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| | | MRI Forum
'Magnetic Field' | | |
| Result: Searchterm 'Magnetic Field'
found in 22 messages |
| Result Pages: 1 2 3 [4] 5 |
More Results:  Database (219) News Service (76) Resources (16) |
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Kathy Dumont
Sun. 6 Jan.08,
20:31
[Reply (2 of 6) to:
'Protection against magnetic exposure'
started by: 'Kathy Dumont'
on Sat. 5 Jan.08]
 Category:
Safety
|
| Protection against magnetic exposure |
Thank you very much Reader, for you answer very quickly! Sorry, I didn’t express myself very well. No, I don’t want to know about the “Gauss lines” (it’s how we say in France).
In the site of the World Health Organization, they talk about “The International EMF Project”.
I’m searching for informations about the effets of the magnetic fields on the human health. And the laws, if they exist in USA?
In France, there are no limits or laws which say the limits (time limits, job in high fields…) when you work at mri.
We just tell the pregnant not to go in the mri room. That’s all. I think you’re getting ahead France in this domain. For me, mri technology is like radiology’s first times, when Marie Curie discovered that tumor increased while X Ray exposure increased. You know?
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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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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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Dimitar Todorov
Thu. 9 Mar.06,
06:30
[Start of:
'does the metaloceramic dental crowns are problem for MRI'
1 Reply]
Category:
Safety
|
| does the metaloceramic dental crowns are problem for MRI |
Hi everybody,
I don't have an experiance with MRI, and i would like to know about metaloceramic crowns. It is true that they can be dangerous in MRI magnetic field. And if a patient have any metalic oject in the body (bulet or someting else) can it be livetreatening.
Thank you!
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Chris Gardener
Wed. 11 May.05,
22:43
[Reply (1 of 2) to:
'Radio frequency exposure'
started by: 'Reader Mail '
on Tue. 3 May.05]
Category:
Basics and Physics
|
| Radio frequency exposure |
If the magnetic field strength (measured in Tesla/Gauss) increases, also the SAR increases. For fields up to 3.0 Tesla, the value of SAR is proportional to the square of the field but at high fields the body becomes increasingly conductive, with the need of increased RF power. The EMF exposure is reduced by the square of the distance.
Hope this will help
Chris
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