MRI spine coil artefact

mrphys · Joined: 12 Sep 2008 Posts: 8

Hi,

I'm getting strange artefacts when using the spine coil. See:

http://s153.photobucket.com/albums/s235/s1020099/?action=view&current=artefact_spine_coil1.jpg

There is a line in the phase encoding direction. In most cases theres a larger hyperintense 'blob/star' also on the line. I have no idea what it is. First I thought it was in the freq-encoding direction so I was checking the room for RF leakage. I also tried scanning in the dark incase there was a faulty light causing problems. Nothing has helped. It seems to get worse when using parallel imaging and a smaller FOV.

This line is located on the slice which is close to the center. (This is centric ordering.)

Any idea's on what this could be and how to solve it?

Thanks.

mrphys · Joined: 12 Sep 2008 Posts: 8

Hi,

Well I'm not getting far here. After reading this:

http://www.revisemri.com/questions/artefacts/zipper_causes

I thought it would be important to determine at what frequency this zipper artefact occurs. Becuause if it's a 0 then it may be RF feedthrough. But when I measure it:

http://s153.photobucket.com/albums/s235/s1020099/?action=view&current=freq_interfere.jpg

The location of the line does depend on the Band Width (Hz/Pixels) but I'm not sure where the f=0 line is. Is it really exactly at the middle? When I assume it's at the middle and calculate the frequncy difference -this itself depends on the BW I use. Confused

Also I don't see any interference line when scanning coronal. Very very strange...

Greetings,
Mrphys