| T O P I C R E V I E W |
| erin.douglas |
Posted - Aug 10 2005 : 09:13:36 AM
On Tuesday evening we ran a subject for ExecInfo.08 on the 4T using spiral in, and there was signal loss in the frontal cortex in every run.
Has anyone else ran into this? Could it be a problem in shimming? Does anyone have ideas? or should we take a break in scanning until things are figured out? |
| 2 L A T E S T R E P L I E S (Newest First) |
| erin.douglas |
Posted - Aug 10 2005 : 09:39:02 AM
Thanks Dr. McCarthy, Our subject did not have any dental work, and the tech did not seem to think it was a shimming problem, but I wondered if perhaps movement by the subject between shimming and functional scans could produce the effect we saw. We looked at the data as it came up after each run, but between the tech, Jeff, and me, we could not come up with a reasonable solution. The data is in Katz\ExecInfo.08\Data\Func\20050809_45159 if you would like to have a look. |
| gregory.mccarthy |
Posted - Aug 10 2005 : 09:28:48 AM
There are a lot of possible reasons for signal loss, and I would have to look at the scans to know. If the loss is in the ventral frontal region, and is especially severe, it could be related to a subject having braces or other dental work. If the brain looks stretched or mishappen, it could be shimming. It is always a good idea to check with the MRI technologist as the data are being acquired - as these problems will be evident in the automatic QA images that show up a few minutes after the conclusion of a run. You should always inspect these, as some problems can be fixed and the session saved. |
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