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| Result: Searchterm 'sequence'
found in 105 messages |
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More Results:  Database (378) News Service (28) Resources (10) |
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Steven Ford
Mon. 7 Mar.11,
16:07
[Reply (6 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 |
We maintain a lot of magnets. The leading cause of image quality problems is applications related. Nobody can possibly know all the nuances of pulse sequences by various vendors, software levels, etc. I've heard many times that a certain machine is no good, when in fact the sequences are inefficiently set up. Look there first.
Usually the techs welcome good training. If they don't want to be trained, then you have a problem, but it sounds like this issue is caused by other factors.
If there are differences in baseline quality between the machines, then compensate for that by other means. Signal starvation is easily remedied; keep the quality as consistent as you can and let time be the variable, if it comes down to that.
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Steven Ford
Thu. 3 Mar.11,
20:28
[Reply (1 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 |
I assume that you mean a t2 fat suppressed sequence. Differing gradient strengths have only an indirect effect on these images. The fat saturation sequences require additional pulses which take time to execute; stronger gradient systems can execute these pulses faster.
If you see different results, it can be caused by a number of factors; if you can describe the differences, that would be helpful. Generally speaking, the quality of the magnet homogeneity makes a big difference. If the small FOV scans (wrist) look different from magnet to magnet, that's probably not the cause.
You should ask your MRI applications specialist about this, and pay attention to the TE and bandwidth. Are the FOV and number of steps the same?
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Elise Gough
Wed. 23 Feb.11,
17:25
[Start of:
'6-1.5T MAGNETS, DIFFERING GRADIENTS'
7 Replies]
Category:
Applications and Examinations
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| 6-1.5T MAGNETS, DIFFERING GRADIENTS |
What parameter, if any, can compensate between magnets of equal field strength but very different gradient strengths? A T2 FAT sequence on one magnet can look very different on another magnet using same parameters.
Elise Gough RT(R)(CT)(MR)
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Mel Chang
Thu. 21 Oct.10,
19:26
[Reply (1 of 2) to:
'cervicla axial image t2 and t2*'
started by: 'kim jk'
on Thu. 23 Sep.10]
Category:
Applications and Examinations
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| cervicla axial image t2 and t2* |
T2* is fine to scan the intervertebral discs. T2 is the better choice to show small spinal cord lesions like MS plaques. The echo time of a T2* sequence may be not long enough to give a good differentiation between the pathology and surrounding tissue.rnDifferent 'Multi Echo Data Image Combination' (MEDIC) techniques have been developed to enhance contrast and pathology detection, if available on the scanner this type of sequence is maybe also a good choice, but due to longer scan times and artifact problems it is best for axial slices.rn
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Leak Sea
Sat. 16 Oct.10,
14:44
[Start of:
'How to fill the K-space?'
1 Reply]
Category:
Basics and Physics
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| How to fill the K-space? |
Hi,
i've been learning MRI for some weeks, and i really want to know that when we use the spin-echo sequences, how can we fill the data into K-space line by line?
i learned the steps of spatial encoding, but i need the algorithm, or the equations, or the quantitative way to fill the K-space.
thanks a lot!
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