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| Result: Searchterm 'Inversion'
found in 7 messages |
| Result Pages: [1] 2 |
More Results:  Database (61) News Service (1) Resources (2) |
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Bjorn Redfors
Sat. 27 Jun.09,
12:31
[Start of:
'90 excitation pulse vs 180 inversion pulse'
11 Replies]
 Category:
Basics and Physics
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| 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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Adana Osco Barras
Tue. 3 Jan.12,
21:09
[Reply (1 of 2) to:
'Hyperintense blood vessels in SE'
started by: 'Peruvumba Jayakumar'
on Thu. 29 Dec.11]
Category:
Sequences and Imaging Parameters
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| Hyperintense blood vessels in SE |
Prolonged T1 relaxation times, decreased T1 tissue contrast, and increased susceptibility rnare typical effects at high field MRI.rnDue to the longer T1 times at 3T, the signal rnintensity inside the vessels is preserved even in smaller vessels. Try TR 700, TE 10.rnInversion recovery sequences are very well suited for optimal gray to white matter contrast, but enhancement after administration of gadolinium may not be visible.
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Mike ferty
Sat. 10 Apr.10,
17:39
[Start of:
'MRI terminology need clarification'
0 Reply]
Category:
Basics and Physics
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| MRI terminology need clarification |
Hi,
This is a very wonderful site and I have learned alot from your definition database. I do have a question with some of the terminologies that I cannot find in your database, here are the ones:
What is:
Alpha pulse?
Inversion Pulse?
z-gradient pulse?
positive x-gradient pulse?
negative x-gradient pulse?
phase encoding pulse?
Refocusing gradient pulse?
Can you please help me know what there terms meant?
Many Thanks!
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N P
Fri. 18 Dec.09,
04:39
[Reply (5 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 |
Ok. How about reading the thread before posting. We're not asking how a 180 rephasing pulse works. INVERSION VS REPHASING CONCERNING COHERENCE.
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n p
Fri. 11 Sep.09,
11:50
[Reply (3 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 |
no hithesh n, that is a 180 rephasing pulse. thats not the question. the question is how is the net magnetization changed from the z plane to the -z plane without causing phase coherence, like the case of an inversion pulse. it is supposedly 2x as long or 2x as strong as the 90 degree pulse, but doesn't cause coherence. Why not is the question.
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