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| Result: Searchterm 'Mode'
found in 18 messages |
| Result Pages: 1 2 [3] 4 |
More Results:  Database (85) News Service (93) Resources (25) |
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David Pierce
Fri. 14 Oct.11,
15:43
[Reply (4 of 7) to:
'MRI Magnet Room Cameras?'
started by: 'David Pierce'
on Thu. 22 Sep.11]
 Category:
Equipment
|
| MRI Magnet Room Cameras? |
Wow, thanks you guys!
Can you tell me who you went through to get these cameras?
How difficult are they to use? And to install?
Jack, Where did you get that stereo-camera model? That sounds great!
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|  View the whole thread | | |
Oliver Lyttelton
Mon. 1 Mar.10,
13:39
[Reply (8 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 |
Okay, so this thread is answering close to a question I had, which is how to conceptually understand what happens with alpha>90 degrees excitation pulses.
I can imagine spinning tops, precessing at the Larmor frequency, I can imagine that as you apply the excitation pulse which is always in the transverse plane to the main magnet, you start to pull the tops further away from the B0 axis and bring them into coherence so like lots of little lighthouses they are all bright/dark in phase with each other. I can imagine a 90 degree pulse bring the spins completely into the transverse plane. I can imagine them relaxing, dephasing quickly and then slowly reducing their angle of precession back up towards initial state close to direction B0.
But what I can't understand in my (rather newtonian) model, is what happens as you continue to excite beyond the 90 degree transverse plane. I sort of get that somehow the spins continue to rotate in some (weird) dimension, and that they have to come back through that (weird) dimension first before returning from 90 degrees back to the relaxed state. But what happens in "weird" dimension is beyond my conceptual model. Can someone extend my model for me, preferrably without signal equations?
tar muchly,
Oliver
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| | View the whole thread | | |
Bjorn Redfors
Sat. 27 Jun.09,
12:31
[Start of:
'90 excitation pulse vs 180 inversion pulse'
11 Replies]
Category:
Basics and Physics
|
| 90 excitation pulse vs 180 inversion pulse |
Im a medical student interested in diagnostic medicine and aim to understand (on some level) the basics of MRI theory but lack an advanced physics background.
Why are the "spins" "brought into coherence" by the 90 excitation pulse but not by a 180 inversion RF pulse?
And how is the 180 inversion pulse explained on the nuclear level, i.e. "paralell/antiparalell" orientation of single nuclei (is it possible by such a simple model?)?
Is it possible to explain this "in layman's terms"?. I find that most texts (at least those written for physicians) omit proper explanations of this.
Thank You!
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Simion Marga
Tue. 2 Jun.09,
11:58
[Start of:
'Bay MRI scanner'
0 Reply]
Category:
Devices, Scanner, Machines
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| Bay MRI scanner |
We want to bay the MRI scanner. Can somebody help us to choose the optimal low field model with permanent magnet?
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| | Reply to this thread
(login or register first) | |
Ihor Tur
Sat. 2 May.09,
16:39
[Reply (6 of 7) to:
'Which MRI machine to buy?'
started by: 'Mike Benji'
on Fri. 12 Dec.08]
Category:
Devices, Scanner, Machines
|
| Which MRI machine to buy? |
Hi,
I am planning my own MRI business, but I do not know the machine of what company and model is good enough to buy, regarding to reliability, producibility ext., can somebody give me advice how to start, please?
Ihor
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