin relaxation is the mechanism by which Mxy, the transverse component of the magnetization vector, exponentially decays towards its equilibrium value in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). It is characterized by the spin–spin relaxation time, known as T2, a time constant characterizing the signal decay. It is named in contrast to T1, the spin–lattice relaxation time.

Modulation de fréquence

right|Illustration de modulation en amplitude et en fréquence. La modulation de fréquence ou MF (FM en anglais) est un mode de modulation consistant à transmettre un signal par la modulation de la fréquence d'un signal porteur (porteuse). On parle de modulation de fréquence par opposition à la modulation d'amplitude. En modulation de fréquence, l'information est portée par une modification de la fréquence de la porteuse, et non par une variation d'amplitude.

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