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| Result: Searchterm 'Phase'
found in 33 messages |
| Result Pages: 1 2 3 [4] 5 6 7 |
More Results:  Database (285) News Service (25) Resources (11) |
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asdf asdfad
Mon. 25 Apr.11,
15:50
[Reply (3 of 4) to:
'Math equation'
started by: 'crystal f'
on Sun. 18 Oct.09]
 Category:
Basics and Physics
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| Math equation |
Time = (TR x NEX x Phase)/ETL
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|  View the whole thread | | |
Michiel Klitsie
Wed. 2 Jun.10,
14:53
[Start of:
'Imaging of the sacral plexus'
1 Reply]
Category:
Applications and Examinations
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| Imaging of the sacral plexus |
We are students Technical Medicine from Twente University and are researching the imaging of the anatomical variation of the sacral plexus. This means the imaging of nerves in a fatty/muscle enviroment with a diameter below 1 mm.rnrnWe are interested in different MR-sequences that will show these small nerves (at the moment we came up with MP(2)Rage, STIR, normal SE T1 and DW) Does anybody can provide us why we should or shouldn't use one of these sequences. Or maybe somebody does have a better suggestion?rnrnAlso we were planning to combine spinal and abdominal coils (phased-array RF coils), does this depict the sacral plexus in a good way?rnrnWe also thought about using a 7T MRI scanner, because of the high spatial resolution. Is this a possibility or does it give to much artifacts? Or is the spatial resolution in a 3T machine enough for such small nerves?rnrnThanks in advance!
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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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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
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| 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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George LoGuirato
Thu. 29 Oct.09,
19:40
[Reply (1 of 4) to:
'Math equation'
started by: 'crystal f'
on Sun. 18 Oct.09]
Category:
Basics and Physics
|
| Math equation |
Time in msec = TR * #phase_steps * NEX
Time in sec = (TR * #phase_steps * NEX) / 1000
Time in minutes = (-as above-) / 60,000
note: for FAST or TURBO spin echo divide the
#phase_steps by the ETL
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