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| Result: Searchterm 'Blurring'
found in 6 messages |
| Result Pages: [1] 2 |
More Results:  Database (15) |
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Elise Gough
Mon. 7 Mar.11,
16:54
[Reply (7 of 8) to:
'6-1.5T MAGNETS, DIFFERING GRADIENTS'
started by: 'Elise Gough'
on Wed. 23 Feb.11]
 Category:
Applications and Examinations
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| 6-1.5T MAGNETS, DIFFERING GRADIENTS |
Thank you for your logical advice. Just spoke with GE apps. "No amount of messing with MR parameters can compensate for weak gradients. Increased gradient strength=decreased echo spacing=less blurring". Coincidently, my DO just emailed me asking what the gradient strength is on the magnet the RADs are complaining about.Just MAYBE they'll upgrade it. I need to visit our sites.The only way I have to check other sites' parameters is importing exams from PACS to my modality console. Tedious, but telling. Again, thankyou for all the help.
Elise Gough RT(R)(CT)(MR)
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|  View the whole thread | | |
Jacob Newton
Thu. 7 Oct.10,
19:22
[Reply (1 of 2) to:
'How does TE affect DWI acquisition?'
started by: 'danilo Scelfo'
on Wed. 29 Sep.10]
Category:
Sequences and Imaging Parameters
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| How does TE affect DWI acquisition? |
I never tried to shorten only the echo time while keeping all other parameters the same, but I would expect a change in SNR and artifact appearance. I would use parallel imaging methods to get a shortest possible echo time. Parallel imaging provides DWI with shorter echo trains associated with further reduction of the echo and repetition times, which reduces susceptibility effects and also image blurring. Additionally, the shorter echo time may lead to changes in ADC measurement.
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| | View the whole thread | | | |
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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 | | |
Scott Lytle
Thu. 4 Jan.07,
17:52
[Reply (2 of 3) to:
'ETL for a STIR'
started by: 'Shaun Schofield'
on Thu. 30 Mar.06]
Category:
Sequences and Imaging Parameters
|
| ETL for a STIR |
It depends.
When Centric echo allocation is used you have higher SNR, a low TE, but more image blurring. Very similar to a PD. I prefer an echo train of less than 8 in this case.
When Sequential echo allocation is used you have lower SNR, a higher TE (I prefer less than a TE of 60), but significantly less image blurring. Very similar to a T2 or FLAIR. In this case your echo train length is governed by your TE and image blurring is not usually an issue. Depending on how short of an inter-echo time you can use, and by keeping an eye on the TE, the echo train can be as high as you want.
Hope this helps.
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| | View the whole thread | | |
ergun ahunbay
Tue. 2 Jan.07,
19:20
[Start of:
'Geometric distortion'
2 Replies]
Category:
Artifacts
|
| 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?
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?
thank you very much in advance
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