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| Result: Searchterm 'Image'
found in 128 messages |
| Result Pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 [15] 16 17 18 19 20 21 22 23 24 25 26 |
More Results:  Database (454) News Service (255) Resources (73) |
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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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|  View the whole thread | | |
Don LaVille
Tue. 21 Dec.10,
20:57
[Reply (1 of 3) to:
'Muscle shading in 3T Images'
started by: 'Travis Conley'
on Thu. 21 Oct.10]
Category:
Applications and Examinations
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| Muscle shading in 3T Images |
This artifact is known as the dielectric effect. It is a phenomena to all magnets. At 1.5T the dielectric effect is at 60cm so when we scan at a FOV of 40 or less we don't see it. At 3t the dielectric effect is reduced to 30cm so we now see it when using a FOV of 30 or more. There is no way to get rid of it that I know of and you will see an increase with patients with more magnetic suseptibility (ie. patients with ascities, and pregnant patient). You could try using Surface Coil Intensity Correction (SCIC) and it will help to even out the extreme dark and light in your image. Some vendors will suggest using a Fat Sat pad to help reduce this artifact. I have tried it with little success.
Looking at your image, it looks like you were scanning on a GE 3T HDX. I hope that the vendors will have a fix for this artifact soon. For right now though we are just dealing with it. I hope this helps.
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| | View the whole thread | | |
Steven Ford
Thu. 2 Dec.10,
15:18
[Reply (1 of 2) to:
'T1&T2 WAIGHTED MEANING ?'
started by: 'BINU VAEGHESE'
on Wed. 1 Dec.10]
Category:
Basics and Physics
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| T1&T2 WAIGHTED MEANING ? |
All MRI images have contrast (the bright and the dark) that is based on properties of the tissue that's being imaged. In MRI (unlike, for example, CT) those images are based on a combination of several physical properties. So to some extent ALL MRI images are based partly on property A, property B, etc.
The tissue properties that are referred to include proton density (how many hydrogen nuclei are in a given area), motion, and two other properties that are called T1 and T2. These are properties that can be seen onloy by using the MRI instrument, much as without a microscope one cannot see inside a cell.
A T1 weighted image is one in which the differences between T1 properties of the various tissues are the predominant reason why some parts of the image are bright and others are not as bright.
This is medically useful because, since T1 and T2 are distinct properties, diseased tissue may show up different than normal tissue on either the T1 weighted scan or the T2.
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| | View the whole thread | | |
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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| | View the whole thread | | |
Jacob Newton
Thu. 7 Oct.10,
19:22
[Reply (1 of 2) to:
'How does TE affect DWI acquisition?'
started by: 'danilo Scelfo'
on Wed. 29 Sep.10]
Category:
Sequences and Imaging Parameters
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| How does TE affect DWI acquisition? |
I never tried to shorten only the echo time while keeping all other parameters the same, but I would expect a change in SNR and artifact appearance. I would use parallel imaging methods to get a shortest possible echo time. Parallel imaging provides DWI with shorter echo trains associated with further reduction of the echo and repetition times, which reduces susceptibility effects and also image blurring. Additionally, the shorter echo time may lead to changes in ADC measurement.
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| | View the whole thread | |
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