[Mristudio-users] artifact

[susumu mori]

Hi Katja,

It is difficult to say anything without looking at the images. Usually if
you find a localized signal drop, that is due to motion. However, they
appear typically around the 4th ventricle and rarely around the central
sulcus. Also, 10 out of 30 seem too many. Siemens had some issues in the
past with signal drop usually in the occipital lobe.

I thought you can attach a small file with some screenshots?


> My questions are: 1) what causes these artifacts (I have seen them in other
> scans/patients at different locations, e.g. posterior tip of the occipital
> lobe) - could it be the effect of a large blood vessel or other kinds of
> motion)?
>
> I have to see the images.  If you want, you can upload your data to our
ftp site.

2) How can I avoid such artifacts?
>
 > see above.

> 3) Is there any way of 'saving' the data - other than throwing those images
> out
>
> 10 out of 30 seem too many to save. Usually the artifacts are linked to a
particular gradient axis; for example, whenever X axis is applied, the
artifact appears. If so, you lose all X gradient orientations and the data
can't be saved.


> 4) If I have to remove these images - how will that affect the tensor
> calculation/FA maps/fibertracking?
>
> see above

>
> Thank you very much.
> Katja
>
>
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