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  Sensitivity to local dipole fields in the CRAZED Experiment: An approach to bright spot MRI

Faber, C., Heil, C., Zahneisen, B., Balla, D., & Bowtell, R. (2006). Sensitivity to local dipole fields in the CRAZED Experiment: An approach to bright spot MRI. Journal of Magnetic Resonance, 182, 315-324. doi:10.1016/j.jmr.2006.05.002.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-CFC9-D Version Permalink: http://hdl.handle.net/21.11116/0000-0004-6FBD-C
Genre: Journal Article

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Faber, C, Author
Heil, C, Author
Zahneisen, B, Author
Balla, DZ1, Author              
Bowtell, R, Author
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1External Organizations, ou_persistent22              

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 Abstract: Local dipole fields such as those created by small iron-oxide particles are used to produce regions of low intensity (dark contrast) in many molecular magnetic resonance imaging applications. We have investigated, with computer simulations and experiments at 17.6 T, how the COSY revamped with asymmetric z-gradient echo detection (CRAZED) experiment that selects intermolecular double-quantum coherences can also be used to visualize such local dipole fields. Application of the coherence-selection gradient pulses parallel to the main magnetic field produced similar, dark contrast as conventional gradient echo imaging. Application of the gradient along the magic angle leads to total loss of signal intensity in homogeneous samples. In the presence of local dipole fields, the contrast was inverted and bright signals from the dipoles were observed over a very low background. Both simulations and experiments showed that the signal strongly decreased when a phase-cycle suppressing single-quantum coherences was employed. Therefore, we conclude that most of the signal comes from directly refocused magnetization or intermolecular single-quantum coherences. Finally, we demonstrate that bright contrast from local dipole fields can also be obtained, when the pair of coherence-selection gradient pulses is deliberately mismatched. Both methods allowed visualization of local dipole fields in phantoms in experimental times of about 3 min.

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 Dates: 2006-10
 Publication Status: Published in print
 Pages: -
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 Table of Contents: -
 Rev. Method: -
 Identifiers: BibTex Citekey: 7021
DOI: 10.1016/j.jmr.2006.05.002
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Title: Journal of Magnetic Resonance
Source Genre: Journal
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Publ. Info: San Diego [etc.] : Academic Press
Pages: - Volume / Issue: 182 Sequence Number: - Start / End Page: 315 - 324 Identifier: ISSN: 0022-2364
CoNE: https://pure.mpg.de/cone/journals/resource/954922651175_1