Yvette and I were reviewing her data this morning and found an interesting artifact in 3 functional runs. During the middle of the run a flash of light appears across 3 or four slices in the coronal view and stretches across the entire field of view. This change in signal intensity is reflected by terrible QA numbers and plots. The intensity change lasts for a few seconds. Has anyone else had this problem? Any ideas for a solution?
I have not seen that problem, but I have recently found that my 3T images become severely degraded after about 30-35 minutes of scanning. The images from runs after this time are blurred and scattered across k-space, especially near visual cortex and lateral temporal areas. Overall the area that resembles a structured brain becomes smaller as the runs progress. Anyone who has conducted experiments with a similar protocol to what I used (1500ms TR, 34 slices) should probably check the quality of their images after 35 minutes of functional scanning to see if they become degraded, too.
We have had a similar problem on at least two of our sessions: ExecInfo.09/20051027_31130 Poker.01/20051026_31118
In our cases, it was on only one of the slices in the middle of brain, lasting for ~10 time points. The error is immediately obvious on the QA and raw images. The raw images immediately before and after the problem appear normal. Again, for us it only affects one slice and for a handful of time points.
3T Artifact
Posted - Oct 28 2005 : 11:18:51 AM
