Hi Paul,
I have also used the good (?) old parameter "motion exceeding voxel
size" but I quite like the idea of using the speed of change as a more
meaningful parameter. I have been using my own script to detect motion
from the parameters for a while and would like to include this option.
Based on your experience, what threshold do you accept in terms of "mm/TR" ?
Thanks,
Marko
Paul Mazaika wrote:
> There are few, if any, quantitative rules for the amount of motion
> allowed in an fMRI study.
>
> The 3 mm motion threshold is related to a rule-of-thumb in the
> community that subjects with maximum motions larger than 2 mm or 3 mm
> should be excluded from a study. However, this rule-of-thumb discards
> too many subjects in pediatric and clinical populations.
>
> In practice now, we usually ignore the maximum motion threshold
> because the large maximum motions are usually from rapid motions, and
> instead we test for rapid motion mm/TR above a threshold. The rapid
> motion scans have distortions, realignment errors, and spin history
> effects, and so they are treated as artifacts. Large slow motions are
> treated fairly well by a different function in the ArtRepair package.
> Consequently, we exclude subjects based on too many scans of rapid
> motion rather than an amount of maximum motion.
>
> Best regards, Paul
>
> ----- Original Message ----- From: "Jen
> Pokorny"<[log in to unmask]> To: [log in to unmask] Sent:
> Wednesday, October 20, 2010 4:03:13 PM Subject: [SPM] ArtRepair
> toolbox
>
> I am currently trying to use the ArtRepair5 toolbox and had a
> question regarding setting the motion threshold (mm/TR). I use a
> cutoff of 3 mm for overall movement. Does this 3 mm correspond to the
> motion threshold mm/TR in the toolbox? Is there a standard guideline
> on the parameters one should use for these thresholds? Thank you for
> any help! -Jen
>
>
>
--
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Marko Wilke (Dr.med./M.D.)
[log in to unmask]
Universitäts-Kinderklinik University Children's Hospital
Abt. III (Neuropädiatrie) Dept. III (Pediatric neurology)
Hoppe-Seyler-Str. 1, D - 72076 Tübingen
Tel.: (+49) 07071 29-83416 Fax: (+49) 07071 29-5473
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