> I tried to use slice timing in spm99 for some fMRI data. I expected slice
> timing in spm99b and spm99 to be similar, but they are not! In spm99,
> inputs of TR and TA are required, but NOT in spm99b. The version in
> spm99b is v2.3 and ,in spm99, v2.6.
>
> (An earlier post about TA was found in the archive in Sept 99, but
> generated only one response/follow-up question.)
>
> My questions:
> 1. What is the acquistion time (TA)? Can someone give an example how
> this is determined?
In simple terms, the TA is the time between acquisition of the first
slice
and acquisition of the last slice of one scan, whereas the TR is the
time
between acquisition of the first slice of one scan and the first slice
of
the next scan (ie TA<=TR). In some acquisition sequences, there is an
appreciable gap between successive scans (TA<TR) which needs to be taken
into account in the slice-timing correction.
> 2. I used spm99b's slice timing for many previous sets of data. Were
> those outputs correct even though TR and TA were not prompted for input?
In the old version, TA=TR, so if you had pretty continuous scanning (ie
gaps of O[100] ms), the difference will be negligible.
Rik
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