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| Result: Searchterm 'Bandwidth'
found in 14 messages |
| Result Pages: 1 2 [3] |
More Results:  Database (19) |
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peter hobden
Wed. 14 Feb.07,
15:35
[Reply (1 of 3) to:
'Geometric distortion'
started by: 'ergun ahunbay'
on Tue. 2 Jan.07]
 Category:
Artifacts
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| Geometric distortion |
Dear Listers,
I have some questions about the image distortions in MRI:
1) Are the magnetic field inhomogeneities the only cause of image distortions? Does RF-inhomogeneities cause distortions or just signal inaccuracies?
There are other factors that can affect the /amount/ of distortion. Run an EPI sequence and change the bandwidth and see the image change shape.
There are other causes of image distortion which are not necessarily directly related to field homogeneity.
It is a complicated question you are asking here!
2) Is it accurate to say that a spiral sequence would not have distortion due to magnetic field inhomogeneity(, but it would have blurring). Would there be image geometric distortions with a spiral imaging?
I guess you are talking about spiral filling of k-space?? The sampling time reduction will help to reduce distortion to some extent.
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|  View the whole thread | | |
Renate Bloemer
Mon. 13 Nov.06,
19:35
[Reply (1 of 3) to:
'Receiver Bandwidth'
started by: 'Stephanie Taylor'
on Wed. 1 Nov.06]
Category:
Basics and Physics
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| Receiver Bandwidth |
Maybe these links will help: http://www.revisemri.com/tutorials/receiver_bandwidth/rbandwidth_files/fullscreen.htm
http://www.medical.siemens.com/siemens/en_US/rg_marcom_FBAs/files/DICpage/MRIHottopics2.pdf
http://www.ebyte.it/library/educards/mri/K-SpaceMRI.html
http://www.mr-tip.com/serv1.php?type=db1&dbs=Bandwidth
Renate Bloemer
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| | View the whole thread | | |
Reader Mail
Sun. 21 May.06,
13:53
[Reply (1 of 3) to:
'What Philips calls bandwidth'
started by: 'Anne Nelson'
on Thu. 4 May.06]
Category:
General
|
| What Philips calls bandwidth |
The corresponding term is the water fat shift and can be changed in the contrast parameter table.
Lower bandwidth = higher water fat shift
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| | View the whole thread | | |
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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