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| Result: Searchterm 'MRI'
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Math G
Fri. 30 Jun.17,
21:02
[Reply (10 of 12) to:
'90 excitation pulse vs 180 inversion pulse'
started by: 'Bjorn Redfors'
on Sat. 27 Jun.09]
 Category:
Basics and Physics
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| 90 excitation pulse vs 180 inversion pulse |
I will try an answer to this rather old tread, in case someone stumble upon this like me.
The phenomenon of "coherence" that produce transverse magnetization after a 90 RF pulse cannot be answered by classical mechanics, or any simple model that represents individual protons as precessing magnets in either the parallel/antiparallel direction with regards to the MRI magnetic field.
Rather, it is a phenomenon related to quantum mechanics and the effect of a RF field on a interacting group of particles with spins (not necessarily oriented as parallel/antiparallel, I might add, even under the effect of a magnetic field).
The simplest depiction, as I understand, would be to imagine a group of spins as literally rotating as a whole under the effect of the RF. After a certain time (corresponding to a 90 degree pulse), the net magnetization that was oriented parallel to the MRI magnetic field, is now oriented in the transverse plane, causing transverse magnetization and signal. If you further apply RF, the system will continue to rotate, shifting gradually toward an antiparralel orientation, losing transverse magnetization in the process.
Hope its clearer!
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Arnold Somereville
Sun. 23 Apr.17,
18:06
[Start of:
'GE 8 channel Body Coil Artifact'
2 Replies]
Category:
Artifacts
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| GE 8 channel Body Coil Artifact |
Have a GE 1.5T HDxt. Problem: experiencing symmetric artifacts in abdominal images. Artifact seen in most anterior images: Some are rectangular in appearance, another reminds me of a plastic knife. All patients are changed in gowns/pants prior to entry into MRI suite. The body coil in question has been changed 3 times but the artifact remains. I suspect this is a hardware reconstruction issue, however, the engineer thinks it is operator error. I have run this sequence with and without options. This is an SSFSE, breath hold sequence. Has anyone encountered this issue?
 MRI Abdomen 8 channel body coil
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Michael Cunningham
Fri. 20 Jan.17,
21:18
[Start of:
'Why reset relative SNR value on GE Optima?'
0 Reply]
Category:
Sequences and Imaging Parameters
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| Why reset relative SNR value on GE Optima? |
Hello, if anyone works on a GE Optima, or any other MRI that has a relative SNR reset button during scan, please explain to me the purpose of this button. I see that it brings the relative SNR back up to 100 percent, but it can't actually be improving the image quality, can it? I just don't understand what the button is actually doing. The manual states that pressing the button brings the value to 100. Clearly. But what is actually happening other than making me feel better about my scan. Thanks.
mjcunningham RT (R) (MR)
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tracie smith
Thu. 8 Dec.16,
16:11
[Reply (20 of 21) to:
'MRI registry equations'
started by: 'Donna Nusser'
on Tue. 18 Aug.09]
Category:
Basics and Physics
|
| MRI registry equations |
Hi i saw your post to this forum and i am studying for the MRI registry as well. I have taken it twice and scored a 74 last time. This is my final attempt and i saw threads with people sharing info and study guides. I wasn't sure how to post to the main forum but if you could repost this to the main forum that would be appreciated so much. if anyone can email any information or study test etc. I am so nervous being my third attempt and ive been out of school so long lol My job is on the line if I dont pass. Ive been studying MRI in Practice hopefully that will help but I just wanted to leave my email address traciem218@gmail.com if anyone has any study hints ect. please send them Im in desperate need to pass this. I hope yours went well if you've taken it yet. Thanks in advance for any infornTraciern
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Mitchell Sapp
Fri. 15 Jul.16,
15:05
[Start of:
'Crash cart requirements for contrast'
0 Reply]
Category:
General
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| Crash cart requirements for contrast |
We are an outpatient surgical center with an MRI department and on-site physicians and we frequently have contrasted exams. What are the MRI department-specific requirements for the crash cart? We currently have a fully loaded crash cart that is honestly stocked with a lot of medications we would never administer even during a reaction. So in an effort to cut restocking costs, what are we REQUIRED to have on hand? And which organization would govern that? (The ACR white paper on MRI safety doesn't seem to cover this topic.)
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