Archived FMRI pipeline: Difference between revisions

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====Rigid body Correction====
====Rigid body Correction====
This step estimates, characterises and broadly corrects for the effect of head-motion. It is also the step at which one can exclude subjects with excessive head-motion (e.g. more than a voxel size).  
This step estimates, characterises and broadly corrects for the effect of head-motion. It is also the step at which one can exclude subjects with excessive head-motion (e.g. more than a voxel size).  
===Registration to Standard Space===
====Registration to Standard Space====
This is the 'Normalize' option in SPM. Chose source image, template (EPI), method, image size, voxel size (2x2x2).
This is the 'Normalize' option in SPM. Chose source image, template (EPI), method, image size, voxel size (2x2x2).
===Regressing out head motion, CSF, white matter & physiological signals===
====Regressing out head motion, CSF, white matter & physiological signals====
In SPM, this is done under '1st level analysis' -> 'Data and design' -> 'Multiple regression'.
In SPM, this is done under '1st level analysis' -> 'Data and design' -> 'Multiple regression'.



Revision as of 14:32, 23 April 2012

NOTE: this page needs cleaning up and filling in!

About fMRI data and file types

Raw fMRI data is saved in .dcm (dicom) files. Typically these .dcm files correspond to individual slices, and the resulting 3D image (or a time-series of 3D images) is saved in a .nii (nifti) file. Raw dicom files can be transformed into nifti format using SPM (a MATLAB software package implementing Statistical Parametric Mapping for neuroimaging data) or other software such as MRIcro.

Note that, when handling neuroimaging data, you need to take special care that the orientation of the images is correct.

Standard Preprocessing Steps

In what follows, we describe the broad stages of fMRI preprocessing. Note that SPM saves the data after each intermediate step in newly created files with relevant prefixes.

Slice-timing Correction

This step corrects for the time-delay between the acquisition of different slices. In order to correct for this, the user needs to provide the following information:

Rigid body Correction

This step estimates, characterises and broadly corrects for the effect of head-motion. It is also the step at which one can exclude subjects with excessive head-motion (e.g. more than a voxel size).

Registration to Standard Space

This is the 'Normalize' option in SPM. Chose source image, template (EPI), method, image size, voxel size (2x2x2).

Regressing out head motion, CSF, white matter & physiological signals

In SPM, this is done under '1st level analysis' -> 'Data and design' -> 'Multiple regression'.

Parcellation

Wavelet Decomposition

The question of smoothing

Required before VBM. Important for finding activations regions. Not used when parcellating (for network analysis).

DVARS and the motion problem

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