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FSL Slice Timing Correction
</H1>
User Guide
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<A NAME="section1"></A><HR><H2>INTRODUCTION</H2>
<P>
<code>slicetimer</code> is a pre-processing tool designed to correct for sampling offsets inherent in slice-wise EPI acquisition sequences.
<P>
Each voxel's timecourse is processed independently and intensities are
shifted in time so that they reflect the interpolated value of the
signal at a common reference timepoint for all voxels, providing an
instantaneous `snapshot' of the data, rather than a staggered sample
throughout each volume. Sinc interpolation with a Hanning windowing
kernel is applied to each timecourse to calculate the interpolated
values.
<p> It is necessary to know in what order the slices were acquired and
set the appropriate option. The default correction is appropriate if
slices were acquired from the bottom of the brain.
<p> If slices were acquired from the top of the brain to the bottom
select the
<b>--down</b> option.
<p> If the slices were acquired with interleaved order (0, 2, 4 ... 1,
3, 5 ...) then choose the
<b>--odd</b> option.
<p>If slices were not acquired in regular order you will need to use a
slice order file or a slice timings file. If a slice order file is to
be used, create a text file with a single number on each line, where
the first line states which slice was acquired first, the second line
states which slice was acquired second, etc. The first slice is
numbered 1 not 0.
<p>If a slice timings file is to be used, put one value (ie for each
slice) on each line of a text file. The units are in TRs, with 0.5
corresponding to no shift. Therefore a sensible range of values will
be between 0 and 1.
<pre>
slicetimer -i <timeseries> [-o <corrected_timeseries>] [options]
Compulsory arguments (You MUST set one or more of):
-i,--in filename of input timeseries
Optional arguments (You may optionally specify one or more of):
-o,--out filename of output timeseries
-h,--help display this message
-v,--verbose switch on diagnostic messages
--down reverse slice indexing
-r,--repeat Specify TR of data - default is 3s
-d,--direction direction of slice acquisition (x=1,y=2,z=3) - default is z
--odd use interleaved acquisition
--tcustom filename of single-column custom interleave timing file
--ocustom filename of single-column custom interleave order file (first slice is referred to as 1 not 0)
<p><HR><FONT SIZE=1>Copyright © 2002, University of
Oxford. Written by <A
HREF="http://www.fmrib.ox.ac.uk/~prb/index.html">P. Bannister</A>.</FONT>
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