Hi Oliva,
Those sort of motion plots are something that we see quite commonly in the
HCP data sampled with a TR of 0.72 sec. Based on your plots, I get an
oscillation frequency close to 0.3 Hz (~ 30 cycles in 80 TRs, with TR=1.25
sec). That frequency is consistent with an effect related to respiration,
either real movement of the head synced to respiration, or perhaps related
to small changes in the magnetic field due to the respiration.
cheers,
-MH
--
Michael Harms, Ph.D.
-----------------------------------------------------------
Conte Center for the Neuroscience of Mental Disorders
Washington University School of Medicine
Department of Psychiatry, Box 8134
660 South Euclid Ave.Tel: 314-747-6173
St. Louis, MO 63110Email: [log in to unmask]
On 8/10/15 2:01 PM, "Olivia Stanley" <[log in to unmask]> wrote:
Hello all,
I am new to FSL so I apologize if this is old hat. I am using MCFLIRT on a
multiband EPI dataset with 272 volumes. The data is 2mm isotropic and has
a 1.25s rep time.
I am running mcflirt with default parameters: mcflirt -in <infile> -out
<outfile>
The resulting plots of translations and rotations have a strange
oscillations less then 0.1mm in magnitude that repeat at a rate of ~0.5
Hz. These oscillations are not in all three axis. I have used MCFLIRT
before and not seen them. Does anyone know what they are and/or how to get
rid of them? I have included the plots above.
Thank you for all your help,
Olivia
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