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Radiofrequenz-Pulse in der lokalisierten STEAM-Spektroskopie

Helms, Gunther LU orcid (1994)
Abstract
By definition, radiofrequency (RF) pulses are the pivotal elements of NMR pulse sequences. Vice versa, the effect of a particular pulse on the evolution of magnetization will depend on the context of the sequence. While the product operator formalism provides a general framework to describe the effect of hard pulses on weakly coupled spin systems, there is no consistent framework describing the effect of selective pulses in the context of MRI sequence.
The excitation profile is the result of frequency dependent trajectories describing the complex interaction of nutation and precession. In spin-echo sequences, the refocusing pulse acts on a spatial distribution of transverse magnetization that may by spatially dispersed by the magnetic... (More)
By definition, radiofrequency (RF) pulses are the pivotal elements of NMR pulse sequences. Vice versa, the effect of a particular pulse on the evolution of magnetization will depend on the context of the sequence. While the product operator formalism provides a general framework to describe the effect of hard pulses on weakly coupled spin systems, there is no consistent framework describing the effect of selective pulses in the context of MRI sequence.
The excitation profile is the result of frequency dependent trajectories describing the complex interaction of nutation and precession. In spin-echo sequences, the refocusing pulse acts on a spatial distribution of transverse magnetization that may by spatially dispersed by the magnetic field gradient applied during the RF pulse. This situation is further complicated in the STEAM sequence, as the stimulated echo is created from a spatial distribution of transverse and longitudinal components.
Aim of the thesis was a qualified choice of selective RF pulses for an improved voxel definition of the STEAM localization and a critical appraisal of optimised RF pulse shapes. The problem was addressed by theory, by numerical simulations and with experimental methods. (Less)
Please use this url to cite or link to this publication:
author
supervisor
organization
alternative title
Selective Radiofrequency Pulses in Localization Sequences for in vivo NMR Spectroscopy
publishing date
type
Thesis
publication status
published
pages
150 pages
publisher
Cuvillier Verlag
ISBN
9783895880292
language
German
LU publication?
yes
id
62be7f83-367f-4c57-ae6c-3c29c9806492
date added to LUP
2020-07-15 19:23:57
date last changed
2021-02-08 15:15:30
@phdthesis{62be7f83-367f-4c57-ae6c-3c29c9806492,
  abstract     = {{By definition, radiofrequency (RF) pulses are the pivotal elements of NMR pulse sequences. Vice versa, the effect of a particular pulse on the evolution of magnetization will depend on the context of the sequence. While the product operator formalism provides a general framework to describe the effect of hard pulses on weakly coupled spin systems, there is no consistent framework describing the effect of selective pulses in the context of MRI sequence. <br/>The excitation profile is the result of frequency dependent trajectories describing the complex interaction of nutation and precession. In spin-echo sequences, the refocusing pulse acts on a spatial distribution of transverse magnetization that may by spatially dispersed by the magnetic field gradient applied during the RF pulse. This situation is further complicated in the STEAM sequence, as the stimulated echo is created from a spatial distribution of transverse and longitudinal components. <br/>Aim of the thesis was a qualified choice of selective RF pulses for an improved voxel definition of the STEAM localization and a critical appraisal of optimised RF pulse shapes. The problem was addressed by theory, by numerical simulations and with experimental methods.}},
  author       = {{Helms, Gunther}},
  isbn         = {{9783895880292}},
  language     = {{ger}},
  publisher    = {{Cuvillier Verlag}},
  school       = {{Lund University}},
  title        = {{Radiofrequenz-Pulse in der lokalisierten STEAM-Spektroskopie}},
  year         = {{1994}},
}