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Modeling the influence of TR and excitation flip angle on the magnetization transfer ratio (MTR) in human brain obtained from 3D spoiled gradient echo MRI

Helms, Gunther LU ; Dathe, Henning and Dechent, Peter (2010) In Magnetic Resonance in Medicine 64(1). p.177-185
Abstract
Attempts to optimize the magnetization transfer ratio (MTR) obtained from spoiled gradient echo MRI have focused on the properties of the magnetization transfer pulse. In particular, continuous-wave models do not explicitly account for the effects of excitation and relaxation on the MTR. In this work, these were modeled by an approximation of free relaxation between the radiofrequency pulses and of an instantaneous saturation event describing the magnetization transfer pulse.

An algebraic approximation of the signal equation can be obtained for short pulse repetition time and small flip angles. This greatly facilitated the mathematical treatment and understanding of the MTR. The influence of inhomogeneous radiofrequency fields... (More)
Attempts to optimize the magnetization transfer ratio (MTR) obtained from spoiled gradient echo MRI have focused on the properties of the magnetization transfer pulse. In particular, continuous-wave models do not explicitly account for the effects of excitation and relaxation on the MTR. In this work, these were modeled by an approximation of free relaxation between the radiofrequency pulses and of an instantaneous saturation event describing the magnetization transfer pulse.

An algebraic approximation of the signal equation can be obtained for short pulse repetition time and small flip angles. This greatly facilitated the mathematical treatment and understanding of the MTR. The influence of inhomogeneous radiofrequency fields could be readily incorporated. The model was verified on the human brain in vivo at 3 T by variation of flip angle and pulse repetition time. The corresponding range in MTR was similar to that observed by a 4-fold increase of magnetization transfer pulse power. Choice of short pulse

repetition time and larger flip angles improved the MTR contrast and reduced the influence of radiofrequency inhomogeneity. Optimal contrast is obtained around an MTR of 50%, and noise progression is reduced when a high reference signal is obtained. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Magnetic Resonance in Medicine
volume
64
issue
1
pages
177 - 185
publisher
Wiley Online Library
external identifiers
  • scopus:77953942924
ISSN
1522-2594
DOI
10.1002/mrm.22379
language
English
LU publication?
yes
id
54c386f8-b08b-403a-a887-84c4031e53dd (old id 8773578)
date added to LUP
2016-02-27 00:59:33
date last changed
2018-05-29 09:36:14
@article{54c386f8-b08b-403a-a887-84c4031e53dd,
  abstract     = {Attempts to optimize the magnetization transfer ratio (MTR) obtained from spoiled gradient echo MRI have focused on the properties of the magnetization transfer pulse. In particular, continuous-wave models do not explicitly account for the effects of excitation and relaxation on the MTR. In this work, these were modeled by an approximation of free relaxation between the radiofrequency pulses and of an instantaneous saturation event describing the magnetization transfer pulse.<br/><br>
An algebraic approximation of the signal equation can be obtained for short pulse repetition time and small flip angles. This greatly facilitated the mathematical treatment and understanding of the MTR. The influence of inhomogeneous radiofrequency fields could be readily incorporated. The model was verified on the human brain in vivo at 3 T by variation of flip angle and pulse repetition time. The corresponding range in MTR was similar to that observed by a 4-fold increase of magnetization transfer pulse power. Choice of short pulse<br/><br>
repetition time and larger flip angles improved the MTR contrast and reduced the influence of radiofrequency inhomogeneity. Optimal contrast is obtained around an MTR of 50%, and noise progression is reduced when a high reference signal is obtained.},
  author       = {Helms, Gunther and Dathe, Henning and Dechent, Peter},
  issn         = {1522-2594},
  language     = {eng},
  number       = {1},
  pages        = {177--185},
  publisher    = {Wiley Online Library},
  series       = {Magnetic Resonance in Medicine},
  title        = {Modeling the influence of TR and excitation flip angle on the magnetization transfer ratio (MTR) in human brain obtained from 3D spoiled gradient echo MRI},
  url          = {http://dx.doi.org/10.1002/mrm.22379},
  volume       = {64},
  year         = {2010},
}