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| Result: Searchterm 'Spin'
found in 58 messages |
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More Results:  Database (332) News Service (64) Resources (27) |
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meike carr
Mon. 23 Oct.17,
15:48
[Start of:
'Dialysis pt and Artifacts'
0 Reply]
 Category:
General
|
| Dialysis pt and Artifacts |
We are having an artifact or loss of signal when we do some dialysis patients spine work. Both of our machines are GE 1.5 and a 3t. It does not happen on all dialysis patients only a few but the images will come out completely dark. We typically do not have any issues with our spine imaging. Has anyone else had this issue or heard of this? Any suggestions on how to fix, it is worse on the 3t of course.
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mm jj
Thu. 31 Aug.17,
04:30
[Start of:
'flipping'
0 Reply]
Category:
General
|
| flipping |
hi
cam we flip net magnetisition vector more than 180? if so,what happens?
after flipping 360 degree,is there any relaxation?
360 pulse makes spins back to initial state?
thanks in advance.
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Antonio Dominin
Mon. 14 Aug.17,
00:03
[Start of:
'MRI Safety w VNS Lead Still In Body'
0 Reply]
Category:
Safety
|
| MRI Safety w VNS Lead Still In Body |
Hello Everyone!rn:-)rnrnPlease forgive me in advance for making any newbie mistakes here. I am new and appreciate your kind correction of any errors that I might make.rnrnI am a patient with many, many illnesses. In 2006, I was in the deepest depths of depression and could not see any other way to treat it, other than the newly approved (then) Vagus Nerve Stimulator (VNS) for depression.rnrnNeedless to say, it did not help at all and, after over 2 years of VNS therapy, my doctor and I agreed to turn it off. (It makes the neck muscles move when it is stimulating the vagus nerve, which can get annoying after a while.)rnrnWhen I got the VNS implanted, I was told that I would never be able to have an MRI done, except with special equipment, called a transmit & receive coil. This wasn't a problem because my hospital, Olympia Medical Center, here in Los Angeles, had one of these.rnrnHowever when they upgraded their equipment in the years following my implant, they no longer had a transmit & receive coil for the new machine, and I could not find any place in LA that did have this coil.rnrnNow, since I have so many illnesses in my life, the possibility that I will need an MRI in the future is great. Therefore, I called and spoke with the assistant of the Neurosurgeon at USC Keck Medical Center that implants VNS, and he could therefore remove the VNS.rnrnHowever, the assistant said that, while he could remove the VNS device itself, he would probably have to leave the lead to the vagus nerve in the body because of it's attachment to the nerve has probably grown in at this point.rnrnMy question is this: Will I be able to safely have MRIs in the future with this lead still in my body? At this point, I am thinking that I might have to have MRIs of my brain (Parkinson’s disease, exotropia), wrist (Carpal Tunnel Syndrome), C-spine (prior to doing occipital nerve blocks). Do you have any other comments or suggestions on my situation?rnrnThank you very much for your kindest consideration of my post. I look forward to hearing back from you, and I will await your replies. rnrnBest regards,rnrn~Antonio Dominionrn:-)
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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
|
| 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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William Richardson
Tue. 20 Jun.17,
12:33
[Start of:
'MRI 1w/kg sequences Siemens Avanto FIT'
0 Reply]
Category:
Sequences and Imaging Parameters
|
| MRI 1w/kg sequences Siemens Avanto FIT |
I have recently been asked to build protocols for Spines and extremities that are 1 watt per kilogram SAR. In speaking with Applications at Siemens they inform me that I can only change certian parameters to help lower SAR but it will all be dependent upon each patient and which sequences are running. I need to present to our MRI QA commitiee if we can or if we cannot do 1w/kg SAR as we are determining if we can scan cochlear implants? Does anyone have any ideas or solutions?
Thank You
Will R.
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