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| Result: Searchterm 'Spin Echo'
found in 12 messages |
| Result Pages: 1 [2] 3 |
More Results:  Database (96) News Service (1) |
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David Brooks
Tue. 22 Dec.09,
02:35
[Start of:
'Scan equation I don't get, HELP'
2 Replies]
 Category:
Basics and Physics
|
| Scan equation I don't get, HELP |
Here's the question:
The approximate scan time of a rapid spin echo sequence with a TR of 3500ms, a TE of 90ms, a 256x256 matrix, 1 exicitation, a 220mm FOV and an echo train length of 5 is______ minutes.
Formal they give is 3500msx1x256/5=?
a.3
b. 8
c. 11
d. 15
I get 179200. What am I missing in my studies and the math?
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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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Jenny Jordan
Sat. 17 Nov.07,
20:11
[Reply (2 of 4) to:
'Haste and Rare sequences'
started by: 'Elena sussi'
on Tue. 13 Nov.07]
Category:
Sequences and Imaging Parameters
|
| Haste and Rare sequences |
Hi Elena,
you can find the different names for the same sequences and options used by manufacturers at: http://www.mr-tip.com/serv1.php?type=cam .
The manufacturers have in principle similar sequences with small differences. So, as you mentioned you can take "sequences as HASTE" or "sequences type RARE".
However, you can lead back these sequences also to the fundamental sequence type FSE ( fast spin echo: http://www.mr-tip.com/serv1.php?type=seq&sub=12 ). Fast sequences as HASTE ( http://www.mr-tip.com/serv1.php?type=db1&dbs=haste ) are especially useful in cases of movement caused by their single shot technique: http://www.mr-tip.com/serv1.php?type=db1&dbs=Single%20Shot%20Technique .
Hope this helps
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Reader Mail
Tue. 6 Mar.07,
22:48
[Start of:
'fluid PD vs T2 weighting'
1 Reply]
Category:
Sequences and Imaging Parameters
|
| fluid PD vs T2 weighting |
Can anyone explain me, why - considering SE sequences with the same TR - fluid in a PD weighting (short TE) should have less signal than in a T2 weighting (long TE)? eg:
Fig 10, p 1397; radiographics resident tutorial: contrast mechanisms in spin echo MR imaging; Radiographics 1994; 14; pp 1389-1404
I would expect that the signal intensity of any tissue (regardless of it Proton density of T2-relaxation time) should decrease with increasing echo time.
Thank you
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Jennifer Jackson
Fri. 21 Jul.06,
04:44
[Reply (1 of 2) to:
'Phase encoding'
started by: 'guillaume bierry'
on Fri. 7 Jul.06]
Category:
General
|
| Phase encoding |
Wow this is a long subject, First you have to under stand how the 3 main gradients are used. (slice select, Freq, then phase)
So you are use 1 of the gradients for your phase encoding. You need to fill the k-space which depends on you matrix. Lets assume you are using 256 (phase). In order to fill K-space you have to have 256 aquistions of the signal. Meaning for each picture (or slice) the signal must be acquire(sampled) 256 times each at a differnt amplitude to put it in a different Line of k-space.
Example- If you are performing a SE(spin echo) you have 1 TR period and 1 TE period (TE=is when the signal is sampled) so you will have to do the TR period 256 times to fill K-space with diffent amplitudes.
There is alot more that I left out. If this did not answer your question let me know
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