[Mristudio-users] artifact

[Katja Doerschner]

Yes! It does, and it is also highly gradient direction dependent (in my data it is also the x gradient direction). Thank you very much for this source.
Best,
katja
On Nov 25, 2010, at 5:16 AM, Fred Tam wrote:

> Hello, Katja. Your artifact looks somewhat like the one examined (and
> corrected/avoided) here:
> 
> 	Gallichan D, Scholz J, Bartsch A, Behrens TE, Robson MD, Miller KL
> (2010): Addressing a Systematic Vibration Artifact in diffusion-Weighted
> MRI. Hum Brain Mapp 31:193-202.
> 
> Fred
> 
> 
> On Fri, 2010-10-22 at 10:15 +0300, Katja Doerschner wrote:
>> Hi,
>> 
>> 
>> I am inspecting my DTI data and find that for some gradient directions
>> (almost 10 out of 30) this hole-like artifact 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 despite
>> parallel imaging. 
>> 
>> 
>> My questions are: 1) what causes these artifacts (I have seen them in
>> other scans/patients at different locations - 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
>> 
>> 
>> 
>> 
> 
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