Jason--
'epirecon' was developed here at Wisconsin, so I'll take a stab at
commenting on your questions.
The bandpass asymmetry correction adjusts for bias in the A-to-D sampling
(basically). You will notice reduced ghosting with this applied, and, to
the extent that any ghosting is not half-field-of-view, this would affect
signal distribution in the region of interest (i.e., brain proper).
The adjustment for phase correction isn't going to yield differences that
are necessarily visible. I would refer you to the work of Jezzard and
colleagues for a full treatment of this rather complicated topic.
As you note, there are subtle differences between data processed with and
without these corrections. However, in my opinion, there is no reason not
to apply them; the increase in processing time is trivial.
Best,
Wil
.............................................................................
William Irwin Laboratory for Affective Neuroscience
Department of Psychology lab: 608-262-4443
University of Wisconsin fax: 608-265-2875
1202 West Johnson Street http: psyphz.psych.wisc.edu
Madison, Wisconsin 53706 [log in to unmask]
.............................................................................
On Tue, 29 Aug 2000, Jason Steffener wrote:
> Hello all,
> I know this is not the most appropriate place to ask this
> question, but I dont know where else to ask.
> I am using epirecon to reconstruct GE format Pfiles.
> The options for 'epirecon' use are to use the bcrvs1.dat file for Bandpass
> Assymetry Correction and to use the
> ref.dat file
> for phase correction. My question is what is the result (differences) of
> using or not using these files in the reconstruction? I have done the
> reconstruction and SPM preprocessing and analysis on images
> using and NOT using these "dat" files. I see some differences in the
> final statistics. (Not great differences) I would just like to know the
> source of the differences.
> Thank you for any insight or better direction,
> Jason.
>
>
> Jason R. Steffener, RTSV
> Department of Psychiatry, University Hospital, UMDNJ
> Office: (973) 972-1604
> http://www.umdnj.edu/~steffejr/jason.html
>
>
>
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