You might catch head motion caused by subject irritation due to vibration that way, but eddy's motion estimates are necessarily based on volume-to-volume measurements, so most vibrations will be too fast to detect that way.
See https://onlinelibrary.wiley.com/doi/full/10.1002/hbm.22846 and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3906573/ for a different approach. There's also another paper about doing "auto-actuated" (i.e. bed + diffusion gradient actuated) MRE, but the MRE experts across the hall prefer to use purpose-built actuators.
I wonder if scanning a simple water phantom would show reduced signal in the direction of the vibration if the bed were suitably loaded.
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Robert I. Reid, Ph.D. | Sr. Analyst/Programmer, Information Technology
Aging and Dementia Imaging Research | Opus Center for Advanced Imaging Research
Mayo Clinic | 200 First Street SW | Rochester, MN 55905 | mayoclinic.org
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf Of Jacob Antony Alappatt
Sent: Tuesday, January 15, 2019 3:21 PM
To: [log in to unmask]
Subject: [EXTERNAL] [FSL] Eddy motion parameters - Usage
Our diffusion data was acquired with a bed that had been reportedly vibrating. We want to make sure none of our results are correlated with motion.
After running eddy (from FSL/5.0) we end up with 6 motion (3 rotation & 3 translation) parameters, for each volume of the acquisition. If I want a single number from this acquisition, to be used as a regressor, or for correlations, how would I post-process this file?
It can't be as simple as averaging across all volumes, plus I don't know how to transform the 6 motion parameters into a single representative value, per volume. Any help on this would be great.
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