[Mristudio-users] artifact

[Katja Doerschner]

Hi,
(my initial post got stuck with the moderator because I attached an example image, sorry)--

I am inspecting my DTI data and find that for some gradient directions (almost 10 out of 30) a hole-like artifact (intensity drop out) near central sulcus (very superior) appears. I am attaching an example from a DTI studio screenshot and the b0 image as a reference.
The images were acquired with a 3 Siemens Magnetom, 50 axial slices, slice thickness 3mm, TR 6400ms, TE 88 ms, 4 averages, FOV 128 x 128; Grappa, Accel. Fact 2, 30 gradient directions, Phase Enc Direction A->P, b value 800, the patient was anesthetized.

I also think that there is quite a bit of b0 distortion (around inferior temporal lobes) despite parallel imaging. 

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)?
2) How can I avoid such artifacts?
3) Is there any way of 'saving' the data - other than throwing those images out
4) If I have to remove these images - how will that affect the tensor calculation/FA maps/fibertracking?

Thank you very much.
Katja

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.mristudio.org/pipermail/mristudio-users/attachments/20101025/d98d1115/attachment.html