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| Result: Searchterm 'Image'
found in 129 messages |
| Result Pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 [23] 24 25 26 |
More Results:  Database (454) News Service (255) Resources (73) |
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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
|
| 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
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| 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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(login or register first) | |
Michael Daniec
Fri. 1 Dec.06,
20:47
[Reply (1 of 2) to:
'pgh to dicom conversion?'
started by: 'corey walker'
on Thu. 26 Oct.06]
Category:
General
|
| pgh to dicom conversion? |
we should be able to help, need more information to assess (how would you provide the images, ie. what media, quantity of images etc.)
you can contact me also at:
Michael Daniec
National Data Conversion Institute
212 463-7511 x107 or mdaniec@ndci.com
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| | View the whole thread | | |
Renate Bloemer
Mon. 13 Nov.06,
19:29
[Reply (1 of 2) to:
'T1 FAT SAT PRE AND POS GADO'
started by: 'CLAUDIO RIBERTI'
on Tue. 24 Oct.06]
Category:
Contrast Agents
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| T1 FAT SAT PRE AND POS GADO |
The contrast agent causes this difference. Contrast agents reduce the T1 time in tissues where they have accumulated depending on blood flow and vascular permeability. Caused by this, tissues after an application of contrast agents will differ in shortening of the T1 time, and the same imaging parameters result in other image appearance.
Some helpful links for musculoskeletal imaging and Fat Sat:
http://www.moffitt.org/moffittapps/ccj/v8n3/pdf/221.pdf
http://www.medical.siemens.com/siemens/en_US/gg_mr_FBAs/files/MRI_Hot_Topics/MRI_HotTopics_Skinny_on_FatSat_engl.pdf
Hope this helps
Renate Bloemer
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