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| Result: Searchterm 'Echo'
found in 42 messages |
| Result Pages: 1 2 [3] 4 5 6 7 8 9 |
More Results:  Database (305) News Service (7) Resources (10) |
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John Smith
Wed. 11 Nov.15,
22:14
[Start of:
'Faster pulse sequences'
0 Reply]
 Category:
General
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| Faster pulse sequences |
Hi,
I have been learning about faster MRI sequences and have two questions
1) With "Fast (Turbo) gradient echo", in which we apply a spoiler gradient, do we not eventually end up with no longitudinal magnetization because TR is always shorter than T1? Hence shouldn't we eventually get no signal at all?
2) in SSFP (Steady-state free precession) we can apply an RF pulse of 90 degrees (in which T1>>T2) to get heart-blood contrast. How is this any different to a standard spin-echo sequence in terms of timing?
Thank you
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aaron yonts`
Thu. 19 Sep.13,
07:56
[Reply (1 of 3) to:
'why there is T2* but not T1*'
started by: 'Isa Toni Toni'
on Wed. 24 Jul.13]
Category:
Sequences and Imaging Parameters
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| why there is T2* but not T1* |
i may just be giving general info but a t2* is aquired from a gradient echo compared to a t2 with a spin echo. according to mri in practice a t2* can help show some things a normal t2 would not, such as ms plaques in a cervical spine
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Reader Mail
Wed. 1 Jun.11,
14:14
[Start of:
'Dixon technique'
1 Reply]
Category:
Sequences and Imaging Parameters
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| Dixon technique |
I have been searching the web for information regarding a "double-echo two-excitation pulse sequence encoding fat and water signals for a phase-sensitive three-point Dixon type analysis". Does anyone know what pulse sequence(s) this is referring to, or a publication that might be helpful???
Thanks
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Elise Gough
Mon. 7 Mar.11,
16:54
[Reply (7 of 8) to:
'6-1.5T MAGNETS, DIFFERING GRADIENTS'
started by: 'Elise Gough'
on Wed. 23 Feb.11]
Category:
Applications and Examinations
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| 6-1.5T MAGNETS, DIFFERING GRADIENTS |
Thank you for your logical advice. Just spoke with GE apps. "No amount of messing with MR parameters can compensate for weak gradients. Increased gradient strength=decreased echo spacing=less blurring". Coincidently, my DO just emailed me asking what the gradient strength is on the magnet the RADs are complaining about.Just MAYBE they'll upgrade it. I need to visit our sites.The only way I have to check other sites' parameters is importing exams from PACS to my modality console. Tedious, but telling. Again, thankyou for all the help.
Elise Gough RT(R)(CT)(MR)
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Renate Semrau
Mon. 7 Mar.11,
15:11
[Reply (3 of 8) to:
'6-1.5T MAGNETS, DIFFERING GRADIENTS'
started by: 'Elise Gough'
on Wed. 23 Feb.11]
Category:
Applications and Examinations
|
| 6-1.5T MAGNETS, DIFFERING GRADIENTS |
Slew rate, rise time and/or duty cycle are specific parameters to describe the performance of the gradient amplifier. Amplifiers with higher performance allow a faster slew rate (shorter rise time). Stronger gradients allow to reduce echo time, increase the bandwidth and/or use a smaller FOV by influencing the SNR. To use same parameters on magnets with different gradient performance may not be recommended, or you have to adjust all parameters to the level of your magnet with the poorest performance.
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