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tharsh
BIAC Faculty
USA
76 Posts |
 Posted - Dec 12 2005 : 2:09:06 PM
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We have had an intermittent problem on the 3T with one slice seeing a large increase in intensity over the course of 10-15 time points. If you've seen this and haven't told me about it yet, please do.
The purpose of this post, however, is to solicit people's successes/failures in dealing with these artifacts. I can offer suggestions, but since I'm not analyzing the data I never know how the suggestions work out in the end. I'd like to hear how these things turn out, so I can then offer suggestions based on the practical experiences of others, rather than just what I think might work (but is quite likely a horrible thing!).
Thanks!
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Todd Harshbarger
Instructor
BIAC, Duke University
todd.harshbarger@duke.edu
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erin.douglas
BIAC Alum
USA
25 Posts |
Posted - Dec 12 2005 : 3:49:54 PM
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Hi Todd,
ExecInfo.09 and Poker.01 are both experiencing RF problems for scans completed within the last two weeks. As an example, see ExecInfo.09, 31252, Run 3 TR222-234 and Run4 TR0-3, 228-236. Also, ExecInfo.09 31234 has random RF spikes reported in the QA blue box areas, although nothing noticable appears within the raw data (that I can see).
Thanks!
Erin |
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ndennis
Junior Member
27 Posts |
Posted - Dec 12 2005 : 4:03:11 PM
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Our lab also sees these spikes/flashes which last 10-15 time points. As Erin suggested they are first noticed in the QA reports and blue boxes 9and are sometime incorrectly labeled as head motion). When looking at the raw time series data you can further pinpoint the exact slice(s) and timepoints where these missing slices occur.
I think averaging those slices before and after may be a solution (and most likely not including these trials in analysis). But our lab is still working out exactly how to handle this. Suggestions welcome. Also I wonder if whatever solution we come up with should also be used for single flashes (i.e., one isolated missing slice - we see this too).
nancy |
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Dichter
BIAC Faculty
190 Posts |
Posted - Dec 13 2005 : 09:59:52 AM
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Todd -
We have another bright flash from a scan yesterday -- ExecFunc.07 20051212_31255 run 3 timepoints 132-143.
-Gabriel |
Gabriel S. Dichter, PhD
UNC Departments of Psychiatry & Psychology
http://www.can.unc.edu/ |
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Dichter
BIAC Faculty
190 Posts |
Posted - Jan 26 2006 : 09:33:39 AM
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Todd -
We had two bright flashes during a scan yesterday -- ExecFunc.07 20060124_31362 run 3 timepoints 211-223 and run 6 timepoints 92-103.
-Gabriel |
Gabriel S. Dichter, PhD
UNC Departments of Psychiatry & Psychology
http://www.can.unc.edu/ |
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tankersley
BIAC Alum
USA
143 Posts |
Posted - Jan 26 2006 : 12:35:49 PM
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We've had success with Nancy's suggestion to interpolate averages of surrounding data points for the TRs with intense brightness.
This is very simple and fast to do in MATLAB. The more involved part is keeping up with all the time points for subsequent data analysis, since we are excluding the overwitten data.
Dharol |
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Dichter
BIAC Faculty
190 Posts |
Posted - Jul 21 2006 : 12:47:27 PM
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Timepoints 56-67 were bad on run 12 of BAPExec.01 20060720_32076:
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Gabriel S. Dichter, PhD
UNC Departments of Psychiatry & Psychology
http://www.can.unc.edu/ |
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'bright flashes' on the 3T
