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'Gradient Echo Sequence' | | |
| Result: Searchterm 'Gradient Echo Sequence'
found in 3 messages |
| Result Pages: [1] |
More Results:  Database (70) News Service (1) Resources (1) |
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Renate Bloemer
Mon. 13 Nov.06,
19:46
[Reply (1 of 3) to:
'MRA'
started by: 'Marco Costa'
on Sun. 22 Oct.06]
 Category:
Protocols
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| MRA |
A test bolus helps to get the delay at which time the CE-MRA sequence has to be started. The sequence needed is a one-slice dynamic fast gradient echo sequence (if possible with fat suppression or subtraction) and a temporal resolution of 0.5 to 1.5 sec. This thick slice is placed over the vessel of interest and the dynamic is started simultaneous with a small (1-2ml) bolus of Gad.
In the follow up you can see at which time the bolus is visible. If it is not clear to differentiate, a ROI measurement will help. The starting time depends on the k-space filling. Around the peak of the highest intensity, the contrast information should be read out (with "centric" at the beginning of the sequence).
Centric k-space filling order means that the central lines of the k-space are filled in the first seconds after starting the scan. Depending on the equipment, there is more than one non-centric order, for example linear, where the central lines are filled in the middle of the scan time.
Hope this helps.
Renate Bloemer
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Nancy Dudek
Fri. 26 Aug.05,
00:25
[Start of:
'3T imaging parameters'
2 Replies]
Category:
Sequences and Imaging Parameters
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| 3T imaging parameters |
Hi
Am looking for the ranges of acceptable TR and TE's for standard spin echo and gradient echo sequences on a 3T.
Does anyone know these or tell me where I can find this info?
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Schmidt Marga
Sat. 17 Apr.04,
20:41
[Reply (1 of 2) to:
'Moire fringing'
started by: 'Kelly Wimpey'
on Tue. 6 Apr.04]
Category:
Artifacts
|
| Moire fringing |
Moire fringes are typical for gradient echo sequences, especially balanced sequences like for example true fisp, bFFE. The reasons are interferences and field inhomogeneities. High order shimming (volume shimming), a more suitable coil, a smaller bandwidth, and scanning not in the edges of the magnetic field will avoid or reduce this artifact. Also parallel imaging techniques can have a positive influence. If this artifact appears, also by using other sequences, a new field adjustment can be necessary (service).
Hope this will help.
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