QSM Artifacts

[Fayez H.]

Dear medi-users, 

I'd like to get your advice on an issue I've had with QSM recon. In the attached image you can see coronal slices of the same subject over 5 timepoints. In the first 3, QSM recon went well, unlike the last two timepoints. There seems to be hyper-intensity regions in the medial temporal cortex, and negative fit values in some regions. Is this an issue with the L1_MEDI parameters, CSF mask, acquisition, or something else? I'd appreciate your input. Thanks!

Fayez

[Alexey Dimov]

Could you please show results of field unwrapping (iFreq) for the timepoints in question?

 

Regards,

Alexey

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[Fayez H.]

Hi Alexey, 

Attached are the snapshots for iFreq (Pixel values go from -1 to 1). For context, we used an evenly spaced 6-echo sequence using Phillips 3T. I used region-growth unwrapping for the above but also tried graph-cut based with no improvement. I used PDF but also tried LBV with similar results. 

Fayez 

[Fayez H.]

Hi, just pinging this again. Thanks!

Fayez