Hi,
I was wondering if you might be able to help clarify some uncertainty that I've
had with thresholding images in Caret.
I am using thresholded volumetric images from FSL, and mapping them into Caret.
I did see in an old post from the mailing list that this is a common approach,
which was good to see. But there are still a few things that I'm uncertain
about:
-- Is it OK to use the interpolated voxel algorithm with pre-thresholded
images? It seems to me that this could be problematic, since it's averaging
zeros in with the data. But if I use the unthresholded images, I'd have to
apply cluster correction in Caret, rather than having FSL do it...which
introduces other complications.
-- Given that the interpolation yields a number of areas in which the actual z
score in Caret is less than our original z threshold, is it advisable to
re-threshold the image using Caret display options (under Metric Settings) to
eliminate all activations under our original threshold (in this case, z = 2.3)?
That seems to show much less activity on the brain, which could be good or
bad, I guess, but the more important question is whether it's a more or less
faithful rendering of the original volumetric image, which I'm not sure about.
-- Is there some "trick" to setting a volume threshold when you import data to
Caret using the "Map volume to surface" option? I tried enabling the volume
threshold, and entered a number to use as a threshold that was higher than the
original threshold used on the image file. But when it imported the image,
that option didn't seem to do anything at all. Is there something else that I
need to do?
Thanks,
Michael
--
Michael S. Cohen, M.S., C. Phil
Ph.D. Candidate
Department of Psychology
University of California, Los Angeles
Los Angeles, CA 90095
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