Hi Live!
That is really the same, thanks for this message! Yes I can absolutely
sign what you wrote.
Up to now, we did several TR/TE variations:
Subject E (60kg)
-polystyrene-vacuum-cushion, TR/TE 9000/92 - artifacts
-foam cushion 9000/92 - NO artifacts
-foam cuhion 12000/110 - artifacts
Subject A (62kg)
-foam chushion TR/TE 9000/92 - artefacts
-foam cushion 11000/110 - NO artefacts
Subject M (92kg)
-polystyrene-vacuum-cushion TR/TE 9000/92 - artifacts
-polystyrene-vacuum-cushion TR/TE 12000/140 - NO artifacts
-polystyrene-vacuum-cushion TR/TE 8600/89 - artifacts
-foam cushion 9000/92 NO artefacts
-foam cushion 9000/96 NO artefacts
And I think that you are right, with the highest possible TE and the
foam cushion (I can't actually explain why the vacuum cushion is
worse), there might be the best results.
Does any one have another idea?
Cheers,
Markus
Quoting Live Eikenes <[log in to unmask]>:
> We have the exact same poor-signal-artifact that you are talking about.
> Siemens definetively knows about it, we have been talking about this
> problem for over a year now. Siemens sent some "experts" in june this
> year, but they were not able to solve the problem. They said that they
> had to go home and think about it.......
> On our system (the same as yours), the problem is subject dependent,
> and does not appear at the same place in each subject. And we also
> think that it is the x-direction that is worst (a colleauge just said
> that he had seen it in other directions as well, but is most evident in
> the x-direction). We do seem to avoid the problem by increasing the TE
> with 10-20 ms above the minimal TE allowed by the scanner, but of
> course, we are not happy about that, we loose a lot of signal.
>
> We also thought that it had to do with vibrations, and have called it a
> vibration problem. The Trio is shaking enormously, and we actually
> tried to put heavy sand-bags on top of the head coild, to try to
> stabilize it from the heavy vibrations. It seemed to work for that
> particular patient, but when we tried it later on another patient, it
> did non work.
>
> So for now, my best advice is to increase the TE!
>
> Best regards, Live Eikenes.
>
>
>
>
>
> Markus Gschwind wrote:
>> Hello !
>>
>> Does anyone have experience with the "Siemens Magnetom Trio" 3T MRI
>> and its behavior in
>> DTI sequences?
>>
>> We suffer from a poor-signal-artifact in the mid-parietal area that:
>>
>> - occurs only in the directions of x far from 0 (x=0.75 to 1 and
>> x=-0.75 to -1)
>> in our 30direction sequence this is always the directions 6, 14, 15
>> 22, 28,29,30
>>
>> - occurs in an uncontrollable manner in 75%, dependent on subject,
>> TR/TE and head
>> fixation.
>> That means we havn't found one single reason.
>>
>> See attached example, please
>>
>> Help! Does anyone know that sort of artifact in a Siemens Magnetom Trio?
>> Does anyone know why it is allways and only the x-gradient?
>> Does anyone know what to do against?
>>
>> Thanks a lot in advance!
>> Markus
>>
>>
>>
>> ------------------------------------------------------------------------
>>
--
Dr. med. Markus Gschwind, M.D.
Laboratory for Neurology and Imaging of Cognition
Dept of Neurosciences
University Medical Center (CMU)
1 Michel-Servet - 1211 GENEVA - CH
Tel 0041 (0) 22 379 5324
Fax 0041 (0) 22 379 5402
email: [log in to unmask]
http://labnic.unige.ch
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